NUREG-1640

Volume 1

RADIOLOGICAL ASSESSMENTS FOR

CLEARANCE OF EQUIPMENT AND MATERIALS

FROM NUCLEAR FACILITIES

Main Report

Manuscript Completed: December 1998

Date Published:

Prepared by

M.A. McKenzie-Carter, M.D. Otis, M.E. Anderson, J.A. Roberts, R.L. Gotchy, R.A. Meck

Science Applications International Corporation

545 Shoup Avenue

Idaho Falls, ID 83402

Prepared for

Division of Regulatory Applications

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington D.C. 20555-0001
intentionally left blank
iii NUREG-1640

$%675$&7

This report documents the technical basis for the Nuclear Regulatory Commission to use in

developing regulatory standards for clearing equipment and materials with residual radioactivity

from nuclear facilities. In addition to equipment reuse, the analysis identifies material flow

models, based on U.S. industry practices, for recycle of steel, copper, aluminum, and concrete. 

Using information from the material flow models, likely potential exposure scenarios were

realistically modeled for the recycle of these materials. Scenarios for copper, aluminum, and

concrete were based on the steel scenarios, but were modified to reflect differences in each

industry, and additional exposure scenarios unique to each material were included. The

modeling includes all significant exposure pathways, and scenarios include handling and

processing, storage, transportation, product use, and disposal. The results of the analyses are

expressed in both mass and surficial units. Using Monte Carlo techniques, distributions of

radionuclide concentrations were estimated in the material flow model, and concentrations at

selected points in the process were used as inputs to the dose assessment model for each

scenario. Probability distributions for dose factors (along with the mean, median, 5th and 95th

percentile values) were estimated for each radionuclide and each scenario. For each material (e.g.

steel), a critical group was identified for each radionuclide, which represents the scenario with

the highest mean dose factor. Appendices containing details of the analysis and tabulations of

results are included.
intentionally left blank
v NUREG-1640

&217(176

VOLUME 1 (Main Report)

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv

Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi

Units Conversion Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii

1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.1 Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.2 Technical Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.3 Results Presented . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

2 SUMMARY AND COMPARISON OF RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1 Dose Factors for Members of Critical Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.2 Comparison of Results with Other Clearance Criteria . . . . . . . . . . . . . . . . . . . . . . 2-8

2.2.1 Comparison with Regulatory Guide 1.86 . . . . . . . . . . . . . . . . . . . . . . . . 2-8

2.2.2 Comparison with the Environmental Protection Agency . . . . . . . . . . . . 2-11

2.2.3 Comparison with the European Commission . . . . . . . . . . . . . . . . . . . . 2-11

2.2.4 Comparison with the International Atomic Energy Agency . . . . . . . . . 2-14

3 EVALUATION OF DIRECT REUSE OF EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.1 Direct Reuse Scenario Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3.2 Exposure Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.2.1 External Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.2.2 Inhalation Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.2.3 Secondary Ingestion Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3.2.4 Total Dose from Equipment Reuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3.3 Discussion of Models and Parameter Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3.3.1 External Pathway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3.3.2 Inhalation Pathway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3.3.3 Secondary Ingestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

3.4 Reuse Scenario Evaluation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

4 EVALUATION OF RECYCLE AND DISPOSAL OF STEEL SCRAP . . . . . . . . . . . . . . . 4-1

4.1 Introduction to Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.1.1 Approach to Scenario Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.1.2 Scenarios for Recycle and Disposal of Cleared Steel Scrap Metal . . . . . 4-4

4.2 Flow of Recycled and Disposed Steel Scrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.2.1 Conceptual Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.2.2 Sources of Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.2.3 Transportation and Processing of Scrap . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.2.3.1 Integrated Steel Mills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.2.3.2 Non-Integrated Steel Mills . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.2.3.3 Output of Refinery Processes . . . . . . . . . . . . . . . . . . . . . . . . . 4-12

4.2.4 Disposition of EAF Baghouse Dust . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14

4.2.5 Product Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
NUREG-1640 vi

4.2.6 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15

4.3 Mass and Elemental Partitioning Factors for Refinery Operations . . . . . . . . . . . . 4-15

4.3.1 Mass Partitioning Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16

4.3.1.1 Metal Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16

4.3.1.2 Baghouse Dust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16

4.3.1.3 Slag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17

4.3.1.4 Basic Oxygen Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18

4.3.2 Elemental Partitioning Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19

4.3.2.1 Basic Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19

4.3.2.2 General Methodology for Determining Elemental 

 Partitioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20

4.3.2.3 Comparison of Partitioning Factors with Published Studies . 4-22

4.4 Mathematical Model for Flow of Recycled Steel Scrap . . . . . . . . . . . . . . . . . . . . 4-23

4.4.1 Scrap Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-23

4.4.2 Refinery Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24

4.4.3 EAF Dust Hazardous Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27

4.5 Radioactivity Concentrations in Steel Refining Co-products . . . . . . . . . . . . . . . . 4-27

4.6 Dose Assessment for Steel Recycle and Disposal . . . . . . . . . . . . . . . . . . . . . . . . 4-27

4.6.1 General Description of Recycle Scenarios . . . . . . . . . . . . . . . . . . . . . . . 4-27

4.6.2 Work Related Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-35

4.6.2.1 Handling Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-35

4.6.2.2 Processing Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-40

4.6.2.3 Storage Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-41

4.6.2.4 Product Use Scenarios—Workers . . . . . . . . . . . . . . . . . . . . . . 4-41

4.6.2.5 Transportation Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-42

4.6.2.6 Disposal Activities Scenarios . . . . . . . . . . . . . . . . . . . . . . . . 4-44

4.6.3 Description of Non-worker Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 4-46

4.6.3.1 Refinery Atmospheric Releases . . . . . . . . . . . . . . . . . . . . . . . 4-46

4.6.3.2 Storage Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-49

4.6.3.3 Product Use Scenarios—Non-workers . . . . . . . . . . . . . . . . . . 4-52

4.6.3.4 Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-56

4.6.3.5 Resident on Closed Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . 4-56

4.6.4 Environmental Media Concentrations Resulting from Environmental

Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-66

4.6.4.1 Atmospheric Releases (Source Term, Dispersion, Media

Concentration) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-66

4.6.4.2 Drinking Water Concentrations . . . . . . . . . . . . . . . . . . . . . . . 4-71

4.6.4.3 Food and Soil Concentrations . . . . . . . . . . . . . . . . . . . . . . . . . 4-77

4.6.5 Exposure Pathway Doses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-80

4.6.5.1 External Exposure Pathway . . . . . . . . . . . . . . . . . . . . . . . . . . 4-80

4.6.5.2 Inhalation Exposure Pathway . . . . . . . . . . . . . . . . . . . . . . . . . 4-83

4.6.5.3 Inadvertent Secondary Ingestion Exposure Pathway . . . . . . . 4-85

4.6.5.4 Water Ingestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-86

4.6.5.5 Ingestion of Food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-86

4.7 Derived Surficial Dose Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-89

4.8 Parameter Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-90
vii NUREG-1640

4.8.1 Radionuclide Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-90

4.8.2 Material Flow Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-92

4.8.3 Scenario Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-92

4.8.4 Dose Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-94

4.8.4.1 Input Radionuclide Concentrations from the Material Flow . 4-94

4.8.4.2 Exposure Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-94

4.8.4.3 Material Densities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-96

4.8.4.4 Mixing of Cleared Material . . . . . . . . . . . . . . . . . . . . . . . . . . 4-97

4.8.4.5 External Exposure Parameters . . . . . . . . . . . . . . . . . . . . . . . . 4-99

4.8.4.6 Inhalation Exposure Parameters . . . . . . . . . . . . . . . . . . . . . . 4-100

4.8.4.7 Inadvertent Secondary Ingestion Exposure Parameters . . . . 4-104

4.8.4.8 Drinking Water Ingestion Exposure Parameters . . . . . . . . . . 4-104

4.8.4.9 Ingestion Exposure Parameters . . . . . . . . . . . . . . . . . . . . . . . 4-106

4.8.4.10 Atmospheric Release Parameters . . . . . . . . . . . . . . . . . . . . 4-107

4.8.4.11 Landfill Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-108

4.8.5 Steel Surface-to-Mass Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-111

4.9 Dose Factors for Recycle of Steel Scrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-111

5 EVALUATION OF RECYCLE AND DISPOSAL OF COPPER SCRAP . . . . . . . . . . . . . . 5-1

5.1 Introduction to Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.2 Flow of Recycled and Disposed Copper Scrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5.2.1 Sources of Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5.2.2 Transportation and Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5.2.3 Copper Mills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5.2.3.1 Reverberatory Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5.2.3.2 Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5.2.3.3 Electrorefiner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5.2.3.4 Output of Refinery Processes . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

5.2.4 Product Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

5.2.5 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

5.3 Mass and Elemental Partitioning Factors for Refinery Operations . . . . . . . . . . . . . 5-7

5.3.1 Mass Partitioning Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

5.3.2 Elemental Partitioning Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

5.4 Mathematical Model for Flow of Recycled Copper Scrap . . . . . . . . . . . . . . . . . . . 5-8

5.4.1 Mixing of Cleared and Other Scrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10

5.4.2 Refinery Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

5.5 Radioactivity Concentrations in Copper Refining Co-products . . . . . . . . . . . . . . 5-13

5.6 Dose Assessment for Unique Copper Recycle and Disposal Scenarios . . . . . . . . 5-20

5.6.1 Exposure Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20

5.6.2 Mathematical Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20

5.7 Parameter Discussion for all Modeled Scenarios . . . . . . . . . . . . . . . . . . . . . . . . 5-21

5.7.1 Scenario Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

5.7.2 Dose Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23

5.7.2.1 Input Concentrations from the Material Flow . . . . . . . . . . . . . 5-23

5.7.2.2 External Exposure Parameters . . . . . . . . . . . . . . . . . . . . . . . . 5-23

5.7.2.3 Ingestion Exposure Parameters . . . . . . . . . . . . . . . . . . . . . . . . 5-23
NUREG-1640 viii

5.7.2.4 Atmospheric Release Parameters . . . . . . . . . . . . . . . . . . . . . . 5-24

5.8 Dose Factors for Recycle and Disposal of Copper Scrap . . . . . . . . . . . . . . . . . . . 5-25

6 EVALUATION OF RECYCLE AND DISPOSAL OF ALUMINUM SCRAP . . . . . . . . . . 6-1

6.1 Introduction to Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2 Flow of Recycled and Disposed Aluminum Scrap . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2.1 Sources of Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

6.2.2 Transportation and Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

6.2.3 Aluminum Mills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

6.2.4 Product Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

6.2.5 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

6.3 Mass and Elemental Partitioning Factors for Refinery Operations . . . . . . . . . . . . . 6-6

6.3.1 Mass Partitioning Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

6.3.2 Elemental Partitioning Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

6.4 Mathematical Model for Flow of Recycled Aluminum Scrap . . . . . . . . . . . . . . . . 6-7

6.4.1 Mixing of Cleared Scrap and Other Scrap . . . . . . . . . . . . . . . . . . . . . . . . 6-7

6.4.2 Refinery Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9

6.5 Radioactivity Concentrations in Aluminum Refining Co-Products . . . . . . . . . . . 6-11

6.6 Dose Assessment for Unique Aluminum Recycle and Disposal Scenarios . . . . . 6-12

6.6.1 Exposure pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

6.6.2 Mathematical Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

6.7 Parameter Discussion for all Modeled Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . 6-16

6.7.1 Scenario Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16

6.7.2 Dose Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16

6.7.2.1 Input Concentrations from the Material Flow . . . . . . . . . . . . . 6-16

6.7.2.2 External Exposure Parameters . . . . . . . . . . . . . . . . . . . . . . . . 6-17

6.7.2.3 Ingestion Exposure Parameters . . . . . . . . . . . . . . . . . . . . . . . . 6-17

6.7.2.4 Atmospheric Release Parameters . . . . . . . . . . . . . . . . . . . . . . 6-18

6.7.3 Aluminum Surface-to-Mass Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-18

6.8 Dose Factors for Recycle and Disposal of Aluminum Scrap . . . . . . . . . . . . . . . . 6-18

7 EVALUATION OF RECYCLE AND DISPOSAL OF CONCRETE . . . . . . . . . . . . . . . . . . 7-1

7.1 Introduction to Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.2 Flow of Recycled and Disposed Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

7.2.1 Source of Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

7.2.2 Transportation and Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

7.2.3 Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

7.2.4 Product Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

7.2.5 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

7.3 Mathematical Model for the Flow of Recycled Concrete Debris . . . . . . . . . . . . . . 7-4

7.4 Radioactivity Concentrations in Concrete Recycle Products . . . . . . . . . . . . . . . . . 7-5

7.5 Dose Assessment for Concrete Recycle and Disposal . . . . . . . . . . . . . . . . . . . . . . 7-6

7.6 Parameter Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

7.6.1 Scenario Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

7.6.2 Dose Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

7.6.2.1 Input Concentrations from the Material Flow . . . . . . . . . . . . . . 7-7
ix NUREG-1640

7.6.2.2 External Exposure Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

7.6.3 Concrete Surface-to-Mass Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

7.7 Dose Factors for Concrete Recycle and Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8

8 QUALITY CONTROL PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.1 Technical Approach to Model Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2

8.2 Quality Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3

8.3 Document Review, Control and Configuration Management . . . . . . . . . . . . . . . . 8-5

8.4 QA Review of Technical Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5

8.5 Recordkeeping: Project Engineering Cabinet . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5

8.6 Instructions for Naming Files and Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7

9 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . glossary-1

Tables

Table 2.1 Mass-based critical-group dose factors for recycle and disposal of 

cleared materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Table 2.2 Surficial critical-group dose factors for recycle and disposal of cleared materials . . 2-6

Table 2.3 Comparison of derived NRC clearance levels with Regulatory Guide 1.86 

acceptable contamination levels (across all materials) . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Table 2.4 Comparison of NRC mass-based steel recycle critical-group dose factors with EPA

values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

Table 2.5 Comparison of derived NRC clearance levels with European Commission 

values (all metals) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

Table 2.6 Comparison of derived NRC clearance levels with IAEA values (all materials) . . 2-18

Table 3.1 Representative reported indoor resuspension data and recommended values . . . . . 3-7

Table 3.2 Dose factors for reuse of a large piece of equipment . . . . . . . . . . . . . . . . . . . . . . . 3-14

Table 4.1 Scenarios discussed in previous studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

Table 4.2 Key assumptions for the steel material flow model . . . . . . . . . . . . . . . . . . . . . . . . 4-11

Table 4.3 Values used for calculation of EAF mass partitioning factors (metric tons 

per charge) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17

Table 4.4 Values used for calculation of BOF mass partition factors (metric tons 

per charge) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19

Table 4.5 Elemental partitioning factors (EPF) for steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22

Table 4.6 Results of material flow model—steel electric arc furnace . . . . . . . . . . . . . . . . . . 4-28

Table 4.7 Results of material flow model—for steel basic oxygen furnace . . . . . . . . . . . . . . 4-31

Table 4.8 Scenario and exposure pathway matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-33

Table 4.9 Radionuclides of interest for recycle, disposal, and reuse of equipment 

and material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-91

Table 4.10 Steel recycle critical-group dose factors—mass . . . . . . . . . . . . . . . . . . . . . . . . . 4-115

Table 4.11 Steel recycle critical-group dose factors—surficial . . . . . . . . . . . . . . . . . . . . . . 4-118

Table 5.1 Elemental partitioning factor ranges (%) for copper refining . . . . . . . . . . . . . . . . . . 5-9

Table 5.2 Results of material flow model—copper reverberatory furnace . . . . . . . . . . . . . . . 5-14

Table 5.3 Results of material flow model—copper converter furnace . . . . . . . . . . . . . . . . . . 5-16
NUREG-1640 x

Table 5.4 Results of material flow model—copper electrorefinery . . . . . . . . . . . . . . . . . . . . 5-18

Table 5.5 Copper recycle critical-group dose factors—mass . . . . . . . . . . . . . . . . . . . . . . . . . 5-27

Table 5.6 Copper recycle critical-group dose factors—surficial . . . . . . . . . . . . . . . . . . . . . . 5-30

Table 6.1 Key modeling assumptions for aluminum secondary smelter . . . . . . . . . . . . . . . . . 6-4

Table 6.2 Elemental partitioning factor ranges (%) for aluminum refining . . . . . . . . . . . . . . . 6-8

Table 6.3 Results of material flow model—aluminum refinery . . . . . . . . . . . . . . . . . . . . . . . 6-13

Table 6.4 Aluminum recycle critical-group dose factors—mass . . . . . . . . . . . . . . . . . . . . . . 6-21

Table 6.5 Aluminum recycle critical-group dose factors—surficial . . . . . . . . . . . . . . . . . . . . 6-24

Table 7.1 Results of concrete material flow model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5

Table 7.2 Concrete recycle critical-group dose factors—mass . . . . . . . . . . . . . . . . . . . . . . . . 7-10

Table 7.3 Concrete recycle critical-group dose factors—surficial . . . . . . . . . . . . . . . . . . . . . 7-13

Figures

Figure 1.1 Relationship of the critical group to other exposed groups . . . . . . . . . . . . . . . . . . . 1-4

Figure 4.1 Flow of steel scrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

Figure 4.2 Generic refining process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

Figure 4.3 Modeling approach for atmospheric releases from a refinery . . . . . . . . . . . . . . . . 4-47

Figure 4.4 Three-box compartment model for the storage of slag scenario . . . . . . . . . . . . . . 4-50

Figure 4.5 Modeling approach for resident on a closed landfill . . . . . . . . . . . . . . . . . . . . . . . 4-58

Figure 4.6 Three-box compartment model for surface-to-groundwater transport for 

resident on closed landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-63

Figure 4.7 Scenarios describing critical groups for steel recycle . . . . . . . . . . . . . . . . . . . . . 4-113

Figure 5.1 Material flow for copper scrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Figure 5.2 Scenarios describing critical groups for copper recycle . . . . . . . . . . . . . . . . . . . . 5-26

Figure 6.1 Material flow for aluminum scrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

Figure 6.2 Scenarios describing critical groups for aluminum recycle . . . . . . . . . . . . . . . . . . 6-20

Figure 7.1 Conceptual model for the overall flow of recycled and disposed concrete . . . . . . . 7-2

Figure 7.2 Scenarios describing critical groups for concrete recycle . . . . . . . . . . . . . . . . . . . . 7-9

VOLUME 2 (Appendices)

APPENDIX A Exposure Scenario Titles and Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . A-1

APPENDIX B Parameter Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

APPENDIX C External Exposure Dose Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

APPENDIX D Mixing of Cleared Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1

APPENDIX E Radioactive Decay and Progeny Ingrowth . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-1

APPENDIX F Dose Factors for Steel Recycle Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-1

APPENDIX G Dose Factors for Copper Recycle Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . G-1

APPENDIX H Dose Factors for Aluminum Recycle Scenarios . . . . . . . . . . . . . . . . . . . . . . . H-1

APPENDIX I Dose Factors for Concrete Recycle Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . I-1

APPENDIX J Additional Considerations for Protection of the Public . . . . . . . . . . . . . . . . . . J-1
xi NUREG-1640

(;(&87,9(6800$5<

This report provides the technical basis for the Nuclear Regulatory Commission (NRC) to base

regulatory standards for clearance of equipment and materials with residual radioactivity from

regulatory control. The goal of the analyses is to identify realistic critical groups resulting from

clearance of equipment and materials from NRC licensed facilities and to calculate dose factors

for the average member of each critical group. The methods described in this report address both

surficially contaminated equipment and volumetrically contaminated scrap materials.

In order to ensure that the reuse and recycle assessments are defensible, accurate, and verifiable,

a Quality Control Plan (QCP) was prepared for and followed during this evaluation. The QCP

specifies procedures and conventions for developing the reuse and recycle models, defining

equations and definitions, and implementing spreadsheets. Also included in the QCP are

requirements for preparing and reviewing calculations and recording and documenting technical

information. The QCP provides a documented system for ensuring accurate results, as well as a

method for tracing the bases of assumptions. The QCP incorporates quality assurance guidelines

provided by the NRC and other recognized authoritative references. 

Dose factors for both surficial and volumetric residual radioactivity were calculated in this

analysis. The dose factors, as well as derived clearance levels, are compared to values from other

documented sources. The dose factors used for deriving clearance levels for each radionuclide

are the critical-group dose factors (the mean value of the distribution calculated from the model

for each critical group). These dose factors represent the total effective dose equivalent (TEDE)

for an average individual in the critical group for each radionuclide. The dose factors are

normalized and are expressed in units of annual dose per unit of residual radioactivity. The

recycle clearance levels for each radionuclide are based on the highest critical-group dose factors

across the materials that are appropriate for comparison (steel, copper, aluminum, and concrete). 

The recycle scenario critical group is not the same for each radionuclide, due to the complex

nature of the recycle analyses (e.g., differential behavior during melting, wide range of scenario

categories, and different types of scrap material). The majority of clearance levels are based on

critical groups that involve either commercial truck drivers or workers at processing facilities. 

With only two exceptions, the recycle (volumetric) critical-group dose factors are more

restrictive than the equipment reuse (surficial) clearance levels, primarily because of the much

smaller amount of radioactivity involved in the equipment reuse scenario analyses. 

The wide range of radionuclide-specific clearance levels derived from the dose factors in this

report compare inconsistently with those contained in Regulatory Guide 1.86. Using a clearance

criterion of 10 μSv/y, approximately half of the derived radionuclide-specific clearance levels in

this report are within a factor of 10 of the acceptable surface contamination levels in Regulatory

Guide 1.86. Most of the remaining are greater than a factor of 10 higher than the Regulatory

Guide values, indicating that the derived clearance levels in this report are less restrictive than

Regulatory Guide 1.86. 
NUREG-1640 xii

Critical group dose factors from this analysis are similar to the draft dose factors published by the

EPA. For 36 of the 40 radionuclides in common, the dose factors are within a factor of 10,

indicating that the two sets of dose factors are in general agreement. Derived clearance levels do

not compare as well to clearance levels from international sources. Using a common clearance

criterion of 10 μSv/y, between 50% and 75% of the derived clearance levels for radionuclides in

common are within a factor of 10 of the clearance levels published by the European Commission

and International Atomic Energy Agency. For those derived clearance levels that are greater

than a factor of 10 different in these two sources, the derived clearance levels in this report are

more restrictive for all but one radionuclide in each comparison.

Reuse of equipment and recycle of materials were both evaluated and are described in this report. 

Equipment reuse scenarios differ from recycle scenarios in three ways: (1) only surficial

contamination is modeled, (2) the cleared equipment is not processed, and (3) different material

types are not considered. A generic equipment reuse scenario was selected for detailed

evaluation based on a qualitative screening evaluation of potential equipment reuse exposure

scenarios. Modeling the reuse of a large piece of contaminated equipment resulted in dose

factors for each radionuclide that bound all other equipment reuse scenarios considered. Thus, it

was not necessary to model other equipment reuse scenarios. Exposure pathways included in the

dose evaluation are external, inhalation, and secondary ingestion. The mathematical equations

and parameter values used to evaluate the scenario are presented, as well as a discussion of key

parameter values. The exposure pathways analyzed produce reasonable estimates of the potential

TEDE that a member of the critical group could receive. 

Recycled material was evaluated using material flow models and dose assessment models. Both

models are based on probabilistic methods. Input parameters are modeled as distributions

instead of point values (because of uncertainty in the values) resulting in distributions for the

output values (i.e., radionuclide concentrations and dose factors).

The material flow model is material-specific and describes the flow of cleared material beginning

with the refining process (for metals) or the processing steps (for concrete) through the

generation of consumer products. In the material flow model, the original concentration of

radionuclides in the cleared material is redistributed to all the products of the process, such as

baghouse dust and off-gas, as well as consumer products. The radionuclide concentrations

calculated from the material flow model are used as input to the models that estimates potential

dose factors for the various scenarios.

The material flow models were also used to identify all the reasonably possible exposure

scenarios within the context of the current recycle industries. Approximately 50 potential

scenarios were screened and consolidated to form set of 31 exposure scenarios (generic and

specific) that were analyzed for the recycle of cleared steel. The scenarios comprise five general

categories of potential exposure: handling and processing, storage, transportation, product use,

and disposal. Within these categories, five source materials were examined: scrap metal,

refinery slag, baghouse dust, refined metal, and atmospheric emissions from refineries. 
xiii NUREG-1640

Radionuclide-specific dose factors were calculated for all scenarios using the dose assessment

models. 

Exposure scenarios developed for clearance of steel served as the basis for the evaluation of three

other materials (copper, aluminum, and concrete). Scenarios unique to each of the other

materials were also analyzed. These unique scenarios involve the use of refined copper in

household plumbing, use of refined aluminum in cookware, and a resident on the site of a closed

landfill containing recycled concrete. Twenty-three scenarios were analyzed for copper recycle

and 17 for aluminum recycle. Because of the lack of refining coproducts, there are fewer

potential scenarios for concrete recycle (7 scenarios). Using the same methodology used for the

steel evaluation, radionuclide-specific dose factors were calculated for all scenarios for these

three additional materials. 

The analyses were conducted using Monte Carlo techniques to develop probability distributions

of the radionuclide concentrations given by the material flow model and of the scenario dose

factors. Specific values tabulated from the output distributions consist of the mean dose factors

for each exposed group, the median of each distribution, and upper (95th percentile) and lower

(5th percentile) values from the distributions. The upper and lower values represent the range of a

90% confidence interval for each radionuclide-specific dose factor. The ratio between the upper

and lower bounds of the confidence interval indicates the width of the distribution and is a

measure of the uncertainty associated with each dose factor. 

Calculated dose factors for an average member of the critical group in the reuse scenario are

based on a unit level of residual surficial contamination and are expressed in normalized units of

μSv/y per Bq/cm2 (mrem/y per pCi/cm2). Dose factors range from a high of 170 μSv/y per

Bq/cm2 (0.6 mrem/y per pCi/cm2) for Th-229 to a low of 1E-05 μSv/y per Bq/cm2. Most of the

eighty-five radionuclide-specific dose factors (approximately two-thirds) are less than 10 μSv/y

per Bq/cm2 (0.04 mrem/y per pCi/cm2). The size of the confidence intervals (i.e., the range from

the 5th percentile value to the 95th percentile value) for dose factors in the equipment reuse

scenario fall into two groups. For about half the nuclides, the confidence interval ratio is close to

5 (ratio of 95th percentile to 5th percentile values). The remaining nuclides have confidence

interval ratios that range from about 10 to about 40. The unique radiological characteristics of

each group are responsible for the wide range of ratios. Calculated dose factors that are

dominated by inhalation and ingestion exposure pathways have wider confidence intervals

(greater uncertainty) than dose factors dominated by the external exposure pathway.

Dose factors for the steel recycle analysis range from a high of 2,000 μSv/y per Bq/g (7 mrem/y

per pCi/g) for Np-237 to a low of 4E-04 μSv/y per Bq/g. The derived surficial mean critical

group dose factors for steel recycle range from 1,400 μSv/y per Bq/cm2

 (Np-237) to a low of

3E-04 μSv/y per Bq/cm2. The Np-237 dose factor results from the drinking water exposure

pathway in a refinery slag storage scenario. Only 6 of the 85 radionuclide-specific dose factors

are greater than 270 μSv/y per Bq/g (1 mrem/y per pCi/g). Occupational doses associated with

transportation and refinery facilities most commonly produce the critical groups for steel recycle.
NUREG-1640 xiv

Results for recycle of copper and aluminum generally yield similar—although lower—dose

factors. Copper recycle dose factors range from a high of 300 μSv/y per Bq/g (1 mrem/y per

pCi/g) for Th-229 to a low of 4E-04 μSv/y per Bq/g. The derived surficial mean critical group

dose factors for copper recycle are numerically the same, range from 300 μSv/y per Bq/cm2

(Th-229) to a low of 4E-04 μSv/y per Bq/cm2. Aluminum recycle dose factors range from a high

of 6 μSv/y per Bq/g (.02 mrem/y per pCi/g) for Ag-110m to a low of 2E-06 μSv/y per Bq/g. The

derived surficial mean critical group dose factors for aluminum recycle range from 23 μSv/y per

Bq/cm2

 (Ag-110m) to a low of 7E-06 μSv/y per Bq/cm2. As in the steel evaluation, most of the

85 radionuclide-specific dose factors for both copper and aluminum are less than 270 μSv/y per

Bq/g (1 mrem/y per pCi/g). Also similar to the steel evaluation, occupational doses associated

with transportation and refinery facilities most commonly result in critical groups for copper and

aluminum. One copper product-use scenario results in a critical group for copper recycle (use of

a generic small copper object), and use of aluminum products accounts for several critical groups

in the aluminum recycle analysis.

The mass-based concrete recycle dose factors are generally higher than those calculated for

metals recycle, ranging from a high of 7E+04 μSv/y per Bq/g (300 mrem/y per pCi/g) for Np-237

to a low of 3E-03 μSv/y per Bq/g. The derived surficial mean critical group dose factors for

concrete recycle range from 1,400 μSv/y per Bq/cm2 (Np-237) to a low of 5E-05 μSv/y per

Bq/cm2. Approximately 90% of the 85 radionuclide-specific dose factors are less than 270 μSv/y

per Bq/g (1 mrem/y per pCi/g). Unlike the metals, a scenario involving a resident on a closed

landfill was analyzed and included in the critical group determination. This scenario accounts for

one-third of the critical groups for concrete recycle. 

Examining the distributions associated with the calculated dose factors for each recycle exposure

scenario provides some additional information. Simple scenarios, with only a few exposure

pathways and relatively well-known parameters, have distributions that are fairly narrow. For

example, the dose factors associated with the commercial truck driver scenarios have confidence

interval ratios that range from 2 to about 15 (ratio of 95th percentile to 5th percentile values). 

Confidence intervals are much wider for complex scenarios with many parameters and uncertain

pathways of exposure, such as food-chain intake, groundwater transport, and atmospheric

dispersion. The scenarios describing residents on closed landfills containing concrete debris and

individuals near large slag storage piles exhibit the greatest range. The confidence interval ratios

for these scenarios range from about 150 to about 650. 

Appendices included as Volume 2 of this report provide details of the extensive calculations used

in this evaluation of reuse and recycle. Radionuclide-specific data such as dose conversion

factors and environmental transport factors are included, as well as parameter values for all

materials and scenarios.
xv NUREG-1640

Acknowledgments

The authors could not have successfully completed this analysis without the assistance and

support of many individuals. The SAIC technical support team included several key members,

including Bill House, Kirt Marlow, and Morris Hall. They provided broad support in several

areas, including parameter development, spreadsheet revisions, and quality assurance reviews. In

addition, Howard Pippen contributed to several technical issues in the early stages of the project;

Gary Leatherman was instrumental in developing the material flow models; and George Santee

provided critical support with several technical issues, including writing the spreadsheet macros. 

The analysis also benefitted from outside reviewers and collaborators. Owen Hoffman and

Kathleen Thiessen of SENES Oak Ridge provided outstanding review comments, as well as

technical advice and guidance during the conduct of the analysis. Our collaborations with Sandy

Cohen and Associates, particularly Bob Anigstein and John Mauro, were also very worthwhile

and helpful to the successful completion of the analysis. Finally, the comments from the NRC

Clearance Rulemaking Working Group and the NRC Clearance Rulemaking Steering Group

provided valuable insights, observations, and recommendations. 

The help of many individuals from the secondary metals industries, recycling facilities, and trade

groups also needs to be acknowledged. The information gathered from conversations and visits

with these individuals provided essential details needed for the development and refinement of

the models used in the analysis.

No analysis is complete without the documentation, and this analysis is no exception. Lisa

Marko was essential in this regard, as she played a critical role keeping the internal

documentation in order during conduct of the analysis, and also provided tremendous support in

the final stages of assembling this document. Carolyn Einerson of TechWrite provided crucial

technical editing support on a very tight schedule. Also, Martha Reisenauer and Linda Hellewell

were extremely helpful in the final stages of preparing this document, and Rayleona Sanders of

the NRC Publications Branch provided timely and useful advice.
NUREG-1640 xvi

ABBREVIATIONS

AEC Atomic Energy Commission

AIHC American Industrial Health Council

AISE Association of Iron and Steel Engineers

AISI American Iron and Steel Institute

ALARA as low as is reasonably achievable

BOF basic oxygen furnace

BWR boiling water reactor

CRC Chemical Rubber Company

D&D decontamination and decommissioning

DCF dose conversion factor

DF dilution factor

DOD Department of Defense

DOE Department of Energy

DWL derived working limits

EAF electric arc furnace

EC European Commission

EDE effective dose equivalent

EDF engineering design file

EPA Environmental Protection Agency

EPF elemental partitioning factor

EPRI Electric Power Research Institute

EPS east pile slag

FGR Federal Guidance Report

GF geometry factor

IAEA International Atomic Energy Agency

ICRP International Commission on Radiological Protection

LANL Los Alamos National Laboratory

LLW low-level radioactive waste

MCNP Monte Carlo N-Particle

MPC maximum permissible concentration

MPF mass partitioning factor

NCRP National Council on Radiation Protection and Measurements

NIOSH National Institute of Safety and Health

NRC Nuclear Regulatory Commission

OSHA Occupational Safety and Health Administration

PWR pressurized water reactor

QA Quality Assurance

QCP Quality Control Plan

RCRA Resource Conservation and Recovery Act

SAIC Science Applications International Corporation

SC&A Sandy Cohen and Associates

TDS total dissolved solids

TEDE total effective dose equivalent

TSD Technical Support Document

USBM United States Bureau of Mines
xvii NUREG-1640

Units Conversion Table

This analysis was conducted using conventional units [e.g., radioactivity units of curies (Ci),

dose in units of rem]. In the interest of promoting the use of internationally accepted units, the

results of the analysis have been converted to S.I. units [e.g., radioactivity units of becquerel

(Bq), dose in units of sievert (Sv)]. Units in the text discussion are primary in units of S.I. units,

followed by conventional units in parentheses. Because the analysis was conducted using

conventional units, parameter units listed with equations are maintained in conventional units.

The following table gives conversion factors that can be used to convert from conventional units

to S. I. units.

To Convert From To Multiply by

degrees Fahrenheit (EF) degrees Celsius (EC) subtract 32 EF, then

multiply by 0.556

short ton (ton) kilogram (kg) 907.2

short ton (ton) metric ton (t) 0.9072

pounds per ton (lbs/ton) kilogram per metric ton (kg/t) 0.5

cubic yard (yd3) cubic meter (m3) 0.7646

cubic foot (ft3) cubic meter (m3) 0.02832

curie (Ci) Becquerel (Bq) 3.7E+10

picocurie (pCi) Becquerel (Bq) 0.037

picocurie per square centimeter

(pCi/cm2

)

Bequerel per square centimeter

(Bq/cm2)

0.037

picocurie per gram (pCi/g) Bequerel per gram (Bq/g) 0.037

picocurie per gram of product per

picocurie per gram of scrap 

(pCi/g product per pCi/g scrap)

Bequerel per gram of product per 

Bequerel per gram of scrap 

(Bq/g product per Bq/g scrap)

1.0

millirem per year (mrem/y) microseivert per year (μSv/y) 10

millirem per year per picocurie per

gram (mrem/y per pCi/g)

microseivert per year per becquerel

per gram (μSv/y per Bq/g)

270.27

millirem per year per picocurie per

square centimeter 

(mrem/y per pCi/cm2)

microseivert per year per becquerel

per square centimeter 

(μSv/y per Bq/cm2)

270.27

mrem per year per disintegration per

minute per 100 square centimeters 

(mrem/y per dpm/100 cm2)

microseivert per year per becquerel

per square centimeter 

(μSv/y per Bq/cm2)

60,000
NUREG-1640 xviii
Section 1 Introduction

1-1 NUREG-1640

This report documents the technical basis for establishing a potential U.S. Nuclear Regulatory

Commission (NRC) rulemaking that addresses clearance of equipment and materials from nuclear

facilities. The report contains descriptions of the analyses used to estimate the potential doses

resulting from reuse of equipment and recycle of steel, copper, aluminum, and concrete material

following clearance. The analyses were conducted to calculate realistic dose factors for the average

member of a critical group for each radionuclide. The analyses were conducted on a probabilistic

basis, using parameter value distributions as input, to determine distributions for specific model

results (i.e., concentrations and dose factors). The mean value from a dose factor output distribution

represents the average dose to the exposed population, while the highest mean dose factor across all

exposure scenarios designates the critical group for each radionuclide. In addition to the mean

values, the 5th , 50th , and 95th percentiles from the distributions are presented and discussed in

subsequent sections of the report.

,1752'8&7,21

The U.S. Nuclear Regulatory Commission (NRC) is considering the possibility of revising the

criteria for the clearance of material and equipment from nuclear facilities. NRC licensed

facilities are currently allowed to release materials and equipment during normal facility

operations. These releases are conducted consistent with the acceptable surface contamination

levels contained in Regulatory Guide 1.86 and site-specific technical specifications and license

conditions. The current regulatory framework suffers from issues of consistency with current

risk-based regulatory dose standards and lack of general applicability to a wide range of

volumetrically contaminated equipment and material. Over the next few decades, large-scale

decontamination and decommissioning (D&D) of NRC-licensed nuclear reactors and other

facilities is expected to generate large quantities of potentially reusable equipment and recyclable

material. The NRC has identified the need for a consistent and health protective regulatory basis

to regulate the clearance of such material from regulatory control (NRC 1994a).

Clearance (unrestricted release from regulatory control) implies that there would be no

restrictions on the fate of such equipment and materials based on radiological considerations. 

The many possible dispositions of material cleared from regulatory control can be grouped into

the following three most likely categories: usable equipment could be reused directly after

clearance (direct reuse); material could be immediately disposed in a landfill (direct disposal)

and scrap material could be sold to a scrapyard for recycle (recycle). The potential radiological

impacts associated with clearance of equipment and material from regulatory control with respect

to each of these categories have been assessed and are presented in this document. 

3XUSRVHDQG6FRSH

This report documents analyses of potential radiation doses to members of the public from

materials and equipment released by NRC licensed facilities. The analyses are designed to

address two principal limitations of current regulatory standards: the lack of risk-based clearance

levels and the lack of consistent guidelines for clearing material containing volumetrically

distributed radioactivity. The results presented here are intended to support development of
Introduction Section 1 

NUREG-1640 1-2

generic clearance levels that are applicable to all NRC licensed facilities. The methodology

developed for these analyses can be applied to case-by-case clearance decisions.

Clearance of iron/steel, aluminum, copper, and concrete is addressed in this report. These

materials are the most likely to become available for clearance into the public sector and also

represent the greatest volume of available material.

The results of these analyses are expressed as radionuclide-specific dose factors that relate the

magnitude of radiation dose to the concentration of radioactivity in or on materials or equipment

at the time of clearance. The dose factors provide estimates of the radiation dose received by an

individual over 1 year for a given initial concentration of radioactivity and a specified set of

circumstances that make up a hypothetical exposure scenario. The scenarios have been

constructed to be as realistic as the quality of the underlying data allow. That is, rather than

constructing each scenario as a conservative “worst case,” the level of conservative bias has been

limited to that required for generic application to the situations described in each scenario. 

A wide range of exposure scenarios was evaluated to ensure that these dose factors are

representative of likely dispositions of cleared material and equipment. The scenarios comprise a

range of reasonably expected reuse, disposal, and recycle activities—from handling cleared scrap

through activities during melting and processing, using refined metal products, to disposing

materials in a sanitary or hazardous waste landfill. Impacts associated with residential use of a

closed landfill are also assessed. 

7HFKQLFDO$SSURDFK

The implications of clearing materials and equipment from licensed nuclear facilities to the

public sector presents a complex assessment problem. Clearance from regulatory control implies

that many possible groups in the general public could come in contact with these materials and

equipment under a wide variety of circumstances. The approach taken in this report is designed

to 1) identify a clear assessment endpoint to serve as a basis for clearance criteria that assures

adequate protection of the public and 2) provide a comprehensive evaluation of the realistic

situations that could result in exposure to groups of individuals in the general public.

The design objective for this analysis is to calculate a realistic estimate of the dose factor for the

average member of the critical group for each radionuclide. The critical group is defined in

10CFR20.1003 as “the group of individuals reasonably expected to receive the greatest exposure

to residual radioactivity for any applicable set of circumstances.” For each material evaluated in

this analysis, nuclide-specific dose factors are provided for both volumetrically (Bq/g or pCi/g)

and surficially (Bq/cm2 or pCi/cm2) distributed radioactivity. The dose factors are annual

individual doses that are normalized to the concentration of radioactivity in cleared material

(μSv/y per Bq/g or mrem/y per pCi/g, and μSv/y per Bq/cm2

 or mrem/y per pCi/cm2 ).

In order to assure adequate assessment of potential public doses, a wide range of possible

scenarios were evaluated to identify the critical group for each radionuclide. The scenarios are
Section 1 Introduction

1-3 NUREG-1640

based on the flow of radioactivity associated with released material from the point of clearance to

ultimate disposition and include likely industrial refining processes and use or disposal of

refinery byproducts. This approach provides a basis for clearance criteria that bounds situations

and behaviors that can be reasonably expected and avoids unnecessary conservative results.

Each exposure scenario was analyzed probabilistically using a unit activity concentration

(1 pCi/g) for each radionuclide. Each exposure scenario analysis resulted in a distribution of

dose factor estimates for each radionuclide. This was accomplished for a set of scenarios for

each material analyzed (steel, copper, aluminum, and concrete) using material-specific

assumptions. 

The mean (average) dose factors from the dose factor distribution in each scenario were ranked

to obtain the highest mean dose factor for each radionuclide within each set of material-specific

scenarios. The exposed group described in the exposure scenario yielding the highest mean dose

factor for each radionuclide was designated as the critical group for that radionuclide. The

distribution of dose factors for each critical group is referred to as the critical-group dose factor

distribution. Because the mean dose factors are representative of the average members of each

critical group, the mean critical-group dose factor is sometimes simply referred to as the criticalgroup dose factor. In this analysis, there are four critical-group dose factors for each

radionuclide—one for each material: steel, copper, aluminum, and concrete.

Figure 1.1 illustrates the relationship between dose factors for a range of exposed groups within

the general public and the critical group. This figure displays hypothetical dose factor

distributions (not based on calculated results) for a single radionuclide in various scenarios. 

Many members of the general public will not be in any exposed group, will not receive any dose,

and will have dose factors of zero. The dose factors for each exposed group are comprised of a

frequency distribution because of uncertainty in the estimated dose factor. The average member

of the critical group is represented by the mean (average) value of the critical group frequency

distribution, where the critical group is the exposed group with the highest average dose factor

for each radionuclide.

As indicated in Figure 1.1, there are some hypothetical situations or behaviors that could result in

dose factors higher than those of the average member of the critical population group. Dose

factors higher than those of the critical group represent situations or behaviors that are not

reasonably expected to occur. These situations are not considered in the analyses.

The process of estimating dose factors begins with the development of a set of exposure

scenarios for reuse of equipment and recycle of steel, aluminum, copper, and concrete. The

intent is to be comprehensive enough to include the situations and behaviors that might

reasonably be expected to bring members of the public into contact with cleared material or

equipment. Each scenario represents an exposed group with a potential for being designated the

critical group. The individual scenarios are described in subsequent chapters for each material

evaluated.
Introduction Section 1 

NUREG-1640 1-4

Figure 1.1 Relationship of the critical group to other exposed groups

A key input parameter for each exposure scenario is the concentration of radioactivity in or on

the material that individuals may be exposed to. In the case of direct reuse of equipment, no

processing takes place between clearance and the start of the exposure scenario. For recycle

scenarios, however, a complex series of industrial processes can occur. Recycle of metal

involves transportation to a scrap yard, cutting and sizing of scrap, transportation to a refinery,

the refinery process itself, and subsequent use of the refined metal product. This process

produces byproducts such as slag and baghouse dust, which may also contain residual

radioactivity. Steel, copper, aluminum, and concrete each undergo a different set of industrial

processes during recycle. These processing steps are addressed by a set of models, called

material flow models, that calculate the concentration of residual radioactivity in each material

and its byproducts at each step. These concentration estimates are input parameters to scenario

models. The material flow models are described in subsequent chapters for each material

evaluated.

Both the material flow models and the exposure scenario models are probabilistic. Both the

input parameters and the results calculated by the models are represented by frequency

distributions rather than point estimates. This approach follows the general guidance presented
Section 1 Introduction

1-5 NUREG-1640

in the Environmental Protection Agency’s (EPA) Guiding Principles for Monte Carlo Analysis

(EPA 1997b), NCRP Commentary Number 14 (NCRP 1996), and IAEA Safety Series Number

100 (IAEA 1989). These references contain recent guidance on the conduct of probabilistic

analyses. They also provide a consistent set of technical terms for describing the various features

of the analysis and its results. 

All assessments based on model calculations are inherently uncertain. This uncertainty arises

from several factors, including 1) our ability to adequately model the physical processes

involved, 2) the degree to which exposure scenarios adequately represent individuals in the

desired critical population groups, 3) the level of knowledge available to estimate appropriate

values for parameters in the model, and 4) the natural variability in various quantities used to

estimate parameter values.

Lack of knowledge about an input parameter typically contributes more to the uncertainty of the

parameter value than does the natural variability of that parameter. Even in cases where the

natural variability may be significant, quantifying the amount of uncertainty is difficult. This

analysis does not attempt to quantify the relative contributions of natural variability and

knowledge uncertainty in estimating parameter values. 

The analysis presented here does not address uncertainty due to model structure. This has been

the subject of other aspects of this dose assessment including external and internal technical

reviews and benchmarking selected scenarios against alternative models proposed by other

assessors (e.g., EPA 1997a).

The analysis uses Monte Carlo techniques to conduct a probabilistic analysis of the material flow

and exposure scenario models. Monte Carlo methods produce a single model result (output)

from a set of randomly selected parameter values (inputs). The distribution resulting from

numerous iterations of this process are then statistically summarized and characterized. The

required number of iterations depends on the complexity of the model and the statistical

quantities to be used. For both the material flow model and the scenario spreadsheets 500

iterations were sufficient to produce stable estimates of the mean and the 5th, 50th, and 95th

percentiles of the output distribution. This analysis was conducted using models implemented on

Excel spreadsheets (Microsoft 1997). Monte Carlo analysis of these spreadsheets was conducted

using Crystal Ball® (Decisioneering 1996) software. Parameter values were sampled using a

Latin Hypercube sampling scheme.

Key to the conduct of a probabilistic analysis is the development of frequency distributions for

individual parameters in the model. In this analysis all parameters in both the material flow

model and the exposure scenarios were characterized as either fixed constants or uncertain

parameters with associated frequency distributions. Fixed constants are of three types: physical

constants, such as radioactive decay rates; parameters fundamental to the definition of the

individual addressed by the scenario; and parameters fundamental to the definition of the

scenario itself.
Introduction Section 1 

NUREG-1640 1-6

The dose assessment addresses individuals representing members of the exposed groups. Some

fundamental characteristics of these individuals are considered constants in the model and are not

subject to variability or uncertainty. Examples of constants include the biological response to

radiation or the dose equivalent due to radionuclide intake. Also, certain parameters within each

scenario are considered constants because they are fundamental to the definition of the scenario. 

That is, because they are assumed for purposes of constructing the scenario, they are not subject

to either natural variability or lack of knowledge. Examples include the placement of residences

relative to the refinery stack or the location of a drinking-water well relative to a slag storage

pile.

For the remaining parameters, frequency distributions have been developed that are appropriate

to each scenario and reflect expert judgment regarding the degree to which each parameter is

unknown. When available, data reflecting the measured variation of parameters was used in

estimating parameter distributions. However, for many parameters, the only available data are

not completely representative of the population being assessed. In the absence of acceptable

representative data, subjective characterizations of parameter ranges and distributions have been

developed based on physical plausibility arguments, the behavior of analogous parameters in

other assessments, and expert judgment. The resulting frequency distributions are necessarily

subjective and should not be considered to represent only natural variability. Conventions for the

assignment of parameter distributions based on the quality of available data are presented in

Appendix B.

In some cases, it is appropriate to combine the variability and uncertainty associated with more

than one parameter into a single distribution which can be treated as a lumped parameter. Some

complex pathways contain many nuclide-dependent parameters for which data on uncertainty are

sparse. To avoid making the analysis overly complex and costly, the uncertainty in these

pathways was estimated by choosing key parameters to represent the uncertainty in the entire

pathway. For example, in scenarios containing a groundwater pathway, distributions on the

absorption coefficient, Kd, contributed most to the total pathway uncertainty. Similarly, for the

atmospheric release scenario, the uncertainty in the atmospheric dispersion model was

precalculated and assigned to the average /Q parameter. 

Uncertain parameters included in this analysis are assumed to vary independently; that is,

covariance among parameters has not been incorporated into the modeling. The potential for

strong covariances was evaluated during the parameter characterization process. No strong

covariances were identified among the parameters explicitly treated in the analysis. In general,

the effect of neglecting covariances is to estimate slightly wider confidence intervals on dose

factors.

5HVXOWV3UHVHQWHG

Results from the material flow models are included in the section for each material. These

results consist of values from the calculated distribution of radioactivity concentrations in each

medium of interest (material and industrial byproduct) normalized to unit concentration at the
Section 1 Introduction

1-7 NUREG-1640

time of clearance (Bq/g or pCi/g). The mean, median, and 90% confidence interval (5th and 95th

percentiles) are presented.

The primary results from this analysis are radionuclide-specific dose factors for both

volumetrically and surficially distributed residual radioactivity. The dose factors can be used to

derive clearance levels (Bq/g or Bq/cm2) from an appropriate individual dose criterion (μSv/y). 

The mean, median, and 90% confidence interval (5th and 95th percentiles) for these dose factors

are presented and discussed. Critical-group dose factors are presented in Section 2 for each

radionuclide from among all the materials evaluated. Subsequent sections present critical-group

dose factors for each of the materials evaluated in this analysis: steel, copper, aluminum, and

concrete. 

The doses calculated are annual total effective dose equivalents (TEDE), which is the TEDE

received during a year of exposure in a given scenario. The TEDE is defined (10CFR20) as the

sum of the deep dose equivalent from external exposures and the committed effective dose

equivalent (EDE) from internal exposures. Environmental Protection Agency (EPA) dose

conversion factors were used for all internal dose calculations and for external exposures where

appropriate. The committed EDE from internal exposures was calculated as the 50-year

committed EDE from an intake.

As described above, the dose factors are radionuclide-specific. Each radionuclide dose factor is

based on a unit radioactivity concentration of a single radionuclide at the time of clearance. 

Mixtures of radionuclides have not been addressed in this report, however, the radionuclide dose

factors are additive in the case of a postulated mixture of radionuclides.

This report presents normalized dose factors (μSv/y per Bq/g or mrem/y per pCi/g, and μSv/y per

Bq/cm2

 or mrem/y per pCi/cm2) by which an assumed dose criterion can be divided to give

clearance levels for each radionuclide. Comparisons of dose factors and derived clearance levels

with several other sources are included in Section 2 (e.g., the International Atomic Energy

Agency [IAEA]). An individual dose limit for clearance has not been established. Where

needed, a dose criterion of 10 μSv/y (1 mrem/y) was used for purposes of comparison with other

criteria. The clearance levels thus calculated are for comparative purposes only. 
Section 2 Summary and Comparison of Results

2-1 NUREG-1640

Dose factors for the average member of radionuclide-specific critical groups were calculated for

equipment reuse and material recycle scenarios. The critical group for each radionuclide for each of the

four materials analyzed (steel, copper, aluminum, and concrete) was identified by selecting the highest

mean values from the distribution of dose factors generated for each exposure scenario. Dose factors

for reuse are based on surficial residual radioactivity, and are independent of material type. Reuse dose

factors are less restrictive than recycle dose factors, so they are not discussed further in this section. 

Dose factors for recycle are based on volumetric residual radioactivity; surficial dose factors were

derived by multiplying the volumetric recycle dose factors by a surface-to-mass ratio. 

Over half of the critical groups for recycle of steel, copper, and aluminum describe workers at scrap

yards and steel refineries who transport, handle, and process scrap metal. This is due to a combination

of characteristics of these scenarios: very little delay time following clearance, no mixing or melting, and

involvement of large masses of material. There are also critical groups in scenarios involving handling

refinery products such as slag and baghouse dust. These scenarios involve radionuclides that

concentrate in certain refinery products, and they also involve internal dose pathways. Residual

radioactivity in consumer products rarely yields any critical groups. 

Transportation and handling of concrete debris are important for concrete for the same reasons that they

are important for the metals. In addition, concrete is commonly used as landfill or disposed of in

municipal landfills, so dose factors for a resident living above buried concrete in a closed landfill were

explicitly evaluated and included in the concrete critical group determination. This scenario describes

the critical group for about 25 radionuclides. In most cases, the critical-group dose factors for these

radionuclides are higher for concrete than for the metals.

The results of this analysis were compared to other clearance criteria. The results compare

inconsistently to the acceptable surface contamination levels of Regulatory Guide 1.86. This is probably

due to the fact that the Regulatory Guide values are not based on a pathway analysis. The results of

this analysis compare more favorably with Environmental Protection Agency (EPA) draft dose factors. 

In this comparison, the dose factors are almost all within an order of magnitude indicating that the two

sets of results can be considered in general agreement. The results of this analysis were also

compared with clearance levels published by the European Commission and the International Atomic

Energy Agency. This comparison shows a general level of agreement that is closer than with

Regulatory Guide 1.86 but not as close as with the EPA draft dose factors, and for those radionuclides

where the difference is greater than a factor of 10, the derived clearance levels in this analysis are

almost always more restrictive.

6800$5<$1'&203$5,6212)5(68/76

This section presents a summary, comparison, and brief interpretation of the results of the overall

analysis for clearance of material from Nuclear Regulatory Commission (NRC) licensed

facilities. It does not include a summary of the analysis methodology, but does provide a brief

discussion of key aspects of the methodology where appropriate in order to explain the patterns

of the results. This summary and comparison section contains information that will help

interpretation of the results as well as help indicate the significance of them. 

The following subsection presents tables containing the critical-group dose factors for all

radionuclides, with a brief interpretation of those dose factors. This is followed by subsections

containing comparisons of the results of this analysis with other available clearance criteria. 
Summary and Comparison of Results Section 2

NUREG-1640 2-2

'RVH)DFWRUVIRU0HPEHUVRI&ULWLFDO*URXSV

The critical-group dose factors presented in this report represent the mean dose to the group of

individuals exposed under the circumstances of the most restrictive scenario (highest calculated

dose factor) for each material and radionuclide. The analysis addresses 85 radionuclides and four

materials: steel, copper, aluminum, and concrete. Two types of dose factors are calculated: 

volumetric (mass-based) and derived surficial. The mass-based dose factors have units of μSv/y

per Bq/g (mrem/y per pCi/g) and are calculated using a normalized concentration of 1 pCi/g

distributed throughout the volume of material at the time of release. Derived surficial dose

factors are calculated from the mass-based dose factors using a surface-to-mass ratio according to

the discussion in Section 4.7. Together, these two sets of dose factors provide the technical basis

for formulating a set of clearance levels for material and equipment to be released from NRC

licensed facilities.

Both mass-based and derived surficial dose factors are based on scenarios related to the recycle

or disposal of cleared scrap material. The related issue of equipment cleared for direct reuse is

addressed in Section 3.

Table 2.1 lists the mass-based critical-group dose factors for each of the four materials analyzed

in this report. Several scenarios were evaluated for each material. The values in Table 2.1 are

the highest mean dose factors for each radionuclide from among all exposure scenarios for each

material. Each critical-group dose factor is the mean of a distribution of values calculated for

that scenario. Subsequent sections of this report for each material include tabulations of the 5th,

50th and 95th percentiles of these distributions along with the mean values. Results for steel

appear in Section 4.9. Those for copper are presented in Section 5.8. Results for aluminum are

presented in Section 6.8 and those for concrete are in Section 7.7. A comprehensive tabulation

of the results for all steel, copper, aluminum, and concrete scenarios is presented in Appendices

F, G, H, and I, respectively.

Specific discussions of the scenarios and critical groups associated with the dose factors in

Table 2.1 are presented in subsequent sections of this report. However, there are some general

patterns in the results that are discussed in this summary presentation. Most critical groups for

recycle of steel, copper, and aluminum describe workers at scrap yards and steel refineries who

transport, handle, and process scrap metal or refinery products such as slag and baghouse dust. 

Two scenarios involving exposure to cleared scrap account for more than half of the 85

radionuclides for all metals (scrap transportation and scrap handling scenarios).

There are three reasons why the scrap transportation and handling scenarios are important for the

largest number of radionuclides. First, there is minimal delay between clearance of scrap and

transporting it to the scrap yard so no significant radioactive decay occurs before the scenario

begins for most radionuclides. Consequently, this scenario describes the critical group for many

short-lived radionuclides that decay before later scenarios can occur. Second, unprocessed scrap

has not yet been subjected to mixing with other materials or chemical partitioning during 
Section 2 Summary and Comparison of Results

2-3 NUREG-1640

Table 2.1 Mass-based critical-group dose factors for recycle and disposal of cleared materials

Mean dose factors (μSv/y per Bq/g)

Radionuclide Steel Copper Aluminum Concrete

H-3 6.4E-04 5.6E-04 1.8E-06 8.8E-03

C-14 2.8E-03 1.6E-02 2.6E-04 1.6E+01

Na-22 4.1E+02 2.2E+02 4.4E+00 2.2E+02

P-32 1.3E-01 1.3E-01 2.6E-03 1.4E-01

S-35 7.6E-03 7.8E-04 8.6E-06 3.5E-03

Cl-36 2.7E+00 5.2E-02 6.8E-04 1.6E+02

K-40 5.2E+01 1.6E+01 3.2E-01 4.7E+01

Ca-41 1.3E-01 2.0E-03 1.0E-05 4.8E+00

Ca-45 8.2E-02 5.1E-03 3.0E-05 1.8E-02

Cr-51 2.5E+00 2.5E+00 4.9E-02 2.5E+00

Mn-54 8.5E+01 8.5E+01 1.7E+00 8.5E+01

Fe-55 1.0E-03 9.7E-04 7.3E-05 3.4E-03

Co-57 3.8E+00 3.8E+00 7.6E-02 6.6E+00

Co-58 9.5E+01 9.5E+01 1.9E+00 9.6E+01

Fe-59 1.1E+02 1.1E+02 2.3E+00 1.2E+02

Ni-59 4.5E-04 4.2E-04 2.9E-05 7.4E-03

Co-60 2.5E+02 2.5E+02 5.1E+00 2.5E+02

Ni-63 1.2E-03 1.1E-03 8.2E-05 1.0E-02

Zn-65 2.1E+02 7.8E+01 1.2E+00 6.0E+01

Cu-67 2.1E+00 2.1E+00 4.1E-02 2.9E+00

Se-75 3.6E+01 2.4E+01 4.9E-01 2.5E+01

Sr-85 4.7E+01 4.7E+01 9.4E-01 4.7E+01

Sr-89 1.2E-01 1.2E-01 2.3E-03 1.4E-01

Sr-90 1.0E+01 4.3E-01 1.0E-02 2.2E+00

Y-91 3.5E-01 3.5E-01 6.9E-03 4.3E-01

Mo-93 1.4E-02 1.1E-02 5.5E-04 3.8E+01

Nb-93m 8.4E-03 5.9E-03 8.7E-05 2.0E-02

Nb-94 1.6E+02 1.6E+02 3.3E+00 2.9E+02

Nb-95 7.2E+01 7.2E+01 1.4E+00 7.4E+01

Zr-95 7.2E+01 7.2E+01 1.4E+00 7.3E+01

Tc-99 1.9E-01 2.9E-03 1.8E-04 1.2E+02

Ru-103 4.6E+01 4.6E+01 9.3E-01 4.7E+01

Ru-106 2.1E+01 2.1E+01 4.1E-01 2.1E+01

Ag-108m 1.6E+02 1.6E+02 3.2E+00 1.7E+02

Cd-109 4.4E-01 2.6E-02 1.3E-03 2.5E-01

Ag-110m 2.8E+02 2.8E+02 5.7E+00 2.8E+02

Sb-124 1.8E+02 1.8E+02 3.6E+00 1.8E+02

I-125 2.7E+00 6.5E-02 1.3E-03 3.0E-01

Sb-125 4.1E+01 4.1E+01 8.1E-01 4.1E+01

I-129 6.1E+01 4.4E-01 1.9E-03 2.4E+03

I-131 2.5E+01 2.5E+01 5.0E-01 2.8E+01

Ba-133 2.8E+01 2.8E+01 5.6E-01 2.8E+01

Cs-134 6.6E+02 1.6E+02 3.2E+00 1.6E+02

Cs-137 2.6E+02 6.2E+01 1.2E+00 6.2E+01

Ce-141 2.7E+00 2.7E+00 5.4E-02 3.4E+00

Ce-144 3.3E+00 3.3E+00 6.6E-02 3.3E+00

Pm-147 1.1E-02 6.8E-03 5.5E-05 2.8E-02
Summary and Comparison of Results Section 2

Table 2.1 Mass-based critical-group dose factors for recycle and disposal of cleared materials

Mean dose factors (μSv/y per Bq/g)

Radionuclide Steel Copper Aluminum Concrete

NUREG-1640 2-4

Eu-152 1.1E+02 1.1E+02 2.2E+00 1.1E+02

Eu-154 1.2E+02 1.2E+02 2.4E+00 1.2E+02

Eu-155 1.1E+00 1.1E+00 2.1E-02 2.5E+00

Re-186 2.5E-01 2.5E-01 4.9E-03 3.1E-01

Ir-192 1.2E+02 7.1E+01 1.4E+00 7.2E+01

Pb-210 1.5E+02 3.8E+00 7.5E-01 3.1E+01

Po-210 6.0E+01 1.1E+00 7.4E-02 1.3E+01

Bi-210 3.3E-02 3.1E-02 6.2E-04 9.9E-02

Rn-222 8.6E+01 8.6E+01 1.7E+00 1.1E+02

Ra-223 1.8E+01 1.8E+01 3.6E-01 1.9E+01

Ra-224 6.1E+01 6.1E+01 1.2E+00 7.6E+01

Ac-225 1.4E+01 1.4E+01 2.8E-01 1.5E+01

Ra-225 1.8E+00 4.7E-01 9.6E-03 5.2E+00

Ra-226 1.7E+02 1.7E+02 3.5E+00 5.3E+02

Ac-227 3.4E+02 2.6E+02 1.9E+00 8.4E+02

Th-227 5.9E+00 5.9E+00 1.2E-01 1.1E+01

Th-228 1.3E+02 1.3E+02 2.5E+00 2.7E+02

Ra-228 8.4E+01 8.4E+01 1.7E+00 8.9E+01

Th-229 4.3E+02 3.3E+02 2.3E+00 1.4E+03

Th-230 6.5E+01 5.0E+01 3.4E-01 2.2E+02

Pa-231 2.3E+02 1.8E+02 1.5E+00 2.1E+03

Th-231 1.5E-02 1.5E-02 3.0E-04 3.9E-02

Th-232 2.9E+02 2.2E+02 1.5E+00 1.3E+03

Pa-233 1.3E+01 1.3E+01 2.6E-01 1.4E+01

U-233 3.4E+01 2.5E+01 1.8E-01 1.7E+02

Th-234 7.3E-01 7.3E-01 1.5E-02 7.5E-01

U-234 3.3E+01 2.5E+01 1.7E-01 1.7E+02

U-235 3.2E+01 2.5E+01 1.6E-01 1.4E+02

Np-237 2.0E+03 1.1E+02 7.2E-01 7.1E+04

Pu-238 7.1E+01 5.5E+01 3.8E-01 1.7E+02

U-238 2.9E+01 2.3E+01 1.5E-01 1.3E+02

Pu-239 7.6E+01 5.8E+01 4.0E-01 2.2E+02

Pu-240 7.6E+01 5.7E+01 4.0E-01 2.2E+02

Pu-241 1.2E+00 9.4E-01 6.5E-03 1.7E+01

Am-241 1.1E+02 9.0E+01 5.9E-01 3.3E+02

Cm-242 4.3E+00 3.0E+00 2.3E-02 1.1E+01

Pu-242 7.3E+01 5.4E+01 3.8E-01 2.1E+02

Cm-244 6.3E+01 4.9E+01 3.3E-01 1.6E+02

 Note: to convert these values to conventional units (mrem/y per pCi/g) multiply by 3.70E-03

refining. This means that the initial radionuclide concentration is unchanged. Third, relatively

large masses of scrap material are transported in each load so relatively larger amounts of

radioactivity are present in this scenario than in most others. Because the scrap transportation

scenario involves only the external dose pathway, the radionuclides for which this scenario

describes the critical group are all gamma emitters.
Section 2 Summary and Comparison of Results

2-5 NUREG-1640

Radionuclides with critical groups in slag, dust, and offgas scenarios are those which concentrate

in these materials during the refining process. All of these scenarios include internal dose

pathways: inhalation of dust, inadvertent ingestion, consumption of drinking water or ingestion

of garden produce. The radionuclides for which these material-specific scenarios describe

critical groups all have relatively long half-lives and are alpha or beta emitters that contribute to

internal dose pathways. 

Four radionuclides (H-3, C-14, Cl-36, and I-129) have a critical group consisting of members of

the general public living in the vicinity of metal refineries exposed to refinery atmospheric

releases. These are all volatile radionuclides with no external dose component.

Residual radioactivity in consumer products rarely yields any critical groups. There are four

reasons for this. First, the passage of time between clearance and the use of consumer products

allows many radionuclides to decay to very small concentrations. Second, the amount of all

metals available from NRC licensed facilities is small compared to the total amounts that are

recycled each year. Mixing cleared metals with other metals reduces concentrations of

radioactivity in finished products. Third, many radionuclides are partitioned to slag or baghouse

dust during refining and do not appear in finished metals. Finally, the relatively small size of

consumer products (compared to the amounts of scrap metals encountered by refinery workers)

limits the amount of radioactivity to which any individual could be exposed in these scenarios. 

In contrast, workers at scrap yards and steel refineries can be exposed to relatively large amounts

of cleared steel before mixing, processing, or radioactive decay can take place.

For most radionuclides, the highest mass-based critical-group dose factor for the three metals are

those for steel. Copper and aluminum critical-group dose factors for similar scenarios are

smaller than those for steel due to the relatively smaller amounts of copper and aluminum

available for clearance compared to the typical capacity of refineries for these metals.

Concrete presents a somewhat different case from the metals. Transportation and handling of

concrete debris are important for the same reasons that they are important for the metals. In

addition, concrete is commonly used as landfill or disposed of in municipal landfills. Potential

doses to a resident living above buried concrete in a closed landfill were explicitly evaluated and

included in the concrete critical group determination. This scenario describes the critical group

for 28 long-lived, water-soluble radionuclides that contribute to ingestion and drinking water

pathway doses. In most cases, the critical-group dose factors for these radionuclides are higher

for concrete than for the metals.

Table 2.2 lists the derived surficial critical-group dose factors for the four materials analyzed in

this report. For all radionuclides, the critical group for the derived surficial dose factor is the

same as for the corresponding mass-based dose factor. The derived surficial dose factors are

calculated from the mass-based dose factors using a surface-to-mass ratio appropriate for each

material. Like the rest of this analysis, the derivation of surficial dose factors is a probabilistic

calculation that takes into account the uncertainty in surface-to-mass ratio. This calculation is

discussed in Section 4.7.
Summary and Comparison of Results Section 2

NUREG-1640 2-6

Table 2.2 Surficial critical-group dose factors for recycle and disposal of cleared materials

Mean dose factors (μSv/y per Bq/cm2

)

Radionuclide Steel Copper Aluminum Concrete

H-3 4.8E-04 4.8E-04 6.8E-06 1.9E-04

C-14 2.1E-03 1.4E-02 1.0E-03 3.7E-01

Na-22 3.2E+02 1.9E+02 1.8E+01 5.2E+00

P-32 9.9E-02 1.1E-01 1.1E-02 3.2E-03

S-35 5.6E-03 6.6E-04 3.5E-05 5.3E-05

Cl-36 2.1E+00 4.4E-02 2.8E-03 3.2E+00

K-40 4.0E+01 1.4E+01 1.3E+00 1.1E+00

Ca-41 9.8E-02 1.7E-03 4.1E-05 1.2E-01

Ca-45 6.1E-02 4.3E-03 1.2E-04 4.2E-04

Cr-51 1.9E+00 2.1E+00 2.0E-01 6.0E-02

Mn-54 6.4E+01 7.3E+01 6.9E+00 2.0E+00

Fe-55 7.6E-04 8.3E-04 2.9E-04 8.0E-05

Co-57 2.9E+00 3.3E+00 3.1E-01 1.5E-01

Co-58 7.2E+01 8.1E+01 7.7E+00 2.3E+00

Fe-59 8.7E+01 9.8E+01 9.3E+00 2.7E+00

Ni-59 3.4E-04 3.6E-04 1.2E-04 1.8E-04

Co-60 1.9E+02 2.2E+02 2.1E+01 6.0E+00

Ni-63 9.1E-04 9.7E-04 3.2E-04 2.4E-04

Zn-65 1.6E+02 6.7E+01 4.8E+00 1.4E+00

Cu-67 1.6E+00 1.8E+00 1.7E-01 6.8E-02

Se-75 2.7E+01 2.1E+01 2.0E+00 5.9E-01

Sr-85 3.6E+01 4.0E+01 3.8E+00 1.1E+00

Sr-89 8.8E-02 9.9E-02 9.4E-03 3.3E-03

Sr-90 7.5E+00 3.7E-01 4.0E-02 5.5E-02

Y-91 2.6E-01 3.0E-01 2.8E-02 1.0E-02

Mo-93 1.1E-02 9.5E-03 2.2E-03 8.5E-01

Nb-93m 6.4E-03 5.0E-03 3.4E-04 4.7E-04

Nb-94 1.2E+02 1.4E+02 1.3E+01 7.3E+00

Nb-95 5.5E+01 6.2E+01 5.8E+00 1.7E+00

Zr-95 5.4E+01 6.2E+01 5.8E+00 1.7E+00

Tc-99 1.4E-01 2.5E-03 7.2E-04 2.6E+00

Ru-103 3.5E+01 4.0E+01 3.7E+00 1.1E+00

Ru-106 1.6E+01 1.8E+01 1.7E+00 4.9E-01

Ag-108m 1.2E+02 1.4E+02 1.3E+01 4.3E+00

Cd-109 3.3E-01 2.2E-02 5.1E-03 5.8E-03

Ag-110m 2.1E+02 2.4E+02 2.3E+01 6.7E+00

Sb-124 1.4E+02 1.5E+02 1.5E+01 4.3E+00

I-125 2.1E+00 5.6E-02 5.3E-03 7.1E-03

Sb-125 3.1E+01 3.5E+01 3.3E+00 9.6E-01

I-129 4.6E+01 3.7E-01 7.5E-03 5.1E+01

I-131 1.9E+01 2.1E+01 2.0E+00 6.5E-01

Ba-133 2.1E+01 2.4E+01 2.3E+00 6.6E-01

Cs-134 4.9E+02 1.4E+02 1.3E+01 3.8E+00

Cs-137 2.0E+02 5.3E+01 5.0E+00 1.5E+00

Ce-141 2.1E+00 2.3E+00 2.2E-01 8.0E-02

Ce-144 2.5E+00 2.8E+00 2.7E-01 7.8E-02

Pm-147 8.4E-03 5.8E-03 2.2E-04 4.4E-04
Section 2 Summary and Comparison of Results

Table 2.2 Surficial critical-group dose factors for recycle and disposal of cleared materials

Mean dose factors (μSv/y per Bq/cm2

)

Radionuclide Steel Copper Aluminum Concrete

2-7 NUREG-1640

Eu-152 8.4E+01 9.5E+01 9.0E+00 2.6E+00

Eu-154 9.2E+01 1.0E+02 9.8E+00 2.9E+00

Eu-155 8.0E-01 9.1E-01 8.6E-02 5.8E-02

Re-186 1.9E-01 2.1E-01 2.0E-02 7.2E-03

Ir-192 8.9E+01 6.1E+01 5.7E+00 1.7E+00

Pb-210 1.2E+02 3.3E+00 3.0E+00 7.4E-01

Po-210 4.4E+01 9.0E-01 2.9E-01 3.1E-01

Bi-210 2.5E-02 2.7E-02 2.5E-03 2.3E-03

Rn-222 6.5E+01 7.3E+01 6.9E+00 2.5E+00

Ra-223 1.4E+01 1.5E+01 1.5E+00 4.5E-01

Ra-224 4.6E+01 5.2E+01 4.9E+00 1.8E+00

Ac-225 1.1E+01 1.2E+01 1.1E+00 3.6E-01

Ra-225 1.4E+00 4.0E-01 3.9E-02 1.2E-01

Ra-226 1.3E+02 1.5E+02 1.4E+01 1.3E+01

Ac-227 2.5E+02 2.3E+02 7.6E+00 2.0E+01

Th-227 4.4E+00 5.0E+00 4.7E-01 2.6E-01

Th-228 9.6E+01 1.1E+02 1.0E+01 6.3E+00

Ra-228 6.3E+01 7.2E+01 6.8E+00 2.1E+00

Th-229 3.3E+02 2.9E+02 9.2E+00 3.3E+01

Th-230 4.9E+01 4.3E+01 1.4E+00 5.3E+00

Pa-231 1.7E+02 1.6E+02 5.9E+00 5.0E+01

Th-231 1.1E-02 1.3E-02 1.2E-03 9.2E-04

Th-232 2.2E+02 1.9E+02 6.1E+00 3.2E+01

Pa-233 1.0E+01 1.1E+01 1.1E+00 3.2E-01

U-233 2.5E+01 2.1E+01 7.2E-01 3.8E+00

Th-234 5.5E-01 6.2E-01 5.9E-02 1.8E-02

U-234 2.5E+01 2.1E+01 7.0E-01 3.8E+00

U-235 2.4E+01 2.1E+01 6.6E-01 3.2E+00

Np-237 1.4E+03 9.4E+01 2.9E+00 1.4E+03

Pu-238 5.4E+01 4.8E+01 1.5E+00 4.0E+00

U-238 2.2E+01 2.0E+01 6.3E-01 3.1E+00

Pu-239 5.8E+01 5.0E+01 1.6E+00 5.4E+00

Pu-240 5.8E+01 4.9E+01 1.6E+00 5.4E+00

Pu-241 9.3E-01 8.1E-01 2.6E-02 4.0E-01

Am-241 8.5E+01 7.8E+01 2.4E+00 8.0E+00

Cm-242 3.2E+00 2.5E+00 9.1E-02 2.5E-01

Pu-242 5.5E+01 4.6E+01 1.5E+00 5.1E+00

Cm-244 4.8E+01 4.2E+01 1.3E+00 3.7E+00

 Note: to convert these values to conventional units (mrem/y per pCi/cm2

) multiply by 3.70E-03

The derived surficial critical-group dose factors for steel and copper in Table 2.2 are slightly

smaller than the corresponding mass-based dose factors in Table 2.1. This is because the average

surface-to-mass ratio for typical steel and copper objects are slightly less than 1 cm2

/g. The

derived surficial dose factors for aluminum in Table 2.2 are larger than the corresponding massbased dose factors because the average surface-to-mass ratio for typical aluminum objects is

about 4 cm2/g. This is largely a consequence of the lower density of aluminum rather than the
Summary and Comparison of Results Section 2

NUREG-1640 2-8

size and shape of typical aluminum objects. The surface-to-mass ratio for cleared concrete is

significantly smaller, averaging about 0.02 cm2

/g. This reflects the surface-to-mass ratios of

large concrete objects such as walls and floor slabs. 

&RPSDULVRQRI5HVXOWVZLWK2WKHU&OHDUDQFH&ULWHULD

In order to establish a context for interpreting the results of this analysis, they can be compared to

other clearance criteria. The four available sets of criteria are the existing Regulatory Guide 1.86

surface contamination levels, the draft dose factors of the Environmental Protection Agency

(EPA), and the draft clearance levels of the European Commission (EC) and the International

Atomic Energy Agency (IAEA). Each of these sets of criteria are intended for slightly different

purposes and are formulated differently. In particular, they are presented in different sets of

units. The results of this analysis are comprehensive enough that they can be modified to allow

direct comparison with each of the four sets of criteria using the units of each criterion.

&RPSDULVRQZLWK5HJXODWRU\*XLGH

Table 2.3 compares the results of this analysis with the average surface contamination levels of

Regulatory Guide 1.86 (AEC 1974). The criteria in Regulatory Guide 1.86 are not dose-based

and are stated in terms of surficial contamination levels (dpm/100cm2

). They do not address

volumetric contamination levels and they do not specify the materials to which they apply.

The dose factors developed for this report do not, by themselves, specify surficial contamination

levels for clearance. In order to compare the results of this analysis to the Regulatory Guide 1.86

acceptable contamination levels, it is necessary to assume some annual individual dose criterion. 

No annual individual dose level for clearance has been established by the NRC, but for purposes

of this comparison a value of 10 μSv/y (1 mrem/y) has been used. While this dose criterion has

not been established by regulation for clearance, it is the proposed criterion for the EC and the

IAEA. Use of this value allows comparison across all sets of criteria.

The NRC clearance levels in the second column of Table 2.3 represent the results of this analysis

expressed in units of dpm/100cm2. They were calculated from the surficial dose factors in

Table 2.2 using Equation 2.1. Consistent with the intended use of Regulatory Guide 1.86, the

highest surficial critical-group dose factor from the four materials was used for each

radionuclide.

Clearance level = (dose criterion ÷ Dose Factor surficial) * 60,000 2.1

where

Clearance level = derived clearance level expressed in Reg. Guide 1.86 units (dpm/100cm2

)

and

dose criterion = assumed annual individual dose criterion for clearance (10 μSv/y)

Dose Factor surficial = highest derived surficial dose factor from Table 2.2 (μSv/y per Bq/cm2

)

60,000 = constant for unit conversions
Section 2 Summary and Comparison of Results

2-9 NUREG-1640

Table 2.3 Comparison of derived NRC surficial clearance levels with Regulatory Guide 1.86 acceptable

contamination levels (across all materials)

NRC Reg. Guide 1.86 Ratio

Radionuclide (dpm/100 cm2

) (dpm/100 cm2) NRC / Reg. Guide 1.86

H-3 1.3E+08 5000 3.E+04

C-14 1.6E+05 5000 3.E+01

Na-22 1.9E+02 5000 4.E-02

P-32 5.4E+05 5000 1.E+02

S-35 1.1E+07 5000 2.E+03

Cl-36 1.9E+04 5000 4.E+00

K-40 1.5E+03 5000 3.E-01

Ca-41 5.1E+05 5000 1.E+02

Ca-45 9.9E+05 5000 2.E+02

Cr-51 2.8E+04 5000 6.E+00

Mn-54 8.2E+02 5000 2.E-01

Fe-55 7.3E+07 5000 1.E+04

Co-57 1.8E+04 5000 4.E+00

Co-58 7.4E+02 5000 1.E-01

Fe-59 6.1E+02 5000 1.E-01

Ni-59 1.7E+08 5000 3.E+04

Co-60 2.8E+02 5000 6.E-02

Ni-63 6.2E+07 5000 1.E+04

Zn-65 3.7E+02 5000 7.E-02

Cu-67 3.4E+04 5000 7.E+00

Se-75 2.3E+03 5000 5.E-01

Sr-85 1.5E+03 5000 3.E-01

Sr-89 6.0E+05 5000 1.E+02

Sr-90 8.0E+03 1000 8.E+00

Y-91 2.0E+05 5000 4.E+01

Mo-93 7.0E+04 5000 1.E+01

Nb-93m 9.3E+06 5000 2.E+03

Nb-94 4.3E+02 5000 9.E-02

Nb-95 9.7E+02 5000 2.E-01

Zr-95 9.7E+02 5000 2.E-01

Tc-99 2.3E+04 5000 5.E+00

Ru-103 1.5E+03 5000 3.E-01

Ru-106 3.4E+03 5000 7.E-01

Ag-108m 4.3E+02 5000 9.E-02

Cd-109 1.8E+05 5000 4.E+01

Ag-110m 2.5E+02 5000 5.E-02

Sb-124 3.9E+02 5000 8.E-02

I-125 2.8E+04 100 3.E+02

Sb-125 1.7E+03 5000 3.E-01

I-129 1.2E+03 100 1.E+01

I-131 2.8E+03 1000 3.E+00

Ba-133 2.5E+03 5000 5.E-01

Cs-134 1.2E+02 5000 2.E-02

Cs-137 3.0E+02 5000 6.E-02

Ce-141 2.6E+04 5000 5.E+00

Ce-144 2.1E+04 5000 4.E+00

Pm-147 7.1E+06 5000 1.E+03
Summary and Comparison of Results Section 2

Table 2.3 Comparison of derived NRC surficial clearance levels with Regulatory Guide 1.86 acceptable

contamination levels (across all materials)

NRC Reg. Guide 1.86 Ratio

Radionuclide (dpm/100 cm2

) (dpm/100 cm2) NRC / Reg. Guide 1.86

NUREG-1640 2-10

Eu-152 6.3E+02 5000 1.E-01

Eu-154 5.8E+02 5000 1.E-01

Eu-155 6.6E+04 5000 1.E+01

Re-186 2.9E+05 5000 6.E+01

Ir-192 6.8E+02 5000 1.E-01

Pb-210 5.2E+02 5000 1.E-01

Po-210 1.4E+03 5000 3.E-01

Bi-210 2.3E+06 5000 5.E+02

Rn-222 8.2E+02 5000 2.E-01

Ra-223 3.9E+03 1000 4.E+00

Ra-224 1.2E+03 1000 1.E+00

Ac-225 5.0E+03 5000 1.E+00

Ra-225 4.4E+04 5000 9.E+00

Ra-226 4.0E+02 100 4.E+00

Ac-227 2.4E+02 100 2.E+00

Th-227 1.2E+04 5000 2.E+00

Th-228 5.5E+02 100 6.E+00

Ra-228 8.4E+02 100 8.E+00

Th-229 1.8E+02 5000 4.E-02

Th-230 1.2E+03 100 1.E+01

Pa-231 3.5E+02 100 4.E+00

Th-231 4.8E+06 5000 1.E+03

Th-232 2.8E+02 1000 3.E-01

Pa-233 5.3E+03 100 5.E+01

U-233 2.4E+03 5000 5.E-01

Th-234 9.6E+04 5000 2.E+01

U-234 2.4E+03 5000 5.E-01

U-235 2.5E+03 5000 5.E-01

Np-237 4.2E+01 100 4.E-01

Pu-238 1.1E+03 100 1.E+01

U-238 2.7E+03 5000 5.E-01

Pu-239 1.0E+03 100 1.E+01

Pu-240 1.0E+03 100 1.E+01

Pu-241 6.4E+04 100 6.E+02

Am-241 7.0E+02 100 7.E+00

Cm-242 1.8E+04 100 2.E+02

Pu-242 1.1E+03 100 1.E+01

Cm-244 1.3E+03 100 1.E+01

The Regulatory Guide 1.86 surface contamination levels are taken from Table 1 of Regulatory

Guide 1.86. The ratios of the results of this analysis to the values in Regulatory Guide 1.86 vary

over a wide range. Where this ratio is plus-or-minus an order of magnitude (0.1 to 10) the two

sets of criteria can be considered in general agreement. The ratio is greater than 1.0 for 50 out of

the 85 radionuclides listed in Table 2.3., indicating that the current analysis produces clearance

levels less restrictive than Regulatory Guide 1.86 for these radionuclides. Radionuclides in this
Section 2 Summary and Comparison of Results

2-11 NUREG-1640

group include all the low-energy beta emitters and most of the transuranic radionuclides. For the

remaining 35 radionuclides the ratio is less than 1.0, indicating that the results of this analysis

produce clearance levels more restrictive than Regulatory Guide 1.86. Radionuclides in this

group include all the highest energy gamma-emitting radionuclides (e.g., Co-60). There are 10

radionuclides for which this analysis produces clearance levels that are more than a factor of 10

more restrictive than Regulatory Guide 1.86.

&RPSDULVRQZLWKWKH(QYLURQPHQWDO3URWHFWLRQ$JHQF\

The EPA has sponsored an analysis of doses from clearance and recycle of scrap steel

(EPA 1997a). The results of this analysis are currently available only in draft form. No

clearance levels have yet been established as regulations by the EPA. 

The draft EPA dose factors were developed using an approach that is similar to the one presented

in this report. They are based on estimating annual doses to individuals under a variety of

scenarios formulated to represent standard industry practices in the United States. Dose factors

address only recycle of volumetrically distributed contamination, and results are expressed as

normalized annual individual dose factors in units of mrem/year per pCi/g. No annual dose level

is specified. The draft published results are limited to clearance of iron and steel.

The EPA results are expressed as normalized annual dose factors, so they can be directly

compared to the results in this report. No unit conversions or assumptions regarding an annual

individual dose criterion are required. Table 2.4 presents this comparison for the 40

radionuclides in common between the two analyses. The NRC dose factors in the second column

of Table 2.4 are mass-based critical-group dose factors for steel recycle taken from Table 2.1 of

this report, expressed in conventional units. The EPA dose factors are taken from Table 7-1 of

EPA (1997a). Both sets of values are expressed as dose factors, which are inversely proportional

to the clearance levels that would likely be embodied in a clearance rule.

The ratio of EPA values to NRC values in the fourth column of Table 2.4 shows a much

narrower range than the comparison with Regulatory Guide 1.86 clearance levels. For 36 of the

40 radionuclides in common, this ratio is plus-or-minus an order of magnitude (0.1 to 10)

indicating that the two sets of criteria can be considered in general agreement. Where the ratio is

greater than 10 (e.g., C-14, Sr-90), the NRC dose factors from this analysis would indicate a

clearance level that is less restrictive than the EPA values. Where the ratio is less than 0.1

(Tc-99, Cs-137), the NRC values would be more restrictive.

&RPSDULVRQZLWKWKH(XURSHDQ&RPPLVVLRQ

The EC has sponsored an analysis of doses from clearance and recycle of scrap steel, copper, and

aluminum (EC 1998). The results of this analysis are currently available as recommended

clearance levels for member states of the European Union for recycling of metals originating

from the dismantling of nuclear facilities. 
Summary and Comparison of Results Section 2

NUREG-1640 2-12

Table 2.4 Comparison of NRC mass-based steel recycle critical-group dose factors with EPA values

NRC EPA Ratio

Radionuclide (mrem/y per pCi/g) (mrem/y per pCi/g) EPA / NRC

H-3 2.4E-06 - -

C-14 1.0E-05 8.7.E-04 8.E+01

Na-22 1.5E+00 - -

P-32 4.8E-04 - -

S-35 2.8E-05 - -

Cl-36 1.0E-02 - -

K-40 1.9E-01 - -

Ca-41 4.9E-04 - -

Ca-45 3.0E-04 - -

Cr-51 9.1E-03 - -

Mn-54 3.2E-01 2.0E-01 6.E-01

Fe-55 3.8E-06 6.7E-06 2.E+00

Co-57 1.4E-02 - -

Co-58 3.5E-01 - -

Fe-59 4.2E-01 - -

Ni-59 1.6E-06 4.4E-06 3.E+00

Co-60 9.4E-01 9.0E-01 1.E+00

Ni-63 4.5E-06 1.1E-05 2.E+00

Zn-65 7.9E-01 9.6E-02 1.E-01

Cu-67 7.7E-03 - -

Se-75 1.3E-01 - -

Sr-85 1.7E-01 - -

Sr-89 4.3E-04 - -

Sr-90 3.8E-02 1.5E+00 4.E+01

Y-91 1.3E-03 - -

Mo-93 5.2E-05 5.6E-05 1.E+00

Nb-93m 3.1E-05 - -

Nb-94 6.1E-01 4.7E-01 8.E-01

Nb-95 2.7E-01 - -

Zr-95 2.7E-01 - -

Tc-99 7.0E-04 2.1E-05 3.E-02

Ru-103 1.7E-01 - -

Ru-106 7.6E-02 5.2E-02 7.E-01

Ag-108m 6.0E-01 - -

Cd-109 1.6E-03 - -

Ag-110m 1.0E+00 6.3E-01 6.E-01

Sb-124 6.7E-01 - -

I-125 1.0E-02 - -

Sb-125 1.5E-01 6.4E-02 4.E-01

I-129 2.3E-01 7.9E-01 4.E+00

I-131 9.3E-02 - -

Ba-133 1.0E-01 - -

Cs-134 2.4E+00 2.5E-01 1.E-01

Cs-137 9.5E-01 8.9E-02 9.E-02

Ce-141 1.0E-02 - -

Ce-144 1.2E-02 1.8E-02 1.E+00

Pm-147 4.2E-05 1.4E-04 3.E+00

Eu-152 4.1E-01 3.4E-01 8.E-01

Eu-154 4.5E-01 - -
Section 2 Summary and Comparison of Results

Table 2.4 Comparison of NRC mass-based steel recycle critical-group dose factors with EPA values

NRC EPA Ratio

Radionuclide (mrem/y per pCi/g) (mrem/y per pCi/g) EPA / NRC

2-13 NUREG-1640

Eu-155 3.9E-03 - -

Re-186 9.1E-04 - -

Ir-192 4.4E-01 - -

Pb-210 5.7E-01 3.1E+00 5.E+00

Po-210 2.2E-01 - -

Bi-210 1.2E-04 - -

Rn-222 3.2E-01 - -

Ra-223 6.7E-02 - -

Ra-224 2.3E-01 - -

Ac-225 5.3E-02 - -

Ra-225 6.7E-03 - -

Ra-226 6.4E-01 6.3E-01 1.E+00

Ac-227 1.3E+00 8.0E+00 6.E+00

Th-227 2.2E-02 - -

Th-228 4.7E-01 1.4E+00 3.E+00

Ra-228 3.1E-01 3.7E-01 1.E+00

Th-229 1.6E+00 4.4E+00 3.E+00

Th-230 2.4E-01 6.4E-01 3.E+00

Pa-231 8.3E-01 2.5E+00 3.E+00

Th-231 5.5E-05 - -

Th-232 1.1E+00 2.8E+00 3.E+00

Pa-233 4.9E-02 - -

U-233 1.2E-01 - -

Th-234 2.7E-03 - -

U-234 1.2E-01 3.1E-01 3.E+00

U-235 1.2E-01 3.3E-01 3.E+00

Np-237 7.4E+00 1.5E+00 2.E-01

Pu-238 2.6E-01 6.8E-01 3.E+00

U-238 1.1E-01 2.9E-01 3.E+00

Pu-239 2.8E-01 7.3E-01 3.E+00

Pu-240 2.8E-01 7.3E-01 3.E+00

Pu-241 4.5E-03 1.2E-02 3.E+00

Am-241 4.2E-01 1.2E+00 3.E+00

Cm-242 1.6E-02 - -

Pu-242 2.7E-01 6.9E-01 3.E+00

Cm-244 2.3E-01 6.8E-01 3.E+00

The EC recommended clearance levels were developed using an approach that is similar to the

one presented in this report in that they are based on estimating annual doses to individuals under

a variety of scenarios formulated to represent standard industry practices. However, they are

based on European industry practices rather than the industry in the United States. Clearance

levels address both volumetrically and surficially distributed contamination. The clearance levels

are based on an annual individual dose level of 10 μSv/y, and are expressed in units of Bq/g or

Bq/cm2

, as appropriate. 
Summary and Comparison of Results Section 2

NUREG-1640 2-14

Table 2.5 compares the results in this report to the recommended EC clearance levels for the 62

radionuclides they have in common. The EC clearance levels in Table 2.5 were taken from

Table 3-1 of EC (1998), and represent the most restrictive clearance level for each radionuclide

among the three metals analyzed by the EC (steel, copper, and aluminum).

The NRC clearance levels in the Table 2.5 represent the results of this analysis expressed in units

of Bq/g or Bq/cm2, as appropriate for comparison. Mass-based clearance levels were calculated

from the dose factors in Table 2.1 and surficial clearance levels were calculated from the dose

factors in Table 2.2 of this report. In each case, the most restrictive dose factor among the three

metals was used for each radionuclide. Equation 2.2 was used to calculate a clearance level for

comparison with the EC values.

Clearance level = Dose criterion ÷ Dose Factor 2.2

where

Clearance level = derived clearance level expressed in EC units (Bq/g or Bq/cm2

)

and

Dose criterion = annual individual dose criterion (10 μSv/y)

Dose Factor = dose factor from Table 2.1 or 2.2 (μSv/y per Bq/g or μSv/y per Bq/cm2

)

The ratio of the results of this analysis to the EC clearance levels shows a general level of

agreement that is closer than with Regulatory Guide 1.86 but not as close as with the draft EPA

dose factors. Where this ratio is plus-or-minus an order of magnitude (0.1 to 10) the two sets of

criteria can be considered in general agreement. For each radionuclide, the ratio differs between

the mass-based and the surficial clearance level. This is because the derived surficial dose

factors in this report are calculated from the mass-based dose factors using a surface-to-mass

ratio appropriate to each material. The EC surficial clearance levels are based on a set of

scenarios different from those used for their mass-based clearance level. A surface-to-mass ratio

was not explicitly addressed in the EC analysis. For both mass-based and surficial clearance

levels, where the ratio is greater than 1.0 the NRC values would indicate a clearance level that is

less restrictive than the EC values. Where the ratio is less than 1.0 the NRC values would be

more restrictive. For those radionuclides where the ratio is greater than a factor of 10 different,

the derived clearance levels in this analysis are more restrictive for all radionuclides except one

(H-3).

&RPSDULVRQZLWKWKH,QWHUQDWLRQDO$WRPLF(QHUJ\$JHQF\

The IAEA has sponsored development of draft clearance levels intended for application to all

solid materials irrespective of the disposition of the materials (IAEA 1996). The results of the

analysis are currently available only in draft form. Final recommended clearance levels have not

yet been established by the IAEA. 
Section 2 Summary and Comparison of Results

2-15 NUREG-1640

Table 2.5 Comparison of derived NRC clearance levels with European Commission values (all metals)

Mass clearance levels Surficial clearance levels

NRC EC Ratio NRC EC Ratio

Radionuclide (Bq/g) (Bq/g) NRC / EC Radionuclide (Bq/cm2

) (Bq/cm2) NRC / EC

H-3 2.E+04 1000 2.E+01 H-3 2.E+04 100000 2.E-01

C-14 6.E+02 100 6.E+00 C-14 7.E+02 1000 7.E-01

Na-22 2.E-02 1 2.E-02 Na-22 3.E-02 10 3.E-03

P-32 8.E+01 - - P-32 9.E+01 - -

S-35 1.E+03 1000 1.E+00 S-35 2.E+03 1000 2.E+00

Cl-36 4.E+00 10 4.E-01 Cl-36 5.E+00 100 5.E-02

K-40 2.E-01 1 2.E-01 K-40 3.E-01 100 3.E-03

Ca-41 8.E+01 - - Ca-41 1.E+02 - -

Ca-45 1.E+02 1000 1.E-01 Ca-45 2.E+02 100 2.E+00

Cr-51 4.E+00 - - Cr-51 5.E+00 - -

Mn-54 1.E-01 1 1.E-01 Mn-54 1.E-01 10 1.E-02

Fe-55 1.E+04 10000 1.E+00 Fe-55 1.E+04 10000 1.E+00

Co-57 3.E+00 10 3.E-01 Co-57 3.E+00 100 3.E-02

Co-58 1.E-01 1 1.E-01 Co-58 1.E-01 10 1.E-02

Fe-59 9.E-02 - - Fe-59 1.E-01 - -

Ni-59 2.E+04 10000 2.E+00 Ni-59 3.E+04 10000 3.E+00

Co-60 4.E-02 1 4.E-02 Co-60 5.E-02 10 5.E-03

Ni-63 8.E+03 10000 8.E-01 Ni-63 1.E+04 10000 1.E+00

Zn-65 5.E-02 1 5.E-02 Zn-65 6.E-02 100 6.E-04

Cu-67 5.E+00 - - Cu-67 6.E+00 - -

Se-75 3.E-01 1 3.E-01 Se-75 4.E-01 100 4.E-03

Sr-85 2.E-01 1 2.E-01 Sr-85 2.E-01 100 2.E-03

Sr-89 9.E+01 - - Sr-89 1.E+02 - -

Sr-90 1.E+00 10 1.E-01 Sr-90 1.E+00 10 1.E-01

Y-91 3.E+01 10 3.E+00 Y-91 3.E+01 100 3.E-01

Mo-93 7.E+02 100 7.E+00 Mo-93 9.E+02 1000 9.E-01

Nb-93m 1.E+03 1000 1.E+00 Nb-93m 2.E+03 10000 2.E-01

Nb-94 6.E-02 1 6.E-02 Nb-94 7.E-02 10 7.E-03

Nb-95 1.E-01 - - Nb-95 2.E-01 - -

Zr-95 1.E-01 1 1.E-01 Zr-95 2.E-01 10 2.E-02

Tc-99 5.E+01 100 5.E-01 Tc-99 7.E+01 1000 7.E-02

Ru-103 2.E-01 - - Ru-103 3.E-01 - -

Ru-106 5.E-01 1 5.E-01 Ru-106 6.E-01 10 6.E-02

Ag-108m 6.E-02 1 6.E-02 Ag-108m 7.E-02 10 7.E-03

Cd-109 2.E+01 10 2.E+00 Cd-109 3.E+01 100 3.E-01

Ag-110m 4.E-02 1 4.E-02 Ag-110m 4.E-02 10 4.E-03

Sb-124 6.E-02 1 6.E-02 Sb-124 6.E-02 10 6.E-03

I-125 4.E+00 1 4.E+00 I-125 5.E+00 100 5.E-02

Sb-125 2.E-01 10 2.E-02 Sb-125 3.E-01 100 3.E-03

I-129 2.E-01 1 2.E-01 I-129 2.E-01 10 2.E-02

I-131 4.E-01 - - I-131 5.E-01 - -

Ba-133 4.E-01 - - Ba-133 4.E-01 - -

Cs-134 2.E-02 1 2.E-02 Cs-134 2.E-02 10 2.E-03

Cs-137 4.E-02 1 4.E-02 Cs-137 5.E-02 100 5.E-04

Ce-141 4.E+00 - - Ce-141 4.E+00 - -

Ce-144 3.E+00 10 3.E-01 Ce-144 4.E+00 10 4.E-01

Pm-147 9.E+02 10000 9.E-02 Pm-147 1.E+03 1000 1.E+00
Summary and Comparison of Results Section 2

Table 2.5 Comparison of derived NRC clearance levels with European Commission values (all metals)

Mass clearance levels Surficial clearance levels

NRC EC Ratio NRC EC Ratio

Radionuclide (Bq/g) (Bq/g) NRC / EC Radionuclide (Bq/cm2

) (Bq/cm2) NRC / EC

NUREG-1640 2-16

Eu-152 9.E-02 1 9.E-02 Eu-152 1.E-01 10 1.E-02

Eu-154 8.E-02 1 8.E-02 Eu-154 1.E-01 10 1.E-02

Eu-155 9.E+00 10 9.E-01 Eu-155 1.E+01 1000 1.E-02

Re-186 4.E+01 - - Re-186 5.E+01 - -

Ir-192 8.E-02 1 8.E-02 Ir-192 1.E-01 10 1.E-02

Pb-210 7.E-02 1 7.E-02 Pb-210 9.E-02 1 9.E-02

Po-210 2.E-01 1 2.E-01 Po-210 2.E-01 0.1 2.E+00

Bi-210 3.E+02 - - Bi-210 4.E+02 - -

Rn-222 1.E-01 - - Rn-222 1.E-01 - -

Ra-223 6.E-01 - - Ra-223 6.E-01 - -

Ra-224 2.E-01 - - Ra-224 2.E-01 - -

Ac-225 7.E-01 - - Ac-225 8.E-01 - -

Ra-225 6.E+00 - - Ra-225 7.E+00 - -

Ra-226 6.E-02 1 6.E-02 Ra-226 7.E-02 0.1 7.E-01

Ac-227 3.E-02 - - Ac-227 4.E-02 - -

Th-227 2.E+00 - - Th-227 2.E+00 - -

Th-228 8.E-02 1 8.E-02 Th-228 9.E-02 0.1 9.E-01

Ra-228 1.E-01 1 1.E-01 Ra-228 1.E-01 1 1.E-01

Th-229 2.E-02 1 2.E-02 Th-229 3.E-02 0.1 3.E-01

Th-230 2.E-01 1 2.E-01 Th-230 2.E-01 0.1 2.E+00

Pa-231 4.E-02 1 4.E-02 Pa-231 6.E-02 0.1 6.E-01

Th-231 7.E+02 - - Th-231 8.E+02 - -

Th-232 3.E-02 1 3.E-02 Th-232 5.E-02 0.1 5.E-01

Pa-233 8.E-01 - - Pa-233 9.E-01 -

U-233 3.E-01 1 3.E-01 U-233 4.E-01 1 4.E-01

Th-234 1.E+01 - - Th-234 2.E+01 - -

U-234 3.E-01 1 3.E-01 U-234 4.E-01 1 4.E-01

U-235 3.E-01 1 3.E-01 U-235 4.E-01 1 4.E-01

Np-237 5.E-03 1 5.E-03 Np-237 7.E-03 0.1 7.E-02

Pu-238 1.E-01 1 1.E-01 Pu-238 2.E-01 0.1 2.E+00

U-238 3.E-01 1 3.E-01 U-238 4.E-01 1 4.E-01

Pu-239 1.E-01 1 1.E-01 Pu-239 2.E-01 0.1 2.E+00

Pu-240 1.E-01 1 1.E-01 Pu-240 2.E-01 0.1 2.E+00

Pu-241 8.E+00 10 8.E-01 Pu-241 1.E+01 10 1.E+00

Am-241 9.E-02 1 9.E-02 Am-241 1.E-01 0.1 1.E+00

Cm-242 2.E+00 10 2.E-01 Cm-242 3.E+00 1 3.E+00

Pu-242 1.E-01 1 1.E-01 Pu-242 2.E-01 0.1 2.E+00

Cm-244 2.E-01 1 2.E-01 Cm-244 2.E-01 0.1 2.E+00

The draft IAEA clearance levels were developed using an approach that is different from the one

presented in this report. Rather than evaluate a set of scenarios representing specific industry

practices, the IAEA reviewed several IAEA and other studies that included a variety of scenarios,

materials, and radionuclides. In the IAEA approach, radionuclides were sorted into bins
Section 2 Summary and Comparison of Results

2-17 NUREG-1640

representing orders of magnitude of the clearance levels. The logarithmic midpoint of each bin is

treated as the single value of the clearance level for all radionuclides in each bin.

The IAEA clearance levels address both volumetrically and surficially distributed contamination. 

The surficial clearance levels are based on a comparative review of mass contamination and

surface contamination studies. Based on this review, the IAEA chose to set surficial clearance

levels in units of Bq/cm2 at the same numerical value as the mass-based clearance levels in Bq/g. 

This is equivalent to assuming that all materials have a surface-to-mass ratio of 1 cm 2/g. As

with the EC, clearance levels are based on an annual individual dose criterion of 10 μSv/y.

Table 2.6 compares the results in this analysis to the draft IAEA clearance levels for the 48

radionuclides they have in common. The IAEA clearance levels were taken from Table I of

IAEA (1996).

The NRC clearance levels in Table 2.6 are the results of this analysis expressed in units of Bq/g

or Bq/cm2

, as appropriate. Mass-based clearance levels were calculated from the dose factors in

Table 2.1 and surficial clearance levels were calculated form the dose factors in Table 2.2 of this

report. In each case, the most restrictive dose factor among the four materials analyzed was used

for each radionuclide, because the IAEA clearance levels are intended to be applied to all solid

materials. Equation 2.2 was used to calculate a clearance level for comparison with the IAEA

values.

The ratio of NRC derived clearance levels to IAEA clearance levels shows a degree of agreement

that is similar to that for the EC values. Where this ratio is plus-or-minus an order of magnitude

(0.1 to 10) the two sets of criteria can be considered in general agreement. For both mass-based

and surficial clearance levels, where the ratio is greater than 1.0 the NRC values indicate a

clearance level that is less restrictive than the EC values. Where the ratio is less than 1.0 the

NRC values are more restrictive. Similar to the EC comparison, for those radionuclides where

the ratio is greater than a factor of 10 different, the derived clearance levels in this analysis are

more restrictive for all radionuclides except one (Fe-55).
Summary and Comparison of Results Section 2

NUREG-1640 2-18

Table 2.6 Comparison of derived NRC clearance levels with IAEA values (all materials)

Mass clearance levels Surficial clearance levels

NRC IAEA Ratio NRC IAEA Ratio

Radionuclide (Bq/g) (Bq/g) NRC / IAEA Radionuclide (Bq/cm2

) (Bq/cm2) NRC / IAEA

H-3 1.1E+03 3000 4.E-01 H-3 2.1E+04 3000 7.E+00

C-14 6.3E-01 300 2.E-03 C-14 2.7E+01 300 9.E-02

Na-22 2.4E-02 - - Na-22 3.2E-02 - -

P-32 7.3E+01 300 2.E-01 P-32 9.0E+01 300 3.E-01

S-35 1.3E+03 3000 4.E-01 S-35 1.8E+03 3000 6.E-01

Cl-36 6.3E-02 300 2.E-04 Cl-36 3.1E+00 300 1.E-02

K-40 1.9E-01 - - K-40 2.5E-01 - -

Ca-41 2.1E+00 - - Ca-41 8.5E+01 - -

Ca-45 1.2E+02 3000 4.E-02 Ca-45 1.6E+02 3000 5.E-02

Cr-51 4.0E+00 30 1.E-01 Cr-51 4.7E+00 30 2.E-01

Mn-54 1.2E-01 0.3 4.E-01 Mn-54 1.4E-01 0.3 5.E-01

Fe-55 2.9E+03 300 1.E+01 Fe-55 1.2E+04 300 4.E+01

Co-57 1.5E+00 30 5.E-02 Co-57 3.1E+00 30 1.E-01

Co-58 1.0E-01 3 3.E-02 Co-58 1.2E-01 3 4.E-02

Fe-59 8.6E-02 3 3.E-02 Fe-59 1.0E-01 3 3.E-02

Ni-59 1.4E+03 - - Ni-59 2.8E+04 - -

Co-60 3.9E-02 0.3 1.E-01 Co-60 4.6E-02 0.3 2.E-01

Ni-63 1.0E+03 3000 3.E-01 Ni-63 1.0E+04 3000 3.E+00

Zn-65 4.7E-02 0.3 2.E-01 Zn-65 6.2E-02 0.3 2.E-01

Cu-67 3.5E+00 - - Cu-67 5.7E+00 - -

Se-75 2.8E-01 - - Se-75 3.8E-01 - -

Sr-85 2.1E-01 - - Sr-85 2.5E-01 - -

Sr-89 7.0E+01 300 2.E-01 Sr-89 1.0E+02 300 3.E-01

Sr-90 9.8E-01 3 3.E-01 Sr-90 1.3E+00 3 4.E-01

Y-91 2.3E+01 - - Y-91 3.4E+01 - -

Mo-93 2.6E-01 - - Mo-93 1.2E+01 - -

Nb-93m 4.9E+02 - - Nb-93m 1.6E+03 - -

Nb-94 3.4E-02 0.3 1.E-01 Nb-94 7.2E-02 0.3 2.E-01

Nb-95 1.4E-01 - - Nb-95 1.6E-01 - -

Zr-95 1.4E-01 - - Zr-95 1.6E-01 - -

Tc-99 8.4E-02 300 3.E-04 Tc-99 3.9E+00 300 1.E-02

Ru-103 2.1E-01 - - Ru-103 2.5E-01 - -

Ru-106 4.8E-01 3 2.E-01 Ru-106 5.7E-01 3 2.E-01

Ag-108m 5.8E-02 - - Ag-108m 7.2E-02 - -

Cd-109 2.3E+01 300 8.E-02 Cd-109 3.1E+01 300 1.E-01

Ag-110m 3.5E-02 0.3 1.E-01 Ag-110m 4.1E-02 0.3 1.E-01

Sb-124 5.5E-02 0.3 2.E-01 Sb-124 6.5E-02 0.3 2.E-01

I-125 3.7E+00 30 1.E-01 I-125 4.7E+00 30 2.E-01

Sb-125 2.5E-01 - - Sb-125 2.9E-01 - -

I-129 4.2E-03 30 1.E-04 I-129 2.0E-01 30 7.E-03

I-131 3.6E-01 3 1.E-01 I-131 4.7E-01 3 2.E-01

Ba-133 3.6E-01 - - Ba-133 4.2E-01 - -

Cs-134 1.5E-02 0.3 5.E-02 Cs-134 2.0E-02 0.3 7.E-02

Cs-137 3.9E-02 0.3 1.E-01 Cs-137 5.1E-02 0.3 2.E-01

Ce-141 2.9E+00 - - Ce-141 4.3E+00 - -

Ce-144 3.0E+00 30 1.E-01 Ce-144 3.6E+00 30 1.E-01

Pm-147 3.6E+02 3000 1.E-01 Pm-147 1.2E+03 3000 4.E-01

Eu-152 9.0E-02 0.3 3.E-01 Eu-152 1.1E-01 0.3 4.E-01
Section 2 Summary and Comparison of Results

Table 2.6 Comparison of derived NRC clearance levels with IAEA values (all materials)

Mass clearance levels Surficial clearance levels

NRC IAEA Ratio NRC IAEA Ratio

Radionuclide (Bq/g) (Bq/g) NRC / IAEA Radionuclide (Bq/cm2

) (Bq/cm2) NRC / IAEA

2-19 NUREG-1640

Eu-154 8.2E-02 - - Eu-154 9.6E-02 - -

Eu-155 4.1E+00 - - Eu-155 1.1E+01 - -

Re-186 3.3E+01 - - Re-186 4.8E+01 - -

Ir-192 8.4E-02 3 3.E-02 Ir-192 1.1E-01 3 4.E-02

Pb-210 6.5E-02 0.3 2.E-01 Pb-210 8.7E-02 0.3 3.E-01

Po-210 1.7E-01 3 6.E-02 Po-210 2.3E-01 3 8.E-02

Bi-210 1.0E+02 - - Bi-210 3.8E+02 - -

Rn-222 9.5E-02 - - Rn-222 1.4E-01 - -

Ra-223 5.2E-01 - - Ra-223 6.5E-01 - -

Ra-224 1.3E-01 - - Ra-224 1.9E-01 - -

Ac-225 6.5E-01 - - Ac-225 8.3E-01 - -

Ra-225 1.9E+00 - - Ra-225 7.3E+00 - -

Ra-226 1.9E-02 0.3 6.E-02 Ra-226 6.7E-02 0.3 2.E-01

Ac-227 1.2E-02 - - Ac-227 3.9E-02 - -

Th-227 9.0E-01 - - Th-227 2.0E+00 - -

Th-228 3.7E-02 0.3 1.E-01 Th-228 9.2E-02 0.3 3.E-01

Ra-228 1.1E-01 0.3 4.E-01 Ra-228 1.4E-01 0.3 5.E-01

Th-229 7.4E-03 - - Th-229 3.1E-02 - -

Th-230 4.5E-02 0.3 2.E-01 Th-230 2.0E-01 0.3 7.E-01

Pa-231 4.8E-03 - - Pa-231 5.9E-02 - -

Th-231 2.5E+02 - - Th-231 7.9E+02 - -

Th-232 7.6E-03 0.3 3.E-02 Th-232 4.6E-02 0.3 2.E-01

Pa-233 7.4E-01 - - Pa-233 8.9E-01 - -

U-233 6.0E-02 - - U-233 3.9E-01 - -

Th-234 1.3E+01 - - Th-234 1.6E+01 - -

U-234 6.0E-02 0.3 2.E-01 U-234 4.0E-01 0.3 1.E+00

U-235 7.1E-02 0.3 2.E-01 U-235 4.1E-01 0.3 1.E+00

Np-237 1.4E-04 0.3 5.E-04 Np-237 7.0E-03 0.3 2.E-02

Pu-238 5.8E-02 - - Pu-238 1.8E-01 - -

U-238 7.7E-02 0.3 3.E-01 U-238 4.5E-01 0.3 1.E+00

Pu-239 4.5E-02 0.3 1.E-01 Pu-239 1.7E-01 0.3 6.E-01

Pu-240 4.5E-02 0.3 2.E-01 Pu-240 1.7E-01 0.3 6.E-01

Pu-241 5.8E-01 30 2.E-02 Pu-241 1.1E+01 30 4.E-01

Am-241 3.0E-02 0.3 1.E-01 Am-241 1.2E-01 0.3 4.E-01

Cm-242 9.4E-01 - - Cm-242 3.1E+00 - -

Pu-242 4.7E-02 - - Pu-242 1.8E-01 - -

Cm-244 6.4E-02 0.3 2.E-01 Cm-244 2.1E-01 0.3 7.E-01
Section 3 Evaluation of Direct Reuse of Equipment

3-1 NUREG-1640

An analysis of the direct reuse of cleared equipment is presented. This analysis differs from recycle

scenarios in three ways: (1) surficial contamination is assumed, rather than volumetric, (2) there is no

processing of the equipment prior to use, and (3) the analysis is independent of equipment material.

A single scenario involving the driver of a cleared truck was analyzed, as this scenario was

determined to bound all other equipment reuse scenarios. The evaluation resulted in realistic

estimates of radionuclide-specific dose factors for an average member of the exposed group. The

analysis was conducted on a probabilistic basis, and the mean of the dose factor distribution was

selected to represent the dose to an average member of the exposed group.

Mean dose factors range from a high of 1.7E+02 μSv/y per Bq/cm2 (0.6 mrem/y per pCi/cm2 ) for Th229 to a low of 1E-05 μSv/y per Bq/cm2 (4E-08 mrem/y per pCi/cm2 ) for H-3. The high mean dose

factor of Th-229 (and also Ac-227 and Th-232) is attributed to the inhalation exposure pathway and a

relatively high inhalation dose conversion factor. Other high reuse scenario mean dose factors (e.g.,

for Co-60 and Ag-110m) result from the external exposure pathway. Approximately one-third of the

mean dose factors are greater than 10 μSv/y per Bq/cm2 (0.04 mrem/y per pCi/cm2 ), one-third are

between 0.01–10 μSv/y per Bq/cm2 (4E-05–0.04 mrem/y per pCi/cm2 ), and the remaining one-third

are less than 0.01 μSv/y per Bq/cm2 (4E-05 mrem/y per pCi/cm2 ). These equipment reuse dose

factors are less restrictive than comparable recycle dose factors described later in the report.

(9$/8$7,212)',5(&75(86(2)(48,30(17

The purpose of this section is to present an evaluation of the limiting dose consequences of

immediate reuse of cleared equipment with residual radioactivity on its surface (direct reuse of

equipment). As with recycle, direct reuse of equipment could result in an infinite number of

exposure scenarios, from the reuse of items as small as hand tools, to very large items such as

trucks or other vehicles. Reuse could also involve the one-time use of a piece of equipment for a

very short duration, or long-term use for a year or more. Scenarios involving reuse of land or a

building are outside the scope of this evaluation, as they are addressed elsewhere (i.e.,

NUREG/CR-5512 [Kennedy and Strenge 1992] or NUREG-1500 [NRC 1994b]). 

The analysis of equipment reuse differs from the analysis of recycle (Section 4) primarily in three

respects: surficial contamination is assumed, rather than volumetric; there is no processing of the

equipment after clearance from the licensed facility; and the analysis is independent of equipment

material. Also, the goal of the equipment reuse scenario analysis is different than that of the

recycle analyses described in later sections of this report. The goal of the reuse scenario analysis

is to realistically analyze a bounding scenario for reuse of cleared equipment. Thus the

conceptual setting of the reuse exposure situation represents conditions of reuse that are judged

to be bounding for all equipment reuse scenarios, however the parameter values used to analyze

the scenario are realistically chosen. 

The following sections contain a description of equipment reuse scenarios, including the

bounding scenario analyzed. This includes a description of the exposure pathways included in

the bounding scenario evaluation and the equations used to analyze the doses for the scenario. 

Finally, a discussion of the probabilistic parameter values used in the evaluation, a listing of
Evaluation of Direct Reuse of Equipment Section 3

NUREG-1640 3-2

selected results from the distribution of dose factors from the equipment reuse scenario analysis,

and a comparison of those results to the recycle analysis results are included. 

'LUHFW5HXVH6FHQDULR'HVFULSWLRQ

In order to address the possible range of unrestricted reuse scenarios, the types of items likely to

be reused were identified. These items fall into the following categories:

• small hand tools and other hand-held items such as drills, saws, and buffers

• electrical items such as motors, pumps, and generators

• office equipment (although these items should not be contaminated)

• construction equipment such as scaffolding, noise or dust-control barriers, wheelbarrows

• large equipment such as trucks and other vehicles.

An initial qualitative screening resulted in the judgment that work related use of a reused item

would result in much longer potential durations of exposure, with other factors being the same,

as for home or residential reuse. Home use of an item from the laboratory or industrial setting of

a Nuclear Regulatory Commission (NRC) licensee would likely be for an intermittent or short

duration, as opposed to the possible full-day, work-related reuse of an item, over a period of time

equivalent to a full workyear. Therefore, work-related settings were emphasized. 

It is likely that equipment that is cleared for direct reuse will contain surficial contamination

rather than volumetric contamination, thus, only surficial contamination reuse scenarios were

analyzed. In screening analyses conducted for this assessment, two scenarios involving reuse of

equipment containing surficial contamination were analyzed in detail. Of these two scenarios,

only the scenario resulting in consistently higher dose factors for all radionuclides is included in

this report. This scenario was developed to represent the critical group scenario for all potential

scenarios involving surficial contamination, including hand tools and other equipment. The

critical group scenario consists of the reuse of a large piece of equipment (a truck). This

bounding scenario is the reuse scenario discussed in the remainder of this section.

The critical group in this scenario is the group of individuals that drive trucks that have been

cleared from NRC licensed facilities. The individual receptor in the reuse scenario is a truck

driver. This individual is exposed externally to radiation from residual radioactivity on the inside

of the truck cab, as well as internally to contamination resuspended from the surface and to

inadvertent ingestion of surface radioactivity. The dose measure is the total effective dose

equivalent (TEDE), which is defined in 10CFR20.1003 as the sum of the (external) deep-dose

equivalent and the (internal) committed effective dose equivalent (EDE). 

Based on assumed good health physics practices at NRC licensed facilities, removable surface

contamination has been removed during decontamination procedures prior to final survey and

clearance. Furthermore, to simplify the analysis, it is assumed that the residual surface

radioactivity is uniformly distributed on the interior surface of the truck cab. 
Section 3 Evaluation of Direct Reuse of Equipment

3-3 NUREG-1640

&VF ' &[VF H

&UW

V 3.1 

There are three exposure pathways included in the evaluation of the reuse scenario: external

radiation exposure, inhalation exposure, and secondary ingestion exposure. External exposure to

penetrating radiation would result from radionuclides on the inside surface of the truck cab. The

inhalation pathway is included because a worker inside the truck cab could inhale contamination

that has been resuspended into the air. This resuspension could either be caused by air flowing

through the cab of the truck or other mechanical disturbance of residual surface radioactivity. 

The third exposure pathway is secondary ingestion. Secondary ingestion refers to the ingestion

of removable residual surface radioactivity inside the truck cab after transfer to hands, food, or

other items entering the mouth. Even more than inhalation of resuspended contamination,

secondary ingestion is a poorly defined pathway that is not easily calculated by a detailed

description of the mechanisms involved. The dose from this exposure pathway is calculated

using an approach similar to the inhalation pathway, where the residual surface radioactivity is

related to intake by means of a lumped parameter that accounts for the combined effects of

several poorly understood processes. The lumped parameter represents the effective transfer rate,

which is a parameter that estimates the area of contamination that is ingested per hour (in units of

area/time). 

([SRVXUH3DWKZD\V

The modeled concentration of radioactive material on the surface of the truck cab is a unit

concentration (1 pCi/cm2) at the time of clearance from the nuclear facility. The following

equations were evaluated separately for each radionuclide in the analysis. Therefore, parameters

such as concentration, decay factors, decay constants, and dose conversion factors are not

explicitly subscripted for each radionuclide.

The surface concentration at the time the reuse begins is calculated by Equation 3.1. This

concentration is slightly less than the unit concentration assumed at the time of clearance.

where

C0,sc = surface concentration on the reused item at the time the scenario begins (pCi/cm2

)

and

Cx,sc = surface concentration on the reused item at the time of clearance (pCi/cm2

)

r = radioactive decay constant (d-1)

ts = delay time from clearance of item from nuclear facility to time scenario begins (d)

The annual dose for the reuse scenario is calculated for the 1-year period immediately following

clearance and the short delay time, ts. The bounding reuse scenario involves the use of a single

truck over an entire 1-year period, so radioactive decay over that period is appropriate to

incorporate. This is done by the use of a decay factor that consists of the integrated decay over

the time from beginning to end of use, as shown in Equation 3.2.
Evaluation of Direct Reuse of Equipment Section 3

NUREG-1640 3-4

DK ' 1 & e & 8r tu

8r t

u

3.2

'H[W ' &VF ( *)( W

[V ( W\V ( '. 3.3 

'LQK ' &VF ( 5)VF ( %5 ( ')LQK ( W

[V ( W\V ( '. ( (% 3.4 

where

DK = decay factor for radioactive decay over period of reuse (unitless)

and

r = radioactive decay constant (d-1)

tu = duration of use of item (d)

The decay factor is applied to each pathway dose in Equations 3.3, 3.4, and 3.5; each pathway

dose is multiplied by the decay factor. The TEDE for the scenario is then calculated by the

addition of the decay-corrected doses from the external, inhalation, and secondary ingestion

exposure pathways. The mathematical equations for calculating the doses for each of the three

exposure pathways in this scenario are discussed in the following three subsections.

([WHUQDO([SRVXUH

The dose from external exposure to penetrating radiation from residual surface radioactivity is

calculated using Equation 3.3.

where

Dext = EDE due to external exposure (mrem/y)

and

C0,sc = surface concentration on the reused item at the time the scenario begins (pCi/cm2

)

GF = geometry factor for the scenario (mrem/h per pCi/cm2

)

txs = daily number of hours of exposure for the scenario (h/d)

tys = annual number of days of exposure for the scenario (d/y)

DK = decay factor for radioactive decay over period of reuse (unitless)

,QKDODWLRQ([SRVXUH

The dose due to the inhalation of resuspended residual surface radioactivity is calculated using

Equation 3.4.

where

Dinh = EDE due to inhalation (mrem/y)

and

C0,sc = surface concentration on the reused item at the time the scenario begins (pCi/cm2

)

RFsc = resuspension factor for residual surface radioactivity (cm-1)

BR = breathing rate for moderate physical activity (m3

/h)

DFinh = inhalation dose factor (mrem/pCi intake)

txs = daily number of hours of exposure for the scenario (h/d)
Section 3 Evaluation of Direct Reuse of Equipment

3-5 NUREG-1640

'LQJ ' &VF ( ,5VF ( ')LQJ ( W

[V ( W\V ( '. 3.5 

'7 ' 'H[W % 'LQK%'LQJ 3.6 

tys = annual number of days of exposure for the scenario (d/y)

DK = decay factor for radioactive decay over period of reuse (unitless)

1E+06 = unit conversion factor (cm3

/m3)

6HFRQGDU\,QJHVWLRQ([SRVXUH

The dose due to secondary ingestion of removable residual surface radioactivity inside the truck

cab after transfer to hands, food, or other items entering the mouth is calculated using

Equation 3.5

where

Ding = EDE due to secondary ingestion (mrem/y)

and

C0,sc = surface concentration on the reused item at the time the scenario begins (pCi/cm2

)

IRsc = effective transfer rate for ingestion of residual surface radioactivity (cm2

/h)

DFing = ingestion dose factor (mrem/pCi intake)

txs = daily number of hours of exposure for the scenario (h/d)

tys = annual number of days of exposure for the scenario (d/y)

DK = decay factor for radioactive decay over period of reuse (unitless)

7RWDO'RVHIURP(TXLSPHQW5HXVH

The total dose from the reuse scenario is the sum of the three exposure pathway doses (external,

inhalation, and secondary ingestion). This is calculated using Equation 3.6

Where

DT = TEDE for the Scenario

and Dext = EDE due to external exposure (mrem/y)

Dinh = EDE due to inhalation (mrem/y)

Ding = EDE due to secondary ingestion (mrem/y)

'LVFXVVLRQRI0RGHOVDQG3DUDPHWHU9DOXHV

This section provides a basis for choosing values for key parameter values and distributions used

in this analysis. The equipment reuse scenario was analyzed probabilistically, resulting in a

distribution of dose factors for each radionuclide. 

Values for the decay factor, DK, were calculated by integrating the radioactive decay over a

period of 1 year, which is the duration of use of the reused item, tu. Values for each radioactive

decay constant, r, used in the calculation were taken from Federal Guidance Report 11 (EPA

1988). All equipment that is cleared and reused is assumed to be initially taken to a distribution
Evaluation of Direct Reuse of Equipment Section 3

NUREG-1640 3-6

center (e.g., surplus equipment broker). A time period of 4 days for handling and transport of the

material prior to reuse is assumed, as well as an additional 7 day storage period at the distribution

center (see Section 4). Thus, a value of 11 d (I 50%) is used for ts. Finally, a range of 1 h/d to 8

h/d was used for txs, a fixed value of 250 d/y is used for tys, for both the external and internal

exposure pathways.

The other parameters used are each unique to a given exposure pathway, so the remainder of the

discussion is arranged by exposure pathway. 

([WHUQDO3DWKZD\

External dose models typically use generic geometrical shapes (e.g., discs, cylinders, and

spheres) to represent a variety of potential items (e.g., O’Donnell et al. 1978, IAEA 1992, Chen

1993). Radionuclide-specific values for the geometry factor (GF) used for the external exposure

pathway evaluation are based on shielding calculations using the computer code MCNP. Values

are listed in Appendix C (GF #12). The GF values were calculated assuming the residual surface

radioactivity is on the inside surface of a hollow sphere, with the receptor at the center of the

sphere. External geometry factors include the dose contributions of progeny as described in

Appendix E. 

This analysis uses a hollow sphere to represent a vehicle. In this geometry, the receptor is inside

the sphere and all the residual radioactivity is assumed to be on the inside surface of the sphere. 

The external geometry factors used in this evaluation do not include potential dose contributions

from beta particles. This could be a nonconservative aspect of the external dose for some

radionuclides, as it is conceivable that the driver of a truck with interior residual surface

radioactivity could receive a skin dose from beta particles emitted from some radionuclides. 

However, this dose contribution would likely be insignificant for most radionuclides and very

small, even for the radionuclides with the most energetic beta emissions. This is largely because

in order to receive a significant skin dose to the most likely exposed part of the body (hands), the

hands of the driver in this scenario would have to be in contact with the contaminated surface for

a significant length of time. The steering wheel of the truck is the only potentially contaminated

surface of the truck cab that a driver’s hands would be in contact with for more than a very brief

time. 

,QKDODWLRQ3DWKZD\

The inhalation dose model used in this study is essentially the same as that used in several other

similar studies (IAEA 1970, IAEA 1992, Kennedy and Strenge 1992, Chen 1993). An exception

is one of the earliest recycle assessments (O’Donnell et al. 1978), which did not include

resuspension of residual surface radioactivity as an exposure pathway. 
Section 3 Evaluation of Direct Reuse of Equipment

3-7 NUREG-1640

Table 3.1 Representative reported indoor resuspension data and recommended values

Reference Resuspension factor or range Comments

Barnes (1959) 4E-5 m-1 (confined space)

2E-6 m-1 (open air)

Reported for “dusty operations”; 10-5 m-1

recommended for most laboratory work.

Stewart (1964) 1E-6 m-1 (quiescent conditions)

1E-5–1E-4 m-1 (“operational”

conditions)

Notes that excessively high particulate resuspension

values indoors are likely to indicate some degree of

inefficiency in the ventilation system.

Brunskill (1964) 2E-4–4E-3 m-1 Measured in small rooms with various types of

personnel movement, including introduction of

loose contamination on coveralls. Lower

recommended values were measured for a large area

of “loose” contamination on concrete; “much

smaller” values were found for linoleum floor.

Jones and Pond

(1964)

2E-8–5E-5 m-1

5E-5 m-1 (recommended for worst

practical conditions)

Estimated that 10–20% of total airborne

radioactivity was respirable. Suggested that

recommended value could be an order of magnitude

lower for average conditions.

Dunster (1964) 2E-6–4E-5 m-1

2E-6 m-1 (recommended safe value for

long-term use)

Highest values from digging through dusty building

rubble and in an enclosed and unventilated space.

Spangler and Willis

(1964)

4E-5 m-1 (derived) This value is calculated using equation for

equilibrium airborne concentration in a small room

from a surface concentration and recommended

values appropriate for calculating 40 hr maximum

permissible concentration (MPC) levels.

Healy (1971) 2.1 E-7–1.0 E-3 m-1(derived) This value is calculated using the equation for

airborne concentration, assuming ventilation rate for

a reasonably tight 28 m2

×2.4 m room.

Gibson and

Wrixom (1979)

2E-6–4E-5 m-1 The lower value was used in original calculation of

derived working limits (DWL) for active area

surfaces and might be inappropriate for widespread

contamination on dusty surfaces. The higher value

was obtained from measurements in a confined

space and is suggested for general use.

IAEA (1970) 2E-6–3E-3 m-1

5E-5 m-1 (recommended)

Recommended value is suggested as appropriate for

general conditions of contamination on surfaces. 

Because of confounding factors, this effectively

reduces the recommended value by 2.5× for use in

calculating DWL values.

Kennedy et al.

(1981)

2.5E-5 m-1 (derived) This value is calculated using the equation for

airborne concentration, assuming ventilation rate of

an open transport truck and resuspension rate for a

28 m2

 room.

Kennedy and

Strenge (1992)

1E-6 m-1 (recommended) Based on a review of resuspension literature. 

Recommended as a reasonably conservative default

value to be applied to total surface concentration.

IAEA (1992) 1E-6 m-1 (recommended) This value is recommended for use in assessing

reuse of tools and equipment. Used a transfer factor

of 0.01 to account for the fraction of the residual

surface radioactivity that is available for

resuspension.

Chen (1993) 1 E-6 m-1 No justification given (based on use in Kennedy and

Strenge 1992)
Evaluation of Direct Reuse of Equipment Section 3

NUREG-1640 3-8

5)VF ' 

 ' I $9 Q 3.7 

Values for the inhalation dose conversion factors, DFinh, are taken from Federal Guidance Report

11 (EPA 1988). Where more than one inhalation dose conversion factor is listed for a

radionuclide in Federal Guidance Report 11, the largest value was selected. Inhalation dose

conversion factors shown in Appendix B have been modified to include the dose contributions of

progeny as described in Appendix E.

The resuspension factor, RFsc, is the most poorly known parameter in the inhalation pathway

analysis. Based on a literature review, information presented in previous evaluations, and the

following discussion, a lognormal distribution with a geometric mean of 1E-10 cm-1 (1E-08 m-1)

is used for the resuspension factor for residual surface radioactivity. This value is at the low end

of measured values. The low value is appropriate for this scenario, which includes the

assumption that surfaces have been cleaned of easily removable, and most readily resuspendable,

contamination at the time of clearance from regulatory control. 

The resuspension of radioactive material from surfaces is typically modeled by the use of an

equilibrium resuspension factor (in units of length-1) or a fractional resuspension rate (in units of

time-1). The resuspension factor is simply a ratio of the air concentration of radioactive material

above a surface (pCi/cm3

) to the concentration on the surface (pCi/cm2). Although the theoretical

inadequacies of both the resuspension factor and the resuspension rate have been discussed in the

literature (e.g., Healy 1971, Horst 1982), both are commonly used in modeling assessments

because more technically defensible approaches are lacking. The resuspension factor and the

resuspension rate can be related by Equation 3.7

Where

RFsc = resuspension factor (cm-1)

= air concentration (pCi/cm3)

= residual surface radioactivity level (pCi/cm2)

f = resuspension rate (h-1)

A = area of the source of residual surface radioactivity (cm2

)

V = volume of air in the room (cm3

)

n = rate of room air exchange (h-1)

Measured resuspension factors and rates can vary over very wide ranges (resuspension factors

from approximately 1E-11 to 1E-2 m-1 [Kennedy and Strenge 1992] and resuspension rates from

approximately 1E-7 to 1E-2 hr-1 [Healy 1971]), which suggests that resuspension is a complex

process of several parameters, and that the specific conditions present at the time of measurement

are critical. For modeling purposes, a resuspension factor or rate is a lumped parameter that is

used to account for a complex combination of mechanisms that are poorly understood, but whose

net effect is observed in the real world. 

A resuspension factor rather than a resuspension rate is used in this evaluation, although neither

is better known than the other, and neither is obviously more appropriate to the reuse scenario. 

The use of a resuspension rate would require additional parameters in Equation 3.4, and would,

in turn introduce additional values and their associated uncertainties. The resuspension factor
Section 3 Evaluation of Direct Reuse of Equipment

3-9 NUREG-1640

value used in this study 1E-10 cm-1 (1E -8 m-1) is based on a review of relevant literature data,

combined with professional judgement and taking into account the application in this specific

scenario. Unfortunately, there are no experimental data that specifically address resuspension

from tools or equipment. The experimental data and recommendations summarized in Table 3.1

are felt to be the most appropriate available information. The range of resuspension factors cited

in Table 3.1 is 2 E-8 m-1 to 4 E-3 m-1. The reported data are generally from experiments that

examined resuspension of liquid or powder contaminated material that had been uniformly

applied to clean surfaces in a laboratory-like setting. The highest values are typically associated

with inefficient ventilation, excessive mechanical disturbance, or dusty conditions. Typically,

the purpose of these studies was to help determine radiation protection safety guidelines for loose

residual, surface radioactivity. Although this situation is not the same as assumed for the reuse

scenario, it is reasonable to use the lowest value of the resuspension factors cited in the studies,

rounded to the nearest order of magnitude. 

Using the lowest value as a geometric mean for this assessment is appropriate because of two key

assumptions inherent in the scenario definition: (1) readily removable contamination has been

removed from the surface of the truck cab prior to clearance, and (2) contamination that is not

readily removable is the least susceptible to resuspension. This situation represents a key

difference between this scenario and the conditions for which resuspension measurements have

typically been taken. 

The use of a mean resuspension factor near the lowest measured value is also justified based on

consideration of the respirable fraction of resuspended contamination. In one of the few studies

where particle size has been measured, Jones and Pond (1964) reported that measurements of air

concentration were often biased by a few highly active large particles. In their study on

resuspension of plutonium, they concluded that only 10%–20% of the total airborne radioactivity

would be respirable. Rather than include a respirable fraction parameter and attempt to define it

without a sound basis, the reuse scenario analysis assumes that all resuspended contamination is

respirable. Although this assumption would result in overestimating the dose from inhalation,

the effect is offset by using the lowest cited value for the parameter RFsc. The resulting Dinh value

is still considered conservative.

Another complicating factor is that the residual surface radioactivity is probably not uniform. 

Several studies (Dunster 1964, IAEA 1970, Healy 1971) discuss how this issue relates to

resuspension values. Healy (1971) points out that in most cases, resuspension has been measured

for uniformly contaminated surfaces and uniformly applied resuspension forces. Healy suggests

that air concentrations are more strongly related to the total amount of surface contamination

present, rather than the amount on any one limited area, and that basing allowable surface

contamination limits on the highest surface levels may be too conservative. 
Evaluation of Direct Reuse of Equipment Section 3

NUREG-1640 3-10

The influence of ventilation is also a key factor that would likely result in a resuspension factor at

the low end of measured values. The potential for excessive ventilation in a truck cab from open

windows, air conditioning, and repeatedly opening doors would tend to reduce airborne

concentrations of resuspended material via dilution and air exchange. Although increased

airflow may also act to increase resuspension, this is likely a second-order effect when compared

to dilution and resulting lower air concentrations (Healy 1971).

There are many other factors that contribute to the uncertainty in resuspension that are not

addressed here because of lack of information. These include temperature, humidity, type and

roughness of surface material, degree and effectiveness of mechanical disturbance, weathering

processes, and chemical state of the contamination. The effect of changes in many of these

factors on resuspended air concentration is intuitive (e.g., an increase in the size of the

contaminated area would likely result in an increase in the resuspended air concentration),

however, the degree and direction of the effect of other factors (e.g., specific surface conditions)

is not so clear. Combining all these factors to define a “generic” resuspension factor or rate for

modeling purposes is difficult. Based on a consideration of these factors and good engineering

judgement, however, it is reasonable to use a lognormal distribution with geometric mean of the

lowest reported resuspension factor in the model.

In an interesting review of measured resuspension factors, Brodsky (1980) concluded that the

fractional amount of contamination on 1 m2

 of floor or ground that would enter 1 m3 of air and be

respirable by an individual over an extended period of time would be less than 10-6 and usually

would be much lower. As a check of the methodology of this analysis against Brodsky’s

conclusion, an annual inhaled fraction of 2 E-6 can be derived for this reuse scenario, using

parameters from Equation 3.4 and the appropriate mean parameter values. This fraction is

consistent with Brodsky's estimate, which adds a degree of confidence that the model and

parameter values used do not substantially underestimate or overestimate the resuspension factor.

Finally, the resuspension factor has not been consistently applied in previous evaluations. The

resuspension factor in Kennedy et al. (1981) and Chen (1993) was applied to contamination that

was assumed to be removable, whereas the rate in Kennedy and Strenge (1992) is intended to be

applied to the total residual surface radioactivity present. The IAEA (1992) also intended for the

resuspension factor to be applied to the total contamination present, however, the removability of

the contamination was addressed by incorporating a transfer factor of 0.01. The resuspension

factor in this evaluation of the reuse of a large piece of equipment is intended to be applied to the

total contamination present at the time of clearance for reuse, because for a generic application,

the full range of removable fraction must be assumed to be encountered. In addition,

measurement of removable residual surface radioactivity is highly variable and uncertain

(Royster and Fish 1964, IAEA 1970).
Section 3 Evaluation of Direct Reuse of Equipment

3-11 NUREG-1640

6HFRQGDU\,QJHVWLRQ

Values for the ingestion dose conversion factor, DFing, are taken from Federal Guidance Report

11 (EPA 1988). Where more than one ingestion dose conversion factor is listed for a

radionuclide in Federal Guidance Report 11, the largest value was selected. Ingestion dose

conversion factors shown in Appendix B have been modified to include the dose contributions of

progeny as described in Appendix E. 

A lognormal distribution is used for the effective transfer rate for ingestion with a geometric

mean of 1E-4 cm2/h. This value was estimated for this scenario using the alternative methods

described below. It is lower than the value used in previous reuse evaluations (1 cm2/hr) (e.g.,

Kennedy and Strenge 1992, and IAEA 1992), however it is judged to be appropriate for this

reuse scenario. 

The secondary ingestion model used in this study is essentially the same as that used in previous

similar evaluations (Kennedy and Strenge 1992, IAEA 1992). As a review of the literature

reveals, there are no data available on secondary ingestion of radioactive material from residual

surface radioactivity. Consequently, most relevant evaluations over the past 30 years have made

basically the same assumption: the amount of loose contamination on approximately 1 cm2

 of

surface area would be ingested per hour (Dunster 1964, IAEA 1970, Healy 1971, Gibson and

Wrixon 1979, Kennedy and Strenge 1992, IAEA 1992). Kennedy et al. (1981) modified the

ingestion value to account for the specific scenario being addressed, and the IAEA (1992)

applied a transfer factor of 0.01 to the ingestion value, although there was no basis provided for

the value used.

Using a value of 1 cm2

/hr as a best estimate for the effective transfer rate for ingestion of residual

surface radioactivity in this scenario has no sound, technical basis, and, as suggested by the

modifications of Kennedy et al. (1981) and IAEA (1970), this value is extremely conservative. 

In fact, it is envisioned that the dose from this exposure pathway in this scenario would be very

small, because there would be only a very small fraction of the total surface area that would come

into contact with hands (e.g., steering wheel, seat belts, various knobs and handles). Also, the

value of 1 cm2

/hr was originally applicable to loose contamination on smooth work surfaces (e.g.,

Barnes 1959, IAEA 1970), not a decontaminated, non-uniform surface such as the interior of a

truck cab. The value of 1 cm2/hr was also originally applied to the skin as often as other surfaces

(Dunster 1964, IAEA 1970), which would then require a modeling parameter to account for

transfer to the skin from the contaminated surface. Finally, using a value of 1 cm2

/hr would yield

results that are not credible and are counter-intuitive in this analysis. For example, the use of

1 cm2

/hr would result in a secondary ingestion dose for this scenario that is much greater than

doses from other exposure pathways for many radionuclides (i.e., > 95% of the total dose). Also,

for radionuclides with energetic gamma-ray emissions, such as Co-60, an unreasonable amount

of the total dose (10%–15%) would be due to secondary ingestion. The other exposure pathways

have been reasonably evaluated, and it is unexpected and unreasonable that secondary ingestion

would represent such a large fraction of the total dose for so many radionuclides in this scenario. 
Evaluation of Direct Reuse of Equipment Section 3

NUREG-1640 3-12

,5VF ' 5)VF ( %5 ( (% 3.8 

Because a realistic (not overly conservative) analysis was desired for this scenario, alternative

methods of estimating the secondary ingestion rate were explored. A “face validity” check can

be made using the evaluation of Brodsky (1980), who reviewed residual surface radioactivity

data and concluded that a fraction of 10-6 is a reasonably conservative estimate of the maximum

fractional amount of “plant throughput” that a single individual could intake via inhalation and

that intake via ingestion would be lower. “Plant throughput” is the material in process at a

facility and is judged to be analogous to the total amount of residual surface radioactivity initially

present in this scenario. In order to obtain an annual fractional intake via ingestion of 10-6 in this

scenario, an ingestion rate of 7E-5 cm2

/hr would have to be used in equation 3.5. A second

alternative method of estimating the secondary ingestion rate is to base it on the intake of

contamination via inhalation. These exposure pathways are linked in that they both rely on the

removability of contamination from the same surfaces plus a mechanism of intake to the body

(i.e., breathing or hand-to-mouth habits). It seems reasonable that intake via secondary ingestion

could be bounded by the estimated intake via inhalation because resuspension potentially comes

from all exposed surfaces and secondary ingestion comes only from the fraction of exposed

surfaces that is touched. Thus, a second estimate of ingestion rate is based on the inhalation

pathway as follows:

where

IRsc = effective transfer rate for ingestion of residual surface radioactivity (cm2

/h)

and

RFsc = resuspension factor for residual surface radioactivity (cm-1)

BR = breathing rate for moderate physical activity (m3

/h)

1E+06 = unit conversion factor (cm3

/m3)

Using mean values of 1E-10 cm-1 for RFSC and 1.2 m3/h for BR, an IRSC value of 1E-4 cm2/h is

calculated with Equation 3.8. 

Based on the arguments and the alternative methods discussed above, a value of 1 cm2/hr is

clearly an unreasonably conservative value for IRSC in this scenario. Further, use of the 1 cm2/hr

value and the modified International Atomic Energy Agency (IAEA) value (.01 cm2/hr) in

previous studies appears to have been somewhat arbitrary. Taking this into consideration, along

with the other values derived with alternate methods and discussed above (1E-4, 7E-5), a value

of 1E-4 cm2

/hr is reasonable to use as a geometric mean in this analysis. In the absence of any

empirical data, this value is thought to be reasonable for this scenario. 

5HXVH6FHQDULR(YDOXDWLRQ5HVXOWV

The results of the analysis for the equipment reuse critical group scenario are listed in Table 3.2. 

The mean dose factor and the 90% confidence interval for the critical group are reported for each

radionuclide. These results represent dose factors for reuse of equipment cleared from NRC

licensed facilities, based on the bounding scenario that involves the truck driver of a cleared
Section 3 Evaluation of Direct Reuse of Equipment

3-13 NUREG-1640

truck. The dose factors range from a high of 170 μSv/y per Bq/cm2 (0.62 mrem/y per pCi/cm2)

for Th-229 to a low of less than 0.01 μSv/y per Bq/cm2

 (4E-05 mrem/y per pCi/cm2). Roughly

one-third of the dose factors are greater than 10 μSv/y per Bq/cm2 (0.04 mrem/y per pCi/cm2),

roughly one-third are between 0.01–10 μSv/y per Bq/cm2 (4E-05–0.04 mrem/y per pCi/cm2), and

the remaining one-third are less than: 0.01 μSv/y per Bq/cm2

 (4E-05 mrem/y per pCi/cm2). 

The surficial dose factors from the bounding equipment reuse scenario can be compared to the

derived surficial results of the recycle analyses, in order to help interpret the equipment reuse

analysis results. As described in Section 4.7, the mass-based recycle dose factors were converted

to a surficial basis using a surface-to-mass ratio. This yields dose factors in surficial units (i.e.,

μSv/y per Bq/cm2). 

For comparison to the equipment reuse dose factors, the highest recycle analysis critical-group

dose factor for each radionuclide, across the three metals analyzed in this report, was used (from

Table 2.2). After comparison, it can be seen that the surficial metals recycle dose factors are

larger than the equipment reuse dose factors for all radionuclides except Mo-93, Nb-93m, and

Cd-109. This means that for almost all radionuclides, the recycle analyses surficial critical-group

dose factors are more restrictive than the equipment reuse critical-group dose factors. Thus, the

equipment reuse dose factors may not need to be considered when setting clearance dose criteria,

and no individual is likely to exceed the clearance criteria under conditions of any equipment

reuse scenario. 

As described above, the radionuclides Mo-93, Nb-93m, and Cd-109 are unique in this

comparison. The dose factors for Mo-93 yield the largest difference between equipment reuse

and recycle, with the equipment reuse dose factor a factor of approximately 30 higher than the

highest metals surficial recycle dose factor. For these three radionuclides, there is some

possibility that a clearance dose criterion could be exceeded under the conditions described by

the equipment reuse scenario in this analysis.
Evaluation of Direct Reuse of Equipment Section 3

NUREG-1640 3-14

Table 3.2 Dose factors for reuse of a large piece of equipment

Mean dose factor 90% Confidence interval, μSv/y per Bq/cm2

μSv/y per Bq/cm2 mrem/y per pCi/cm2 5th 50th 95th

H-3 1.1E-05 4.1E-08 2.2E-06 7.5E-06 3.1E-05

C-14 3.1E-04 1.1E-06 1.3E-04 2.5E-04 6.4E-04

Na-22 2.6E+01 9.6E-02 1.2E+01 2.5E+01 4.4E+01

P-32 1.7E-03 6.4E-06 7.6E-04 1.6E-03 2.9E-03

S-35 1.2E-04 4.5E-07 4.2E-05 8.7E-05 3.3E-04

Cl-36 1.3E-02 4.9E-05 6.1E-03 1.2E-02 2.2E-02

K-40 1.9E+00 7.1E-03 8.7E-01 1.9E+00 3.2E+00

Ca-41 2.3E-04 8.6E-07 4.5E-05 1.6E-04 6.6E-04

Ca-45 6.7E-04 2.5E-06 2.6E-04 5.2E-04 1.6E-03

Cr-51 4.1E-02 1.5E-04 1.9E-02 3.9E-02 6.9E-02

Mn-54 7.8E+00 2.9E-02 3.6E+00 7.6E+00 1.3E+01

Fe-55 1.5E-04 5.7E-07 2.5E-05 9.4E-05 5.1E-04

Co-57 9.5E-01 3.5E-03 4.4E-01 9.4E-01 1.6E+00

Co-58 3.4E+00 1.2E-02 1.6E+00 3.3E+00 5.8E+00

Fe-59 2.3E+00 8.4E-03 1.0E+00 2.2E+00 3.8E+00

Ni-59 1.0E-04 3.8E-07 1.4E-05 5.6E-05 3.6E-04

Co-60 3.0E+01 1.1E-01 1.4E+01 2.9E+01 5.0E+01

Ni-63 2.6E-04 9.8E-07 3.7E-05 1.5E-04 9.0E-04

Zn-65 4.6E+00 1.7E-02 2.1E+00 4.5E+00 7.8E+00

Cu-67 1.1E-03 4.1E-06 1.7E-04 7.8E-04 3.3E-03

Se-75 2.2E+00 8.0E-03 1.0E+00 2.1E+00 3.7E+00

Sr-85 1.7E+00 6.4E-03 8.0E-01 1.7E+00 3.0E+00

Sr-89 7.4E-03 2.7E-05 3.5E-03 7.1E-03 1.3E-02

Sr-90 1.4E-01 5.0E-04 2.0E-02 6.7E-02 4.7E-01

Y-91 1.0E-02 3.8E-05 4.9E-03 9.9E-03 1.8E-02

Mo-93 3.6E-01 1.3E-03 1.7E-01 3.5E-01 6.1E-01

Nb-93m 6.1E-02 2.3E-04 2.9E-02 5.9E-02 1.0E-01

Nb-94 2.2E+01 8.2E-02 1.0E+01 2.2E+01 3.8E+01

Nb-95 1.2E+00 4.5E-03 5.6E-01 1.2E+00 2.0E+00

Zr-95 2.3E+00 8.5E-03 1.1E+00 2.2E+00 3.9E+00

Tc-99 1.8E-03 6.7E-06 7.2E-04 1.4E-03 4.2E-03

Ru-103 9.6E-01 3.6E-03 4.4E-01 9.2E-01 1.6E+00

Ru-106 2.1E+00 7.8E-03 9.8E-01 2.0E+00 3.5E+00

Ag-108m 2.4E+01 8.9E-02 1.1E+01 2.4E+01 4.1E+01

Cd-109 4.2E-01 1.6E-03 1.9E-01 4.1E-01 7.2E-01

Ag-110m 2.3E+01 8.5E-02 1.1E+01 2.2E+01 3.9E+01

Sb-124 4.9E+00 1.8E-02 2.3E+00 4.8E+00 8.4E+00

I-125 2.6E-01 9.7E-04 1.2E-01 2.6E-01 4.5E-01

Sb-125 5.9E+00 2.2E-02 2.7E+00 5.7E+00 9.9E+00

I-129 7.2E-01 2.7E-03 3.5E-01 7.0E-01 1.2E+00

I-131 7.4E-02 2.7E-04 2.9E-02 6.6E-02 1.3E-01

Ba-133 6.3E+00 2.3E-02 2.9E+00 6.2E+00 1.1E+01

Cs-134 1.9E+01 7.0E-02 8.7E+00 1.8E+01 3.2E+01

Cs-137 8.6E+00 3.2E-02 4.0E+00 8.4E+00 1.5E+01

Ce-141 1.1E-01 3.9E-04 4.8E-02 1.0E-01 1.8E-01
Section 3 Evaluation of Direct Reuse of Equipment

Table 3.2 Dose factors for reuse of a large piece of equipment

Mean dose factor 90% Confidence interval, μSv/y per Bq/cm2

μSv/y per Bq/cm2 mrem/y per pCi/cm2 5th 50th 95th

3-15 NUREG-1640

Ce-144 4.2E-01 1.6E-03 2.0E-01 4.1E-01 7.1E-01

Pm-147 3.3E-03 1.2E-05 3.7E-04 1.5E-03 1.2E-02

Eu-152 1.5E+01 5.6E-02 6.9E+00 1.5E+01 2.5E+01

Eu-154 1.6E+01 5.9E-02 7.3E+00 1.5E+01 2.7E+01

Eu-155 7.5E-01 2.8E-03 3.4E-01 7.3E-01 1.3E+00

Re-186 5.3E-04 2.0E-06 1.4E-04 4.3E-04 1.3E-03

Ir-192 3.2E+00 1.2E-02 1.5E+00 3.1E+00 5.4E+00

Pb-210 1.8E+00 6.7E-03 3.8E-01 1.1E+00 5.9E+00

Po-210 4.2E-01 1.5E-03 5.6E-02 2.2E-01 1.4E+00

Bi-210 1.6E-04 6.0E-07 4.5E-05 1.2E-04 4.6E-04

Rn-222 5.3E-02 2.0E-04 1.4E-02 4.3E-02 1.3E-01

Ra-223 1.2E-01 4.4E-04 5.0E-02 1.1E-01 2.1E-01

Ra-224 3.7E-02 1.4E-04 9.7E-03 3.0E-02 9.2E-02

Ac-225 7.2E-02 2.7E-04 2.9E-02 6.7E-02 1.4E-01

Ra-225 3.7E-02 1.4E-04 1.1E-02 2.4E-02 1.1E-01

Ra-226 2.3E+01 8.6E-02 1.1E+01 2.3E+01 3.9E+01

Ac-227 1.3E+02 4.7E-01 1.6E+01 5.8E+01 4.5E+02

Th-227 1.6E-01 5.8E-04 6.1E-02 1.2E-01 3.6E-01

Th-228 4.1E+01 1.5E-01 1.2E+01 2.7E+01 1.2E+02

Ra-228 1.7E+01 6.4E-02 7.0E+00 1.4E+01 3.6E+01

Th-229 1.7E+02 6.2E-01 1.8E+01 7.5E+01 6.1E+02

Th-230 2.5E+01 9.1E-02 2.0E+00 1.1E+01 9.1E+01

Pa-231 8.2E+01 3.0E-01 8.2E+00 3.7E+01 3.0E+02

Th-231 1.2E-05 4.3E-08 8.7E-08 2.4E-06 5.5E-05

Th-232 1.1E+02 4.1E-01 1.0E+01 4.9E+01 4.0E+02

Pa-233 2.7E-01 1.0E-03 1.2E-01 2.6E-01 4.5E-01

U-233 1.3E+01 4.7E-02 1.0E+00 5.6E+00 4.7E+01

Th-234 1.8E-02 6.7E-05 8.3E-03 1.7E-02 3.0E-02

U-234 1.2E+01 4.6E-02 1.0E+00 5.5E+00 4.6E+01

U-235 1.4E+01 5.1E-02 2.9E+00 7.2E+00 4.5E+01

Np-237 5.5E+01 2.0E-01 8.2E+00 2.6E+01 1.9E+02

Pu-238 2.7E+01 1.0E-01 2.2E+00 1.2E+01 1.0E+02

U-238 1.1E+01 4.2E-02 1.2E+00 5.2E+00 4.2E+01

Pu-239 2.9E+01 1.1E-01 2.3E+00 1.3E+01 1.1E+02

Pu-240 2.9E+01 1.1E-01 2.3E+00 1.3E+01 1.1E+02

Pu-241 4.6E-01 1.7E-03 3.6E-02 2.0E-01 1.7E+00

Am-241 4.2E+01 1.6E-01 4.1E+00 1.9E+01 1.6E+02

Cm-242 8.3E-01 3.1E-03 1.0E-01 3.8E-01 3.0E+00

Pu-242 2.8E+01 1.0E-01 2.2E+00 1.2E+01 1.0E+02

Cm-244 2.3E+01 8.5E-02 2.0E+00 1.0E+01 8.5E+01
Section 4 Recycle and Disposal of Steel

4-1 NUREG-1640

Twenty-seven exposure scenarios for cleared steel scrap that are based on current American

industries are evaluated in this section. Scenario categories include handling and processing,

storage, transportation, product use, and disposal. Four landfill resident scenarios were also

analyzed. A radionuclide-specific, probabilistic dose factor distribution was calculated for the

members of the exposed group in each scenario. The highest mean dose factor among the 27

scenarios on a radionuclide-by-radionuclide basis for 85 radionuclides is the critical-group dose factor

i.e., for an average member of the critical group. This critical-group dose factors are reported in

normalized units of μSv/y per Bq/g scrap (mrem/y per pCi/g) and μSy/y per Bq/cm2 scrap (mrem/y per

pCi/cm2 scrap) for each radionuclide. Dose factors at the 5th , 50th , and 95th percentiles are also

reported.

The most common critical groups are commercial truck drivers carrying cleared steel scrap and

workers at steel refineries. Scenarios involving transport of scrap material resulted in critical group

designation for almost half (39) of the 85 radionuclides in the analysis. Other scenarios identifying

critical groups for many radionuclides involve exposure while handling scrap (14 radionuclides), to

refinery slag and slag leachate (12 radionuclides), and exposure to refinery baghouse dust (11

radionuclides). Only one critical group involves the use of steel consumer products. 

Critical group mean dose factors range from a high of 2.0E+03 μSv/y per Bq/g (7 mrem/y per pCi/g)

for Np-237 to a low of 4.5E-04 μSv/y per Bq/g (1.6E-06 mrem/y per pCi/g) for Ni-59. The derived

surficial mean dose factors range from a high of 1.4E+3 μSv/y per Bq/cm2 (5.3 mrem/y per pCi/cm2 ) to

a low of 3E-4 μSv/y per Bq/cm2 (1E-6 mrem/y per pCi/cm2 ). The high critical-group mean dose factors

of Np-237 are attributed to the drinking water exposure pathway in the refinery slag storage scenario. 

Seventy-nine of the radionuclide-specific, critical group mean dose factors for steel are 270 μSv/y per

Bq/g or lower (1 mrem/y per pCi/g). 

(9$/8$7,212)5(&<&/($1'',6326$/2)67((/

6&5$3

This section describes the technical evaluation of the recycle of steel scrap metal that could be

cleared from Nuclear Regulatory Commission (NRC) licensed facilities. The flow of cleared

steel scrap was modeled using the likely sequence of steps recycled and disposed steel would be

subjected to following clearance. Radioactivity concentrations in recycle byproducts and

disposed materials were calculated, and potential dose factors to members of exposed population

groups were estimated using reasonable formulations of potential situations where individuals

could be exposed to radioactivity in cleared material and recycle byproducts. 

This evaluation is based on mass radioactivity concentration (i.e., Bq/g or pCi/g) because

material likely to be cleared is inventoried on a mass basis. Therefore, all calculated dose factors

are initially in units of annual dose per unit mass (i.e., μSv/y per Bq/g or mrem/y per pCi/g). 

This normalization allows the NRC to scale doses according to concentration of a radionuclide in

scrap to be cleared. The mass dose factors have been converted to surficial dose factors by the

use of a surface-to-mass ratio, which is the ratio of the surface area to the mass of a piece of

scrap or other cleared material. This differs from the dose factors calculated for reuse of

equipment, which are based exclusively on surficial contamination as described in Section 3. 

This surface to mass relationship and its use in converting mass dose factors to surficial dose
Recycle and Disposal of Steel Section 4

NUREG-1640 4-2

factors is discussed later in Section 4. Therefore, all dose factors are also in units of annual dose

per unit surface area (i.e., μSv/y per Bq/cm2

 or mrem/y per pCi/cm2).

,QWURGXFWLRQWR$QDO\VLV

The overall evaluation of the potential dose impacts of recycling and disposal of scrap iron and

steel was conducted in two general steps. First, a probabilistic material flow model specific to

iron and steel scrap was developed, and distributions of material radionuclide concentrations in

recycle products and disposed material were calculated. This step provided the basic

radioactivity for the second step, which was the development and probabilistic evaluation of

potential situations of individual exposure to radioactivity in cleared material and recycle

byproducts. The development of the iron and steel material flow model is discussed in Sections

4.2 and 4.3, and the calculations used to implement the material flow model are presented in

Section 4.4. 

The dose assessment step of the overall evaluation is described in detail in Section 4.6. The

exposure scenarios developed and analyzed are key parts of the assessment. The exposure

scenarios define the exposure situation, so they play an extremely important role in the analyses. 

They define the conditions surrounding the potential exposure of individuals and populations

and, in the modeling of potential exposure, they relate the radionuclide concentration in recycled

and disposed material to the potential dose of an individual. Before developing exposure

scenarios and the approach to be used to model scenarios for this study, several general

objectives were defined. The desired approach was intended to: 

C Simplify the evaluation of numerous possible exposure scenarios

C Identify scenarios that adequately represent critical groups

C Calculate potential dose factors as realistically as possible.

The material flow model was used to identify general scenarios that would represent a

comprehensive range of potential exposure situations. Simple mathematical models of those

non-specific scenarios were developed to streamline evaluation and analysis. The simplicity of

the mathematical models makes them potentially applicable to a wide range of scenarios,

providing flexibility for analyzing potential doses associated with whole categories of scenarios. 

$SSURDFKWR6FHQDULR'HYHORSPHQW

The majority of previous analyses of recycled material did not present a clear rationale for

scenario selection and evaluation. This section of the report documents the philosophy and

technical approach that were used for this project to select, evaluate, and analyze potential

exposures to recycled materials. 

A number of previous assessments have been conducted to quantify the potential radiation

exposures to workers and the general public from recycle of contaminated materials. In general,

these assessments have been based on the formulation and evaluation of fairly specific scenarios
Section 4 Recycle and Disposal of Steel

4-3 NUREG-1640

that describe hypothetical situations in which workers or members of the general public might be

exposed to radioactivity in reused or recycled materials. In order to be comprehensive, this

approach requires identifying the entire range of potential scenarios and using professional

judgement to select a final set for detailed analysis. 

A review of the literature on radiological assessment indicates that there are two general

approaches to scenario-based assessments. The "specific" approach attempts to model, as

accurately as possible, the actual physical circumstances surrounding a selected set of very

detailed scenarios. Among the assessments addressing recycle of radioactive materials, this

approach is exemplified by the work of O’Donnell et al. (1978) in which an iron frying pan was

used as the reference consumer product. The analysis included calculations based on extensive

details of frying pan manufacture and use.

For the purposes of the assessment proposed here, the "specific" approach suffers from several

weaknesses. First, it restricts the number of scenarios that can be treated to those for which

extensive, detailed descriptions can be formulated. Second, it is open to the criticism that the

chosen scenarios are too limited because they do not specifically represent other situations of

interest. Third, many individual parameters are required to describe the scenario details. Each of

the parameter values in the scenario must be defended as technically sound even when only the

grossest estimates are used. Finally, the data requirements of the "realistic" approach introduce

serious demands on available resources. Each value must be researched, documented, and

subjected to quality assurance procedures.

In contrast, a "generic" approach uses broadly defined scenarios that can be taken as

representative of a wide range of possible exposure circumstances and does not attempt to model

the details of any specific, real-world situation. Several recent studies illustrate the main features

of this approach. Charles and Smith (1992), for example, modeled a wide range of consumer

products using a generic geometry factor based on a cylinder of specified height, diameter, and

thickness without attempting to mimic the manufacture and use of actual objects. Deckert et al.

(1992) evaluated two generic geometries, one defined as "a 1 kg object" and the other as "a 1000

kg" object to represent different categories of consumer products.

The "generic" approach addresses each of the objections to the "specific" scenario approach. 

Since each generic scenario is representative of a wide range of situations, the number of

situations addressed is not so severely restricted. By representing a range of situations, carefully

chosen generic scenarios can address any situation of interest that falls into the generic category. 

Finally, the number of detailed parameters can be minimized, along with the need to estimate and

defend values for each parameter. 

The approach taken in this analysis is a combination of the “specific” and “generic” approaches. 

Several specific scenarios have been modeled, as realistically as available data allow. In

addition, several generic scenarios have been modeled to represent a range of potential exposure

situations that are similar.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-4

6FHQDULRVIRU5HF\FOHDQG'LVSRVDORI&OHDUHG6WHHO6FUDS0HWDO

An infinite number of potential exposure scenarios for recycle and disposal of steel scrap could

be postulated. The goal-based criteria set for this study required that the scenarios selected be

comprehensive, appropriate, and practical. Comprehensive means that the scenarios must

address all potential critical group exposure situations. The scenarios must be appropriate to

actual practices in the recycle industry and conditions of product use. Finally from a modeling

viewpoint, the scenarios had to be practical, in that a relatively small number of scenarios needed

to include an extremely large pool of potential exposure scenarios. Selected scenarios had to

account for all potential significant recycle scenarios. The very unlikely cases that could result in

higher doses were excluded on the basis of not addressing the design objective of the analysis.

The approach for this evaluation is similar to that taken by Charles and Smith (1992), who

evaluated the feasibility of different options for managing large volumes of very low level waste. 

The management options included scenarios similar to those selected for this report, including

clearance followed by recycling and disposal of steel and concrete in landfills. The exposure

scenarios used in their models were derived from adopting the various management options. The

methodology used generic exposure scenarios that are similar to the scenarios used in this

evaluation in terms of their generic nature. Scenarios used in previous studies, including

scenarios reported by Charles and Smith (1992), are shown in Table 4.1.

Table 4.1 Scenarios discussed in previous studies

Work-related Non-worker

C Decontamination and dismantling of concrete and

steel structures and handling scrap during the

process

C Transport of scrap to smelter or disposal facility

C Exposure to scrap piles before smelting

C Repair of contaminated machinery

C Operation of smelter and subsequent processing

C Building renovation or demolition

C Landfill disposal (operation of facility or waste

fires)

C Reuse of large concrete masses (building

renovation)

C Reuse of contaminated slag in concrete

manufacture production/manufacture of end

products

C End product use (i.e. frying pan, steel furniture,

steel car, steel reinforcement in houses, large

and small products)

C Smelting process (airborne effluents)

C Slag in roadbeds, foundations of houses, reuse

of contaminated slag in concrete

C Landfill and sanitary disposal of waste products

or contaminated scrap (leachate, inadvertent

intrusion)

C Incineration of contaminated scrap

C Building occupancy by the public

C Drinking water—drinking water that contains

radionuclides leached from surface soils

C Residential (contaminated soil)

C Shallow repository disposal

C Reuse of large concrete masses (building

occupancy)

Rather than attempting to initially define a specific "bounding" scenario, in which potential

exposure is maximized even though the combination of circumstances is very improbable, broad

scenario categories and a combination of general and specific scenarios within the categories

were identified and evaluated. Scenarios were then evaluated so that dose factors calculated in

the model would be realistic estimates for potential real-life situations.
Section 4 Recycle and Disposal of Steel

4-5 NUREG-1640

The material flow model provides a basis for developing exposure scenarios. Junctures in the

material flow that provide opportunities for exposure to radionuclides in recycled iron or steel

define the broad scenario categories, such as handling or product use. Scenarios within those

categories describe the conditions surrounding the potential exposure of individuals and

populations. For example, several scenarios within the handling category evaluate potential

exposure of workers to a variety of material (e.g., scrap metal, baghouse dust, refined metal

product) and locations (scrap yard, refinery, baghouse). The exposure scenarios were selected to

comprise a reasonable set of potential exposures to the estimated concentrations of radioactivity

in scrap metal or refinery co-products.

The combination of a “specific” and “generic” approach used to develop exposure scenarios

provided flexibility in defining a set of reasonable scenarios for identifying critical groups. This

approach addresses a wide range of potential exposure situations and also lends itself to future

evaluation of additional scenarios of interest. 

)ORZRI5HF\FOHGDQG'LVSRVHG6WHHO6FUDS

&RQFHSWXDO'HVFULSWLRQ

This section presents the conceptual model that describes the flow of cleared steel scrap through

the normal refining process, beginning with the generation of scrap, through refining,

manufacturing, product use, and finally disposal. Figure 4.1 presents a schematic diagram of the

overall material flow conceptual model for steel scrap. Both the mass and radioactivity of steel

scrap follow this flow model. As seen in Figure 4.1, there are several distinct steps in the

refining process. Each of these is discussed in the following subsections. Direct reuse of

equipment is discussed in Section 3.

6RXUFHVRI0DWHULDO

There are two sources of materials for the steel refining process: the primary and secondary

metals pools. The primary metals pool consists of pig iron smelted from ore. The material from

this pool would not be contaminated at any point by the recycling of scrap cleared by NRC

licensed facilities because scrap is not used during the smelting of ore. Approximately 5.2E+7 t

(5.7E+7 tons) of pig iron was consumed in 1995 in the U.S. (Fenton 1996).

The secondary metals pool is comprised of scrap metal. A total of 7.2E+7 t (7.9E+7 tons) of iron

and steel scrap was consumed in the U.S. in 1995 (Fenton 1996). There are three types of scrap

metal used in the steel-making industry: home, new, and old. Home scrap consists of unusable

metal produced during the processing or fabrication of steel into a form usable for

manufacturing. Home scrap is usually high-grade metal with very few impurities. Even though

home scrap is produced at the refinery, it is still considered a secondary metal because it is not

the processed raw material, pig iron. New scrap is produced during manufacture of end products. 

New scrap is also high-grade metal with very few impurities. Old scrap includes obsolete, wornout or broken products that have been used by the general public or industry. Old scrap is usually 
Recycle and Disposal of Steel Section 4

NUREG-1640 4-6

Secondary

Metals

Pool

Scrap Dealer

&

Processor

Existing

Recyclers

Use

Transportation

Transportation

&

Distribution

Disposal

Manufacturing

&

Processing

Steel Refinery

Transportation

&

Handling

Cleared

Scrap

Figure 4.1 Flow of steel scrap

low-grade metal, and the chemical composition is not well-known. Therefore, it must first be

sorted, sized, and classified. Cleared scrap metal from the nuclear industry would be considered

old scrap. 

The modeling for this analysis does not distinguish between the different types of scrap. Cleared

materials are assumed to be mixed with a single source of uncontaminated scrap—roughly the

total of old, new, and home scrap sources.

The two sources of secondary metals considered in this evaluation are conventional recyclers,

and potential, cleared scrap metal. Recyclers are the current producers of scrap metal and consist

of the general public (e.g., recycling steel cans), industry (e.g., recycle automobiles), or

manufacturers (e.g., scrap produced during manufacture of end products). 

The main source of the cleared scrap for this study is the nuclear industry (decommissioned

material from nuclear facilities), which consists mainly of commercial power plants, test and

research reactors, and industrial nuclear facilities. Other producers of such scrap include the

Department of Energy (DOE) weapons complex and the Department of Defense (DOD), which

could contribute slightly contaminated scrap primarily from conventional weapons testing and

army and navy test reactors. Approximately 3.0E+3 t/y (3.3E+3 ton/y) of potentially cleared

material is generated each year from NRC licensed facilities; increased dismantling and
Section 4 Recycle and Disposal of Steel

1

Recycle/Reuse Literature Search Report, SAIC, 1994 scheduled to be published as NUREG/CR-5610

4-7 NUREG-1640

decommissioning activities by DOE could increase the mass of steel to about 7.1E+4 t/y

(7.8E+4 ton/y) (NUREG/CR-56101

) for a limited number of years. 

Following entry of cleared material into the steel pool, a continuing buildup of residual

radioactivity levels in steel products to significant levels is not likely. Especially unlikely is any

significant increase in potential individual doses (compared to collective doses). This is because

1) ongoing radioactive decay occurs; 2) virgin, raw materials are continually added to the metals

production processes, and 3) cleared material will comprise only a small fraction of the total

recycled amount of any material. Therefore, the radioactivity concentrations in any subsequent

recycling will likely be lower than that resulting from the initial recycle. Therefore, any

individual doses from secondary recycle would likely be lower than those calculated for initial

recycle in this analysis. The potential, long-term buildup of radioactivity in the steel pool may be

a collective dose issue, but it is not considered an individual dose issue, and is therefore outside

the scope of this analysis. 

7UDQVSRUWDWLRQDQG3URFHVVLQJRI6FUDS

Scrap cleared by a NRC licensed facility must be commercially transported to a scrap dealer or

processor. Not all cleared scrap is likely to be suitable for recycle, so some would be transported

directly to a disposal site. In all cases, transportation could occur either by truck or rail.

After scrap is processed at a scrap dealer, it is transported by rail or truck to a refinery, where it is

usually off-loaded directly for melting in a furnace. Two types of processes are involved in steel

making: smelting and refining. Smelting treats the raw material (ore), to separate the metal

portion (pig iron), from the waste slag. Because the smelting process does not accept scrap, it is

not discussed further in this report. 

Scrap cleared from NRC licensed facilities would become part of the generic refining process

represented by Figure 4.2. Refining takes pig iron produced at a smelter and refines it to a

specified impurity level by adding differing types and amounts of scrap metal. Refining is also

commonly done by using only scrap with no pig iron. The two types of steel refineries currently

in use (integrated and non-integrated) differ primarily in characteristics of the charge (i.e., the

material that is melted in the furnace per cycle). The integrated process accepts small amounts of

scrap per charge and, therefore, produces a product of higher purity. The non-integrated process,

on the other hand, can use up to 100% scrap metal in a charge. This results in a product with

lower purity but with greater strength. 
Recycle and Disposal of Steel Section 4

NUREG-1640 4-8

Figure 4.2 Generic refining process
Section 4 Recycle and Disposal of Steel

1

Recycle/Reuse Literature Search Report, SAIC, 1994 scheduled to be published as NUREG/CR-5610

4-9 NUREG-1640

Together, integrated and non-integrated mills consumed a total of approximately 6.2E+7 t

(6.8E+7 ton) of steel scrap, and produced a total of 9.52E+7 t (1.0E+08 ton) of raw steel in 1995

(Fenton 1996). A small amount of scrap and pig iron is consumed by foundries and other types

of refineries [9.78E+6 t (1.1E+7 tons)] of scrap. However, because these facilities contribute

only a small percentage (<1%) of the total steel production, they are not included in this analysis

(Brown 1993). Refinery worker activities at the two types of steel refineries are similar, and on

average, it takes 3.5 man-hours to produce 0.907 t (1 ton) of steel (NUREG/CR-56101). 

,QWHJUDWHG6WHHO0LOOV

The integrated steel mills use mainly basic oxygen furnaces (BOF). The input material for this

type of furnace consists of molten pig iron, scrap, and flux materials (mostly lime and silica or

limestone). (Flux materials are added to achieve a desired composition.) The exothermic

reaction of oxygen (added during the process), with the molten pig iron, oxidizes and removes

impurities in the iron while providing heat for melting the scrap. The amount of oxygen added

varies depending on the quality of the scrap and the desired final steel chemistry. Furnace

capacities of BOFs range up to 300 t (330 ton) per charge, and the required time per melting

cycle typically ranges from 25 to 45 minutes (EPA 1986). The average size of a charge in a BOF

refinery is estimated to be 58 t (64 ton) with an average of 5580 charges per year for one refinery.

The fumes that are generated when oxygen is added to a BOF are captured by the primary

exhaust hood and cleaned by high pressure venturi scrubbers or electrostatic precipitators. The

fumes generated during melting, tapping (pouring molten steel), and slagging (decanting slag) are

captured by local or canopy hoods and transported via a duct system to a baghouse. (For this

report the fume collection system is generalized and referred to as a baghouse.) The BOF

baghouse is assumed to be 99.9% efficient because of the cleaning efficiency of the primary

collection system in conjunction with the baghouse (Mody and Jaknet 1988). 

Scrap used in the BOF refining process is largely home scrap. Because of the small percent of

old scrap used, the concentrations of Environmental Protection Agency (EPA)-listed hazardous

metals (i.e., lead, cadmium, and chromium) in the dust are below regulatory limits. Therefore,

BOF dust is not listed as a hazardous waste (EPRI 1993). 

The integrated mills produce "flat" products (e.g., sheets and strips) and supply the consumer

goods market, mainly automotive and appliance. In 1995, BOFs consumed about 22% and 96%

of the total scrap and pig iron, respectively used in the U.S., while producing approximately 60%

of the total raw steel for that year (Fenton 1996). 

1RQ,QWHJUDWHG6WHHO0LOOV

The non-integrated steel mills employ mostly electric arc furnaces (EAF), and primarily produce

carbon steel. The input material to an EAF is usually 100% scrap, with a very small amount of
Recycle and Disposal of Steel Section 4

NUREG-1640 4-10

flux. Capacities of EAFs vary, ranging from a diameter of 2 m (6.6 ft) and a product capacity of

3 t (3.3 tons), to 12 m (39 ft) with a capacity of 360 t (397 tons) (EPA 1986). Melting cycles

range from about 11⁄2 to 5 hours to produce carbon steel. Based on information presented in the

1993 Directory of Iron and Steel Plants (AISE 1993), the average size of a charge in an EAF

refinery is 88 t (97 ton) with an average of 5,580 charges per year for one refinery.

The fumes generated during the meltdown and refining period of an EAF are evacuated directly

off the furnace (direct shell evacuation) and transported via a duct system to the collection

system. The fumes produced during melting, tapping, and slagging are evacuated through a fume

collection hood on the roof of the building, then transported through a duct to the collection

system. The most efficient, cost-effective, and typical collection system used to control the EAF

fume dust is the fabric filter baghouse system. Discussions with industry indicate that these

systems typically have a collection efficiency greater than 99% when running optimally.

However, Cass and Langley (1977) provide data from a controlled experiment that measured dust

characteristics from an EAF refining carbon steel. Measurements included particle size and mass

at both the inlet and outlet of a baghouse. Ten separate experiments were run. The mass fraction

penetrating the filters was reported to have a mean of 1.904 % with a standard deviation of

0.3862 % (Cass and Langley 1977). The mean value corresponds to a filter efficiency of 98.1 %. 

The mass penetration value that is two standard deviations above the mean is 2.68 %,

corresponding to a filter efficiency of 97.3 %. The mass penetration value two standard

deviations below the mean is 1.13 %, corresponding to a filter efficiency of 98.9 %.

Cuscino (1979) reports the results of emission measurements at a variety of steel refineries. The

data are difficult to interpret because of variations between facilities and variations between

sampling procedures. Two pairs of values are given which provide measures of dust entering and

leaving a baghouse. These measurements provide two direct estimates of filter efficiencies at

97.3% and 95.0%. In addition, four values related to dust production are reported for emissions

measured downstream from a baghouse at an EAF refinery making carbon steel from scrap. 

These are 0.02 kg dust per metric ton of steel produced and 0.072, 0.16, and 0.85 kg/t of scrap

input. If one assumes 15 kg of dust enters the baghouse per metric ton of steel produced and 90 t

of steel is produced per 100 t of scrap (see Section 4.3), these values correspond to mass

penetration fractions of 0.15%, 0.54%, 1.2%, and 6.3% with a mean of 2.0%. The corresponding

filter efficiencies range from 99.8% to 93.7% and average 98%. Although these values are

questionable because of the quality of the original data and the assumptions required to interpret

them, they are consistent with values from controlled experiments. They are used here to justify

a wider range of uncertainty in real baghouse efficiencies than in the controlled experiments. 

Cuscino (1979) reports that, depending on refinery configuration, significant fractions of refinery

dust may not be ducted to the baghouse and may be emitted unfiltered to the atmosphere. 

Therefore, a value of 98% is a reasonable most likely value for the baghouse filter efficiency,

BHeff, for an EAF refinery.

Because a large percentage of an EAF charge is comprised of old scrap, the concentrations of

hazardous metals (i.e., lead, cadmium, and chromium) in the baghouse dust, which are regulated
Section 4 Recycle and Disposal of Steel

4-11 NUREG-1640

under the Resource Conservation and Recovery Act (RCRA), are above regulatory limits

(EPRI 1993). Therefore, the EAF baghouse dust is listed by the EPA as a hazardous waste and is

handled differently than BOF dust. 

The non-integrated mills produce high-strength, low alloy steel, supplying mainly the

construction industry. In 1995, EAFs consumed about 64% and 3% of the total scrap and pig

iron used in the U.S., while producing about 40% of the total raw steel made in that year

(Fenton 1996). The remaining 14% scrap and 1% pig iron were consumed by other facilities

(e.g., blast furnace, cupola furnace, etc). It is common practice for an EAF to operate using only

scrap metal as feed.

The amount of oxygen used in the EAF process is assumed to be about the same as the amount

used for the BOF process. For the purpose of this analysis, a BOF and an EAF are treated the

same for determining the elemental partitioning factors, but are modeled differently for other

factors, including scrap dilutions, baghouse efficiency, end products, and EPA regulation of the

dust. Table 4.2 lists the differences that are relevant to the modeling in this analysis.

Table 4.2 Key assumptions for the steel material flow model

Assumptions Basic oxygen furnace Electric arc furnace

End product and use flat products and used mainly in the

consumer goods market

high-strength, low alloy steel and

used mainly in the construction

industry

End use of baghouse dust disposed of in a sanitary landfill on

site

sent to metals recovery, fertilizer, or

disposal in a hazardous (RCRA)

landfill

Temperature inside furnace 1600EC 1600EC

Temperature inside the baghouse 190EC 190EC

Chemical form of elements entering

baghouse

oxides oxides

Efficiency of baghouse 99.9% 98%

Type of slagging agent used in

furnace

basic basic

Average size of a charge 58 t 88 t

Average number of charges per year

for a single refinery

5,580 5580
Recycle and Disposal of Steel Section 4

NUREG-1640 4-12

2XWSXWRI5HILQHU\3URFHVVHV

During the refining process (using either the EAF or BOF), the furnace contents separate into

four different end products: off-gas, dust, slag, and metal (Figure 4.2). Both the mass and

radioactivity are redistributed (partitioned) into the different end products. To account for this in

the material flow modeling, partitioning factors for both mass and radioactivity were developed

and are discussed in detail in Section 4.3.

Each of the end products undergoes a different process, use, and final disposal. The off-gas

includes elements that are completely volatilized into stable gases or very fine particles during

refining and exit the refinery stack. Furnace fume dust includes elements that are volatilized

from the furnace, form particulates when cooled, and are collected in baghouse filters. Neither

EAF or BOF air pollution control systems are 100% efficient, and a small percentage of the dust

exiting the baghouse is released to the atmosphere with the off-gas. After collection, BOF dust is

placed in a sanitary landfill.

The baghouse dust from EAF facilities is classified as a RCRA hazardous waste because of the

metal content (EPA Waste No. K061), and refineries have two options for disposition of the dust: 

treatment and disposal, or delisting. Both of these options are addressed in the material flow

modeling. At the time this issue was investigated, the two most common treatment and disposal

methods in use were 1) immobilization treatment, followed by disposal, and 2) high-temperature

metals recovery. Immobilization and disposal is explicitly addressed in the modeling for this

analysis, as described in subsequent sections of this report. Metals recovery was also

investigated, including calculation of radionuclide concentrations in recovered metal products. 

However, the calculated radioactivity concentrations have a very large degree of uncertainty

associated with them (due primarily to the lack of specific information about the proprietary

metals recovery processes) and were judged to be inadequate to support development of new

scenarios associated with metals recovery. Therefore, the radionuclide concentrations of

recovered metal are not used further in this analysis, but their uncertainty suggests areas for

future investigation, and also to address the types of questions that can arise during rulemaking

and related activities. Electric arc furnace dust is transported by truck to either a hazardous

landfill facility or to a processor. At either type facility, it is typically unloaded in an enclosed

building, where it is immediately placed in a bin and moistened with water for dust control.

Steel-making slag is not considered a hazardous waste, therefore, it can be reprocessed for use or

directly disposed of. Typical uses of slag are railroad bases, aggregate, and railroad ballast. 

After slag is removed from the furnace and cooled, it is stored in piles outdoors at the refinery

until it is either used by the refinery or transported to a slag processor. Approximately 10% of

the total slag produced in 1992 was used at the plant where it was originally produced

(Solomon 1993). Slag is transported from the refinery to manufacturers or processors by either

truck, rail, or waterway. Of the slag produced and transported in 1992, 82.9% traveled by truck

with an average range of 45 km (72 mi), 3.6% traveled by waterway with an average range of

400 km (250 mi), and 3.5% traveled by rail with an average range of 400 km (250 mi)
Section 4 Recycle and Disposal of Steel

4-13 NUREG-1640

(Solomon 1993). As those figures indicate, most slag is used within a 50 km (80 mi) radius of its

source. 

Basic oxygen furnaces and EAFs yield different types of metal products. Electric arc furnaces

manufacture mainly bar products for use in the construction industry. These products have a

lower purity and a greater strength than BOF products and do not require additional

manufacturing or processing prior to use. The metal produced at mills using BOFs is usually in

sheet form and will undergo additional manufacturing or processing for use in items such as

appliances or automobiles. Both product types follow the flow model presented in Figure 4.1. 

Basic oxygen furnace metal products are transported from the mill to manufacturers or

processors by either truck, rail, or waterway.

Manufacturing and processing converts slag and BOF metal products created at the refineries

into finished products. Manufacturing involves activities such as cutting and shaping the metal. 

Electric arc furnace refined metal products are not processed after leaving the refinery. 

After a metal product or slag is manufactured into a finished product, it must be transported and

distributed to the general public (i.e., end user). Facilities involved in the distribution of finished

metal products, produced at both EAFs and BOFs, include stores, warehouses, and car lots. Slag

is usually distributed and transported directly from the refinery where it is produced or from the

manufacturer where it is processed. EAF dust is usually processed (immobilized) at the same

facility where it is disposed of and requires no additional transportation. EAF dust that is

processed into fertilizer is containerized and shipped by truck to distributors. 

There are other refinery byproducts in addition to refined metal, slag, and baghouse dust. 

However, these represent comparatively small material flow pathways, and have not been

evaluated in this analysis. One such byproduct is mill scale, which is the oxidized surface of

refined steel that is produced, for example, during the hot rolling of steel slabs. Scale consists of

a mixture of iron oxides, and therefore has a high iron content (e.g., 55%). Scale production can

be as high as 1% of refined steel output at a refinery, but is more typically between 0.5% and

0.75%. Scale must be removed from refined steel because it results in unwanted characteristics

of the finished steel. Because of its high iron content and other characteristics, mill scale is a

commodity and can be used in the steel industry as well as the cement industry. Partitioning of

radionuclides to scale has not been evaluated for this analysis, but it would be dependent on the

partitioning to refined steel, and it is likely that radionuclide concentrations in scale would be

roughly the same as in refined steel. Radionuclides in any mill scale that is returned to the steel

industry would likely end up in refined steel at some point, at lower concentrations than initially

in the scale. The fate of radionuclides in scale that is used in the cement industry is unknown,

however the evaluation of slag use in concrete in this analysis may be an adequate substitute

analysis for this potential flow pathway. 
Recycle and Disposal of Steel Section 4

1

Personal communication between Mary Anderson (SAIC) and J. Wyett (Frit Fertilizer), February 1995.

NUREG-1640 4-14

'LVSRVLWLRQRI($)%DJKRXVH'XVW

Between 450,000 and 590,000 t (500,000 and 650,000 tons) of EAF baghouse dust is generated

each year in the U.S. This dust is classified as a RCRA hazardous waste because of the metal

content (EPA Waste No. K061). For many years, the majority of the dust was thermally treated

for metals extraction or disposal. Data available at the time this was formally investigated (for

calendar year 1992) indicated processes that an estimated 86.5% of the EAF dust generated was

treated by high-temperature metals recovery (EPRI 1993). Therefore, the high-temperature

metals recovery process was evaluated for this analysis. However, because of a high degree of

uncertainty in the modeled radionuclide concentrations of byproducts, plus evolving industry

practices, these concentrations were not used for scenario evaluation.

Also in 1992, approximately 11.2% of all EAF dust collected by baghouse filters was treated and

disposed of as hazardous waste (EPRI 1993). The standard treatment prior to disposal is

immobilization. Electric arc furnace dust is immobilized by mixing it with hydraulic cement, the

most common of which is Portland cement. Cement hydration reactions require that the wastecement mixture have an alkaline pH. While cement—a highly alkaline medium—is quite

effective itself in raising the pH of most wastes, its effectiveness is limited, particularly with

highly acidic wastes. Such wastes are typically pretreated to raise the pH before solidification.

At the disposal facility, EAF dust is treated to obtain a waste form that meets RCRA

immobilization requirements. Typically about 100 g of EAF dust is mixed with about 30 g of

two additives (liquid reagent and dry cement), which results in a dilution factor of 0.77; the

density of the solidified product is typically 1.36 g/cm3

 (Logan 1993). It is then loaded into steel

roll-off boxes or drums, which are temporarily stored in the yard. When laboratory tests confirm

that the waste meets EPA treatment standards, the containers are placed in the disposal trench. 

The remaining 2.3% of EAF dust collected by baghouse filters was used for the manufacture of

fertilizer in 1992 (EPRI 1993). According to 40CFR266.20, which details use of EAF dust in

fertilizer, EAF dust used in fertilizer is no longer regulated under RCRA; however, this

classification is subject to change. In this application, fertilizer manufacturers treat the dust with

sulfuric acid to form soluble zinc compounds and insoluble lead sulfates. Fertilizer

manufacturers require high zinc content (preferably above 20%) in the dust (EPRI 1993) to

achieve a reasonable maximum concentration of zinc in fertilizer of 3%.1

 Assuming that the

initial concentration of zinc is 20% in the EAF dust and that the final zinc concentration is 3% in

enriched fertilizer, 1.36E+5 g of EAF dust would be added to 7.71E+5 g of non-enriched

fertilizer (additives).1

 This results in a dilution factor of 0.15. All EAF dust shipped for use in

fertilizer manufacturing is consumed during the process. The enriched fertilizer is loaded into

packing loaders, boxed, and shipped out on trucks. 

The disposition of EAF dust has been an issue for the steel industry for several years; as a result

of this, the regulatory situation is evolving. Because of the regulatory and liability issues,
Section 4 Recycle and Disposal of Steel

4-15 NUREG-1640

industry has responded rapidly with new practices for the disposition of EAF dust: these

changing practices, however, make the process difficult to analyze. New recycle processes are

being developed to remove heavy metals and zinc oxide, producing various byproducts such as

building bricks, roofing granules, and abrasives. Also, several approaches to minimize the

amount of dust requiring disposition are being investigated by the steel industry. This includes

efforts to minimize the generation of dust and various on-site recycling programs. There is

sufficient economic motivation and environmental liability to pursue such efforts, so practices for

the disposition of EAF dust will likely continue to evolve.

3URGXFW8VH

Slag or finished metal products are used by the public for many applications. Examples of

finished metal products from BOFs are small appliances (e.g., toasters), automobiles, public

transportation vehicles, furniture, and small objects that would be in contact with the body, such

as jewelry. Types of finished EAF metal products include large items (reinforcements for

houses, rebar, fence posts) and smaller objects (tools and belt buckles). Slag can be used in

commercial applications for construction (various types of concrete aggregates and products),

road-building (road bases), glass manufacture, mineral wool, railroad ballast, and soil

conditioning (Solomon 1993). Fertilizer containing EAF dust is used by the agricultural industry

to fertilize produce that is meant for human consumption. However, because of the concerns

discussed above, EAF dust fertilizer is not included in this analysis.

'LVSRVDO

The ultimate endpoint for finished metal products, slag, and BOF dust is disposal in a public

sanitary landfill (RCRA Subtitle D). The types of objects that could end up in a public sanitary

landfill include discarded end products, waste from manufacturing, slag directly from the

refinery, products made from slag, scrap not suitable for reuse or recycle, and BOF dust. The

ultimate endpoint for immobilized EAF dust is a hazardous landfill (RCRA Subtitle C).

0DVVDQG(OHPHQWDO3DUWLWLRQLQJ)DFWRUVIRU5HILQHU\2SHUDWLRQV

Redistribution (partitioning) of the radioactivity and mass present in cleared steel scrap entering

the refinery furnace must be followed to estimate concentrations of radionuclides in various

recycle end products. Partitioning factors are defined as the fraction of original radioactivity or

mass of scrap entering the refinery furnace that would be present in various end products. 

For this analysis, the mass of scrap metal entering a furnace during the refining process is

redistributed into the three immediate products of the refining process: metal product, slag, and

dust. Radioactivity in incoming scrap metal is also redistributed among those products, as well

as in the off-gas leaving the refinery stack. Assumptions and data used to develop the

partitioning factors, as well as calculated partitioning factors used in the material flow modeling

for both mass and radioactivity, are discussed in the following sections.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-16

0DVV3DUWLWLRQLQJ)DFWRUV

Mass partitioning factors are calculated and used for the metal product, slag, and dust. 

Partitioning factors for the metal product and dust are based on literature, while those for slag are

calculated by approximating conservation of mass.

The partition factor distributions are not sampled to ensure that they add up to 1.0 for any single

run within a Monte Carlo simulation. This is not necessary since each exposure scenario

calculates dose factors from radioactivity in only one material at a time (i.e., refined metal, slag,

or baghouse dust). 

0HWDO3URGXFW

Industry data indicates that EAFs typically produce 90 t (99 tons) of steel for every 100 t

(110 tons) of scrap used (Lankford et al. 1985). Data reported by the American Iron and Steel

Institute for the period 1988 through 1992 yield an average mass partitioning factor for metal

product (fp1) of 90% with a range from 85% to 95% (AISI 1993). These estimates are supported

by three industry contacts (Border Steel, TX , Bayou Steel, LA, and Arkansas Steel, AR). Each

of these three refineries indicated that they controlled their process toward a target yield of 90%

with a range from 88% to 92%.

%DJKRXVH'XVW

All available references give dust generation rates in terms of mass of dust per mass of steel

produced not per mass of scrap used. In order to estimate a mass partitioning factor, some

assumptions must be made regarding the mass of steel produced per mass of scrap used. The

equation for the mass partitioning factor for dust, fd1, is as follows:

 fd1 = Massdust / Massscrap used

= (Massdust / Masssteel produced) * (Masssteel produced / Massscrap used)

= (Massdust / Masssteel produced) * fp1

The value used here for fp1 (mass partitioning factor for metal product) is 90 t (99 tons) of carbon

steel produced per 100 t (110 tons)of scrap used (see Section 4.3.1.1).

There is remarkable consensus in the literature for a best estimate value of 15 kg of dust per

metric ton of carbon steel produced at EAF facilities. Brough and Carter (1972) and Venturini

(1970) give 15 kg/t a “measured operating value.” This value is supported by two industry

contacts (Border Steel, TX and Arkansas Steel, AR). EPRI (1993) presents 15 kg/t of capacity as

an industry average of 52 plants responding to their survey. A dust production rate of 15 kg/t of

steel produced corresponds to an fd1 of 0.014.

Estimates of the range of dust production are also fairly consistent. Brough and Carter (1972)

cites a range of 7.5 to 20 kg/t as a specification for baghouse design. Elert and Wiborgh (1992)
Section 4 Recycle and Disposal of Steel

4-17 NUREG-1640

cites a range of 10 to 15 kg/t for Swedish EAF steel mills. Szabo and Gerstle (1978) gives a

range of 12 to 29 kg/t. The range used for this evaluation is from 10 to 25 kg/t which

corresponds to a range in fd1 of 0.009 to 0.023.

6ODJ

Steel yield is well-known because it is of significant economic importance, and baghouse dust

production is well-known because it is a regulated material. However, the mass of slag produced

per mass of scrap is not well-documented in the literature and has not been readily available from

industry contacts. Estimates for slag production can be calculated based on a mass balance for a

typical carbon steel recipe. In addition to scrap, the typical EAF uses fluxing agents (mostly lime

and silica or limestone) at a rate of about 38 kg/t of scrap (AISI 1993). Small amounts of other

materials are included in the melt (carbon, consumed electrodes, and refractory brick). In

addition, oxygen is consumed in the oxidation of materials that are incorporated into slag. Slag

consists primarily of iron oxide, calcium, and silicon oxides from oxidation of fluxes, along with

oxides of various metals appearing as impurities in scrap. Slag is about 20% oxygen by weight

(Lankford 1985). 

Table 4.3 provides estimates for slag production using a mass balance approach. Sufficient

oxygen has been included to account for oxidation of the fluxing material and the difference in

mass between the scrap and the steel produced. The masses of steel and dust produced are taken

from preceding sections of this report. Dust production is assumed to be inversely proportional

to steel production. That is, the maximum dust production of 2.0% occurs when steel production

is 85%, the minimum dust production of 0.9% occurs when steel production is 95%, and the

average dust production of 1.4% occurs when steel production is 90%. Using this method, a

value of 0.16 is chosen for the most likely estimate for the mass partitioning factor for slag, fs1.

Table 4.3 Values used for calculation of EAF mass partitioning factors (metric tons per charge)

Nominal High* Low*

Furnace Input

Scrap 100 100 100

Flux 4 4 4

Oxygen 3.15 2 4.3

Total 107.15 106 108.3

Furnace Output

Steel 90 95 85

Baghouse Dust 1.4 0.9 2.0

Slag 15.75 10.1 21.3

Total 107.15 106 108.3

* High = Highest yield of steel (lowest production of baghouse dust and slag)

 Low = Lowest yield of steel (highest production of baghouse dust and slag)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-18

%DVLF2[\JHQ)XUQDFH

As cleared steel scrap is processed in a refinery, new refined metal, dust, slag, and off-gas is

produced. A mass partition factor is used in the model to simulate the quantity of each of the

four media produced during refining. The uncertainty in the mass partition factors is related to a

number of factors including composition of the scrap, the refining method used, fluxing,

charging, and other factors. The mass partition factors are different for EAF and BOF refinery

processes because of different furnace charging procedures.

The efficiency for an EAF has a most likely value of 90% with a range of 85% to 95%. 

According to Lankford (1985) a typical basic oxygen furnace (BOF) has a yield of about 88%. 

(i.e., 88 t of metal product produced for every 100 t charge). However, a charge in a BOF can

consist of 20–35% scrap with a typical value of about 32.2% (Lankford 1985). A value of 32 t of

scrap for every 100 t of metal charge is used for the amount of scrap in each charge.

Because no information was found to indicate that a typical BOF is less efficient than an EAF,

the same efficiency range for the BOF metal-product mass partitioning factor is used.

The only available reference gives dust generation rates in terms of mass of dust per mass of steel

produced not per mass of scrap used. According to EPA (1986), about 14 kg of dust is produced

for every metric ton of metal product produced in a BOF. In order to estimate a mass partitioning

factor for dust, some assumptions must be made regarding the mass of steel produced per mass of

scrap used. The equation for fd1 is as follows:

 fd1 = Mdust / Mscrap used

= (Mdust / Msteel produced) * (Msteel produced / Mscrap used)

= (Mdust /Msteel produced) * fp1

The mass of slag produced per mass of scrap is not well documented in the literature and has not

been readily available from industry contacts. Steel yield is well known because it is of

economic importance. Estimates for slag production can be calculated based on a mass balance

for a typical carbon steel recipe. In addition to scrap and pig iron, the typical BOF takes fluxing

agents (mostly burnt lime and dolomitic lime) at a rate of about 90 kg/t (180 lb/ton) of metal

product produced (Lankford 1985). Small amounts of other materials are included in the melt

(carbon, consumed electrodes, refractory brick, and fluorspar). In addition, oxygen is consumed

in the oxidation of materials that are incorporated into the slag. Oxygen is added at a rate of

about 2 m3

 per minute per metric ton for a period of 16 to 25 minutes (Lankford 1985). 

Assuming an average period (20.5) for the oxygen blow and density of 1.43 g/L for oxygen at

standard temperature and pressure (CRC 1992), approximately 5.9 t of oxygen is used for a 100 t

(scrap + pig iron) charge.

Table 4.4 provides input and yield estimates used for calculating mass partitioning factors for the

metal product, dust, and slag.
Section 4 Recycle and Disposal of Steel

4-19 NUREG-1640

Table 4.4 Values used for calculation of BOF mass partition factors (metric tons per charge)

Nominal High* Low*

Furnace Input

Pig Iron 68 68 68

Scrap 32 32 32

Flux 7.8 7.8 7.8

Oxygen 5.9 5.9 5.9

Total, t 113.7 113.7 113.7

Furnace Output

Steel 88 95 85

Baghouse Dust 1.2 1.3 1.2

Slag 24.5 17.4 27.5

Total, t 113.7 113.7 113.7

* High = Highest yield of steel (lowest production of baghouse dust and slag)

 Low = Lowest yield of steel (highest production of baghouse dust and slag)

(OHPHQWDO3DUWLWLRQLQJ)DFWRUV

This section presents the basic assumptions and methodology used in developing the elemental

partitioning factors. Section 4.3.2.3 summarizes a comparison of the estimated partitioning

factors used in this analysis against data available in the literature.

%DVLF$VVXPSWLRQV

All the elements included in the material flow model, with the exception of the actinides and

noble gases, are typically found in steel-making as components of steel scrap, alloying additions,

or unwanted impurities. Sulfur, for example, is usually an unwanted impurity in steel. However,

sulfur and other chalcogenides are sometimes added to alloys to produce free-machining steels. 

In general, steel making processes and operating conditions have been developed that, depending

on the desired result, can maximize the retention of a particular element in the molten steel or,

conversely, maximize its removal. The elemental partitioning factors determined for the material

flow model are intended to be representative of the expected behavior during melting in a typical

domestic EAF or BOF. 

It is recognized that there will be variability in the behavior of elements during the refining of

steel. For example, cesium may almost completely volatilize to the dust if a basic slag is used,

but would tend to partition to both the slag and dust if a neutral or acidic slag is used

(Harvey 1990). Other factors that could affect elemental partitioning factors are gas sparging,

mixing, or the type of desired melt (e.g., carbon steel or stainless steel). Thus, any single

partitioning value used in the material flow modeling has some associated uncertainty. In order

to address this uncertainty, the partitioning values are included as variables in the uncertainty

analysis of the material flow modeling. 

The primary components of a typical steel refining facility that are important to the material flow

model are the primary melting chamber (the furnace) and the air pollution control system. As
Recycle and Disposal of Steel Section 4

NUREG-1640 4-20

stated previously, the air pollution control system consists of a fabric baghouse filter. Other

components of the refinery, such as ladles, tun dishes, and reheating ovens, are not important to

the material flow model because no phase changes occur and there is no dilution or concentration

of elements. The most common type of furnace uses a basic process with a basic slag (Lankford

et al. 1985). Other processes, such as the use of different slagging agents, gas sparging, and

mixing, can affect the partitioning of elements. However, for this study, these will not be

included because their use in refineries is extremely variable and their effects are difficult to

predict.

During refining, elements can partition to one or both of the main melt components (i.e., the slag

and metal phases), or discharge from the furnace in the volatilized gas. Some of the elements

that leave the furnace in the volatilized gas will remain in the vapor phase (off-gas) and some

will condense or coalesce into particulates (dust). Elements found in coarse particulates are

captured by the baghouse filter. Some of the fine particles and species in the vapor phase will

escape in the off-gas exiting the stack. A small fraction of metals and oxides that are refractory

or ferrous in nature will be carried over to the dust. Based on general knowledge of these

elements in baghouse dust and actual experience with EAF baghouse dust, a fraction of 1% was

assumed to be carried over to the dust for this flow model. For example, even though iron is a

ferrous element and would be expected to partition completely to the steel product, data from

baghouse filter dust analyses show that iron is present in baghouse dust (EPRI 1993). 

The refinery furnace is assumed to be using a basic process, i.e., basic slag, with an average

temperature of about 1600EC. The average temperature of the baghouse is assumed to be 190EC. 

For purposes of determining partitioning, it is assumed that the air flowing through the baghouse

is cooled to this temperature. Other assumptions include those listed in Table 4.2.

*HQHUDO0HWKRGRORJ\IRU'HWHUPLQLQJ(OHPHQWDO3DUWLWLRQLQJ

In order to simplify the material flow modeling, elements of concern were grouped according to

their elemental partitioning factors. It was assumed that all isotopes of a given element would

behave identically (no isotope effects).

First, the likely chemical form of the element in question after charging the furnace was

determined. For example, iron, cobalt, and nickel will remain in the metallic state as part of a

solid solution in the steel. Elements that are more reactive than iron will readily form oxides

(e.g., Pu, Ac, Th). The physical properties of that form, particularly boiling point, were then

examined. If the boiling point of the element of interest is less than 1600EC, then it is assumed

to volatilize from the melt or the slag. However, if the boiling point of the element of interest is

greater than 1600EC, it is assumed to remain in the original form. Most volatilized from the

furnace will form oxides before they reach the baghouse, no matter what their form at the time of

volatilization. To determine if the element that volatilizes from the furnace will stay in the vapor

phase or form particulates, the boiling points of the oxide of these elements were compared to the

temperature of the baghouse (190EC). If the boiling point of an element is greater than 190EC, it

will tend to form particulates as it cools, with a small fraction remaining in the vapor phase. If
Section 4 Recycle and Disposal of Steel

1

Personal communication, G. L. Leatherman, Science Applications International Corporation, 1995.

2

Personal communication, A. Murray, Science Applications International Corporation, 1995.

4-21 NUREG-1640

the boiling point is less than 190EC the element will remain in the vapor phase with a small

fraction forming particulates. For example, zinc, which is found as a metal, boils at a

temperature well below the expected temperature in the furnace. Thus, zinc is expected to

partition primarily to the off-gas components. However, the boiling point of zinc oxide is well

above 190EC, and it is expected to form particulates (dust). On the other hand H, I, and Rn are

assumed to remain in the vapor phase. 

In some cases, it is inappropriate to assume elements will appear as oxides in the baghouse. For

example, the partitioning of chlorine depends on the presence of alkali metals. Even though the

elemental characteristics indicate that chlorine would form a stable gas, it would likely tend to

form particulates if alkali metals are present. Based on this information, it is determined that a

small fraction of chlorine would most likely form particulates.

There are some elements that were treated as special cases because certain chemical reactions

occur in the furnace that do not follow the methodology presented above. These special case

elements and their expected behavior are presented below.

P - oxidized by a basic slag and volatilizes as an oxide

C - alloys with steel (with more oxygen it will tend to volatilize)

Se - generally difficult to remove from steel

Sb - readily alloys with steel and is difficult to remove

Mn - used extensively in the steel industry for desulfurization and reacts with sulfur to form

MnS2 which forms as inclusions in the steel melt.

Na - very reactive and readily forms oxides. Because of the temperature at which Na2O

sublimes it will only partially volatilize from the slag.1

Tc - alloys with steel and is difficult to remove.2

Ru - alloys with steel and is difficult to remove.2

Bi - reactive and readily forms oxides. Because of the temperature at which Bi2O5

decomposes it will only partially volatilize from the slag.

K - very reactive and readily forms oxides but decomposes at a low temperature and will

volatilize in the elemental form.

Pb - normally less reactive than iron. With the addition of oxygen it will form oxides and

volatilize.

Table 4.5 lists elemental partitioning factors for each element in the anlaysis. For many elements

there is sufficient data to identify a most likely value within this range. In probabilistic

calculations, these are described using a triangular distribution with the mode equal to the most

likely value. For some elements, the data do not allow a best estimate to be chosen from the

ranges in the table. Partitioning of these elements is described by a uniform distribution of

values across the ranges with maxima and minima, as shown in the table. Information on the

uncertainty distributions for this parameter appears in Appendix B, Table B.3.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-22

Table 4.5 Elemental partitioning factors (EPF) for steel

Elemental partitioning factors (%)

Elements Metal product Baghouse dust Slag Volatile

Ag, C, Co, Cu, Mo, Ni, Ru, Tc 95–100 0–2 0–1 0

Sb 80–100 0–1 0–20 0

Se 0–80 0–80 20–77 0

Fe 95–100 0–2 0–5 0

Pb 0–5 95–100 0–5 0

Zn 0–20 80–100 0–1 0

Cd, Cs, Po 0–1 95–100 0–5 0

S 0–20 4–97 0–3 0

Re 0–99 1–97 3–87 0

P 0–10 4–97 3–77 0

K 0–1 50–100 3–50 0

Ir 0–100 0–100 0–3 0

Bi 0–25 45–100 0–25 0–5

Mn 24–50 0–4 50–75 0

Cr 49–99 0–1 0–50 0

Na 0–10 40–50 45–55 0–5

Ra 0–5 0–5 95–100 0

Ac, Am, Ba, Ca, Ce, Cm, Eu, Nb, Np, Pa, Pm,

Pu, Sr, Sm, Th, U, Y, Zr

0–1 0–5 95–100 0

Cl 0–1 8–50 0–50 0–90

I, Rn 0 0 0 100

H 0–10 0 0 90–100

EPF = [element concentration in product/element concentration in scrap]×100

Partitioning factors are not sampled to ensure that they add up to 1.0 for any single run within a

probabilistic calculation. This is not necessary for the purpose of this anlaysis because each

scenario calculates dose from exposure to only one material at a time.

&RPSDULVRQRI3DUWLWLRQLQJ)DFWRUVZLWK3XEOLVKHG6WXGLHV

A comparison of the partitioning factors presented above to experimental information on

partitioning was done in order to help establish their validity. The comparison was limited to

those studies that presented results from actual experimental meltings of radioactively

contaminated metal. One exception to this was Copeland (Copeland et al. 1978) who used a

non-experimental thermodynamic approach similar to this study. However, dust was not

included in the Copeland study, and elements were partitioned between slag and the metal

product only. Articles that did not present enough data to determine partitioning were not

included. The literature reviewed had information on only a limited number of elements—most

commonly cobalt and cesium— probably because these are most likely to be involved in

accidental melting of sealed sources. 

In general, the results presented in previous studies support the grouping and partitioning factors

developed herein. Even though partitioning values do not agree exactly, the overall grouping is

supported. The differences between the previous studies and partitioning factors and groupings

developed for this study are mainly due to the different assumptions used (e.g., type of furnace

used, purpose of refining). The purpose of some experiments was to decontaminate the metal
Section 4 Recycle and Disposal of Steel

4-23 NUREG-1640

0 ' 0 % 01& 4.1

and force the radionuclides to the slag. This is different than the assumption used in this report

(normal refining operations and no decontamination). In some cases the assumptions used were

not stated in the study, so an accurate interpretation and comparison of the partitioning data was

impossible.

0DWKHPDWLFDO0RGHOIRU)ORZRI5HF\FOHG6WHHO6FUDS

This section presents the equations that comprise the mathematical model of the information

presented previously in Sections 4.2 and 4.3. The equations are used to estimate radionuclide

concentrations in refined steel and other co-products of refining. For calculation, the equations

are entered in spreadsheets that have been organized and structured specifically for this analysis. 

The calculated radionuclide concentrations in refined steel, refinery slag, refinery baghouse dust,

and the activity released out the refinery stack are used as input to the scenario analyses described

in Section 4.6.

6FUDS0L[LQJ

There are two processes by which the original concentration of each radionuclide in steel scrap is

potentially changed. The first can occur upon mixing with other scrap metal prior to refining. 

This mixing is a radionuclide-independent process, so the radioactivity concentration of all

radionuclides is affected the same when mixing with a given mass of non-contaminated scrap

steel. The second process is the refining process itself, which generally consists of the melting of

steel scrap metal and the resulting redistribution (partitioning) of mass and radioactivity. 

Partitioning of mass during refining is radionuclide-independent, however partitioning of

radioactivity during refining is element-dependent. The following equations are used to calculate

the radionuclide concentrations in refinery co-products at those points in the material flow which

correspond to potential exposure scenarios.

The first change in radioactivity concentration occurs if the cleared scrap from the nuclear facility

is mixed with other metal prior to melting. There are actually two potential places that mixing

can occur: at the scrap dealer (i.e., secondary metal pool) and in the primary metal pool at the

refinery furnace. For simplicity, these two mixings were treated as a single potential dilution. 

This mixing is modeled using appropriate ranges for the masses of cleared and other scrap

entering a refinery furnace. These masses were derived for both EAFs and BOFs and are listed in

Appendix B. The total mass of scrap entering the furnace in a year was calculated using

Equation 4.1.

where

M1 = total mass of scrap metal entering the furnace per charge (g/charge)

and

M0 = mass of cleared material entering the furnace per charge (g/charge)

MNC = mass of non-contaminated scrap metal entering the furnace per charge (g/charge)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-24

& ' 0

0

( & 4.2

0V ' 0 ( I

V ( &3< 4.3

0G ' 0 ( I

G ( &3< 4.4

0

S ' 0 ( IS ( &3< 4.5

The radionuclide concentration in the metal entering the furnace was calculated using

Equation 4.2. The original radioactivity concentration, C0 , is reduced by the ratio of the mass of

cleared scrap entering the furnace to the total mass of material entering the furnace. The

following equations are intended to be evaluated separately for each radionuclide in the analysis. 

However, parameters such as concentration and other radionuclide-specific parameters are not

explicitly subscripted in the equations.

Where

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

and

M0 = mass of cleared material entering the furnace per charge (g/charge)

M1 = total mass of scrap metal entering the furnace per charge (g/charge)

C0 = original radionuclide concentration in cleared material (pCi/g)

For slag, baghouse dust, and off-gas, Equations 4.1 and 4.2 were evaluated using annual average

values for the masses of scrap input to the furnaces, because all of the exposure scenarios for

these materials depend on annual average radionuclide concentrations. For metal, both an annual

average and a single charge evaluation of Equations 4.1 and 4.2 were conducted. This was done

for metal because there are metal products that could easily be manufactured from a single

refinery charge. The single charge radionuclide concentrations were used in metal product use

exposure scenarios except where noted. (See Appendix D for additional details.)

5HILQHU\3URFHVV

To accurately account for the changes in radionuclide concentration in the different products, the

mass of each refinery product must be calculated independent of radionuclide activity. Equations

4.3, 4.4, and 4.5 were used to calculate the masses of slag, dust, and metal product, respectively.
Section 4 Recycle and Disposal of Steel

4-25 NUREG-1640

&V' & ( I

V ( 0

0 ( I

V

' & ( I

V

I

V

4.6

&G' & ( I

G

I

G

4.7

&

S' & ( I

S

I

S

4.8

where

Ms = mass of slag produced from a refinery per year (g)

Md = mass of dust produced from a refinery per year (g)

Mp = mass of metal product produced from a refinery per year (g)

and

M1 = total mass of scrap entering the furnace per charge (g/charge)

fs1 = mass partitioning factor for slag during the refining process (dimensionless)

fd1 = mass partitioning factor for dust during the refining process (dimensionless)

fp1 = mass partitioning factor for metal product during the refining process

(dimensionless)

CPY = number of charges per refinery per year (charge)

The radioactivity in the original scrap metal entering the furnace during the refining process is

partitioned into four products. Equation 4.6 shows the calculation of the concentration of

radionuclides in slag, taking into account both the mass and elemental partitioning factors.

where

Cs = radionuclide concentration in slag after the refining process (pCi/g)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

fs = slag elemental partitioning factor during the refining process (dimensionless)

M1 = total mass of scrap entering the furnace per charge (g/charge)

fs1 = mass partitioning factor for slag during the refining process (dimensionless)

The concentration of radionuclides in the dust and metal product are calculated using Equations

4.7 and 4.8, respectively.

where

Cd = radionuclide concentration in dust after the refining process (pCi/g)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

fd = dust elemental partitioning factor during the refining process(dimensionless)

fd1 = mass partitioning factor for dust during the refining process (dimensionless)

where

Cp = radionuclide concentration in metal product after the refining process (pCi/g)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-26

$

J ' & ( 0 ( IJ ( &3< 4.9

0UD ' 0G (  & %+HII 4.10

0GE ' 0G & 0UD 4.11

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

fp = metal product elemental partitioning factor during the refining process

(dimensionless)

fp1 = mass partitioning factor for metal product during the refining process

(dimensionless)

Because there is no mass associated with the refinery off-gas, the total quantity of radioactivity

was calculated instead of a concentration. The off-gas radioactivity was calculated using

Equation 4.9 using only the elemental partitioning factor (i.e., no mass partitioning factor). This

radioactivity is calculated on an annual basis. 

where

Ag = radioactivity in the off-gases leaving the refinery stack in a year (pCi)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

M1 = total mass of scrap entering the furnace per charge (g/charge)

fg = off-gas elemental partitioning factor during the refining process (dimensionless)

CPY = number of charges per refinery per year (charge)

Equations 4.10 and 4.11 were used to calculate the mass of dust that escapes the baghouse filters,

and that which is captured in the baghouse, respectively. 

where

Mra = total mass of dust that escapes the baghouse in a year (g)

and

Md = mass of dust produced from the refining process in a year (g)

BHeff = baghouse efficiency (dimensionless)

where

Mdb = total mass of dust captured in the refinery baghouse in a year (g)

and

Md = mass of dust produced from the refining process in a year (g)

Mra = total mass of dust that escapes the baghouse in a year (g)
Section 4 Recycle and Disposal of Steel

4-27 NUREG-1640

0+ ' 0GE ( I

+ 4.12

0W+ ' 0+DGG % 0+ 4.13

&+ ' &G ( GI+ 4.14

($)'XVW+D]DUGRXV/DQGILOO

A certain percentage of the EAF dust produced by the steel industry each year is treated for direct

disposal in a hazardous landfill. During this immobilization treatment, dilution of the EAF dust

is the only process modeled. The mass of EAF dust that is sent to hazardous landfills in a year is

represented by Equation 4.12. The total mass of material entering the immobilization process in

a year is calculated using Equation 4.13. The radioactivity concentration in the treated dust when

it is placed in a hazardous landfill is calculated using Equation 4.14.

Where

MH = mass of contaminated EAF dust sent to a hazardous landfill in a year (g)

MtH = total mass of material entering the immobilization process in a year (g)

CH = radionuclide concentration in immobilized dust (pCi/g)

and

Mdb = total mass of dust captured in the refinery baghouse in a year (g)

fH = annual fraction of total EAF dust that is sent to hazardous landfills (dimensionless)

MH,add = mass of additives used in the immobilization process in a year (g)

Cd = radionuclide concentration in dust after the refining process (pCi/g)

dfH = dilution factor for immobilization process (dimensionless)

5DGLRDFWLYLW\&RQFHQWUDWLRQVLQ6WHHO5HILQLQJ&RSURGXFWV

The values listed in Table 4.6 are calculated radioactivity concentrations at an EAF refinery and

Table 4.7 for a BOF refinery. The values are normalized to a unit radioactivity concentration in

scrap, and are listed in S.I. units. The values are numerically identical if expressed in

conventional units (e.g., pCi/g product per pCi/g scrap).

'RVH$VVHVVPHQWIRU6WHHO5HF\FOHDQG'LVSRVDO
Recycle and Disposal of Steel Section 4

NUREG-1640 4-28

*HQHUDO'HVFULSWLRQRI5HF\FOH6FHQDULRV

General categories of scenarios were established to organize and simplify the evaluation and

analysis of potential exposure scenarios. Because of the logical link between material flow

models and potential exposure scenarios, the categories were derived from the steel scrap

material flow model (Figure 4.1). Analysis of material characteristics and human behavior at

certain points in the flow model identified six logical scenario categories for the evaluation: 

handling and processing (individual atmospheric releases), storage, product use, transportation,

disposal activities, and resident on closed landfill scenarios. 

Exposure conditions for scenarios not in these identified categories would be similar to those in

the selected categories, and can be reasonably approximated by the evaluation of the categories

chosen for evaluation. Consistent with the goals of the analysis, the exposure categories were

selected to simplify the evaluation without limiting its comprehensiveness. 

The following sections briefly describe the exposure pathways included in the recycle scenario

analyses, followed by a description of the six general categories that the exposure scenarios fall

into. Starting with handling at a scrap yard, through processing and use, to disposal and postclosure of a landfill, the categories encompass a “cradle to grave” picture of recycle of steel

cleared from a NRC licensed facility. The scenarios can be divided into two broad categories

work related and non-work related. Work related exposure scenarios, obviously, would be

limited to workers exposed to recycled material during the course of their workday. Non-work

related exposure scenarios describe situations where the general public might come in contact

with recycled material as consumers or as part of daily activities not directly associated with

employment. Some scenario categories contain both worker and non-worker exposure scenarios.

There are 31 exposure scenarios listed in Table 4.8. Of these, only 27 were used for the

determination of critical groups. The four landfill resident scenarios were judged to be too

unlikely to use in the critical group determination, but were analyzed for completeness. A

summary of the highest mean dose factors for the landfill resident scenarios is included in

Appendix J.

Table 4.6 Results of material flow model—steel electric arc furnace

Mean radionuclide concentrations in refinery products (Bq/g per Bq/g scrap)

Refined metal Off-gas

Nuclide Single charge Annual Slag Dust (Bq per Bq/g)

H-3 3.1E-02 2.3E-03 0.0E+00 0.0E+00 3.4E+10

C-14 9.2E-01 7.0E-02 1.5E-03 4.3E-02 0.0E+00

Na-22 3.1E-03 2.3E-04 2.1E-01 1.9E+00 1.2E+09

P-32 3.2E-02 2.4E-03 1.9E-01 2.1E+00 0.0E+00

S-35 9.4E-02 7.0E-03 1.6E-01 2.2E+00 0.0E+00

Cl-36 6.2E-03 4.7E-04 1.0E-01 1.3E+00 1.6E+10

K-40 3.1E-03 2.4E-04 1.1E-01 3.2E+00 0.0E+00

Ca-41 3.1E-03 2.4E-04 4.1E-01 8.6E-02 0.0E+00
Section 4 Recycle and Disposal of Steel

Table 4.6 Results of material flow model—steel electric arc furnace

Mean radionuclide concentrations in refinery products (Bq/g per Bq/g scrap)

Refined metal Off-gas

Nuclide Single charge Annual Slag Dust (Bq per Bq/g)

4-29 NUREG-1640

Ca-45 3.2E-03 2.4E-04 4.1E-01 8.3E-02 0.0E+00

Cr-51 7.0E-01 5.2E-02 1.1E-01 2.9E-02 0.0E+00

Mn-54 3.5E-01 2.6E-02 2.6E-01 7.1E-02 0.0E+00

Fe-55 9.1E-01 6.9E-02 9.7E-03 4.3E-02 0.0E+00

Co-57 9.2E-01 7.0E-02 1.4E-03 4.3E-02 0.0E+00

Co-58 9.2E-01 7.0E-02 1.4E-03 4.3E-02 0.0E+00

Fe-59 9.1E-01 6.9E-02 9.6E-03 4.3E-02 0.0E+00

Ni-59 9.2E-01 7.0E-02 1.4E-03 4.3E-02 0.0E+00

Co-60 9.2E-01 7.0E-02 1.3E-03 4.3E-02 0.0E+00

Ni-63 9.2E-01 7.0E-02 1.4E-03 4.2E-02 0.0E+00

Zn-65 9.4E-02 7.0E-03 1.4E-03 3.9E+00 0.0E+00

Cu-67 9.2E-01 7.0E-02 1.4E-03 4.4E-02 0.0E+00

Se-75 3.8E-01 2.9E-02 2.0E-01 1.7E+00 0.0E+00

Sr-85 3.1E-03 2.4E-04 4.1E-01 8.5E-02 0.0E+00

Sr-89 3.1E-03 2.4E-04 4.1E-01 8.8E-02 0.0E+p0

Sr-90 3.1E-03 2.4E-04 4.1E-01 8.6E-02 0.0E+00

Y-91 3.2E-03 2.5E-04 4.1E-01 8.5E-02 0.0E+00

Mo-93 9.2E-01 7.0E-02 1.4E-03 4.3E-02 0.0E+00

Nb-93m 3.1E-03 2.3E-04 4.1E-01 8.7E-02 0.0E+00

Nb-94 3.1E-03 2.4E-04 4.1E-01 8.6E-02 0.0E+00

Nb-95 3.1E-03 2.4E-04 4.1E-01 8.6E-02 0.0E+00

Zr-95 3.1E-03 2.4E-04 4.1E-01 8.6E-02 0.0E+00

Tc-99 9.2E-01 7.0E-02 1.4E-03 4.3E-02 0.0E+00

Ru-103 9.2E-01 7.0E-02 1.4E-03 4.3E-02 0.0E+00

Ru-106 9.2E-01 7.0E-02 1.4E-03 4.3E-02 0.0E+00

Ag-108m 9.2E-01 7.0E-02 1.3E-03 4.3E-02 0.0E+00

Cd-109 3.1E-03 2.3E-04 1.1E-02 4.2E+00 0.0E+00

Ag-110m 9.2E-01 7.0E-02 1.4E-03 4.4E-02 0.0E+00

Sb-124 8.5E-01 6.4E-02 4.1E-02 1.4E-02 0.0E+00

I-125 0.0E+00 0.0E+00 0.0E+00 0.0E+00 3.6E+10

Sb-125 8.5E-01 6.4E-02 4.2E-02 1.4E-02 0.0E+00

I-129 0.0E+00 0.0E+00 0.0E+00 0.0E+00 3.6E+10

I-131 0.0E+00 0.0E+00 0.0E+00 0.0E+00 3.6E+10

Ba-133 3.2E-03 2.4E-04 4.1E-01 8.5E-02 0.0E+00

Cs-134 3.1E-03 2.3E-04 1.1E-02 4.2E+00 0.0E+00

Cs-137 3.2E-03 2.3E-04 1.1E-02 4.2E+00 0.0E+00

Ce-141 3.1E-03 2.4E-04 4.1E-01 8.7E-02 0.0E+00

Ce-144 3.1E-03 2.4E-04 4.1E-01 8.4E-02 0.0E+00

Pm-147 3.2E-03 2.5E-04 4.1E-01 8.7E-02 0.0E+00

Eu-152 3.1E-03 2.4E-04 4.1E-01 8.4E-02 0.0E+00

Eu-154 3.1E-03 2.4E-04 4.1E-01 8.7E-02 0.0E+00

Eu-155 3.2E-03 2.4E-04 4.1E-01 8.7E-02 0.0E+00

Re-186 4.6E-01 3.5E-02 8.3E-03 2.1E+00 0.0E+00

Ir-192 4.7E-01 3.7E-02 8.4E-03 2.2E+00 0.0E+00
Recycle and Disposal of Steel Section 4

Table 4.6 Results of material flow model—steel electric arc furnace

Mean radionuclide concentrations in refinery products (Bq/g per Bq/g scrap)

Refined metal Off-gas

Nuclide Single charge Annual Slag Dust (Bq per Bq/g)

NUREG-1640 4-30

Pb-210 2.2E-02 1.7E-03 9.6E-03 4.2E+00 0.0E+00

Po-210 3.1E-03 2.3E-04 1.1E-02 4.2E+00 0.0E+00

Bi-210 1.2E-01 8.8E-03 5.2E-02 3.2E+00 1.2E+09

Rn-222 0.0E+00 0.0E+00 0.0E+00 0.0E+00 3.6E+10

Ra-223 1.9E-02 1.5E-03 4.1E-01 8.6E-02 0.0E+00

Ra-224 1.9E-02 1.4E-03 4.1E-01 8.6E-02 0.0E+00
Section 4 Recycle and Disposal of Steel

Table 4.6 Results of material flow model—steel electric arc furnace

Mean radionuclide concentrations in refinery products (Bq/g per Bq/g scrap)

Refined metal Off-gas

Nuclide Single charge Annual Slag Dust (Bq per Bq/g)

4-31 NUREG-1640

Ac-225 3.1E-03 2.4E-04 4.1E-01 8.6E-02 0.0E+00

Ra-225 1.9E-02 1.5E-03 4.1E-01 8.6E-02 0.0E+00

Ra-226 1.9E-02 1.4E-03 4.1E-01 8.8E-02 0.0E+00

Ac-227 3.1E-03 2.3E-04 4.1E-01 8.7E-02 0.0E+00

Th-227 3.1E-03 2.4E-04 4.1E-01 8.7E-02 0.0E+00

Th-228 3.1E-03 2.3E-04 4.1E-01 9.0E-02 0.0E+00

Ra-228 1.9E-02 1.4E-03 4.1E-01 8.4E-02 0.0E+00

Th-229 3.1E-03 2.4E-04 4.1E-01 8.5E-02 0.0E+00

Th-230 3.1E-03 2.4E-04 4.1E-01 8.6E-02 0.0E+00

Pa-231 3.2E-03 2.3E-04 4.1E-01 8.5E-02 0.0E+00

Th-231 3.2E-03 2.4E-04 4.1E-01 8.8E-02 0.0E+00

Th-232 3.1E-03 2.3E-04 4.1E-01 8.7E-02 0.0E+00

Pa-233 3.1E-03 2.3E-04 4.1E-01 8.6E-02 0.0E+00

U-233 3.2E-03 2.4E-04 4.1E-01 8.8E-02 0.0E+00

Th-234 3.1E-03 2.4E-04 4.1E-01 8.5E-02 0.0E+00

U-234 3.2E-03 2.4E-04 4.1E-01 8.6E-02 0.0E+00

U-235 3.2E-03 2.4E-04 4.1E-01 8.7E-02 0.0E+00

Np-237 3.1E-03 2.4E-04 4.1E-01 8.4E-02 0.0E+00

Pu-238 3.1E-03 2.4E-04 4.1E-01 8.5E-02 0.0E+00

U-238 3.1E-03 2.4E-04 4.1E-01 8.6E-02 0.0E+00

Pu-239 3.1E-03 2.4E-04 4.1E-01 8.5E-02 0.0E+00

Pu-240 3.1E-03 2.4E-04 4.1E-01 8.5E-02 0.0E+00

Pu-241 3.2E-03 2.3E-04 4.1E-01 8.5E-02 0.0E+00

Am-241 3.2E-03 2.3E-04 4.1E-01 8.3E-02 0.0E+00

Cm-242 3.1E-03 2.4E-04 4.1E-01 8.5E-02 0.0E+00

Pu-242 3.2E-03 2.3E-04 4.1E-01 8.5E-02 0.0E+00

Cm-244 3.2E-03 2.4E-04 4.1E-01 8.8E-02 0.0E+00
Recycle and Disposal of Steel Section 4

NUREG-1640 4-32

Table 4.7 Results of material flow model—for steel basic oxygen furnace

Mean radionuclide concentrations in refinery products (Bq/g per Bq/g scrap)

Refined metal Off-gas

Nuclide Single charge Annual Slag Dust (Bq per Bq/g)

H-3 1.0E-02 6.9E-03 0.0E+00 0.0E+00 2.2E+10

C-14 3.0E-01 2.0E-01 2.6E-03 1.5E-01 0.0E+00

Na-22 1.0E-03 6.7E-04 4.0E-01 6.6E+00 7.7E+08

P-32 1.0E-02 6.7E-03 3.7E-01 7.2E+00 0.0E+00

S-35 3.0E-02 2.0E-02 3.3E-01 7.3E+00 0.0E+00

Cl-36 2.0E-03 1.4E-03 2.0E-01 4.3E+00 1.1E+10

K-40 1.0E-03 6.8E-04 2.1E-01 1.1E+01 0.0E+00

Ca-41 1.0E-03 6.8E-04 7.9E-01 3.0E-01 0.0E+00

Ca-45 1.0E-03 6.7E-04 7.9E-01 3.0E-01 0.0E+00

Cr-51 2.2E-01 1.5E-01 2.0E-01 9.7E-02 0.0E+00

Mn-54 1.1E-01 7.7E-02 5.0E-01 2.4E-01 0.0E+00

Fe-55 2.9E-01 2.0E-01 1.9E-02 1.5E+00 0.0E+00

Co-57 3.0E-01 2.0E-01 2.7E-03 1.5E-01 0.0E+00

Co-58 3.0E-01 2.0E-01 2.7E-03 1.4E-01 0.0E+00

Fe-59 2.9E-01 2.0E-01 1.9E-02 1.4E+00 0.0E+00

Ni-59 3.0E-01 2.0E-01 2.6E-03 1.5E-01 0.0E+00

Co-60 3.0E-01 2.0E-01 2.7E-03 1.5E-01 0.0E+00

Ni-63 3.0E-01 2.0E-01 2.7E-03 1.5E-01 0.0E+00

Zn-65 3.0E-02 2.0E-02 2.7E-03 1.3E+01 0.0E+00

Cu-67 3.0E-01 2.0E-01 2.7E-03 1.4E-01 0.0E+00

Se-75 1.2E-01 8.2E-02 3.9E-01 5.8E+00 0.0E+00

Sr-85 1.0E-03 6.8E-04 7.9E-01 3.0E-01 0.0E+00

Sr-89 1.0E-03 6.8E-04 7.9E-01 2.9E-01 0.0E+00

Sr-90 1.0E-03 7.1E-04 7.9E-01 2.9E-01 0.0E+00

Y-91 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

Mo-93 3.0E-01 2.0E-01 2.7E-03 1.5E-01 0.0E+00

Nb-93m 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

Nb-94 1.0E-03 6.9E-04 7.9E-01 3.0E-01 0.0E+00

Nb-95 1.0E-03 7.0E-04 7.9E-01 3.0E-01 0.0E+00

Zr-95 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

Tc-99 3.0E-01 2.0E-01 2.6E-03 1.4E-01 0.0E+00

Ru-103 3.0E-01 2.0E-01 2.6E-03 1.5E-01 0.0E+00

Ru-106 3.0E-01 2.0E-01 2.7E-03 1.4E-01 0.0E+00

Ag-108m 3.0E-01 2.0E-01 2.7E-03 1.5E-01 0.0E+00

Cd-109 1.0E-03 6.9E-04 2.1E-02 1.4E+01 0.0E+00

Ag-110m 3.0E-01 2.0E-01 2.7E-03 1.5E-01 0.0E+00

Sb-124 2.7E-01 1.9E-01 8.2E-02 4.7E-02 0.0E+00

I-125 0.0E+00 0.0E+00 0.0E+00 0.0E+00 2.3E+10

Sb-125 2.7E-01 1.9E-01 7.9E-02 4.8E-02 0.0E+00

I-129 0.0E+00 0.0E+00 0.0E+00 0.0E+00 2.3E+10

I-131 0.0E+00 0.0E+00 0.0E+00 0.0E+00 2.3E+10

Ba-133 1.0E-03 6.8E-04 7.9E-01 2.9E-01 0.0E+00

Cs-134 1.0E-03 6.9E-04 2.1E-02 1.4E+01 0.0E+00

Cs-137 1.0E-03 6.9E-04 2.2E-02 1.4E+01 0.0E+00
Section 4 Recycle and Disposal of Steel

Table 4.7 Results of material flow model—for steel basic oxygen furnace

Mean radionuclide concentrations in refinery products (Bq/g per Bq/g scrap)

Refined metal Off-gas

Nuclide Single charge Annual Slag Dust (Bq per Bq/g)

4-33 NUREG-1640

Ce-141 1.0E-03 7.0E-04 7.9E-01 2.9E-01 0.0E+00

Ce-144 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

Pm-147 1.0E-03 7.0E-04 7.9E-01 3.0E-01 0.0E+00

Eu-152 1.0E-03 6.8E-04 7.9E-01 2.9E-01 0.0E+00

Eu-154 1.0E-03 7.0E-04 7.9E-01 2.9E-01 0.0E+00

Eu-155 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

Re-186 1.5E-01 1.0E-01 1.6E-02 7.3E+00 0.0E+00

Ir-192 1.5E-01 1.0E-01 1.6E-02 7.2E+00 0.0E+00

Pb-210 7.0E-03 4.8E-03 1.8E-02 1.4E+01 0.0E+00

Po-210 1.0E-03 6.9E-04 2.1E-02 1.4E+01 0.0E+00

Bi-210 3.8E-02 2.6E-02 1.0E-01 1.1E+01 7.6E+08

Rn-222 0.0E+00 0.0E+00 0.0E+00 0.0E+00 2.3E+10

Ra-223 6.0E-03 4.1E-03 7.9E-01 3.0E-01 0.0E+00

Ra-224 6.0E-03 4.1E-03 7.9E-01 3.0E-01 0.0E+00

Ac-225 1.0E-03 6.7E-04 7.9E-01 2.9E-01 0.0E+00

Ra-225 6.0E-03 4.1E-03 7.9E-01 2.9E-01 0.0E+00

Ra-226 6.1E-03 4.0E-03 7.9E-01 2.9E-01 0.0E+00

Ac-227 9.8E-04 6.7E-04 7.9E-01 2.9E-01 0.0E+00

Th-227 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

Th-228 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

Ra-228 6.1E-03 4.2E-03 7.9E-01 3.0E-01 0.0E+00

Th-229 1.0E-03 7.0E-04 7.9E-01 2.9E-01 0.0E+00

Th-230 1.0E-03 6.8E-04 7.9E-01 2.9E-01 0.0E+00

Pa-231 1.0E-03 6.8E-04 7.9E-01 3.0E-01 0.0E+00

Th-231 1.0E-03 7.0E-04 7.9E-01 3.0E-01 0.0E+00

Th-232 1.0E-03 6.9E-04 7.9E-01 3.0E-01 0.0E+00

Pa-233 1.0E-03 6.7E-04 7.9E-01 2.9E-01 0.0E+00

U-233 1.0E-03 6.7E-04 7.9E-01 2.9E-01 0.0E+00

Th-234 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

U-234 9.9E-04 6.9E-04 7.9E-01 2.9E-01 0.0E+00

U-235 1.0E-03 6.8E-04 7.9E-01 2.9E-01 0.0E+00

Np-237 1.0E-03 6.8E-04 7.9E-01 2.9E-01 0.0E+00

Pu-238 1.0E-03 6.8E-04 7.9E-01 2.9E-01 0.0E+00

U-238 1.0E-03 7.0E-04 7.9E-01 3.0E-01 0.0E+00

Pu-239 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

Pu-240 1.0E-03 7.1E-04 7.9E-01 2.9E-01 0.0E+00

Pu-241 1.0E-03 7.1E-04 7.9E-01 3.0E-01 0.0E+00

Am-241 1.0E-03 6.8E-04 7.9E-01 2.8E-01 0.0E+00

Cm-242 1.0E-03 6.9E-04 7.9E-01 2.9E-01 0.0E+00

Pu-242 1.0E-03 7.1E-04 7.9E-01 3.0E-01 0.0E+00

Cm-244 1.0E-03 6.7E-04 7.9E-01 2.9E-01 0.0E+00
Recycle and Disposal of Steel Section 4

NUREG-1640 4-34

Table 4.8 Scenario and exposure pathway matrix

Scenario title and abbreviation for steel

Exposure pathwaysa

Ext Inh Sec DW Ing

Handling and Processing Scenarios

Handling scrap metal at the scrapyard, FE-SCRP-HANDLIN-W 1  

Handling slag at the refinery, FE-SLAG-HANDLIN-W F1  

Refinery baghouse operations, FE-EAFD-BAGHOUS-W 8  

Handling EAF dust at the refinery, FE-EAFD-HANDLIN-W 9  

Handling refined metal product at the refinery, FE-METL-HANDREF-W 2  

Handling BOF refined metal during product manufacturing, FE-BOFM-HANDMAN-W 2  

Handling EAF refined metal product during distribution, FE-METL-HANDDIS-W 2

Processing EAF dust for disposal, FE-EAFD-PROCESS-W 1  

Processing slag for use as aggregate or as roadbed, FE-SLAG-PROCESS-W 1  

Atmospheric release during refining, FE-ATMO-REFINER-N F2  

Storage Scenario

Storage of slag at the refinery, FE-SLAG-STORAGE-N 

Transport Scenarios

Transport of scrap metal, FE-SCRP-TRANSPO-W 4

Transport of slag, FE-SLAG-TRANSPO-W 4

Transport of untreated EAF dust, FE-EAFD-TRANSPO-W 4

Transport of refined metal product, FE-METL-TRANSPO-W 4

Disposal Scenarios

Disposal of BOF dust in a sanitary landfill, FE-BOFD-DISPOSL-W F1  

Disposal of refinery slag in a sanitary landfill, FE-SLAG-DISPOSL-W F1  

Disposal of scrap metal in a sanitary landfill, FE-SCRP-DISPOSL-W F1

Disposal of EAF dust in a hazardous waste landfill, FE-EAFD-DISPOSL-W F1

Product Use Scenarios

Road construction activities using refinery slag, FE-SLAG-ROADBED-W F1  

In proximity of a large metal mass, FE-METL-LGMASS-N 2

In proximity of a small metal mass, FE-METL-SMMASS-N 3

Small steel mass close to the body, FE-METL-SMOBJCT-N 6

Inside an automobile, FE-METL-VEHICLE-N 11

Inside a building structure, FE-METL-BLDGSTR-N 10

Use of slag as aggregate in basement construction, FE-SLAG-CONCBAS-N 7

Use of slag in a roadbed, FE-SLAG-ROADBED-N F1
Section 4 Recycle and Disposal of Steel

Table 4.8 Scenario and exposure pathway matrix

Scenario title and abbreviation for steel

Exposure pathwaysa

Ext Inh Sec DW Ing

4-35 NUREG-1640

Landfill Resident Scenarios

Resident on a closed landfill after disposal of BOF dust, FE-BOFD-LANDFIL-N F1  

Resident on a closed landfill after disposal of refinery slag, FE-SLAG-LANDFIL-N F1  

Resident on a closed landfill after disposal of scrap metal, FE-SCRP-LANDFIL-N F1  

Resident on a closed landfill after disposal of EAF dust, FE-EAFD-LANDFIL-N F1  

a. Ext = external, Inh = inhalation, Sec = secondary ingestion, Ing = ingestion of food (plants), DW = drinking

water ingestion.

b. These landfill resident scenarios were analyzed, but were not included in the determination of critical groups. A

dose summary is included in Appendix J.

1 External dose based on geometry factor #1 (large pile)

2 External dose based on geometry factor #2 (large metal object)

3 External dose based on geometry factor #3 (small metal object)

4 External dose based on geometry factor #4 (driver of truck)

5 External dose based on geometry factor #5 (beside truck)

6 External dose based on geometry factor #6 (small metal object close to body)

7 External dose based on geometry factor #7 (inside a structure)

8 External dose based on geometry factor #8 (inside refinery baghouse)

9 External dose based on geometry factor #9 (on top of bag house dust truck)

10 External dose based on geometry factor #10 (steel-framed structure)

11 External dose based on geometry factor #11 (inside an automobile)

F1 External dose based on Federal Guidance Report # 12 values (soil contaminated to an infinite depth)

F2 External dose based on Federal Guidance Report # 12 values (contaminated ground surface)

Exposure Pathways

The characteristics and behavior of the radionuclides in recycled material will also determine the

potential exposure pathways. For example, gamma-emitting radionuclides will present an

external exposure potential, whereas alpha-emitting radionuclides will not. Three main exposure

pathways have been identified for this study: external exposure, inhalation, and ingestion. Each

pathway has been subdivided into more specific pathways for modeling purposes. Exposure

scenarios were modeled by combinations of various exposure pathways. The exposure pathways

that were included in each exposure scenario are shown in Table 4.8.

Each scenario description includes an identification of the pathways most likely to result in

exposure to the individual(s) evaluated. Although other exposure pathways for many of the

scenarios are theoretically possible, they were not included because the probability of them

occurring to a significant extent is very low. For example, doses resulting from external

exposure to resuspended dust would be insignificant compared to doses from external exposure

to the volume source itself. Those pathways that are unlikely—or that represent comparatively

insignificant exposure—are not included.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-36

Of the many possible exposure pathways that could be identified for reuse and recycle exposure

scenarios, a comprehensive set of five potentially important pathways has been used for this

analysis. The five exposure pathways are described below.

External exposure to penetrating radiation—The source material containing radionuclides that

emit penetrating radiation can include volume sources, such as piles of scrap metal or slag,

refinery baghouse structures, large or small metal products made from refined steel, or transport

containers. Plane sources, such as from disposed metal, baghouse dust, or slag are also included.

Inhalation exposure to airborne radionuclides—This pathway includes inhalation of material

resuspended from surfaces during handling, processing, and disposal activities; atmospheric

releases from refineries; and selected product use activities. Source material includes dust, soil

slag, and fine particulates from metal-cutting operations.

Secondary ingestion of surface contamination—This exposure pathway addresses inadvertent

ingestion of surface sources of material (dust, soil, slag, and metal shavings). Except for two

exceptions, this pathway is included whenever the inhalation pathway is present and is based on

the same source material as the inhalation pathway. (The scenarios addressing atmospheric

releases from a refinery and resident on a closed landfill do not include secondary ingestion.)

Ingestion of food and soil—This exposure pathway is the conventional food consumption

pathway (vegetables), plus direct ingestion of soil.

Drinking water ingestion—This exposure pathway addresses the consumption (ingestion) of

drinking water extracted from a groundwater source (i.e., a well).

:RUN5HODWHG6FHQDULRV

The exposure scenario categories that are work related are:

C handling

C processing

C storage

C product use

C transport

C disposal scenarios.

+DQGOLQJ6FHQDULRV

After clearance from a NRC licensed facility, if the material is for recycle or disposal, scrap and

refinery byproducts (slag, dust, metal product) must be handled in a number of work related

settings. A variety of work related conditions and practices were analyzed to identify the most

likely exposure scenarios. This included investigating the details of work-related settings to

develop accurate and representative scenarios and to assign realistic values (and ranges) to
Section 4 Recycle and Disposal of Steel

4-37 NUREG-1640

exposure parameters. During scenario development, details were periodically re-examined to

ensure that appropriate scenarios were identified and completely described.

The handling scenarios analyzed for this report encompass a representative range of work related

activities associated with handling scrap and refinery byproducts in a number of work related

settings. 

C Handling scrap metal at the scrapyard

C Handling slag at refinery

C Refinery baghouse operations

C Handling EAF dust at the mill

C Handling of refined metal product at the mill

C Handling BOF refined metal product during manufacturing

C Handling EAF refined metal product during distribution.

+DQGOLQJ6FUDS0HWDODWWKH6FUDS\DUG

Following clearance from a NRC licensed facility, scrap metal would be transported to a scrap

yard, where it would be unloaded, processed, and prepared for shipment to a refinery. This

scenario addresses activities that require scrap yard workers to be in proximity to the scrap metal. 

These activities include unloading, sorting, cutting (sizing), shredding, baling, and loading for

shipment. The individual evaluated in this scenario is assumed to perform several of these

activities.

Cutting and shredding processes used on scrap metal can generate airborne particulates. This is a

result of the mechanical and chemical (torch) techniques used on the scrap. These airborne

particulates can settle and be inadvertently ingested by workers. This is the basis for including

inhalation and secondary ingestion exposure pathways.

Exposure pathways: Because of the variety of operations involved at the scrap yard, internal, as

well as external exposure pathways are included in this scenario evaluation. 

External: Proximity to incoming or piled scrap metal could result in external exposure to

penetrating radiation from the volume source (scrap pile). 

Inhalation: The various processing methods used (e.g., cutting and shredding) could result in

resuspended metal particulates from the scrap metal, resulting in inhalation exposure.

Secondary Ingestion: Suspended metal particulates created from processing could be deposited

on surfaces, causing inadvertent ingestion from contaminated hands and food.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-38

+DQGOLQJ6ODJDW5HILQHU\

Refinery slag is handled at the refinery in preparation for processing or use, potentially subjecting

workers to exposure. In this scenario, the slag is in a very large pile and a front-end loader is

used to move it. This would involve driving a loader around and on top of the pile. Since the

driver is subject to the greatest potential exposure, this is the individual evaluated.

Exposure Pathways:

External: The worker would receive external exposure from the slag pile.

Inhalation: Exposure to suspended slag in the vicinity of the slag pile.

Secondary Ingestion: Inadvertent ingestion of surface contamination.

5HILQHU\%DJKRXVH2SHUDWLRQV

Normal operations of a steel refinery require routine and non-routine maintenance of the

baghouse and baghouse filters, requiring workers to spend time near the exterior of the baghouse

and inside the baghouse that encloses the filters. Typical operations near the exterior of the

baghouse include routine inspections of the baghouse structure, ductwork, fans, and other parts

of the ventilation and filter system. Typical operations inside the baghouse include inspection,

repair, and replacement of filter bags and inspection and maintenance of other components of the

dust removal system, such as seals, valves, and shaker mechanisms. The individual evaluated in

this scenario is the worker performing routine inspections and maintenance, as well as nonroutine operations, in and around the refinery baghouse.

A larger percentage of the charge at an EAF refinery would be comprised of scrap metal than

would be the case at a BOF refinery, and dust produced by an EAF would be higher in

concentration for all radionuclides. Therefore, the baghouse at an EAF refinery is the case

analyzed and it bounds the exposure at BOF refineries. 

The inside of a baghouse represents a hazardous environment. The presence of airborne

baghouse dust in a confined and congested area requires that precautions be taken, such as use of

protective clothing and a respirator. This scenario assumes a respirator is used. Volatile and

entrained particulate radionuclides in the effluent would be trapped on the filters, presenting a

possible source of exposure to the individuals involved in baghouse operations. 

Exposure Pathways:

External: Exposure to penetrating radiation from the dust on the baghouse filters.

Inhalation: Exposure to resuspended dust in the baghouse.
Section 4 Recycle and Disposal of Steel

4-39 NUREG-1640

Secondary Ingestion: A baghouse worker would likely be dressed in anti-contamination

clothing. However, because of the prevalence of dust in the general refinery environment it is

still reasonable to include the secondary ingestion exposure pathway (inadvertent ingestion of

surface contamination). 

+DQGOLQJ($)'XVWDWWKH5HILQHU\

This work related scenario involves a refinery worker handling EAF dust at a refinery in

preparation for shipment. Most EAF refineries do not process their dust before shipping, so this

scenario assumes that there is no preparation of the dust for transport to a treatment and disposal

facility or fertilizer manufacturer. The bulk dust is loaded directly from its storage container into

a shipping container (e.g., an enclosed truck trailer) via a handling chute. The truck driver and

the worker who disconnects the chute and caps the transportation container would be the only

individuals in close proximity to the dust or the truck for a significant amount of time. This

scenario addresses the potential exposure of the refinery worker; the potential dose to the truck

driver is covered in another scenario. This scenario involves a worker that is located on top of

the container while the dust is being loaded via an overhead chute or conveyor belt. Exposure to

individuals other than the worker handling the chute are also possible. However, those people

would not be in close proximity to the truck for more than a very short time, and any amount of

dust that escaped the truck container would be small and would disperse before reaching any

nearby occupied areas. The scenario does not include public exposures, because the dust is

essentially contained at all times. 

Exposure Pathways: 

External: The worker would be exposed to penetrating radiation from the volume of dust inside

the container. 

Inhalation: This scenario assumes that while dust is being loaded into a truck container, a

fraction escapes and could be inhaled by the worker.

Secondary Ingestion: The EAF dust that is resuspended during the loading of dust into the

shipping container can be deposited as surface contamination, causing inadvertent ingestion of

EAF dust from contaminated hands and food. 

+DQGOLQJ5HILQHG0HWDO3URGXFWDWWKH5HILQHU\

This work related scenario covers a variety of specific jobs involving working close to refined

metal slabs, rods, sheets, and other forms at a refinery or mill. Even though just handling the

metal products will not generate airborne dust, other processing activities ongoing at the refinery

(melting, pouring molten steel, water-cooling steel, etc.) would cause metal dust to be

resuspended in the air. Similar to the refinery baghouse operations scenario, EAF refined metal

product is the case analyzed and bounds the exposure at BOF refineries.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-40

Exposure Pathways: 

External: The worker would be exposed to penetrating radiation from the metal forms. 

Inhalation: Inhalation of the resuspended metal dust from the various processing activities

mentioned is possible.

Secondary Ingestion: Suspended dust from other refinery operations could be deposited as

surface contamination, causing inadvertent ingestion from contaminated hands and food. 

+DQGOLQJ%2)5HILQHG0HWDO'XULQJ3URGXFW0DQXIDFWXUH

This work related scenario involves proximity to metal sheets in a metal-shop or factory and

activities such as bending, cutting, or shaping metal, which could result in resuspended metal

particles. Metal products from BOF refineries represent the analyzed scenario because EAF

metal products are typically items such as rebar and metal tractor cleats, and they do not undergo

further manufacturing.

Exposure Pathways: 

External: The worker would be exposed to penetrating radiation from the metal forms. 

Inhalation: Manufacturing activities would generate airborne metal particles.

Secondary Ingestion: Material deposited as surface contamination could be inadvertently

ingested from contaminated hands and food. 

+DQGOLQJ($)5HILQHG0HWDO3URGXFW'XULQJ'LVWULEXWLRQ

This work related scenario involves activities for distributing products made of EAF metal for

final use. Examples of potentially affected workers include delivery truck drivers, warehouse

workers, and shipping and receiving personnel. Metal items include such things as industrial

items, construction supplies, and general consumer products. Electric arc furnace metal product

is the case analyzed for this scenario for two reasons: 1) a larger percentage of the charge at an

EAF refinery would be scrap metal and 2) there is a shorter amount of time from production of

the metal to distribution for the EAF than the BOF (therefore less radioactive decay).

Exposure Pathways: 

External: Because distribution workers would not be in an environment where activities would

result in airborne metal dust, they would only be exposed to penetrating radiation from the

finished metal products. 
Section 4 Recycle and Disposal of Steel

4-41 NUREG-1640

3URFHVVLQJ6FHQDULRV

Refinery byproducts (dust and slag) must be processed before use or disposal, providing

opportunity for worker exposure to radioactivity. For this study, a variety of work related

conditions and practices were analyzed to identify the most likely exposure scenarios. This

included investigating the details of work related settings to develop accurate and representative

scenarios and to assign reasonable values (and ranges) to exposure parameters. During scenario

development, details were re-examined to ensure that appropriate scenarios were identified and

completely described. 

Processing activities involve potential exposure to all radionuclides present in refinery

byproducts by all three exposure pathways. Most processing activities involve worker proximity

to large masses of volumetrically contaminated refinery byproduct and moving it by a front-end

loader. The driver operating a front-end loader in close proximity to a large pile of material is

the individual evaluated. Other possible exposures (e.g., to other workers in the facility) would

be small. This scenario category includes two specific scenarios:

• Processing EAF dust for disposal

• Processing slag for use as aggregate or as roadbed

3URFHVVLQJ($)'XVWIRU'LVSRVDO

This work related scenario addresses a worker at a processing facility moving dust with a frontend loader or working near a pile of EAF dust.

Exposure Pathways: 

External: A worker in proximity to large masses of contaminated EAF dust would be exposed to

penetrating radiation from the volume source. 

Inhalation: While the EAF dust is being moved by the front-end loader, a fraction of it could be

suspended into the air, where it could be inhaled by the worker.

Secondary Ingestion: The material that is suspended can be deposited as surface contamination,

enabling secondary ingestion of radioactive material from contaminated hands and food. 

3URFHVVLQJ6ODJIRU8VHDV$JJUHJDWHRUDV5RDGEHG

This work related scenario addresses a worker at a processing facility moving slag with a frontend loader or working near a slagpile. The same type of activities that occur at a facility

processing EAF dust would occur here. Slag from an EAF refinery is the case analyzed, because

a larger percentage of an EAF charge is comprised of scrap metal, therefore, potentially resulting

in a higher concentration of radionuclides in slag.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-42

Exposure Pathways: 

External: Exposure to penetrating radiation from the material volume source (the slag pile).

Inhalation: A fraction of the slag could be suspended into the air, where it could be inhaled by

the worker. 

Secondary Ingestion: Suspended material could be deposited as surface contamination, allowing

inadvertent secondary ingestion of radioactive material from contaminated hands and food. 

6WRUDJH6FHQDULRV

Prior to use or disposal, slag is stored in large piles at the refinery and EAF dust in a storage silo. 

This category evaluates one work related exposure scenario (any work related exposures from a

slap pile would be bounded by the slag handling scenario).

6WRUDJHRI($)'XVWDW5HILQHU\

This scenario evaluates potential exposure to a worker at a refinery performing activities near an

EAF dust silo. This scenario assumes that a worker would be located near the silo where the

EAF dust is stored, for a certain amount of time each day. Exposure to EAF dust is being

analyzed instead of BOF dust because the concentration of radionuclides is higher in EAF dust,

due to less mixing with non-contaminated material in each furnace charge.

Exposure Pathways: 

External: Because EAF baghouse dust is typically contained within a silo, exposure to

penetrating radiation from the material volume source (the silo) is the only pathway explored.

3URGXFW8VH6FHQDULRV3:RUNHUV

The product-use category includes an extremely large number of possible worker exposure

situations. Because this category includes the use of products manufactured from recycled scrap

metal as well as refinery byproducts, it represents the most diverse category of potential exposure

scenarios—including both work related and public exposures. The size and diversity of potential

exposure situations makes it difficult to identify, organize, screen, and evaluate all possible

scenarios. 

This analysis does not evaluate the wide variety of possible worker product-use scenarios. These

exposure scenarios would be similar to the many potential non-worker product use scenarios, and

are, therefore, implicitly addressed in the non-worker scenarios described in Section 4.6.3.3. 

Refinery slag is considered a product of the refining process and is used in the single worker

product-use scenario: road construction activities using refinery slag.
Section 4 Recycle and Disposal of Steel

4-43 NUREG-1640

5RDG&RQVWUXFWLRQ$FWLYLWLHV8VLQJ5HILQHU\6ODJ

This work related product-use scenario involves the use of refinery slag as construction material

for a roadbed. It evaluates the potential exposures associated with activities necessary for

handling and laying the slag as road construction material. 

In this scenario, the slag is transported in a large dump truck to the construction site, where it is

dumped onto the roadbed and spread evenly on the road. The majority of work-related exposure

would occur as a result of being on the slag, to level it, after it is dumped on the roadbed. 

Therefore, the worker using the leveling equipment on the slag is the individual evaluated. The

exposure to the worker loading the dump truck from the slag pile is bounded by the handling slag

at the refinery scenario, and the exposure to the driver of the dump truck is bounded by the

transport of slag scenario.

Exposure Pathways: 

External: This scenario assumes that a worker is on the surface of the roadbed leveling the slag

and would be exposed to penetrating radiation from the slag volume source. 

Inhalation: While the slag is being dumped and leveled, a fraction of it could be suspended into

the air, making inhalation by the worker possible.

Secondary Ingestion: Redeposited surface contamination can be inadvertently ingested on

contaminated hands and food. 

7UDQVSRUWDWLRQ6FHQDULRV

One activity that occurs many times throughout the material flow for steel is transportation (see

Figure 4.1). Scrap metal cleared from NRC licensed facilities must be transported from the

nuclear facility to the refinery, and the refined metal product and refinery byproducts must be

transported from the refinery or mill to manufacturers, processors, users, or disposal sites. 

Although these can occur by either truck, rail, air, or barge, truck transportation is most common. 

Truck transportation also presents the highest potential dose to individuals because of long

exposure times and small distances from the source (truck) to the receptor (driver).

In general, those who handle packages directly are exposed to the highest dose rates, although

these exposures are usually for relatively short periods of time. Bystanders and persons traveling

or living along a travel route generally are subjected to lower dose rates. In most cases,

exposures of persons along the transport route are for a relatively short duration, but the number

of persons who can be exposed may become very large during a shipment of considerable

distance. A worker (the truck driver) is analyzed for all transportation scenarios.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-44

The transportation scenarios analyzed for this report include:

C Transport of scrap metal

C Transport of slag

C Transport of untreated EAF dust

C Transport of refined metal product.

Exposures of the general public during transportation are addressed in Section 4.6.3.4.

Exposure Pathways

External: The only exposure pathway included in the evaluation of all transportation scenarios is

the external exposure pathway for penetrating radiation from the truck load of material (e.g.,

scrap metal, slag, EAF dust).

7UDQVSRUWRI6FUDS0HWDO

This scenario describes the transportation of scrap metal from the nuclear facility. As described

in Section 4.2, the scrap metal can either be transported to a scrap dealer if it is suitable for

recycling, to the user if it is suitable for direct reuse rather than recycling, or directly to a disposal

facility if it is not suitable for either recycling or direct reuse. 

7UDQVSRUWRI6ODJ

This scenario describes the transportation of slag from the refinery to processors. The majority

of refinery slag is transported by truck within a 50 km (80 mi) radius of its source, the refinery.

7UDQVSRUWRI8QWUHDWHG($)'XVW

This scenario describes the transportation of EAF dust from the refinery to manufacturers or

processors (e.g., hazardous landfill or fertilizer manufacturer). As described in Section 4.2, EAF

baghouse dust is transported to either a hazardous landfill for immobilization and disposal or to a

fertilizer manufacturer for use as an additive.

7UDQVSRUWRI5HILQHG0HWDO3URGXFW

This scenario describes the transportation of refined metal product from the refinery or mill to the

manufacturers or distributors. Electric arc furnace refined metal products are sent directly to the

distributors with no additional manufacturing required, while BOF refined metal products are

sent to manufacturers prior to distribution (see Section 4.2). Because EAF refineries typically

use more scrap metal in a furnace charge than BOF refineries, and, therefore, have greater

potential radionuclide concentrations in refined metal products, the case analyzed for this

scenario is the transport of EAF refined metal products. 
Section 4 Recycle and Disposal of Steel

4-45 NUREG-1640

'LVSRVDO$FWLYLWLHV6FHQDULRV

When scrap metal or refinery byproducts have reached the end of their usefulness, they are

disposed of in either a RCRA Subtitle C (hazardous) or D (sanitary) landfill. Material placed in a

Subtitle C landfill is stabilized and, typically, placed in 55-gallon drums prior to disposal. 

Material placed in a Subtitle D sanitary landfill is not stabilized or placed in containers before

disposal. Disposal of this material involves workers placing waste in the final location within the

landfill unit, an activity that requires workers to spend time near the waste. 

This category of scenarios evaluates the activities associated with the disposal of materials. The

disposal activity scenarios include reasonable exposures to disposal facility workers. Some of

the total potential exposure is likely to occur after disposal of cleared material, not during actual

handling of the material (i.e., external exposure to disposed waste material). 

Four work related disposal activities scenarios were examined for this study. These scenarios

address those workers involved with the disposal of the material. 

C Disposal of BOF dust in a sanitary landfill

C Disposal of refinery slag in a sanitary landfill

C Disposal of scrap metal in a sanitary landfill

C Disposal of EAF dust in a hazardous waste landfill. 

No exposures of the general public would occur under any of the work related disposal scenarios

presented here. 

'LVSRVDORI%2)'XVWLQD6DQLWDU\/DQGILOO

This work related exposure scenario describes a worker disposing of BOF dust in a sanitary

landfill. Such activities can include a worker moving the BOF dust with a front-end loader from

a pile or truck to the landfill, or a worker on a piece of machinery, such as a bulldozer,

compacting the material in the landfill. The BOF dust is assumed to be in a form similar to soil,

with suspension of the material for inhalation and inadvertent ingestion by the worker. This

scenario assumes that BOF dust is disposed of in a sanitary landfill directly after production at

the refinery. Only the worker involved with the actual disposal activities is addressed.

Exposure Pathways: 

External: Exposure to penetrating radiation from the BOF dust on the ground.

Inhalation: Exposure to suspended BOF dust.

Secondary Ingestion: Inadvertent ingestion of surface contamination. 
Recycle and Disposal of Steel Section 4

NUREG-1640 4-46

'LVSRVDORI5HILQHU\6ODJLQD6DQLWDU\/DQGILOO

This work related exposure scenario describes a worker disposing of slag in a sanitary landfill. 

Such activities can include a worker moving the slag with a front-end loader from a pile or truck

to the landfill or a worker on a piece of machinery, such as a bulldozer, compacting the material

in the landfill. The slag is assumed to be in a form similar to soil, with suspension of the

material for inhalation and inadvertent ingestion by the worker. This scenario assumes that slag

is disposed of in a sanitary landfill directly after production at the refinery. Only the worker

involved with the actual disposal activities is addressed.

Exposure Pathways: 

External: Exposure to penetrating radiation from the slag in the ground.

Inhalation: Exposure to suspended slag.

Secondary Ingestion: Inadvertent ingestion of surface contamination. 

'LVSRVDORI6FUDS0HWDOLQD6DQLWDU\/DQGILOO

This work related exposure scenario describes a worker disposing of NRC licensed facility scrap

metal in a sanitary landfill. Only the worker involved with the actual disposal activities is

addressed. Disposal activities can include a worker at the landfill handling the metal manually or

using machinery. Activities can also include a worker on a piece of machinery, such as a

bulldozer, compacting the scrap metal.

Because no mechanical cutting or shredding of cleared scrap metal is assumed to occur prior to

disposal, it is reasonable to assume that there would be no appreciable suspension of

contamination, and therefore, no inhalation exposure to resuspended material. Likewise, there

would be no mechanism that would result in appreciable amounts of contamination for

inadvertent ingestion. Therefore, the only exposure pathway that is relevant is the external

exposure to penetrating radiation from the volume source. This scenario assumes that scrap

metal is disposed of in a sanitary landfill directly from the nuclear facility. 

Exposure Pathways: 

External: Exposure to penetrating radiation from the scrap metal in the ground.

'LVSRVDORI($)'XVWLQD+D]DUGRXV:DVWH/DQGILOO

This work related exposure scenario describes a worker disposing of EAF baghouse dust

immobilized in 55-gallon drums in a hazardous landfill. Handling includes moving the 55-gallon

drums with a fork lift, moving them from a vehicle to a storage facility, or placing them into the

landfill unit. (NOTE: Processing the dust, immobilizing it, and placing it in 55-gallon drums is
Section 4 Recycle and Disposal of Steel

4-47 NUREG-1640

covered in Section 4.6.2.2). Because the EAF dust is immobilized in the 55-gallon drums, it is

reasonable to assume that there is no suspension of contamination and, therefore, no exposure

due to inhalation of the resuspended material or inadvertent ingestion of surface contamination. 

Therefore, the only exposure pathway that is relevant is the external exposure to penetrating

radiation from the volume source. Only the worker involved with the actual disposal activities is

addressed. Exposures could also occur after initially handling the drums. These exposures are

also included.

Exposure Pathways:

External: Exposure to penetrating radiation from the 55-gallon drums containing immobilized

EAF dust.

'HVFULSWLRQRI1RQZRUNHU6FHQDULRV

The exposure scenario categories that include non-worker exposure are: 

C atmospheric releases

C storage

C product use

C transportation

C resident on closed landfill.

5HILQHU\$WPRVSKHULF5HOHDVHV

When scrap metal is processed at a refinery, atmospheric effluents released from the stack

potentially expose people living nearby to radioactivity contained in the release. A representative

scenario was evaluated for this category:

$WPRVSKHULF5HOHDVH'XULQJ5HILQLQJ

This public exposure scenario takes place near a refinery that is processing scrap metal from a

nuclear facility. During the refining process, atmospheric effluents are released from the stack. 

The scenario assumes the exposed person lives in the area surrounding the refinery year round

and has a home garden.

This scenario includes the exposure pathways listed below and illustrated in Figure 4.3.
4-48 NUREG-1640Source Atmosphere Transport

PathwayDoseTEDE

Resuspension

of Dust

Deposition

onto Plants

Deposition

onto Soil

Inhalation

Exposure

External

Exposure

Annual TEDE 

Ing

Exp

Uptake

into Plants

Figure 4.3 Modeling approach for the atmospheric releases from a refinery
Section 4 Recycle and Disposal of Steel

4-49 NUREG-1640

Exposure Pathways:

External: Exposure to penetrating radiation from volume sources while indoors and/or outdoors.

Inhalation: Exposure to the passing plume while indoors and outdoors, to suspended soil while

indoors and outdoors, and to suspended surface sources from soil tracked indoors.

Ingestion of Food and Soil: Ingestion of soil (secondary) from plant products grown in

contaminated soil and soil tracked indoors (inadvertent).

This set of exposure pathways, along with the selection of reasonable parameter values, provides

a comprehensive analysis for this scenario.

Other exposure pathways are possible, but were judged to have very small contributions in

comparison to the ones selected. For instance, ingestion of drinking water from a contaminated

surface water source in the vicinity of the refinery would be very small unless very large amounts

of radioactivity were released. Similarly, a potential dose from ingestion of drinking water from

a contaminated ground-water source would be insignificant unless the atmospheric deposition

source was very large and the subsequent transport to groundwater was rapid and unretarded.

The material that is released from a refinery stack is in two forms; particulates and off-gases. 

The off-gases are either completely volatilized or are in the form of particulates too small to be

captured in the air pollution control system at the refinery. Besides these off-gases, a small

fraction of the larger particulates that are produced are also released into the atmosphere. This is

because the baghouse filters that make up the air pollution control system are not 100% efficient. 

On average, these filters are about 99% efficient (see Sections 4.2 and 4.3).

Refinery emissions are the principal airborne effluents of concern during recycled steel

processing. Other effluents could be postulated, such as fugitive atmospheric releases from scrap

handling, however, these effluents are considered insignificant due to the small probability and

small magnitude of any release.

Listed below are assumptions for the specific exposure pathways.

External: People that live near the refinery would spend their time indoors, outdoors, and offsite. 

The time spent offsite is the fraction of the year that no external exposure occurs. Therefore, the

annual effective dose equivalent (EDE) for the external exposure pathway results from outdoor

activities and indoor activities onsite. The radionuclide concentration on the soil as a result of

deposition from the plume is used as the basis for calculating the external exposure.

Ingestion of Food and Soil: In general, an individual is assumed to live at a residence that has

soil contaminated via atmospheric deposition. Ingestion pathways that are included are ingestion

of plant products grown at the receptor location and secondary (inadvertent) ingestion of surface

soil at the receptor location. Since the ingestion dose is based on the air concentration at the
Recycle and Disposal of Steel Section 4

NUREG-1640 4-50

specified receptor location, the calculated intake of radioactivity is based on concentrations of

radionuclides in plant products grown at the same location. 

The following assumptions were made for the ingestion pathway:

C The concentration of radionuclides in edible parts of the plant at the end of the first

growing period is used as the harvest concentration. Multiple harvesting of plant crops is

not included.

C The concentration of C-14 and H-3 in the edible parts of the plant due to atmospheric

release was calculated separately using different equations.

C The resident consumes soil, leafy vegetables, and other vegetables grown on the

contaminated soil.

C The harvested crops, v, for human consumption (i.e., leafy vegetables and other

vegetables) are retained during a hold-up period before human consumption.

C The consumption period by an individual for plant food crops is 1 year. Radioactive

decay during the consumption period is accounted for in the intake calculation.

C Instantaneous equilibrium occurs between the radionuclide concentration in the soil and

in the concentration in the plants.

6WRUDJH6FHQDULRV

Prior to use or disposal, slag is accumulated and stored in large piles at the refinery and EAF dust

in a storage silo. This category evaluates one exposure scenario, storage of slag at refinery.

6WRUDJHRI6ODJDW5HILQHU\

This non-worker scenario takes place near a refinery that stores slag outside and does not include

any work related exposures associated with handling the slag. This scenario does not include

potential exposures associated with direct contact with the slag by the public (i.e., external,

exposure inhalation, or inadvertent ingestion). These exposure pathways are addressed in the

work related scenario which describes the worker near a slag pile (Section 4.6.2.1). Any public

exposure that would occur near the pile, such as external or inhalation, would be very small

because of the likely distance between the piles and any non-workers. Therefore, the only

pathway analyzed in this scenario is the ingestion of drinking water from a groundwater source. 

The analysis models the transport of radionuclides from the slag pile to the groundwater and

subsequent intake by a member of the public. The total effective dose equivalent (TEDE) due to

the ingestion of drinking water is calculated for a period of 1 year.
Section 4 Recycle and Disposal of Steel

4-51 NUREG-1640

Ground-Water 

Well

Domestic Use

Infiltration

Slag

Pile

Unsaturated 

Zone

Thickness =H

Thickness =H

1

2

Box 1

Box 2

Ground-Water 

Aquifer

Box 3

Figure 4.4 Three-box compartment model for the storage of slag scenario

Exposure Pathway:

Ingestion of drinking water: A member of the public would ingest contaminated drinking water

from a well near a refinery.

Once the slag is placed outside on the unprotected ground there is a potential to contaminate

groundwater in either the saturated or unsaturated zones. The primary mechanisms controlling

potential groundwater contamination include infiltration and leaching, transport through the

unsaturated zone, and transport through the saturated zone. Many additional characteristics of

the site influence these mechanisms, including precipitation rates, the land’s surface properties,

soil properties, the chemical nature of the radioactive contamination, spatial distributions of the

contamination, and advection/retardation in the aquifer.

For this scenario, the method used to estimate the concentration of radionuclides in a

groundwater aquifer is a simple leach-rate model accounting for total water use. Leach rates are

dependent on the chemical properties of the radionuclides and soil/slag and the rate of local water

movement. For the water-use model used, it was assumed that radionuclides would be

transferred to the groundwater because of contact with infiltrating water (i.e., as a function of the

solubility of the material in water with no retardation in soils). To account for potential saturated

and unsaturated conditions, a three-box compartmental model, similar to that used in

NUREG/CR-5512 (Kennedy and Strenge 1992), is used to estimate the transfer of radioactivity

from the surface to the groundwater aquifer over time. Figure 4.4 illustrates the three-box

compartmental model.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-52

The basic drinking water scenario from NUREG/CR-5512 is used for this scenario (Kennedy and

Strenge 1992). Assumptions for the drinking water model are listed below (box numbers refer to

Figure 4.4):

C Initial radioactivity is contained within box 1 (slag pile) and is assumed to be constant

throughout the year.

C Box 2 (unsaturated zone) and box 3 (aquifer) are initially free of contamination.

C The unsaturated zone refers to the distance between the bottom of the slag pile to the top

of the aquifer. For simplicity, the soil in this zone is treated as being homogeneous.

C Vertical, saturated, hydraulic conductivity is greater than the infiltration rate; water will

move vertically downward at least as fast as the infiltration rate.

C Infiltration volume is the product of the infiltration rate and the area of land

contaminated.

C No retardation in box 3 (aquifer).

C Activity in box 3 (aquifer) is diluted by the total volume of water in the aquifer 

C Radionuclide concentrations in all parts of box 3 (aquifer) are the same. Radionuclides

entering box 3 (aquifer) are immediately and uniformly mixed with the total volume of

water in the aquifer.

C Water is removed from the aquifer at a constant rate during the year to meet the needs of

irrigation and domestic water uses. The volume of water removed is immediately

replaced with an equal volume of uncontaminated water.

C The volume of water used for domestic purposes is sufficient for ten people.

C Radioactivity not removed during a year remains in the aquifer and contributes to the

initial radioactivity concentration for the next annual period.

C Water infiltration rate is a fraction of the total water application rate, which is equal to the

annual precipitation rate.

C Evaporative losses remove only water from the system (i.e., surface soil); radioactivity is

not lost by evaporation.

Steel slag is a very basic substance, and any water that leaches through a large pile of slag would

become “hard” through the leaching of oxides of calcium and magnesium. Therefore, it is likely

that in this scenario, an aquifer underlying a large slag pile would contain high concentrations of
Section 4 Recycle and Disposal of Steel

4-53 NUREG-1640

dissolved solids. In order to incorporate the probable high dissolved solids content of the aquifer

in this scenario, the total dissolved solids (TDS) in the aquifer were calculated over a period of

time, and when a TDS level of 10,000 mg/L was reached, the aquifer was no longer considered

drinkable. This TDS level is part of the EPA definition of an “underground source of drinking

water” (e.g., 40CFR146) and is considered a reasonable natural limit on potability of drinking

water, even without regulatory oversight.

3URGXFW8VH6FHQDULRV31RQZRUNHUV

The product-use category includes an extremely large number of possible exposure situations. 

Because this category includes the use of consumer products manufactured from recycled scrap

metal, as well as refinery byproducts, it represents the most diverse category of potential

exposure scenarios—including both work related and public exposures. The size and diversity of

potential exposure situations makes it difficult to identify, organize, screen, and evaluate all

possible scenarios. In line with the goals set for this study (the scenarios are required to be

comprehensive, appropriate, and practical) exposure scenarios were represented generically

instead of modeling a limited group of specific scenarios. The generic representations describe

groups of similar exposure situations (e.g., individuals close to a large mass of metal or a small

mass of metal close to tissue) rather than specific scenarios (e.g., person wearing a belt buckle or

using a frying pan). The sub-category of "individuals close to a large mass of metal," for

example, represents exposure situations such as individuals using office equipment (a desk) or

large consumer products (a refrigerator) made from recycled steel. 

The product-use exposure scenarios analyzed for this report include:

C In proximity of large metal mass

C In proximity of small steel mass

C Small steel mass close to body

C Inside an automobile

C Inside a steel-framed structure

C Use of slag as aggregate in basement construction

C Use of slag in a roadbed.

,Q3UR[LPLW\RI/DUJH0HWDO0DVV

Following clearance from a licensee, scrap metal would enter the scrap metal market, where it

could be melted and made into sheets or large, more massive pieces of steel stock. These in turn

can be manufactured into large metal items used by workers, consumers, or other members of the

general public. These items could be used in homes, offices, warehouses, and other industrial

settings. 

This scenario description is intended to be generic, in the sense that no specific situation is

described and is representative of any of the settings listed above. Among the numerous

examples of objects this scenario is intended to cover are large home appliances (such as
Recycle and Disposal of Steel Section 4

NUREG-1640 4-54

refrigerators and washing machines), office furnishings (such as large filing cabinets and metal

desks), and large industrial machines. An individual near such an object would be subject to

external radiation from radionuclides contained in the metal. The geometry of the object can be

represented generically by viewing it as an individual near a “large metal mass.” Other settings

where this geometry is applicable include less frequented areas, such as near highway bridge

supports, and certain work related settings, such as near scaffolding or other large items.

Items falling into the category of "large objects" could be the products of either a BOF refinery

(e.g., appliance, large filing cabinets) or EAF refineries (e.g., large structures like bridge supports

or scaffolding), based on the type of products from each refinery type (Section 4.2).

Activities conducted as part of this scenario could include short duration activities (e.g.,

occasional use of industrial items, such as scaffolding), medium duration (e.g., office work), and

long duration (e.g., residential). The case analyzed was of an individual in a residential setting

where a BOF product is used, because it is more likely that BOF products would result in the

residential exposures described in this scenario. 

Exposure Pathway: 

External: The only exposure pathway included in the scenario evaluation is the external

exposure pathway for penetrating radiation from the large object. 

,Q3UR[LPLW\RI6PDOO6WHHO0DVV

This scenario addresses activities that take place in the vicinity of a small object that is

constructed of metal made from recycled scrap metal. The scenario description is generic, in the

sense that no specific situation is described. Rather, this scenario covers use of numerous small

objects composed of metal from either a BOF refinery (e.g., small appliances such as a toaster) or

EAF refineries (e.g., hand tools). Items could be used in homes, offices, warehouses, and other

industrial settings. An individual near such an object would be subject to external radiation from

radionuclides contained in the metal. The geometry of the object can be generically represented

by categorizing it as an individual near a small steel mass.

Activities conducted as part of this scenario could include short duration activities (e.g.,

occasional use of industrial items such as small tools), medium duration (e.g., an office worker),

and long duration (e.g., residential). The case analyzed is of an individual in a residential setting

where a BOF product is used. 

Exposure Pathways:

External: The only exposure pathway included in the scenario evaluation is the external

exposure pathway for penetrating radiation from the small object. Other exposure pathways

theoretically possible—such as inhalation of contaminated material from degraded metal—are

not likely to be significant, compared to doses from external exposure. 
Section 4 Recycle and Disposal of Steel

4-55 NUREG-1640

6PDOO6WHHO0DVV&ORVHWR%RG\

This public-use scenario is similar to the scenario Proximity to Small Steel Mass, above, in that it

addresses activities that take place close to a small object that is constructed of metal made from

recycled scrap metal. The scenario description is generic and covers the use of numerous small

items, such as tools or belt buckles, made of metal from an EAF refinery. An individual very

near such an object would be subject to external radiation from radionuclides contained in the

metal. The geometry can be represented generically by a small metal object essentially on an

individual’s body.

Exposure Pathways: 

External: The only exposure pathway included in the scenario evaluation is the external

exposure pathway for penetrating radiation from the small object.

,QVLGHDQ$XWRPRELOH

Following clearance from a NRC licensed facility, cleared scrap metal would enter the scrap

metal market, where it could be melted and made into components for a vehicle. This is a likely

occurrence, because approximately 70% of a typical U.S. automobile is made from steel and iron,

and many of the steel components (e.g., undercarriage, engine block, axle, springs, and drive

shaft) are made from recycled steel (SRI 1995). An individual inside such a vehicle would be

subject to external radiation from radionuclides contained in the metal components. The

geometry can be represented generically by a plane (the undercarriage, drive shaft, axle, etc.) and

a block of metal (engine block). 

The exposed group in this scenario consists of people who drive or ride in an automobile a

significant part of each day (more than one hour). The scenario may be work related (i.e., a fleet

driver) or non-work related (e.g., a commuter). 

Exposure Pathways:

External: The only exposure pathway included in the scenario evaluation is the external

exposure pathway for penetrating radiation from the steel vehicle components. Other exposure

pathways theoretically possible—such as inhalation of contaminated material from degraded

metal—are not likely to be significant, compared to doses from external exposure, because the

residual radioactivity would be distributed throughout the volume of the recycled steel and hence

would not be easily mobilized. 

Although the metal could come from either an EAF or BOF, it is more likely that the types of

structural components involved in the scenario are products of EAF refineries. Therefore, this

scenario assumes EAF steel was used.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-56

,QVLGHD6WHHO)UDPHG6WUXFWXUH

Following clearance from a NRC licensed facility, cleared scrap metal would enter the scrap

metal market, where it could be melted and made into steel-framing components. This is an

increasingly likely occurrence, as the steel-framing industry uses recycled steel components, and

this U.S. residential industry is growing. The American Iron and Steel Institute estimates that the

number of full steel home starts in the U.S. has doubled from 40,000 in 1994 to 95,000 in 1997

and is projected to reach 325,000 by the year 2000 (AISI 1998).

An individual inside a steel-framed building would be subject to external radiation from

radionuclides contained in the metal structural components. The geometry can be represented

generically by an individual inside a cage.

The exposed group in this scenario consists of people who spend time inside a building

containing structural members made of recycled scrap steel. They could be in a work related

setting (e.g., an office building) or a residential setting (a home). Activities conducted as part of

this scenario could include short duration activities (occasional entry into a warehouse), medium

duration (office work), and long duration (residential). All of these were considered in

determining the exposure duration time for this scenario, however, the office and residential

settings were emphasized due to the longer times inside the building. 

Although the metal could come from either an EAF or BOF, it is likely that the types of

structural components involved in the scenario are products of EAF refineries. Therefore, this

scenario assumes EAF steel was used.

Exposure Pathway:

External: The only exposure pathway included in the scenario evaluation is the external

exposure pathway for penetrating radiation from the steel frame material (studs and joists). 

Other exposure pathways theoretically possible—such as inhalation of contaminated material

from degraded metal—are not likely to be significant, compared to doses from external exposure,

because the residual radioactivity would be distributed throughout the volume of the recycled

steel and, hence, would not be easily mobilized. 

8VHRI6ODJDV$JJUHJDWHLQ%DVHPHQW&RQVWUXFWLRQ

This public residential scenario evaluates exposure from slag used as aggregate in concrete. Slag

produced as a byproduct of refining can be used for construction of basements in homes,

although this is a limited practice. Because of its unsuitability, steel slag would not constitute

more than 3% of any concrete mixture. An individual living in a home with a basement built of

concrete with steel slag would be subject to external radiation from radionuclides contained in

the slag. 
Section 4 Recycle and Disposal of Steel

4-57 NUREG-1640

The individual evaluated in this scenario is a member of the public whose basement is

constructed with concrete containing refinery slag, and who spends the maximum defined period

inside the home.

Exposure Pathways:

External: The only exposure pathway included in the scenario evaluation is the external

exposure pathway for penetrating radiation from the slag. 

8VHRI6ODJLQD5RDGEHG

Refinery slag can be used as an aggregate in a roadbed. For this scenario, it is assumed that slag

is used as a base and asphalt or concrete is placed over it. Since the slag is either contained

within or under a solid mass, no resuspension of it can occur under normal conditions. It is

recognized that slag is sometimes used as the entire roadway and is not contained in a solid mass. 

The potential dose from this type of use is bounded by the evaluation of the work related scenario

addressed in Section 4.6.2, Road Construction Activities Using Refinery Slag.

Exposure would differ by type of use. The average driver may only be on the roadway a short

time each day, whereas a truck driver can spend a full work day on the road. However, the length

of time that a person is potentially exposed is balanced by proximity and shielding. The truck

driver is much higher off the ground and is more heavily shielded than is the average driver in a

car. This scenario analyzes the average person in a car.

Exposure Pathways: 

External: Because there is no possibility for the suspension of the slag in this scenario, only

external exposure to penetrating radiation from the volume source (the slag in the roadbed) is

analyzed.

7UDQVSRUWDWLRQ

One non-worker receptor was initially analyzed for all transportation scenarios, a maximally

exposed individual along the transportation route. This person is either caught in traffic next to

the truck or is driving next to the truck for a distance. The dose factors for this situation were

found to be insignificant and are, therefore, not included in the final tabulation of dose factors.

5HVLGHQWRQ&ORVHG/DQGILOO

This category of public exposure scenarios involves a resident on the site of a RCRA Subtitle C

or D landfill unit after the completion of the post-closure monitoring period. These scenarios are

of a different nature than the other scenarios analyzed, because they describe unlikely situations

potentially occurring many years in the future. Therefore, the dose factors calculated for the four

landfill-resident scenarios were not used in the critical group determination, but were analyzed
Recycle and Disposal of Steel Section 4

NUREG-1640 4-58

for completeness. The scenarios are described here and elsewhere in this section, and a summary

of the highest landfill-resident dose factors is included in Appendix J.

Section 4.6.2 discussed exposure of workers involved with disposing various types of material in

a either a RCRA Subtitle C or D landfill. This section introduces the scenarios describing

potential exposures to the general public after closure of such a landfill. The four scenarios

examined for this study are:

C Resident on closed landfill after disposal of BOF dust

C Resident on closed landfill after disposal of refinery slag

C Resident on closed landfill after disposal of scrap metal

C Resident on closed landfill after disposal of EAF dust

These scenarios are very similar to each other, with the disposed material representing the most

significant difference. No scenarios involving more than one potentially contaminated byproduct

of recycle have been evaluated, however, doses from more than one of the scenarios listed above

could be added if appropriate. 

This resident scenario category involves a person occupying a house with a basement and

maintains a vegetable garden on the site of a closed landfill that contains material derived from

cleared scrap steel. The exposure pathways modeled are listed and illustrated in Figure 4.5. The

modeling approach and assumptions that each of the scenarios within this category have in

common are presented below. 

Exposure Pathways

Specific exposure pathways included in the evaluation of resident scenarios are listed below. 

General and exposure-specific assumptions for the scenarios are discussed following this listing. 

External: The only exposure pathway consists of penetrating radiation from volume soil sources

while indoors and/or outdoors.

Inhalation: The inhalation pathway includes exposure to suspended soil while indoors and/or

outdoors and to suspended surface sources of soil tracked indoors.

Ingestion of Food and Soil: Ingestion exposure includes soil (secondary ingestion) and soil

tracked indoors (inadvertent ingestion), plant products grown in contaminated soil, soil

contaminated by irrigation (direct and inadvertent), and plant products irrigated with

contaminated ground water only.

Ingestion of drinking water: This pathway is limited to ingestion of drinking water from a

ground water source.
4-59 NUREG-1640

Soil Source

TransportPathwayDoseTEDE

Resuspension

of Dust

Uptake into

Plants

Inhalation

Exposure

External

Exposure

Annual TEDE

Irrigation

on Plant

Irrigation

on Soil

Uptake into

Plants

Drinking W

Exposur

Ingestion Exposure

(Irrigation & Non-irrigation)

Figure 4.5 Modeling approach for the resident on a closed landfill scenario
Recycle and Disposal of Steel Section 4

NUREG-1640 4-60

Because these residential scenarios are not based on worst-case occurrences, several exposure

pathways were not analyzed. For example, while air submersion may be an important pathway to

consider when evaluating the potential consequences of airborne releases from some facilities,

numerous studies of residual contamination in soil left after decommissioning a nuclear facility

have concluded that external doses from air submersion are trivial compared with external doses

from surface or volume sources (Schneider and Jenkins 1977; Smith et al. 1978; Oak et al. 1980). 

Since these residential scenarios are similar to residual contamination in soil, left after

decommissioning a nuclear facility, air submersion doses are considered insignificant and are not

evaluated.

Similarly, internal exposures from puncture wounds or from dermal absorption may be important

when evaluating sources of exposure to workers in licensed nuclear facilities. But most dose

assessments using these pathways are retrospective (after-the-fact) and rely on bioassay results to

help establish the magnitude of internal deposition that occurred for specific situations. The

frequency of occurrence of puncture wounds, although unpredictable, is assumed to be low. 

Dermal absorption may be important for only a few radionuclides, most notably H-3. To help

account for dermal absorption of H-3, the International Commission on Radiological Protection

(ICRP) increased the inhalation conversion by 50% (ICRP 1978). The dose that could result

from dermal absorption is assumed to be low compared with inhalation and ingestion doses. 

Thus, internal doses from puncture wounds and dermal absorption are not included in this

scenario.

Finally, some ingestion pathways often included in subsistence farmer scenarios have been

omitted. Maintenance of a dairy cow, a cattle herd, a wheat field, or a fish pond were considered

too unlikely to be appropriate for this exposed group. Therefore the milk, meat, grain, and fish

ingestion pathways were not included in this scenario. Ingestion rates for home grown

vegetables were chosen to represent a typical family garden rather than a subsistence farmer.

Six general assumptions for the residential scenarios are listed below. Assumptions specific to a

particular exposure pathway are discussed following this listing of general assumptions.

C Waste is placed in the landfill in the middle of its lifetime, 15 years before closure of a

hazardous landfill and 20 years before closure of a sanitary landfill.

C By a non-specific and unidentified means, the radionuclides in the waste are dispersed

evenly throughout the soil to a depth equal to that of the original landfill. The time that

leaching begins is different for each type of landfill. Waste disposed of in a sanitary

landfill begins leaching immediately after emplacement; waste disposed of in a hazardous

landfill begins leaching at the end of the post-closure monitoring period. Similarly, it is

assumed that the total activity in the waste is dispersed throughout the total volume of

material (soil and waste) in the landfill. This assumption simplifies the calculation by not

attempting to model the complex and uncertain waste-leaching process.
Section 4 Recycle and Disposal of Steel

4-61 NUREG-1640

C Contamination in the soil decays normally and continues to leach until the time activity is

determined.

C Irrigation (watering with contaminated groundwater) contaminates crops, which are

subsequently ingested by the resident. Recycling of radioactivity in irrigation water back

to the groundwater is not included in order to simplify the models. 

C A resident moves onto the landfill site after a post-closure monitoring period is

concluded. The scenario TEDE is for a 1-year period.

C The scenario “begins” at the time leaching starts, although no resident moves onto the

landfill until 50 to 150 years later.

Exposure Pathway-Specific Assumptions

External: The soil radioactivity concentration at the time a resident is assumed to move onto the

landfill site consists of the radioactivity remaining in the contaminated layer after leaching and

radioactive decay occurring during the post-closure monitoring period. 

Residents on the contaminated soil would spend their time indoors, outdoors, and offsite. The

time spent offsite is the fraction of the year that no external exposure occurs. Therefore, the

annual dose for the external exposure pathway results from outdoor activities and indoors

activities onsite. The radioactivity concentration in the soil, when the resident moves onto the

landfill, is used as the basis for calculating the external exposure. 

Inhalation: Similar to the external exposure pathway, the inhalation exposure pathway involves

a person that spends their time indoors, outdoors, and offsite. However, for this exposure

pathway, the outdoor exposure is separated into time spent on dusty activities (e.g., gardening)

and time spent on non-dusty activities (e.g., sitting). Because the original contamination occurs

as soil contamination, the inhalation dose only includes the suspension of contaminated soil from

the ground. The resuspension of soil indoors has two sources; material blown into the house

from outside and the suspension of soil that was tracked into the house. 

Ingestion of Food and Soil: The landfill resident is assumed to consume plants grown in a home

garden. This individual would also be exposed to secondary (inadvertent) ingestion of soil or

house dust. 

The ingestion exposure pathway is separated into two parts: non-irrigation and irrigation models. 

These two models can be used separately (e.g., growing plants in contaminated soil and irrigating

with uncontaminated water or growing plants in clean soil offsite but irrigating with

contaminated water), or they can be used together (e.g., growing plants in the contaminated soil

and irrigating with contaminated water). Effective dose equivalents are calculated for each

model separately, and the total ingestion (non-irrigation plus irrigation) dose assumes both occur

simultaneously. 
Recycle and Disposal of Steel Section 4

NUREG-1640 4-62

The following assumptions were made for the ingestion pathway dose modeling:

C The soil radionuclide concentration at the beginning of the crop-growing period is

considered to be the same as the soil radionuclide concentration at the time the resident

moves onto the landfill, Cs(t).

C The concentration of radionuclides in edible parts of the plant at the end of the first

growing period is used as the harvest concentration. Multiple harvesting of plant crops is

not included.

C A resident consumes soil, and vegetables, grown on the contaminated soil.

C Harvested vegetables for human consumption are held for a hold-up period before human

consumption.

C The consumption period by an individual for plant food crops is 1 year. Radioactive

decay during the consumption period is accounted for in the intake calculation.

C Instantaneous equilibrium occurs between the radionuclide concentration in the soil and

the concentration in the plants (for both human and animal consumption).

Irrigation vs Non-irrigation Ingestion Pathways

The irrigation ingestion pathway is similar to the non-irrigation pathway, except that the total

dose results from the use of contaminated irrigation water to grow plants in a home garden

instead of from surface soil contamination. In the non-irrigation ingestion model, the only

contamination available to be transferred to the plants is due to the initial soil radioactivity

concentration after the post closure monitoring period. In contrast, the irrigation model is used to

calculate the dose to a person who consumes plants and soil irrigated with contaminated water. 

The evaluation of resident doses can be made with both irrigation and non-irrigation models or

just one model. For example, if an individual lives on contaminated soil and irrigates with

contaminated water, use of both would be appropriate. Alternately, if the scenario involves an

individual who lives on non-contaminated soil and irrigates with contaminated water, the

irrigation model alone would be appropriate. For the evaluation of resident doses, the two

models are assumed simultaneously. 

To calculate the radionuclide concentration in foods grown with contaminated irrigation water

and consumed by a person living on the contaminated area, the following additional assumptions

have been made.

C The entire land surface area is irrigated and under cultivation.

C Radioactivity in the irrigation water is deposited in box 1 (surface layer).
Section 4 Recycle and Disposal of Steel

4-63 NUREG-1640

C Initial radionuclide concentration in the soil is zero and the concentration in plants and

soil is due only to the contamination from the irrigation water.

C Plants are contaminated from the irrigation water through deposition directly onto plants,

deposition onto the soil, and subsequent root uptake into the plant.

C The concentration of radionuclides in irrigation water is constant over the year of

irrigation (an average water concentration is used).

C Material deposited on plant surfaces is removed at a constant weathering half-life.

C Radionuclide concentrations in the soil from irrigation water are immediately in

equilibrium with radionuclide concentrations in edible portions of the plants grown in the

soil.

Ingestion of drinking water: Once the contamination from the waste is placed in the landfill, it

has the potential to contaminate groundwater in either the saturated or unsaturated zones. The

primary mechanisms controlling potential groundwater contamination include infiltration and

leaching, transport through the unsaturated zone, and transport through the saturated zone. Many

additional characteristics of the site influence these mechanisms, including precipitation rates,

the land’s surface properties, soil properties, the chemical nature of the radioactive

contamination, spatial distributions of the contamination, and advection\retardation in the

aquifer.

For the drinking-water pathway, the method used to estimate the concentration of radionuclides

in a groundwater aquifer is a simple leach-rate model accounting for total water use. Leach rates

are dependent on the chemical properties of the radionuclides and soil and the rate of local water

movement. For the water-use model used, it was assumed that radionuclides would be

transferred to the groundwater because of contact with infiltrating water (i.e., as a function of the

solubility of material in water with no retardation in soils). To account for potential saturated

and unsaturated conditions, a three-box compartmental model, similar to that used in

NUREG/CR-5512 (Kennedy and Strenge 1992) is used to estimate the transfer of activity from

the surface to the groundwater aquifer over time. Figure 4.6 illustrates the three-box

compartmental model.

The basic drinking-water scenario from NUREG/CR-5512 was used instead of the residential

drinking-water pathway. The basic drinking-water scenario does not include the recycling of

contamination from the aquifer back to the surface. The pumping-rate constant for the residential

scenario was used.

Assumptions for the drinking-water model are listed below (box numbers refer to Figure 4.6):

C Initial radioactivity is contained within box 1 (surface layer).
Recycle and Disposal of Steel Section 4

NUREG-1640 4-64

Ground-Water 

Well

Domestic Use

Infiltration

Surface 

Layer

Unsaturated 

Zone

Ground-Water 

Aquifer

Surface-Water 

Pond

Thickness =H

Thickness =H

1

2

Precipitation/Evaporation

Irrigation

Box 1

Box 2

Box 3

Figure 4.6 Three-box compartmental model for surface-to-groundwater transport for

resident on closed landfill scenario

C Box 2 (unsaturated zone) and box 3 (aquifer) are initially free of contamination.

C Vertically saturated hydraulic conductivity is greater than the infiltration rate. Water will

move vertically downward at least as fast as the infiltration rate.

C Infiltration volume is the product of the infiltration rate and the area of land

contaminated.

C No retardation in box 3 (aquifer).

C Activity in box 3 (aquifer) is diluted by the total volume of water in the aquifer (including

the volume of water in the surface water pond that is recharged from the aquifer).

C Radionuclide concentrations in all parts of box 3 (aquifer) are the same. Radionuclides

entering box 3 (aquifer) are immediately and uniformly mixed with the total volume of

water in the aquifer.
Section 4 Recycle and Disposal of Steel

4-65 NUREG-1640

C Water is removed from the aquifer at a constant rate during the year to meet the needs of

irrigation and domestic water uses. The volume of water removed is immediately

replaced with an equal volume of uncontaminated water.

C The volume of water used for domestic purposes is sufficient for ten people.

C Water is removed from the aquifer at a constant rate during the year of interest in the

analysis.

C Radioactivity not removed during a year remains in the aquifer and contributes to the

initial concentration for the next annual period.

C Water infiltration rate is a fraction of the total water application rate, which is the sum of

the irrigation application rate and the annual precipitation rate.

C Evaporative losses remove only water from the system (i.e., surface soil and surfacewater pond). Radioactivity is not lost by evaporation.

The initial activity present in box 1 is defined as the total activity present in box 1 when leaching

begins. Once leaching begins, the contamination is dispersed evenly throughout the soil to a

depth equal to the original depth of the landfill. The total capacity of the landfill unit does not

consist completely of cleared waste. Daily cover material is interspersed between the waste, as

well as being placed over the entire landfill upon closure. 

Landfill Resident Scenario Descriptions

The specific landfill resident scenarios are described below.

5HVLGHQWRQD&ORVHG/DQGILOO$IWHU'LVSRVDORI%2)'XVW

This public exposure scenario describes exposure to a resident on the site of a closed sanitary

landfill after the disposal of BOF dust from the refinery. This residence begins after the postclosure monitoring period is completed and does not include any work related exposures

associated with operating the landfill. This scenario assumes that the BOF dust is immediately

disposed of in a sanitary landfill in the middle of its lifetime, 20 years before closure. The waste

is assumed to begin leaching immediately upon placement in the landfill. Because the BOF dust

is able to physically mix throughout the soil, the radioactivity is assumed to be dispersed

throughout the mass of waste, daily cover-soil (soil used to cover the waste on a daily basis) and

final cover-soil. This scenario addresses the same exposure pathways that are addressed in the

generic scenario: drinking water, external exposure, inhalation exposure, and ingestion

exposure. 
Recycle and Disposal of Steel Section 4

NUREG-1640 4-66

5HVLGHQWRQD&ORVHG/DQGILOO$IWHU'LVSRVDORI5HILQHU\6ODJ

This public exposure scenario describes a resident on the site of a closed sanitary landfill after

the disposal of refinery slag. This scenario assumes that slag is disposed of in a sanitary landfill

directly from the refinery and allowed to immediately leach towards the groundwater. A resident

then moves onto the closed landfill after the completion of the post-closure monitoring period. 

Because the slag is able to physically mix throughout the soil, the activity is assumed to be

dispersed throughout the mass of waste, daily cover-soil, and final cover-soil. 

5HVLGHQWRQD&ORVHG/DQGILOO$IWHU'LVSRVDORI6FUDS0HWDO

This public exposure scenario describes a resident on the site of a closed sanitary landfill after

the disposal of scrap metal from a nuclear facility (direct disposal of cleared scrap). In order to

calculate the radionuclide concentration in the surface layer after leaching occurs, the total mass

of material in which the radioactivity is dispersed must be determined. Because the scrap metal

cannot physically mix throughout the soil, the activity is assumed to be dispersed throughout the

daily cover soil and final cover soil only. 

Radionuclides are modeled to begin leaching from the scrap immediately upon placement in the

landfill. The radionuclides in the scrap metal leach to the unsaturated zone beneath the scrap as

well as the cover soil surrounding the scrap metal. The radioactivity that is leached to the cover

soil surrounding the scrap metal is then accumulated and not allowed to leach toward the

groundwater. This is reasonable within the context of this scenario because the same leach-rate

constant is used for the movement of radionuclides from the scrap metal to the unsaturated zone

and the cover-soil. Therefore, twice the normal amount is allowed to leach from the scrap metal. 

A resident moves onto the closed landfill after completion of the post closure monitoring period,

50–100 years after the scrap metal is placed in the landfill.

5HVLGHQWRQD&ORVHG/DQGILOO$IWHU'LVSRVDORI($)'XVW

This public exposure scenario describes a resident on the site of a closed hazardous landfill after

the disposal of EAF dust directly from the refinery. This scenario assumes that EAF dust is

disposed of in a hazardous landfill directly from the refinery. Because EAF dust is placed in 55-

gallon drums for disposal, leaching does not begin immediately upon disposal. At the end of the

post-closure monitoring period, the integrity of the drum is assumed to be lost and the EAF dust

is dispersed throughout the soil. The total mass of material in which the radioactivity is mixed

includes the waste, daily cover-soil, and final cover-soil. At this point, modeling the

radionuclides leaching toward the groundwater begins. A resident is assumed to move onto the

landfill after the completion of the post-closure monitoring period, 95–145 years after the EAF

dust is placed in the landfill.
Section 4 Recycle and Disposal of Steel

4-67 NUREG-1640

4 '  $J % $UD  ( H

&UW

V

5'

4.15

$UD ' 0UD ( &G 4.16

(QYLURQPHQWDO0HGLD&RQFHQWUDWLRQV5HVXOWLQJIURP(QYLURQPHQWDO7UDQV

$WPRVSKHULF5HOHDVHV6RXUFH7HUP'LVSHUVLRQ0HGLD

&RQFHQWUDWLRQ

Before the TEDE from atmospheric releases can be calculated, the source term and atmospheric

dispersion term, must be calculated. 

As stated previously, the emissions from a refinery consist of two parts, the off-gases and the

particulates that escape the air pollution control system. The volumetric release rate of air from

the refinery stack over the time period of interest is not a critical value, as long as it is relatively

constant, and it is assumed that all activity is released. The average radioactivity release rate

from the refinery stack is the important parameter. This is represented in Equation 4.15. 

where

Q = radionuclide release rate from refinery stack (pCi/s)

and

Ag = activity in the off-gases leaving the refinery stack in a year (pCi)

Ara = dust activity in refinery atmospheric effluent that passes through the baghouse filter

(pCi)

RD = duration of release of refinery atmospheric effluent (s)

r = radioactive decay constant (1/d)

ts = time from clearance of material from nuclear facility to time scenario begins (d)

The dust radioactivity in the refinery atmospheric effluent that passes through the baghouse filter

(Ara) can be calculated from the mass of dust that passes through the filter and the radioactivity

concentration in dust as follows. This is shown in Equation 4.16. 

where

Ara = dust radioactivity in refinery atmospheric effluent that escapes the refinery baghouse

in a year (pCi)

and

Mra = total mass of dust that escapes the refinery baghouse in a year (g)

Cd = radionuclide concentration in dust after the refining process (pCi/g)

$WPRVSKHULF'LVSHUVLRQ7HUP

The effluent dispersion of radioactive materials released into the atmosphere from a refinery

facility is a function of several physical and environmental variables. For routine airborne
Recycle and Disposal of Steel Section 4

NUREG-1640 4-68



4 '  jM )6&M

( >[ XM]M@

& ( H[S & 



+H

]M



4.17

] M' 6& ( [ Q 4.18

releases, the concentration of radioactive material at a given downwind locus depends upon the

effluent emission rate, the effective height of the release, the average windspeed, atmospheric

stability, airflow patterns at the site, and various effluent removal mechanisms. 

Of the different approaches to modeling atmospheric dispersion, the straight-line Gaussian plume

model (Slade 1968) is the most widely used method. In this model, the windspeed and

atmospheric stability at the release point are assumed to determine the atmospheric dispersion

characteristics in the mean wind direction at all distances. For effluent releases that are

continuous or intermittent over long periods of time and, thus, subject to variations in wind

direction, horizontal dispersion can be treated as an average over the width of a user-defined

sector. The sector-averaged form of the Gaussian model (NRC 1977) used for this scenario is

based on a sector width of 22.5°. The frequency of occurrence for windspeed and stability class

are based on national-average data. This model treats the exposed group as residing in the

downwind direction throughout the year. Atmospheric dispersion is given by Equation 4.17. 

where

/Q = annual average atmospheric dispersion factor (s/m3)

and

FSCj = fraction of time that stability class j occurs (dimensionless)

x = distance from release point to receptor (m)

uj = average windspeed for stability class j (m/s)

zj = vertical dispersion coefficient for stability class j at distance x (m)

He = effective stack height (m)

The vertical dispersion coefficient, z, is defined for each Pasquill atmospheric stability class AG and is a function of downwind distance, x. The Jülich System, for an emission height of 50 m

(164 ft) is used to define z. According to Till and Meyer (1983), this system is applicable to

sites with medium to high surface roughness, due to settlements, vegetation, and other ground

obstacles. Equation 4.18 is used to calculate these coefficients for stability classes, SC, A-F and

Equation 4.19 is used for stability class G.

where

zj = vertical dispersion coefficient for stability class j at distance x (m)

SC = stability class

x = distance from release to receptor (m) 
Section 4 Recycle and Disposal of Steel

4-69 NUREG-1640

]*'  ]) 4.19 

 ' 

4 ( 4 4.20

&JUQG '  ( 9G 7 ( & H

& U W

E

U

4.21

SC = 0.2222 (j = A,B)

0.2149 (j = C)

0.2048 (j = D)

0.1616 (j = E)

0.3960 (j = F)

n = 0.9680 (j = A, B)

0.9438 (j = C)

0.9358 (j = D)

0.8094 (j = E)

0.6183 (j = F)

Equation 4.20 represents the air concentration of radionuclides at a distance x from the refinery. 

where

= the average effluent concentration, averaged over a sector 22.5E wide (pCi/m3)

and

/Q = annual average atmospheric dispersion factor (s/m3)

Q = radionuclide release rate from refinery stack (pCi/s)

*URXQG6XUIDFH&RQFHQWUDWLRQ5HVXOWLQJIURP$WPRVSKHULF

5HOHDVHV

Doses were calculated for external irradiation from nuclides deposited on the ground surface. 

The ground-surface dose originates from a thin layer of radionuclides deposited on the ground

surface from the passing plume. This concentration also includes the amount of radioactivity that

is weathered off plants. Therefore, the total deposition velocity, Vd(t), is used in Equation 4.21 to

calculate the ground-surface radioactivity concentration.

where

Cgrnd = ground-surface radioactivity concentration (pCi/m2

)

and

= the average effluent concentration, averaged over a sector 22.5E wide (pCi/m3)

Vd(T) = total deposition velocity (m/d)

tb = the period of long-term buildup for activity in soil (d)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-70

Cs(0) ' Cgrnd

H1 ( s

4.22

&Y ' (9G7 U&H

&HW

JY

<Y H

% %LY :Y &H

&UW

E



U 3

4.23

r = radioactive decay constant (1/d)

The volumetric radionuclide concentration in the soil is represented by Equation 4.22.

where

Cs(O) = soil radionuclide concentration at time of scenario (pCi/g dry-weight soil)

and

Cgrnd = ground surface radionuclide concentration (pCi/m2

)

H1 = thickness of surface soil layer (m)

s = average density of soil in surface layer (g dry-weight soil/m3

)

&RQFHQWUDWLRQLQ(GLEOH3DUWVRI3ODQWV

The radionuclide concentration in the edible parts of plants at the time of harvest is described in

Equation 4.23. This equation is used to calculate the concentration in leafy vegetables and

vegetables (for human consumption) due to direct deposition and root uptake. The concentration

of C-14 and H-3 in plants is calculated using Equations 4.24 and 4.25, respectively. 

where

Cv = radionuclide concentration in edible part of plant v for consumption (i.e., leafy

vegetables and vegetables) due to root uptake and directly deposited material (pCi/kg

wet-weight plant)

and

= average effluent radionuclide concentration, averaged over a sector 22.5E wide

(pCi/m3

)

Vd(T) = total deposition velocity (m/d)

r = the fraction of total material being deposited that is intercepted by crops

(dimensionless)

e = effective weathering and decay constant at harvest (1/d) ( r

 + w)

tgv = the time period that crops are exposed to contamination during the growing season

(d)

Yv = yield of plant v (kg wet-weight plant/m2

)

Biv = root uptake factor for radionuclide i from soil to plant v (pCi/kg dry-weight plant per

pCi/kg dry-weight soil)

Wv = dry-weight-to-wet-weight conversion factor for plant v (kg dry-weight plant/kg wetweight plant)

r = radioactive decay constant (1/d)

tb = the period of long-term buildup for radioactivity in soil (d)

P = areal soil density (kg dry-weight soil/m2

)
Section 4 Recycle and Disposal of Steel

4-71 NUREG-1640

&Y&& ' (%  ( SF& (( 

 4.24

&Y+& ' (%  (   (( 

+ 4.25

Cv,h ' Cv e &8r

th 4.26

The concentration of C-14 in plants due to deposition is calculated using Equation 4.24.

where

Cv,C-14 = concentration of C-14 in edible part of plant v for consumption (i.e., all plants)

(pCi/kg wet-weight plant)

and

= average effluent radionuclide concentration, averaged over a sector 22.5E wide

(pCi/m3

)

pc-14 = fractional equilibrium ratio (dimensionless)

0.11 = fraction of total plant mass that is natural carbon (dimensionless)

0.16 = radionuclide concentration of natural carbon in the atmosphere (g/m3

)

1.0E+3 = unit conversion factor (g/kg)

The concentration of H-3 in plants due to deposition is represented by Equation 4.25.

where

Cv,H-3 = concentration of H-3 in edible part of plant v for consumption (i.e., all plants)

(pCi/kg wet-weight plant)

and

= average effluent radionuclide concentration, averaged over a sector 22.5E wide

(pCi/m3

)

H = absolute humidity of the atmosphere at receptor (g/m3

)

0.5 = ratio of tritium concentration in plant water to tritium concentration in

atmospheric water (dimensionless)

1.0E+3 = unit conversion factor (g/kg)

0.75 = fraction of total plant mass that is water (dimensionless)

Plants for direct human consumption are considered to have a hold-up period before being

consumed. The radionuclide concentration in plants at the end of the hold-up period is calculated

using Equation 4.26 for all radionuclides including C-14 and H-3.

where

Cv,h = radionuclide concentration in edible part of plant v for human consumption at the

end of the hold-up period (pCi/kg wet-weight plant)

and

Cv = radionuclide concentration in edible part of plant v for consumption due to root

uptake and directly deposited material (pCi/kg wet-weight plant)

r = radioactive decay constant (1/d)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-72

0Z ' 9Z ( Z ( ): 4.27

$ ' &ZDVWH ( 0Z 4.28

$ ' & ( 0 4.29

th = hold-up period between harvesting and consumption (d)

'ULQNLQJ:DWHU&RQFHQWUDWLRQV

The drinking water pathway is included in residential scenarios and the slag storage scenario. 

Calculation of doses resulting from ingestion of drinking water requires calculating radioactivity

concentrations in the aquifer, i.e., the assumed source of drinking water. This section contains

the equations comprising the drinking-water model, starting with the surface layer. The total

mass of waste in the surface layer, for landfill resident scenarios is calculated using

Equation 4.27.

where

Mw = total mass of waste that is from cleared material in box 1 (surface layer) (g waste)

and

Vw = volume of all waste in landfill (m3

)

w = density of waste that is from cleared material (g waste/m3

)

FW = fraction of total waste that is from cleared material

The total initial radioactivity is calculated by multiplying the radioactivity concentration in the

waste for residential landfill scenarios, when leaching to the groundwater begins, by the total

mass of waste in the contaminated surface layer as shown in Equation 4.28.

where

A1(0) = initial activity in box 1 (surface layer) (pCi)

and

Cwaste = radionuclide concentration in waste when leaching to groundwater begins (pCi/g

waste)

Mw = total mass of waste that is from cleared material in box 1 (surface layer) (g waste)

For the slag storage scenario, the total activity in the slag pile is represented by Equation 4.29.

where

A1(0) = initial radioactivity in box 1 (slag pile) (pCi)

and

C0 = radionuclide concentration in the source material at the time the scenario begins

(pCi/g)
Section 4 Recycle and Disposal of Steel

4-73 NUREG-1640

$W ' $ H

&U % / W

4.30

$VW ' $H

& UW

& $H

&U% /ZVW

4.31

$W '

/$ H

&U % / W

U % / & U % / % $ &

/$

U % / & U % /

H

&U % /W

4.32

M = total mass of material in box 1 (slag pile) (g)

Once the initial radioactivity in the surface layer is calculated, the activities in each of the other

two boxes (layers) in the model can be calculated. These activities are calculated as a function of

time because radionuclides move through the boxes according to leach rate constants, which

have units of d-1. Leaching is assumed to begin immediately after placement of slag or waste,

prior to the beginning of the exposure scenario. The activity in box 1 (surface layer) as a

function of time is expressed using Equation 4.30.

Box 1 in the groundwater model for scrap disposal scenarios consists of the scrap metal instead

of the surface layer. Box 2 and box 3 still refer to the unsaturated zone and the aquifer,

respectively. Therefore, A1(0), calculated by Equation 4.29, is defined as the initial activity in the

scrap metal at the time leaching to the groundwater begins. Equation 4.31 is used for scrap

disposal scenarios to calculate activity in the surrounding soil at time t.

where

As(t) = activity in the surrounding cover soil at time t (pCi)

and

A1(0) = initial activity in box 1 (scrap metal) (pCi)

r = radioactive decay constant (1/d)

t = time from beginning of leaching to time activity is determined (d)

Lws = rate constant for movement of radionuclide from box 1 (scrap metal) to box 2

(unsaturated zone and cover soil) (1/d)

Equation 4.32 is used to calculate the activity in the unsaturated zone at time t. In scrap disposal

scenarios, the rate constant Lws is substituted for L12. Lws is also substituted for L12 in

Equation 4.33.

The activity of the radionuclide in box 3 (aquifer) as a function of time is calculated using

Equation 4.33.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-74

$W '

/ / $H

&U % /W

> U % / & U % /@ >U % ZU & U % / @

/ $

U % ZU & U % / &

/ / $

>U % / & U % /@>U % ZU & U % / @

H

& U % /

% $&

/ $

U%ZU&U%/

%

// $

>U%ZU&U%/@>U%ZU&U%/ @

H

&U%ZUW

4.33

/ ' ,

+  5 W   4.34

 ' Q I

 4.35

where

A1(t) = activity in box 1 (surface layer) at time t (pCi)

A2(t) = activity in box 2 (unsaturated zone) at time t (pCi)

A3(t) = activity in box 3 (aquifer) at time t (pCi)

and

A1(0) = initial activity in box 1 (surface layer) (pCi)

A2(0) = initial activity in box 2 (unsaturated zone) (pCi)

A3(0) = initial activity in box 3 (aquifer) (pCi)

r = radioactive decay constant (1/d)

L12 = rate constant for movement of radionuclide from box 1 (surface layer) to box 2

(unsaturated zone) (1/d)

L23 = rate constant for movement of radionuclide from box 2 (unsaturated zone) to box 3

(aquifer) (1/d)

t = time from beginning of leaching to time activity is determined (d)

wr = residential pumping rate constant from box 3 (aquifer) to box 2 (surface layer) (1/d)

As described for previous equations, Box 1 can represent a slag pile, the surface layer, or scrap

metal. The rate constants for movement of radionuclides from box 1 to box 2 are calculated

using Equations 4.35, 4.34, and 4.36. The rate constant for the movement of radionuclides from

the scrap metal to the surrounding soil and to the unsaturated zone, Lws, was not calculated by

Equation 4.34. Instead this value was input as a radionuclide-independent parameter. Two

different pumping rate constants are used in Equation 4.33 depending on the scenario being

analyzed. The residential pumping rate constant, wr

, is used for the resident on closed landfill

scenarios while wd is used for the storage of slag scenario.
Section 4 Recycle and Disposal of Steel

4-75 NUREG-1640

5 W '  %

. G 

Q

4.36

 ' Q I

 4.37

5 W '  %

. G 

Q

4.38

/ ' ,

+  5 W   4.39

where

L12 = rate constant for movement of radionuclide from box 1 (surface layer) to box 2

(unsaturated zone) (1/d)

and

I = infiltration rate (m/y)

H1 = thickness of box 1 (surface layer) (m)

1 = volumetric water content of box 1 (surface layer) (dimensionless)

Rt1 = retardation factor for movement of radionuclide from box 1 (surface layer) to box 2

(unsaturated zone) (dimensionless)

365.25 = unit conversion factor (d/y)

n1 = total porosity of box 1 (surface layer) (dimensionless)

f1 = saturation ratio for box 1 (surface layer) (dimensionless)

Kd1 = soil/water partition coefficient for radionuclide in box 1 (surface layer) (mL/g)

1 = bulk density of soil in box 1 (surface layer) (g/mL)

Equations used to calculate movement of radionuclides from box 2 to box 3 are shown below as

Equations 4.37, 4.38, and 4.39.

where

L23 = rate constant for movement of radionuclide from box 2 (unsaturated zone) to box 3

(aquifer) (1/d)

and

I = infiltration rate (m/y)

H2 = thickness of box 2 (unsaturated zone) (m)

2 = volumetric water content of box 2 (unsaturated zone) (dimensionless)

Rt2 = retardation factor for movement of radionuclide from box 2 (unsaturated zone) to

box 3 (aquifer) (dimensionless)

365.25 = unit conversion factor (d/y)

n2 = total porosity of box 2 (unsaturated zone) (dimensionless)

f2 = saturation ratio for box 2 (unsaturated zone) (dimensionless)

Kd2 = soil/water partition coefficient for radionuclide in box 2 (unsaturated zone) (mL/g)

2 = bulk density of soil in box 2 (unsaturated zone) (g/mL)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-76

Pumping rate constants are calculated in order to estimate the amount of water pumped from the

aquifer, using Equations 4.40 and 4.41.
Section 4 Recycle and Disposal of Steel

4-77 NUREG-1640

ZG '

9GG  97G

7S

4.40

ZU '

9LUU % 9GU

97U

7

S

4.41

&Z '

$W

97U

4.42

where

wd = pumping rate constant from box 3 (aquifer) to surface (1/d)

and

Vdd = volume of water used for domestic purposes during a year (L)

VTd = total water volume in box 3 (aquifer) (L)

Tp = time period for pumping (d)

where

wr = residential pumping rate constant from box 3 (aquifer) to box 1 (surface layer) (1/d)

and

Vdr = volume of water used for domestic purposes during a year (L)

Virr = volume of water used for irrigation purposes during a year (L)

VTr = total water volume in box 3 (aquifer) (L)

Tp = time period for pumping (d)

The concentration of radioactivity in the groundwater is calculated by dividing the total activity

in the aquifer at the time the scenario begins by the total volume of water in the aquifer, as shown

in Equation 4.42.

where

Cw = radionuclide concentration in groundwater (pCi/L)

and

A3(t) = activity in box 3 (aquifer) at time t (pCi)

VTr = total water volume in box 3 (aquifer) (L)

The value for the total volume of water in the aquifer is the greater of (1) the sum of the annual

infiltration and annual irrigation volume or (2) the sum of the annual volume of water used for

irrigation, the annual domestic water use, and the aquifer-fed surface-water pond volume. For

some scenarios (e.g., storage of slag at the refinery), the total volume of water in the aquifer is
Recycle and Disposal of Steel Section 4

NUREG-1640 4-78

9,U ' , ( $F ( (7L 4.43

9,U ' , ( $G ( (7L 4.44

&VW '

$W

47

4.45

simply the greater of (1) the sum of the annual infiltration and the annual irrigation volume, or

(2) the annual domestic water use.

The annual infiltration and irrigation volume is calculated using Equation 4.43.

where

VIr = annual infiltration and irrigation volume through the cultivated farmland area (L)

And I = infiltration rate (m/y)

Ac = area of land under cultivation (m2 )

1000 = unit conversion factor (L/m3 )

Ti = time period for infiltration and irrigation (y)

For the slag storage scenario, the annual infiltration and irrigation volume is calculated using

Equation 4.44, where the area of contaminated land has been substituted for the area of land

under cultivation.

where

VIr = annual infiltration and irrigation volume through the cultivated farmland area (L)

and

I = infiltration rate (m/y)

Ad = area of contaminated land (m2 )

1000 = unit conversion factor (L/m3 )

Ti = time period for infiltration and irrigation (y)

The soil radionuclide concentration at the beginning of landfill resident scenarios, after leaching

has taken place, is calculated using Equation 4.45. The total mass of material in the landfill, QT,

refers to the waste, daily cover-soil, and final cover-soil. 

where

Cs(t) = soil radionuclide concentration at time resident moves onto landfill (pCi/g dryweight soil)

and

A1(t) = activity in box 1 (surface layer) at time t (pCi)

QT = total mass of material in box 1 (surface layer) (g dry-weight soil)
Section 4 Recycle and Disposal of Steel

4-79 NUREG-1640

For one scenario (resident on closed landfill after disposal of scrap metal) Equation 4.46 was

used in place of Equation 4.45 to calculate soil radionuclide concentration where the total mass

of material in the landfill is comprised of the daily cover-soil and final cover-soil.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-80

&VW ' $VW

47

4.46

&YQ '  ( 0/Y % %LY  ( :Y ( &VWH

&U W

JY 4.47

where

Cs(t) = soil radionuclide concentration at time resident moves onto landfill (pCi/g dryweight soil)

and

As(t) = activity in the surrounding cover soil at time t (pCi)

QT = total mass of material in box 1 (surface layer) (g dry-weight soil)

)RRGDQG6RLO&RQFHQWUDWLRQV

The ingestion exposure pathway is analyzed in two parts using non-irrigation and irrigation

models. These two models can be used separately (i.e., growing plants in contaminated soil and

irrigating with uncontaminated water or growing plants in clean soil offsite, but irrigating with

contaminated water) or they can be used together (i.e., growing plants in contaminated soil and

irrigating with contaminated water). Effective dose equivalents are calculated for each model

separately; the total ingestion dose (non-irrigation plus irrigation) dose assumes both occur

simultaneously. 

1RQ,UULJDWLRQ,QJHVWLRQ0RGHOIRU5HVLGHQWRQ&ORVHG/DQGILOO

&RQFHQWUDWLRQLQHGLEOHSDUWVRISODQW. The radionuclide

concentration in the edible part of the plant of interest at the time of harvest is described in

Equation 4.47. This Equation is used to calculate the radionuclide concentration in vegetables

for human consumption.

where

Cv,n = radionuclide concentration in edible part of plant v for consumption due to root

uptake and resuspended soil (non-irrigation model) (pCi/kg wet-weight plant)

and

Biv = root uptake factor for radionuclide I from soil to plant v (pCi/kg dry-weight plant per

pCi/kg dry-weight soil)

MLv = plant soil mass-loading factor for resuspended soil to plant v (pCi/kg dry-weight

plant per pCi/kg dry-weight soil)

Wv = dry-weight-to-wet-weight conversion factor for plant v (kg dry-weight plant/kg

wet-weight plant)

Cs(t) = soil radionuclide concentration at time resident moves onto landfill (pCi/g

dry-weight soil)

r = radioactive decay constant (1/d )

tgv = growing period for plant v (d)

1000 = unit conversion factor (g/kg)
Section 4 Recycle and Disposal of Steel

4-81 NUREG-1640

&YQK ' &YQH

&UW

K 4.48

5YS '

,5 ( U

Y ( 7Y ( &Z

<Y

4.49

The soil radionuclide concentration at the time the resident moves onto the landfill, Cs(t), is

calculated using Equation 4.45; Equation 4.46 is used for disposal of metal. Plants for direct

human consumption are considered to have a hold-up period before being consumed. The

radionuclide concentration in plant v at the end of the hold-up period is calculated using

Equation 4.48.

where

Cv,nh = radionuclide concentration in edible part of plant v for human consumption at end of

hold-up period (non-irrigation model) (pCi/kg wet-weight plant)

and

Cv,n = radionuclide concentration in edible part of plant v for consumption due to root

uptake and resuspended soil (non-irrigation model) (pCi/kg wet-weight plant)

r = radioactive decay constant (1/d)

th = hold-up period between harvesting and consumption (d)

,UULJDWLRQ,QJHVWLRQ0RGHOIRU5HVLGHQWRQ&ORVHG/DQGILOO

&RQFHQWUDWLRQLQHGLEOHSDUWVRISODQW. There are two ways for

contamination to enter the plant, direct deposition of irrigation water on the plants and direct

deposition of irrigation water on the soil, with subsequent root uptake into the plant. Each of

these radionuclide concentrations are calculated separately. 

The rate of direct deposition of irrigation water onto plants is calculated using Equation 4.49.

where

Rv,p = rate of deposition of irrigation water onto plant v (pCi translocated/kg-d)

and

IR = average annual application rate of irrigation water (L/m2

-d)

rv = fraction of initial deposition of irrigation water retained on plant v (pCi retained/pCi

deposited)

Tv = fraction of retained activity translocated to edible part of plant v (pCi

translocated/pCi retained)

Cw = radionuclide concentration in groundwater (pCi/L)

Yv = yield of plant v (kg wet-weight plant/m2 )

The radionuclide concentration in plants, due only to direct deposition of irrigation water at the

time of harvest, is calculated using Equation 4.50.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-82

&YLG ' 5YS

 & H

&H W

JY

H

4.50

5V '

,5 ( &Z

3

4.51

&VJ ' 5V

&H

&U W

JY

U

4.52

where

Cv,id = radionuclide concentration in edible part of plant v at time of harvest due to direct

deposition of irrigation water (pCi/kg wet-weight plant)

and

Rv,p = rate of deposition of irrigation water onto plant v (pCi translocated/kg-d)

e = effective weathering and decay constant at harvest (1/d) ( w + r )

w = weathering constant at harvest (1/d)

r = radioactive decay constant (1/d)

tgv = growing period for plant v (d)

Deposition onto soil and subsequent root uptake is also modeled. The rate at which irrigation

water is deposited onto the soil is calculated using Equation 4.51.

where

Rs = rate of deposition of irrigation water onto soil (pCi/kg dry-weight soil- d)

and 

IR = average annual application rate of irrigation water (L/m2

-d)

Cw = radionuclide concentration in groundwater (pCi/L)

P = areal soil density (kg dry-weight soil/m2 )

The radionuclide concentration in the soil at the end of the growing season is calculated using

Equation 4.52. 

where

Csg = soil radionuclide concentration at end of growing season due to direct deposition of

irrigation water (pCi/kg dry-weight soil)

and

Rs = rate of deposition of irrigation water onto soil (pCi/kg dry-weight soil - d)

r = radioactive decay constant (1/d)

tgv = growing period for plant v (d)

The radionuclide concentration in the edible part of the plant at the time of harvest (only from

deposition onto the soil and root uptake) is calculated using Equation 4.53.
Section 4 Recycle and Disposal of Steel

4-83 NUREG-1640

&YSVL ' 0/Y % %LY  ( :Y ( &VJ 4.53

&YLK ' &YLG % &YSVL ( H

&U W

K 4.54

where

Cv,psi = radionuclide concentration in edible part of plant v at time of harvest due to root

uptake (pCi/kg wet-weight plant)

and

MLv = plant soil mass-loading factor for resuspended soil to plant v (pCi/kg dry-weight

plant per pCi/kg dry-weight soil)

Biv = root uptake factor for radionuclide i from soil to plant v (pCi/kg dry-weight plant per

pCi/kg dry-weight soil)

Wv = dry-weight-to-wet-weight conversion factor for plant v (kg dry-weight plant/kg wetweight plant)

Csg = soil radionuclide concentration at end of growing season due to direct deposition of

irrigation water (pCi/kg dry-weight soil)

Finally, the total radionuclide concentration in the edible parts of plants, following deposition via

irrigation and after the hold-up period, is calculated using Equation 4.54.

where

Cv,ih = total radionuclide concentration in plant v after hold-up period (irrigation model)

(pCi/kg wet-weight plant)

and

Cv,id = radionuclide concentration in edible part of plant v at time of harvest due to direct

deposition of irrigation water (pCi/kg wet-weight plant)

Cv,psi = radionuclide concentration in edible part of plant v at time of harvest due to root

uptake (pCi/kg wet-weight plant)

r = radioactive decay constant (1/d)

th = hold-up period between harvesting and consumption (d)

([SRVXUH3DWKZD\'RVHV

This section presents the equations used to calculate pathway doses, using the media radionuclide

concentrations described in Section 4.6.4, as well as other parameters described in other sections.

([WHUQDO([SRVXUH3DWKZD\

When external exposure is due to penetrating radiation from an object such as a drum or pile,

then it is calculated using Equation 4.55 which assumes that a worker is in close proximity to the

object. The parameter GF is a nuclide- and scenario-specific dose rate factor. The values of GF

incorporate information on the photon spectrum of each nuclide and the size, mass, shape, and

elemental composition of objects such as drums or piles of material. For each nuclide and object,

GF has a fixed value. Calculation of GF is discussed in Appendix C. The parameter UGF is a

multiplicative factor which carries the uncertainty information about each GF. The range and
Recycle and Disposal of Steel Section 4

NUREG-1640 4-84

'H[W ' & ( *) ( 8*) ( W

[V ( W\V 4.55

'H[W ' &( 8*) ( ')H[W( 6) ( Z( W

[V( W\V(  4.56

'H[W ' W

RG ( 6)2 ( &VW ( V (8*) ( ')H[W (  %

 W

LG ( 6), ( &VW ( V ( 8*) ( ')H[W ( 

4.57

mode of each UGF are based on uncertainty in the mass of the object and the relative position of

the exposed individual. This equation is used for scenario categories such as handling,

processing, storage, transportation, and product use.

where

Dext = EDE due to external exposure (mrem/y)

and

C0 = radionuclide concentration in the source material at the time scenario begins (pCi/g

waste)

GF = geometry factor for the scenario (mrem/h per pCi/g)

txs = daily number of hours of exposure for scenario (h/d)

tys = annual number of days of exposure for scenario (d/y)

UGF = uncertainty factor for GF (dimensionless)

Federal Guidance Report No. 12 (EPA 1993a) provides dose rate factors for certain simple

geometries such as an infinite plane of soil contaminated to various depths. These values have

been used for scenarios in which the geometry of the source is similar to one specified in Federal

Guidance Report No. 12. Equation 4.56 is used for the disposal activities scenarios.

where

Dext = EDE due to external exposure (mrem/y)

and

C0 = radionuclide concentration in the source material at the time scenario begins (pCi/g

waste)

DFext = external dose rate factor for contamination of infinite depth (mrem-m3

/pCi-s)

SF = vehicle shielding factor (dimensionless)

w = density of waste from cleared material (g waste/m3

)

txs = daily number of hours of exposure for scenario (h/d)

tys = annual number of days of exposure for scenario (d/y)

3600 = unit conversion factor (s/h)

UGF = uncertainty factor for dose rate factor (dimensionless)

Equation 4.57 is used to calculate the dose to a resident on a closed landfill due to both outdoor

and indoor external exposure, where contamination is distributed volumetrically in soil.

Where
Section 4 Recycle and Disposal of Steel

4-85 NUREG-1640

'H[W ' W

RG ( 6)2 % WLG ( 6), ( &JUQG ( ')JUQG ( 8*) (  4.58

'H[W ' *) ( &2 ( W

[V ( W\V (8*) 4.59

Dext = EDE due to external exposure (mrem/y)

and

SFO = shielding factor during outdoor activities (dimensionless)

SFI = shielding factor during indoor activities (dimensionless)

Cs(t) = soil radionuclide concentration at time resident moves onto landfill (pCi/g

dry-weight soil)

s = average density of soil in surface layer (g dry-weight soil/m3

 )

DFext = external dose rate factor for contamination of soil of infinite depth (mrem-m3

 per

pCi-s)

86400 = unit conversion factor (s/d)

tod = annual number of days spent outdoors (d/y)

tid = annual number of days spent indoors (d/y)

UGF = uncertainty factor for dose rate factor (dimensionless)

Equation 4.58 is to calculate external exposure due to ground-surface radionuclide concentrations

of radionuclides. This equation is used for external exposure due to atmospheric releases from a

refinery.

where

Dext = EDE due to external exposure (mrem/y)

and

tod = annual number of days spent outdoors (d/y)

SFO = shielding factor during outdoor activities (dimensionless)

tid = annual number of days spent indoors (d/y)

SFI = shielding factor during indoor activities (dimensionless)

Cgrnd = ground surface concentration of radionuclide at time of scenario (pCi/m2

)

DFgrnd = external dose rate factor for exposure to contaminated ground surface (mrem/s per

pCi/m2

)

UGF = uncertainty on geometry factor (dimensionless)

86400 = unit conversion factor (s/d)

For the transportation scenarios, the potential external doses for the truck driver are calculated

using Equation 4.59.

where:

Dext, = EDE due to external exposure for individual (mrem/y)

GF = geometry factor for the scenario (mrem/hr per pCi/g)

CO = radionuclide concentration in the source material at the time the scenario begins

(pCi/g)

txs = daily number of hours of exposure for the scenario (h/d)

tys = annual number of days of exposure for the scenario (d/y)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-86

'LQK ' & ( 0/ ( 5) ( %5 ( 3) ( ')LQK ( (& ( W

[V ( W\V 4.60

'LQK ' %5GXVW ( W

GG ( 0/GXVW ( &VW ( ')LQK ( 

%  %5RXW ( W

RG & WGG ( 0/RXW ( &VW ( ')LQK ( 

%  %5LQ ( W

LG ( 0/LQ % 3G ( 5)U ( &VW ( ')LQK ( 

4.61

UGF = uncertainty factor for dose rate factor (dimensionless)

,QKDODWLRQ([SRVXUH3DWKZD\

:RUNUHODWHGIn some worker scenarios, a fraction of the material (e.g.,

metal shavings, slag, and EAF dust) would be suspended into the air, making it available for

inhalation by a worker at a steel refinery. The dose due to this exposure pathway is calculated

using Equation 4.60.

where

Dinh = EDE due to inhalation (mrem/y)

and

C0 = radionuclide concentration in the source material at the time the scenario begins

(pCi/g)

ML = mass loading of the source material (mg/m3

)

 RF = respirable fraction of resuspended source material (dimensionless)

BR = breathing rate for moderate physical activity (m3

/h)

DFinh = inhalation dose factor (mrem/pCi intake)

PF = protection factor for respirator (dimensionless)

1E-3 = unit conversion factor (g/mg)

txs = daily number of hours of exposure for scenario (h/d)

tys = annual number of days of exposure for scenario (d/y)

/DQGILOOUHVLGHQW. To estimate inhalation exposure for the scenarios

involving a resident on a closed landfill, Equation 4.61 is used. This equation is used to calculate

the total inhalation dose due to indoor, dusty, and non-dusty activities.

where

Dinh = EDE due to inhalation (mrem/y)

and

Cs(t) = soil radionuclide concentration at time resident moves onto landfill (pCi/g

dry-weight soil)

MLdust = mass loading factor for resuspended soil for dusty activities outdoors (g/m3

 )

MLout = mass loading factor for resuspended soil for normal activities outdoors(g/m3

 )

MLin = mass loading factor for resuspended soil blown indoors from outdoors (g/m3

 )

Pd = indoor dust-loading on floors (g/m2

 )

RFr = indoor resuspension factor (1/m)
Section 4 Recycle and Disposal of Steel

4-87 NUREG-1640

'LQK ' $SOP % $UHV ( ')LQK

4.62

$SOP ' %5LQ ( 5), ( W

LG % %5RXW ( WRG (  (  4.63

BRdust = breathing rate for dusty activities outdoors (m3/h)

BRout = breathing rate for normal activities outdoors (m3

/h)

BRin = breathing rate for indoor activities (m3

/h)

DFinh = inhalation dose factor (mrem/pCi intake)

24 = conversion factor (h/d)

tdd = annual number of days spent on dusty activities outdoors (d/y)

tod = annual number of days spent outdoors (d/y)

tid = annual number of days spent indoors (d/y)

Atmospheric Releases

Inhalation doses resulting from refinery releases are calculated for inhalation of airborne

radionuclides at a residence (from the passing plume) and inhalation of suspended soil (dust). 

Like the external pathway, an individual’s time is divided between offsite and onsite, and while

onsite, indoors and outdoors. The EDE due to inhalation includes the radioactivity inhaled as a

result of the passing plume and from suspension of the soil. This is represented by

Equation 4.62.

where 

Dinh = EDE due to inhalation (mrem/y)

and

Aplm = activity inhaled directly from the passing plume in a year (pCi/y)

Ares = activity inhaled due to resuspension of soil in a year (pCi/y)

DFinh = inhalation dose factor (mrem/pCi intake)

The activity inhaled directly from the passing plume is represented by Equation 4.63. The

average effluent radionuclide concentration used in this equation is calculated using

Equation 4.20.

where

Aplm = activity inhaled directly from the passing plume in a year (pCi/y)

and

BRin = breathing rate for indoor activities (m3

/h)

RFI = indoor fraction of outdoor radionuclide concentration

tid = annual number of days spent indoors (d/y)

BRout = breathing rate for normal activities outdoors (m3

/h)

tod = annual number of days spent outdoors (d/y)

= average effluent radionuclide concentration, averaged over a sector 22.5E wide

(pCi/m3

)

24 = unit conversion factor (h/d)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-88

$UHV ' > %5GXVW ( W

GG ( 0/GXVW % %5RXW ( WRG & WGG ( 0/RXW

% %5LQ ( W

LG ( ^0/LQ % 3G ( 5)U

` @ ( >

&JUQG

V ( 5/ (  @

4.64

'VHF ' & ( ,5 ( ')LQJ ( W

[V ( W\V 4.65

Doses due to inhalation of radionuclides in resuspended soil (dust) at a residence will also be

calculated. A fraction of an individual’s time at the residence will be spent indoors, during which

the individual will breathe dust blown in from outdoors as well as dust tracked inside then

resuspended. During the fraction of the time spent outdoors onsite, the individual’s time will be

divided into time spent engaged in activities that could generate dust (such as sweeping, playing

sports, and gardening) and time spent engaged in other outdoor activities (such as walking,

sunbathing, and washing windows). Equation 4.64 represents the activity inhaled as a result of

resuspension of the soil.

where

Ares = radioactivity inhaled due to resuspension of soil in a year (pCi/y)

and

BRdust = breathing rate for dusty activities outdoors (m3

/h)

BRout = breathing rate for normal activities outdoors (m3

/h)

BRin = breathing rate for indoors activities (m3

/h)

tdd = annual number of days spent on dusty activities outdoors (d/y)

tod = annual number of days spent outdoors (d/y)

tid = annual number of days spent indoors (d/y)

MLdust = mass loading factor for resuspended soil for dusty activities outdoors (g/m3

)

MLout = mass loading factor for resuspended soil for normal activities outdoors (g/m3

)

MLin = mass loading factor for resuspended soil blown indoors from outdoors (g/m3

)

RFr = indoor resuspension factor (1/m)

Pd = indoor dust-loading on floors (g/m2

)

Cgrnd = ground surface radionuclide concentration (pCi/m2

)

s = average density of soil in surface layer (g/m3

)

RL = thickness of soil layer available for resuspension (resuspension layer) (m)

24 = unit conversion factor (h/d)

,QDGYHUWHQW6HFRQGDU\,QJHVWLRQ([SRVXUH3DWKZD\

Material that is resuspended can be deposited as surface contamination. Secondary ingestion

includes ingestion of radioactive material from contaminated hands and food. This is a relatively

poorly defined pathway that is not easily calculated by a detailed description of the mechanisms

involved. The dose from this exposure pathway is calculated using Equation 4.65.

where

Dsec = EDE due to secondary ingestion (mrem/y)

and
Section 4 Recycle and Disposal of Steel

4-89 NUREG-1640

'GZ ' &Z ( 8Z ( ')LQJ (  4.66

'QLQJ ' ',(7Q (  &OYQK ( 8OY % &YHJ QK ( 8YHJ 

% &VW ( 8VRLO (   ( ')LQJ

4.67

C0 = radionuclide concentration in the source material at the time the scenario begins

(pCi/g)

IR = secondary ingestion rate (g/h)

DFing = ingestion dose factor (mrem/pCi intake)

txs = daily number of hours of exposure for scenario (h/d)

tys = annual number of days of exposure for scenario (d/y)

:DWHU,QJHVWLRQ

The drinking-water dose (from ingesting contaminated groundwater) is calculated using

Equation 4.66. The radionuclide concentration in groundwater, Cw, is calculated using

Equation 4.42

where

Ddw = EDE due to ingestion of drinking water (mrem/y)

and

Cw = radionuclide concentration in groundwater (pCi/L)

Uw = human consumption rate of water (L/d)

DFing = ingestion dose factor (mrem/pCi intake)

365.25 = unit conversion factor (d/y)

,QJHVWLRQRI)RRG

(IIHFWLYH'RVH(TXLYDOHQW'XHWR,QJHVWLRQRI1RQ,UULJDWHG

)RRGV35HVLGHQWRQ&ORVHG/DQGILOO

In the non-irrigation model, the dose from ingestion of contaminated plants is calculated using

Equation 4.67.

where

Dn,ing = EDE due to non-irrigation ingestion model of plants (i.e., leafy vegetables and

vegetables) (mrem/y)

and

DIETn = fraction of annual diet from non-irrigated plants (dimensionless)

Cs(t) = soil radionuclide concentration at time resident moves onto landfill (pCi/g dryweight soil)

Clv,nh = radionuclide concentration in edible part of leafy vegetables after hold-up period

(non-irrigation model) (pCi/kg wet-weight plant)

Cveg,nh = radionuclide concentration in edible part of vegetables after hold-up period (nonirrigation model) (pCi/kg wet-weight plant)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-90

'LLQJ ' ',(7Q ( &OYLK ( 8OY % &YHJLK ( 8YHJ 

% &VJ ( 8VRLO ( ')LQJ

4.68

3)Q ' 8OY ( &OYQK % 8YHJ( &YHJQK 4.69

Usoil = human consumption rate of soil (kg dry-weight soil/y)

Ulv = human consumption rate of leafy vegetables (kg wet-weight plant/y)

Uveg = human consumption rate of vegetables (kg wet-weight plant/y)

DFing = ingestion dose factor (mrem/pCi intake)

1000 = unit conversion (g/kg)

(IIHFWLYH'RVH(TXLYDOHQW'XHWR,UULJDWLRQ,QJHVWLRQ0RGHO3IRU

5HVLGHQWRQ&ORVHG/DQGILOO

The EDE for the irrigation ingestion model is calculated using Equation 4.68. All plant

radionuclide concentrations and human consumption rates of plants are in wet-weight while soil

radionuclide concentrations and human consumption rates of soil are in dry-weight.

where

Di,ing = EDE due to irrigation ingestion model of irrigated plants (mrem/y)

and

DIETi = fraction of annual diet from irrigated plants (dimensionless)

Clv,ih = radionuclide concentration in edible part of leafy vegetables after hold-up period

(irrigation model) (pCi/kg wet-weight plant)

Cveg,ih = radionuclide concentration in edible part of vegetables after hold-up period

(irrigation model) (pCi/kg wet-weight plant)

Csg = soil radionuclide concentration at end of growing season due to direct deposition of

irrigation water (pCi/kg dry-weight soil)

Ulv = human consumption rate of leafy vegetables (kg wet-weight plant/y)

Uveg = human consumption rate of vegetables (kg wet-weight plant/y)

Usoil = human consumption rate of soil (kg dry-weight soil/y)

DFing = ingestion dose factor (mrem/pCi intake)

(IIHFWLYH'RVH(TXLYDOHQWIRU7RWDO,QJHVWLRQ0RGHO

The TEDE for the ingestion model assumes that the vegetables are grown on contaminated soil

and are spray irrigated with contaminated groundwater. The total dose, non-irrigation plus

irrigation, is calculated using Equations 4.69, 4.70, and 4.71, below. All plant radionuclide

concentrations and human consumption rates of plants are in wet-weight while soil radionuclide

concentrations and human consumption rates of soil are in dry-weight.
Section 4 Recycle and Disposal of Steel

4-91 NUREG-1640

3)L '%8OY ( &OYLK % 8YHJ ( &YHJLK 4.70 'LQJ ' ',(7 ( 3)Q % 3)L



% &VW ( 8VRLO (   % &VJ ( 8VRLO ( ')LQJ

4.71

'LQJ ' ',(7 ( &OYK ( 8OY % &YHJ K ( 8YHJ 

% &V ( 8VRLO (   ( ')LQJ

4.72

where

PFn = activity uptake from non-irrigation model (pCi/y)

PFi = activity uptake from irrigation model (pCi/y)

Ding = EDE due to ingestion (non-irrigation and irrigation models) (mrem/y)

and

Ulv = human consumption rate of leafy vegetables (kg wet-weight plant/y)

Uveg = human consumption rate of vegetables (kg wet-weight plant/y)

Usoil = human consumption rate of soil (kg dry-weight soil/y)

Clv,nh = radionuclide concentration in edible part of leafy vegetables after hold-up period

(non-irrigation model) (pCi/kg wet-weight plant)

Cveg,nh = radionuclide concentration in edible part of vegetables after hold-up period (nonirrigation model) (pCi/kg wet-weight plant)

Clv,ih = radionuclide concentration in edible part of leafy vegetables after hold-up period

(irrigation model) (pCi/kg wet-weight plant)

Cveg,ih = radionuclide concentration in edible part of vegetables after hold-up period

(irrigation model) (pCi/kg wet-weight plant)

Cs(t) = soil radionuclide concentration at time resident moves onto landfill (from nonirrigation model) (pCi/g dry-weight soil)

Csg = soil radionuclide concentration at end of growing season due to direct deposition of

irrigation water (pCi/kg dry-weight soil)

1000 = unit conversion factor (g/kg)

DFing = ingestion dose factor (mrem/pCi intake)

(IIHFWLYH'RVH(TXLYDOHQW'XHWR,QJHVWLRQRI)RRGVDQG

6RLO35HILQHU\6WDFN5HOHDVHV

The TEDE from ingestion of contaminated plants, and soil is calculated using Equation 4.72.

where

DIET = fraction of annual diet derived from home-grown foods (dimensionless)

Cs(0) = soil radionuclide concentration at time of scenario (pCi/g dry-weight soil) 

Clv,h = radionuclide concentration in edible part of leafy vegetables after hold-up period

(pCi/kg wet-weight plant)
Recycle and Disposal of Steel Section 4

NUREG-1640 4-92

Cveg,h = radionuclide concentration in edible part of vegetables after hold-up period (pCi/kg

wet-weight plant)

Usoil = human consumption rate of soil (kg dry-weight soil/y)

Ulv = human consumption rate of leafy vegetables (kg wet-weight plant/y)

Uveg = human consumption rate of vegetables (kg wet-weight plant/y)

DFing = ingestion dose factor (mrem/pCi intake)

1000 = unit conversion (g/kg)

'HULYHG6XUILFLDO'RVH)DFWRUV

At the time of clearance, residual radioactivity may initially be distributed on the surface or

throughout the volume (mass) of the cleared material. All of the scenarios discussed in this

section treat residual radioactivity as volumetrically distributed throughout the mass of scrap or

refinery product such as slag or baghouse dust. This is because, once the material has been

processed, radioactivity is redistributed throughout the entire volume regardless of its initial

distribution. Even “unprocessed” scrap that has not yet been melted at a refinery can be treated

as volumetrically contaminated. Consistent with industry practices, scrap that is ready for release

would be sized and sorted for efficient loading onto trucks. The residual radioactivity associated

with large piles or truck loads of such scrap would be effectively distributed throughout the

volume even if it were present only on the surfaces of individual pieces of equipment or scrap

metal.

The mass-based dose factors for each recycle scenario indicate the annual dose to an individual

from residual radioactivity distributed throughout the mass of cleared material. The derived

surficial dose factor indicates the annual dose to an individual exposed under the same conditions

from radioactivity that was initially distributed over the surface of the cleared material. A

derived surficial dose factor for each scenario is calculated using the surface-to-mass ratio of the

cleared object or material according to Equation 4.73.

Dose Factor surficial = SM * Dose Factor mass 4.73

where

Dose Factor surficial = derived surficial dose factor (mrem/y per pCi/cm2

)

and

SM = surface-to-mass ratio (cm2

/g)

Dose Factor mass = mass-based dose factor (mrem/y per pCi/g)

The surface-to-mass ratio of objects and materials available for clearance can vary over a wide

range. This is due, in part to the different surface-to-volume ratios of various objects such as

pipes, sheets, and bar stock. It is also the result of different densities among various materials. 

The parameter SM is represented by a distribution of values that incorporate the variability and

uncertainty in the surface-to-mass ratio of objects available for clearance. The distributions used

for the surface-to-mass ratios are chosen as appropriate for each material in the analysis (see

Section 4.8.5). 
Section 4 Recycle and Disposal of Steel

4-93 NUREG-1640

3DUDPHWHU'LVFXVVLRQ

Calculation of potential impacts from reuse or recycle of cleared licensee scrap material depends

on many parameter values. Parameter values are needed for both material flow and dose

assessment models. The material flow parameter values rely on information from the U.S.

secondary steel industry. The parameter values for the dose modeling rely on receptor behavior

information, such as time on a specific job or breathing rate, as well as environmental transport

of radionuclides. Parameter values used for the assessment of impacts are discussed in the

following sections and are tabulated as appropriate in this section. Although not a parameter

value, a description of the selection of radionuclides is also provided in this section.

To support the probabilistic nature of the dose calculations, a range and assumed distributional

shape was used for most parameter values in the dose modeling. Parameter value distributions

are intended to capture uncertainty and variability in the parameter values for the exposed groups

described for each scenario. Each exposed group is relatively homogeneous in characteristics

that are relevant to the calculated dose factors. Therefore, most of each parameter range is due to

uncertainty rather than variability among individuals. 

In some cases, only nominal parameter values are discussed, not the ranges. If only a nominal

value is discussed, it is generally a “most likely value” (i.e., fixed value or the mode of a

distribution), or an estimate of central tendency (e.g., a mean value). A complete listing of

parameter distributions and their characteristics is provided in Appendix B.

The quality of underlying data varies among the parameters used in the analyses. In some cases,

appropriate data were available and were used as a basis for a realistic parameter value range. In

other cases, appropriate data were not readily available, and professional judgement was more

heavily relied on to determine a parameter range. Appendix B describes the data quality

conventions and levels used in this analysis.

5DGLRQXFOLGH6HOHFWLRQ

Several recent sources were reviewed to identify those radionuclides that are most likely to be

found in equipment and material cleared from a NRC licensed facility. Rather than use lists from

previous similar assessments, developing the list independently of previous studies helped ensure

that radionuclides of interest would not be overlooked—or included—because of convention. 

The list (presented in Table 4.9) was compiled from the following five sources:

NRC Correspondence with IAEA (Meck 1992). Radioactive contamination in recycled or reused material is likely to be similar to that of low level waste currently disposed. Radionuclides

listed in this reference constitute greater than 90 percent of the radioactivity disposed of by U.S.

commercial sites during the three years 1988 through 1990.

1992 State-by-State Assessment of Low-Level Radioactive Wastes Received at Commercial

Disposal Sites (Fuchs and McDonald 1993). This document lists those radionuclides that were
Recycle and Disposal of Steel Section 4

NUREG-1640 4-94

disposed of in 1992 at commercial low level disposal sites from various sources: nondirect

(shipments from the generator to the disposal facility through an intermediary), reactors,

academic, medical, industrial, and government.

Radionuclides in United States Commercial Nuclear Power Reactors (Dyer 1995). This

article presents data from several studies on the amounts and types of radionuclide activities

found in nuclear power plant systems and materials (specifically stainless steel). The study

considered only those radionuclides with half-lives longer than 50 days. 

Special activation products in certain materials. Some radionuclides not listed in the previous

three sources are activation products for certain materials. The materials considered for this

study were steel, copper, aluminum, and concrete.

Radioactive progeny of radionuclides on the list. Potentially significant (half life greater than

1 day) radioactive progeny from parent radionuclides identified in the sources listed above were

included explicitly on the list. Radioactive progeny with half-lives of less than 1 day are

excluded from the list because their emissions would be insignificant by the time of the first

exposure scenario, 4 days post-clearance. The effects of progeny radionuclides are included with

the parent radionuclides listed in Table 4.9; these are described in Appendix E.

Radionuclides excluded. Radionuclides with half-lives longer than Th-232 (greater than

1.41E+10 years) were not included in the analysis. Emissions from these radionuclides (e.g.,

Sm-147) would be insignificant during the relatively short time periods that are assumed for the

scenarios. Two radionuclides listed above (Y-90, Kr-85) meet the criteria for inclusion,

however, these radionuclides are not included in final dose tables because it seems unlikely that

they would be found in the equipment or material cleared from a NRC licensed facility addressed

in this study. The short radioactive half-life of Y-90 (64 hours) makes it unlikely that is would

be in any cleared material except in equilibrium with its parent Sr-90, and Kr-85 is a noble gas

and would not exist as residual radioactivity in cleared material.

Table 4.9 Radionuclides of interest for recycle, disposal, and reuse of equipment and materials

H-3 (1) Co-58 (1) Y-91 (3) I-125 (1) Eu-155 (3) Ac-227 (5) U-234 (5)

C-14 (1) Fe-59 (1) Mo-93 (3) Sb-125 (2) Re-186 (2) Th-227 (5) U-235 (2)

Na-22 (1) Ni-59 (2) Nb-93m (3) I-129 (1) Ir-192 (2) Th-228 (2) Np-237 (5)

P-32 (1) Co-60 (1) Nb-94 (3) I-131 (1) Pb-210 (5) Ra-228 (2) Pu-238 (3)

S-35 (1) Ni-63 (1) Nb-95 (1) Ba-133 (2) Po-210 (1) Th-229 (5) U-238 (1)

Cl-36 (1) Zn-65 (1) Zr-95 (1) Cs-134 (1) Bi-210 (5) Th-230 (5) Pu-239 (3)

K-40 (2) Cu-67 (2) Tc-99 (1) Cs-137 (1) Rn-222 (2) Pa-231 (5) Pu-240 (3)

Ca-41 (4) Se-75 (1) Ru-103 (1) Ce-141(1) Ra-223 (5) Th-231 (5) Pu-241 (1)

Ca-45 (1) Kr-85 (1) Ru-106 (1) Ce-144 (1) Ra-224 (5) Th-232 (1) Pu-242 (6)

Cr-51 (1) Sr-85 (2) Ag-108m (3) Pm-147 (1) Ac-225 (5) Pa-233 (5) Am-241 (2)

Mn-54 (1) Sr-89 (3) Cd-109 (2) Eu-152 (2) Ra-225 (5) U-233 (5) Cm-242 (3)

Fe-55 (1) Sr-90 (1) Ag-110m (1) Eu-154 (2) Ra-226 (1) Th-234 (5) Cm-244 (3)

Co-57 (1) Y-90 (5) Sb-124 (1)

(1) Meck (1992); (2) Fuchs and McDonald (1993); (3) Dyer (1995); (4) Special activation product; (5)

Radioactive progeny; (6) added in review process
Section 4 Recycle and Disposal of Steel

4-95 NUREG-1640

0DWHULDO)ORZ0RGHO

The parameter values used in the material flow model are presented in Appendix B and are based

on the information presented in Sections 4.2 and 4.3 of this report. The values are based on

recycling material cleared from a NRC licensed facility for 1 year in the existing, commercial

iron and steel industry.

6FHQDULR7LPLQJ

This section presents the basic assumptions used in defining the nominal time periods for each of

the recycle scenarios. All exposure scenarios were derived from the material flow conceptual

modeling, and scenarios were assumed to occur at specific points in time following clearance. 

This basis was used to define the parameter ts, the time from clearance of material to the time the

scenario begins. Where a reference was used as a basis for the assumed time period, it is cited. 

If no citation is given, general knowledge of practices gained from talking with industry

personnel combined with professional judgement was used as the basis. A uniform distribution

was used with a range of ±50% of the nominal value. The following is a list of basic

assumptions that were used in developing nominal values for the timing of the scenarios:

Scrap Handling:

C All scrap metal is assumed to be initially taken to a scrap dealer. It takes 4 days for the

scrap metal to reach the scrap dealer.

C The scrap metal remains at the scrap dealer for a period of 7 days prior to reuse or

disposal, and 25 days for scrap metal that is recycled. 

Refining and Processing:

C For recycled scrap metal the refining process and associated product manufacture, final

processing, and any onsite storage at the refinery is assumed to take a total of 11 days for

an EAF (O'Donnell et al. 1978) and 15 days for BOF.

C Following initial processing, BOF products undergo further processing before use; this

secondary processing, plus storage and handling, is assumed to take 22 days.

C EAF metal products are distributed to the public upon completion of the refinery process

while BOF products are distributed for use upon completion of the secondary process. 

Distribution for both products is assumed to take 7 days.

C Releases of radionuclides in the atmospheric effluent from an EAF or BOF refinery occur

at the time the scrap is refined, i.e., 29 days after clearance. 
Recycle and Disposal of Steel Section 4

NUREG-1640 4-96

Use and Disposal:

C An EAF metal product is used for 30 years, based on an assumed use in the construction

industry. Use of a BOF metal product is 10 years, based on an assumed general purpose

use (IAEA 1992).

C EAF and BOF refinery slag and baghouse dust are produced at the time refining occurs,

29 days after clearance of scrap metal from the licensee.

C Refinery slag that is sold for subsequent use is processed at the refinery 3 days after

production and leaves the refinery in another 2 days. Slag is assumed to be used within

2 days after distribution and is used for a period of 30 years. Once the period of use is

completed, the products are disposed in a sanitary landfill. Slag that is to be directly

disposed is held at the refinery for 7 days, at which time it is transported to a disposal

facility. The slag is assumed to be disposed immediately following handling at a sanitary

landfill.

C The two management options for EAF baghouse dust that are being analyzed in this

report are direct disposal in a hazardous landfill and use as an additive in fertilizer. If the

dust is to be disposed of, it is transported within 3 days after production. Handling and

processing of the dust takes 4 days, at which time the dust is disposed in a hazardous

waste landfill. Electric arc furnace dust that is to be processed as fertilizer is sent to the

processor 3 days after production. Processing takes 3 days, and the fertilizer is distributed

for use and is used within 1 day.

C BOF baghouse dust is disposed of onsite or sent to a sanitary disposal facility after 7 days. 

Storage and handling take 4 days, at which time disposal occurs.

Post Disposal:

C A sanitary landfill operates for 40 years.

C A hazardous landfill operates for 30 years.

C Disposed items are placed in the landfill at the midpoint of the landfill operating period.

C Post-closure monitoring of landfills is done for 30 years.

C A disposal site is available for potential residential use after post-closure monitoring

ends.
Section 4 Recycle and Disposal of Steel

4-97 NUREG-1640

'RVH(YDOXDWLRQ

Values for radionuclide-dependent parameters (e.g., r, DFing) are taken from Federal Guidance

Report 11 (EPA 1988) and are tabulated in Appendix B. All other parameters are either

radionuclide-independent or material-dependent, and are discussed below; values for these

parameters are also listed in Appendix B.

,QSXW5DGLRQXFOLGH&RQFHQWUDWLRQVIURPWKH0DWHULDO)ORZ

The undecayed radioactivity concentration in the source material, Cx, is used as the source

material input as the source material input radioactivity concentration for scenario evaluations. 

This parameter is radionuclide dependent and is calculated in the material flow modeling. Table

B.8 lists the sources for Cx as they appear in the mathematical modeling of the material flow

(e.g., Cp, radioactivity concentration in metal product after the refining process).

([SRVXUH'XUDWLRQ

The duration of exposure is the time that the individuals in the exposed group are assumed to

spend in the scenario conditions that result in exposure to cleared material. The number of hours

of exposure in each scenario is calculated as the product of the parameters txs (h/d) and tys (d/y). 

Values for both these parameters are tabulated in Appendix B. All scenarios incorporate

uncertainty via the parameter for hours per day, txs, and the parameter tys (d/y) is fixed. The workrelated scenarios use a fixed value of 250 d/y for tys, and all other scenarios use a fixed value of

350 d/y. 

:RUNUHODWHG6FHQDULRV

The maximum number of hours in a typical work year was limited to the fraction of time that a

worker would reasonably spend performing the work that would result in exposure to cleared

material during a calendar year. The fraction is based on the amount of time a worker would be

working directly with cleared material plus the time working in the vicinity of the material. 

Generic scenarios for industry workers (scrap handling, refinery workers, and manufacturing

workers) use a range of values that reflects varying operational practices among scrap yards and

refineries. Even though the members of the exposed groups in these scenarios are dedicated to

handling scrap or refinery products, it is reasonable to assume that any individual would actually

spend less than a full working day handling material with residual radioactivity. Other activities

during a typical day would include checking out equipment, driving equipment back and forth

between parking, storage, and handling areas, refueling equipment, waiting for vehicles to load

or unload, receiving instructions or plans for work to be done, and performing other duties. 

Therefore a range that often does not include the maximum number of hours in a work day was

determined to reflect the likelihood of these other activities.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-98

The specific handling scenarios incorporate a range involving a much smaller number of hours in

an average workday. This is reasonable because there is a much smaller volume of material

being handled (EAF baghouse dust) as compared to the other worker scenarios.

The single product use scenario that involves workers (“Roadbed construction activities”) would

involve considerable variability in the daily number of hours spent using and in the vicinity of

refinery slag. These workers would likely not spend an entire year constructing roads using

refinery slag, because roads are also constructed using materials other than slag (e.g., gravel). 

Also, road construction is a seasonal activity in many northern areas of the U.S. 

An exposure duration for scenarios involving disposal of material with residual radioactivity was

determined using the capacity of typical landfills and the amount of material available to be

disposed in a geographic area. These two values (capacity and amount of material available)

were ratioed, and the material-specific ratio was multiplied by the number of hours in a working

year to estimate values for each material of interest. 

The basic assumption for the duration of exposure for commercial drivers of trucks carrying

cleared material or any of the co-products of refining was that these individuals were employed

full-time in a trucking job. Specific assumptions for the scenarios in this analysis were

developed after talking with individuals in the steel transport industry. It is common for these

drivers to work up to 50 hours per week; this is supported by statistics from the Bureau of Labor

Statistics (BLS 1998), which indicate that local truck drivers frequently work 48 hours or more a

week. It was also determined that it was reasonable to assume that there are sufficient amounts

of scrap, slag, baghouse dust, and refined steel for some drivers to spend a majority of their time

hauling this material (not necessarily all cleared material, however). These drivers would be

hauling a single material a maximum of half of their workdays (i.e., full loads only one-way). 

Some drivers may haul one material (e.g., scrap) to a refinery and load their trucks at the refinery

with another material (e.g., slag) for a "return" trip. 

A most likely value was determined to be one-half of a 40-hour work week, with a reasonable

minimum value incorporating the assumption of less time for the drivers that do not spend all of

their time hauling steel industry material. A maximum value was used to represent one-half of a

50-hour work week.

Values for a driver of a vehicle were used to model a taxi driver or other commercial driver (e.g.

small delivery van). A range from one-half to a full work day with no most likely value was

used.

1RQZRUNHUVFHQDULRV

Similar to the worker scenarios, the non-worker scenarios incorporate uncertainty into exposure

duration via the parameter for hours per day, while the value for days per year was held constant. 

Most of the non-worker scenarios involve use of refinery co-products, most commonly refined

steel products. Duration times for the generic small object and large object scenarios were
Section 4 Recycle and Disposal of Steel

4-99 NUREG-1640

developed to include those individuals who spend a large fraction of their work day or residential

time near these objects (e.g., machine tools, office furniture, and household appliances or

furniture). The most likely value for these scenarios is one-half of a typical work day. A range

of 2–8 hours per day would cover a variety of potential exposure situations in both residential

and occupational settings.

The scenario involving a small object close to the body involves a wide range of exposure

duration because of the variety of potential exposure scenarios (e.g., belt buckles, tools). The

scenario involving individuals inside a basement (or other concrete structure) could involve

occupational or residential settings, and a range was chosen to incorporate both of these settings. 

A most likely value was chosen to represent a residential setting; this was also used as the

maximum value in the parameter range. Use of a roadway containing refinery slag was assumed

to involve regular, short-term use. Values were for a range to represent a commuter using the

same route every work day.

For those exposure scenarios that occur in a residential setting (e.g., person inside a basement

made with slag) a year’s duration consisting of 5600 hours is assumed. For residential landfill

scenarios and the atmospheric release scenarios where an individual spends time indoors as well

as outdoors, additional exposure duration parameters are needed. The number of hours spent on

indoor, outdoor, and dusty activities are represented by tid, tod, and tdd, respectively, and are listed

in Table B.7. Nominal values for these parameters were based on values in Kennedy and Strenge

(1992); distributions for the parameters were subjectively developed, based on professional

judgement and the scenario definition.

0DWHULDO'HQVLWLHV

Four fixed values were used for the density of waste, w: 1) For the waste products that are

similar to soil (i.e., BOF baghouse dust), a value identical to the nominal value used for s; 2) For

those waste products that are similar to metal (e.g., scrap metal and refined metal product), a

value derived and used for bulk density in the calculation of the geometry factors for metal

products was used; 3) For immobilized EAF dust, a value of 1.36E+6 g/m3

 was used (Logan

1993); 4) For the disposal of slag the same density that was used for slag in a pile was used for

slag in a landfill.

Three approaches were used to estimate a range for the bulk density of slag as used in various

scenarios: industry contacts, appropriate references, and a theoretical approach. The three

approaches result in a range of estimates that differ by a factor of a little over 3× (1.19 g/cm3 -

3.9 g/cm3

). Two estimates of bulk density values were needed for use in the scenarios involving

slag pile and roadbed, because the bulk density of slag would be different in the two scenarios. 

The information from industry contacts was judged to be the best source and was therefore

emphasized, because it is specific to EAF steelmaking slag and does not depend on the use of

assumptions. One literature source (IAEA 1992) does not provide justification for the value

used, nor does it give detailed information about the type of slag (e.g., furnace source). The

Handbook of Chemistry and Physics (CRC 1992) lists a value for slag bulk density, however it
Recycle and Disposal of Steel Section 4

1

Personal communication M. McKenzie-Carter, SAIC and Alexander Mill Service, Plymouth, UT, May 14, 1996.

NUREG-1640 4-100

does not list the type of slag (e.g., steelmaking, pig iron, other industry). The value listed in

Lankford et al. (1985) is specific to steelmaking slag, but does not give information on type of

furnace. Finally, a theoretical value was calculated by weighting the percentage of each chemical

constituent of EAF slag, then summing and accounting for the void space presumed to be present

in bulk slag. Although this approach is specific to EAF slag, it depends on an uncertain

assumption for the porosity of the bulk slag. 

To estimate values for the bulk density of a slag pile, the information from industry contacts was

emphasized. The industry values are generally lower than those obtained from other sources,

however it was judged that these slag processors would provide a more accurate value for bulk

density of slag in a pile, since that is what they deal with on a daily basis. One possible

explanation for the lower bulk density values from the slag processors is that the slag in their

piles has expanded, due to hydration of free lime or magnesia in the slag (Lankford et al. 1985). 

A fixed value of 2.0 g/cm3 was estimated by first obtaining an average value from the slag

processors (1.74 g/cm3), then adjusting it upward because of the literature value of 2.38 g/cm3

(Lankford et al. 1985) (a value of 2.0 is a round number that is approximately midway between

1.74 and 2.38). 

The slag as used in a roadbed would be different in two key respects from the slag in a slag pile: 

it would consist primarily of smaller pieces (0–1 in.1), and it would likely be compacted during

road construction. The single density value for the smallest size fraction found in a survey of

slag processors was used as the fixed value (2.4 g/cm3). Although this is the highest value

obtained from any of the slag processors, and it is also the maximum value for steelmaking slag

in general (Lankford et al. 1985), it was used because of the nature of the use of slag in this

scenario (small pieces and highly compacted).

0L[LQJRI&OHDUHG0DWHULDO

A basic assumption of this analysis is that material that is cleared from a licensee would enter the

general commercial sector. Any cleared material or refinery products could therefore be mixed

with non-cleared, but otherwise similar material. This likelihood is incorporated into the analysis

in three ways: 1) mixing of scrap that does not undergo any melting at a refinery and mixing of

scrap that is melted at a refinery; 2) mixing of refinery slag when used as an additive in concrete;

and 3) mixing of material that is disposed. These three concepts are discussed in the following

subsections.

0L[LQJRI&OHDUHG6FUDS

A “mixing factor” was calculated and is described in Appendix D. The mixing factor is a

multiplicative factor that was used to incorporate the mixing of cleared scrap with other, similar

scrap. The mixing factor range was used to modify the exposure duration in the scrap handling
Section 4 Recycle and Disposal of Steel

1

 Personal communication from W. C. Thurber of S.C. & A.

4-101 NUREG-1640

and scrap disposal scenarios. These scenarios model the direct use of scrap (no melting). Most

other scenarios (except as described in next subsections) incorporate mixing by the use of

appropriate values for cleared scrap and other scrap in the material flow model.

'LOXWLRQRIUHILQHU\VODJXVHGLQEDVHPHQWFRQVWUXFWLRQ

An explicit dilution factor (DF) is used in the scenario involving use of refinery slag in the

manufacture of concrete that is used in the construction of a basement or other building structure. 

This is to account for the amount of slag used in the commercial process where slag is blended

with other cement ingredients, heated, and results in a cement clinker that can be ground to the

required size. Based on information1

 that was obtained from the cement industry, a triangular

distribution for DF from 0.5% to 3% was used, with a most likely value of 1.5%. For this one

scenario, the parameter DF is used multiplicatively in Equation 4.55 to modify the radionuclide

concentrations.

0L[LQJRIZDVWHLQWKHODQGILOO

In order to estimate the fraction of a landfill that could consist of waste from disposing of

contaminated scrap or byproducts of recycling, landfill mixing factors were calculated for the

resident and disposal activities scenarios. To make reasonable estimates, a bounding case for

slag was first examined. It was calculated that if all of the slag generated from refining all of the

slightly contaminated scrap steel likely to be cleared from a NRC licensed facility were disposed

in a single landfill, it would comprise roughly 4% of the capacity of an average-sized sanitary

landfill (40,000 m3

 out of 1 million m3 capacity). This bounding analysis is unreasonable by

itself, because industry practice and the economics of landfill disposal make it extremely unlikely

that all slag from contaminated scrap recycle would be disposed in a single landfill. However,

the unpredictable nature of future scrap cleared practices by a NRC licensed facility and the

varying sizes of landfills must be considered. If the assumption is arbitrarily made that no more

than 2% of the slag from scrap recycling were disposed of at a single landfill, the total amount

disposed in a representative facility would be about 0.2% of capacity (2000 m3). This value

appears to be reasonable, and is consistent with the “reasonable maximum case” contained in

Appendix G of EPA (1997a). In evaluating regional dilution of NRC licensee scrap, it is

postulated in this reference that 22,500 t (24807 tons) of scrap could be refined at a single

reference mill. Using a slag production rate of 15%, this would result in 3,375 t (3721 tons)

(1,688 m3

) of slag amounting to 0.15% of capacity for an average landfill. The regional

distribution of power plants and steel mills makes it unlikely that this rate of refining could be

sustained for multiple years. If the total slag from scrap recycling disposed of at a single landfill

were twice the “reasonable maximum” 1-year value, the result would be 6,750 t (7,442 tons)

(3,375 m3) or 0.31% of capacity. 

Based on this rationale, it is unlikely that the amount of slag from refining contaminated steel

present in a single landfill would exceed a few thousand cubic meters and is likely to be very
Recycle and Disposal of Steel Section 4

NUREG-1640 4-102

much less. However, the basic assumption behind the resident-on-landfill scenarios is that

significant landfill disposal of slag from refining licensee scrap occurs for at least one licensed

facility. Therefore, an estimate of 0.2% is used as the per cent of a landfill capacity comprised of

slag that is a byproduct of recycling cleared steel scrap. 

Using this rationale, and appropriate partitioning factors for other byproducts, the following

landfill mixing fractions were estimated and used in the assessments of scenarios for residents on

closed landfills: 

Steel slag: 0.2% of landfill capacity

Steel scrap: 0.7% of landfill capacity

Baghouse dust: 0.02% of landfill capacity

These values formed the basis to estimate a range for the parameter FW, fraction of the volume

of a landfill that is from cleared material. Ranges were developed by using values ±50% of the

values listed above. 

([WHUQDO([SRVXUH3DUDPHWHUV

The parameter UGF was used to account for uncertainty in external exposure rates. The fixedvalue external dose factors used in this analysis come from two sources: Federal Guidance

Report No. 12, and values calculated using the code Monte Carlo N-Particle (MCNP) specifically

for this analysis. Federal Guidance Report No. 12 values were used in scenarios involving large

areas of contaminated soil or similar materials that can be treated as a infinite planar source. The

MCNP values were used for scenarios where finite objects of shapes and composition were

modeled. The UGF is a multiplicative factor based on an evaluation of the circumstances

described in each scenario. A discussion of the calculation of GFs and development of

distributions for UGF are both discussed in Appendix C, as is a listing of the GF values used. 

Values for UGF are tabulated in Appendix B.

Shielding factors were also used in this analysis to calculate the external exposure dose factors. 

A vehicle shielding factor, SF, was used in the disposal activity scenarios to account for the

likely shielding afforded by the large equipment used at landfills (e.g., loaders and bulldozers). 

Based on interviews with equipment manufacturers and landfill operators, a geometric model

was developed to characterize the effective shielding for operators of this type of large

equipment. Transmission factors were developed sufficiently to determine a reasonable

triangular distribution from 0.3 to 0.7, with a most likely value of 0.5. These values were used

multiplicatively to reduce the external exposure dose factors for workers handling waste at

landfills. 

Shielding factors were also used for the types of activities in residential scenarios. Values for the

parameters SFI and SFO were developed from the values used in Kennedy and Strenge (1992)

because they represented reasonable values for a generic member of the public.
Section 4 Recycle and Disposal of Steel

4-103 NUREG-1640

The external exposure pathway in the atmospheric release scenario uses a parameter for the

period of long-term buildup for activity in soil, tb. A fixed value of 5.48E+3 d is used for this

parameter and was taken from NRC Regulatory Guide 1.109 (NRC 1977).

,QKDODWLRQ([SRVXUH3DUDPHWHUV

This section presents a description of the basis for parameter values for those radionuclideindependent parameters used in the calculation of inhalation exposure, including those that

address mass loading, and breathing rate.

Breathing Rate

Two methods used to estimate breathing rates for dose assessments are the tidal volume and

frequency method (ICRP 1974, ICRP 1994, and EPA 1989a) and the method using oxygen

demand based on metabolic conversion of food nutrients (Layton 1993). Although the latter

method is takes into account variations in oxygen uptake efficiency, lung physiology, and

metabolic efficiency among individuals, it is not as widely accepted as the tidal volume method. 

Both the EPA and the ICRP base their average hourly breathing rates on the tidal volume

(ml/breath) and the frequency (breaths/minute) for various activity levels, and that is the method

adopted for this study.

The inhalation rates for different levels of activities in ICRP (1994) and EPA (1989a) were

reviewed to determine a reasonable range to use for breathing rate in the scenarios in this

analysis. Both reports are based on tidal volume (ml/breath) and frequency (breaths/min). The

EPA listing is detailed and allows more interpretation of the values, and was judged to be more

representative of workers and members of the public. Therefore, the EPA values were

emphasized. Furthermore, the values for males were used because it is more likely that the jobs

described in the exposure scenarios would be performed by males. The range for breathing rate

given in EPA (1989a) is from 0.7 m3

/h during resting to 5.1 m3/h for very heavy activity. The

range in ICRP (1994) is from 0.45 m3

/h for resting to 3.0 m3/h for heavy exercise. From these

ranges, two triangular distributions were developed, one for outdoor activities and the other for

indoor activities. The range used for outdoor activities is from 0.6 m3

/h to 3.0 m3/h, and the

range for indoor activities is 0.5 m3

/h to 1.2 m3/h. Both distributions use a most likely value of

1.2 m3

/h, consistent with Volume 1 of NUREG/CR 5512 (Kennedy and Strenge 1992) and some

of the scenarios values in Volume 3 of NUREG/CR-5512 (Beyeler et al, 1996). 

Respirator Use

Only one work-related scenario, refinery baghouse operations, presents hazards that would

typically require a worker to wear a respirator. In the refinery work environment, the inside of a

baghouse represents a hazardous environment. The presence of airborne baghouse dust in a

confined and congested area requires that precautions be taken; typically including protective

clothing and a respirator. Therefore, in order to be realistic, use of a respirator is assumed. 
Recycle and Disposal of Steel Section 4

1

Personal communication, M. Anderson, SAIC with Vinnie Caesar, Midwesco Filter Resources, Inc., Oct. 1996.

2

Personal Communication, S. Jones, SAID with Bill Fergeson, Arkansas Steel, May 9, 1996.

3

Personal Communication, S. Jones, SAID with Many Morelac, Border Steel, April 26, 1996.

4

Personal Communication, S. Jones, SAID with Al Pulliam, Bayou Steel, April 25, 1996.

NUREG-1640 4-104

Based on conversations with industry representatives1,2,3,4 and the fact that there are regulations

requiring the use of respiratory protection while working in dusty and hazardous environments, a

worker entering the baghouse without a respirator is not considered realistic and, therefore, is not

considered. Requirements stated in 42CFR84 list minimum efficiencies for three levels of

respirators (95%, 99%, and 99.97%). According to Caesar1 respirators in the steel recycle

industry are selected and approved by management based on the physical and chemical properties

of the air contaminants that will be encountered and the concentration level likely to be

encountered by an employee. However, there are no reliable data on which to base a range, and

it was judged that a range biased toward the lower end of efficiencies would be most likely. In

order to account for use of less efficient respirators, as well as ill-fitting respirators, a range of

90% to 99.7% was used for respirator efficiency.

Mass Loading and Respirable Fraction

The mass loading (ML) factor used for the inhalation exposure pathway calculation is difficult to

estimate. The usual approach to estimating intake via mass loading models assumes that the

concentration of radioactivity in airborne particulates is the same as in the material from which

those particulates are generated. In this case, airborne radioactivity is assumed to be associated

exclusively with particulates originating from the scrap material or recycle product regardless of

any other sources of particulates at the job site. For the scenarios that include the inhalation

pathway, the mass loading factor used for the inhalation exposure pathway calculation must be

typical of dusty work environments like that which would be found around a construction site. 

The mass loading factor approach was used so that the concentration of radionuclides in the dust

could be directly related to an air concentration by use of an assumed mass of dust particulates in

the air at the receptor location. A mass loading factor is typically used in environmental

evaluations to relate soil concentrations to air concentrations. Although recycle scenarios are not

strictly an environmental setting, and the dust volume is not in situ soil, the use of a mass loading

approach is valid because it relates the source radioactivity concentration to an air radioactivity

concentration using an appropriate value for dust loading. 

The respirable fraction of resuspended material is another key parameter for the inhalation

pathway. Fugitive emissions from the steel industry include open dust sources such as raw

material storage piles from which emissions are generated by the forces of wind and machinery

acting on exposed aggregate materials. The EPA has sponsored the Midwest Research Institute

to measure particulate emissions and particle size distributions from a variety of sources

including unpaved roads of mixed slag and soil in the vicinity of steel mill slag piles (Cowherd et

al. 1979). Measurements include mass loading near areas disturbed by vehicular traffic and in

undisturbed upwind areas.
Section 4 Recycle and Disposal of Steel

4-105 NUREG-1640

The gross values presented in Cowherd et al. (1979, Table 3-4) were used to estimate mass

loading and respirable fraction (data from roads treated for dust suppression were not included;

values for profiler samplers, cascade impactors and hi-vol samplers (5m) were pooled). The

summary statistics for these values are as follows:

n = 35 , range = 2.1 mg/m3

 to 13.6 mg/m3, mean ± stnd. dev.= 7.0 ± 3.2 mg/m3.

In addition, upwind background measurements were reported for representing undisturbed areas

in the same vicinity. Values in Cowherd et al. (1979, Tables 3-4 and 3-14) were used to estimate

background levels of particulates. The summary statistics for these values are as follows:

n = 13, range = 0.43 mg/m3 to 1.2 mg/m3, mean ± stnd. dev.= 0.79 ± 0.23 mg/m3.

Based on the information presented here and in Cowherd et al. (1979) a triangular distribution

between 1.3 mg/m3

 and 7.4 mg/m3, and a mode of 3.9 mg/m3 was calculated and used for the

mass loading factor for dusty work-related scenarios (i.e., slag worker, scrap handling, dust

handling, refinery product handling, road construction scenarios, and disposal activities with

BOF dust and slag). This was calculated by incorporating an assumption that an individual

spends one-half of the time upwind (.79 mg/m3) and one-half in a high concentration area

(7 mg/m3).

Cowherd et al. (1979) also contains estimates of the mass median diameter, the fraction less than

30 μm, the fraction less than 5 μm, and the fraction greater than 50 μm. Linear interpolation

between the fractions less than 30 μm and less than 5 μm was used here to estimate the fraction

less than 10 μm. Respirable particles are considered to be less than 10 μm. From the summary

statistics for these interpolated values listed below, a triangular distribution between 0.23 and

0.42 was used, with a mode of 0.33 was used for the respirable fraction, RF, when it is applied to

resuspended slag.

n = 8, range = 0.23 to 0.42, mean ± stnd. dev.= 0.33 ± 0.07.

One special case scenario (refinery baghouse operations) occurs in an extremely dusty

environment. Mass loading inside a baghouse is apparently not a commonly measured value, and

inquiries to steel refineries did not result in locating any measured values. Some data are

available, however, to support an estimation of this parameter value, i.e., measurements of the

respirable fraction of dust; this was used to estimate the mass loading parameter value. The mass

loading factor approach was used so that the concentration of radionuclides in the dust could be

directly related to an air concentration by use of an assumed mass of dust particulates in the air

inside the baghouse. A mass loading factor is typically used in environmental evaluations to

relate soil concentrations to air concentrations. Although a baghouse is not strictly an

environmental setting, and the dust volume is not in situ soil, the use of a mass loading approach

is valid because it relates the dust source radioactivity concentration to an air radioactivity

concentration using an appropriate value for dust loading. Background levels of dust can be

estimated from environmental settings, where ambient air concentrations of dust particulates can
Recycle and Disposal of Steel Section 4

NUREG-1640 4-106

range up to 254 μg/m3 in urban locations, and up to 79 μg/m3 in nonurban locations

(Healy 1980). A value of 100 μg/m3

 is often used for predictive purposes (e.g., Anspaugh et

al. 1974), the EPA has used 100 μg/m3 for screening calculations (EPA 1977), and often a value

of 200 μg/m3 is recommended for generic evaluations for sites that may include some mechanical

disturbance (Healy 1980). 

The basic approach used to estimate the mass loading and respirable fraction of dust for the

baghouse worker was based on a limited amount of industry knowledge, measured data for

respirable fraction of dust, and regulatory limits. The industry knowledge consists of an

understanding that a steel refinery generates a large amount of dust [on the order of 15 kg dust

per metric ton of steel produced, which is equivalent to several thousand metric tons per year for

a typical steel refinery (EPRI 1993)], and therefore a large mass of dust must pass through a

refinery baghouse.

Applicable data are presented in Jeffery and Vay (1986), which provides particle size data for

emissions from EAF, BOF, and other processes. They cite a value of 0.58 for the mass fraction

less than 10 μm from melting and refining carbon steel in an EAF. Szabo and Gerstle (1978)

provides particle size data for particulate emissions from EAF and BOF processes, citing a value

of 0.70 for the mass fraction less than 12 μm and 0.61 for the fraction less than 8 μm. 

In addition, Cass and Langley (1977) provides data from a controlled experiment that measured

dust characteristics from an EAF refining carbon steel. Measurements included particle size and

mass at both the inlet and outlet of a baghouse. Ten separate experiments were run. The mass

fraction less than 10 μm varied from a minimum of about 0.40 to a maximum of about 0.70 with

a mean of about 0.60. These values are approximate because they were interpolated from graphs.

Finally, the regulatory information considered consists of an occupational Safety and Health

Administration (OSHA) limit for the Permissible Exposure Limit for total suspended particulates

at a work environment: the 8-hour time-weighted-average value for total dust allowed by OSHA

is 15,000 μg/m3

, and the allowed respirable fraction is 5,000 μg/m3 (NIOSH 1990). This

suggests an implied RF value of 0.33. 

From these sources, a triangular distribution between 1 mg/m3

 and 15 mg/m3 was used for mass

loading in a baghouse, with a mode of 10 mg/m3

. Likewise a triangular distribution was used for

respirable fraction in this scenario, with a range of 0.4 to 0.7, and a mode of 0.6. This

distribution was also used for scenarios involving handling EAF or BOF baghouse dust. 

To put these estimates in context, they can be compared to values used in similar analyses. The

range derived for use in this analysis for airborne dust concentration is within the range of

0.1 mg/m3

 to 40 mg/m3 used in previous similar analyses [e.g., fixed value of 0.1 mg/m3 used in

IAEA (1992); fixed value of 5 mg/m3

 used in O'Donnell et al. (1978); fixed value of 40 mg/m3

used in EPA (1997)]. 
Section 4 Recycle and Disposal of Steel

4-107 NUREG-1640

Soil Suspension

Seven additional parameters are needed to model the suspension of soil for the residential

scenarios. The mass loading values for indoor, outdoor, and dusty activities (i.e., MLin, MLout,

MLdust) as well as the indoor dust-loading on floors, Pd, and the indoor resuspension factor, RFr

,

are taken from Kennedy and Strenge (1992). For refinery atmospheric release scenarios, when

the plume passes over a house or building, only a fraction of the material in the plume enters the

building, and is therefore respirable by the resident. Yu et al. (1993) estimated that the dust level

inside a building is about 40% of that outdoors. Because conditions within a plume are similar to

those with suspended soil, a value of 0.40 is used for the indoor fraction of outdoor radioactivity

concentration, RFI. 

For atmospheric release scenarios, the thickness of the soil layer that is available for suspension,

RL, determines the amount of radioactivity that is suspended from the surface. The types of

activities that could cause suspension are walking or driving on packed dirt or roadways. A

value of 1 cm (0.01 m) is used for RL, based on the assumption that the particles that are

deposited on the soil during an atmospheric release would not be mixed into the soil under

normal conditions. 

,QDGYHUWHQW6HFRQGDU\,QJHVWLRQ([SRVXUH3DUDPHWHUV

It is reasonable to include the secondary ingestion exposure pathway for all scenarios where

inhalation exposure is assumed, because of the presence of dust in an industrial environment. If

there is a resuspension of dust that is available for inhalation, then it is reasonable to assume that

inadvertent secondary ingestion can also occur. The range used for the secondary ingestion, IR,

of surface deposited material (e.g., slag, dust, or metal shavings) is based primarily on the review

of surface-contamination ingestion data and soil ingestion rates contained in Volume 1 of

NUREG/CR-5512 (Kennedy and Strenge 1992). The overall range cited in NUREG/CR-5512

for secondary soil ingestion is from 0 mg/d to 200 mg/d. These values were interpreted to be

based on a variable number of hours per day, based on the assumed source of data (e.g., 8 hours

for worker data, longer for resident data). From these data, a uniform distribution over the range

of 2.1 mg/h–30 mg/h was used in this analysis. The upper-end value was selected following

discussions with EPA contractors regarding consistency with the analyses being conducted for

the EPA (EPA 1997a). 

'ULQNLQJ:DWHU,QJHVWLRQ([SRVXUH3DUDPHWHUV

Radionuclide-independent parameters used in the evaluation of the drinking water exposure

pathway include those that model the transport of radionuclides to the groundwater as well as

human consumption. All the scenarios that include the drinking water ingestion exposure

pathway assume that box 2 (unsaturated layer) and box 3 (aquifer) are initially free of

contamination. Therefore, A2(0) and A3(0) are set equal to zero.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-108

For several parameters used in the drinking water ingestion exposure pathway, it was determined

that the values used in Kennedy and Strenge (1992) were appropriate for use as point estimates or

estimates of central tendency for the drinking water exposure dose factor analysis (see

Appendix B for values used). The parameters Ti (time period for infiltration and irrigation) and

Tp (time period for pumping) were both fixed at the values used in Volume 1 of NUREG/CR5512 (Kennedy and Strenge 1992). The Volume 1 NUREG/CR values for porosity, n1 and n2,

and saturation ratios, f1 and f2, were used as most likely values in triangular distributions. The

Volume 1 NUREG/CR values for Ac (area of land under cultivation) and I (infiltration rate) were

used as the geometric means of lognormal distributions. 

For the parameter Uw, analysis of survey data has shown that tap water averages about 60% of

total water consumption (Roseberry and Burmaster 1992). These data support a lognormal

distribution of total tap water consumption having a geometric mean of 0.957 L/d and a

geometric standard deviation of 1.77. In addition, not all tap water consumption comes from

one’s own tap. A significant numbers of meals can be eaten outside one’s home, for example. 

The data on the fraction of tap water from one’s own tap are poor and are best represented by a

uniform distribution having a minimum of a 0.5 and a maximum of 1.0. A Monte Carlo

calculation of the product of the two parameters yields the value of 0.71 L/d used in this analysis

for tap water consumption.

Kennedy and Strenge (1992) made the assumption that the amount of water needed for domestic

purposes was for one person. Because the areas of the landfills in this analysis are so large, it is

likely that more than one person would be living on the land over a closed landfill. Therefore,

for this analysis, the geometric mean for the amount of water used for domestic purposes, Vdd and

Vdr, is based on 10 people, 9.1E+5 L. The amount of water from the aquifer needed for irrigation

is determined based on the average irrigation rate of 2.08 L/m2-d, the area of land under

cultivation, 2500 m2, and 365 d/y (Kennedy and Strenge 1992). Therefore a value of 1.9E+6 L

was used as the basis for a distribution for Virr (volume of water used for irrigation purposes

annually). A beta distribution was used for Virr to be consistent with the distribution assumption

for this parameter in Volume 3 of NUREG/CR-5512 (Beyeler et al. 1996).

Slag Pile at the Refinery

The size of the slag pile in the slag storage scenario affects the modeled concentration of

radionuclides in the aquifer, and thus the drinking water dose. The size of the slag pile used is

20,000 t (22,050 tons), corresponding to a slag pile comprised of the annual amount produced at

a typical steel refinery. This value is consistent with EPA (1997), and was judged to be a

reasonable slag pile size to use for this scenario. This value seems reasonable because slag is

typically stored to “cure” for 6 months or longer, and also because slag producers often keep

large stockpiles to be able to participate in bids for projects seeking to purchase large amounts of

slag (Kalyoncu 1996). The slag pile is modeled as a half-cylinder with a radius of 4 m (13 ft) and

a length of 400 m (1,312 ft), resulting in a large rectangular base with the dimensions of 8 m

(26 ft) wide by 400 m (1,312 ft) in length, and an area of 3.20E+3 m2

. The thickness of box 1 is

assumed to be the height of the slag pile, 4.0 m. This results in a total volume of 1.0E+4 m3

 of
Section 4 Recycle and Disposal of Steel

4-109 NUREG-1640

slag being stored, and assuming the density of slag in a pile is 2.0E+6 g/m3, the most likely value

for the total mass of slag present is 2.0+10 g (20,000 t [22,050 tons]). A value for the geometric

mean for the thickness of box 2 in the drinking water model, from the bottom of the slag pile to

the top of the aquifer, was obtained as the sum of the thicknesses of box 1 and box 2 in

NUREG/CR-5512, 1.1 m (3.77 ft) (Kennedy and Strenge 1992). This is reasonable because,

similar to the modeling done in NUREG/CR-5512, this scenario is intended to be generic for

sites across the United States. 

As described in the preceding paragraph, the size of the slag pile is based on a 1-year production

of slag. Therefore, a 1-year delay period following clearance was incorporated into the modeling,

and the drinking water dose over the 1-year period from 1 to 2 years following clearance was

calculated for this scenario. As described earlier in Section 4, the TDS of the aquifer in the slag

storage scenario was calculated over a long period of time. It was verified that based on these

models, the aquifer remained potable during this period. 

,QJHVWLRQ([SRVXUH3DUDPHWHUV

This section presents a description of uncertain values for those radionuclide-independent

parameters used in the calculation of ingestion exposure. Values for most environmental and

biotic transport of radionuclides and subsequent human consumption parameters were fixed and

were taken from Volume 1 of NUREG/CR-5512 (Kennedy and Strenge 1992). These values

were reviewed and were deemed appropriate and reasonable for the scenarios presented in this

report. 

Uncertainty in the food ingestion pathway was incorporated via the parameter for the fraction of

an individual’s annual diet derived from a home-grown garden. Two types of ingestion exposure

pathways are calculated; irrigation and non-irrigation. Although a dose is calculated separately

for each of these models, the same distribution of input values for the fraction of annual diet

(DIET) from each of the types of food (irrigated and non-irrigated) was used. The most likely

setting for the scenarios in this analysis were judged to be that of an urban or suburban garden

supplying a relatively small fraction of dietary fresh vegetables on a seasonal basis. The

triangular distribution used in this analysis for DIET (0–0.25, mode of 0.08) corresponds to the

generic assessment scenario for an urban gardener in EPA’s CAP-88 code (EPA 1991).

The soil ingestion pathway also includes uncertainty, incorporated in the modeling via the

parameter for consumption rate of soil, Usoil. The range used is based on an extensive recent

review of human soil ingestion (Simon 1998). The lognormal distribution used in this analysis is

adopted from Simon (1998), for “suburban lifestyles (with homes)—including lawns, parks,

recreational areas, some gardens.”

The atmospheric release scenario requires the use of the thickness of box 1 (surface layer) for the

ingestion exposure pathway. This parameter is used to calculate the radioactivity concentration

in the soil from deposition, assuming complete mixing throughout box 1. The fixed value used

for this parameter for the atmospheric scenario is the assumed depth of a plow layer, 0.15 m.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-110

The transport of C-14 from atmospheric release to uptake into plant depends on a fractional

equilibrium ration, pc-14. According to Regulatory Guide 1.109, this ratio is set equal to 1.0 for a

continuous release. Therefore, a value of 1.0 is used for pc-14. The transport of H-3 from

atmospheric release to uptake into plants depends on the absolute humidity of the atmosphere at

the receptor, H. Till and Meyer (1983) states that atmospheric humidity varies greatly from one

location to another in the United States. A graph in Till and Meyer (1983) shows that the

absolute humidity ranges from an average of 4.9 g/m3 in the west (e.g., Idaho, Utah) to an

average of 13.8 g/m3 in the southeast (e.g., Florida). A most likely value (mode) of 7 g/m3 for the

absolute humidity was calculated by incorporating the approximate percentage of the continental

U.S. that had a particular average humidity, as shown in Till and Meyer (1983, Figure 9.1). The

following assumptions were used to calculate a weighted average absolute humidity, H, of

7 g/m3

.

Percentage of U.S.

Average absolute

humidity (g/m3)

40% 4.9

20% 6.6

20% 8.4

15% 10.7

5% 13.8

Overall Weighted Average 7.3

An overall range of 3 g/m3 to 16 g/m3 was used based on the values in Till and Meyer (1983).

$WPRVSKHULF5HOHDVH3DUDPHWHUV

The total mass of dust that is calculated to escape a refinery baghouse in a year, Mra is calculated

using the material flow model. The duration of release of refinery atmospheric effluent, is 1 year,

in order to calculate an annual average release rate. 

The uncertainty in the atmospheric dispersion calculations was incorporated via the parameter

Chi/Q, the annual average dispersion factor. Historical data and statistical summaries for

approximately 300 weather stations in the U.S. were obtained (Doty and Wallace 1976), and used

to conduct a Monte Carlo analysis on the Gaussian plume dispersion equation. The median of

the resulting output (3.76 E-06 s/m3

) was obtained and used as the geometric mean of a

lognormal distribution, and an input distribution was fitted to the high end of the Monte Carlo

distribution using a geometric standard deviation of 2.59.

The fraction of time during a year that each stability class occurs is taken from Doty and Wallace

(1976). The average windspeed for stability classes A-F is calculated from data in Till and

Meyer (1983, Table 2.1). In calculating average windspeeds, the lowest and highest windspeed
Section 4 Recycle and Disposal of Steel

4-111 NUREG-1640

categories were not used (< 2 m/s and > 6 m/s), and the resulting average windspeeds are

representative of typical windspeeds. A value of 1.0 is used for the average windspeed for

stability class G. 

The effective height of the refinery stack, He is assumed to be 40 m (131 ft) above the ground. 

This value is reasonable for refineries, based on the physical height of typical baghouses, the

effluent velocity, and the temperature of the effluent. Because the distance from the refinery to

the nearest receptor, x, is generic, and a typical resident is assumed (suburban garden) a fixed

distance of 1,000 m (3,280 ft) is assumed.

The atmospheric scenario also uses a total deposition velocity, Vd(T) for calculating external

exposure from ground deposition (Equation 4.25) and internal dose from foliar deposition on

plants (Equation 4.27). The value for this parameter is dependent on the type of element, so the

radionuclides are grouped into three general groups: iodines, gases, and particulates (all others). 

The distributions used were developed using data and information in standard references (e.g.,

Miller 1984; Till and Meyer 1983) for deposition velocity and interception fractions.

/DQGILOO3DUDPHWHUV

For the scenarios involving a resident on a landfill after closure, the total mass of contaminated

material in the landfill, QT, is needed. This parameter is used to calculate the radioactivity

concentration in the soil, assuming complete mixing. This mass includes the daily and final

cover soil, and/or waste, depending on the type of waste. The total mass of material in a landfill

was calculated using the following information for sanitary and hazardous waste landfills:

6DQLWDU\/DQGILOO$VVXPSWLRQV

C The depth of an average sanitary landfill unit is about 4 m (13 ft), using the average

capacity (waste and daily cover soil) of 1.4E+6 m3 and an average area of 3.4E+5 m2

(Dehmel et al. 1994). 

C The ratio of waste to daily cover soil is 4:1 (Dehmel et al. 1994), which results in an

average of 80% (1.1E+6 m3

) of the capacity of the landfill consisting of waste, Vw, and

the remaining 20% (2.8E+5 m3

) consisting of daily cover soil.

C EPA recommends that the final closure cover on a sanitary landfill consist of at least

0.46 m (1.5 ft) of soil for an infiltration layer and 0.15 m (0.5 ft) for an erosion layer,

resulting in a total cover of 0.61 m (2 ft) (EPA 1993b). Therefore, the total volume of

final cover soil on a sanitary landfill is 2.1E+5 m3

.

C The bulk densities of the wastes (as disposed) are as follows: BOF baghouse dust

1.6E+6 g/m3

, refinery slag 2.0E+6 g/m3, and metal 3.93E+6 g/m3.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-112

C The radioactivity in the waste types that are similar to soil (i.e., BOF baghouse dust and

refinery slag) are dispersed throughout the total mass (waste, daily cover soil, and final

cover soil). However, for wastes that are similar to metals the radioactivity is dispersed

only throughout the daily cover soil and final cover soil. 

C For BOF baghouse dust disposal scenarios, the total volume of material in a sanitary

landfill after closure is 1.6E+6 m3 (waste = 1.1E+6 m3, daily and final cover soil =

4.9E+5 m3). Assuming a value of 1.60E+6 g/m3 for the density of soil as well as for

disposed BOF baghouse dust (EPA 1993a) a value of 2.54E+12 g is calculated for QT. 

C For slag disposal scenarios, the total volume of waste in a sanitary landfill is 1.1E+6 m3

while the total volume of soil in the landfill (daily and final cover soil) is 4.8E+5 m3. 

Assuming a density of 1.60E+6g/m3

 for soil and 2.0E+6g/m3 for slag, a value of

2.97E+12 g is used for QT. 

C For scenarios involving the disposal of metal wastes, only the volume of soil (daily and

final cover) is needed to calculate QT. Assuming 1.60E+6 g/m3

 for the density of soil, a

value of 7.8E+11 g is calculated for QT. 

C In order to account for the small fraction of a landfill that would likely consist of material

derived from cleared scrap, a sanitary landfill dilution factor was calculated and discussed

above (see Section 4.8.4.4). For estimates of the percent of a landfill that would be

comprised of material derived from licensee scrap, the following dilution factors were

applied to each waste category: Scrap metal (0.7%), slag (0.2%), baghouse dust (0.02%),

and refined metal products (0.6%).

Hazardous Landfill Assumptions

C Based on landfill survey information in Dehmel et al. (1994), the depth, area, and

capacity of an average hazardous landfill unit are 8.6 m (28 ft), 7.28E+4 m2

, and

6.58E+5 m3, respectively.

C Based on information in EPRI (1993), a maximum of approximately 25% of the capacity

of a hazardous landfill would consist of contaminated EAF dust. This results in 1.65E+5

m3

 of EAF dust and 4.94E+5 m3 of daily cover soil and other waste.

C For hazardous landfills EPA recommends that a minimum depth of 1.5 m (5 ft) of cover

material be in place upon closure (EPA 1989b). Therefore, the total volume of final

cover soil on a hazardous landfill is 1.09E+5 m3.

C The radioactivity in disposed EAF dust is assumed to be dispersed throughout the total

volume of material in the landfill (waste and soil).
Section 4 Recycle and Disposal of Steel

4-113 NUREG-1640

C The total volume of material in a hazardous landfill after closure (waste, daily cover soil,

and final cover soil) is 7.68E+5 m3

. Assuming a density of 1.60E+6 g/m3 (EPA 1993a)

for the soil (daily and final cover), and a density of 1.36E+6 g/m3 for the EAF dust, total

mass of material in a hazardous landfill, QT, is 1.19E+12 g. 

The thickness of box 1 (surface layer) in the landfill model, H1, is the sum of the depths of the

landfill and the final cover soil. Using a depth for an average sanitary landfill of 3.66 m (12 ft)

(Dehmel et al. 1994) and a final closure cover depth of 24 inches (0.61 m), the thickness of box 1

for a sanitary landfill is 4.27 m (4 ft). According to Dehmel et al. the depth of an average

hazardous landfill is 8.6 m (28 ft) (Dehmel et al. 1994). For hazardous landfills EPA

recommends that a minimum depth of 1.5 m (4.9 ft) of cover material upon closure

(EPA 1989b). Therefore, the total thickness for hazardous landfills is 10.1 m (33 ft). 

As seen in the mathematical modeling for the resident on closed landfills, the leach rate

parameter L12 is not used for metal waste (e.g., scrap metal or refined metal product). Therefore,

the thickness of box 1 is not needed for these scenarios. The leach rate constant for the

movement of radionuclides from disposed metal to the surrounding soil is dependent on the

corrosion of the metal. The leach rate constant used for the movement of radionuclides from the

metal waste to the soil, Lws, is 4.17E-4/y (1.14E-6/d) (Maheras et al. 1994).

The thickness of box 2 (unsaturated zone), H2, is the distance from the bottom edge of the landfill

to the top of the water table (aquifer). A mean value of 27 m (87 ft) was used for sanitary

landfills and 14.9 m (49 ft) for hazardous landfills for this distance (Dehmel et al. 1994).

The radionuclides in the waste placed in sanitary landfills are assumed to begin leaching

immediately upon placement in the landfill. The time between beginning of leaching and the

time radioactivity concentrations in groundwater are determined is treated as a probabilistic

parameter. The distribution of times is based on what is realistic for the exposed group and the

exposure situation addressed by each scenario. 

For the sanitary landfill resident scenarios, leaching is assumed to begin immediately upon

disposal of the cleared material, i.e., at the “beginning” of the scenario. Groundwater activity is

determined between 50 y and 150 y after leaching begins (18,263–54,788 d). These times are

based on professional judgement. The objective was to use a reasonable time frame, without

being overly conservative. It was judged unreasonable to assume immediate residence on an

abandoned sanitary landfill, yet it is also unreasonable to assume time frames far into the future.

For the sanitary landfill resident scenarios, the use of a uniform distribution for the time between

beginning of leaching and the time radioactivity concentrations in groundwater are determined

(between 50 y and 150 y after leaching begins) means that the 100-year range of time that is used

to calculate groundwater radioactivity concentration corresponds to the 100 years immediately

following the end of the post-closure monitoring period. This is because of the remaining 20

years of landfill operational, (one half of the 40-year total), followed by a 30-year monitoring

period.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-114

For the hazardous landfill resident scenario (for EAF dust), leaching is assumed to begin at the

end of the post-closure monitoring period, approximately 45 years after clearance (following 15

years of landfill operation and 30 years of post-closure monitoring). The time frame for

groundwater activity determination, between 50 y and 100 y after leaching begins

(18,263–36,525 days), corresponds to the time period between 95 y and 145 y after clearance. 

6WHHO6XUIDFHWR0DVV5DWLR

The surface-to-mass ratios for various steel objects were evaluated to develop an appropriate

range to use for this study. For this analysis, steel objects are assumed to have a density of 7.8

g/cm3

. Using this density, theoretical values for the surface-to-mass ratios for various objects

vary over a wide range from approximately 0.01 cm2

/g for large spheres (30-cm radius) and bar

stock (10-cm radius), up to approximately 2.0 cm2

/g for small bar stock, pipes, and sheets. 

Data are not available provide an adequate basis for choosing a “best estimate” from this range of

values. Using professional judgement and these theoretical data, the value of the surface-to-mass

ratio for recycled steel scrap is best described by a loguniform distribution having a minimum of

0.1 cm2

/g and a maximum of 2.0 cm2/g. The minimum value is characteristic of bar stock having

a radius of 1.0 cm. The maximum value is characteristic of pipes and sheets having a thickness

of 0.05 cm. These values are representative of bar stock, pipes, and sheets of various sizes with

residual radioactivity on one side only. A wide variety of steel objects commonly found at

nuclear facilities have surface-to-mass values that fall within this range. 

This range can be compared to other estimates for studies similar to this one. The EPA

Technical Support Document (EPA 1997) contains an estimated average surface-to-mass ratio of

0.3 cm2/g for all potentially cleared steel from NRC licensed facilities and the DOE complex. 

O’Donnell et al. (1978) suggested a value of 0.14 cm2/g as representative of typical heavy sheet

steel, and O’Donnell’s calculations are based on a reference steel object with a surface-to-mass

ratio of 0.45cm2/g. 

'RVH)DFWRUVIRU5HF\FOHRI6WHHO6FUDS

This analysis of recycle of cleared steel scrap includes 27 separate scenarios evaluated for 85

radionuclides. Of these, 9 scenarios have the highest dose factor for at least one radionuclide. 

Table 4.10 lists the mass-based critical-group dose factors for each radionuclide. Table 4.11 lists

the corresponding derived surficial critical-group dose factor for each radionuclide. Results for

all 27 scenarios are tabulated in Appendix A. 

The mean values of the critical-group dose factors for each radionuclide are listed in Table 4.10. 

These represent the dose to the average member of the critical group exposed to radioactivity

distributed throughout the mass of cleared steel (Bq/g or pCi/g). The circumstances of that

exposure are described by the scenario indicated in the right hand column. The 5th, 50th, and 95th

percentiles listed for each radionuclide represent the underlying distribution of dose factors

calculated for each critical group. The range of values from the 5th to the 95th percentile is the
Section 4 Recycle and Disposal of Steel

4-115 NUREG-1640

90% confidence interval on the dose factor. That is, there is a 90% certainty that the dose factor

for the average member of the critical group lies within this interval. The confidence interval is a

subjective measure of uncertainty in the dose factor that includes estimates of the variability and

uncertainty in the parameters used in each scenario.

The ratio of the 95th to the 5th percentile is a useful measure of the relative width of the 90%

confidence interval for comparison between scenarios. Smaller values of the 95/5 ratio indicate

less uncertainty than larger values. The scenarios with the smallest uncertainty are those with the

fewest number of exposure pathways and the least uncertainty in the parameters describing those

pathways. Of the nine critical group scenarios listed in Table 4.10, the scrap transportation

scenario has the smallest uncertainty with a 95/5 ratio of about 2 for most radionuclides. This

scenario involves only the external dose pathway. It includes uncertainty only in the time of

exposure for the truck driver, the external dose rate factor for the cargo of scrap, and the timing

of the scenario. The uncertainty in the timing of the scenario is unimportant for most

radionuclides. For a few radionuclides with very short half-lives uncertainty in the timing of the

scenario contributes some what to the width of the confidence interval. For example, Re-186

with a 3.8 day half-life has a 95/5 ratio of about 3.

For all scenarios that take place subsequent to the initial transport of scrap, additional sources of

uncertainty are introduced and wider confidence intervals result. Scenarios that address handling

of scrap include uncertainty due to dilution with other scrap. They also include additional

exposure pathways—inhalation of resuspended dust and inadvertent ingestion under dusty

conditions. Scenarios that address handling and processing of refinery products such as

baghouse dust and refinery slag include additional uncertainty in how much of each radionuclide

is partitioned to these materials. This group of handling and processing scenarios have 95/5

ratios that range from about 10 to about 50. The relative contribution to this uncertainty from

scenario timing, radioactivity partitioning, and internal dose pathways is nuclide-dependent. The

uncertainty in these dose factors results from a complicated interaction of half-life, radioactive

decay properties, and chemical behavior as well as uncertainties in describing the circumstances

under which individuals are exposed.

Greater uncertainty is associated with scenarios that involve multiple exposure pathways and

complex submodels. The atmospheric release scenarios, for example, include an atmospheric

dispersion model and pathways for ingestion, inhalation, and external exposure. Dose factors for

nuclides limited by the atmospheric release scenario have 95/5 ratios that range from about 60 to

slightly over 200. Most of this uncertainty is due to the atmospheric dispersion model but

additional contributions from partitioning to refinery off-gas and uncertainties in ingestion dose

are nuclide-dependent.

Dose factors for the five radionuclides limited by the drinking water pathway in the slag storage

scenario have the widest confidence intervals of all those analyzed in this report. The 95/5 ratios

for dose factors limited by the slag storage scenarios range from about 350 for Tc-99 to about

1,500 for Np-237. This is due to the uncertainties associated with the groundwater transport

model and the timing of the scenario. Over the period of time addressed by this scenario there is
Recycle and Disposal of Steel Section 4

NUREG-1640 4-116

Scrap Transport

Scrap Handling

EAF Dust Transport

Slag Handling

Slag Storage

EAF Dust Processing

Refined Metal Manufacturing

Refinery Atmospheric Release

Small Metal Object Close to Body

39

14

7 7

4 4 4 1 5

0

5

10

15

20

25

30

35

40

Number of Radionuclides

Steel Critical Group Scenarios

Figure 4.7 Scenarios describing critical groups for steel recycle

a large uncertainty in the rate at which each radionuclide leaches to the drinking water supply and

in the resulting radioactivity concentration in drinking water. 

Figure 4.7 indicates how many radionuclides have critical groups described by each of these

scenarios. Most limiting scenarios for steel recycle describe critical groups consisting of workers

at scrap yards and steel refineries who transport, handle, and process scrap metal or refinery

products such as slag and baghouse dust. Two critical group scenarios involving exposure to

cleared scrap account for 53 of the 85 radionuclides—scrap transportation for 39 and scrap

handling for 14 radionuclides. Eleven radionuclides have critical group scenarios involving

exposure to EAF baghouse dust—dust transportation for 7 and dust processing for 4

radionuclides. Seven radionuclides are limited by the slag handling scenario. Four are limited by

exposure to finished metal from a BOF refinery during manufacturing.
Section 4 Recycle and Disposal of Steel

4-117 NUREG-1640

There are three reasons why the scrap transportation scenario is important for the largest number

of radionuclides. First, there is minimal delay between clearance of scrap and transporting it to

the scrap yard so no significant radioactive decay occurs before the scenario begins. 

Consequently, this scenario describes critical groups for many short-lived radionuclides that

decay before later scenarios can occur. Second, unprocessed scrap has not yet been subjected to

dilution with other materials or chemical partitioning during refining. This means that the initial

radioactivity concentration is unchanged. Third, relatively large masses of scrap material are

transported in each load so relatively larger amounts of radioactivity are present in this scenario

than in most others. Because the scrap transportation scenario involves only the external dose

pathway, the radionuclides limited by this scenario are all gamma emitters.

Radionuclides associated with slag, dust, and off-gas scenarios are those which concentrate in

these materials during the refining process. All of these scenarios include internal dose

pathways; inhalation of dust, inadvertent ingestion, consumption of drinking water or ingestion

of garden produce. The radionuclides for which these material-specific scenarios are important

all have relatively long half-lives and are alpha- or beta emitters that contribute to internal dose

pathways. 

Two types of radionuclides have critical groups consisting of members of the general public

living in the vicinity of steel refineries. Critical groups for four volatile radionuclides with no

external dose component are described by the atmospheric release scenario. Critical group for

five-water soluble radionuclides with no external dose component result from the ground water

pathway of the slag storage scenario.

Residual radioactivity in consumer products rarely yields critical groups. Only one radionuclide

(Mo-93) is limited by exposure of an individual in the general public to a manufactured product. 

There are four reasons for this. First, the passage of time between clearance and the use of

consumer products allows many radionuclides to decay to very small concentrations. Second, the

amount of steel available from NRC licensed facilities is small compared to the total amount of

steel that is recycled each year. It is not large even when compared to the capacity of some steel

refineries. Mixing cleared steel with normal steel, even on a single charge basis, reduces

concentrations of radioactivity in finished steel. Third, many radionuclides do not appear in

finished steel. They are partitioned to slag or baghouse dust during refining. Finally, the

relatively small size of consumer products compared to the amounts of steel encountered by

refinery workers limits the amount of radioactivity to which any individual could be exposed. In

contrast, workers at scrap yards and steel refineries can be exposed to relatively large amounts of

cleared steel before mixing, processing, or radioactive decay can take place.

The mean values of the derived surficial dose factors for each radionuclide in Table 4.11

represent the dose to the average member of the critical group exposed to residual radioactivity

initially distributed over the surface of cleared iron and steel (Bq/cm2

 or pCi/cm2). Derived

surficial dose factors are calculated from mass-based dose factors by use of a surface-to-mass

ratio, appropriate for typical steel objects available for clearance. The value of The surface-tomass ratio is used to derive surficial dose factors as described in Section 4.7.
Recycle and Disposal of Steel Section 4

NUREG-1640 4-118

The calculation of derived surficial dose factors is probabilistic. The parameter SM is

represented by a distribution of values that incorporate the variability and uncertainty in the

surface-to-mass ratio of steel objects available for clearance. This additional source of

uncertainty results in wider confidence intervals for the surficial dose factors than for the massbased dose factors from which they are derived. The relative importance of this additional

uncertainty depends on the scenario. For scenarios with the narrowest confidence intervals, the

added uncertainty can contribute as much as an additional 100% to the width of the confidence

interval. The mass-based dose factor for the scrap transportation scenario has a 95/5 ratio of

about 2 for most radionuclides. The corresponding derived surficial dose factors have a 95/5

ratio of about 4. The added uncertainty in surface-to-mass ratio has a relatively smaller effect on

the confidence interval for scenarios with larger uncertainties, contributing an additional 10% to

50% to the 95/5 ratio. 

Table 4.10 Steel recycle critical-group dose factors—mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

H-3 6.4E-04 3.8E-05 2.8E-04 2.4E-03 2.4E-06 1.4E-07 1.0E-06 8.8E-06FE-ATMO-REFINER-N

C-14 2.8E-03 1.7E-04 2.1E-03 7.8E-03 1.0E-05 6.3E-07 7.8E-06 2.9E-05FE-BOFM-HANDMAN-W

Na-22 4.1E+02 7.3E+01 2.9E+02 1.1E+03 1.5E+00 2.7E-01 1.1E+00 3.9E+00FE-EAFD-TRANSPO-W

P-32 1.3E-01 8.1E-02 1.3E-01 1.8E-01 4.8E-04 3.0E-04 4.9E-04 6.7E-04FE-SCRP-TRANSPO-W

S-35 7.6E-03 7.1E-04 4.4E-03 2.5E-02 2.8E-05 2.6E-06 1.6E-05 9.2E-05FE-EAFD-PROCESS-W

Cl-36 2.7E+00 5.1E-02 9.3E-01 1.1E+01 1.0E-02 1.9E-04 3.4E-03 4.0E-02FE-ATMO-REFINER-N

K-40 5.2E+01 9.2E+00 3.8E+01 1.4E+02 1.9E-01 3.4E-02 1.4E-01 5.1E-01FE-EAFD-TRANSPO-W

Ca-41 1.3E-01 7.4E-04 2.7E-02 5.7E-01 4.9E-04 2.7E-06 1.0E-04 2.1E-03FE-SLAG-STORAGE-N

Ca-45 8.2E-02 3.7E-04 1.2E-02 3.4E-01 3.0E-04 1.4E-06 4.3E-05 1.2E-03FE-SLAG-STORAGE-N

Cr-51 2.5E+00 1.5E+00 2.5E+00 3.4E+00 9.1E-03 5.6E-03 9.2E-03 1.3E-02FE-SCRP-TRANSPO-W

Mn-54 8.5E+01 5.3E+01 8.6E+01 1.2E+02 3.2E-01 2.0E-01 3.2E-01 4.3E-01FE-SCRP-TRANSPO-W

Fe-55 1.0E-03 5.6E-05 8.4E-04 2.6E-03 3.8E-06 2.1E-07 3.1E-06 9.5E-06FE-BOFM-HANDMAN-W

Co-57 3.8E+00 2.4E+00 3.8E+00 5.2E+00 1.4E-02 8.7E-03 1.4E-02 1.9E-02FE-SCRP-TRANSPO-W

Co-58 9.5E+01 5.8E+01 9.6E+01 1.3E+02 3.5E-01 2.2E-01 3.5E-01 4.8E-01FE-SCRP-TRANSPO-W

Fe-59 1.1E+02 7.0E+01 1.2E+02 1.6E+02 4.2E-01 2.6E-01 4.3E-01 5.8E-01FE-SCRP-TRANSPO-W

Ni-59 4.5E-04 3.2E-05 4.0E-04 1.1E-03 1.6E-06 1.2E-07 1.5E-06 4.0E-06FE-BOFM-HANDMAN-W

Co-60 2.5E+02 1.6E+02 2.6E+02 3.5E+02 9.4E-01 5.9E-01 9.5E-01 1.3E+00FE-SCRP-TRANSPO-W

Ni-63 1.2E-03 7.3E-05 1.1E-03 2.8E-03 4.5E-06 2.7E-07 4.0E-06 1.1E-05FE-BOFM-HANDMAN-W

Zn-65 2.1E+02 4.0E+01 1.5E+02 5.8E+02 7.9E-01 1.5E-01 5.4E-01 2.1E+00FE-EAFD-TRANSPO-W

Cu-67 2.1E+00 1.0E+00 1.9E+00 3.6E+00 7.7E-03 3.8E-03 7.1E-03 1.3E-02FE-SCRP-TRANSPO-W

Se-75 3.6E+01 1.5E+00 2.2E+01 1.2E+02 1.3E-01 5.6E-03 8.1E-02 4.3E-01FE-EAFD-TRANSPO-W

Sr-85 4.7E+01 2.9E+01 4.7E+01 6.4E+01 1.7E-01 1.1E-01 1.7E-01 2.4E-01FE-SCRP-TRANSPO-W

Sr-89 1.2E-01 7.1E-02 1.2E-01 1.6E-01 4.3E-04 2.6E-04 4.3E-04 5.9E-04FE-SCRP-TRANSPO-W
Section 4 Recycle and Disposal of Steel

Table 4.10 Steel recycle critical-group dose factors—mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

4-119 NUREG-1640

Sr-90 1.0E+01 3.9E-02 1.0E+00 3.4E+01 3.8E-02 1.4E-04 3.8E-03 1.3E-01FE-SLAG-STORAGE-N

Y-91 3.5E-01 2.1E-01 3.5E-01 4.7E-01 1.3E-03 7.9E-04 1.3E-03 1.7E-03FE-SCRP-TRANSPO-W

Mo-93 1.4E-02 2.5E-03 1.1E-02 3.7E-02 5.2E-05 9.2E-06 4.2E-05 1.4E-04FE-METL-SMOBJCT-N

Nb-93m 8.4E-03 1.2E-03 5.6E-03 2.6E-02 3.1E-05 4.4E-06 2.1E-05 9.6E-05FE-SLAG-HANDLIN-W

Nb-94 1.6E+02 1.0E+02 1.6E+02 2.3E+02 6.1E-01 3.8E-01 6.1E-01 8.3E-01FE-SCRP-TRANSPO-W

Nb-95 7.2E+01 4.5E+01 7.3E+01 9.9E+01 2.7E-01 1.6E-01 2.7E-01 3.7E-01FE-SCRP-TRANSPO-W

Zr-95 7.2E+01 4.4E+01 7.2E+01 9.8E+01 2.7E-01 1.6E-01 2.7E-01 3.6E-01FE-SCRP-TRANSPO-W

Tc-99 1.9E-01 1.8E-03 4.4E-02 9.2E-01 7.0E-04 6.8E-06 1.6E-04 3.4E-03FE-SLAG-STORAGE-N

Ru-103 4.6E+01 2.9E+01 4.7E+01 6.4E+01 1.7E-01 1.1E-01 1.7E-01 2.4E-01FE-SCRP-TRANSPO-W

Ru-106 2.1E+01 1.3E+01 2.1E+01 2.8E+01 7.6E-02 4.7E-02 7.7E-02 1.0E-01FE-SCRP-TRANSPO-W

Ag-108m 1.6E+02 1.0E+02 1.6E+02 2.2E+02 6.0E-01 3.7E-01 6.0E-01 8.3E-01FE-SCRP-TRANSPO-W

Cd-109 4.4E-01 6.2E-02 3.0E-01 1.2E+00 1.6E-03 2.3E-04 1.1E-03 4.3E-03FE-EAFD-PROCESS-W

Ag-110m 2.8E+02 1.8E+02 2.8E+02 3.9E+02 1.0E+00 6.5E-01 1.1E+00 1.4E+00FE-SCRP-TRANSPO-W

Sb-124 1.8E+02 1.1E+02 1.8E+02 2.5E+02 6.7E-01 4.1E-01 6.7E-01 9.2E-01FE-SCRP-TRANSPO-W

I-125 2.7E+00 1.2E-01 1.3E+00 1.0E+01 1.0E-02 4.5E-04 4.8E-03 3.8E-02FE-ATMO-REFINER-N

Sb-125 4.1E+01 2.5E+01 4.1E+01 5.6E+01 1.5E-01 9.4E-02 1.5E-01 2.1E-01FE-SCRP-TRANSPO-W

I-129 6.1E+01 3.3E+00 2.7E+01 2.4E+02 2.3E-01 1.2E-02 9.9E-02 8.8E-01FE-ATMO-REFINER-N

I-131 2.5E+01 1.5E+01 2.5E+01 3.6E+01 9.3E-02 5.7E-02 9.3E-02 1.3E-01FE-SCRP-TRANSPO-W

Ba-133 2.8E+01 1.7E+01 2.8E+01 3.8E+01 1.0E-01 6.4E-02 1.0E-01 1.4E-01FE-SCRP-TRANSPO-W

Cs-134 6.6E+02 1.1E+02 4.7E+02 1.7E+03 2.4E+00 3.9E-01 1.8E+00 6.3E+00FE-EAFD-TRANSPO-W

Cs-137 2.6E+02 4.8E+01 1.8E+02 6.8E+02 9.5E-01 1.8E-01 6.7E-01 2.5E+00FE-EAFD-TRANSPO-W

Ce-141 2.7E+00 1.7E+00 2.7E+00 3.7E+00 1.0E-02 6.2E-03 1.0E-02 1.4E-02FE-SCRP-TRANSPO-W

Ce-144 3.3E+00 2.0E+00 3.3E+00 4.5E+00 1.2E-02 7.5E-03 1.2E-02 1.7E-02FE-SCRP-TRANSPO-W

Pm-147 1.1E-02 1.6E-03 7.4E-03 3.3E-02 4.2E-05 5.9E-06 2.7E-05 1.2E-04FE-SLAG-HANDLIN-W

Eu-152 1.1E+02 6.9E+01 1.1E+02 1.5E+02 4.1E-01 2.6E-01 4.1E-01 5.7E-01FE-SCRP-TRANSPO-W

Eu-154 1.2E+02 7.5E+01 1.2E+02 1.7E+02 4.5E-01 2.8E-01 4.5E-01 6.2E-01FE-SCRP-TRANSPO-W

Eu-155 1.1E+00 6.6E-01 1.1E+00 1.5E+00 3.9E-03 2.4E-03 3.9E-03 5.4E-03FE-SCRP-TRANSPO-W

Re-186 2.5E-01 1.4E-01 2.4E-01 3.9E-01 9.1E-04 5.1E-04 8.8E-04 1.4E-03FE-SCRP-TRANSPO-W

Ir-192 1.2E+02 6.3E+00 6.7E+01 4.0E+02 4.4E-01 2.3E-02 2.5E-01 1.5E+00FE-EAFD-TRANSPO-W

Pb-210 1.5E+02 2.4E+01 9.9E+01 4.3E+02 5.7E-01 8.9E-02 3.7E-01 1.6E+00FE-EAFD-PROCESS-W

Po-210 6.0E+01 8.1E+00 4.2E+01 1.6E+02 2.2E-01 3.0E-02 1.6E-01 6.0E-01FE-EAFD-PROCESS-W

Bi-210 3.3E-02 7.3E-03 2.8E-02 7.6E-02 1.2E-04 2.7E-05 1.0E-04 2.8E-04FE-SCRP-HANDLIN-W

Rn-222 8.6E+01 4.8E+01 8.2E+01 1.3E+02 3.2E-01 1.8E-01 3.0E-01 5.0E-01FE-SCRP-TRANSPO-W

Ra-223 1.8E+01 1.1E+01 1.8E+01 2.5E+01 6.7E-02 4.2E-02 6.7E-02 9.4E-02FE-SCRP-TRANSPO-W

Ra-224 6.1E+01 3.4E+01 5.9E+01 9.7E+01 2.3E-01 1.2E-01 2.2E-01 3.6E-01FE-SCRP-TRANSPO-W
Recycle and Disposal of Steel Section 4

Table 4.10 Steel recycle critical-group dose factors—mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

NUREG-1640 4-120

Ac-225 1.4E+01 8.8E+00 1.4E+01 2.0E+01 5.3E-02 3.2E-02 5.2E-02 7.4E-02FE-SCRP-TRANSPO-W

Ra-225 1.8E+00 4.0E-01 1.5E+00 4.1E+00 6.7E-03 1.5E-03 5.6E-03 1.5E-02FE-SCRP-HANDLIN-W

Ra-226 1.7E+02 1.1E+02 1.7E+02 2.4E+02 6.4E-01 4.0E-01 6.5E-01 8.9E-01FE-SCRP-TRANSPO-W

Ac-227 3.4E+02 4.1E+01 2.1E+02 1.1E+03 1.3E+00 1.5E-01 7.8E-01 3.9E+00FE-SLAG-HANDLIN-W

Th-227 5.9E+00 3.6E+00 5.9E+00 8.1E+00 2.2E-02 1.3E-02 2.2E-02 3.0E-02FE-SCRP-TRANSPO-W

Th-228 1.3E+02 7.9E+01 1.3E+02 1.7E+02 4.7E-01 2.9E-01 4.7E-01 6.5E-01FE-SCRP-TRANSPO-W

Ra-228 8.4E+01 5.2E+01 8.4E+01 1.2E+02 3.1E-01 1.9E-01 3.1E-01 4.3E-01FE-SCRP-TRANSPO-W

Th-229 4.3E+02 6.2E+01 3.6E+02 1.0E+03 1.6E+00 2.3E-01 1.3E+00 3.8E+00FE-SCRP-HANDLIN-W

Th-230 6.5E+01 9.3E+00 5.4E+01 1.6E+02 2.4E-01 3.4E-02 2.0E-01 5.8E-01FE-SCRP-HANDLIN-W

Pa-231 2.3E+02 3.0E+01 1.3E+02 6.7E+02 8.3E-01 1.1E-01 5.0E-01 2.5E+00FE-SLAG-HANDLIN-W

Th-231 1.5E-02 3.3E-03 1.1E-02 3.9E-02 5.5E-05 1.2E-05 3.9E-05 1.4E-04FE-SCRP-TRANSPO-W

Th-232 2.9E+02 4.1E+01 2.4E+02 6.9E+02 1.1E+00 1.5E-01 8.8E-01 2.6E+00FE-SCRP-HANDLIN-W

Pa-233 1.3E+01 8.1E+00 1.3E+01 1.8E+01 4.9E-02 3.0E-02 4.9E-02 6.8E-02FE-SCRP-TRANSPO-W

U-233 3.4E+01 4.6E+00 2.8E+01 8.1E+01 1.2E-01 1.7E-02 1.0E-01 3.0E-01FE-SCRP-HANDLIN-W

Th-234 7.3E-01 4.5E-01 7.4E-01 1.0E+00 2.7E-03 1.7E-03 2.7E-03 3.7E-03FE-SCRP-TRANSPO-W

U-234 3.3E+01 4.5E+00 2.7E+01 7.9E+01 1.2E-01 1.7E-02 1.0E-01 2.9E-01FE-SCRP-HANDLIN-W

U-235 3.2E+01 4.1E+00 2.2E+01 9.3E+01 1.2E-01 1.5E-02 8.2E-02 3.5E-01FE-SLAG-HANDLIN-W

Np-237 2.0E+03 8.4E+00 3.1E+02 7.3E+03 7.4E+00 3.1E-02 1.1E+00 2.7E+01FE-SLAG-STORAGE-N

Pu-238 7.1E+01 9.8E+00 5.9E+01 1.7E+02 2.6E-01 3.6E-02 2.2E-01 6.4E-01FE-SCRP-HANDLIN-W

U-238 2.9E+01 4.1E+00 2.4E+01 7.1E+01 1.1E-01 1.5E-02 9.0E-02 2.6E-01FE-SCRP-HANDLIN-W

Pu-239 7.6E+01 1.0E+01 6.3E+01 1.8E+02 2.8E-01 3.9E-02 2.3E-01 6.8E-01FE-SCRP-HANDLIN-W

Pu-240 7.6E+01 1.0E+01 6.3E+01 1.8E+02 2.8E-01 3.9E-02 2.3E-01 6.8E-01FE-SCRP-HANDLIN-W

Pu-241 1.2E+00 1.7E-01 1.0E+00 3.0E+00 4.5E-03 6.2E-04 3.8E-03 1.1E-02FE-SCRP-HANDLIN-W

Am-241 1.1E+02 1.3E+01 8.0E+01 3.4E+02 4.2E-01 4.9E-02 3.0E-01 1.3E+00FE-SLAG-HANDLIN-W

Cm-242 4.3E+00 6.7E-01 3.6E+00 1.0E+01 1.6E-02 2.5E-03 1.3E-02 3.8E-02FE-SCRP-HANDLIN-W

Pu-242 7.3E+01 9.9E+00 6.0E+01 1.8E+02 2.7E-01 3.7E-02 2.2E-01 6.5E-01FE-SCRP-HANDLIN-W

Cm-244 6.3E+01 7.4E+00 4.1E+01 1.9E+02 2.3E-01 2.7E-02 1.5E-01 7.1E-01FE-SLAG-HANDLIN-W
Section 4 Recycle and Disposal of Steel

4-121 NUREG-1640

Table 4.11 Steel recycle critical-group dose factors—surficial

(μSv/y per Bq/cm2) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

H-3 4.8E-04 2.2E-05 2.1E-04 1.7E-03 1.8E-06 8.1E-08 7.6E-07 6.3E-06 FE-ATMO-REFINER-N

C-14 2.1E-03 1.3E-04 1.4E-03 6.5E-03 7.8E-06 4.9E-07 5.2E-06 2.4E-05 FE-BOFM-HANDMAN-W

Na-22 3.2E+02 4.6E+01 1.9E+02 9.2E+02 1.2E+00 1.7E-01 7.2E-01 3.4E+00 FE-EAFD-TRANSPO-W

P-32 9.9E-02 4.2E-02 9.2E-02 1.8E-01 3.7E-04 1.6E-04 3.4E-04 6.6E-04 FE-SCRP-TRANSPO-W

S-35 5.6E-03 3.9E-04 3.1E-03 2.1E-02 2.1E-05 1.4E-06 1.2E-05 7.7E-05 FE-EAFD-PROCESS-W

Cl-36 2.1E+00 3.1E-02 6.6E-01 8.6E+00 7.7E-03 1.1E-04 2.4E-03 3.2E-02 FE-ATMO-REFINER-N

K-40 4.0E+01 5.7E+00 2.6E+01 1.2E+02 1.5E-01 2.1E-02 9.6E-02 4.5E-01 FE-EAFD-TRANSPO-W

Ca-41 9.8E-02 5.4E-04 1.9E-02 3.6E-01 3.6E-04 2.0E-06 7.1E-05 1.3E-03 FE-SLAG-STORAGE-N

Ca-45 6.1E-02 2.7E-04 8.1E-03 2.3E-01 2.2E-04 1.0E-06 3.0E-05 8.5E-04 FE-SLAG-STORAGE-N

Cr-51 1.9E+00 7.8E-01 1.7E+00 3.4E+00 6.9E-03 2.9E-03 6.4E-03 1.3E-02 FE-SCRP-TRANSPO-W

Mn-54 6.4E+01 2.7E+01 6.0E+01 1.2E+02 2.4E-01 1.0E-01 2.2E-01 4.3E-01 FE-SCRP-TRANSPO-W

Fe-55 7.6E-04 4.7E-05 5.6E-04 2.1E-03 2.8E-06 1.7E-07 2.1E-06 7.6E-06 FE-BOFM-HANDMAN-W

Co-57 2.9E+00 1.2E+00 2.7E+00 5.3E+00 1.1E-02 4.5E-03 9.9E-03 1.9E-02 FE-SCRP-TRANSPO-W

Co-58 7.2E+01 3.0E+01 6.6E+01 1.3E+02 2.7E-01 1.1E-01 2.5E-01 4.8E-01 FE-SCRP-TRANSPO-W

Fe-59 8.7E+01 3.6E+01 8.0E+01 1.6E+02 3.2E-01 1.3E-01 3.0E-01 5.8E-01 FE-SCRP-TRANSPO-W

Ni-59 3.4E-04 2.2E-05 2.7E-04 9.3E-04 1.2E-06 8.1E-08 9.8E-07 3.4E-06 FE-BOFM-HANDMAN-W

Co-60 1.9E+02 8.2E+01 1.8E+02 3.5E+02 7.1E-01 3.0E-01 6.6E-01 1.3E+00 FE-SCRP-TRANSPO-W

Ni-63 9.1E-04 5.2E-05 7.6E-04 2.5E-03 3.4E-06 1.9E-07 2.8E-06 9.1E-06 FE-BOFM-HANDMAN-W

Zn-65 1.6E+02 2.3E+01 1.0E+02 4.9E+02 6.0E-01 8.5E-02 3.8E-01 1.8E+00 FE-EAFD-TRANSPO-W

Cu-67 1.6E+00 5.6E-01 1.4E+00 3.1E+00 5.8E-03 2.1E-03 5.0E-03 1.2E-02 FE-SCRP-TRANSPO-W

Se-75 2.7E+01 1.0E+00 1.6E+01 9.3E+01 9.8E-02 3.8E-03 5.9E-02 3.4E-01 FE-EAFD-TRANSPO-W

Sr-85 3.6E+01 1.5E+01 3.3E+01 6.5E+01 1.3E-01 5.5E-02 1.2E-01 2.4E-01 FE-SCRP-TRANSPO-W

Sr-89 8.8E-02 3.7E-02 8.1E-02 1.6E-01 3.3E-04 1.4E-04 3.0E-04 5.9E-04 FE-SCRP-TRANSPO-W

Sr-90 7.5E+00 2.3E-02 7.3E-01 2.2E+01 2.8E-02 8.6E-05 2.7E-03 8.2E-02 FE-SLAG-STORAGE-N

Y-91 2.6E-01 1.1E-01 2.4E-01 4.7E-01 9.7E-04 4.1E-04 9.0E-04 1.8E-03 FE-SCRP-TRANSPO-W

Mo-93 1.1E-02 1.4E-03 7.9E-03 3.1E-02 3.9E-05 5.4E-06 2.9E-05 1.1E-04 FE-METL-SMOBJCT-N

Nb-93m 6.4E-03 8.0E-04 3.7E-03 2.1E-02 2.4E-05 3.0E-06 1.4E-05 7.6E-05 FE-SLAG-HANDLIN-W

Nb-94 1.2E+02 5.3E+01 1.1E+02 2.3E+02 4.6E-01 2.0E-01 4.2E-01 8.4E-01 FE-SCRP-TRANSPO-W

Nb-95 5.5E+01 2.3E+01 5.1E+01 9.9E+01 2.0E-01 8.5E-02 1.9E-01 3.7E-01 FE-SCRP-TRANSPO-W

Zr-95 5.4E+01 2.3E+01 5.0E+01 9.9E+01 2.0E-01 8.5E-02 1.9E-01 3.7E-01 FE-SCRP-TRANSPO-W

Tc-99 1.4E-01 1.3E-03 3.4E-02 6.7E-01 5.3E-04 4.9E-06 1.3E-04 2.5E-03 FE-SLAG-STORAGE-N

Ru-103 3.5E+01 1.5E+01 3.2E+01 6.4E+01 1.3E-01 5.4E-02 1.2E-01 2.4E-01 FE-SCRP-TRANSPO-W

Ru-106 1.6E+01 6.6E+00 1.4E+01 2.8E+01 5.8E-02 2.5E-02 5.4E-02 1.1E-01 FE-SCRP-TRANSPO-W

Ag-108m 1.2E+02 5.2E+01 1.1E+02 2.2E+02 4.5E-01 1.9E-01 4.2E-01 8.3E-01 FE-SCRP-TRANSPO-W

Cd-109 3.3E-01 3.9E-02 2.2E-01 1.0E+00 1.2E-03 1.5E-04 8.3E-04 3.7E-03 FE-EAFD-PROCESS-W
Recycle and Disposal of Steel Section 4

Table 4.11 Steel recycle critical-group dose factors—surficial

(μSv/y per Bq/cm2) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

NUREG-1640 4-122

Ag-110m 2.1E+02 9.1E+01 2.0E+02 3.9E+02 7.9E-01 3.4E-01 7.3E-01 1.4E+00 FE-SCRP-TRANSPO-W

Sb-124 1.4E+02 5.7E+01 1.3E+02 2.5E+02 5.1E-01 2.1E-01 4.7E-01 9.2E-01 FE-SCRP-TRANSPO-W

I-125 2.1E+00 8.1E-02 9.0E-01 8.0E+00 7.8E-03 3.0E-04 3.3E-03 3.0E-02 FE-ATMO-REFINER-N

Sb-125 3.1E+01 1.3E+01 2.9E+01 5.6E+01 1.1E-01 4.8E-02 1.1E-01 2.1E-01 FE-SCRP-TRANSPO-W

I-129 4.6E+01 2.1E+00 1.9E+01 1.8E+02 1.7E-01 7.9E-03 7.2E-02 6.7E-01 FE-ATMO-REFINER-N

I-131 1.9E+01 8.0E+00 1.7E+01 3.4E+01 7.0E-02 3.0E-02 6.4E-02 1.3E-01 FE-SCRP-TRANSPO-W

Ba-133 2.1E+01 9.0E+00 2.0E+01 3.9E+01 7.8E-02 3.3E-02 7.2E-02 1.4E-01 FE-SCRP-TRANSPO-W

Cs-134 4.9E+02 7.2E+01 3.3E+02 1.3E+03 1.8E+00 2.7E-01 1.2E+00 4.9E+00 FE-EAFD-TRANSPO-W

Cs-137 2.0E+02 2.8E+01 1.3E+02 5.9E+02 7.3E-01 1.0E-01 4.7E-01 2.2E+00 FE-EAFD-TRANSPO-W

Ce-141 2.1E+00 8.6E-01 1.9E+00 3.7E+00 7.6E-03 3.2E-03 7.1E-03 1.4E-02 FE-SCRP-TRANSPO-W

Ce-144 2.5E+00 1.1E+00 2.3E+00 4.5E+00 9.2E-03 3.9E-03 8.5E-03 1.7E-02 FE-SCRP-TRANSPO-W

Pm-147 8.4E-03 9.4E-04 5.2E-03 2.5E-02 3.1E-05 3.5E-06 1.9E-05 9.2E-05 FE-SLAG-HANDLIN-W

Eu-152 8.4E+01 3.6E+01 7.8E+01 1.5E+02 3.1E-01 1.3E-01 2.9E-01 5.7E-01 FE-SCRP-TRANSPO-W

Eu-154 9.2E+01 3.9E+01 8.5E+01 1.7E+02 3.4E-01 1.4E-01 3.2E-01 6.2E-01 FE-SCRP-TRANSPO-W

Eu-155 8.0E-01 3.4E-01 7.5E-01 1.5E+00 3.0E-03 1.3E-03 2.8E-03 5.4E-03 FE-SCRP-TRANSPO-W

Re-186 1.9E-01 7.5E-02 1.7E-01 3.5E-01 6.9E-04 2.8E-04 6.2E-04 1.3E-03 FE-SCRP-TRANSPO-W

Ir-192 8.9E+01 3.7E+00 4.9E+01 3.4E+02 3.3E-01 1.4E-02 1.8E-01 1.2E+00 FE-EAFD-TRANSPO-W

Pb-210 1.2E+02 1.4E+01 6.8E+01 3.5E+02 4.3E-01 5.3E-02 2.5E-01 1.3E+00 FE-EAFD-PROCESS-W

Po-210 4.4E+01 5.3E+00 3.0E+01 1.3E+02 1.6E-01 1.9E-02 1.1E-01 4.9E-01 FE-EAFD-PROCESS-W

Bi-210 2.5E-02 4.3E-03 1.9E-02 6.5E-02 9.3E-05 1.6E-05 7.1E-05 2.4E-04 FE-SCRP-HANDLIN-W

Rn-222 6.5E+01 2.6E+01 5.9E+01 1.2E+02 2.4E-01 9.6E-02 2.2E-01 4.5E-01 FE-SCRP-TRANSPO-W

Ra-223 1.4E+01 5.7E+00 1.3E+01 2.5E+01 5.1E-02 2.1E-02 4.7E-02 9.1E-02 FE-SCRP-TRANSPO-W

Ra-224 4.6E+01 1.8E+01 4.2E+01 8.8E+01 1.7E-01 6.8E-02 1.5E-01 3.2E-01 FE-SCRP-TRANSPO-W

Ac-225 1.1E+01 4.5E+00 9.9E+00 1.9E+01 4.0E-02 1.7E-02 3.7E-02 7.1E-02 FE-SCRP-TRANSPO-W

Ra-225 1.4E+00 2.3E-01 1.1E+00 3.6E+00 5.1E-03 8.7E-04 3.9E-03 1.3E-02 FE-SCRP-HANDLIN-W

Ra-226 1.3E+02 5.6E+01 1.2E+02 2.4E+02 4.9E-01 2.1E-01 4.5E-01 8.9E-01 FE-SCRP-TRANSPO-W

Ac-227 2.5E+02 2.5E+01 1.5E+02 7.7E+02 9.4E-01 9.3E-02 5.6E-01 2.8E+00 FE-SLAG-HANDLIN-W

Th-227 4.4E+00 1.9E+00 4.1E+00 8.1E+00 1.6E-02 6.9E-03 1.5E-02 3.0E-02 FE-SCRP-TRANSPO-W

Th-228 9.6E+01 4.1E+01 8.9E+01 1.8E+02 3.6E-01 1.5E-01 3.3E-01 6.5E-01 FE-SCRP-TRANSPO-W

Ra-228 6.3E+01 2.7E+01 5.9E+01 1.2E+02 2.3E-01 1.0E-01 2.2E-01 4.3E-01 FE-SCRP-TRANSPO-W

Th-229 3.3E+02 3.8E+01 2.4E+02 8.6E+02 1.2E+00 1.4E-01 9.0E-01 3.2E+00 FE-SCRP-HANDLIN-W

Th-230 4.9E+01 5.6E+00 3.7E+01 1.3E+02 1.8E-01 2.1E-02 1.4E-01 4.8E-01 FE-SCRP-HANDLIN-W

Pa-231 1.7E+02 2.0E+01 9.7E+01 5.3E+02 6.3E-01 7.3E-02 3.6E-01 1.9E+00 FE-SLAG-HANDLIN-W

Th-231 1.1E-02 1.9E-03 7.7E-03 3.2E-02 4.2E-05 7.0E-06 2.9E-05 1.2E-04 FE-SCRP-TRANSPO-W

Th-232 2.2E+02 2.5E+01 1.6E+02 5.8E+02 8.0E-01 9.2E-02 6.0E-01 2.1E+00 FE-SCRP-HANDLIN-W
Section 4 Recycle and Disposal of Steel

Table 4.11 Steel recycle critical-group dose factors—surficial

(μSv/y per Bq/cm2) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

4-123 NUREG-1640

Pa-233 1.0E+01 4.2E+00 9.3E+00 1.8E+01 3.7E-02 1.5E-02 3.4E-02 6.8E-02 FE-SCRP-TRANSPO-W

U-233 2.5E+01 2.8E+00 1.9E+01 6.8E+01 9.4E-02 1.0E-02 7.0E-02 2.5E-01 FE-SCRP-HANDLIN-W

Th-234 5.5E-01 2.3E-01 5.1E-01 1.0E+00 2.0E-03 8.5E-04 1.9E-03 3.7E-03 FE-SCRP-TRANSPO-W

U-234 2.5E+01 2.7E+00 1.9E+01 6.6E+01 9.2E-02 1.0E-02 6.9E-02 2.4E-01 FE-SCRP-HANDLIN-W

U-235 2.4E+01 2.6E+00 1.5E+01 7.5E+01 8.9E-02 9.5E-03 5.5E-02 2.8E-01 FE-SLAG-HANDLIN-W

Np-237 1.4E+03 6.1E+00 2.2E+02 6.0E+03 5.3E+00 2.2E-02 8.0E-01 2.2E+01 FE-SLAG-STORAGE-N

Pu-238 5.4E+01 6.0E+00 4.0E+01 1.4E+02 2.0E-01 2.2E-02 1.5E-01 5.3E-01 FE-SCRP-HANDLIN-W

U-238 2.2E+01 2.5E+00 1.7E+01 5.9E+01 8.2E-02 9.1E-03 6.2E-02 2.2E-01 FE-SCRP-HANDLIN-W

Pu-239 5.8E+01 6.4E+00 4.3E+01 1.5E+02 2.1E-01 2.4E-02 1.6E-01 5.7E-01 FE-SCRP-HANDLIN-W

Pu-240 5.8E+01 6.4E+00 4.3E+01 1.5E+02 2.1E-01 2.4E-02 1.6E-01 5.7E-01 FE-SCRP-HANDLIN-W

Pu-241 9.3E-01 1.0E-01 7.0E-01 2.5E+00 3.4E-03 3.8E-04 2.6E-03 9.1E-03 FE-SCRP-HANDLIN-W

Am-241 8.5E+01 1.1E+01 6.3E+01 2.2E+02 3.2E-01 4.0E-02 2.3E-01 8.3E-01 FE-SLAG-HANDLIN-W

Cm-242 3.2E+00 4.1E-01 2.4E+00 8.6E+00 1.2E-02 1.5E-03 8.9E-03 3.2E-02 FE-SCRP-HANDLIN-W

Pu-242 5.5E+01 6.1E+00 4.1E+01 1.5E+02 2.0E-01 2.2E-02 1.5E-01 5.4E-01 FE-SCRP-HANDLIN-W

Cm-244 4.8E+01 4.6E+00 2.9E+01 1.5E+02 1.8E-01 1.7E-02 1.1E-01 5.5E-01 FE-SLAG-HANDLIN-W
Section 5 Evaluation of Copper

5-1 NUREG-1640

Twenty-three potential exposure scenarios for cleared copper scrap that are realistically based on

current American industries are evaluated in this section. As in the steel evaluation, scenario

categories include handling and processing, storage, transportation, product use, and disposal. A

radionuclide-specific, probabilistic dose factor distribution was calculated for the members of all

exposed groups, and a dose factor for an average member of each critical group was calculated in the

same manner as for steel recycle. The mean dose factor for each critical group is reported in

normalized units of μSv/y per Bq/g scrap (mrem/y per pCi/g) and μSv/y per Bq/cm2 scrap (mrem/y per

pCi/cm2 ) for each radionuclide. Dose factors at the 5th , 50th , and 95th percentiles are also reported.

The copper recycle analyses yield similar critical groups as steel recycle. The most common critical

groups are commercial truck drivers carrying cleared copper scrap and workers at copper refineries. 

Scenarios involving transport of scrap material resulted in critical group designation for approximately

half (47) of the 85 radionuclides in the analysis. Other scenarios identifying critical groups for many

radionuclides involve handling refinery slag (31 radionuclides). Only one critical group involves the

use of steel consumer products: use of a generic small object close to the body made from refined

copper. 

Mean critical-group dose factors for the radionuclides range from a high of 3.3E+02 μSv/y per Bq/g

(1.2 mrem/y per pCi/g) for Th-229 to a low of 4.2E-04 μSv/y per Bq/g (1.6E-06 mrem/y per pCi/g) for

Ni-59. The surficial mean critical-group dose factors range from 2.9E+2 μSv/y per Bq/cm2 (Th-229)

down to 3.6E-4 μSv/y per Bq/cm2 (Ni-59). The Th-229 dose factors are not unusual for the set of

copper dose factors, as 16 other dose factors are within a factor of three of the Th-229 values. 

Seventy-three of the radionuclide-specific, copper critical-group dose factors are 135 μSv/y per Bq/g

or lower (0.5 mrem/y per pCi/g).

(9$/8$7,212)5(&<&/($1'',6326$/2)&233(5

6&5$3

This section describes the technical evaluation of the recycle and disposal of copper scrap that

could be cleared from Nuclear Regulatory Commission (NRC) licensed facilities. Similar to

steel scrap (Section 4), the flow of cleared material was probabilistically modeled, distributions

of radionuclide concentrations in refined and disposed materials were calculated, and the mean

dose factors for each potentially exposed group were estimated. 

,QWURGXFWLRQWR$QDO\VLV

The analysis process for calculating potential exposure from copper recycle and disposal is

essentially the same as described previously for iron and steel. A material flow model specific to

copper scrap was developed, radionuclide concentrations were calculated, and scenario

evaluations were conducted. Besides the material flow model (and calculated concentrations in

refined and disposed materials), there are only minor differences between the steel and copper

scrap analyses. There are several minor scenario parameter differences and one additional

exposure scenario that is specific to recycled copper scrap (described in Section 5.6). 
Evaluation of Copper Section 5

NUREG-1640 5-2

)ORZRI5HF\FOHGDQG'LVSRVHG&RSSHU6FUDS

The material flow model for copper represents the general processes that cleared material would

go through from the time it is cleared by a licensed facility to the time of final disposal. Similar

to steel, the copper material flow model is comprised of two types of models: conceptual and

mathematical. The conceptual model describes the copper refining process and defines the limits

of this analysis, while the mathematical model presents the mathematical equations that

implement the information presented in the conceptual model.

The material flow model is based on a literature review of the U.S. secondary copper industry. It

is intended to provide a defensible basis for developing appropriate exposure scenarios. In

addition, the output of the material flow model provides key input to the dose calculations for

each scenario. This input consists of radionuclide-specific concentrations in recycle byproducts,

in effluents, and in waste products of the refining process. Because of the number of scenarios

being analyzed and the differing times at which they occur, the mathematical model presented in

this section does not include radioactive decay. However, radioactive decay is taken into account

in the individual scenarios, in the same manner as in the steel recycle analysis.

This section presents the conceptual model that describes the movement of scrap through the

normal refining process, beginning with the production of scrap, through refining,

manufacturing, product use, and ending with disposal. Figure 5.1 presents a schematic diagram

of the overall material flow for copper scrap. The mass of material and the amount of

radioactivity are tracked separately so that the radioactivity concentration can be calculated at any

point in the flow. The steps or processes in the refining process are shown in Figure 5.1. Each of

these are discussed separately in the following subsections.

6RXUFHVRI0DWHULDO

Recyclers are the producers of scrap metal. Recyclers can be the general public (e.g., recycling

copper wire), industry (e.g., recycle disused copper items), or manufacturers (e.g., scrap produced

during manufacture of end products). 

A total of 1.32E+6 t (1.5E+6 ton) of secondary copper—scrap—was consumed in the U.S. in

1995 (USBM 1997). Similar to steel scrap, there are three types of scrap metal used in the

copper-making industry: home, new, and old. Home scrap consists of unusable metal produced

during the processing or fabrication of copper into a form usable for manufacturing. Home scrap

is usually high-grade metal with very few impurities. Even though home scrap is produced at the

refinery, it is still considered a secondary metal because it is not the processed raw material. New

scrap is produced during manufacture of end products. New scrap also is high-grade metal with

very few impurities. Old scrap includes obsolete, worn-out or broken products that have been

used by the general public or industry. Old scrap is usually low-grade metal and the chemical

composition is not well-known. Therefore, it must first be sorted, sized, and classified. Cleared

scrap metal from the nuclear industry is considered old scrap. 
Section 5 Evaluation of Copper

 1Recycle/Reuse Literature Search Report, SAIC, 1994 scheduled to be published as NUREG/CR-5610

5-3 NUREG-1640

Transportation

&

Handling

Scrap Dealer

&

Processor

Existing

Recyclers

Blast

Furnace

Reverberatory

Furnace

Transportation

to

Refinery

Use

Transportation

Transportation

&

Handling

Disposal

Manufacturing

&

Processing

Converter Electrorefining

Direct Disposal

Slag

Copper-rich Slag

Cleared

 Scrap

Recycle

Figure 5.1 Material flow for copper scrap

The main producer of the scrap assumed for this study is the nuclear industry (decommissioned

material from nuclear facilities), which consists mainly of commercial power plants, test and

research reactors, and industrial nuclear facilities. Other producers of such scrap include the

Department of Energy (DOE) weapons complex and the Department of Defense (DOD), which

would contribute slightly contaminated scrap primarily from conventional weapons testing and

army and navy test reactors. Approximately 1.0E+3 t/y (1.1E+3 ton/y) of potentially recyclable

copper and brass scrap metal is generated each year from NRC licensed facilities. Increased

dismantling and decommissioning activities could result in approximately 1.80E+4 t/y (2.0E+4

ton/y) of copper scrap (NUREG/CR-56101

) for a limited number of years. Current home, new,
Evaluation of Copper Section 5

 1Personal communication between M. Anderson, SAIC and G. Golebiowski, Muellar Copper Tube Co., May 27, 1997.

 2Personal communication between M. Anderson, SAIC and J. Schuster, Cerro Copper Tube Co., May 27, 1997.

NUREG-1640 5-4

and old scrap is essentially uncontaminated. Similar to the steel analysis, cleared copper scrap is

assumed to be mixed with a single source of uncontaminated scrap. 

7UDQVSRUWDWLRQDQG3URFHVVLQJ

Scrap copper cleared from a nuclear facility must be transported to a scrap dealer or processor;

this would most likely be done by a commercial company. Because not all licensee scrap is

likely to be suitable for recycle, some would be transported directly to a disposal site. In all

cases, transportation could occur either by truck or rail.

After scrap is processed at a scrap dealer, it is transported by either rail or truck to a refinery. 

The types of activities performed at the scrap refinery include shearing the metal into size,

briquetting or crushing thin and lightweight materials (e.g., turnings and borings), magnetically

separating iron, and cleaning and degreasing (Bever 1986). Slag, metal products, and dust

produced at the refinery or mill are transported to manufacturers or processors by either truck,

rail, or waterway.

&RSSHU0LOOV

Copper scrap can be used in many different types of refineries and mills. According to Smith

(1996) approximately 30% of the scrap consumed was in copper smelters and refiners, 51% in

brass mills, 10% in brass and bronze ingot makers, and the remaining by miscellaneous

manufacturers, foundries, and chemical plants. Brass mills use mainly new scrap while copper

smelters and refiners use mainly old scrap. Because it is possible and likely that scrap from the

nuclear industry would be recycled in brass mills as well as copper smelters and refiners, both

have been analyzed. The typical furnace that scrap would enter for copper recycling is the

reverberatory furnace. The output from the reverberatory furnace can then be further refined in a

converter and electrorefiner.

5HYHUEHUDWRU\)XUQDFH

In the reverberatory furnace, the lighter impurities combine and float to the top of the melt as a

slag that is skimmed off and discarded, while the copper, iron, most of the sulfur, and any

contained precious metals form a product know as “matte” (USBM 1985). This molten matte is

collected and is drawn off from the lower part of the furnace. The copper matte from the

reverberatory furnace has a typical copper concentration between 50% and 75% (EPA 1995). 

According to industry, a typical reverberatory furnace operates at a temperature of about 1100EC

(2000EF). Very small amounts of sand and limestone additives are typically added to the

furnace.1,2 A typical charge size for a reverberatory furnace ranges from 18–499 t (20-550 tons).1

An average value of 227 t (250 tons) is used2

 in the model. A typical copper refinery using a
Section 5 Evaluation of Copper

 1Personal communication between M. Anderson, SAIC and G. Golebiowski, Muellar Copper Tube Co., May 27, 1997.

 2Personal communication between M. Anderson, SAIC and J. Schuster, Cerro Copper Tube Co., May 27, 1997.

5-5 NUREG-1640

reverberatory furnace has an average of 1016 t (1,120 ton) of charge/furnace-day (Butts 1970). 

This results in about 4 charges/day for a single furnace or 1460 charges/year.

The brass refineries operate at temperatures similar to the reverberatory furnace. Brass refineries

use either rotary or electric furnaces. A typical charge size for a rotary furnace ranges from 9–45

t (10–50 tons), while the electric furnace has a typical charge size of about 2.3 t (2.5 ton). There

is no slag produced in the electric furnace. The output of a reverberatory furnace in brass

refineries is assumed to be similar to the output of the copper refinery reverberatory furnace.

&RQYHUWHU

The matte from the reverberatory furnace is fed into the converter where air flowing through the

matte burns off the sulfur, oxidizes the iron for removal in a slag, and yields a product called

“blister” copper (USBM 1985). A typical converter must operate between 1220EC and 1350EC

(2230EF–2460EF) (Butts 1970). Below 1220EC the temperature is too low to form a true slag,

while above 1350EC the heat will wear out the basic lining very rapidly. Converter slags are

generally disposed of by pouring them back into the blast furnaces (Butts 1970). 

(OHFWURUHILQHU

The blister copper from the converter is approximately 99.5% Cu. It is first cast into anodes that

are fed into the electrorefiner. Electrorefining consists of placing the impure copper anodes and

thin, pure-copper cathode starting sheets in a CuSO4-H2SO4-H2O electrolyte and passing a direct

current between them. The electric current causes the copper to dissolve from the anode and

plate in pure form on the cathode (Bever 1986). Cathodes are typically grown for 10-14 days to a

weight of about 150 kg (330 lbs). The anodes are left in the electrolytic cells until they are

almost completely dissolved, usually forming two batches of cathodes. The undissolved anode

scrap is washed, melted, and recast as fresh anodes for further refining (Bever 1986). Solid

impurities in the anodes fall to the bottom of the cell as a sludge where they are ultimately

collected and processed for the recovery of precious metals such as gold and silver. This

material is known as “anode slime” (EPA 1986).

The fumes that are generated during the refining of copper scrap are captured by the primary

exhaust hood and transported via a duct system to a baghouse. The baghouse used in the refining

of copper scrap is similar to those used in the iron and steel industry. Therefore, the same

parameters for the baghouse are used for the recycling of copper (e.g., temperature, efficiency). 

The baghouse dust produced during the refining of copper scrap is not considered hazardous.1,2
Evaluation of Copper Section 5

NUREG-1640 5-6

2XWSXWRI5HILQHU\3URFHVVHV

During each of the refining processes, the original metal separates into four different end

products: off-gas, dust, slag, and metal (Figure 5.1). Each radionuclide is partitioned into these

four materials in an element-specific manner. This process is described using mass partitioning

factors and element-specific elemental partitioning factors. Partitioning factors are defined as the

fraction of original radionuclide concentration or mass entering the refinery furnace that would

be present in various end products. These partitioning factors for copper are discussed in detail

in Section 5.3.

Each of the end products undergoes a different process, use, and final disposal process. The offgas includes elements that are completely volatilized into stable gases or very fine particles

during refining and then exit the refinery stack. Dust includes elements that are volatilized from

the furnace, form particulates when cooled, and are collected in baghouse filters. (The air

pollution control systems are not 100% efficient, and a small percentage of the dust entering the

baghouse is released into the atmosphere with the off-gas.)

Slag is not considered a hazardous waste, therefore, it can be reprocessed or directly disposed of. 

After slag is removed from the furnace and cooled, it is stored in piles outdoors at the refinery

until it is either used by the refinery or transported to a processor. Because of its high metal

content, slag is usually fed back into the furnace as input material.

Manufacturing and processing converts slag and metal products created at the refineries and mills

into finished products. Manufacturing involves activities such as cutting and shaping the metal. 

Processing of slag involves crushing and sizing. After a metal product or slag is manufactured

into a finished product, it must be transported and distributed to the general public (i.e., end

user). Facilities involved in the distribution of finished metal products include stores and

warehouses. Slag is usually distributed and transported directly from the refinery where it is

produced or the manufacturer where it is processed.

3URGXFW8VH

Finished metal products, and occasionally slag, are used by the public for many applications. 

The largest use of copper metal is in electrical equipment and supplies. Copper and copper alloy

wire are used in manufacturing electric motors and generators, power transmission lines, etc. 

Copper is also used in producing nonelectrical industrial machinery and parts, such as

automobile parts, railroad equipment, and construction materials(e.g., roofing, gutters, nails,

plumbing) (USBM 1985). When copper slag is used instead of being recycled, its use is similar

to that of iron and steel slag (roadbed, railroad ballast).
Section 5 Evaluation of Copper

 1Personal communication between M. Anderson, SAIC and J. Schuster, Cerro Copper Tube Company, May 27, 1997.

 2Personal communication between M. Anderson, SAIC and G. Golebiowski, Muellar Copper Tube Company, May 27, 1997.

5-7 NUREG-1640

'LVSRVDO

The ultimate endpoint for finished metal products, slag, and dust is disposal in a public sanitary

landfill (Resource Conservation and Recovery Act [RCRA] Subtitle D). Discarded end products,

waste from manufacturing, slag direct from the refinery, products made from slag, scrap not

suitable for recycle, and dust are all metal byproducts that could be disposed of in a sanitary

landfill. 

0DVVDQG(OHPHQWDO3DUWLWLRQLQJ)DFWRUVIRU5HILQHU\2SHUDWLRQV

For this analysis, the mass of scrap metal entering a furnace during the refining process is

redistributed into the three immediate products: metal product, slag, and dust. Radioactivity in

incoming scrap metal is redistributed among those products, as well as in the off-gas leaving the

refinery stack. 

0DVV3DUWLWLRQLQJ)DFWRUV

The mass partitioning factors for copper were estimated using information obtained from

industry contacts. Mass partitioning factors were determined for the metal product, slag, and

dust. Between 90% and 96% of the metal mass entering the reverberatory furnace ends up in the

metal product.1,2 Because the dust produced during the recycling of copper scrap is not

considered hazardous, a record of the mass of dust produced per charge is not typically kept by

refineries. However, industry estimates that about 1–2% of the original mass entering the

furnace ends up in the dust. More dust is produced with dirtier scrap. Because very few

additives are added during the recycling of copper, the remaining fraction is assumed to be the

mass partitioning to slag.

No information is readily available to determine the mass partitioning for the converter and

electrorefiner. However, because the metal product entering these furnaces has a higher content

of copper than the metal entering the reverberatory furnace, the percentage of copper recovered is

considered to be at least as great as that recovered for the reverberatory furnace. Therefore, for

the converter, the same mass partitioning factors are used as for the reverberatory furnace. Very

little dust and anode slime is produced during the electrorefining process because of the high

purity of the anodes used in the process. Based on engineering judgement, partitioning to metal

product is estimated to be as high as 98% for the electrorefiner. Partitioning to the anode slime

and dust is estimated to be approximately 1% each.
Evaluation of Copper Section 5

NUREG-1640 5-8

(OHPHQWDO3DUWLWLRQLQJ)DFWRUV

Copper recycling involves three steps: a reverberatory furnace, a converter furnace, and an

electrorefinery. For the first two furnaces the primary mechanism for impurity removal is

oxidation. The first furnace, the reverberatory furnace, removes those impurities that are

significantly greater in oxidation potential than copper, while the second, the converter, removes

most elements with oxidation potential less than that of copper. In the third step, the

electrorefiner, copper preferentially plates out at the cathode while many impurities, such as lead

and tin, are left in the anode slime. Nickel accumulates in the electrolyte. Extremely low

concentrations of many impurities may be difficult to remove from the copper.

The elemental partitioning factors determined for the material flow model are intended to be

representative of the expected behavior during melting beginning with a typical domestic

reverberatory furnace. Direct thermodynamic calculations of the oxidation potential of each

element were used in estimating elemental partition factors at temperatures typical of the

reverberatory furnace and the converter. When these calculations were not possible, elemental

partitioning factors were estimated based on the behavior of chemically similar elements. There

is significant variability in the behavior of elements during copper refining depending on initial

concentration, temperature of the melt, and the presence of chemically similar elements. Any

single partitioning value used in the material flow model has some associated uncertainty. In

order to address this uncertainty, ranges for the elemental partitioning values were used. 

During refining, radionuclides could partition to one or both of the main melt components (i.e.,

the slag and metal phases) or discharge from the furnace in the volatilized gas. Some of the

radionuclides that leave the furnace in the volatilized gas would remain in the vapor phase (offgas) and some would condense or coalesce into particulates (dust). Radionuclides found in

coarse particulates would be captured by the baghouse filter. Some of the fine particles and

species in the vapor phase would escape in the off-gas exiting the stack. 

Table 5.1 shows the resulting elemental partitioning factors (EPF) for each element. Note that

the partitioning factors for some elements (e.g., iodine) do not sum to 100% since the values of

the partitioning factors are estimated over a range.

0DWKHPDWLFDO0RGHOIRU)ORZRI5HF\FOHG&RSSHU6FUDS

This section presents the equations that represent the information discussed previously in Section

5.2 and 5.3 and are used to formulate the mathematical model. The equations estimate

radionuclide concentrations in refined copper and other co-products of refining. The equations

are entered into spreadsheets that have been organized and structured specifically for this

analysis. The calculated radionuclide concentrations in refined copper, refinery slag, refinery

baghouse dust, and the amount of radioactivity released out the refinery stack are used as input to

the scenario analyses.
Section 5 Evaluation of Copper

5-9 NUREG-1640

Table 5.1 Elemental partitioning factor ranges (%) for copper refining

Reverberatory Furnace

Elements Matte Slag

Baghouse

Dust Off-gas

Cu 99–100 .99–1.01 0 0

Ag, Bi, Cd, Co, Cr, Fe, Ir, Mn, Mo, Nb, Ni, Pb, Sb 94–100 .95–1.05 0 0

Po, Re, Ru, Tc, Zr, 69–100 .7–1.3 0 0

Zn 89–99 .95–1.05 4.75–5.25 0

Ac, Am, Cm, Np, Pa, Pu, Th, U 0–5 95–100 0 0

P, S, Se 0–30 70–100 0 0

Ca, Cs, K, Na 0 94–100 .95–1.05 0

Ba, Sr 35–65 35–65 0 0

Ce, Eu, Pm, Y, 19–31 56–94 0 0

Ra 19–31 19–31 0 0

C 0 38–62 0 71–100

I 0 59–100 0 .6–1.4

Cl 0 30–70 29–69 .9–1.1

H, Rn 0–5 0 0 95–100

Converter

Elements

Blister

Copper Slag

Baghouse

Dust Off-gas

Cu 98–100 .99–1.01 0 0

Ag, Ir 94–100 .05–1.05 0 0

Bi, Co, Cr, Fe, Mn, Mo, Nb, Ni, Sb 9.5–10.5 86–94 0 0

Re, Ru, Tc, Zr 7–13 63–100 0 0

Cd, Pb, Zn 9.5–10.5 0 86–94 0

Po 9.5–10.5 0 63–100 0

Ac, Am, Cm, Pa, Np, Pu, Th, U 0–5 95–100 0 0

P, S, Se 0–30 70–100 0 0

Ca, Cs, K, Na 0 94–100 .95–1.05 0

Ba, Sr 35–65 35–65 0 0

Ce, Eu, Pm, Ra Y 19–31 56–94 0 0

C 0 3.8–6.2 0 71–100

I 0 59–100 0 .6–1.4

Cl 0 30–70 29–69 .9–1.1

H, Rn 0–5 95–100 0 95–100

Electrorefiner

Elements Copper

Anode Slime Baghouse

Dust Off-gas

Cu 99–100 0–1 0 0

Ac, Ag, Am, Ba, Bi, Ca, Cd, Ce, Cm, Co, Cr, Cs, Eu,

Fe, Ir, K, Mn, Mo, Na, Nb, Ni, Np, Pa, Pb, Pm, Po,

Pu, Ra, Re, Ru, Sb, Sr, Tc, Th, U, Y, Zn, Zr

0–1 99–100 0 0

P, S, Se 0–5 70–100 0 0

C, H, Rn 0–5 0 0 95–100

I 0–20 0 0 80–100

Cl 0 0 38–62 38–62
Evaluation of Copper Section 5

NUREG-1640 5-10

0 ' 0 % 01& 5.1

0L[LQJRI&OHDUHGDQG2WKHU6FUDS

There are only two processes by which the original concentration of each radionuclide in cleared

copper scrap can be potentially changed. The first can occur upon mixing with other scrap metal

prior to refining. This mixing is a radionuclide-independent process, so the radioactivity

concentration of all radionuclides is effected the same when mixing cleared copper scrap with a

given mass of other copper scrap. The second process is the refining process itself, which

generally consists of melting the copper scrap metal results in a redistribution (partitioning) of

mass and radioactivity. Partitioning of mass during melting is radionuclide independent,

however, partitioning of radioactivity during refining is element dependent. The following

equations are used to calculate the concentrations in refinery co-products at those points in the

material flow which correspond to potential exposure scenarios.

The following set of equations is used for all three steps used in copper refining (reverberatory

furnace, converter furnace, and electrorefiner). Copper refining is a sequential process (except

for the reflux from the converter, which is assumed to be steady state), so the calculated mass and

radioactivity concentrations in refined copper from the reverberatory furnace is used as input to

the converter furnace. Similarly, the output from the converter furnace is used as input to the

electrorefiner.

The total mass of material entering the furnace in a year, including cleared material, other scrap,

and primary metal was calculated using Equation 5.1.

where

M1 = total mass of scrap metal entering the furnace per charge (g/charge)

and

M0 = mass of cleared material entering the furnace per charge (g/charge)

MNC = mass of other scrap metal entering the furnace per charge (g/charge)

Mixing of cleared scrap with metal from sources other than licensed facilities can occur at the

scrap dealer (i.e., secondary metal pool) and at the refinery, where material from the primary

metal pool enters the furnace. In this analysis, no distinction is made between the two sources of

other metal. The mass of other metal includes contributions at the scrap yard and at the refinery.

The radionuclide concentration in the metal entering the furnace was calculated using

Equation 5.2. The following equations are intended to be evaluated separately for each

radionuclide in the analysis. Therefore, parameters such as concentration, decay factors, decay

constants, and dose conversion factors are not explicitly subscripted for each radionuclide.
Section 5 Evaluation of Copper

5-11 NUREG-1640

& ' 0

0

( & 5.2

0V ' 0 ( I

V ( &3< 5.3 

0G ' 0 ( I

G ( &3< 5.4

0

S ' 0 ( IS ( &3< 5.5

where

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

and

M0 = mass of cleared material entering the furnace per charge (g/charge)

M1 = total mass of scrap metal entering the furnace per charge (g/charge)

C0 = original radionuclide concentration in cleared material (pCi/g)

For slag, baghouse dust, and off-gas, Equations 5.1 and 5.2 were evaluated using annual average

values for the masses of scrap entering the furnaces because all the exposure scenarios for these

materials depend on annual average concentrations. For metal, both an annual average and a

single charge evaluation of Equations 5.1 and 5.2 were conducted. This was done for metal

because there are metal products that could easily be manufactured from a single refinery charge. 

The single charge concentrations were used in metal product-use exposure scenarios except

where noted. (See Appendix D for additional details.)

5HILQHU\3URFHVVHV

To accurately account for concentration changes in the different products, the mass of each

refinery product must be calculated. Equations 5.3, 5.4, and 5.5 are used to calculate the masses

of slag, dust, and metal product, respectively (no mass is associated with the completely

volatilized elements).

Where

Ms = mass of slag produced from a refinery per year (g/y)

Md = mass of dust produced from a refinery per year (g/y)

Mp = mass of metal product produced from a refinery per year (g/y)

and

M1 = total mass of scrap entering the furnace per charge (g/charge)
Evaluation of Copper Section 5

NUREG-1640 5-12

&V' & ( I

V ( 0

0 ( I

V

' & ( I

V

I

V

5.6

&G' & ( I

G

I

G

5.7

fs1 = mass partitioning factor for slag during the refining process (dimensionless)

fd1 = mass partitioning factor for dust during the refining process (dimensionless)

fp1 = mass partitioning factor for metal product during the refining process

(dimensionless)

CPY = number of charges per refinery per year (charge)

The total amount of radioactivity in the original metal entering the furnace during the refining

process is partitioned among four product materials. Equation 5.6 shows the calculation for

radionuclide concentration in slag, taking into account both the mass and elemental partitioning

factors.

where

Cs = radionuclide concentration in slag after the refining process (pCi/g)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

fs = slag elemental partitioning factor during the refining process (dimensionless)

M1 = total mass of scrap entering the furnace per charge (g/charge)

fs1 = mass partitioning factor for slag during the refining process (dimensionless)

The concentration of radionuclides in the dust and metal product are similarly calculated using

Equations 5.7 and 5.8, respectively.

where

Cd = radionuclide concentration in dust after the refining process (pCi/g)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

fd = dust elemental partitioning factor during the refining process(dimensionless)

fd1 = mass partitioning factor for dust during the refining process (dimensionless)
Section 5 Evaluation of Copper

5-13 NUREG-1640

&

S' & ( I

S

I

S

5.8

$

J ' & ( 0 ( IJ ( &3< 5.9

0UD ' 0G (  & %+HII 5.10

0GE ' 0G & 0UD 5.11

where

Cp = radionuclide concentration in metal product after the refining process (pCi/g)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

fp = metal product elemental partitioning factor during the refining process

(dimensionless)

fp1 = mass partitioning factor for metal product during the refining process

(dimensionless)

No mass is explicitly calculated for the refinery off-gas. Exposure scenarios for atmospheric

effluents are based on the total amount of radioactivity released from the refinery stack each year. 

The annual amount of radioactivity in the off-gas was calculated using Equation 5.9. 

where

Ag = radioactivity in the off-gases leaving the refinery stack in a year (pCi/y)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

M1 = total mass of scrap entering the furnace per charge (g/charge)

fg = off-gas elemental partitioning factor during the refining process (dimensionless)

CPY = number of charges per refinery per year (charge)

Equations 5.10 and 5.11 are used to calculate the mass of dust that escapes the baghouse filters

and the mass that is captured in the baghouse, respectively. 

where

Mra = total mass of dust that escapes the baghouse in a year (g/y)

and

Md = mass of dust produced from the refining process in a year (g/y)

BHeff = baghouse efficiency (dimensionless)

where

Mdb = total mass of dust captured in the refinery baghouse in a year (g/y)

and
Evaluation of Copper Section 5

NUREG-1640 5-14

Md = mass of dust produced from the refining process in a year (g/y)

Mra = total mass of dust that escapes the baghouse in a year (g/y)

5DGLRDFWLYLW\&RQFHQWUDWLRQVLQ&RSSHU5HILQLQJ&RSURGXFWV

Mean radionuclide concentrations in the co-products from copper refining are listed in Tables 5.2

through 5.4 for each of the three refining steps. These values represent estimated radioactivity

concentrations in the refinery output. The values are normalized to a unit radioactivity

concentration in scrap and are only listed in S.I. units since the values are numerically identical if

expressed in conventional units (e.g., pCi/g product per pCi/g scrap).

As stated above, Tables 5.2 through 5.4 list the mean concentration of each radionuclide in each

medium. Tabulations are limited to mean values simply because of the space that would be

required if percentiles from the distributions were also tabulated. The entire distribution of

values for each radionuclide in the appropriate medium was used as input for the exposure

scenario analysis.
Section 5 Evaluation of Copper

5-15 NUREG-1640

Table 5.2 Results of material flow model—copper reverberatory furnace

Mean radionuclide concentrations in refinery products (Bq/g product per Bq/g scrap)

Refined Metal Off-gas

Nuclide Single Charge Annual Slag Dust (Bq per Bq/g)

H-3 1.4E-02 3.2E-04 0.0E+00 0.0E+00 3.1E+10

C-14 0.0E+00 0.0E+00 1.6E-02 0.0E+00 2.7E+10

Na-22 0.0E+00 0.0E+00 3.1E-01 1.6E-02 0.0E+00

P-32 1.3E-01 2.9E-03 2.7E-01 0.0E+00 0.0E+00

S-35 1.3E-01 2.9E-03 2.7E-01 0.0E+00 0.0E+00

Cl-36 0.0E+00 0.0E+00 1.6E-01 8.0E-01 3.1E+08

K-40 0.0E+00 0.0E+00 3.1E-01 0.0E+00 0.0E+00

Ca-41 0.0E+00 0.0E+00 3.1E-01 1.6E-02 0.0E+00

Ca-45 0.0E+00 0.0E+00 3.1E-01 1.6E-02 0.0E+00

Cr-51 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Mn-54 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Fe-55 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Co-57 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Co-58 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Fe-59 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Ni-59 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Co-60 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Ni-63 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Zn-65 8.1E-01 1.8E-02 3.1E-03 8.2E-02 0.0E+00

Cu-67 8.5E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Se-75 1.3E-01 3.0E-03 2.7E-01 0.0E+00 0.0E+00

Sr-85 4.3E-01 9.6E-03 1.6E-01 0.0E+00 0.0E+00

Sr-89 4.3E-01 9.6E-03 1.6E-01 0.0E+00 0.0E+00

Sr-90 4.3E-01 9.6E-03 1.6E-01 0.0E+00 0.0E+00

Y-91 2.2E-01 4.8E-03 2.3E-01 0.0E+00 0.0E+00

Mo-93 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Nb-93m 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Nb-94 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Nb-95 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Zr-95 7.3E-01 1.6E-02 3.1E-03 0.0E+00 0.0E+00

Tc-99 7.3E-01 1.6E-02 3.1E-03 0.0E+00 0.0E+00

Ru-103 7.3E-01 1.6E-02 3.1E-03 0.0E+00 0.0E+00

Ru-106 7.3E-01 1.6E-02 3.1E-03 0.0E+00 0.0E+00

Ag-108m 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Cd-109 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Ag-110m 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Sb-124 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

I-125 0.0E+00 0.0E+00 2.5E-01 0.0E+00 3.1E+08

Sb-125 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

I-129 0.0E+00 0.0E+00 2.5E-01 0.0E+00 3.1E+08

I-131 0.0E+00 0.0E+00 2.5E-01 0.0E+00 3.1E+08

Ba-133 4.3E-01 9.6E-03 1.6E-01 0.0E+00 0.0E+00

Cs-134 0.0E+00 0.0E+00 3.1E-01 1.6E-02 0.0E+00

Cs-137 0.0E+00 0.0E+00 3.1E-01 1.6E-02 0.0E+00
Evaluation of Copper Section 5

Table 5.2 Results of material flow model—copper reverberatory furnace

Mean radionuclide concentrations in refinery products (Bq/g product per Bq/g scrap)

Refined Metal Off-gas

Nuclide Single Charge Annual Slag Dust (Bq per Bq/g)

NUREG-1640 5-16

Ce-141 2.2E-01 4.8E-03 2.4E-01 0.0E+00 0.0E+00

Ce-144 2.2E-01 4.8E-03 2.3E-01 0.0E+00 0.0E+00

Pm-147 2.2E-01 4.8E-03 2.4E-01 0.0E+00 0.0E+00

Eu-152 2.2E-01 4.8E-03 2.3E-01 0.0E+00 0.0E+00

Eu-154 2.2E-01 4.8E-03 2.4E-01 0.0E+00 0.0E+00

Eu-155 2.2E-01 4.8E-03 2.4E-01 0.0E+00 0.0E+00

Re-186 7.3E-01 1.6E-02 3.2E-03 0.0E+00 0.0E+00

Ir-192 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Pb-210 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Po-210 7.3E-01 1.6E-02 3.2E-03 0.0E+00 0.0E+00

Bi-210 8.4E-01 1.9E-02 3.1E-03 0.0E+00 0.0E+00

Rn-222 1.4E-02 3.2E-04 0.0E+00 0.0E+00 3.1E+10

Ra-223 2.2E-01 4.8E-03 7.8E-02 0.0E+00 0.0E+00

Ra-224 2.2E-01 4.8E-03 7.8E-02 0.0E+00 0.0E+00

Ac-225 1.4E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Ra-225 2.2E-01 4.8E-03 7.9E-02 0.0E+00 0.0E+00

Ra-226 2.2E-01 4.8E-03 7.8E-02 0.0E+00 0.0E+00

Ac-227 1.5E-02 3.3E-04 3.1E-01 0.0E+00 0.0E+00

Th-227 1.4E-02 3.3E-04 3.1E-01 0.0E+00 0.0E+00

Th-228 1.5E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Ra-228 2.2E-01 4.8E-03 7.8E-02 0.0E+00 0.0E+00

Th-229 1.4E-02 3.3E-04 3.1E-01 0.0E+00 0.0E+00

Th-230 1.4E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Pa-231 1.4E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Th-231 1.4E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Th-232 1.4E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Pa-233 1.5E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

U-233 1.5E-02 3.1E-04 3.1E-01 0.0E+00 0.0E+00

Th-234 1.4E-02 3.1E-04 3.1E-01 0.0E+00 0.0E+00

U-234 1.4E-02 3.1E-04 3.1E-01 0.0E+00 0.0E+00

U-235 1.5E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Np-237 1.5E-02 3.1E-04 3.1E-01 0.0E+00 0.0E+00

Pu-238 1.4E-02 3.1E-04 3.1E-01 0.0E+00 0.0E+00

U-238 1.4E-02 3.3E-04 3.1E-01 0.0E+00 0.0E+00

Pu-239 1.4E-02 3.3E-04 3.1E-01 0.0E+00 0.0E+00

Pu-240 1.4E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Pu-241 1.4E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Am-241 1.4E-02 3.3E-04 3.1E-01 0.0E+00 0.0E+00

Cm-242 1.5E-02 3.1E-04 3.1E-01 0.0E+00 0.0E+00

Pu-242 1.4E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00

Cm-244 1.4E-02 3.2E-04 3.1E-01 0.0E+00 0.0E+00
Section 5 Evaluation of Copper

5-17 NUREG-1640

Table 5.3 Results of material flow model—copper converter furnace

Mean radionuclide concentrations in refinery products (Bq/g product per Bq/g scrap)

Nuclide Refined Metal Slag Dust

H-3 5.7E-06 0.0E+00 0.0E+00

C-14 0.0E+00 0.0E+00 0.0E+00

Na-22 0.0E+00 0.0E+00 0.0E+00

P-32 4.7E-04 4.2E-02 0.0E+00

S-35 4.7E-04 4.2E-02 0.0E+00

Cl-36 0.0E+00 0.0E+00 0.0E+00

K-40 0.0E+00 0.0E+00 0.0E+00

Ca-41 0.0E+00 0.0E+00 0.0E+00

Ca-45 0.0E+00 0.0E+00 0.0E+00

Cr-51 2.0E-03 2.9E-01 0.0E+00

Mn-54 2.0E-03 2.9E-01 0.0E+00

Fe-55 2.0E-03 2.9E-01 0.0E+00

Co-57 2.0E-03 2.9E-01 0.0E+00

Co-58 2.0E-03 2.9E-01 0.0E+00

Fe-59 2.0E-03 2.9E-01 0.0E+00

Ni-59 2.0E-03 2.9E-01 0.0E+00

Co-60 2.0E-03 2.9E-01 0.0E+00

Ni-63 2.0E-03 2.9E-01 0.0E+00

Zn-65 1.9E-03 0.0E+00 1.5E+00

Cu-67 2.0E-02 3.3E-03 0.0E+00

Se-75 4.5E-04 4.2E-02 0.0E+00

Sr-85 5.1E-03 8.3E-02 0.0E+00

Sr-89 5.1E-03 8.3E-02 0.0E+00

Sr-90 5.1E-03 8.3E-02 0.0E+00

Y-90 1.3E-03 6.3E-02 0.0E+00

Y-91 1.3E-03 6.3E-02 0.0E+00

Mo-93 2.0E-03 2.9E-01 0.0E+00

Nb-93m 2.0E-03 2.9E-01 0.0E+00

Nb-94 2.0E-03 2.9E-01 0.0E+00

Nb-95 2.0E-03 2.9E-01 0.0E+00

Zr-95 1.7E-03 2.3E-01 0.0E+00

Tc-99 1.7E-03 2.3E-01 0.0E+00

Ru-103 1.7E-03 2.3E-01 0.0E+00

Ru-106 1.7E-03 2.3E-01 0.0E+00

Ag-108m 1.9E-02 2.3E-03 0.0E+00

Cd-109 2.0E-03 0.0E+00 1.6E+00

Ag-110m 1.9E-02 2.3E-03 0.0E+00

Sb-124 2.0E-03 2.9E-01 0.0E+00

I-125 0.0E+00 0.0E+00 0.0E+00

Sb-125 2.0E-03 2.9E-01 0.0E+00

I-129 0.0E+00 0.0E+00 0.0E+00

I-131 0.0E+00 0.0E+00 0.0E+00

Ba-133 5.1E-03 8.4E-02 0.0E+00

Cs-134 0.0E+00 0.0E+00 0.0E+00

Cs-137 0.0E+00 0.0E+00 0.0E+00

Ce-141 1.3E-03 6.3E-02 0.0E+00

Ce-144 1.3E-03 6.3E-02 0.0E+00

Pm-147 1.3E-03 6.2E-02 0.0E+00

Eu-152 1.3E-03 6.2E-02 0.0E+00

Eu-154 1.3E-03 6.2E-02 0.0E+00
Evaluation of Copper Section 5

Table 5.3 Results of material flow model—copper converter furnace

Mean radionuclide concentrations in refinery products (Bq/g product per Bq/g scrap)

Nuclide Refined Metal Slag Dust

NUREG-1640 5-18

Eu-155 1.3E-03 6.2E-02 0.0E+00

Re-186 1.7E-03 2.3E-01 0.0E+00

Ir-192 2.0E-02 2.3E-03 0.0E+00

Pb-210 2.0E-03 0.0E+00 1.5E+00

Po-210 1.7E-03 0.0E+00 1.2E+00

Bi-210 2.0E-03 2.9E-01 0.0E+00

Rn-222 5.3E-06 0.0E+00 4.9E+08

Ra-223 1.3E-03 6.3E-02 0.0E+00

Ra-224 1.3E-03 6.3E-02 0.0E+00

Ac-225 5.6E-06 5.4E-03 0.0E+00

Ra-225 1.3E-03 6.3E-02 0.0E+00

Ra-226 1.3E-03 6.3E-02 0.0E+00

Ac-227 5.6E-06 5.4E-03 0.0E+00

Th-227 6.1E-06 5.6E-03 0.0E+00

Th-228 6.1E-06 5.6E-03 0.0E+00

Ra-228 1.3E-03 6.3E-02 0.0E+00

Th-229 6.1E-06 5.6E-03 0.0E+00

Th-230 6.1E-06 5.6E-03 0.0E+00

Pa-231 6.0E-06 5.6E-03 0.0E+00

Th-231 6.1E-06 5.6E-03 0.0E+00

Th-232 6.1E-06 5.6E-03 0.0E+00

Pa-233 6.0E-06 5.6E-03 0.0E+00

U-233 5.8E-06 5.5E-03 0.0E+00

Th-234 6.1E-06 5.6E-03 0.0E+00

U-234 5.8E-06 5.5E-03 0.0E+00

U-235 5.8E-06 5.5E-03 0.0E+00

Np-237 5.8E-06 5.4E-03 0.0E+00

Pu-238 5.7E-06 5.6E-03 0.0E+00

U-238 5.8E-06 5.5E-03 0.0E+00

Pu-239 5.7E-06 5.6E-03 0.0E+00

Pu-240 5.7E-06 5.6E-03 0.0E+00

Pu-241 5.7E-06 5.6E-03 0.0E+00

Am-241 5.8E-06 5.5E-03 0.0E+00

Cm-242 6.0E-06 5.5E-03 0.0E+00

Pu-242 5.7E-06 5.6E-03 0.0E+00

Cm-244 6.0E-06 5.5E-03 0.0E+00

NOTES:

 1) All values are annual averages because single charge values are not needed for any scenarios.

 2) Only one radionuclide is partitioned to off-gas, H-3, with an annual release of 5.02E+08 Bq per Bq/g

scrap.

 3) Radionuclides that have mean concentrations of zero for all refinery products have concentrations of

0 Bq/g in the matte input to the converter.
Section 5 Evaluation of Copper

5-19 NUREG-1640

Table 5.4 Results of material flow model—copper electrorefinery

Mean concentrations in refinery products (Bq/g product per Bq/g scrap)

Refined Metal

Nuclide Single Charge Annual Slag

H-3 4.2E-06 9.5E-08 0.0E+00

C-14 0.0E+00 0.0E+00 0.0E+00

Na-22 0.0E+00 0.0E+00 0.0E+00

P-32 3.2E-03 6.6E-05 2.4E-02

S-35 3.2E-03 7.4E-05 2.4E-02

Cl-36 0.0E+00 0.0E+00 0.0E+00

K-40 0.0E+00 0.0E+00 0.0E+00

Ca-41 0.0E+00 0.0E+00 0.0E+00

Ca-45 0.0E+00 0.0E+00 0.0E+00

Cr-51 3.0E-04 6.9E-06 1.2E-01

Mn-54 3.1E-04 6.9E-06 1.2E-01

Fe-55 3.0E-04 6.7E-06 1.2E-01

Co-57 3.0E-04 6.8E-06 1.2E-01

Co-58 3.0E-04 6.8E-06 1.2E-01

Fe-59 3.0E-04 6.7E-06 1.2E-01

Ni-59 3.0E-04 6.7E-06 1.2E-01

Co-60 3.0E-04 6.8E-06 1.2E-01

Ni-63 3.0E-04 6.7E-06 1.2E-01

Zn-65 2.9E-04 6.5E-06 1.2E-01

Cu-67 9.2E-01 2.0E-02 4.1E-03

Se-75 3.3E-03 7.2E-05 2.4E-02

Sr-85 7.8E-04 1.7E-05 3.1E-01

Sr-89 7.8E-04 1.7E-05 3.1E-01

Sr-90 7.8E-04 1.7E-05 3.1E-01

Y-91 2.0E-04 4.3E-06 7.8E-02

Mo-93 3.0E-04 6.7E-06 1.2E-01

Nb-93m 3.0E-04 6.8E-06 1.2E-01

Nb-94 3.0E-04 6.8E-06 1.2E-01

Nb-95 3.0E-04 6.8E-06 1.2E-01

Zr-95 2.6E-04 6.0E-06 1.1E-01

Tc-99 2.6E-04 6.0E-06 1.1E-01

Ru-103 2.6E-04 5.7E-06 1.1E-01

Ru-106 2.6E-04 5.7E-06 1.1E-01

Ag-108m 2.9E-03 6.6E-05 1.2E+00

Cd-109 3.1E-04 6.7E-06 1.2E-01

Ag-110m 2.9E-03 6.6E-05 1.2E+00

Sb-124 3.1E-04 6.8E-06 1.2E-01

I-125 0.0E+00 0.0E+00 0.0E+00

Sb-125 3.1E-04 6.8E-06 1.2E-01

I-129 0.0E+00 0.0E+00 0.0E+00

I-131 0.0E+00 0.0E+00 0.0E+00

Ba-133 7.7E-04 1.7E-05 3.1E-01

Cs-134 0.0E+00 0.0E+00 0.0E+00

Cs-137 0.0E+00 0.0E+00 0.0E+00

Ce-141 2.0E-04 4.4E-06 7.8E-02

Ce-144 2.0E-04 4.4E-06 7.8E-02

Pm-147 1.9E-04 4.4E-06 7.8E-02

Eu-152 1.9E-04 4.4E-06 7.8E-02

Eu-154 1.9E-04 4.4E-06 7.8E-02
Evaluation of Copper Section 5

Table 5.4 Results of material flow model—copper electrorefinery

Mean concentrations in refinery products (Bq/g product per Bq/g scrap)

Refined Metal

Nuclide Single Charge Annual Slag

NUREG-1640 5-20

Eu-155 1.9E-04 4.4E-06 7.8E-02

Re-186 2.7E-04 5.9E-06 1.1E-01

Ir-192 3.0E-03 6.5E-05 1.2E+00

Pb-210 3.0E-04 6.9E-06 1.2E-01

Po-210 2.6E-04 5.8E-06 1.1E-01

Bi-210 3.0E-04 6.7E-06 1.2E-01

Rn-222 4.7E-06 9.5E-08 0.0E+00

Ra-223 1.9E-04 4.3E-06 7.8E-02

Ra-224 1.9E-04 4.3E-06 7.8E-02

Ac-225 7.9E-07 1.9E-08 3.4E-04

Ra-225 1.9E-04 4.3E-06 7.8E-02

Ra-226 1.9E-04 4.3E-06 7.8E-02

Ac-227 7.9E-07 1.9E-08 3.4E-04

Th-227 9.2E-07 1.7E-08 3.3E-04

Th-228 9.2E-07 1.7E-08 3.3E-04

Ra-228 1.9E-04 4.3E-06 7.8E-02

Th-229 9.2E-07 1.7E-08 3.3E-04

Th-230 9.2E-07 1.7E-08 3.3E-04

Pa-231 9.2E-07 2.0E-08 3.6E-04

Th-231 9.2E-07 1.7E-08 3.3E-04

Th-232 9.2E-07 1.7E-08 3.3E-04

Pa-233 9.2E-07 2.0E-08 3.6E-04

U-233 8.6E-07 1.9E-08 3.5E-04

Th-234 9.2E-07 1.7E-08 3.3E-04

U-234 8.6E-07 1.9E-08 3.5E-04

U-235 8.6E-07 1.9E-08 3.5E-04

Np-237 8.9E-07 2.0E-08 3.4E-04

Pu-238 7.6E-07 1.9E-08 3.4E-04

U-238 8.6E-07 1.9E-08 3.5E-04

Pu-239 7.6E-07 1.9E-08 3.4E-04

Pu-240 7.6E-07 1.9E-08 3.4E-04

Pu-241 7.6E-07 1.9E-08 3.4E-04

Am-241 8.5E-07 1.8E-08 3.3E-04

Cm-242 8.5E-07 2.0E-08 3.4E-04

Pu-242 7.6E-07 1.9E-08 3.4E-04

Cm-244 8.5E-07 2.0E-08 3.4E-04

NOTES:

 1) Only one radionuclide is partitioned to off-gas, H-3, with an annual release of 1.56E+06 Bq per Bq/g

scrap.

 2) Radionuclides that have mean concentrations of zero for all electrorefinery products have concentrations

of 0 Bq/g in the blister input to the electrorefinery.
Section 5 Evaluation of Copper

5-21 NUREG-1640

'7 ' 'LQJ 5.12

'RVH$VVHVVPHQWIRU8QLTXH&RSSHU5HF\FOHDQG'LVSRVDO

6FHQDULRV

Most of the potential exposure scenarios for recycled and disposed copper scrap are adequately

covered by adapting the steel scrap recycle scenarios described in Section 4. Only one scenario

was added to the copper analysis that was not already described: the use of copper or bronze

piping made of recycled copper scrap. This general scenario was included in the evaluation of

copper recycling because it represents a scenario unique to copper and because of the large

amount of copper piping in use in the U.S. 

Recycled copper can be used to make piping or other plumbing fixtures. The additional scenario

described below involves using copper or bronze piping made of recycled copper, where material

that has leached from the piping into the drinking water might be ingested. 

([SRVXUH3DWKZD\V

Ingestion: If copper pipe is used to transport water, a small amount of material could leach from

the inside surface of the pipe to the water. If the water is used for drinking or cooking, the

leached material could be ingested.

Suspension of particulates from copper piping is unlikely, therefore, the inhalation pathway is not

included. Also, external exposure to copper pipes and fixtures was judged to be small in

comparison to ingestion of drinking water and was not included in the modeling.

0DWKHPDWLFDO5HSUHVHQWDWLRQ

The annual total effective dose equivalent (TEDE) is equal to the effective dose equivalent from

the ingestion exposure pathway. The TEDE for a member of the public using copper or bronze

piping is represented by Equation 5.12.

where

DT = TEDE for the scenario (mrem/y)

and

Ding = EDE due to ingestion (mrem/y)

Equation 5.13 calculates the radionuclide concentrations in the piping at the time use occurs. 

This accounts for radioactive decay from the time the scrap is cleared from a nuclear facility to

the time the scenario begins. The reference to "source material" in the parameters of

Equation 5.13 and other equations means the material that represents the source of exposure. In

this scenario, the source material is copper or bronze piping. 
Evaluation of Copper Section 5

NUREG-1640 5-22

& ' &[ H

& U W

V 5.13

'LQJ ' & ( &5&X ( ',: ( ): ( W

\V ( ')LQJ ( (&  5.14

where

C0 = radionuclide concentration in the source material at time the scenario begins (pCi/g)

and

Cx = undecayed radionuclide concentration in the source material (pCi/g)

r = radioactive decay constant (1/d)

ts = time from clearance from nuclear facility to time scenario begins (d)

This scenario includes the assumption that while water is transported through a copper or bronze

piping, a certain amount of piping material is leached from the pipe into the water. The dose due

to this exposure pathway is presented in Equation 5.14.

where

Ding = EDE due to ingestion (mrem/y)

and

C0 = radionuclide concentration in the source material at time the scenario begins (pCi/g)

CRCu = leaching rate for copper (mg Cu/L water)

DIw = total water intake (L water/d)

FW = fraction of total water intake that is from the copper pipes (dimensionless)

DFing = ingestion dose factor (mrem/pCi intake)

1E-03 = unit conversion factor (g/mg)

tys = annual number of days of exposure for the scenario (d/y)

3DUDPHWHU'LVFXVVLRQIRUDOO0RGHOHG6FHQDULRV

Calculation of potential impacts from recycle of cleared copper scrap material depends on many

parameter values. Parameter values are needed for both material flow and dose assessment

models. The material flow parameter values rely on information from the U.S. secondary copper

industry. The parameter values for the dose modeling are a function of receptor behavior, such

as time on a specific job or breathing rate, as well as how the radionuclides are transported in the

environment. The dose modeling parameter values are based on those used in the iron and steel

modeling described in Section 4. Except for scenario timing assumptions, only those parameter

values that are different from those used in the iron and steel modeling are discussed in this

section. 

Nominal parameter values are described below. Ranges were used to define some parameter

values in the modeling. All values and ranges are given in Appendix B.
Section 5 Evaluation of Copper

5-23 NUREG-1640

6FHQDULR7LPLQJ

This section presents the basic assumptions used in defining the time periods for each of the

copper recycle scenarios. They are based on the scenario timing for the basic oxygen furnace

(BOF) iron and steel refinery modeling. The following list of basic assumptions was used in

estimating the timing parameters for the scenarios:

Scrap Handling:

C All cleared scrap metal is assumed to be initially taken to a scrap dealer. It takes 4 days

for the scrap metal to reach the scrap dealer.

C The scrap metal remains at the scrap dealer for a period of 7 days prior to reuse or

disposal and 25 days for scrap metal that is recycled.

Refining and Processing:

C For recycled scrap metal, the refining process and associated product manufacture, final

processing, and any on-site storage at the refinery takes a total of 15 days for each of the

reverberatory, converter, and electrorefinery facilities.

C The metal product output from the reverberatory and converter facilities immediately

enters the converter and electrorefinery, respectively.

C Following initial processing, reverberatory and electrorefinery products undergo further

processing before use. This secondary processing, plus storage and handling takes 22

days.

C Distribution of products from the reverberatory and converter takes 7 days.

C Radionuclide releases into the atmospheric effluent from the reverberatory and converter

occur at the time the scrap is refined, i.e., 29 and 44 days after clearance, respectively.

Use and Disposal:

C An electrorefinery metal product is used for 30 years, based on an assumed use in the

construction industry. Use of a reverberatory metal product is 10 years, based on an

assumed general purpose use (IAEA 1992).

C Reverberatory, converter and electrorefinery slag and baghouse dust are produced at the

time refining occurs, 29, 44, and 59 days, respectively, after clearance of scrap metal from

a licensee.
Evaluation of Copper Section 5

NUREG-1640 5-24

C Refinery slag that is sold for subsequent use is processed at the refinery 3 days after

production and leaves the refinery in another 2 days. Slag is used within 2 days after

distribution and is used for a period of 30 years. Once the period of use is completed, the

products are disposed of in a sanitary landfill. Slag that is to be directly disposed is held

at the refinery for 7 days, at which time it is transported to a disposal facility. The slag is

assumed to be disposed immediately following handling at a sanitary landfill.

C Baghouse dust from the reverberatory, converter, and electrorefinery is disposed of onsite

or sent to a sanitary disposal facility after 7 days. Storage and handling takes 4 days, at

which time disposal occurs.

'RVH(YDOXDWLRQ

This section presents a discussion of parameter values used for the analysis of copper recycle

scenarios. In general, the same scenarios are analyzed for copper recycle as were analyzed for

steel recycle in Section 4. Values used for many of the parameters are also the same as for the

steel recycle analysis. For some parameters, however, values specific to the recycle of copper

were used in order to more appropriately model the scenarios as they would likely occur for

copper recycle. The following discussion is limited to these specific parameter values. If a

parameter is not discussed below and listed in Table B.9, the same value as used for the steel

evaluation (Table B.7) is used for copper.

,QSXW&RQFHQWUDWLRQVIURPWKH0DWHULDO)ORZ

The undecayed radionuclide concentration in the source material, Cx, is used as the source

material input radionuclide concentration for scenario evaluations. This parameter is

radionuclide dependent and is calculated in the material flow modeling. Table B.11 lists the

sources for Cx, as they appear in the mathematical modeling of the material flow (e.g., Cp,

concentration in metal product after the refining process).

([WHUQDO([SRVXUH3DUDPHWHUV

This section describes the value used for one parameter needed for calculating external exposure

including those that address duration of exposure and material density. Values for these

parameters are tabulated in Table B.9.

For the scrap disposal scenario a fixed value of 4.47E+6 g/m3

 is used for the density of waste,

consistent with the value used in the calculation of the geometry factors for metal products.

,QJHVWLRQ([SRVXUH3DUDPHWHUV

This section describes the values used for those unique parameters needed for calculating

ingestion exposure.
Section 5 Evaluation of Copper

5-25 NUREG-1640

The use of copper or bronze pipes can increase the concentration of copper in drinking water. 

When water is allowed to remain in the pipes for a period of time, copper can leach from the

pipes into the water. Soft water is more corrosive than hard water, therefore enhancing leaching

of copper from the pipes (U.S. Public Health Services 1990). When pipes have not been flushed

after a period of disuse, the concentration of copper in tap water may exceed 1.3 ppm (1.3 mg

Cu/L water), which is the EPA drinking-water limit (U.S. Public Health Services 1990). U.S.

Public Health Services (1990) presents results from a number of different studies. One study in

Canada found that the copper concentration in treated water that has not been exposed to copper

pipes was generally very low, # 10 ppb (0.01 mg Cu/L water). Another study in Seattle, WA

showed the mean copper concentrations in running and standing water from copper pipes were

0.16 and 0.45 ppm, respectively, with an average value of 0.31 ppm (0.31 mg Cu/L water), and

an increase in copper concentration due to leaching of copper from the pipes of 0.3 mg Cu/L

water. A triangular distribution, with a minimum of 0.16 mg Cu/L, a most likely value of 0.3 mg

Cu/L, and a maximum of 1.3 mg Cu/L is used to represent the variation in observed data for the

parameter CRcu, the concentration of copper in tap water due to leaching from pipes.

Analysis of survey data has shown that tap water averages about 60% of total water consumption

(Roseberry and Burmaster 1992). This analysis supports a lognormal distribution for total tap

water consumption having a geometric mean of 1400 ml/d and a geometric standard deviation of

1.78. In addition, not all tap water consumption comes from one’s own tap. A significant

number of meals are eaten outside one’s home, for example. The data on the fraction of tap

water from one’s own tap are poor and are best represented by a uniform distribution having a

minimum of 0.5 and a maximum of 1.0.

$WPRVSKHULF5HOHDVH3DUDPHWHUV

The only parameter value for atmospheric dispersion of refinery stack releases from copper

recycling facilities that is different from the steel analysis is the total mass of dust that escapes

the refinery baghouse in a year, Mra. This value is calculated in the material flow model, and

values of 3.31E+06 g and 3.08E+06 g were calculated for the reverberatory and converter,

respectively.

The surface-to-mass ratios of various objects (spheres) were examined in estimating values for

this parameter for copper. Copper objects are assumed to have a density of 9.0 g/cm3

. Values for

various copper objects ranges from approximately 0.01 cm2/g for large-radius spheres, wire, and

bar stock, up to approximately 2.2 for small radius spheres and thin sheets and pipes. 

Data are not available to provide an adequate basis for choosing a “best estimate” from this range

of values. Using professional judgement and these theoretical data, the value of the parameter

SM for recycled copper scrap is best described by a loguniform distribution having a minimum

of 0.2 cm2/g and a maximum of 2.0 cm2/g. The minimum value is characteristic of heavy wire

having a radius of 0.5 cm. The maximum value is characteristic of pipes and sheets having a

thickness of 0.05 cm. The range for copper is representative of wire, pipes, and sheets of various

sizes with residual radioactivity on one side only. A wide variety of copper and copper alloy
Evaluation of Copper Section 5

NUREG-1640 5-26

(brass and bronze) objects commonly found at nuclear facilities have surface-to-mass values that

fall within this range. 

This range can be compared to an estimate from a studies similar to this one. O’Donnell (1978)

suggested a generic value of 0.6 cm2/g as representative of Number 2 copper wire, and

O’Donnell’s calculations are based on a reference copper object with a surface-to-mass ratio of

0.45cm2/g. 

'RVH)DFWRUVIRU5HF\FOHDQG'LVSRVDORI&RSSHU6FUDS

This analysis of recycled cleared copper scrap includes 23 separate scenarios evaluated for 85

radionuclides. Figure 5-2 shows which scenarios describe the critical groups and for how many

radionuclides. There are six scenarios which have the highest dose factor for at least one

radionuclide. The largest number of radionuclides have critical groups described by scenarios

associated with transporting (47 radionuclides) or handling (1 radionuclide) unprocessed scrap. 

Individuals handling either reverberatory furnace, converter, or electrorefiner slag constitute the

critical group for 31 radionuclides. For four volatile radionuclides, the critical group consists of

individuals exposed to atmospheric releases from the refining process. Transporting baghouse

dust describes the critical group for one radionuclide. Only one radionuclide is limited by a

scenario associated with use of a consumer product made from refined copper. Table 5.5 lists the

mass-based critical-group dose factors for each radionuclide. Table 5.6 lists the corresponding

derived surficial dose factors for each radionuclide. Results for all 23 copper scenarios are

tabulated in Appendix G. 

The mean values of the critical-group dose factors for each radionuclide are listed in Table 5.5 as

the “critical-group dose factor.” These represent the dose to the average member of the critical

group exposed to radioactivity distributed throughout the mass of cleared copper (Bq/g or pCi/g). 

The circumstances of that exposure are described by the scenario indicated in the right hand

column. The 5th, 50th, and 95th percentiles listed for each radionuclide represent the underlying

distribution of dose factors calculated for each critical group. The range of values from the 5th to

the 95th percentile is the 90% confidence interval on the dose factor. That is, there is a 90%

certainty that the dose factor for the average member of the critical group lies within this interval. 

The confidence interval is a subjective measure of uncertainty in the dose factor that includes

estimates of the variability and uncertainty in the parameters used in each scenario.

The ratio of the 95th to the 5th percentile is a useful measure of the relative width of the 90%

confidence interval for comparison between scenarios. Smaller values of the 95/5 ratio indicate

less uncertainty than larger values. The scenarios with the smallest uncertainty are those with the

fewest number of exposure pathways and the least uncertainty in the parameters describing those

pathways. The scrap transportation scenario accounts for 47 of the 85 radionuclides. It has the

smallest uncertainty of all the critical group scenarios with a 95/5 ratio of about 2 for most
Section 5 Evaluation of Copper

5-27 NUREG-1640

Scrap Transport

Slag Handling

Refinery Atmospheric Release

Dust Transport

Scrap Handling

Small Metal Object Close to Body

47

31

1 1 1

4

0

5

10

15

20

25

30

35

40

45

50

Number of Radionuclides

Copper Critical Group Scenarios

Figure 5.2 Scenarios describing critical groups for copper recycle

radionuclides. The sources of uncertainty in this scenario are similar to those for the steel scrap

transportation scenario discussed in Section 4.9.

For all scenarios that take place subsequent to the initial transport of scrap, additional sources of

uncertainty are introduced and wider confidence intervals result. Scenarios that address handling

of scrap include uncertainty due to mixing with other scrap. They also include additional

exposure pathways - inhalation of resuspended dust and inadvertent ingestion under dusty

conditions. Scenarios that address handling and processing of refinery products such as

baghouse dust and refinery slag include additional uncertainty in how much of each radionuclide

is partitioned to these materials. For copper, this group of handling and processing scenarios

have 95/5 ratios that range from about 10 to about 20.
Evaluation of Copper Section 5

NUREG-1640 5-28

Table 5.5 Copper recycle critical-group dose factors—mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

H-3 5.6E-04 6.1E-05 4.1E-04 1.7E-03 2.1E-06 2.2E-07 1.5E-06 6.2E-06CU-ATMO-REVERAT-N

C-14 1.6E-02 1.7E-03 1.1E-02 5.1E-02 6.0E-05 6.4E-06 4.0E-05 1.9E-04CU-ATMO-REVERAT-N

Na-22 2.2E+02 1.4E+02 2.2E+02 3.1E+02 8.1E-01 5.1E-01 8.1E-01 1.1E+00CU-SCRP-TRANSPO-W

P-32 1.3E-01 8.2E-02 1.3E-01 1.8E-01 4.8E-04 3.0E-04 4.8E-04 6.8E-04CU-SCRP-TRANSPO-W

S-35 7.8E-04 1.7E-04 6.1E-04 2.0E-03 2.9E-06 6.1E-07 2.3E-06 7.2E-06CU-REVS-HANDLIN-W

Cl-36 5.2E-02 4.6E-03 3.4E-02 1.6E-01 1.9E-04 1.7E-05 1.3E-04 5.8E-04CU-ATMO-REVERAT-N

K-40 1.6E+01 1.0E+01 1.6E+01 2.3E+01 6.0E-02 3.8E-02 6.0E-02 8.4E-02CU-SCRP-TRANSPO-W

Ca-41 2.0E-03 3.3E-04 1.5E-03 5.2E-03 7.3E-06 1.2E-06 5.6E-06 1.9E-05CU-REVS-HANDLIN-W

Ca-45 5.1E-03 1.0E-03 3.8E-03 1.3E-02 1.9E-05 3.8E-06 1.4E-05 5.0E-05CU-REVS-HANDLIN-W

Cr-51 2.5E+00 1.6E+00 2.5E+00 3.4E+00 9.1E-03 5.8E-03 9.1E-03 1.3E-02CU-SCRP-TRANSPO-W

Mn-54 8.5E+01 5.4E+01 8.5E+01 1.2E+02 3.2E-01 2.0E-01 3.1E-01 4.4E-01CU-SCRP-TRANSPO-W

Fe-55 9.7E-04 1.9E-04 7.6E-04 2.5E-03 3.6E-06 7.1E-07 2.8E-06 9.2E-06CU-CNVS-HANDLIN-W

Co-57 3.8E+00 2.4E+00 3.8E+00 5.3E+00 1.4E-02 8.9E-03 1.4E-02 2.0E-02CU-SCRP-TRANSPO-W

Co-58 9.5E+01 6.1E+01 9.5E+01 1.3E+02 3.5E-01 2.2E-01 3.5E-01 4.9E-01CU-SCRP-TRANSPO-W

Fe-59 1.1E+02 7.3E+01 1.2E+02 1.6E+02 4.2E-01 2.7E-01 4.3E-01 5.9E-01CU-SCRP-TRANSPO-W

Ni-59 4.2E-04 1.0E-04 3.3E-04 9.8E-04 1.6E-06 3.8E-07 1.2E-06 3.6E-06CU-CNVS-HANDLIN-W

Co-60 2.5E+02 1.6E+02 2.5E+02 3.6E+02 9.4E-01 5.9E-01 9.4E-01 1.3E+00CU-SCRP-TRANSPO-W

Ni-63 1.1E-03 2.6E-04 8.8E-04 3.0E-03 4.2E-06 9.7E-07 3.3E-06 1.1E-05CU-CNVS-HANDLIN-W

Zn-65 7.8E+01 2.2E+01 6.4E+01 1.9E+02 2.9E-01 8.1E-02 2.4E-01 6.9E-01CU-CNVD-TRANSPO-W

Cu-67 2.1E+00 1.0E+00 1.9E+00 3.6E+00 7.7E-03 3.7E-03 7.2E-03 1.3E-02CU-SCRP-TRANSPO-W

Se-75 2.4E+01 1.6E+01 2.5E+01 3.4E+01 9.1E-02 5.7E-02 9.1E-02 1.3E-01CU-SCRP-TRANSPO-W

Sr-85 4.7E+01 3.0E+01 4.7E+01 6.6E+01 1.7E-01 1.1E-01 1.7E-01 2.4E-01CU-SCRP-TRANSPO-W

Sr-89 1.2E-01 7.4E-02 1.2E-01 1.6E-01 4.3E-04 2.8E-04 4.3E-04 6.0E-04CU-SCRP-TRANSPO-W

Sr-90 4.3E-01 1.0E-01 3.0E-01 1.2E+00 1.6E-03 3.8E-04 1.1E-03 4.4E-03CU-ELRS-HANDLIN-W

Y-91 3.5E-01 2.2E-01 3.5E-01 4.8E-01 1.3E-03 8.2E-04 1.3E-03 1.8E-03CU-SCRP-TRANSPO-W

Mo-93 1.1E-02 1.6E-03 8.6E-03 3.1E-02 4.1E-05 6.0E-06 3.2E-05 1.1E-04CU-REVM-SMOBJCT-N

Nb-93m 5.9E-03 1.5E-03 4.7E-03 1.4E-02 2.2E-05 5.5E-06 1.7E-05 5.1E-05CU-CNVS-HANDLIN-W

Nb-94 1.6E+02 1.0E+02 1.6E+02 2.3E+02 6.1E-01 3.8E-01 6.0E-01 8.5E-01CU-SCRP-TRANSPO-W

Nb-95 7.2E+01 4.6E+01 7.3E+01 1.0E+02 2.7E-01 1.7E-01 2.7E-01 3.7E-01CU-SCRP-TRANSPO-W

Zr-95 7.2E+01 4.6E+01 7.2E+01 1.0E+02 2.7E-01 1.7E-01 2.7E-01 3.7E-01CU-SCRP-TRANSPO-W

Tc-99 2.9E-03 7.0E-04 2.2E-03 7.0E-03 1.1E-05 2.6E-06 8.3E-06 2.6E-05CU-CNVS-HANDLIN-W

Ru-103 4.6E+01 2.9E+01 4.7E+01 6.5E+01 1.7E-01 1.1E-01 1.7E-01 2.4E-01CU-SCRP-TRANSPO-W

Ru-106 2.1E+01 1.3E+01 2.1E+01 2.9E+01 7.6E-02 4.8E-02 7.6E-02 1.1E-01CU-SCRP-TRANSPO-W

Ag-108m 1.6E+02 1.0E+02 1.6E+02 2.3E+02 6.0E-01 3.8E-01 6.0E-01 8.4E-01CU-SCRP-TRANSPO-W

Cd-109 2.6E-02 6.2E-03 2.0E-02 6.4E-02 9.5E-05 2.3E-05 7.5E-05 2.4E-04CU-ELRS-HANDLIN-W
Section 5 Evaluation of Copper

Table 5.5 Copper recycle critical-group dose factors—mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

5-29 NUREG-1640

Ag-110m 2.8E+02 1.8E+02 2.8E+02 4.0E+02 1.0E+00 6.6E-01 1.0E+00 1.5E+00CU-SCRP-TRANSPO-W

Sb-124 1.8E+02 1.2E+02 1.8E+02 2.5E+02 6.7E-01 4.3E-01 6.7E-01 9.4E-01CU-SCRP-TRANSPO-W

I-125 6.5E-02 4.2E-02 6.5E-02 9.1E-02 2.4E-04 1.5E-04 2.4E-04 3.4E-04CU-SCRP-TRANSPO-W

Sb-125 4.1E+01 2.6E+01 4.1E+01 5.7E+01 1.5E-01 9.5E-02 1.5E-01 2.1E-01CU-SCRP-TRANSPO-W

I-129 4.4E-01 4.4E-02 3.1E-01 1.3E+00 1.6E-03 1.6E-04 1.2E-03 4.7E-03CU-ATMO-REVERAT-N

I-131 2.5E+01 1.5E+01 2.5E+01 3.6E+01 9.3E-02 5.5E-02 9.1E-02 1.3E-01CU-SCRP-TRANSPO-W

Ba-133 2.8E+01 1.8E+01 2.8E+01 3.9E+01 1.0E-01 6.5E-02 1.0E-01 1.4E-01CU-SCRP-TRANSPO-W

Cs-134 1.6E+02 1.0E+02 1.6E+02 2.2E+02 5.9E-01 3.7E-01 5.9E-01 8.3E-01CU-SCRP-TRANSPO-W

Cs-137 6.2E+01 3.9E+01 6.2E+01 8.6E+01 2.3E-01 1.4E-01 2.3E-01 3.2E-01CU-SCRP-TRANSPO-W

Ce-141 2.7E+00 1.7E+00 2.7E+00 3.8E+00 1.0E-02 6.4E-03 1.0E-02 1.4E-02CU-SCRP-TRANSPO-W

Ce-144 3.3E+00 2.1E+00 3.3E+00 4.6E+00 1.2E-02 7.7E-03 1.2E-02 1.7E-02CU-SCRP-TRANSPO-W

Pm-147 6.8E-03 1.5E-03 5.2E-03 1.7E-02 2.5E-05 5.5E-06 1.9E-05 6.2E-05CU-REVS-HANDLIN-W

Eu-152 1.1E+02 7.0E+01 1.1E+02 1.6E+02 4.1E-01 2.6E-01 4.1E-01 5.8E-01CU-SCRP-TRANSPO-W

Eu-154 1.2E+02 7.6E+01 1.2E+02 1.7E+02 4.5E-01 2.8E-01 4.5E-01 6.3E-01CU-SCRP-TRANSPO-W

Eu-155 1.1E+00 6.7E-01 1.1E+00 1.5E+00 3.9E-03 2.5E-03 3.9E-03 5.5E-03CU-SCRP-TRANSPO-W

Re-186 2.5E-01 1.3E-01 2.4E-01 3.9E-01 9.2E-04 5.0E-04 8.7E-04 1.4E-03CU-SCRP-TRANSPO-W

Ir-192 7.1E+01 4.5E+01 7.1E+01 9.9E+01 2.6E-01 1.7E-01 2.6E-01 3.7E-01CU-SCRP-TRANSPO-W

Pb-210 7.7E-01 2.8E+00 9.2E+00 9.2E+00 1.4E-02 2.8E-03 1.0E-02 3.4E-02CU-ELRS-HANDLIN-W

Po-210 2.0E-01 7.7E-01 2.6E+00 2.6E+00 3.9E-03 7.6E-04 2.8E-03 9.7E-03CU-ELRS-HANDLIN-W

Bi-210 3.1E-02 1.7E-02 3.0E-02 4.7E-02 1.2E-04 6.4E-05 1.1E-04 1.7E-04CU-SCRP-TRANSPO-W

Rn-222 8.6E+01 4.6E+01 8.2E+01 1.3E+02 3.2E-01 1.7E-01 3.0E-01 5.0E-01CU-SCRP-TRANSPO-W

Ra-223 1.8E+01 1.1E+01 1.8E+01 2.6E+01 6.7E-02 4.1E-02 6.6E-02 9.5E-02CU-SCRP-TRANSPO-W

Ra-224 6.1E+01 3.3E+01 5.8E+01 9.7E+01 2.3E-01 1.2E-01 2.2E-01 3.6E-01CU-SCRP-TRANSPO-W

Ac-225 1.4E+01 8.6E+00 1.4E+01 2.0E+01 5.3E-02 3.2E-02 5.1E-02 7.5E-02CU-SCRP-TRANSPO-W

Ra-225 4.7E-01 1.3E-01 4.2E-01 9.5E-01 1.7E-03 4.9E-04 1.5E-03 3.5E-03CU-SCRP-HANDLIN-W

Ra-226 1.7E+02 1.1E+02 1.7E+02 2.4E+02 6.4E-01 4.0E-01 6.4E-01 9.0E-01CU-SCRP-TRANSPO-W

Ac-227 2.6E+02 5.1E+01 2.0E+02 6.5E+02 9.7E-01 1.9E-01 7.6E-01 2.4E+00CU-REVS-HANDLIN-W

Th-227 5.9E+00 3.7E+00 5.8E+00 8.2E+00 2.2E-02 1.4E-02 2.2E-02 3.0E-02CU-SCRP-TRANSPO-W

Th-228 1.3E+02 8.0E+01 1.3E+02 1.8E+02 4.7E-01 3.0E-01 4.7E-01 6.6E-01CU-SCRP-TRANSPO-W

Ra-228 8.4E+01 5.3E+01 8.4E+01 1.2E+02 3.1E-01 2.0E-01 3.1E-01 4.3E-01CU-SCRP-TRANSPO-W

Th-229 3.3E+02 6.2E+01 2.5E+02 9.3E+02 1.2E+00 2.3E-01 9.2E-01 3.4E+00CU-REVS-HANDLIN-W

Th-230 5.0E+01 1.0E+01 3.6E+01 1.4E+02 1.9E-01 3.8E-02 1.3E-01 5.1E-01CU-REVS-HANDLIN-W

Pa-231 1.8E+02 3.3E+01 1.4E+02 4.4E+02 6.7E-01 1.2E-01 5.1E-01 1.6E+00CU-REVS-HANDLIN-W

Th-231 1.5E-02 3.3E-03 1.1E-02 3.8E-02 5.6E-05 1.2E-05 4.1E-05 1.4E-04CU-SCRP-TRANSPO-W

Th-232 2.2E+02 4.0E+01 1.6E+02 6.1E+02 8.3E-01 1.5E-01 6.1E-01 2.3E+00CU-REVS-HANDLIN-W
Evaluation of Copper Section 5

Table 5.5 Copper recycle critical-group dose factors—mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

NUREG-1640 5-30

Pa-233 1.3E+01 8.4E+00 1.3E+01 1.8E+01 4.9E-02 3.1E-02 4.9E-02 6.8E-02CU-SCRP-TRANSPO-W

U-233 2.5E+01 4.8E+00 2.0E+01 6.2E+01 9.3E-02 1.8E-02 7.2E-02 2.3E-01CU-REVS-HANDLIN-W

Th-234 7.3E-01 4.6E-01 7.3E-01 1.0E+00 2.7E-03 1.7E-03 2.7E-03 3.8E-03CU-SCRP-TRANSPO-W

U-234 2.5E+01 4.3E+00 1.9E+01 6.6E+01 9.2E-02 1.6E-02 7.0E-02 2.5E-01CU-REVS-HANDLIN-W

U-235 2.5E+01 5.7E+00 1.9E+01 6.2E+01 9.2E-02 2.1E-02 7.2E-02 2.3E-01CU-REVS-HANDLIN-W

Np-237 1.1E+02 2.1E+01 8.3E+01 3.2E+02 4.1E-01 7.9E-02 3.1E-01 1.2E+00CU-REVS-HANDLIN-W

Pu-238 5.5E+01 9.7E+00 4.1E+01 1.5E+02 2.0E-01 3.6E-02 1.5E-01 5.7E-01CU-REVS-HANDLIN-W

U-238 2.3E+01 4.0E+00 1.6E+01 6.4E+01 8.5E-02 1.5E-02 5.9E-02 2.4E-01CU-REVS-HANDLIN-W

Pu-239 5.8E+01 1.0E+01 4.4E+01 1.5E+02 2.2E-01 3.8E-02 1.6E-01 5.6E-01CU-REVS-HANDLIN-W

Pu-240 5.7E+01 1.2E+01 4.2E+01 1.6E+02 2.1E-01 4.6E-02 1.5E-01 5.8E-01CU-REVS-HANDLIN-W

Pu-241 9.4E-01 1.8E-01 7.0E-01 2.6E+00 3.5E-03 6.5E-04 2.6E-03 9.7E-03CU-REVS-HANDLIN-W

Am-241 9.0E+01 1.8E+01 6.7E+01 2.4E+02 3.3E-01 6.7E-02 2.5E-01 8.9E-01CU-REVS-HANDLIN-W

Cm-242 3.0E+00 6.3E-01 2.3E+00 7.6E+00 1.1E-02 2.3E-03 8.6E-03 2.8E-02CU-REVS-HANDLIN-W

Pu-242 5.4E+01 9.7E+00 4.3E+01 1.2E+02 2.0E-01 3.6E-02 1.6E-01 4.6E-01CU-REVS-HANDLIN-W

Cm-244 4.9E+01 9.8E+00 3.7E+01 1.3E+02 1.8E-01 3.6E-02 1.4E-01 4.7E-01CU-REVS-HANDLIN-W
Section 5 Evaluation of Copper

5-31 NUREG-1640

Table 5.6 Copper recycle critical-group dose factors—surficial

(μSv/y per Bq/cm2

) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

H-3 4.8E-04 4.5E-05 3.3E-04 1.4E-03 1.8E-06 1.7E-07 1.2E-06 5.0E-06CU-ATMO-REVERAT-N

C-14 1.4E-02 1.3E-03 8.4E-03 4.6E-02 5.1E-05 4.6E-06 3.1E-05 1.7E-04CU-ATMO-REVERAT-N

Na-22 1.9E+02 9.3E+01 1.8E+02 3.2E+02 7.0E-01 3.4E-01 6.5E-01 1.2E+00CU-SCRP-TRANSPO-W

P-32 1.1E-01 5.4E-02 1.0E-01 1.9E-01 4.1E-04 2.0E-04 3.9E-04 6.9E-04CU-SCRP-TRANSPO-W

S-35 6.6E-04 1.3E-04 5.0E-04 1.8E-03 2.5E-06 4.7E-07 1.8E-06 6.5E-06CU-REVS-HANDLIN-W

Cl-36 4.4E-02 4.5E-03 2.8E-02 1.3E-01 1.6E-04 1.7E-05 1.1E-04 4.9E-04CU-ATMO-REVERAT-N

K-40 1.4E+01 6.9E+00 1.3E+01 2.4E+01 5.1E-02 2.5E-02 4.8E-02 8.9E-02CU-SCRP-TRANSPO-W

Ca-41 1.7E-03 2.5E-04 1.2E-03 4.7E-03 6.2E-06 9.1E-07 4.4E-06 1.7E-05CU-REVS-HANDLIN-W

Ca-45 4.3E-03 7.0E-04 3.1E-03 1.2E-02 1.6E-05 2.6E-06 1.1E-05 4.6E-05CU-REVS-HANDLIN-W

Cr-51 2.1E+00 1.0E+00 2.0E+00 3.5E+00 7.8E-03 3.8E-03 7.3E-03 1.3E-02CU-SCRP-TRANSPO-W

Mn-54 7.3E+01 3.6E+01 6.8E+01 1.3E+02 2.7E-01 1.3E-01 2.5E-01 4.6E-01CU-SCRP-TRANSPO-W

Fe-55 8.3E-04 1.5E-04 6.1E-04 2.2E-03 3.1E-06 5.6E-07 2.3E-06 8.1E-06CU-CNVS-HANDLIN-W

Co-57 3.3E+00 1.6E+00 3.0E+00 5.6E+00 1.2E-02 6.0E-03 1.1E-02 2.1E-02CU-SCRP-TRANSPO-W

Co-58 8.1E+01 4.0E+01 7.5E+01 1.4E+02 3.0E-01 1.5E-01 2.8E-01 5.1E-01CU-SCRP-TRANSPO-W

Fe-59 9.8E+01 4.8E+01 9.1E+01 1.7E+02 3.6E-01 1.8E-01 3.4E-01 6.1E-01CU-SCRP-TRANSPO-W

Ni-59 3.6E-04 8.2E-05 2.8E-04 9.0E-04 1.3E-06 3.0E-07 1.0E-06 3.3E-06CU-CNVS-HANDLIN-W

Co-60 2.2E+02 1.1E+02 2.0E+02 3.8E+02 8.1E-01 4.0E-01 7.5E-01 1.4E+00CU-SCRP-TRANSPO-W

Ni-63 9.7E-04 1.8E-04 7.5E-04 2.6E-03 3.6E-06 6.6E-07 2.8E-06 9.5E-06CU-CNVS-HANDLIN-W

Zn-65 6.7E+01 1.5E+01 5.0E+01 1.6E+02 2.5E-01 5.7E-02 1.9E-01 6.0E-01CU-CNVD-TRANSPO-W

Cu-67 1.8E+00 6.8E-01 1.6E+00 3.3E+00 6.5E-03 2.5E-03 5.9E-03 1.2E-02CU-SCRP-TRANSPO-W

Se-75 2.1E+01 1.0E+01 1.9E+01 3.6E+01 7.7E-02 3.8E-02 7.2E-02 1.3E-01CU-SCRP-TRANSPO-W

Sr-85 4.0E+01 2.0E+01 3.7E+01 6.9E+01 1.5E-01 7.3E-02 1.4E-01 2.5E-01CU-SCRP-TRANSPO-W

Sr-89 9.9E-02 4.9E-02 9.2E-02 1.7E-01 3.7E-04 1.8E-04 3.4E-04 6.2E-04CU-SCRP-TRANSPO-W

Sr-90 3.7E-01 7.2E-02 2.5E-01 1.1E+00 1.4E-03 2.7E-04 9.2E-04 4.1E-03CU-ELRS-HANDLIN-W

Y-91 3.0E-01 1.5E-01 2.7E-01 5.0E-01 1.1E-03 5.4E-04 1.0E-03 1.9E-03CU-SCRP-TRANSPO-W

Mo-93 9.5E-03 1.2E-03 6.9E-03 2.6E-02 3.5E-05 4.3E-06 2.6E-05 9.6E-05CU-REVM-SMOBJCT-N

Nb-93m 5.0E-03 1.1E-03 3.9E-03 1.3E-02 1.9E-05 3.9E-06 1.4E-05 4.8E-05CU-CNVS-HANDLIN-W

Nb-94 1.4E+02 6.9E+01 1.3E+02 2.4E+02 5.2E-01 2.6E-01 4.8E-01 8.9E-01CU-SCRP-TRANSPO-W

Nb-95 6.2E+01 3.0E+01 5.8E+01 1.0E+02 2.3E-01 1.1E-01 2.1E-01 3.9E-01CU-SCRP-TRANSPO-W

Zr-95 6.2E+01 3.0E+01 5.7E+01 1.1E+02 2.3E-01 1.1E-01 2.1E-01 3.9E-01CU-SCRP-TRANSPO-W

Tc-99 2.5E-03 4.7E-04 1.9E-03 6.4E-03 9.1E-06 1.7E-06 6.9E-06 2.4E-05CU-CNVS-HANDLIN-W

Ru-103 4.0E+01 1.9E+01 3.7E+01 6.7E+01 1.5E-01 7.2E-02 1.4E-01 2.5E-01CU-SCRP-TRANSPO-W

Ru-106 1.8E+01 8.7E+00 1.6E+01 3.0E+01 6.5E-02 3.2E-02 6.1E-02 1.1E-01CU-SCRP-TRANSPO-W

Ag-108m 1.4E+02 6.9E+01 1.3E+02 2.4E+02 5.1E-01 2.5E-01 4.8E-01 8.9E-01CU-SCRP-TRANSPO-W

Cd-109 2.2E-02 4.6E-03 1.6E-02 5.7E-02 8.2E-05 1.7E-05 6.1E-05 2.1E-04CU-ELRS-HANDLIN-W
Evaluation of Copper Section 5

Table 5.6 Copper recycle critical-group dose factors—surficial

(μSv/y per Bq/cm2

) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

NUREG-1640 5-32

Ag-110m 2.4E+02 1.2E+02 2.2E+02 4.2E+02 8.9E-01 4.4E-01 8.3E-01 1.5E+00CU-SCRP-TRANSPO-W

Sb-124 1.5E+02 7.6E+01 1.4E+02 2.6E+02 5.7E-01 2.8E-01 5.3E-01 9.7E-01CU-SCRP-TRANSPO-W

I-125 5.6E-02 2.7E-02 5.2E-02 9.5E-02 2.1E-04 1.0E-04 1.9E-04 3.5E-04CU-SCRP-TRANSPO-W

Sb-125 3.5E+01 1.7E+01 3.2E+01 6.0E+01 1.3E-01 6.4E-02 1.2E-01 2.2E-01CU-SCRP-TRANSPO-W

I-129 3.7E-01 4.0E-02 2.6E-01 1.1E+00 1.4E-03 1.5E-04 9.6E-04 4.1E-03CU-ATMO-REVERAT-N

I-131 2.1E+01 1.0E+01 2.0E+01 3.6E+01 7.9E-02 3.7E-02 7.5E-02 1.3E-01CU-SCRP-TRANSPO-W

Ba-133 2.4E+01 1.2E+01 2.2E+01 4.1E+01 8.8E-02 4.4E-02 8.2E-02 1.5E-01CU-SCRP-TRANSPO-W

Cs-134 1.4E+02 6.8E+01 1.3E+02 2.4E+02 5.1E-01 2.5E-01 4.7E-01 8.7E-01CU-SCRP-TRANSPO-W

Cs-137 5.3E+01 2.6E+01 4.9E+01 9.1E+01 2.0E-01 9.7E-02 1.8E-01 3.4E-01CU-SCRP-TRANSPO-W

Ce-141 2.3E+00 1.1E+00 2.2E+00 3.9E+00 8.6E-03 4.2E-03 8.0E-03 1.4E-02CU-SCRP-TRANSPO-W

Ce-144 2.8E+00 1.4E+00 2.6E+00 4.8E+00 1.0E-02 5.2E-03 9.7E-03 1.8E-02CU-SCRP-TRANSPO-W

Pm-147 5.8E-03 1.2E-03 4.2E-03 1.7E-02 2.1E-05 4.4E-06 1.6E-05 6.2E-05CU-REVS-HANDLIN-W

Eu-152 9.5E+01 4.7E+01 8.9E+01 1.6E+02 3.5E-01 1.7E-01 3.3E-01 6.1E-01CU-SCRP-TRANSPO-W

Eu-154 1.0E+02 5.1E+01 9.7E+01 1.8E+02 3.8E-01 1.9E-01 3.6E-01 6.6E-01CU-SCRP-TRANSPO-W

Eu-155 9.1E-01 4.5E-01 8.5E-01 1.6E+00 3.4E-03 1.7E-03 3.1E-03 5.8E-03CU-SCRP-TRANSPO-W

Re-186 2.1E-01 9.0E-02 2.0E-01 3.6E-01 7.8E-04 3.3E-04 7.4E-04 1.3E-03CU-SCRP-TRANSPO-W

Ir-192 6.1E+01 3.0E+01 5.6E+01 1.0E+02 2.2E-01 1.1E-01 2.1E-01 3.8E-01CU-SCRP-TRANSPO-W

Pb-210 5.9E-01 2.3E+00 8.8E+00 8.8E+00 1.2E-02 2.2E-03 8.4E-03 3.3E-02CU-ELRS-HANDLIN-W

Po-210 1.5E-01 6.6E-01 2.5E+00 2.5E+00 3.3E-03 5.7E-04 2.4E-03 9.2E-03CU-ELRS-HANDLIN-W

Bi-210 2.7E-02 1.2E-02 2.5E-02 4.5E-02 9.8E-05 4.4E-05 9.4E-05 1.7E-04CU-SCRP-TRANSPO-W

Rn-222 7.3E+01 3.1E+01 6.9E+01 1.3E+02 2.7E-01 1.2E-01 2.6E-01 4.6E-01CU-SCRP-TRANSPO-W

Ra-223 1.5E+01 7.4E+00 1.5E+01 2.6E+01 5.7E-02 2.7E-02 5.4E-02 9.5E-02CU-SCRP-TRANSPO-W

Ra-224 5.2E+01 2.2E+01 4.9E+01 9.0E+01 1.9E-01 8.2E-02 1.8E-01 3.3E-01CU-SCRP-TRANSPO-W

Ac-225 1.2E+01 5.7E+00 1.1E+01 2.0E+01 4.5E-02 2.1E-02 4.2E-02 7.4E-02CU-SCRP-TRANSPO-W

Ra-225 4.0E-01 9.9E-02 3.4E-01 9.0E-01 1.5E-03 3.7E-04 1.3E-03 3.3E-03CU-SCRP-HANDLIN-W

Ra-226 1.5E+02 7.4E+01 1.4E+02 2.6E+02 5.5E-01 2.7E-01 5.1E-01 9.5E-01CU-SCRP-TRANSPO-W

Ac-227 2.3E+02 3.9E+01 1.7E+02 6.6E+02 8.4E-01 1.5E-01 6.1E-01 2.4E+00CU-REVS-HANDLIN-W

Th-227 5.0E+00 2.4E+00 4.7E+00 8.4E+00 1.9E-02 9.0E-03 1.7E-02 3.1E-02CU-SCRP-TRANSPO-W

Th-228 1.1E+02 5.4E+01 1.0E+02 1.9E+02 4.0E-01 2.0E-01 3.7E-01 6.9E-01CU-SCRP-TRANSPO-W

Ra-228 7.2E+01 3.6E+01 6.7E+01 1.2E+02 2.7E-01 1.3E-01 2.5E-01 4.6E-01CU-SCRP-TRANSPO-W

Th-229 2.9E+02 5.2E+01 2.0E+02 8.1E+02 1.1E+00 1.9E-01 7.3E-01 3.0E+00CU-REVS-HANDLIN-W

Th-230 4.3E+01 7.8E+00 2.9E+01 1.3E+02 1.6E-01 2.9E-02 1.1E-01 4.7E-01CU-REVS-HANDLIN-W

Pa-231 1.6E+02 2.7E+01 1.1E+02 4.0E+02 5.7E-01 1.0E-01 3.9E-01 1.5E+00CU-REVS-HANDLIN-W

Th-231 1.3E-02 2.3E-03 9.3E-03 3.5E-02 4.7E-05 8.7E-06 3.4E-05 1.3E-04CU-SCRP-TRANSPO-W

Th-232 1.9E+02 3.1E+01 1.4E+02 5.1E+02 7.0E-01 1.1E-01 5.1E-01 1.9E+00CU-REVS-HANDLIN-W
Section 5 Evaluation of Copper

Table 5.6 Copper recycle critical-group dose factors—surficial

(μSv/y per Bq/cm2

) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

5-33 NUREG-1640

Pa-233 1.1E+01 5.5E+00 1.1E+01 1.9E+01 4.2E-02 2.0E-02 3.9E-02 7.0E-02CU-SCRP-TRANSPO-W

U-233 2.1E+01 4.0E+00 1.6E+01 5.8E+01 7.9E-02 1.5E-02 5.8E-02 2.2E-01CU-REVS-HANDLIN-W

Th-234 6.2E-01 3.0E-01 5.8E-01 1.0E+00 2.3E-03 1.1E-03 2.2E-03 3.9E-03CU-SCRP-TRANSPO-W

U-234 2.1E+01 3.4E+00 1.5E+01 6.1E+01 7.9E-02 1.2E-02 5.5E-02 2.3E-01CU-REVS-HANDLIN-W

U-235 2.1E+01 4.1E+00 1.6E+01 6.1E+01 7.9E-02 1.5E-02 6.0E-02 2.3E-01CU-REVS-HANDLIN-W

Np-237 9.4E+01 1.6E+01 6.6E+01 2.7E+02 3.5E-01 5.9E-02 2.4E-01 1.0E+00CU-REVS-HANDLIN-W

Pu-238 4.8E+01 7.1E+00 3.4E+01 1.3E+02 1.8E-01 2.6E-02 1.2E-01 4.9E-01CU-REVS-HANDLIN-W

U-238 2.0E+01 3.0E+00 1.4E+01 5.8E+01 7.3E-02 1.1E-02 5.1E-02 2.1E-01CU-REVS-HANDLIN-W

Pu-239 5.0E+01 8.4E+00 3.6E+01 1.4E+02 1.9E-01 3.1E-02 1.3E-01 5.2E-01CU-REVS-HANDLIN-W

Pu-240 4.9E+01 9.0E+00 3.6E+01 1.3E+02 1.8E-01 3.3E-02 1.3E-01 4.9E-01CU-REVS-HANDLIN-W

Pu-241 8.1E-01 1.3E-01 5.7E-01 2.5E+00 3.0E-03 4.7E-04 2.1E-03 9.3E-03CU-REVS-HANDLIN-W

Am-241 7.8E+01 1.4E+01 5.5E+01 2.1E+02 2.9E-01 5.1E-02 2.0E-01 7.9E-01CU-REVS-HANDLIN-W

Cm-242 2.5E+00 5.0E-01 1.9E+00 6.9E+00 9.4E-03 1.8E-03 6.9E-03 2.6E-02CU-REVS-HANDLIN-W

Pu-242 4.6E+01 8.0E+00 3.2E+01 1.2E+02 1.7E-01 2.9E-02 1.2E-01 4.3E-01CU-REVS-HANDLIN-W

Cm-244 4.2E+01 7.4E+00 3.1E+01 1.1E+02 1.5E-01 2.7E-02 1.1E-01 4.2E-01CU-REVS-HANDLIN-W

Greater uncertainty is associated with scenarios that involve multiple exposure pathways and

complex submodels. Four volatile radionuclides (H-3, C-14, Cl-36, and I-129) have critical

groups consisting of individuals living in the vicinity of a copper refinery and exposed to

atmospheric releases. This scenario includes an atmospheric dispersion model and pathways for

ingestion, inhalation, and external exposure, each of which contributes to uncertainty in the dose

factor. For copper, radionuclides limited by the atmospheric release scenario have 95/5 ratios

that range from about 30 to about 35. Most of this uncertainty is due to the atmospheric

dispersion model but additional contributions from partitioning to refinery off-gas and

uncertainties in ingestion dose are nuclide-dependent.

The mean values of the derived surficial dose factors for each radionuclide in Table 5.6 represent

the dose to the average member of the critical group exposed to radioactivity initially distributed

over the surface cleared copper scrap (Bq/cm2

 or pCi/cm2). Derived surficial dose factors are

calculated from mass-based dose factors by use of a surface-to-mass ratio, SM, appropriate for

typical copper objects available for clearance. The use of this parameter to derive surficial dose

factors is described in Section 4.7.

The calculation of derived surficial dose factors is probabilistic. The parameter SM is

represented by a distribution of values that incorporate the variability and uncertainty in the

surface-to-mass ratio of typical copper objects available for clearance. This additional source of

uncertainty results in wider confidence intervals for the surficial dose factors than for the mass-
Evaluation of Copper Section 5

NUREG-1640 5-34

based dose factors from which they are derived. The relative importance of this additional

uncertainty depends on the scenario. For scenarios with the narrowest confidence intervals, the

added uncertainty can contribute as much as an additional 50% to the width of the confidence

interval. The mass-based dose factor for the scrap transportation scenario has a 95/5 ratio of

about 2 for most radionuclides. The corresponding derived surficial dose factors have a 95/5

ratio of about 3. The added uncertainty in surface-to-mass ratio has a relatively smaller impact

on the confidence interval for scenarios with larger uncertainties, contributing an additional 10%

to 30%.
Section 6 Evaluation of Aluminum

6-1 NUREG-1640

Seventeen potential exposure scenarios for cleared aluminum scrap that are realistically based on

current American industries are evaluated in this section. As in the steel evaluation, scenario

categories include handling and processing, storage, transportation, product use, and disposal. A

radionuclide-specific, probabilistic dose factor distribution was calculated for the members of all

exposed groups, and dose factors for an average member of each critical group was calculated in the

same manner as for steel recycle. The mean dose factor for each critical group is reported in

normalized units of μSv/y per Bq/g scrap (mrem/y per pCi/g) and μSv/y per Bq/cm2 scrap (mrem/y per

pCi/cm2 ) for each radionuclide. Dose factors at the 5th , 50th , and 95th percentiles are also reported.

Similar to steel and copper, the most common critical group consists of commercial truck drivers

carrying cleared aluminum scrap. Scenarios involving transport of scrap material resulted in critical

group designation for over half (52) of the 85 radionuclides in the analysis. Other scenarios

identifying critical groups for many radionuclides involve handling aluminum scrap material (17

radionuclides). Unlike the other metals evaluated, use of aluminum products identify critical groups

for several radionuclides. Use of aluminum cookware accounts for 11 critical groups, and use of a

generic, small metal object accounts for 2 critical groups. 

Mean critical-group dose factors range from a high of 6 μSv/y per Bq/g (0.02 mrem/y per pCi/g) for Ag110m to a low of 2E-06 μSv/y per Bq/g (7E-09 mrem/y per pCi/g) for H-3. The surficial mean criticalgroup dose factors range from 23 μSv/y per Bq/cm2 (Ag-110m) down to 7E-06 μSv/y per Bq/cm2 (H-3). 

 Scenarios involving scrap transport account for the highest critical-group dose factors. Seventy-eight

of the radionuclide-specific, mean dose factors for aluminum critical groups are 270 μSv/y per Bq/g or

lower (1 mrem/y per pCi/g). 

(9$/8$7,212)5(&<&/($1'',6326$/2)

$/80,1806&5$3

This section describes the technical evaluation of the recycle and disposal of aluminum scrap that

could be cleared from Nuclear Regulatory Commission (NRC) licensed facilities. Similar to

steel scrap (Section 4), the flow of cleared material was probabilistically modeled, distributions

of radionuclide concentrations in refined and disposed materials were calculated, and the mean

dose factors for each potentially exposed group were estimated.

,QWURGXFWLRQWR$QDO\VLV

The analysis process for potential exposures from aluminum recycle and disposal is essentially

the same as described previously for steel and copper. A material flow model specific to

aluminum scrap was developed, radionuclide concentrations were calculated, and scenario

evaluations were conducted. Besides the material flow model (and calculated concentrations in

refined and disposed materials), there are only minor differences between the steel and aluminum

scrap analyses. There are several minor scenario parameter differences and one additional

exposure scenario that is specific to recycled aluminum scrap (described in Section 6.6). 
Evaluation of Aluminum Section 6

NUREG-1640 6-2

Figure 6.1 Material flow for aluminum scrap

)ORZRI5HF\FOHGDQG'LVSRVHG$OXPLQXP6FUDS

The material flow model for aluminum represents the general processes that cleared material

would go through from the time it is cleared by a NRC licensed facility to the time of final

disposal. Similar to steel and copper, the aluminum material flow model is comprised of two

types of models: conceptual and mathematical. The conceptual model describes the aluminum

refining process and defines the limits of this analysis, while the mathematical model presents the

mathematical equations that implement the information presented in the conceptual model.

The material flow model is based on a literature review of the U.S. secondary aluminum industry. 

It is intended to provide a defensible basis for developing appropriate exposure scenarios. In

addition, the output of the material flow model provides key input to the dose calculations for

each scenario. This input consists of radionuclide-specific concentrations in recycle by-products,

in effluent, and in waste products of the refining process. Because of the number of scenarios

being analyzed and the differing times at which they occur, the mathematical model presented in

this section does not include radioactive decay. However, radioactive decay is taken into account

in the individual scenarios, in the same manner as in the analyses for steel and copper.
Section 6 Evaluation of Aluminum

1

Recycle/Reuse Literature Search Report, SAIC, 1994 scheduled to be published as NUREG/CR-5610

6-3 NUREG-1640

This section presents the conceptual model that describes the movement of aluminum scrap

through the normal refining process, beginning with the production of scrap, through refining,

manufacturing, product use, and ending with disposal. Figure 6.1 presents a schematic diagram

of the overall material flow conceptual model for aluminum. Both the mass and radioactivity

follow this flow model. There are several distinct steps or processes in the refining process. 

These are discussed in the following subsections.

6RXUFHVRI0DWHULDO

Similar to steel and copper, aluminum recyclers can be the general public (e.g., recycling

aluminum cans), industry (e.g., recycling aluminum siding), or manufacturers (e.g., scrap

produced during the manufacture of end products). 

There are three types of scrap metal used in the aluminum making industry: home, new, and old. 

Home scrap consists of unusable metal produced during the processing or fabrication of

aluminum into a form usable for manufacturing. Home scrap is usually high-grade metal with

very few impurities. Even though home scrap is produced at the refinery, it is still considered a

secondary metal because it is not the processed raw material. New scrap is produced during

manufacture of end products. New scrap also is high-grade metal with very few impurities. Old

scrap includes obsolete, worn out or broken products that have been used by the general public

or industry. Old scrap is usually low grade metal and the chemical composition is not wellknown. Therefore, it must first be sorted, sized, and classified. Recyclable scrap metal from the

nuclear industry is considered old scrap. A total of 3.19E+06 t (3.5 E+06 tons) of secondary

aluminum (scrap) was consumed in the U.S. in 1995, and almost half of that was old scrap

(USBM 1997). 

The main producer of the scrap assumed for this study is the nuclear industry (decommissioned

material from nuclear facilities), which consists mainly of commercial power plants, test and

research reactors, and industrial nuclear facilities. Other producers of such scrap include the

Department of Energy (DOE) weapons complex and the Department of Defense (DOD), which

would contribute scrap primarily from conventional weapons testing and army and navy test

reactors. Approximately 2.5E+02 t/y (2.75 E+02 ton/y) of potentially recyclable aluminum scrap

metal is generated each year by NRC licensed facilities. Increased dismantling and

decommissioning activities could result in up to 4.50E+03 t/y (5.0E+03 ton/y) of aluminum scrap

from these facilities for a limited number of years (NUREG/CR-56101

). 

Similar to the steel and copper analyses, cleared aluminum scrap is assumed to be mixed with a

single source of uncontaminated scrap.
Evaluation of Aluminum Section 6

NUREG-1640 6-4

7UDQVSRUWDWLRQDQG3URFHVVLQJ

Scrap aluminum cleared from a nuclear facility could be transported to a scrap dealer or

processor; this would most likely be done by a commercial company. Because not all scrap

aluminum would be suitable for recycle, some may be transported directly to a disposal site. In

all cases, transportation could occur either by truck or rail.

After scrap is processed at a scrap dealer, it is transported by either rail or truck to a refinery. 

Dross (refining slag), metal products, and dust also would be transported from the refinery to

manufacturers or processors by either truck, rail, or waterway.

$OXPLQXP0LOOV

There are five types of refineries and mills that use aluminum scrap as input: primary scrap

processors, secondary smelters, foundries, fabricators, and chemical plants. However, the

aluminum scrap produced at nuclear facilities would most likely enter a secondary smelter. 

Secondary smelters most commonly use an oil or gas-fired reverberatory furnace. Key modeling

parameter values for an aluminum secondary smelter are shown in Table 6.1.

Table 6.1 Key modeling assumptions for aluminum secondary smelter

Assumptions Value

End product and use sheet, plate, foil, ingot, rod, bar and wire

End use of the dust disposed of in a sanitary landfill 

Temperature inside furnace 650EC

Temperature inside the baghouse 190EC

Chemical form of elements entering baghouse oxides

Efficiency of baghouse 99.9%

Average size of a charge 50 t

Average number of charges per year for a single

refinery

5580

In 1996, secondary smelters consumed approximately 1.4E+6 t (1.5E+6 tons) of scrap (new +

used). The typical input material for this type of furnace is aluminum scrap and occasionally a

small amount of additives (silicon, titanium, and strontium rods). The capacity of a typical

reverberatory furnace is approximately 50 t (55 tons). No data were available at the time of this

analysis to determine the average number of charges per year for an aluminum refinery; the value

used for steel BOF refineries (5580 charges/y) was judged to be adequate for aluminum

references.
Section 6 Evaluation of Aluminum

6-5 NUREG-1640

The fumes that are generated during the refining of aluminum scrap are captured by the primary

exhaust hood and transported via a duct system to a baghouse. The baghouses used in the

refining of aluminum scrap are similar to those used in the iron and steel industry.1 Therefore,

the same parameters for the baghouse are used for the recycling of aluminum (e.g., temperature,

efficiency). Occasionally dirty aluminum scrap undergoes pretreatment to remove iron, oil, and

water. Pretreatment consists of crushing and/or drying (using an afterburner). The dust produced

during pretreatment is collected in the same baghouse as for the furnace. When the dust is

removed from the baghouse, it is tested for hazardous components to determine if it needs to be

handled as hazardous waste. About 99% of the dust produced during the recycling of aluminum

is not considered hazardous. Therefore, for this analysis the baghouse dust is considered to be

nonhazardous.

During the refining process, the original metal separates into four different end products: off-gas,

dust, dross, and metal (Figure 6.1). Both the mass and radioactivity partition into the different

end products. To account for this in the material flow modeling, partitioning factors for both

mass and elements were developed and are discussed in detail in Section 6.3.

Each of the end products undergoes a different process, use, and final disposal process. The offgas includes elements that are completely volatilized into stable gases or very fine particles

during refining and exit the refinery stack. Dust includes elements that are volatilized from the

furnace, form particulates when cooled, and are collected in baghouse filters. (The air pollution

control systems are not 100% efficient, and a small percentage of the dust is released into the

atmosphere with the off-gas.) 

Dross is not considered a hazardous waste, therefore, it can be recycled, reprocessed, or directly

disposed of. After dross is removed from the furnace and cooled, it is stored outdoors in piles at

the refinery until it is either used by the refinery or transported to a processor. Because of its

high metal content, dross can be fed back into the furnace as input material.

Manufacturing and processing converts dross and metal products created at the refineries and

mills into finished products. Manufacturing involves activities such as cutting and shaping the

metal. Processing of dross involves crushing and sizing. After a metal product or dross is

manufactured into a finished product, it must be transported and distributed to the general public

(i.e., end user). Facilities involved in the distribution of finished metal products include stores,

warehouses, and car lots. If it is not recycled on-site, dross is usually distributed and transported

directly from the refinery where it is produced or from the manufacturer where it is processed. 

3URGXFW8VH

Dross or finished metal products are used by the public for many applications. Aluminum metal

products are used in containers and packaging, building and construction, transportation,

electrical products, consumer durables, and machinery and equipment. Use of dross is similar to

that of iron and steel slag (e.g., roadbed, railroad ballast).
Evaluation of Aluminum Section 6

1

 Personal communication between Mary Anderson of SAIC and Jim Bopp of Alchem Aluminum, May 23, 1997.

NUREG-1640 6-6

'LVSRVDO

The ultimate endpoint for finished metal products, dross, and dust is disposal in a public sanitary

landfill (i.e., a Resource Conservation and Recovery Act [RCRA] Subtitle D landfill). The types

of objects that could end up in a public sanitary landfill include discarded end products, waste

from manufacturing, dross directly from the refinery, products made from dross, scrap not

suitable for recycle, and dust. 

0DVVDQG(OHPHQWDO3DUWLWLRQLQJ)DFWRUVIRU5HILQHU\2SHUDWLRQV

Partitioning of the radioactivity and mass present in scrap entering the refinery furnace is

modeled in order to estimate concentrations of radionuclides in various end products. 

Partitioning factors are defined as the estimated fraction of original radionuclide concentration or

mass entering the refinery furnace that would be present in various end products. As modeled in

this analysis, the mass of scrap metal entering a furnace during the refining process is

redistributed into the three immediate products: metal product, dross, and dust. Partitioning of

radioactivity to these products is also modeled, as well as for the off-gas leaving the refinery

stack. 

0DVV3DUWLWLRQLQJ)DFWRUV

Mass partitioning factors for aluminum were estimated using information obtained from industry

contacts for the metal product, dross, and dust. According to Alchem Aluminum,1

 40% to 90%

of the metal mass entering the furnace ends up in the metal product. If cleaner scrap (new scrap)

is used, the percent yield is close to 90%. However, if dross is used with the scrap as input, the

percent yield is closer to 40%. The cleared aluminum material being analyzed in this material

flow is assumed to be fairly clean and representative of new scrap. Therefore, a range of 40% to

90% is used as the distribution for the mass partitioning for metal product. Because the dust

produced during the recycling of aluminum scrap is not considered hazardous, a record of the

mass produced per charge is not typically kept by refineries. Between 0.5% and 2% of the

original mass entering the furnace is estimated to end up in the dust. The dirtier the scrap input,

the more dust is produced. There are very few additives used during the refining of aluminum

scrap, so the remaining fraction is assumed to be the mass partitioning for dross.

(OHPHQWDO3DUWLWLRQLQJ)DFWRUV

In order to simplify the material flow modeling, elements of concern were grouped according to

their elemental partitioning factors. It was assumed that there were no isotopic effects and that

all isotopes of a given element would behave identically.

The primary methods for removing impurities from the melt in the reverberatory furnace are

bubbling chlorine through the melt and/or using fluoride fluxes. Whether or not an element
Section 6 Evaluation of Aluminum

6-7 NUREG-1640

remains in the melt depends primarily on its propensity to form chlorides or fluorides. Calcium

is added to the melt to increase the formation of intermetallic compounds with cadmium, lead,

bismuth, and antimony. These compounds float to the top and are incorporated into the dross. In

addition to these factors, the chemical and physical properties of the elements in question were

also considered, particularly for those elements for which only limited data are available. Where

no direct estimates of partitioning were available, elemental partitioning factors were estimated

based on the behavior of chemically similar elements.

The elemental partitioning factor ranges determined for the aluminum material flow model are

intended to be representative of the expected behavior during melting in a typical domestic

aluminum reverberatory furnace. Both lack of knowledge about the behavior of elements during

the refining of aluminum and variability in refinery conditions contribute to uncertainty in the

estimates of elemental partitioning factors. In order to address this uncertainty, ranges for the

partitioning values were used, similar to the analyses for steel and copper.

During refining, elements could partition to one or both of the main melt components (i.e., the

dross and/or metal phases) or discharge from the furnace in the volatilized gas. Some of the

radionuclides that leave the furnace in the volatilized gas would remain in the vapor phase (offgas) and some would condense or coalesce into particulates (dust). Elements found in coarse

particulates would be captured by the baghouse filter. Some of the fine particles and species in

the vapor phase would escape in the off-gas exiting the stack. 

The furnace is assumed to be operating at an average temperature of about 650EC (1200EF). The

average temperature of the baghouse is assumed to be 190EC (375EF). It is assumed that the air

flowing through the baghouse is cooled to this temperature. The assumptions listed in Table 6.1

of this report are also used.

Table 6.2 shows the resulting elemental partitioning factor (EPF) ranges for each element. Note

that the partitioning factors for some elements (e.g., iodine) do not sum to 100%. This is due to

the use of ranges for partitioning factors. However, this is acceptable because only one material

is present in each exposure scenario, and a strict mass balance is not necessary.

0DWKHPDWLFDO0RGHOIRU)ORZRI5HF\FOHG$OXPLQXP6FUDS

This section presents the equations that represent the information discussed previously in Section

6.2 and 6.3 and are used to formulate the mathematical model. The equations estimate

radionuclide concentrations in refined aluminum and other co-products of refining. The

equations are entered into spreadsheets that have been organized and structured specifically for

this analysis. The calculated radionuclide concentrations in refined aluminum, dross (refinery

slag), refinery baghouse dust, and the amount of radioactivity released out the refinery stack are

used as input to the scenario analyses. 
Evaluation of Aluminum Section 6

NUREG-1640 6-8

0L[LQJRI&OHDUHG6FUDSDQG2WKHU6FUDS

There are only two processes by which the original concentration of each radionuclide in cleared

aluminum scrap can be potentially changed. The first can occur upon mixing with other scrap

metal prior to refining. This mixing is a radionuclide-independent process, so the radioactivity

concentration of all radionuclides is effected the same when mixing cleared aluminum scrap with

a given mass of other aluminum scrap. The second process is the refining process itself, which

generally consists of melting the aluminum scrap metal, resulting in a redistribution (partitioning)

of mass and radioactivity. Partitioning of mass during melting is radionuclide-independent,

however, partitioning of radioactivity during refining is element-dependent. The following 
Section 6 Evaluation of Aluminum

6-9 NUREG-1640

0 ' 0 % 01& 6.1

& ' 0

0

( & 6.2

Table 6.2 Elemental partitioning factor ranges (%) for aluminum refining

Elements

Metal

Product

Baghouse

Dust Dross Off-gas

Ac, Th, Pa, U, Np, Pu, Am, Cm, Cr, Fe, Co, Ni, Cu,

Mo, Nb, Ag, Cd, Sb, Ir, Pb, Bi, Ra

95–100 0 0–5 0

Tc, Ru, Re, Po 70–100 0 0–30 0

C 71–100 0 3.8–6.2 0

Zn 90–99.8 4.8–5.2 0 0

Sr, Ba, Zr 38–62 0 38–62 0

Y, Ce, Pm, Eu 19–31 0 56–94 0

Na, K, Cs, Ca, Mn 0 .95–1.05 94–100 0

P, S, Se 0 0–30 70–100 0

I 0 0 59–100 .6–1.4

Cl 0 29–69 30–70 .9–1.1

H, Rn 0–5 0 0 95–100

equations are used to calculate the concentrations in refinery co-products at those points in the

material flow which correspond to potential exposure scenarios.

The total mass of material entering the furnace in a year, including cleared and other scrap, was

calculated using Equation 6.1.

where

M1 = total mass of scrap metal entering the furnace per charge (g/charge)

and

M0 = mass of cleared material entering the furnace per charge (g/charge)

MNC = mass of other scrap metal entering the furnace per charge (g/charge)

Mixing of cleared scrap with metal from sources other than licensed facility can occur at the

scrap dealer (i.e., secondary metal pool) and at the refinery, where material from the primary

metal pool enters the furnace. In this analysis, no distinction is made between the two sources of

other metal. The mass of other metal includes contributions at the scrap yard and at the refinery. 

The radionuclide concentration in the metal entering the furnace was calculated using

Equation 6.2. The following equations are intended to be evaluated separately for each

radionuclide in the analysis. Therefore, parameters such as concentration, decay factors, decay

constants, and dose conversion factors are not explicitly subscripted for each radionuclide.
Evaluation of Aluminum Section 6

NUREG-1640 6-10

0V ' 0 ( I

V ( &3< 6.3

0G ' 0 ( I

G ( &3< 6.4

0

S ' 0 ( IS ( &3< 6.5

where

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

and

M0 = mass of cleared material entering the furnace per charge (g/charge)

M1 = total mass of scrap metal entering the furnace per charge (g/charge)

C0 = original concentration of cleared material (pCi/g)

For slag, baghouse dust, and off-gas, Equations 6.1 and 6.2 were evaluated using annual average

values for the masses of scrap entering the furnaces because all the exposure scenarios for these

materials depend on annual average concentrations. For metal, both an annual average and a

single charge evaluation of Equations 6.1 and 6.2 were conducted. This was done for metal

because there are metal products that could easily be manufactured from a single refinery charge. 

The single charge concentrations were used in metal product-use exposure scenarios except

where noted. (See Appendix D for additional details.)

5HILQHU\3URFHVV

To accurately account for concentration changes in the different products, the mass of each

refinery product must be calculated. Equations 6.3, 6.4, and 6.5 are used to calculate the masses

of slag, dust, and metal product, respectively.

where

Ms = mass of slag produced from a refinery per year (g/y)

Md = mass of dust produced from a refinery per year (g/y)

Mp = mass of metal product produced from a refinery per year (g/y)

and

M1 = total mass of scrap entering the furnace per charge (g/charge)

fs1 = mass partitioning factor for slag during the refining process (dimensionless)

fd1 = mass partitioning factor for dust during the refining process (dimensionless)

fp1 = mass partitioning factor for metal product during the refining process

(dimensionless)

CPY = number of charges per refinery per year (charge)
Section 6 Evaluation of Aluminum

6-11 NUREG-1640

&V' & ( I

V ( 0

0 ( I

V

' & ( I

V

I

V

6.6

&G' & ( I

G

I

G

6.7

&

S' & ( I

S

I

S

6.8

The total amount of radioactivity in the original metal entering the furnace during the refining

process is partitioned among four product materials. Equation 6.6 shows the calculation for

radionuclide concentration in slag, taking into account both the mass and elemental partitioning

factors.

where

Cs = radionuclide concentration in slag after the refining process (pCi/g)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

fs = slag elemental partitioning factor during the refining process (dimensionless)

M1 = total mass of scrap entering the furnace per charge (g/charge)

fs1 = mass partitioning factor for slag during the refining process (dimensionless)

The concentration of radionuclides in the dust and metal product are similarly calculated using

Equations 6.7 and 6.8, respectively.

where

Cd = radionuclide concentration in dust after the refining process (pCi/g)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

fd = dust elemental partitioning factor during the refining process(dimensionless)

fd1 = mass partitioning factor for dust during the refining process (dimensionless)

where

Cp = radionuclide concentration in metal product after the refining process (pCi/g)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

fp = metal product elemental partitioning factor during the refining process

(dimensionless)

fp1 = mass partitioning factor for metal product during the refining process

(dimensionless)
Evaluation of Aluminum Section 6

NUREG-1640 6-12

$

J ' & ( 0 ( IJ ( &3< 6.9

0UD ' 0G (  & %+HII 6.10

0GE ' 0G & 0UD 6.11

No mass is explicitly calculated for the off-gas. Exposure scenarios for atmospheric effluents are

based on the total amount of radioactivity released from the refinery stack each year. The annual

amount of radioactivity in the off-gas was calculated using Equation 6.9. 

where

Ag = radioactivity in the off-gases leaving the refinery stack in a year (pCi/y)

and

C1 = radionuclide concentration in scrap entering the refining process (pCi/g)

M1 = total mass of scrap entering the furnace per charge (g/charge)

fg = off-gas elemental partitioning factor during the refining process (dimensionless)

CPY = number of charges per refinery per year (charge)

Equations 6.10 and 6.11 are used to calculate the mass of dust that escapes the baghouse filters

and the mass that is captured in the baghouse, respectively. 

where

Mra = total mass of dust that escapes the baghouse in a year (g)

and

Md = mass of dust produced from the refining process in a year (g)

BHeff = baghouse efficiency (dimensionless)

where

Mdb = total mass of dust captured in the refinery baghouse in a year (g)

and

Md = mass of dust produced from the refining process in a year (g)

Mra = total mass of dust that escapes the baghouse in a year (g)

5DGLRDFWLYLW\&RQFHQWUDWLRQVLQ$OXPLQXP5HILQLQJ&R3URGXFWV

Mean radionuclide concentrations in the co-products of aluminum refining are listed in

Table 6.3. These values represent estimated radioactivity concentrations in the refinery output. 

The values are normalized to a unit radioactivity concentration in scrap and are only listed in S.I.
Section 6 Evaluation of Aluminum

6-13 NUREG-1640

'7 ' 'H[W%'LQJ 6.12

units since the values are numerically identical if expressed in conventional units (e.g. pCi/g

product per pCi/g scrap).

As stated above, Table 6.3 lists the mean concentration of each radionuclide in each medium. 

Tabulations are limited to mean values simply because of the space that would be required if

percentiles from the distributions were also tabulated. The entire distribution of values for each

radionuclide in the appropriate medium was used as input for the exposure scenario analysis.

'RVH$VVHVVPHQWIRU8QLTXH$OXPLQXP5HF\FOHDQG'LVSRVDO

6FHQDULRV

Most of the potential exposure scenarios for recycled and disposed aluminum scrap are

adequately covered by adapting the steel scrap scenarios described in Section 4. Only one

scenario was added to the aluminum analysis that is not already described: a piece of cookware

made out of recycled aluminum that is used by a member of the general public in a home

situation. This scenario was not included in the set of scenarios for steel because of the small

potential doses previously calculated in other analyses (e.g., O’Donnell 1978). However, it was

included here because aluminum had not been analyzed in previous studies and because

aluminum cookware is commonly used in the U.S. 

Recycled aluminum can be made into a variety of cookware, including large pots, baking pans,

skillets, and coffee pots. The scenario described below involves using an aluminum pot, where

material corroded from the pot might be ingested through the food cooked in it.

([SRVXUHSDWKZD\V

External: This scenario includes external exposure to penetrating radiation from the volume

source of an aluminum pot.

Ingestion: If an aluminum pot is used to boil water or cook food, a small amount of material

could corrode off the pot and transfer to the water or food in the pot. This material would then

be ingested with the prepared food.

Suspension of particulates from aluminum cookware is unlikely, therefore the inhalation pathway

is not included.

0DWKHPDWLFDO5HSUHVHQWDWLRQ

The annual total effective dose equivalent (TEDE) is calculated by adding the effective dose

equivalents from the external and ingestion exposure pathways. The TEDE for a member of the

public using an aluminum pot is represented by Equation 6.12.
Evaluation of Aluminum Section 6

NUREG-1640 6-14

where

DT = TEDE for the scenario (mrem/y)

and

Dext = EDE due to external exposure (mrem/y)

Ding = EDE due to ingestion (mrem/y)
Section 6 Evaluation of Aluminum

6-15 NUREG-1640

Table 6.3 Results of material flow model—aluminum refinery

Mean radionuclide concentrations in refinery products (Bq/g product per Bq/g scrap)

Refined Metal Off-gas

Nuclide Single Charge Annual Slag Dust (Bq per Bq/g)

H-3 5.8E-04 9.4E-06 0.0E+00 0.0E+00 9.6E+07

C-14 3.1E-02 4.8E-04 8.4E-05 0.0E+00 0.0E+00

Na-22 0.0E+00 0.0E+00 1.6E-03 3.6E-04 0.0E+00

P-32 0.0E+00 0.0E+00 1.4E-03 5.3E-03 0.0E+00

S-35 0.0E+00 0.0E+00 1.4E-03 5.3E-03 0.0E+00

Cl-36 0.0E+00 0.0E+00 8.4E-04 1.8E-02 9.7E+05

K-40 0.0E+00 0.0E+00 1.6E-03 3.6E-04 0.0E+00

Ca-41 0.0E+00 0.0E+00 1.6E-03 3.6E-04 0.0E+00

Ca-45 0.0E+00 0.0E+00 1.6E-03 3.6E-04 0.0E+00

Cr-51 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Mn-54 0.0E+00 0.0E+00 1.6E-03 3.6E-04 0.0E+00

Fe-55 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00

Co-57 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Co-58 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Fe-59 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Ni-59 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Co-60 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Ni-63 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Zn-65 3.4E-02 5.3E-04 0.0E+00 1.8E-03 0.0E+00

Cu-67 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Se-75 0.0E+00 0.0E+00 1.4E-03 5.3E-03 0.0E+00

Sr-85 1.8E-02 2.8E-04 8.4E-04 0.0E+00 0.0E+00

Sr-89 1.8E-02 2.8E-04 8.4E-04 0.0E+00 0.0E+00

Sr-90 1.8E-02 2.8E-04 8.4E-04 0.0E+00 0.0E+00

Y-91 8.9E-03 1.4E-04 1.3E-03 0.0E+00 0.0E+00

Mo-93 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Nb-93m 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00

Nb-94 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00

Nb-95 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Zr-95 1.8E-02 2.8E-04 8.4E-04 0.0E+00 0.0E+00

Tc-99 3.0E-02 4.8E-04 2.5E-04 0.0E+00 0.0E+00

Ru-103 3.0E-02 4.8E-04 2.6E-04 0.0E+00 0.0E+00

Ru-106 3.0E-02 4.8E-04 2.5E-04 0.0E+00 0.0E+00

Ag-108m 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Cd-109 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Ag-110m 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Sb-124 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00

I-125 0.0E+00 0.0E+00 1.3E-03 0.0E+00 9.7E+05

Sb-125 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

I-129 0.0E+00 0.0E+00 1.3E-03 0.0E+00 9.8E+05

I-131 0.0E+00 0.0E+00 1.3E-03 0.0E+00 9.6E+05

Ba-133 1.8E-02 2.8E-04 8.4E-04 0.0E+00 0.0E+00

Cs-134 0.0E+00 0.0E+00 1.6E-03 3.6E-04 0.0E+00

Cs-137 0.0E+00 0.0E+00 1.6E-03 3.6E-04 0.0E+00
Evaluation of Aluminum Section 6

Table 6.3 Results of material flow model—aluminum refinery

Mean radionuclide concentrations in refinery products (Bq/g product per Bq/g scrap)

Refined Metal Off-gas

Nuclide Single Charge Annual Slag Dust (Bq per Bq/g)

NUREG-1640 6-16

Ce-141 9.0E-03 1.4E-04 1.3E-03 0.0E+00 0.0E+00

Ce-144 9.0E-03 1.4E-04 1.3E-03 0.0E+00 0.0E+00

Pm-147 8.9E-03 1.4E-04 1.3E-03 0.0E+00 0.0E+00

Eu-152 8.9E-03 1.4E-04 1.3E-03 0.0E+00 0.0E+00

Eu-154 9.0E-03 1.4E-04 1.3E-03 0.0E+00 0.0E+00

Eu-155 8.9E-03 1.4E-04 1.3E-03 0.0E+00 0.0E+00

Re-186 3.0E-02 4.8E-04 2.6E-04 0.0E+00 0.0E+00

Ir-192 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Pb-210 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Po-210 3.0E-02 4.8E-04 2.5E-04 0.0E+00 0.0E+00

Bi-210 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Rn-222 5.9E-04 9.7E-06 0.0E+00 0.0E+00 9.6E+07

Ra-223 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00

Ra-224 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00

Ac-225 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Ra-225 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Ra-226 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Ac-227 3.5E-02 5.5E-04 3.0E-05 0.0E+00 0.0E+00

Th-227 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Th-228 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Ra-228 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Th-229 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Th-230 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Pa-231 3.5E-02 5.5E-04 3.0E-05 0.0E+00 0.0E+00

Th-231 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Th-232 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00

Pa-233 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

U-233 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Th-234 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00

U-234 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

U-235 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00

Np-237 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Pu-238 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

U-238 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Pu-239 3.5E-02 5.5E-04 2.8E-05 0.0E+00 0.0E+00

Pu-240 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Pu-241 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Am-241 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Cm-242 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Pu-242 3.5E-02 5.5E-04 2.7E-05 0.0E+00 0.0E+00

Cm-244 3.5E-02 5.5E-04 2.9E-05 0.0E+00 0.0E+00
Section 6 Evaluation of Aluminum

6-17 NUREG-1640

& ' &[ H

& U W

V 6.13

'H[W ' &( *)( 8*) (W

[V( W\V 6.14

The mathematical representations for each exposure pathway are discussed in the following three

subsections.

Equation 6.13 estimates the radionuclide concentration in the aluminum pot at the time use. This

incorporates radioactive decay from the time the scrap aluminum is cleared by a NRC licensed

facility to the time the scenario begins. The reference to "source material" in the parameters of

Equation 6.13 and other equations refers to the material that represents the source of

radioactivity. In this scenario, the source material is an aluminum pot. 

where

C0 = radionuclide concentration in the source material at time the scenario begins (pCi/g)

and

Cx = undecayed radionuclide concentration in the source material (pCi/g)

r = radioactive decay constant (1/d)

ts = time from clearance from nuclear facility to time scenario begins (d)

External Exposure

An individual in close proximity to the pot while using it would be exposed to penetrating

radiation from the mass of aluminum in the pot. This external exposure is calculated using

Equation 6.14.

where

Dext = EDE due to external exposure (mrem/y)

and

C0 = radionuclide concentration in the source material at time the scenario begins (pCi/g)

GF = geometry factor for the scenario (mrem/h per pCi/g)

UGF = uncertainty in geometry factor (dimensionless)

txs = daily number of hours of exposure for the scenario (h/d)

tys = annual number of days of exposure for the scenario (d/y)

Ingestion Exposure

While food is being cooked in an aluminum pot, a certain amount of aluminum could corrode off

the pot and transfer to the food. The dose due to this exposure pathway is presented in

Equation 6.15.
Evaluation of Aluminum Section 6

NUREG-1640 6-18

'LQJ ' & ( &5$O ( ',W ( )', ( W

\V ( ')LQJ ( (&  6.15

where

Ding = EDE due to ingestion (mrem/y)

and

C0 = radionuclide concentration in the source material at time the scenario begins (pCi/g)

CRAl = corrosion and transfer rate for aluminum (mg Al/kg food)

DIt = total dietary intake (kg food/d)

FDI = fraction of total dietary intake that is cooked in aluminum pot (dimensionless)

DFing = ingestion dose factor (mrem/pCi intake)

1E-03 = unit conversion factor (g/mg)

tys = annual number of days of exposure for the scenario (d/y)

3DUDPHWHU'LVFXVVLRQIRUDOO0RGHOHG6FHQDULRV

Calculation of potential impacts from recycle of cleared aluminum scrap material depends on

many parameter values. Parameter values are needed for both material flow and dose assessment

models. The material flow parameter values rely on information from the U.S. secondary

aluminum industry. The parameter values for the dose modeling are a function of receptor

behavior, such as time on a specific job or breathing rate, as well as how the radionuclides are

transported in the environment. The dose modeling parameter values are based on those used in

the iron and steel modeling described in Section 4. Only those parameter values that are different

from those used in the iron and steel modeling are discussed in this section. 

6FHQDULR7LPLQJ

The same scenario-timing assumptions that are presented for the BOF steel modeling (Section 4)

are used for the aluminum modeling.

'RVH(YDOXDWLRQ

This section presents a discussion of parameter values used for the analysis of aluminum recycle

scenarios. In general, the same scenarios are analyzed for aluminum recycle as were analyzed for

steel recycle in Section 4. Values used for many of the parameters are also the same as for the

steel recycle analysis. For some parameters, however, values specific to the recycle of aluminum

were used in order to more appropriately model the scenarios as they would likely occur for

aluminum recycle. The following discussion is limited to these specific parameter values. If a

parameter is not discussed below and listed in Table B.12, the same value as used for the steel

evaluation (Table B.7) is used for aluminum.
Section 6 Evaluation of Aluminum

6-19 NUREG-1640

,QSXW&RQFHQWUDWLRQVIURPWKH0DWHULDO)ORZ

The undecayed radionuclide concentration in the source material, Cx, is used as the source

material input concentration for scenario evaluations. This parameter is radionuclide dependent

and is calculated in the material flow modeling. Table B.14 lists the sources for Cx, as they

appear in the mathematical modeling of the material flow (e.g., Cp, concentration in metal

product after the refining process).

([WHUQDO([SRVXUH3DUDPHWHUV

This section presents values for those radionuclide-independent parameters used in calculating

external exposure, including those that address duration of exposure and material density. 

Values for these parameters are tabulated in Table B.12.

The dose factors for the additional scenario involving use of an aluminum pot are based on the

assumption that the use occurs once per day for approximately 30 minutes. A normal residence

period of 350 days per year is assumed. From these assumptions, a range of .375 to .5 h/d was

used for txs.

For the scrap disposal scenario a fixed value of 1.35E+6 g/m3 was used for the density of waste.

,QJHVWLRQ([SRVXUH3DUDPHWHUV

Radionuclide-independent parameters used in the evaluation of ingestion exposure include those

that address environmental and biotic transport, as well as human consumption. This section

describes the values for those unique parameters used in the calculation of ingestion exposure. 

The only parameters that are different in the aluminum recycling analysis are for the scenario

addressing use of aluminum cookware.

When an aluminum pot is used to cook foods, a certain amount of aluminum is corroded and

transferred to the food. According to the US Public Health Service, acidic foods, such as

tomatoes, tomato sauce and applesauce, tend to accumulate more aluminum than other foods

(U.S. Public Health Service 1992). Aluminum concentrations in precooked foods (applesauce,

green beans, beef, eggs, ham, pudding, rice, and tomato sauce) range from less than 0.10 to 21.6

mg Al/kg food. However, if these foods are cooked in an aluminum pot, the concentrations

range from 0.24 to 125 mg Al/kg food (U.S. Public Health Services 1992). This means the

increase in aluminum concentration due to cooking in an aluminum pot is from 0.14 to 103.4 mg

Al/kg. This range was used for this scenario evaluation, and the average value of 52 mg Al/kg

food was used as the most likely value for CRA1.

A value for dietary intake was calculated using “The Exposure Factors Sourcebook” (AIHC

1995), which presents data for total dietary intake. Data range from 1.4 kg/d for the UK to 1.6

kg/d for the U.S. and are based on food purchased minus a certain percent for waste. Ten percent

waste is assumed in the UK while 15% waste is assumed in the U.S. AIHC (1995) suggests a
Evaluation of Aluminum Section 6

NUREG-1640 6-20

value of 1.6 kg/d be used for purposes of non-U.S. FDA risk assessments. Therefore, a uniform

range of 1.3 to 1.6 was used for the total dietary intake, DIt

. The corrosion and transfer rate

discussed above is for a wide variety of foods, so a range of .33 to 1.0 is used for the fraction of

total dietary intake that is cooked in the aluminum pot, FDI.

$WPRVSKHULF5HOHDVH3DUDPHWHUV

This section presents the values for those radionuclide-independent parameters used for

calculating atmospheric dispersion of refinery stack releases from aluminum recycling facilities. 

The only radionuclide-independent parameter different from the steel analysis is the total mass of

dust that escapes the refinery baghouse in a year, Mra. The distribution calculated in the material

flow model is used as the input distribution for this parameter.

$OXPLQXP6XUIDFHWR0DVV5DWLR

The surface-to-mass ratios of various aluminum objects (spheres and cylindrical bar stock) were

examined in estimating a range for aluminum scrap. Aluminum objects are assumed to have a

density of 2.7 g/cm3. Surface-to-mass ratios for various aluminum objects ranges from

approximately 0.04 cm2/g for large-radius spheres and bar stock, up to 10 cm2/g or higher for

very thin sheets and pipes. 

Data are not available to provide an adequate basis for choosing a “best estimate” from this range

of values. Based on these data and assumptions, the value of surface-to-mass ratio for aluminum

is best described by a uniform distribution having a minimum of 1.0 cm2

/g and a maximum of

7.0 cm2/g. The minimum value is characteristic of pipes and sheets having a thickness of 0.25

cm. The maximum value is characteristic of pipes and sheets having a thickness of 0.05 cm. 

These surface-to-mass ratios for aluminum are representative of pipes and sheets of various sizes

with residual contamination on one side only. A wide variety of aluminum objects commonly

found at nuclear facilities have surface-to-mass values that fall within this range. 

'RVH)DFWRUVIRU5HF\FOHDQG'LVSRVDORI$OXPLQXP6FUDS

This analysis of recycle of cleared aluminum scrap includes 17 separate scenarios evaluated for

85 radionuclides. Figure 6.2 shows which scenarios describe the critical groups and for how

many radionuclides. There are six scenarios which have the highest mean dose factor for at least

one radionuclide. The largest number of radionuclides have critical groups described by

scenarios associated with transporting (52 radionuclides) or handling (17 radionuclide)

unprocessed scrap. Individuals handling aluminum dross (slag) constitute the critical group for 2

radionuclides. For one volatile radionuclide (H-3), the critical group consists of individuals

exposed to atmospheric releases from the refining process. Thirteen radionuclides are limited by

scenarios associated with use of consumer products made from recycled aluminum. Use of

aluminum cookware accounts for 11 of these radionuclides and use of a small metal object close

to the body accounts for two of them. Table 6.4 lists the mass-based dose factors for each
Section 6 Evaluation of Aluminum

6-21 NUREG-1640

radionuclide. Table 6.5 lists the corresponding derived surficial dose factors for each

radionuclide. Results for all 17 aluminum scenarios are tabulated in Appendix H. 

The mean values of the critical-group dose factors for each radionuclide are listed in Table 6.4 as

the “critical-group dose factor.” These represent the dose to the average member of the critical

group exposed to radioactivity distributed throughout the mass of cleared aluminum (Bq/g or

pCi/g). The circumstances of that exposure are described by the scenario indicated in the right

hand column. The 5th, 50th, and 95th percentiles listed for each radionuclide represent the

underlying distribution of dose factors calculated for each critical group. The range of values

from the 5th to the 95th percentile is the 90% confidence interval on the dose factor. That is, there

is a 90% certainty that the dose factor for the average member of the critical group lies within

this interval. The confidence interval is a subjective measure of uncertainty in the dose factor

that includes estimates of the variability and uncertainty in the parameters used in each scenario.

The ratio of the 95th to the 5th percentile is a useful measure of the relative width of the 90%

confidence interval for comparison between scenarios. Smaller values of the 95/5 ratio indicate

less uncertainty than larger values. The scenarios with the smallest uncertainty are those with the

fewest number of exposure pathways and the least uncertainty in the parameters describing those

pathways. The scrap transportation scenario accounts for 52 of the 85 radionuclides. It has the

smallest uncertainty of all the critical group scenarios with a 95/5 ratio of about 2 for most

radionuclides. The sources of uncertainty in this scenario are similar to those for the steel scrap

transportation scenario discussed in Section 4.9.

For all scenarios that take place subsequent to the initial transport of scrap, additional sources of

uncertainty are introduced and wider confidence intervals result. Scenarios that address handling

of scrap include uncertainty due to dilution with other scrap. They also include additional

exposure pathways—inhalation of resuspended dust and inadvertent ingestion under dusty

conditions. Scenarios that address handling of refinery products such as aluminum dross include

additional uncertainty in how much of each radionuclide is partitioned to these materials. In

addition, the aluminum cookware scenario includes uncertainty in dietary practices. For 

aluminum, this group of handling, processing, and consumer product scenarios have 95/5 ratios

that range from about 10 to about 20.

Greater uncertainty is associated with scenarios that involve multiple exposure pathways and

complex submodels. One radionuclide (H-3) has a critical group consisting of individuals living

in the vicinity of an aluminum refinery and exposed to atmospheric releases. This scenario

includes an atmospheric dispersion model and pathways for ingestion, inhalation, and external

exposure, each of which contributes to uncertainty in the dose factor. In this case, the

atmospheric release scenario has a 95/5 ratio of 50. Most of this uncertainty is due to the

atmospheric dispersion model with additional contributions from uncertainties in the ingestion

dose pathway.

The mean values of the derived surficial dose factors for each radionuclide in Table 6.5 represent

the dose to the average member of the critical group exposed to radioactivity initially distributed
Evaluation of Aluminum Section 6

NUREG-1640 6-22

Scrap Transport

Scrap Handling

Use of Aluminum Cookware

Small Metal Object Close to Body

Slag Handling

Refinery Atmospheric Releases

52

17

1 2 2

11

0

10

20

30

40

50

60

Number of Radionuclides

Aluminum Critical Group Scenarios

Figure 6.2 Scenarios describing critical groups for aluminum recycle

over the surface cleared aluminum scrap (Bq/cm2 or pCi/cm2). Derived surficial dose factors are

calculated from mass-based dose factors by use of a surface-to-mass ratio, appropriate for typical

aluminum objects available for clearance. The surface-to-mass ratio is used to derive surficial

dose factors as described in Section 4.7.
Section 6 Evaluation of Aluminum

6-23 NUREG-1640

Table 6.4 Aluminum recycle critical-group dose factors–mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

H-3 1.8E-06 1.3E-07 9.4E-07 6.6E-06 6.6E-09 4.9E-10 3.5E-09 2.5E-08AL-ATMO-REFINER-N

C-14 2.6E-04 5.2E-05 2.1E-04 5.8E-04 9.4E-07 1.9E-07 7.9E-07 2.2E-06AL-METL-COOKWAR-N

Na-22 4.4E+00 2.8E+00 4.4E+00 6.0E+00 1.6E-02 1.0E-02 1.6E-02 2.2E-02AL-SCRP-TRANSPO-W

P-32 2.6E-03 1.7E-03 2.6E-03 3.6E-03 9.7E-06 6.2E-06 9.6E-06 1.3E-05AL-SCRP-TRANSPO-W

S-35 8.6E-06 5.5E-06 8.7E-06 1.2E-05 3.2E-08 2.0E-08 3.2E-08 4.4E-08AL-SCRP-TRANSPO-W

Cl-36 6.8E-04 4.4E-04 6.8E-04 9.4E-04 2.5E-06 1.6E-06 2.5E-06 3.5E-06AL-SCRP-TRANSPO-W

K-40 3.2E-01 2.1E-01 3.3E-01 4.5E-01 1.2E-03 7.7E-04 1.2E-03 1.6E-03AL-SCRP-TRANSPO-W

Ca-41 1.0E-05 1.2E-06 6.9E-06 2.9E-05 3.8E-08 4.4E-09 2.6E-08 1.1E-07AL-DROS-HANDLIN-W

Ca-45 3.0E-05 1.9E-05 3.0E-05 4.2E-05 1.1E-07 7.1E-08 1.1E-07 1.5E-07AL-SCRP-TRANSPO-W

Cr-51 4.9E-02 3.2E-02 4.9E-02 6.8E-02 1.8E-04 1.2E-04 1.8E-04 2.5E-04AL-SCRP-TRANSPO-W

Mn-54 1.7E+00 1.1E+00 1.7E+00 2.3E+00 6.3E-03 4.0E-03 6.3E-03 8.7E-03AL-SCRP-TRANSPO-W

Fe-55 7.3E-05 1.6E-05 6.3E-05 1.6E-04 2.7E-07 5.9E-08 2.3E-07 6.1E-07AL-METL-COOKWAR-N

Co-57 7.6E-02 4.9E-02 7.6E-02 1.0E-01 2.8E-04 1.8E-04 2.8E-04 3.9E-04AL-SCRP-TRANSPO-W

Co-58 1.9E+00 1.2E+00 1.9E+00 2.6E+00 7.0E-03 4.5E-03 7.0E-03 9.7E-03AL-SCRP-TRANSPO-W

Fe-59 2.3E+00 1.5E+00 2.3E+00 3.2E+00 8.5E-03 5.4E-03 8.4E-03 1.2E-02AL-SCRP-TRANSPO-W

Ni-59 2.9E-05 6.2E-06 2.4E-05 6.7E-05 1.1E-07 2.3E-08 9.0E-08 2.5E-07AL-METL-COOKWAR-N

Co-60 5.1E+00 3.3E+00 5.1E+00 7.0E+00 1.9E-02 1.2E-02 1.9E-02 2.6E-02AL-SCRP-TRANSPO-W

Ni-63 8.2E-05 1.8E-05 7.0E-05 1.9E-04 3.0E-07 6.7E-08 2.6E-07 6.9E-07AL-METL-COOKWAR-N

Zn-65 1.2E+00 7.6E-01 1.2E+00 1.6E+00 4.4E-03 2.8E-03 4.4E-03 6.1E-03AL-SCRP-TRANSPO-W

Cu-67 4.1E-02 2.1E-02 3.8E-02 7.2E-02 1.5E-04 7.9E-05 1.4E-04 2.7E-04AL-SCRP-TRANSPO-W

Se-75 4.9E-01 3.1E-01 4.9E-01 6.8E-01 1.8E-03 1.2E-03 1.8E-03 2.5E-03AL-SCRP-TRANSPO-W

Sr-85 9.4E-01 6.0E-01 9.4E-01 1.3E+00 3.5E-03 2.2E-03 3.5E-03 4.8E-03AL-SCRP-TRANSPO-W

Sr-89 2.3E-03 1.5E-03 2.3E-03 3.2E-03 8.6E-06 5.5E-06 8.6E-06 1.2E-05AL-SCRP-TRANSPO-W

Sr-90 1.0E-02 1.9E-03 8.8E-03 2.4E-02 3.8E-05 7.1E-06 3.3E-05 8.9E-05AL-METL-COOKWAR-N

Y-91 6.9E-03 4.4E-03 6.9E-03 9.6E-03 2.6E-05 1.6E-05 2.6E-05 3.5E-05AL-SCRP-TRANSPO-W

Mo-93 5.5E-04 8.4E-05 4.1E-04 1.6E-03 2.1E-06 3.1E-07 1.5E-06 5.8E-06AL-METL-SMOBJCT-N

Nb-93m 8.7E-05 1.5E-05 6.5E-05 2.4E-04 3.2E-07 5.4E-08 2.4E-07 8.8E-07AL-METL-SMOBJCT-N

Nb-94 3.3E+00 2.1E+00 3.3E+00 4.5E+00 1.2E-02 7.8E-03 1.2E-02 1.7E-02AL-SCRP-TRANSPO-W

Nb-95 1.4E+00 9.3E-01 1.4E+00 2.0E+00 5.4E-03 3.4E-03 5.3E-03 7.4E-03AL-SCRP-TRANSPO-W

Zr-95 1.4E+00 9.2E-01 1.4E+00 2.0E+00 5.3E-03 3.4E-03 5.3E-03 7.4E-03AL-SCRP-TRANSPO-W

Tc-99 1.8E-04 4.1E-05 1.4E-04 4.5E-04 6.7E-07 1.5E-07 5.2E-07 1.7E-06AL-METL-COOKWAR-N

Ru-103 9.3E-01 5.9E-01 9.2E-01 1.3E+00 3.4E-03 2.2E-03 3.4E-03 4.7E-03AL-SCRP-TRANSPO-W

Ru-106 4.1E-01 2.6E-01 4.1E-01 5.7E-01 1.5E-03 9.8E-04 1.5E-03 2.1E-03AL-SCRP-TRANSPO-W

Ag-108m 3.2E+00 2.1E+00 3.2E+00 4.5E+00 1.2E-02 7.7E-03 1.2E-02 1.6E-02AL-SCRP-TRANSPO-W

Cd-109 1.3E-03 2.8E-04 1.1E-03 2.8E-03 4.7E-06 1.0E-06 4.0E-06 1.0E-05AL-METL-COOKWAR-N
Evaluation of Aluminum Section 6

Table 6.4 Aluminum recycle critical-group dose factors–mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

NUREG-1640 6-24

Ag-110m 5.7E+00 3.6E+00 5.7E+00 7.8E+00 2.1E-02 1.3E-02 2.1E-02 2.9E-02AL-SCRP-TRANSPO-W

Sb-124 3.6E+00 2.3E+00 3.6E+00 5.0E+00 1.3E-02 8.5E-03 1.3E-02 1.9E-02AL-SCRP-TRANSPO-W

I-125 1.3E-03 8.3E-04 1.3E-03 1.8E-03 4.8E-06 3.1E-06 4.8E-06 6.7E-06AL-SCRP-TRANSPO-W

Sb-125 8.1E-01 5.2E-01 8.1E-01 1.1E+00 3.0E-03 1.9E-03 3.0E-03 4.1E-03AL-SCRP-TRANSPO-W

I-129 1.9E-03 2.7E-04 1.1E-03 5.6E-03 6.9E-06 1.0E-06 4.1E-06 2.1E-05AL-DROS-HANDLIN-N

I-131 5.0E-01 3.2E-01 4.9E-01 7.2E-01 1.9E-03 1.2E-03 1.8E-03 2.7E-03AL-SCRP-TRANSPO-W

Ba-133 5.6E-01 3.6E-01 5.6E-01 7.7E-01 2.1E-03 1.3E-03 2.1E-03 2.8E-03AL-SCRP-TRANSPO-W

Cs-134 3.2E+00 2.1E+00 3.2E+00 4.4E+00 1.2E-02 7.6E-03 1.2E-02 1.6E-02AL-SCRP-TRANSPO-W

Cs-137 1.2E+00 7.9E-01 1.2E+00 1.7E+00 4.6E-03 2.9E-03 4.6E-03 6.3E-03AL-SCRP-TRANSPO-W

Ce-141 5.4E-02 3.5E-02 5.4E-02 7.5E-02 2.0E-04 1.3E-04 2.0E-04 2.8E-04AL-SCRP-TRANSPO-W

Ce-144 6.6E-02 4.2E-02 6.6E-02 9.1E-02 2.4E-04 1.6E-04 2.4E-04 3.4E-04AL-SCRP-TRANSPO-W

Pm-147 5.5E-05 1.2E-05 4.5E-05 1.2E-04 2.0E-07 4.6E-08 1.7E-07 4.6E-07AL-SCRP-HANDLIN-W

Eu-152 2.2E+00 1.4E+00 2.2E+00 3.1E+00 8.2E-03 5.3E-03 8.2E-03 1.1E-02AL-SCRP-TRANSPO-W

Eu-154 2.4E+00 1.6E+00 2.4E+00 3.3E+00 9.0E-03 5.8E-03 9.0E-03 1.2E-02AL-SCRP-TRANSPO-W

Eu-155 2.1E-02 1.4E-02 2.1E-02 2.9E-02 7.9E-05 5.0E-05 7.9E-05 1.1E-04AL-SCRP-TRANSPO-W

Re-186 4.9E-03 2.9E-03 4.7E-03 8.0E-03 1.8E-05 1.1E-05 1.7E-05 2.9E-05AL-SCRP-TRANSPO-W

Ir-192 1.4E+00 9.1E-01 1.4E+00 2.0E+00 5.2E-03 3.3E-03 5.2E-03 7.2E-03AL-SCRP-TRANSPO-W

Pb-210 7.5E-01 1.7E-01 5.9E-01 1.8E+00 2.8E-03 6.3E-04 2.2E-03 6.8E-03AL-METL-COOKWAR-N

Po-210 7.4E-02 1.6E-02 6.2E-02 1.6E-01 2.7E-04 5.8E-05 2.3E-04 6.0E-04AL-METL-COOKWAR-N

Bi-210 6.2E-04 3.8E-04 6.0E-04 9.5E-04 2.3E-06 1.4E-06 2.2E-06 3.5E-06AL-SCRP-TRANSPO-W

Rn-222 1.7E+00 1.0E+00 1.6E+00 2.8E+00 6.3E-03 3.7E-03 6.0E-03 1.0E-02AL-SCRP-TRANSPO-W

Ra-223 3.6E-01 2.3E-01 3.6E-01 5.1E-01 1.3E-03 8.5E-04 1.3E-03 1.9E-03AL-SCRP-TRANSPO-W

Ra-224 1.2E+00 7.2E-01 1.2E+00 2.0E+00 4.5E-03 2.6E-03 4.3E-03 7.3E-03AL-SCRP-TRANSPO-W

Ac-225 2.8E-01 1.8E-01 2.8E-01 4.0E-01 1.0E-03 6.7E-04 1.0E-03 1.5E-03AL-SCRP-TRANSPO-W

Ra-225 9.6E-03 2.4E-03 8.0E-03 2.0E-02 3.5E-05 8.7E-06 3.0E-05 7.6E-05AL-SCRP-HANDLIN-W

Ra-226 3.5E+00 2.2E+00 3.5E+00 4.8E+00 1.3E-02 8.3E-03 1.3E-02 1.8E-02AL-SCRP-TRANSPO-W

Ac-227 1.9E+00 4.4E-01 1.7E+00 4.2E+00 7.1E-03 1.6E-03 6.2E-03 1.6E-02AL-METL-COOKWAR-N

Th-227 1.2E-01 7.6E-02 1.2E-01 1.6E-01 4.3E-04 2.8E-04 4.3E-04 6.0E-04AL-SCRP-TRANSPO-W

Th-228 2.5E+00 1.6E+00 2.5E+00 3.5E+00 9.4E-03 6.0E-03 9.4E-03 1.3E-02AL-SCRP-TRANSPO-W

Ra-228 1.7E+00 1.6E+00 2.5E+00 3.5E+00 6.2E-03 6.0E-03 9.4E-03 1.3E-02AL-SCRP-TRANSPO-W

Th-229 2.3E+00 4.2E-01 1.9E+00 5.2E+00 8.4E-03 1.6E-03 6.9E-03 1.9E-02AL-SCRP-HANDLIN-W

Th-230 3.4E-01 6.3E-02 2.8E-01 7.9E-01 1.3E-03 2.3E-04 1.0E-03 2.9E-03AL-SCRP-HANDLIN-W

Pa-231 1.5E+00 3.0E-01 1.3E+00 3.7E+00 5.5E-03 1.1E-03 4.8E-03 1.4E-02AL-METL-COOKWAR-N

Th-231 3.0E-04 6.6E-05 2.2E-04 7.7E-04 1.1E-06 2.5E-07 8.0E-07 2.8E-06AL-SCRP-TRANSPO-W

Th-232 1.5E+00 2.8E-01 1.2E+00 3.5E+00 5.6E-03 1.0E-03 4.6E-03 1.3E-02AL-SCRP-HANDLIN-W
Section 6 Evaluation of Aluminum

Table 6.4 Aluminum recycle critical-group dose factors–mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

6-25 NUREG-1640

Pa-233 2.6E-01 1.7E-01 2.6E-01 3.6E-01 9.8E-04 6.3E-04 9.7E-04 1.3E-03AL-SCRP-TRANSPO-W

U-233 1.8E-01 3.2E-02 1.4E-01 4.1E-01 6.5E-04 1.2E-04 5.4E-04 1.5E-03AL-SCRP-HANDLIN-W

Th-234 1.5E-02 9.5E-03 1.5E-02 2.0E-02 5.4E-05 3.5E-05 5.4E-05 7.4E-05AL-SCRP-TRANSPO-W

U-234 1.7E-01 3.1E-02 1.4E-01 4.0E-01 6.4E-04 1.2E-04 5.2E-04 1.5E-03AL-SCRP-HANDLIN-W

U-235 1.6E-01 1.0E-01 1.6E-01 2.2E-01 6.0E-04 3.9E-04 6.1E-04 8.3E-04AL-SCRP-TRANSPO-W

Np-237 7.2E-01 1.5E-01 5.9E-01 1.7E+00 2.7E-03 5.5E-04 2.2E-03 6.1E-03AL-SCRP-HANDLIN-W

Pu-238 3.8E-01 6.8E-02 3.1E-01 8.7E-01 1.4E-03 2.5E-04 1.1E-03 3.2E-03AL-SCRP-HANDLIN-W

U-238 1.5E-01 2.8E-02 1.3E-01 3.6E-01 5.7E-04 1.0E-04 4.7E-04 1.3E-03AL-SCRP-HANDLIN-W

Pu-239 4.0E-01 7.3E-02 3.3E-01 9.3E-01 1.5E-03 2.7E-04 1.2E-03 3.4E-03AL-SCRP-HANDLIN-W

Pu-240 4.0E-01 7.3E-02 3.3E-01 9.3E-01 1.5E-03 2.7E-04 1.2E-03 3.4E-03AL-SCRP-HANDLIN-W

Pu-241 6.5E-03 1.2E-03 5.3E-03 1.5E-02 2.4E-05 4.3E-06 2.0E-05 5.5E-05AL-SCRP-HANDLIN-W

Am-241 5.9E-01 1.2E-01 4.9E-01 1.4E+00 2.2E-03 4.4E-04 1.8E-03 5.0E-03AL-SCRP-HANDLIN-W

Cm-242 2.3E-02 4.5E-03 1.9E-02 5.2E-02 8.4E-05 1.7E-05 6.8E-05 1.9E-04AL-SCRP-HANDLIN-W

Pu-242 3.8E-01 7.0E-02 3.1E-01 8.8E-01 1.4E-03 2.6E-04 1.2E-03 3.3E-03AL-SCRP-HANDLIN-W

Cm-244 3.3E-01 6.7E-02 2.7E-01 7.6E-01 1.2E-03 2.5E-04 1.0E-03 2.8E-03AL-SCRP-HANDLIN-W
Evaluation of Aluminum Section 6

NUREG-1640 6-26

Table 6.5 Aluminum recycle critical-group dose factors–surficial

(μSv/y per Bq/cm2

) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

H-3 6.8E-06 5.1E-07 3.1E-06 2.3E-05 2.5E-08 1.9E-09 1.2E-08 8.5E-08AL-ATMO-REFINER-N

C-14 1.0E-03 1.5E-04 7.5E-04 2.7E-03 3.8E-06 5.5E-07 2.8E-06 1.0E-05AL-METL-COOKWAR-N

Na-22 1.8E+01 4.7E+00 1.6E+01 3.4E+01 6.6E-02 1.7E-02 6.1E-02 1.2E-01AL-SCRP-TRANSPO-W

P-32 1.1E-02 2.9E-03 9.6E-03 2.0E-02 3.9E-05 1.1E-05 3.6E-05 7.6E-05AL-SCRP-TRANSPO-W

S-35 3.5E-05 9.2E-06 3.2E-05 6.6E-05 1.3E-07 3.4E-08 1.2E-07 2.4E-07AL-SCRP-TRANSPO-W

Cl-36 2.8E-03 7.3E-04 2.5E-03 5.2E-03 1.0E-05 2.7E-06 9.4E-06 1.9E-05AL-SCRP-TRANSPO-W

K-40 1.3E+00 3.5E-01 1.2E+00 2.5E+00 4.9E-03 1.3E-03 4.5E-03 9.2E-03AL-SCRP-TRANSPO-W

Ca-41 4.1E-05 3.4E-06 2.5E-05 1.3E-04 1.5E-07 1.3E-08 9.2E-08 4.8E-07AL-DROS-HANDLIN-W

Ca-45 1.2E-04 3.2E-05 1.1E-04 2.3E-04 4.5E-07 1.2E-07 4.2E-07 8.6E-07AL-SCRP-TRANSPO-W

Cr-51 2.0E-01 5.3E-02 1.8E-01 3.8E-01 7.4E-04 2.0E-04 6.7E-04 1.4E-03AL-SCRP-TRANSPO-W

Mn-54 6.9E+00 1.8E+00 6.3E+00 1.3E+01 2.5E-02 6.7E-03 2.3E-02 4.8E-02AL-SCRP-TRANSPO-W

Fe-55 2.9E-04 4.4E-05 2.2E-04 7.9E-04 1.1E-06 1.6E-07 8.1E-07 2.9E-06AL-METL-COOKWAR-N

Co-57 3.1E-01 8.1E-02 2.8E-01 5.8E-01 1.1E-03 3.0E-04 1.1E-03 2.2E-03AL-SCRP-TRANSPO-W

Co-58 7.7E+00 2.0E+00 7.0E+00 1.5E+01 2.8E-02 7.5E-03 2.6E-02 5.4E-02AL-SCRP-TRANSPO-W

Fe-59 9.3E+00 2.5E+00 8.5E+00 1.8E+01 3.4E-02 9.1E-03 3.1E-02 6.5E-02AL-SCRP-TRANSPO-W

Ni-59 1.2E-04 1.8E-05 9.0E-05 3.1E-04 4.3E-07 6.6E-08 3.3E-07 1.1E-06AL-METL-COOKWAR-N

Co-60 2.1E+01 5.4E+00 1.9E+01 3.9E+01 7.6E-02 2.0E-02 7.0E-02 1.4E-01AL-SCRP-TRANSPO-W

Ni-63 3.2E-04 5.3E-05 2.5E-04 8.1E-04 1.2E-06 2.0E-07 9.2E-07 3.0E-06AL-METL-COOKWAR-N

Zn-65 4.8E+00 1.3E+00 4.5E+00 9.1E+00 1.8E-02 4.7E-03 1.6E-02 3.4E-02AL-SCRP-TRANSPO-W

Cu-67 1.7E-01 4.2E-02 1.4E-01 3.8E-01 6.2E-04 1.6E-04 5.3E-04 1.4E-03AL-SCRP-TRANSPO-W

Se-75 2.0E+00 5.2E-01 1.8E+00 3.8E+00 7.3E-03 1.9E-03 6.7E-03 1.4E-02AL-SCRP-TRANSPO-W

Sr-85 3.8E+00 1.0E+00 3.5E+00 7.2E+00 1.4E-02 3.7E-03 1.3E-02 2.7E-02AL-SCRP-TRANSPO-W

Sr-89 9.4E-03 2.5E-03 8.6E-03 1.8E-02 3.5E-05 9.2E-06 3.2E-05 6.6E-05AL-SCRP-TRANSPO-W

Sr-90 4.0E-02 5.7E-03 2.8E-02 1.2E-01 1.5E-04 2.1E-05 1.0E-04 4.3E-04AL-METL-COOKWAR-N

Y-91 2.8E-02 7.4E-03 2.6E-02 5.3E-02 1.0E-04 2.7E-05 9.5E-05 2.0E-04AL-SCRP-TRANSPO-W

Mo-93 2.2E-03 2.4E-04 1.4E-03 6.4E-03 8.1E-06 8.8E-07 5.2E-06 2.4E-05AL-METL-SMOBJCT-N

Nb-93m 3.4E-04 3.7E-05 2.3E-04 1.1E-03 1.3E-06 1.4E-07 8.4E-07 4.0E-06AL-METL-SMOBJCT-N

Nb-94 1.3E+01 3.5E+00 1.2E+01 2.5E+01 4.9E-02 1.3E-02 4.5E-02 9.3E-02AL-SCRP-TRANSPO-W

Nb-95 5.8E+00 1.6E+00 5.3E+00 1.1E+01 2.2E-02 5.8E-03 2.0E-02 4.1E-02AL-SCRP-TRANSPO-W

Zr-95 5.8E+00 1.5E+00 5.3E+00 1.1E+01 2.2E-02 5.7E-03 2.0E-02 4.1E-02AL-SCRP-TRANSPO-W

Tc-99 7.2E-04 1.2E-04 5.0E-04 1.9E-03 2.7E-06 4.3E-07 1.8E-06 7.1E-06AL-METL-COOKWAR-N

Ru-103 3.7E+00 1.0E+00 3.4E+00 7.1E+00 1.4E-02 3.7E-03 1.3E-02 2.6E-02AL-SCRP-TRANSPO-W

Ru-106 1.7E+00 4.4E-01 1.5E+00 3.2E+00 6.2E-03 1.6E-03 5.7E-03 1.2E-02AL-SCRP-TRANSPO-W

Ag-108m 1.3E+01 3.4E+00 1.2E+01 2.5E+01 4.8E-02 1.3E-02 4.5E-02 9.2E-02AL-SCRP-TRANSPO-W

Cd-109 5.1E-03 8.3E-04 3.9E-03 1.4E-02 1.9E-05 3.1E-06 1.5E-05 5.1E-05AL-METL-COOKWAR-N
Section 6 Evaluation of Aluminum

Table 6.5 Aluminum recycle critical-group dose factors–surficial

(μSv/y per Bq/cm2

) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

6-27 NUREG-1640

Ag-110m 2.3E+01 6.0E+00 2.1E+01 4.3E+01 8.5E-02 2.2E-02 7.8E-02 1.6E-01AL-SCRP-TRANSPO-W

Sb-124 1.5E+01 3.9E+00 1.3E+01 2.8E+01 5.4E-02 1.4E-02 5.0E-02 1.0E-01AL-SCRP-TRANSPO-W

I-125 5.3E-03 1.4E-03 4.8E-03 1.0E-02 1.9E-05 5.1E-06 1.8E-05 3.7E-05AL-SCRP-TRANSPO-W

Sb-125 3.3E+00 8.7E-01 3.0E+00 6.2E+00 1.2E-02 3.2E-03 1.1E-02 2.3E-02AL-SCRP-TRANSPO-W

I-129 7.5E-03 6.1E-04 4.6E-03 2.5E-02 2.8E-05 2.3E-06 1.7E-05 9.1E-05AL-DROS-HANDLIN-N

I-131 2.0E+00 5.6E-01 1.9E+00 4.0E+00 7.5E-03 2.1E-03 6.9E-03 1.5E-02AL-SCRP-TRANSPO-W

Ba-133 2.3E+00 5.9E-01 2.1E+00 4.3E+00 8.3E-03 2.2E-03 7.7E-03 1.6E-02AL-SCRP-TRANSPO-W

Cs-134 1.3E+01 3.4E+00 1.2E+01 2.4E+01 4.8E-02 1.3E-02 4.4E-02 9.1E-02AL-SCRP-TRANSPO-W

Cs-137 5.0E+00 1.3E+00 4.6E+00 9.5E+00 1.8E-02 4.9E-03 1.7E-02 3.5E-02AL-SCRP-TRANSPO-W

Ce-141 2.2E-01 5.9E-02 2.0E-01 4.1E-01 8.1E-04 2.2E-04 7.4E-04 1.5E-03AL-SCRP-TRANSPO-W

Ce-144 2.7E-01 7.0E-02 2.5E-01 5.0E-01 9.8E-04 2.6E-04 9.1E-04 1.9E-03AL-SCRP-TRANSPO-W

Pm-147 2.2E-04 3.6E-05 1.7E-04 5.9E-04 8.2E-07 1.3E-07 6.2E-07 2.2E-06AL-SCRP-HANDLIN-W

Eu-152 9.0E+00 2.4E+00 8.3E+00 1.7E+01 3.3E-02 8.8E-03 3.1E-02 6.3E-02AL-SCRP-TRANSPO-W

Eu-154 9.8E+00 2.6E+00 9.1E+00 1.9E+01 3.6E-02 9.6E-03 3.4E-02 6.9E-02AL-SCRP-TRANSPO-W

Eu-155 8.6E-02 2.3E-02 7.9E-02 1.6E-01 3.2E-04 8.4E-05 2.9E-04 6.0E-04AL-SCRP-TRANSPO-W

Re-186 2.0E-02 5.5E-03 1.8E-02 4.2E-02 7.4E-05 2.1E-05 6.7E-05 1.6E-04AL-SCRP-TRANSPO-W

Ir-192 5.7E+00 1.5E+00 5.2E+00 1.1E+01 2.1E-02 5.6E-03 1.9E-02 4.0E-02AL-SCRP-TRANSPO-W

Pb-210 3.0E+00 4.5E-01 2.2E+00 8.1E+00 1.1E-02 1.7E-03 8.3E-03 3.0E-02AL-METL-COOKWAR-N

Po-210 2.9E-01 4.3E-02 2.2E-01 7.8E-01 1.1E-03 1.6E-04 8.1E-04 2.9E-03AL-METL-COOKWAR-N

Bi-210 2.5E-03 7.2E-04 2.3E-03 5.1E-03 9.3E-06 2.7E-06 8.6E-06 1.9E-05AL-SCRP-TRANSPO-W

Rn-222 6.9E+00 1.9E+00 6.3E+00 1.5E+01 2.6E-02 7.1E-03 2.3E-02 5.4E-02AL-SCRP-TRANSPO-W

Ra-223 1.5E+00 4.1E-01 1.3E+00 2.9E+00 5.4E-03 1.5E-03 4.9E-03 1.1E-02AL-SCRP-TRANSPO-W

Ra-224 4.9E+00 1.4E+00 4.5E+00 1.1E+01 1.8E-02 5.1E-03 1.7E-02 3.9E-02AL-SCRP-TRANSPO-W

Ac-225 1.1E+00 3.2E-01 1.0E+00 2.3E+00 4.2E-03 1.2E-03 3.9E-03 8.3E-03AL-SCRP-TRANSPO-W

Ra-225 3.9E-02 6.8E-03 2.9E-02 1.0E-01 1.4E-04 2.5E-05 1.1E-04 3.7E-04AL-SCRP-HANDLIN-W

Ra-226 1.4E+01 3.7E+00 1.3E+01 2.7E+01 5.2E-02 1.4E-02 4.8E-02 9.8E-02AL-SCRP-TRANSPO-W

Ac-227 7.6E+00 9.8E-01 5.8E+00 1.9E+01 2.8E-02 3.6E-03 2.2E-02 7.2E-02AL-METL-COOKWAR-N

Th-227 4.7E-01 1.3E-01 4.3E-01 9.1E-01 1.8E-03 4.8E-04 1.6E-03 3.4E-03AL-SCRP-TRANSPO-W

Th-228 1.0E+01 2.7E+00 9.5E+00 1.9E+01 3.8E-02 1.0E-02 3.5E-02 7.2E-02AL-SCRP-TRANSPO-W

Ra-228 6.8E+00 1.8E+00 6.3E+00 1.3E+01 2.5E-02 6.6E-03 2.3E-02 4.8E-02AL-SCRP-TRANSPO-W

Th-229 9.2E+00 1.3E+00 6.7E+00 2.5E+01 3.4E-02 4.6E-03 2.5E-02 9.3E-02AL-SCRP-HANDLIN-W

Th-230 1.4E+00 1.9E-01 1.0E+00 3.8E+00 5.1E-03 7.0E-04 3.8E-03 1.4E-02AL-SCRP-HANDLIN-W

Pa-231 5.9E+00 9.1E-01 4.3E+00 1.5E+01 2.2E-02 3.4E-03 1.6E-02 5.5E-02AL-METL-COOKWAR-N

Th-231 1.2E-03 1.8E-04 7.4E-04 4.0E-03 4.5E-06 6.6E-07 2.8E-06 1.5E-05AL-SCRP-TRANSPO-W

Th-232 6.1E+00 8.4E-01 4.5E+00 1.7E+01 2.3E-02 3.1E-03 1.7E-02 6.2E-02AL-SCRP-HANDLIN-W
Evaluation of Aluminum Section 6

Table 6.5 Aluminum recycle critical-group dose factors–surficial

(μSv/y per Bq/cm2

) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

NUREG-1640 6-28

Pa-233 1.1E+00 2.8E-01 9.8E-01 2.0E+00 3.9E-03 1.1E-03 3.6E-03 7.5E-03AL-SCRP-TRANSPO-W

U-233 7.2E-01 9.5E-02 5.2E-01 2.0E+00 2.6E-03 3.5E-04 1.9E-03 7.3E-03AL-SCRP-HANDLIN-W

Th-234 5.9E-02 1.6E-02 5.4E-02 1.1E-01 2.2E-04 5.8E-05 2.0E-04 4.1E-04AL-SCRP-TRANSPO-W

U-234 7.0E-01 9.3E-02 5.1E-01 1.9E+00 2.6E-03 3.4E-04 1.9E-03 7.1E-03AL-SCRP-HANDLIN-W

U-235 6.6E-01 1.7E-01 6.1E-01 1.3E+00 2.4E-03 6.4E-04 2.3E-03 4.6E-03AL-SCRP-TRANSPO-W

Np-237 2.9E+00 4.2E-01 2.2E+00 8.0E+00 1.1E-02 1.6E-03 8.0E-03 2.9E-02AL-SCRP-HANDLIN-W

Pu-238 1.5E+00 2.0E-01 1.1E+00 4.2E+00 5.6E-03 7.5E-04 4.1E-03 1.5E-02AL-SCRP-HANDLIN-W

U-238 6.3E-01 8.3E-02 4.6E-01 1.7E+00 2.3E-03 3.1E-04 1.7E-03 6.4E-03AL-SCRP-HANDLIN-W

Pu-239 1.6E+00 2.2E-01 1.2E+00 4.5E+00 6.0E-03 8.0E-04 4.4E-03 1.7E-02AL-SCRP-HANDLIN-W

Pu-240 1.6E+00 2.2E-01 1.2E+00 4.5E+00 6.0E-03 8.0E-04 4.4E-03 1.7E-02AL-SCRP-HANDLIN-W

Pu-241 2.6E-02 3.5E-03 1.9E-02 7.2E-02 9.7E-05 1.3E-05 7.0E-05 2.7E-04AL-SCRP-HANDLIN-W

Am-241 2.4E+00 3.4E-01 1.8E+00 6.5E+00 8.9E-03 1.3E-03 6.6E-03 2.4E-02AL-SCRP-HANDLIN-W

Cm-242 9.1E-02 1.3E-02 6.7E-02 2.5E-01 3.4E-04 4.7E-05 2.5E-04 9.3E-04AL-SCRP-HANDLIN-W

Pu-242 1.5E+00 2.1E-01 1.1E+00 4.2E+00 5.7E-03 7.6E-04 4.2E-03 1.6E-02AL-SCRP-HANDLIN-W

Cm-244 1.3E+00 1.9E-01 9.9E-01 3.6E+00 4.9E-03 7.0E-04 3.7E-03 1.4E-02AL-SCRP-HANDLIN-W

The calculation of derived surficial dose factors is probabilistic. The parameter SM is

represented by a distribution of values that incorporate the variability and uncertainty in the

surface-to-mass ratio of typical aluminum objects available for clearance. This additional source

of uncertainty results in wider confidence intervals for the surficial dose factors than for the

mass-based dose factors from which they are derived. The relative importance of this additional

uncertainty depends on the scenario. For scenarios with the narrowest confidence intervals, the

added uncertainty can contribute as much as an additional 50% to the width of the confidence

interval. The mass-based dose factor for the scrap transportation scenario has a 95/5 ratio of

about 2 for most radionuclides. The corresponding derived surficial dose factors have a 95/5

ratio of about 3. The added uncertainty in surface-to-mass ratio has a relatively smaller impact

on the confidence interval for scenarios with larger uncertainties, contributing an additional 10%

to 30%.
Section 7 Evaluation of Concrete

7-1 NUREG-1640

Seven potential exposure scenarios for cleared concrete debris that are realistically based on current

American industries are evaluated in this section. As in the evaluations for metals, concrete scenario

categories include handling and processing, transportation, product use, and disposal. Unique to the

concrete evaluation is the inclusion of a scenario involving a resident on the site of a closed landfill. A

radionuclide-specific, probabilistic dose factor distribution was calculated for the members of all

exposed groups. Dose factors for an average member of each critical group was calculated in the

same manner as for metals recycle. The mean dose factor for each critical group is reported in

normalized units of μSv/y per Bq/g scrap (mrem/y per pCi/g) and μSv/y per Bq/cm2 (mrem/y per

pCi/cm2 ) for each radionuclide. Dose factors at the 5th , 50th , and 95th percentiles are also reported.

Similar to the metals analyses, the most common critical group consists of commercial truck drivers

carrying cleared concrete debris, accounting for critical group designation for almost half (33) of the

85 radionuclides in the analysis. Unlike the metals analyses, the scenario involving a resident on a

closed landfill containing cleared concrete debris was analyzed and included in critical group

determination. This scenario accounts for critical group designation for one-third (28) of the

radionuclides in the analysis. Scenarios involving handling concrete debris accounted for most of the

remaining critical groups.

Mean critical-group dose factors range from a high of 7E+04 μSv/y per Bq/g (3E+02 mrem/y per

pCi/g) for Np-237 to a low of 3E-03 μSv/y per Bq/g (1.3E-05 mrem/y per pCi/g) for Fe-55. The surficial

mean critical-group dose factors range from 1.4E+03 μSv/y per Bq/cm2 (Np-237) down to 5E-05 μSv/y

per Bq/cm2 (S-35). The Np-237 highest mean dose factors are a factor of 30 higher than the next

highest mean dose factor. The high mean dose factor of Np-237 is the highest calculated for all

materials (metals and concrete) and is attributed to the drinking-water exposure pathway in a

residential scenario on the site of a closed landfill. Seventy-four of the radionuclide-specific, mean

dose factors for concrete critical groups are 270 μSv/y per Bq/g or lower (1 mrem/y per pCi/g). 

(9$/8$7,212)5(&<&/($1'',6326$/2)

&21&5(7(

This section describes the technical evaluation of the recycle and disposal of concrete debris that

could be cleared by Nuclear Regulatory Commission (NRC) licensed facilities. Similar to the

analyses of metal scrap (Sections 4, 5, and 6), the likely flow of cleared concrete was

probabilistically modeled, distributions of radionuclide concentrations in recycled products and

disposed materials were calculated, and potential doses to average members of potential critical

groups were estimated. 

,QWURGXFWLRQWR$QDO\VLV

The analysis process for calculating potential exposures from concrete recycle and disposal is

relatively simple when compared to the analyses conducted for recycled and disposed metals. A

simple material flow model specific to concrete recycle and disposal was developed, radioactivity

concentrations in reprocessed concrete were calculated, and scenario evaluations were conducted. 

In contrast to the metal analyses, the processing of concrete does not involve redistribution of

radionuclides, and there is only one resulting end product. The exposure scenario evaluations for

concrete are similar to those for the metals, with only several minor scenario parameter
Evaluation of Concrete Section 7

NUREG-1640 7-2

differences, and only one fundamentally different scenario is used in the determination of critical

groups (resident on a closed landfill site). 

)ORZRI5HF\FOHGDQG'LVSRVHG&RQFUHWH

The material flow model for concrete represents the general processes that concrete cleared by

NRC licensed facilities would go through from the time of clearance to the time of final disposal. 

Decontamination is assumed to have already taken place and is not included in the model. The

material flow model comprises two types of models: conceptual and mathematical. The

conceptual model describes the recycling process and defines the limits of this analysis, while the

mathematical model presents the mathematical equations that implement the information

presented in the conceptual model.

The material flow model is based largely on information gathered from personal communications

with individuals in the concrete recycling industry. It is intended to provide a defensible basis for

developing appropriate exposure scenarios for recycled concrete. In addition, the output of the

material flow model provides key input to the dose calculations for each scenario. This input

consists of radionuclide-specific concentrations in recycle products containing recycled concrete,

in effluents, and in waste products of the recycling process. Because of the number of scenarios

being analyzed and the differing times at which they occur, the mathematical model presented in

this section does not include radioactive decay. Like other materials, this is accounted for in the

scenario evaluations.

This section presents the conceptual model that follows the concrete through a typical recycling

process, beginning with cleared concrete debris, through the recycling process, product use, and

ending with disposal. Figure 7.1 presents a schematic diagram of the conceptual model of the

overall flow of recycled and disposed concrete. The modeling of both mass and radioactivity in

recycled concrete follow this flow model. As seen in Figure 7.1, there are several distinct steps

in the recycling process. Each of these are discussed separately in the following subsections.
Section 7 Evaluation of Concrete

7-3 NUREG-1640

Figure 7.1 Conceptual model of the overall flow of recycled and disposed concrete
Evaluation of Concrete Section 7

1

Recycle/Reuse Literature Search Report, SAIC, 1994 scheduled to be published as NUREG/CR-5610

2

Personal communication between M. Anderson, SAIC and J. Dykes, Dykes Paving and Construction Co., Inc.,

January 13, 1997.

NUREG-1640 7-4

6RXUFHRI0DWHULDO

Concrete for recycling comes mainly from commercial sources, which contributes concrete from

demolished buildings or parking lots. 

The main producer of concrete debris (scrap) for this analysis is the nuclear industry, which

consists mainly of commercial power plants, test and research reactors, and industrial nuclear

facilities. Other producers of concrete debris include the Department of Energy (DOE) weapons

complex and the Department of Defense (DOD), which could contribute concrete debris

primarily from conventional weapons testing and army and navy test reactors. 

Unlike the metals analyzed, concrete is more likely to be recycled only during the

decontamination and decommissioning (D&D) of a nuclear facility. This would result in a large

amount of concrete available for recycling during a very short period of time. The D&D of a

typical pressurized water reactor would result in about 180,000 t (198,000 tons), whereas

approximately 348,000 t (383,000 tons) would be available from a typical boiling water reactor

(NUREG/CR-56101

). Large masses of concrete could also be available during the D&D of nonreactor facilities.

7UDQVSRUWDWLRQDQG3URFHVVLQJ

Concrete debris cleared from a nuclear facility may be transported, usually by a commercial

company, to the processor. Processing could also occur at the origination site of the concrete

debris. The operations at both places are similar. Because not all concrete debris is likely to be

suitable for recycle, some would be transported directly to a disposal site. In both cases,

transportation would occur by truck. This transportation could occur either before or after

processing occurs.

Prior to use, concrete debris must be crushed and sorted. Any steel rebar in the concrete would

be removed with a magnet prior to crushing and sent to an iron and steel refinery. The concrete

must be in blocks approximately 1.5 x 1.5 x 0.8 m to be crushed. During crushing, water is

sprayed on the dust to contain it. Although not required by regulation, workers near the site

typically wear dust respirators. One major recycler of concrete, Dykes Paving & Construction

Co., Inc., recycles about 230,000 t (250,000 tons) of concrete per year.2

As soon as the concrete debris is needed after processing and crushing, it is transported by truck

to the site of the final use. 
Section 7 Evaluation of Concrete

1

 Personal communication between M. Anderson, SAIC and J. Dykes, Dykes Paving and Construction Co., Inc.,

January 13, 1997.

7-5 NUREG-1640

07 ' 0& % 0&$ 7.1

0DQXIDFWXULQJ

In order to prepare recycled, crushed concrete debris for final use, it is mixed with a small

amount of additives. The additives are added to promote adhesion. According to Dykes,1

 it is

very common for the final concrete end product to be made of entirely recycled concrete and

additives, although occasionally other aggregate is added to the recycled concrete. If the recycled

concrete is used just as aggregate, such as for the base of roadways, then there is no additional

processing after the crushing and sizing at the scrap dealer/processor.

3URGXFW8VH

Typical end products for recycled concrete include the base for roads, a stabilizer for asphalt, and

an aggregate for non-structural materials. Recycled concrete is not used as aggregate in structural

concrete, such as that used in houses or buildings.1

'LVSRVDO

The ultimate endpoint for some concrete is a public sanitary landfill (i.e., Resource Conservation

and Recovery Act (RCRA) Subtitle D landfill). Concrete debris that is not suitable for recycling

is sent directly to a landfill. Also, end products containing recycled concrete can also be sent to a

landfill after use.

0DWKHPDWLFDO0RGHOIRUWKH)ORZRI5HF\FOHG&RQFUHWH'HEULV

This section presents the equations that represent the information discussed previously in

Section 7.2 and are used to formulate the mathematical model

According to the material flow conceptual model, there is only one point at which the cleared

concrete debris radionuclide concentration is potentially changed: mixing with other concrete or

aggregate before or during recycling. Dilution with other concrete is radionuclide-independent. 

The following equations calculate the concentrations at points of interest (i.e., where scenarios

would occur). 

The total mass of material entering the recycling facility in a year, including cleared concrete

debris and other concrete/aggregate was calculated using Equation 7.1.

where
Evaluation of Concrete Section 7

NUREG-1640 7-6

&7 ' 0&

07

( && 7.2

MT = total mass of material entering the recycling facility in a year (g/y)

and

MC = mass of cleared concrete debris entering the recycling facility per year (g/y)

MCA = mass of other concrete debris/aggregate entering the recycling facility per year (g/y)

The radionuclide concentration in the recycled concrete entering the manufacturing process was

calculated using Equation 7.2. The following equations are intended to be evaluated separately

for each radionuclide in the analysis. Therefore, parameters such as radionuclide concentration,

decay factors, decay constants, and dose conversion factors are not explicitly subscripted for each

radionuclide. 

where

CT = radionuclide concentration in recycled concrete entering the manufacturing process

(pCi/g)

and

MC = mass of cleared concrete debris entering the recycling facility per year (g/y)

MT = total mass of material entering the recycling facility in a year (g/y)

CC = original radionuclide concentration of cleared concrete debris (pCi/g)

5DGLRDFWLYLW\&RQFHQWUDWLRQVLQ&RQFUHWH5HF\FOH3URGXFWV

Radioactivity concentrations in concrete recycle products are calculated using the models

described in the previous sections. The evaluation for concrete recycle and disposal assumes

some mixing of cleared concrete debris with other concrete debris. No mass or elemental

partitioning occurs during processing. Therefore, for a unit radionuclide concentration in cleared

concrete, the concentration in concrete recycle products would be the same for all radionuclides

and all scenarios except immediate handling or transport of cleared concrete.

The radioactivity concentrations that characterize the distribution calculated in the concrete

material flow model are listed in Table 7.1.

Table 7.1 Results of concrete material flow model

Radionuclide concentrations in recycled concrete

(Bq/g per Bq/g concrete debris)

Scenario Category Mean 5th 50th 95th

Large Objecta 8.7E-01 7.82E-01 8.83E-01 9.40E-01

Other Scenarios 9.71E-01 8.61E-01 9.93E-01 1.00E+00

a. The only concrete scenario using this set of radionuclide concentrations is CN-SCRP-LGMASS-N.
Section 7 Evaluation of Concrete

7-7 NUREG-1640

 

'RVH$VVHVVPHQWIRU&RQFUHWH5HF\FOHDQG'LVSRVDO

There are no scenarios in addition to those discussed for steel that are used for the evaluation of

concrete recycling and disposal. However, because landfill disposal of large masses of concrete

is more likely than for metals, a landfill resident scenario was included in the determination of

critical groups for concrete. For other scenarios, the analyses are the same as described for steel

recycle in Section 4, except for several parameter value differences. These are discussed in the

next section.

3DUDPHWHU'LVFXVVLRQ

Calculation of potential impacts from recycle of cleared concrete depends on many parameter

values. Parameter values are needed for both material flow and dose assessment models. The

material flow parameter values rely on information from the concrete recycling industry. The

parameter values for the dose modeling are a function of receptor behavior, such as time on a

specific job or breathing rate, as well as how the radionuclides are transported in the

environment. The dose modeling parameter values used for evaluation of concrete recycling and

disposal are generally the same as those used in the iron and steel modeling. Only those

parameter values that are different than those used in the iron and steel modeling are discussed in

this section. 

6FHQDULR7LPLQJ

As described previously, all exposure scenarios were derived from the material flow conceptual

modeling, and scenarios were assumed to occur at specific points in time following clearance

from the NRC licensed facility. In order to incorporate radioactive decay between clearance and

scenario dose modeling, the specific times were quantified as described in this section. Where a

reference was used as a basis for the assumed time period, it is cited. If no citation is given,

general knowledge of practices gained from talking with industry personnel combined with

professional judgement was used as the basis. The following is a list of basic assumptions that

were used in developing the timing of the concrete recycle scenarios:

Scrap Handling:

• All scrap concrete is assumed to be initially taken to a scrap processor. It takes

approximately 4 days for the scrap concrete to reach the scrap dealer.

Refining and Processing:

• The scrap concrete remains at the scrap processor for a period of approximately 7 days

prior to use or disposal.
Evaluation of Concrete Section 7

NUREG-1640 7-8

Use and Disposal:

• A recycled concrete product is used for 30 years, based on an assumed use in the

construction industry.

Post Disposal:

• A sanitary landfill operates for 40 years.

• Disposed items are placed in the landfill at the midpoint of the landfill operating period.

• Post-closure monitoring of landfills is done for 30 years.

• A disposal site is released for potential residential use after post-closure monitoring ends.

Specific scenario timing values are listed in Appendix B, Table B.15.

'RVH(YDOXDWLRQ

This section presents a discussion of parameter values used for the analysis of concrete recycle

scenarios. The analysis of seven concrete scenarios is based on the scenario descriptions

provided in the steel analysis (section 4). Similar scenarios are analyzed using the same models

as for the steel recycle analysis. Values used for many of the parameters are also the same as for

the steel recycle analysis. For some parameters, however, values specific to the recycle of

concrete were used in order to more appropriately model the scenarios as they would likely occur

for concrete recycle. The following discussion is limited to these specific parameter values. If a

parameter is not discussed below and listed in Table B.15, the same value as used for the steel

evaluation (Table B.7) is used for concrete.

,QSXW&RQFHQWUDWLRQVIURPWKH0DWHULDO)ORZ

The undecayed radionuclide concentration in the source material, Cx, is used as the source

material input concentration for scenario evaluations. For concrete recycling, this parameter is

radionuclide-independent and is calculated in the material flow modeling. Representative values

from the input concentration are listed in Table 7.1. 

([WHUQDO([SRVXUH3DUDPHWHUV

The only unique parameter value used for evaluation of the external pathway for concrete recycle

is the density of concrete, for which a fixed value of 2.33E+6 g/m3

 was used.

&RQFUHWH6XUIDFHWR0DVV5DWLR

The surface-to-mass ratio for concrete is representative of concrete slabs (e.g., floors and walls)

with residual radioactivity on only one side. The surface-to-mass ratio is not sensitive to the size

of the pieces made from these slabs but is sensitive to the original thickness of the slabs. The

surface-to-mass ratio is also dependent on the density of concrete. 
Section 7 Evaluation of Concrete

7-9 NUREG-1640

The typical thickness of wall and floor slabs is assumed to range from 15 to 46 cm (6 to 18 in). 

Concrete for normal construction purposes ranges in density from 1.6 to 3.2 g/cm3

 (100 to 200

lb/ft3) (Chen, 1995). Data are not available to provide an adequate basis for choosing a “best

estimate” for either thickness or density of concrete slabs at NRC licensees. Based on these data

and assumptions, the value of the parameter SM for concrete is best described by a uniform

distribution with a minimum of 0.007 cm2

/g and a maximum of 0.04 cm2/g. The minimum value

corresponds to a thick slab of high-density, e.g., a 46 cm (18 in) slab with a density of 3.2 g/cm3

(200 lb/ft3). The maximum value corresponds to a thin slab of low density, e.g., a 15 cm (6 in)

slab with a density of 3.2 g/cm3

 (100 lb/ft3).

'RVH)DFWRUVIRU&RQFUHWH5HF\FOHDQG'LVSRVDO

This analysis of recycle of cleared concrete scrap includes 7 separate scenarios evaluated for 85

radionuclides. Figure 7.2 shows which scenarios describe the critical groups and for how many

radionuclides. There are four scenarios which have the highest dose factor for at least one

radionuclide. The largest number of radionuclides have critical groups described by scenarios

associated with transporting (33 radionuclides) or handling (14 radionuclides) unprocessed

debris. Individuals engaged in roadbed construction activities using cleared concrete scrap

constitute the critical group for 10 radionuclides. For 28 radionuclides, the critical group consists

of individuals residing on closed landfills containing buried concrete scrap. Table 7.2 lists the

limiting mass-based dose factors for each radionuclide. Table 7.3 lists the corresponding derived

surficial dose factors for each radionuclide. Results for all 7 concrete scenarios are tabulated in

Appendix I. 

The mean values of the critical-group dose factors for each radionuclide are listed in Table 7.2 as

the “critical-group dose factor.” These represent the dose to the average member of the critical

group exposed to radioactivity distributed throughout the mass of cleared concrete (Bq/g or

pCi/g). The circumstances of that exposure are described by the scenario indicated in the right

hand column. The 5th, 50th, and 95th percentiles listed for each radionuclide represent the

underlying distribution of dose factors calculated for each critical group. The range of values

from the 5th to the 95th percentile is the 90% confidence interval on the dose factor. That is, there

is a 90% certainty that the dose factor for the average member of the critical group lies within

this interval. The confidence interval is a subjective measure of uncertainty in the dose factor

that includes estimates of the variability and uncertainty in the parameters used in each scenario.
Evaluation of Concrete Section 7

NUREG-1640 7-10

Concrete Debris Transport

Resident on Closed Landfill

Handling Concrete Debris

Roadbed Construction Activities

33

10

14

28

0

5

10

15

20

25

30

35

Number of Radionuclides

Concrete Critical Group Scenarios

Figure 7.2 Scenarios describing critical groups for concrete recycle
Section 7 Evaluation of Concrete

7-11 NUREG-1640

Table 7.2 Concrete recycle critical-group dose factors—mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

H-3 8.8E-03 9.9E-06 5.0E-04 3.9E-02 3.3E-05 3.7E-08 1.9E-06 1.5E-04CN-SCRP-LANDFIL-N

C-14 1.6E+01 2.7E-02 1.1E+00 5.7E+01 5.9E-02 1.0E-04 4.1E-03 2.1E-01CN-SCRP-LANDFIL-N

Na-22 2.2E+02 1.4E+02 2.2E+02 3.0E+02 8.1E-01 5.3E-01 8.1E-01 1.1E+00CN-SCRP-TRANSPO-W

P-32 1.4E-01 8.6E-02 1.4E-01 1.9E-01 5.1E-04 3.2E-04 5.0E-04 7.2E-04CN-SCRP-TRANSPO-W

S-35 3.5E-03 1.5E-03 3.3E-03 6.2E-03 1.3E-05 5.4E-06 1.2E-05 2.3E-05CN-SCRP-HANDLIN-W

Cl-36 1.6E+02 1.0E+00 1.9E+01 5.4E+02 5.9E-01 3.9E-03 6.9E-02 2.0E+00CN-SCRP-LANDFIL-N

K-40 4.7E+01 1.9E-01 5.7E+00 2.2E+02 1.7E-01 6.9E-04 2.1E-02 8.2E-01CN-SCRP-LANDFIL-N

Ca-41 4.8E+00 1.4E-02 4.6E-01 1.9E+01 1.8E-02 5.2E-05 1.7E-03 7.0E-02CN-SCRP-LANDFIL-N

Ca-45 1.8E-02 6.4E-03 1.7E-02 3.4E-02 6.7E-05 2.4E-05 6.2E-05 1.3E-04CN-SCRP-HANDLIN-W

Cr-51 2.5E+00 1.6E+00 2.5E+00 3.5E+00 9.4E-03 5.9E-03 9.2E-03 1.3E-02CN-SCRP-TRANSPO-W

Mn-54 8.5E+01 5.6E+01 8.4E+01 1.2E+02 3.2E-01 2.1E-01 3.1E-01 4.4E-01CN-SCRP-TRANSPO-W

Fe-55 3.4E-03 1.1E-03 3.2E-03 6.5E-03 1.3E-05 4.2E-06 1.2E-05 2.4E-05CN-SCRP-HANDLIN-W

Co-57 6.6E+00 1.4E+00 5.9E+00 1.3E+01 2.4E-02 5.3E-03 2.2E-02 5.0E-02CN-SCRP-ROADBED-W

Co-58 9.6E+01 6.2E+01 9.5E+01 1.3E+02 3.5E-01 2.3E-01 3.5E-01 4.9E-01CN-SCRP-TRANSPO-W

Fe-59 1.2E+02 7.4E+01 1.2E+02 1.6E+02 4.3E-01 2.8E-01 4.3E-01 6.0E-01CN-SCRP-TRANSPO-W

Ni-59 7.4E-03 1.8E-05 8.1E-04 3.0E-02 2.7E-05 6.8E-08 3.0E-06 1.1E-04CN-SCRP-LANDFIL-N

Co-60 2.5E+02 1.7E+02 2.5E+02 3.5E+02 9.4E-01 6.1E-01 9.3E-01 1.3E+00CN-SCRP-TRANSPO-W

Ni-63 1.0E-02 2.7E-05 1.0E-03 3.8E-02 3.7E-05 1.0E-07 3.7E-06 1.4E-04CN-SCRP-LANDFIL-N

Zn-65 6.0E+01 3.9E+01 5.9E+01 8.3E+01 2.2E-01 1.4E-01 2.2E-01 3.1E-01CN-SCRP-TRANSPO-W

Cu-67 2.9E+00 1.1E+00 2.5E+00 5.6E+00 1.1E-02 3.9E-03 9.2E-03 2.1E-02CN-SCRP-TRANSPO-W

Se-75 2.5E+01 5.5E+00 2.3E+01 5.2E+01 9.3E-02 2.0E-02 8.4E-02 1.9E-01CN-SCRP-ROADBED-W

Sr-85 4.7E+01 3.0E+01 4.7E+01 6.6E+01 1.8E-01 1.1E-01 1.7E-01 2.4E-01CN-SCRP-TRANSPO-W

Sr-89 1.4E-01 5.3E-02 1.3E-01 2.7E-01 5.3E-04 1.9E-04 4.8E-04 9.8E-04CN-SCRP-ROADBED-W

Sr-90 2.2E+00 3.0E-03 1.3E-01 7.6E+00 8.3E-03 1.1E-05 4.8E-04 2.8E-02CN-SCRP-LANDFIL-N

Y-91 4.3E-01 1.2E-01 3.9E-01 8.7E-01 1.6E-03 4.6E-04 1.4E-03 3.2E-03CN-SCRP-ROADBED-W

Mo-93 3.8E+01 9.9E-02 3.5E+00 1.6E+02 1.4E-01 3.7E-04 1.3E-02 6.1E-01CN-SCRP-LANDFIL-N

Nb-93m 2.0E-02 7.8E-03 1.8E-02 4.2E-02 7.5E-05 2.9E-05 6.7E-05 1.6E-04CN-SCRP-HANDLIN-W

Nb-94 2.9E+02 4.4E-01 2.1E+01 1.1E+03 1.1E+00 1.6E-03 7.9E-02 3.9E+00CN-SCRP-LANDFIL-N

Nb-95 7.4E+01 4.7E+01 7.3E+01 1.0E+02 2.7E-01 1.7E-01 2.7E-01 3.8E-01CN-SCRP-TRANSPO-W

Zr-95 7.3E+01 4.7E+01 7.2E+01 1.0E+02 2.7E-01 1.7E-01 2.7E-01 3.7E-01CN-SCRP-TRANSPO-W

Tc-99 1.2E+02 8.8E-01 1.8E+01 4.6E+02 4.4E-01 3.3E-03 6.7E-02 1.7E+00CN-SCRP-LANDFIL-N

Ru-103 4.7E+01 3.0E+01 4.7E+01 6.6E+01 1.7E-01 1.1E-01 1.7E-01 2.4E-01CN-SCRP-TRANSPO-W

Ru-106 2.1E+01 1.3E+01 2.0E+01 2.9E+01 7.6E-02 5.0E-02 7.6E-02 1.1E-01CN-SCRP-TRANSPO-W

Ag-108m 1.7E+02 2.3E-01 1.2E+01 7.4E+02 6.4E-01 8.6E-04 4.4E-02 2.7E+00CN-SCRP-LANDFIL-N

Cd-109 2.5E-01 8.8E-02 2.3E-01 4.7E-01 9.2E-04 3.2E-04 8.5E-04 1.7E-03CN-SCRP-ROADBED-W
Evaluation of Concrete Section 7

Table 7.2 Concrete recycle critical-group dose factors—mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

NUREG-1640 7-12

Ag-110m 2.8E+02 1.8E+02 2.8E+02 3.9E+02 1.0E+00 6.8E-01 1.0E+00 1.4E+00CN-SCRP-TRANSPO-W

Sb-124 1.8E+02 1.2E+02 1.8E+02 2.5E+02 6.8E-01 4.3E-01 6.7E-01 9.3E-01CN-SCRP-TRANSPO-W

I-125 3.0E-01 1.1E-01 2.9E-01 5.8E-01 1.1E-03 4.1E-04 1.1E-03 2.2E-03CN-SCRP-ROADBED-W

Sb-125 4.1E+01 2.6E+01 4.0E+01 5.6E+01 1.5E-01 9.8E-02 1.5E-01 2.1E-01CN-SCRP-TRANSPO-W

I-129 2.4E+03 1.5E+01 2.6E+02 8.4E+03 8.9E+00 5.4E-02 9.6E-01 3.1E+01CN-SCRP-LANDFIL-N

I-131 2.8E+01 1.6E+01 2.7E+01 4.0E+01 1.0E-01 5.9E-02 1.0E-01 1.5E-01CN-SCRP-TRANSPO-W

Ba-133 2.8E+01 1.8E+01 2.8E+01 3.9E+01 1.0E-01 6.7E-02 1.0E-01 1.4E-01CN-SCRP-TRANSPO-W

Cs-134 1.6E+02 1.0E+02 1.6E+02 2.2E+02 5.9E-01 3.9E-01 5.9E-01 8.2E-01CN-SCRP-TRANSPO-W

Cs-137 6.2E+01 4.0E+01 6.1E+01 8.5E+01 2.3E-01 1.5E-01 2.3E-01 3.2E-01CN-SCRP-TRANSPO-W

Ce-141 3.4E+00 7.5E-01 3.1E+00 7.1E+00 1.3E-02 2.8E-03 1.2E-02 2.6E-02CN-SCRP-ROADBED-W

Ce-144 3.3E+00 2.1E+00 3.3E+00 4.6E+00 1.2E-02 7.9E-03 1.2E-02 1.7E-02CN-SCRP-TRANSPO-W

Pm-147 2.8E-02 1.1E-02 2.5E-02 5.7E-02 1.0E-04 3.9E-05 9.3E-05 2.1E-04CN-SCRP-HANDLIN-W

Eu-152 1.1E+02 7.2E+01 1.1E+02 1.5E+02 4.1E-01 2.7E-01 4.1E-01 5.7E-01CN-SCRP-TRANSPO-W

Eu-154 1.2E+02 7.9E+01 1.2E+02 1.7E+02 4.5E-01 2.9E-01 4.4E-01 6.2E-01CN-SCRP-TRANSPO-W

Eu-155 2.5E+00 5.6E-01 2.3E+00 5.0E+00 9.1E-03 2.1E-03 8.3E-03 1.9E-02CN-SCRP-ROADBED-W

Re-186 3.1E-01 1.4E-01 2.8E-01 5.2E-01 1.1E-03 5.3E-04 1.0E-03 1.9E-03CN-SCRP-TRANSPO-W

Ir-192 7.2E+01 4.6E+01 7.1E+01 9.9E+01 2.6E-01 1.7E-01 2.6E-01 3.7E-01CN-SCRP-TRANSPO-W

Pb-210 1.1E+01 2.9E+01 5.9E+01 5.9E+01 1.2E-01 4.0E-02 1.1E-01 2.2E-01CN-SCRP-HANDLIN-W

Po-210 4.9E+00 1.2E+01 2.4E+01 2.4E+01 4.9E-02 1.8E-02 4.5E-02 8.7E-02CN-SCRP-HANDLIN-W

Bi-210 9.9E-02 4.3E-02 9.0E-02 1.9E-01 3.7E-04 1.6E-04 3.3E-04 7.0E-04CN-SCRP-HANDLIN-W

Rn-222 1.1E+02 5.0E+01 9.7E+01 1.8E+02 3.9E-01 1.8E-01 3.6E-01 6.6E-01CN-SCRP-TRANSPO-W

Ra-223 1.9E+01 1.2E+01 1.9E+01 2.8E+01 7.1E-02 4.3E-02 7.0E-02 1.0E-01CN-SCRP-TRANSPO-W

Ra-224 7.6E+01 3.6E+01 7.0E+01 1.3E+02 2.8E-01 1.3E-01 2.6E-01 4.9E-01CN-SCRP-TRANSPO-W

Ac-225 1.5E+01 9.1E+00 1.5E+01 2.2E+01 5.7E-02 3.4E-02 5.6E-02 8.1E-02CN-SCRP-TRANSPO-W

Ra-225 5.2E+00 2.0E+00 4.8E+00 1.0E+01 1.9E-02 7.4E-03 1.8E-02 3.9E-02CN-SCRP-HANDLIN-W

Ra-226 5.3E+02 1.2E+00 5.0E+01 2.1E+03 2.0E+00 4.4E-03 1.9E-01 7.7E+00CN-SCRP-LANDFIL-N

Ac-227 8.4E+02 3.0E+02 7.4E+02 1.8E+03 3.1E+00 1.1E+00 2.7E+00 6.6E+00CN-SCRP-HANDLIN-W

Th-227 1.1E+01 4.8E+00 1.0E+01 2.1E+01 4.1E-02 1.8E-02 3.7E-02 7.9E-02CN-SCRP-HANDLIN-W

Th-228 2.7E+02 9.7E+01 2.5E+02 4.9E+02 9.9E-01 3.6E-01 9.2E-01 1.8E+00CN-SCRP-ROADBED-W

Ra-228 8.9E+01 2.7E+01 8.1E+01 1.8E+02 3.3E-01 9.8E-02 3.0E-01 6.5E-01CN-SCRP-ROADBED-W

Th-229 1.4E+03 1.8E+00 1.0E+02 4.3E+03 5.0E+00 6.5E-03 3.7E-01 1.6E+01CN-SCRP-LANDFIL-N

Th-230 2.2E+02 2.9E-01 1.6E+01 6.9E+02 8.2E-01 1.1E-03 6.0E-02 2.6E+00CN-SCRP-LANDFIL-N

Pa-231 2.1E+03 3.4E+00 1.8E+02 6.7E+03 7.7E+00 1.2E-02 6.6E-01 2.5E+01CN-SCRP-LANDFIL-N

Th-231 3.9E-02 3.5E-03 2.1E-02 1.3E-01 1.5E-04 1.3E-05 7.9E-05 4.6E-04CN-SCRP-TRANSPO-W

Th-232 1.3E+03 1.9E+00 1.1E+02 4.6E+03 4.9E+00 6.9E-03 3.9E-01 1.7E+01CN-SCRP-LANDFIL-N
Section 7 Evaluation of Concrete

Table 7.2 Concrete recycle critical-group dose factors—mass

(μSv/y per Bq/g) (mrem/y per pCi/g)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

7-13 NUREG-1640

Pa-233 1.4E+01 8.6E+00 1.3E+01 1.9E+01 5.0E-02 3.2E-02 5.0E-02 7.0E-02CN-SCRP-TRANSPO-W

U-233 1.7E+02 6.8E-01 1.7E+01 6.0E+02 6.1E-01 2.5E-03 6.3E-02 2.2E+00CN-SCRP-LANDFIL-N

Th-234 7.5E-01 4.7E-01 7.4E-01 1.0E+00 2.8E-03 1.7E-03 2.7E-03 3.9E-03CN-SCRP-TRANSPO-W

U-234 1.7E+02 4.0E-01 1.6E+01 6.5E+02 6.2E-01 1.5E-03 6.1E-02 2.4E+00CN-SCRP-LANDFIL-N

U-235 1.4E+02 5.1E-01 1.8E+01 6.1E+02 5.2E-01 1.9E-03 6.7E-02 2.2E+00CN-SCRP-LANDFIL-N

Np-237 7.1E+04 9.0E+01 4.0E+03 2.2E+05 2.6E+02 3.3E-01 1.5E+01 8.0E+02CN-SCRP-LANDFIL-N

Pu-238 1.7E+02 5.4E+01 1.5E+02 3.8E+02 6.4E-01 2.0E-01 5.6E-01 1.4E+00CN-SCRP-HANDLIN-W

U-238 1.3E+02 4.0E-01 1.5E+01 5.7E+02 4.8E-01 1.5E-03 5.5E-02 2.1E+00CN-SCRP-LANDFIL-N

Pu-239 2.2E+02 2.8E-01 1.6E+01 7.1E+02 8.3E-01 1.0E-03 5.8E-02 2.6E+00CN-SCRP-LANDFIL-N

Pu-240 2.2E+02 2.7E-01 1.5E+01 7.1E+02 8.2E-01 1.0E-03 5.7E-02 2.6E+00CN-SCRP-LANDFIL-N

Pu-241 1.7E+01 2.1E-02 8.9E-01 7.2E+01 6.4E-02 7.6E-05 3.3E-03 2.7E-01CN-SCRP-LANDFIL-N

Am-241 3.3E+02 4.2E-01 2.3E+01 1.1E+03 1.2E+00 1.6E-03 8.7E-02 3.9E+00CN-SCRP-LANDFIL-N

Cm-242 1.1E+01 3.6E+00 9.3E+00 2.3E+01 3.9E-02 1.3E-02 3.4E-02 8.5E-02CN-SCRP-HANDLIN-W

Pu-242 2.1E+02 2.7E-01 1.5E+01 6.8E+02 7.9E-01 9.8E-04 5.7E-02 2.5E+00CN-SCRP-LANDFIL-N

Cm-244 1.6E+02 5.5E+01 1.4E+02 3.4E+02 5.8E-01 2.0E-01 5.1E-01 1.2E+00CN-SCRP-HANDLIN-W
Evaluation of Concrete Section 7

NUREG-1640 7-14

Table 7.3 Concrete recycle critical-group dose factors—surficial

(μSv/y per Bq/cm2

) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

H-3 1.9E-04 1.9E-07 1.1E-05 7.9E-04 7.1E-07 7.1E-10 4.0E-08 2.9E-06 CN-SCRP-LANDFIL-N

C-14 3.7E-01 6.4E-04 2.4E-02 1.2E+00 1.4E-03 2.4E-06 8.9E-05 4.6E-03 CN-SCRP-LANDFIL-N

Na-22 3.2E+00 1.8E+00 5.0E+00 1.0E+01 1.9E-02 6.7E-03 1.8E-02 3.7E-02 CN-SCRP-TRANSPO-W

P-32 5.2E-03 1.1E-03 3.1E-03 6.1E-03 1.2E-05 4.1E-06 1.1E-05 2.3E-05 CN-SCRP-TRANSPO-W

S-35 5.3E-05 1.4E-05 4.4E-05 1.2E-04 2.0E-07 5.1E-08 1.6E-07 4.3E-07 CN-SCRP-ROADBED-W

Cl-36 3.2E+00 1.8E-02 3.9E-01 1.2E+01 1.2E-02 6.7E-05 1.5E-03 4.4E-02 CN-SCRP-LANDFIL-N

K-40 1.1E+00 4.0E-03 1.3E-01 5.5E+00 4.0E-03 1.5E-05 4.7E-04 2.0E-02 CN-SCRP-LANDFIL-N

Ca-41 1.2E-01 3.2E-04 9.7E-03 4.7E-01 4.3E-04 1.2E-06 3.6E-05 1.7E-03 CN-SCRP-LANDFIL-N

Ca-45 4.2E-04 9.5E-05 3.6E-04 1.0E-03 1.6E-06 3.5E-07 1.3E-06 3.7E-06 CN-SCRP-HANDLIN-W

Cr-51 6.0E-02 2.1E-02 5.7E-02 1.1E-01 2.2E-04 7.6E-05 2.1E-04 4.2E-04 CN-SCRP-TRANSPO-W

Mn-54 2.0E+00 7.0E-01 1.9E+00 3.9E+00 7.4E-03 2.6E-03 7.1E-03 1.4E-02 CN-SCRP-TRANSPO-W

Fe-55 8.0E-05 1.7E-05 6.7E-05 1.9E-04 3.0E-07 6.3E-08 2.5E-07 7.1E-07 CN-SCRP-HANDLIN-W

Co-57 1.5E-01 2.6E-02 1.2E-01 3.9E-01 5.7E-04 9.5E-05 4.5E-04 1.4E-03 CN-SCRP-ROADBED-W

Co-58 2.3E+00 7.9E-01 2.1E+00 4.4E+00 8.4E-03 2.9E-03 7.9E-03 1.6E-02 CN-SCRP-TRANSPO-W

Fe-59 2.7E+00 9.6E-01 2.6E+00 5.3E+00 1.0E-02 3.5E-03 9.7E-03 2.0E-02 CN-SCRP-TRANSPO-W

Ni-59 1.8E-04 3.9E-07 1.6E-05 6.9E-04 6.5E-07 1.4E-09 6.0E-08 2.6E-06 CN-SCRP-LANDFIL-N

Co-60 6.0E+00 2.1E+00 5.7E+00 1.2E+01 2.2E-02 7.7E-03 2.1E-02 4.3E-02 CN-SCRP-TRANSPO-W

Ni-63 2.4E-04 5.4E-07 2.2E-05 9.0E-04 8.8E-07 2.0E-09 8.2E-08 3.3E-06 CN-SCRP-LANDFIL-N

Zn-65 1.4E+00 5.0E-01 1.3E+00 2.7E+00 5.2E-03 1.8E-03 5.0E-03 1.0E-02 CN-SCRP-TRANSPO-W

Cu-67 6.8E-02 1.6E-02 5.7E-02 1.6E-01 2.5E-04 6.1E-05 2.1E-04 5.9E-04 CN-SCRP-TRANSPO-W

Se-75 5.9E-01 9.8E-02 4.6E-01 1.5E+00 2.2E-03 3.6E-04 1.7E-03 5.5E-03 CN-SCRP-ROADBED-W

Sr-85 1.1E+00 3.9E-01 1.1E+00 2.2E+00 4.1E-03 1.4E-03 3.9E-03 8.0E-03 CN-SCRP-TRANSPO-W

Sr-89 3.3E-03 8.4E-04 2.7E-03 7.6E-03 1.2E-05 3.1E-06 9.9E-06 2.8E-05 CN-SCRP-ROADBED-W

Sr-90 5.5E-02 5.5E-05 2.6E-03 1.6E-01 2.0E-04 2.0E-07 9.7E-06 6.0E-04 CN-SCRP-LANDFIL-N

Y-91 1.0E-02 2.1E-03 7.8E-03 2.5E-02 3.7E-05 7.8E-06 2.9E-05 9.2E-05 CN-SCRP-ROADBED-W

Mo-93 8.5E-01 2.3E-03 6.7E-02 3.3E+00 3.1E-03 8.5E-06 2.5E-04 1.2E-02 CN-SCRP-LANDFIL-N

Nb-93m 4.7E-04 1.3E-04 4.0E-04 1.1E-03 1.8E-06 4.8E-07 1.5E-06 4.0E-06 CN-SCRP-HANDLIN-W

Nb-94 7.3E+00 8.4E-03 4.6E-01 2.5E+01 2.7E-02 3.1E-05 1.7E-03 9.3E-02 CN-SCRP-LANDFIL-N

Nb-95 1.7E+00 6.0E-01 1.7E+00 3.4E+00 6.4E-03 2.2E-03 6.2E-03 1.2E-02 CN-SCRP-TRANSPO-W

Zr-95 1.7E+00 6.0E-01 1.6E+00 3.3E+00 6.3E-03 2.2E-03 6.0E-03 1.2E-02 CN-SCRP-TRANSPO-W

Tc-99 2.6E+00 1.9E-02 4.1E-01 9.5E+00 9.5E-03 7.1E-05 1.5E-03 3.5E-02 CN-SCRP-LANDFIL-N

Ru-103 1.1E+00 3.9E-01 1.1E+00 2.2E+00 4.1E-03 1.4E-03 3.9E-03 8.0E-03 CN-SCRP-TRANSPO-W

Ru-106 4.9E-01 1.7E-01 4.7E-01 9.4E-01 1.8E-03 6.3E-04 1.7E-03 3.5E-03 CN-SCRP-TRANSPO-W

Ag-108m 4.3E+00 5.0E-03 2.5E-01 1.4E+01 1.6E-02 1.9E-05 9.2E-04 5.1E-02 CN-SCRP-LANDFIL-N

Cd-109 5.8E-03 1.4E-03 4.6E-03 1.4E-02 2.2E-05 5.2E-06 1.7E-05 5.1E-05 CN-SCRP-ROADBED-W
Section 7 Evaluation of Concrete

Table 7.3 Concrete recycle critical-group dose factors—surficial

(μSv/y per Bq/cm2

) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

7-15 NUREG-1640

Ag-110m 6.7E+00 2.3E+00 6.4E+00 1.3E+01 2.5E-02 8.7E-03 2.4E-02 4.8E-02 CN-SCRP-TRANSPO-W

Sb-124 4.3E+00 1.5E+00 4.1E+00 8.3E+00 1.6E-02 5.6E-03 1.5E-02 3.1E-02 CN-SCRP-TRANSPO-W

I-125 7.1E-03 1.9E-03 6.0E-03 1.6E-02 2.6E-05 6.9E-06 2.2E-05 5.9E-05 CN-SCRP-ROADBED-W

Sb-125 9.6E-01 3.3E-01 9.2E-01 1.8E+00 3.5E-03 1.2E-03 3.4E-03 6.8E-03 CN-SCRP-TRANSPO-W

I-129 5.1E+01 2.9E-01 5.3E+00 2.0E+02 1.9E-01 1.1E-03 2.0E-02 7.6E-01 CN-SCRP-LANDFIL-N

I-131 6.5E-01 2.1E-01 6.1E-01 1.3E+00 2.4E-03 7.7E-04 2.2E-03 4.6E-03 CN-SCRP-TRANSPO-W

Ba-133 6.6E-01 2.3E-01 6.3E-01 1.3E+00 2.4E-03 8.5E-04 2.3E-03 4.7E-03 CN-SCRP-TRANSPO-W

Cs-134 3.8E+00 1.3E+00 3.6E+00 7.2E+00 1.4E-02 4.9E-03 1.3E-02 2.7E-02 CN-SCRP-TRANSPO-W

Cs-137 1.5E+00 5.1E-01 1.4E+00 2.8E+00 5.4E-03 1.9E-03 5.1E-03 1.0E-02 CN-SCRP-TRANSPO-W

Ce-141 8.0E-02 1.3E-02 6.2E-02 2.1E-01 3.0E-04 4.8E-05 2.3E-04 7.6E-04 CN-SCRP-ROADBED-W

Ce-144 7.8E-02 2.7E-02 7.4E-02 1.5E-01 2.9E-04 1.0E-04 2.7E-04 5.5E-04 CN-SCRP-TRANSPO-W

Pm-147 4.4E-04 1.0E-04 3.6E-04 1.2E-03 1.6E-06 3.8E-07 1.3E-06 4.3E-06 CN-SCRP-ROADBED-W

Eu-152 2.6E+00 9.1E-01 2.5E+00 5.0E+00 9.7E-03 3.4E-03 9.3E-03 1.9E-02 CN-SCRP-TRANSPO-W

Eu-154 2.9E+00 1.0E+00 2.7E+00 5.5E+00 1.1E-02 3.7E-03 1.0E-02 2.0E-02 CN-SCRP-TRANSPO-W

Eu-155 5.8E-02 9.9E-03 4.5E-02 1.5E-01 2.1E-04 3.7E-05 1.7E-04 5.4E-04 CN-SCRP-ROADBED-W

Re-186 7.2E-03 2.0E-03 6.4E-03 1.5E-02 2.7E-05 7.3E-06 2.4E-05 5.7E-05 CN-SCRP-TRANSPO-W

Ir-192 1.7E+00 5.9E-01 1.6E+00 3.3E+00 6.2E-03 2.2E-03 5.9E-03 1.2E-02 CN-SCRP-TRANSPO-W

Pb-210 1.6E-01 6.2E-01 1.7E+00 1.7E+00 2.7E-03 5.9E-04 2.3E-03 6.4E-03 CN-SCRP-HANDLIN-W

Po-210 7.4E-02 2.6E-01 6.9E-01 6.9E-01 1.1E-03 2.7E-04 9.7E-04 2.5E-03 CN-SCRP-HANDLIN-W

Bi-210 2.3E-03 6.6E-04 2.0E-03 5.2E-03 8.6E-06 2.5E-06 7.3E-06 1.9E-05 CN-SCRP-HANDLIN-W

Rn-222 2.5E+00 6.8E-01 2.2E+00 5.3E+00 9.2E-03 2.5E-03 8.3E-03 2.0E-02 CN-SCRP-TRANSPO-W

Ra-223 4.5E-01 1.5E-01 4.3E-01 8.7E-01 1.7E-03 5.6E-04 1.6E-03 3.2E-03 CN-SCRP-TRANSPO-W

Ra-224 1.8E+00 4.9E-01 1.6E+00 3.8E+00 6.6E-03 1.8E-03 6.0E-03 1.4E-02 CN-SCRP-TRANSPO-W

Ac-225 3.6E-01 1.2E-01 3.4E-01 6.9E-01 1.3E-03 4.4E-04 1.2E-03 2.6E-03 CN-SCRP-TRANSPO-W

Ra-225 1.2E-01 3.3E-02 1.1E-01 2.7E-01 4.5E-04 1.2E-04 3.9E-04 1.0E-03 CN-SCRP-HANDLIN-W

Ra-226 1.3E+01 2.4E-02 1.0E+00 5.0E+01 4.8E-02 9.0E-05 3.7E-03 1.8E-01 CN-SCRP-LANDFIL-N

Ac-227 2.0E+01 4.8E+00 1.6E+01 4.6E+01 7.2E-02 1.8E-02 6.1E-02 1.7E-01 CN-SCRP-HANDLIN-W

Th-227 2.6E-01 7.2E-02 2.3E-01 5.8E-01 9.6E-04 2.7E-04 8.4E-04 2.1E-03 CN-SCRP-HANDLIN-W

Th-228 6.3E+00 1.6E+00 5.2E+00 1.4E+01 2.3E-02 5.8E-03 1.9E-02 5.3E-02 CN-SCRP-ROADBED-W

Ra-228 2.1E+00 4.4E-01 1.6E+00 5.0E+00 7.7E-03 1.6E-03 6.0E-03 1.9E-02 CN-SCRP-ROADBED-W

Th-229 3.3E+01 3.8E-02 2.1E+00 1.2E+02 1.2E-01 1.4E-04 7.7E-03 4.5E-01 CN-SCRP-LANDFIL-N

Th-230 5.3E+00 6.3E-03 3.4E-01 1.9E+01 2.0E-02 2.3E-05 1.3E-03 7.1E-02 CN-SCRP-LANDFIL-N

Pa-231 5.0E+01 7.6E-02 3.7E+00 1.9E+02 1.9E-01 2.8E-04 1.4E-02 7.2E-01 CN-SCRP-LANDFIL-N

Th-231 9.2E-04 5.8E-05 4.7E-04 3.5E-03 3.4E-06 2.2E-07 1.8E-06 1.3E-05 CN-SCRP-TRANSPO-W

Th-232 3.2E+01 4.1E-02 2.3E+00 1.2E+02 1.2E-01 1.5E-04 8.6E-03 4.4E-01 CN-SCRP-LANDFIL-N
Evaluation of Concrete Section 7

Table 7.3 Concrete recycle critical-group dose factors—surficial

(μSv/y per Bq/cm2

) (mrem/y per pCi/cm2)

Criticalgroup

dose

factor

90% Confidence interval Criticalgroup

dose

factor

90% Confidence interval

Radionuclide

5th

(lower

bound)

50th

(median)

95th

(upper

bound)

5th

(lower

bound)

50th

(median)

95th

(upper

bound) Scenario

NUREG-1640 7-16

Pa-233 3.2E-01 1.1E-01 3.1E-01 6.1E-01 1.2E-03 4.1E-04 1.1E-03 2.3E-03 CN-SCRP-TRANSPO-W

U-233 3.8E+00 1.3E-02 3.4E-01 1.3E+01 1.4E-02 5.0E-05 1.3E-03 4.9E-02 CN-SCRP-LANDFIL-N

Th-234 1.8E-02 6.1E-03 1.7E-02 3.4E-02 6.5E-05 2.2E-05 6.3E-05 1.2E-04 CN-SCRP-TRANSPO-W

U-234 3.8E+00 9.7E-03 3.5E-01 1.4E+01 1.4E-02 3.6E-05 1.3E-03 5.2E-02 CN-SCRP-LANDFIL-N

U-235 3.2E+00 1.2E-02 4.0E-01 1.3E+01 1.2E-02 4.3E-05 1.5E-03 4.7E-02 CN-SCRP-LANDFIL-N

Np-237 1.4E+03 1.6E+00 8.3E+01 5.0E+03 5.2E+00 5.9E-03 3.1E-01 1.9E+01 CN-SCRP-LANDFIL-N

Pu-238 4.0E+00 9.2E-01 3.3E+00 1.0E+01 1.5E-02 3.4E-03 1.2E-02 3.7E-02 CN-SCRP-HANDLIN-W

U-238 3.1E+00 8.9E-03 3.4E-01 1.1E+01 1.1E-02 3.3E-05 1.3E-03 3.9E-02 CN-SCRP-LANDFIL-N

Pu-239 5.4E+00 6.9E-03 3.4E-01 2.0E+01 2.0E-02 2.5E-05 1.3E-03 7.5E-02 CN-SCRP-LANDFIL-N

Pu-240 5.4E+00 7.2E-03 3.4E-01 2.0E+01 2.0E-02 2.7E-05 1.3E-03 7.5E-02 CN-SCRP-LANDFIL-N

Pu-241 4.0E-01 3.4E-04 1.8E-02 1.6E+00 1.5E-03 1.3E-06 6.8E-05 5.8E-03 CN-SCRP-LANDFIL-N

Am-241 8.0E+00 1.1E-02 5.1E-01 3.1E+01 3.0E-02 4.1E-05 1.9E-03 1.2E-01 CN-SCRP-LANDFIL-N

Cm-242 2.5E-01 5.9E-02 2.1E-01 6.0E-01 9.2E-04 2.2E-04 7.6E-04 2.2E-03 CN-SCRP-HANDLIN-W

Pu-242 5.1E+00 6.2E-03 3.3E-01 1.9E+01 1.9E-02 2.3E-05 1.2E-03 7.1E-02 CN-SCRP-LANDFIL-N

Cm-244 3.7E+00 8.8E-01 3.1E+00 8.8E+00 1.4E-02 3.3E-03 1.1E-02 3.3E-02 CN-SCRP-HANDLIN-W

The ratio of the 95th to the 5th percentile is a useful measure of the relative width of the 90%

confidence interval for comparison between scenarios. Smaller values of the 95/5 ratio indicate

less uncertainty than larger values. The scenarios with the smallest uncertainty are those with the

fewest number of exposure pathways and the least uncertainty in the parameters describing those

pathways. The scrap transportation scenario accounts for 33 of the 85 radionuclides. It has the

smallest uncertainty of all the critical group scenarios with a 95/5 ratio of about 2 for most

radionuclides. The sources of uncertainty in this scenario are similar to those for the steel scrap

transportation scenario discussed in Section 4.9.

For all scenarios that take place subsequent to the initial transport of scrap, additional sources of

uncertainty are introduced and wider confidence intervals result. Scenarios that address handling

concrete scrap or using it in roadbed construction include uncertainty due to mixing with other

scrap. They also include additional exposure pathways—inhalation of suspended dust and

inadvertent ingestion under dusty conditions. For concrete, this group of handling and

construction scenarios have 95/5 ratios that range from about 5 to about 35.

The landfill resident scenario is limiting for 28 radionuclides. Uncertainty in this scenario

includes contributions from the ground water transport model and pathways for ingestion,

inhalation, and external exposure. Dose factors for nuclides limited by this scenario have 95/5

ratios that range from about 500 to about 6500 and are typically about 2000. This is due to the

uncertainties associated with the groundwater transport model and the timing of the scenario. 
Section 7 Evaluation of Concrete

7-17 NUREG-1640

Over the period of time addressed by this scenario there is a large uncertainty in the rate at which

each radionuclide leaches to the drinking water supply and in the resulting concentration in

drinking water. Some radionuclides undergo significant radioactive decay and some have

radioactive progeny that are increasing over this time scale. Uncertainty in timing is magnified

by the exponential processes of radioactive decay and progeny ingrowth.

The mean values of the derived surficial dose factors for each radionuclide in Table 7.3 represent

the dose to the average member of the critical group exposed to radioactivity initially distributed

over the surface of cleared concrete scrap (Bq/cm2 or pCi/cm2). Derived surficial dose factors

are calculated from mass-based dose factors by use of a surface-to-mass ratio appropriate for

concrete slabs of typical thicknesses. The surface-to-mass ratio is used to derive surficial dose

factors as described in Section 4.7. 

The calculation of derived surficial dose factors is probabilistic. The parameter SM is

represented by a distribution of values that incorporate the variability and uncertainty in the

surface-to-mass ratio of typical concrete slabs available for clearance. This additional source of

uncertainty results in wider confidence intervals for the surficial dose factors than for the massbased dose factors from which they are derived. The relative importance of this additional

uncertainty depends on the scenario. The uncertainty in the surface-to-mass ratio is somewhat

larger for concrete slabs than for typical steel, copper, and aluminum objects due to the wide

range of slab thicknesses and the variability in the density of concrete. For this reason, the

confidence intervals for derived surficial dose factors are relatively wider for concrete relative to

the mass-based dose factors. For scenarios with the narrowest confidence intervals, the added

uncertainty can result in confidence intervals about three times wider than the corresponding

mass-based dose factors. The mass-based dose factor for the scrap transportation scenario has a

95/5 ratio of about 2 for most radionuclides. The corresponding derived surficial dose factors

have a 95/5 ratio of about 6. The added uncertainty in surface-to-mass ratio has a relatively

smaller impact on the confidence interval for scenarios with larger uncertainties, contributing an

additional 50% to 100% for the scrap handling and roadbed construction scenarios. For the

landfill resident scenario the uncertainty in surface-to-mass ratio is small compared to the

uncertainties in the ground water model and ingestion dose pathways. For this scenario, the 95/5

ratio for the derived surficial dose factors ranges from zero to about 30% larger than for the

corresponding mass-based dose factors.
Section 8 Quality Control Program

8-1 NUREG-1640

In order to ensure that the reuse and recycle assessments are defensible, accurate, and verifiable, a

Quality Control Plan (QCP) was prepared and followed during conduct of this evaluation. The QCP

includes specification of procedures and conventions adopted to implement quality control for the

recycle and reuse modeling efforts. The QCP also describes requirements for model development,

equation and parameter definitions, and spreadsheet implementation, and also specifically addresses

requirements for preparation, review, calculation checks, documentation, and record keeping of

technical information. The QCP therefore provides a documented system for ensuring accuracy of

results, as well as a basis for tracing assumptions. The QCP incorporated quality assurance

guidelines provided by both the NRC and other recognized authoritative references. 

The pathway model components developed for this analysis served as the design description for

spreadsheet software development. A Quality Assurance (QA) administrator ensured that appropriate

steps were taken to implement the quality control, documentation and configuration management

requirements of the analyses. The QA administrator acted as a central hub for the review process; all

material passed through the QA administrator for each step of the review and final documentation of

technical information. All technical information developed for the project was peer reviewed. This

included conceptual models, equations and spreadsheets. Specific items to be reviewed were

indicated on the review checklist that accompanied all review packets. In addition to in-house peer

review, aspects of the analyses were peer reviewed by an outside consultant. This review function

was to ensure technical adequacy and reasonableness of the analysis, interpretation of the results,

and other aspects of the analysis. 

In order to meet the documentation requirements in an organized, retrievable manner, a formal

system of document review and filing was implemented. The project QA administrator was

responsible for maintaining the organization and contents of the Project Engineering Cabinet, which

served as a repository for the master versions of all controlled project documents. In addition, a

system was implemented for assigning electronic file names, in order to maintain proper document

control.

48$/,7<&21752/352*5$0

As described in Section 1, the purpose of this evaluation is to provide the technical basis for

implementing criteria for clearance of equipment and material from nuclear facilities licensed by

the Nuclear Regulatory Commission (NRC). A defensible dose assessment for rulemaking

purposes must be accurate and verifiable. It must be supported by a quality assurance record of

checks for errors in documentation, calculation, and transcription. In order to ensure that these

elements are incorporated, a Quality Control Plan (QCP) was prepared and followed while

conducting this evaluation.

The QCP includes specification of procedures and conventions adopted to implement quality

control for the recycle and reuse modeling efforts. The QCP also describes requirements for

model development, equation and parameter definitions, and spreadsheet implementation, as well

as addressing requirements for preparation, review, calculation checks, documentation, and

record keeping of technical information. The QCP, therefore, provides a documented system for

ensuring accuracy of results, as well as a basis for tracing assumptions. The QCP was revised

and updated as the project progressed, in order to address changes in the technical requirements.
Quality Control Program Section 8

NUREG-1640 8-2

The QCP identified the procedures and conventions that were adopted to implement quality

control for the project. In keeping with the nature of the tasks, special emphasis was placed upon

quality assurance for spreadsheet model development and documentation. The QCP

incorporated quality assurance guidelines provided by the following references: 

• NQA-1b-1987, Quality Assurance Program Requirements for Nuclear Facilities

• NQA-2a-1990 Quality Assurance Program Requirements for Nuclear Facilities

• ANSI/ANS-10.4, Guidelines for the Validation and Verification of Scientific and

Engineering Computer Programs for Nuclear Facilities

• NUREG/CR-0167, Software Quality Assurance Program and Guidelines

The QCP also discusses incorporation of the technical approach into the quality control

guidelines. The remainder of this section describes information and criteria contained in the

QCP.

7HFKQLFDO$SSURDFKWR0RGHO,PSOHPHQWDWLRQ

As required by NRC, computer applications and models met the requirements of the NRC Policy

and Procedures Manual, Section 2.2. Spreadsheet models were developed on PC-based

platforms running proprietary, commercial software. Other commercially available software was

used to precalculate "lumped" parameter values for use in the spreadsheet models. Prior to use,

software was approved by the SAIC Task Manager and Project Manager. With only one

exception, all of the codes listed below were run on personal computers (the MCNP code was

run on a workstation). This listing does not include non-technical codes such as word processing

or project management software. The following software applications were approved and used in

this analysis.

Crystal Ball 4.0 (Decisioneering 1996). Crystal Ball, a forecasting and risk analysis program, is

used as an add-on to Excel. It uses the Monte Carlo sampling methods to calculate uncertainty in

a model result. Crystal Ball will sample from an assumption cell in the Excel worksheet that

contains a probability distribution defined by the user and calculate a range of possible outcomes

in the forecast cell as well as the likelihood of achieving each of them. The Monte Carlo method,

as used by Crystal Ball, is accomplished with three simple steps which are repeated for a set

number of times defined by the user. These steps are (1) generating random numbers for

assumption cells, (2) calculating the entire spreadsheet, and (3) displaying results in a forecast

chart. This program was used as an uncertainty analysis tool.

Excel 97 (SR-1) (Microsoft 1997). Excel is a general purpose, spreadsheet analysis application. 

Excel provides the tools necessary to perform data analysis, list-keeping, and calculations. Excel

also enables the user to present the results efficiently. Worksheets enable the user to store,

manipulate, calculate, and analyze data. Macros are also available in Excel, which enable the

user to automate frequently performed tasks and perform specialized calculations. Excel was

used as the platform for all calculations. 
Section 8 Quality Control Program

8-3 NUREG-1640

MCNP (Briesmeister 1993). MCNP (Monte Carlo N-Particle) is a three-dimensional transport

code which treats an arbitrary configuration of materials in cells bounded by surfaces. Pointwise,

continuous-energy cross-section data are used. The transport equation is solved by the method of

random walk (Monte Carlo). Energy specific sources and response functions may be used to

estimate dosimetric quantities of interest for virtually any configuration. MCNP was used to

calculate all of the external exposure geometry factors except those obtained from Environmental

Protection Agency (EPA) documents.

MicroShield 4 (Negin and Worku 1992a). MicroShield analyzes shielding and estimates

exposure from gamma radiation. This version allows versatile geometries with offsets from axes

of symmetry. Sensitivity analyses are available for dimensional variations within a single case. 

Results are calculated with and without buildup simultaneously. MicroShield has the capability

to handle photon energies between .015 and 15 MeV. Data for attenuation coefficients, buildup

factors, and buildup factor coefficients are obtained from information distributed by the

Radiation Shielding Information Center and included in ANS 6.4.3. MicroShield was used in the

development of uncertainty ranges for the geometry factors and occasionally as a quality

assurance check for the geometry factors calculated with MCNP.

RadDecay 4 (Negin and Worku 1992b). RadDecay contains radioactive decay information for

497 radionuclides. Data includes the half-lives, radioactive daughters, probabilities per decay,

and decay product energies for alphas, betas, positrons, electrons, X-rays, and gamma rays. 

Given an initial radioactivity and decay time, RadDecay will calculate the remaining radioactivity

of a radionuclide and the radioactivity level of its progeny. The decay chain is calculated and

displayed for up to 20 generations. Identical daughters generated along different branches of the

parent decay chain are combined. RadDecay also has the capability to search for gammas and Xrays in a specific energy range set by the user (Negin and Worku 1992b). RadDecay was used

primarily to calculate ingrowth of radioactive progeny.

RADTRAN 4 (Neuhauser and Kanipe 1994). The RADTRAN 4 code combines user-supplied

input data with health physics data to calculate the expected radiological consequences and risks

resulting from the transportation of radioactive material. Estimates of radiological consequences

and risks are derived by numerically modeling the path and behavior of each package from the

time that transportation begins until it arrives at its destination.

4XDOLW\5HTXLUHPHQWV

The exposure pathway model components developed for this analysis, including scenario

descriptions, parameter tables, mathematical equations and pathway flow diagrams, served as the

design description for spreadsheet software development. All staff involved in model

development were apprised of these quality control, documentation, and configuration

management requirements, and a Quality Assurance (QA) administrator ensured that appropriate

steps were taken to implement the requirements. Each model developer was responsible for

assuring that the data and formulas encoded as spreadsheet models were accurate, complete,
Quality Control Program Section 8

NUREG-1640 8-4

verifiable, and properly documented. The basic quality requirements imposed on this analysis

are listed below. 

 - The source and evolution of all model parameter values and algorithms must be

documented. Documentation must be sufficient to permit the completion of independent

verification and quality reviews and to allow ready verification of configuration

management functions by audit. 

 - Documents and references necessary to establish the basis of a model must be maintained

in the Project Engineering Cabinet. 

 - Design changes must be documented and traceable. 

 - Where appropriate, parameters and units must be named in a manner consistent with

Section 2.2 of NUREG/CR-5512 (Kennedy and Strenge 1992) or Volume 3 of

NUREG/CR-5512 (Beyeler et al. 1996). 

 - Spreadsheet applications must contain sufficient internal documentation so that users do

not have to consult external manuals for routine operation of the spreadsheet. If external

manuals or other documents are necessary, the spreadsheet must contain complete

citations for these documents. Documentation must be sufficient to permit a user to

identify and track any changes to the spreadsheet made under the configuration control

procedures.

 - Spreadsheets must conform to a standard structure, consisting of a title page followed by

several principal sections. The banner/title page must identify the model, the version

number, and the responsible author. The spreadsheet must also contain a workbook or

spreadsheet description, macro fields and macro listings. Another section of the

spreadsheet must list the parameter names, symbols, units, default values, as well as

references that are applied in the spreadsheet. Another section must contain the data

input fields for radionuclide-independent and dependent parameters. The calculational

fields of the model must be delineated in another section. Other sections of the

spreadsheet must be identified as needed. 

 - Numeric formats must be consistent. Appropriate significant figures should be used for

final results. 

 - To the extent practicable, standard functions within the spreadsheet applications software

should be used in lieu of custom functions. To the extent practicable, if custom functions

are used, they will be consistently applied to all calculations performed. 
Section 8 Quality Control Program

8-5 NUREG-1640

'RFXPHQW5HYLHZ&RQWURODQG&RQILJXUDWLRQ0DQDJHPHQW

In order to meet the documentation requirements in an organized, retrievable manner, a formal

system of document review and filing was implemented. A QA administrator acted as a central

hub for the review process; all material passed through the QA administrator for each step of the

review and final documentation of technical information. 

When a scenario model, material flow description, or other technical description was sufficiently

developed, the author was responsible for transmitting a packet containing descriptions,

references and electronic copies to the project QA administrator for document control. The QA

Administrator would then review the submittal for completeness, log-in and file the model, and

submit the packet for peer review. 

Because of the complexity of many of the spreadsheet models in this analysis, documentation and

review of the scenario descriptions were completed prior to encoding the spreadsheet. 

4$5HYLHZRI7HFKQLFDO,QIRUPDWLRQ

All technical information developed for the project was peer-reviewed. This included conceptual

models, equations and spreadsheets. Specific items to be reviewed were indicated on the review

checklist that accompanied all review packets.

The QA review for a new or revised version of a spreadsheet model included, at a minimum, a

review of the following six elements: parameters, benchmark check, calculation model,

documentation, transcription, and verification. Parameter values were checked against sources

for accuracy and transcription; documentation was checked for completeness. Verification

involved a check of whether or not the mathematical model algorithms were accurately

implemented. Benchmark checks included a comparison of the computation results of a specific

spreadsheet or workbook with the results (printed version) of a reference spreadsheet or

workbook used to analyze the same or comparable problem. QA reviews of interim revisions

were limited in scope, but were sufficient to address the documented changes.

In addition to in-house peer-review by SAIC technical personnel, the analyses were peerreviewed by an outside contractor. This review function was to ensure that the analyses were

reasonable and technically adequate and the results were interpreted satisfactorily.

5HFRUGNHHSLQJ3URMHFW(QJLQHHULQJ&DELQHW

The project QA administrator was responsible for maintaining the organization and contents of

the Project Engineering Cabinet, which served as a repository for the master versions of all

controlled project documents. Individual files were separately labeled and coded by the QA

Administrator, and the cabinet was organized to include the sections outlined below. 
Quality Control Program Section 8

NUREG-1640 8-6

Master Directory

The master directory contained information applicable to all aspects of the project. This includes

master scenario lists, document status tables, procedures, and general project information. The

master directory served as a key section of the project engineering cabinet and is the starting

point for anyone looking for specific technical information about the project. 

Scenario Files

The scenario is a primary, organizational unit for this analysis. As such, project documentation

and quality review functions were structured around scenario development. Documentation of

the description, modeling, and review for each scenario was maintained as a unit: a discrete file

in the project engineering cabinet. A completed scenario file contains all descriptions,

documents, and forms indicated for that individual scenario. It includes a full-version history of

the model and provides for traceability of configuration control, model validation, and other

elements of the QA review.

Scenario model development usually proceeded in three stages, where the conceptual framework

and mathematical representation of the scenario model was completed and reviewed prior to

encoding the deterministic model into a spreadsheet. In turn, encoding and review of the

deterministic model served as the basis for probabilistic modeling. This process was reflected in

the Engineering Cabinet documentation. 

The file structure described above for printed documents in the cabinet is duplicated for

electronic versions of the scenario files. A controlled electronic media repository was

maintained by the QA Administrator. Each electronic file was assigned a unique, 8-character

name according to the conventions described in Section 8.6. Three-digit file extensions

(e.g.,*.xxx) were used to indicate individual document types and revision numbers maintained in

the scenario file. For example, the scenario file for the transportation of dust was labeled as

tdu03fei. The original (revision 0) scenario spreadsheet was labeled as tdu03fei.ds0. 

Material Flow Files

The Material Flow section contains all the information used to develop the conceptual and

mathematical models, as well as the initial version and supporting documentation, for the

material flow. For purposes of project documentation and quality review, material flow models

and spreadsheets were considered to be the same as scenario models, and met the same set of

requirements. Information in this section also contains the original review checklist form

attached to the appropriate material. 

Background Documentation Files

Background documentation refers to technical information about the project that does not clearly

fall into one of the other specified sections of the Engineering Cabinet. An Engineering Design
Section 8 Quality Control Program

8-7 NUREG-1640

File (EDF) system provided a formal structure for document review and control for additional

technical descriptions and reference documents that needed to be included in the project files. 

For instance, the EDF format was used to document the technical development and justification

of parameters such as the surface-to-mass ratios. 

All background documents to be reviewed or filed required an EDF coversheet followed by the

body of the report, references, and any appendices. A completed EDF coversheet included the

EDF log number (assigned by QA Administrator), the report title, a report summary, and

signatures of all authors and reviewers.

Geometry Factor Files

The Geometry Factors section of the Engineering File Cabinet contains details of the calculations

needed to develop Geometry Factors for the scenarios evaluated. The Geometry Factor is a

"lumped parameter," therefore, the content of this file section is different than other sections of

the cabinet, but still contains a complete documentation record. 

Quality Assurance Administration Files

The Project QA Documentation section contains the quality assurance documents for the overall

project (i.e., the Project Quality Control Plan with all the attached appendices). The QA Forms

section also contains all completed QA forms (i.e., spreadsheet QA form). The QA forms were

printed on colored paper so they were easy to identify. 

Project Management Files

The Project Management section was for items such as monthly reports, memoranda, and other

items applicable to various aspects of management of the project. 

Report Files

The Report section contains all draft and final versions of formal reports produced for the NRC

as part of this analysis. 

References

All references that are used are kept in the Reference section.

,QVWUXFWLRQVIRU1DPLQJ)LOHVDQG6FHQDULRV

The following criteria were used when assigning electronic file names to scenario files for this

evaluation. In general, the first eight file characters are reserved for each of the following six

classifications: scenario category, material type, restricted or unrestricted uses, scenario
Quality Control Program Section 8

NUREG-1640 8-8

description number, initial product material type, and target population. The final criterion

specifies the file extension criteria.

1) The first character was reserved for the scenario category. The following scenario

categories have been identified:

h = handling and processing d = disposal

s = storage t = transportation 

p = product use x = applies to all categories

2) The second character was reserved for the product material type. The following material

types have been identified:

a = atmospheric emission d = dust and dust byproducts

m = scrap metal r = refined metal product

s = slag from steel refining x = applies to all end product

material types

3 The third character was reserved for designating whether the scenarios is a restricted use

or an unrestricted use scenario, as follows:

r = restricted use u = unrestricted use

x = all uses

Note: “Restricted” and “unrestricted” terms were used in the early phases of this analysis, but

were dropped during the course of the analysis. There are no “restricted use” scenarios

evaluated, so this character is unnecessary.

4) The fourth and fifth characters were reserved for a scenario description number (1–99). 

This number can be cross-referenced to the Scenario Description Table to provide a

complete scenario description. 

5) The sixth and seventh characters were reserved for the initial product material being

reused or recycled. Standard chemical symbols were used when possible:

al = aluminum fe = iron/steel

 cu = copper cn = concrete

 xx = applies to all initial product materials

6) The eighth character was used to identify the target population, using the following

abbreviations:

i = onsite worker, individual o = onsite worker, population

g = general public, individual p = general public, population

v = visitor, individual x = applies to all target

populations
Section 8 Quality Control Program

8-9 NUREG-1640

7) File extensions reflected the document type and revision number (used only for exposure

scenarios). The first and second characters indicate the document type and the third

character indicates the revision number: 

*.pd# = probabilistic description, revision number #

*.dd# = deterministic description, revision number #

*.ps# = probabilistic spreadsheet, revision number #

*.ds# = deterministic spreadsheet, revision number #

Following the above file naming criteria, file tdu03fei.dd1 is the first revision of a deterministic

scenario description and technical justification for the unrestricted transportation of dust. This

scenario is the third in the transportation category, thus it has a scenario description number of

03. The initial source material being recycled is steel. The dose is evaluated for an individual

onsite worker.

For the purposes of this report, additional scenario abbreviations were developed. The use of

these abbreviations does not affect the electronic file names. A cross-reference between the two

sets of file names is included in Appendix A.
Section 9 References

9-1 NUREG-1640

5()(5(1&(6

AEC, 1974. Termination of Operating Licenses for Nuclear Reactors, Regulatory Guide 1.86,

U.S. Atomic Energy Commission.

AIHC, 1994. American Industrial Health Council, "Exposure Factors Source Book,"

Washington, DC, May 1994.

AIHC, 1995. Exposure Factors Source Book, The American Industrial Health Council.

AISI 1998. American Iron and Steel Institute, data cited in promotional material for Florida Steel

Homes, Inc., located on the Internet at http://www.floridasteelhome.com/ststistics.htm,

May 28, 1998.

Anspaugh, L. R., et al., 1974. "Evaluation of the Resuspension Pathway Toward Protective

Guidelines for Soil Contamination with Radioactivity," presented at the International

Atomic Energy Agency/World Health Organization Symposium on Radiological Safety

Evaluation of Population Doses and Application of Radiological Safety Standards to Man

and the Environment, Portoaz, Yugoslavia, May 20 - 24, 1974. 

Association of Iron and Steel Engineers (AISE), 1993. Directory: Iron and Steel Plants 1993

Barnes, D. E., 1959. “Basic Criteria in the Control of Air and Surface Contamination,” in

Symposium on Health Physics in Nuclear Installations, at Risø, Denmark, 25–28 May

1959.

Bever, M. B., 1986. Encyclopedia of Materials Science and Engineering, Volume 2. 

Beyeler et al. 1996. Residual Radioactive Contamination from Decommissioning: Parameter

Analysis, NUREG/CR-5512, Volume 3 (Draft for Review), Sandia National Laboratories,

April 25, 1996. 

BLS 1998: Information from the Occupational Outlook Handbook, downloaded from the BLS

website on 4/3/98 (http://stats.bls.gov/oco). 

Briesmeister, J. F., 1993. “MCNP-A General Monte Carlo N-Particle Transport Code, Version

4A,” LA-12625-M, Los Alamos National Laboratory, Los Alamos, NM, November 1993.

Brodsky, A., 1980. “Resuspension Factors and Probabilities of Intake of Material in Process (Or

“Is 10-6 a Magic Number in Health Physics?”),” Health Physics, Vol. 39, December 1980,

pp. 992-1000.

Brough, J. R. and W. A. Carter, 1972. Air Pollution Control of an Electric Furnace Steelmaking

Shop, Journal of the Air Pollution Control Association, Volume 22, No. 3, March 1972.
References Section 9

NUREG-1640 9-2

Brown, R. E., 1993. "Minerals Yearbook, 1992: Iron and Steel Scrap," U.S. Bureau of Mines,

October, 1993.

Brunskill, R. T., 1964. “The Relationship Between Surface and Airborne Contamination,” in

Surface Contamination, Proceedings of a Symposium held at Gatlinburg, Tennessee, June

1964.

Butts, A., 1970. COPPER: The Science and Technology of the Metal, Its Alloys and

Compounds. Hafner Publishing Company, Inc., 1970.

Cass, R. W. and J. E. Langley, 1977. Fractional Efficiency of an Electric Arc Furnace

Baghouse, EPA-600/7-77-023, March 1977.

Charles, D. and G. M. Smith, 1992. "Waste Management Study for Large Volumes of Very Low

Level Waste from Decommissioning of Nuclear Installations," report prepared by Intera

Information Technologies for CEC, IE2713-5, Version 2; Oxfordshire, U.K; December

1992.

Chen, S. Y., 1993. Risk Assessment Based on Current Release Standards for Radioactive

Surface Contamination, ANL/EAIS/CP-79677, Argonne National Laboratory, September

1993.

Chen, W. F., 1995. Civil Engineering Handbook, W. F. Chen, ed., CRC Press, 1995.

Copeland, G. L., R. L. Heestand, and R.S. Mateer, 1978. Volume Reduction of Low-Level

Contaminated Metal Waste by Melting- Selection of Method and Conceptual Plan. 

ORNL/TM-6388, Oak Ridge National Laboratory, June 1978.

Cowherd, C., R. Bohn, T. Cuscino, 1979. Iron and Steel Plant Open Source Fugitive Emission

Evaluation, Midwest Research Institute, Kansas City, MO, EPA-600/2-79-103, May

1979.

CRC, 1992. Handbook of Chemistry and Physics, 73rd edition (1992-1993), D. Lide, Editor-inChief, pg 15-38.

Cuscino, T. A., 1979. Particulate Emission Factors Applicable to the Iron and Steel Industry,

EPA-450/4-79-028, September.

Decisioneering, 1996. Crystal Ball Version 4.0 User Manual, Decisioneering, Inc., 1996.

Deckert, A., R. Graf, and R. Gortz, 1992. "Radiation Exposure to the General Public from

Reclaimed Metals Out of Nuclear Facilities," Proceedings of the Symposium on Waste

Management, Vol.2, pp1809-1814, Tucson, AZ, March 1-5, 1992.
Section 9 References

9-3 NUREG-1640

Dehmel, J. C., D. Loomis, J. Mauro, and M. Kaplan, 1994. Characterization of Class A LowLevel Radioactive Waste 1989 - 1990. NUREG/CR-6147, U.S. Nuclear Regulatory

Commission, Washington, D.C.

Doty, S. R. and B. L. Wallace, 1976. A Climatological Analysis of Pasquill Stability Categories

Based on ’Star’ Summaries, National Oceanic and Atmospheric Administration, April

1976.

Dunster, H. J., 1964. “The Concept of Derived Working Limits for Surface Contamination,” in

Surface Contamination, Proceedings of a Symposium held at Gatlinburg, Tennessee, June

1964.

Dyer, N. C. 1995. "Radionuclides in United States commercial Nuclear Power Reactors," 

Radiation Protection Management, Vol. 12, No. 1, January/February 1995).

Elert, M. and M. Wiborgh, 1992. Basis for criteria for exemption of decommissioning waste: 

Reprocessing of dust from recycling of steel, KEMAKTA Konsult AB, KEMAKTA AR

92-08, June 1992

EPA 1997a. Technical Support Document: Evaluation of the Potential for Recycling of Scrap

Metals From Nuclear Facilities, (Review Draft), U.S. Environmental Protection Agency,

March 11, 1997.

EPA, 1997b. Guiding Principles for Monte Carlo Analysis, Office of Prevention, Pesticides, and

Toxic Substances, EPA/630/R-97/001, March 1997

EPA, 1995. Profile of the Nonferrous Metals Industry, EPA 310-R-95-010, September 1995.

EPA, 1993a. External Exposure to Radionuclides in Air, Water, and Soil. Federal Guidance

Report No. 12, EPA 402-R-93-081, EPA Office of Radiation and Indoor Air,

Washington, D.C.

EPA, 1993b. Solid Waste Disposal Facility Criteria Technical Manual. EPA 530-R-93-017,

EPA Office of Solid Waste and Emergency Response, Washington, D.C.

EPA, 1991. Clean Air Act Assessment Package (CAP88-PC), Environmental Protection Agency,

Washington, D.C., 1991.

EPA, 1989a. Exposure Factors Handbook, EPA/600/8-89/-43, EPA Office of Health and

Environmental.

EPA, 1989b. Technical Guidance Document: Final Covers on Hazardous Waste Landfills and

Surface Impoundments. EPA 530-SW-89-047, Office of Solid Waste and Emergency

Response, Washington, D.C.
References Section 9

NUREG-1640 9-4

EPA, 1988. Limiting Values of Radionuclide Intake and Air Concentration and Dose

Conversion Factors for Inhalation, Submersion, and Ingestion. Federal Guidance Report

No. 11, EPA-520/1-88-020, EPA Office of Radiation Programs, Washington, D.C.

EPA, 1986. Iron and Steel Industry Particulate Emissions Source Category Report, EPA/600/7-

86/036, Office of Research and Development, October 1986.

EPA, 1977. Proposed Guidance on Dose Limits for Persons Exposed to Transuranium Elements

in the General Environment, Office of Radiation Programs, Criteria and Standards

Division, Washington, D.C.

EPRI, 1993. Electric Arc Furnace Dust - 1993 Overview. CMP Report No. 93-1, EPRI Center

of Materials Production, July 1993.

Fenton, 1996. “Minerals Yearbook, 1995: Iron and Steel Scrap,” U.S. Bureau of Mines and the

U.S. Geological Survey.

Fuchs, R. L. and S. D. McDonald, 1993. 1992 State-by State Assessment of Low-Level

Radioactive Wastes Received at Commercial Disposal Sites, Department of Energy,

DOE/LLW-181, September 1993.

Gibson, J. A. B., and A. D. Wrixon, 1979. “Methods for the Calculations of Derived Working

Limits for Surface Contamination by Low-Toxicity Radionuclides,” Health Physics, 36,

March 1979, pp. 311-321.

Harvey, D. S., 1990. Melting of Contaminated Steel Scrap from Decommissioning,

Decommissioning of Nuclear Installations, Elsevier Applied Sciece, London and New

York.

Healy, J. W., 1980. "Review of Resuspension Models," in Transuranic Elements in the

Environment, W. C. Hanson (Editor).

Healy, J. W., 1971. Surface Contamination: Decision Levels, LA-4558-MS, Los Alamos

Scientific Laboratory, September, 1971.

Horst, T. W., 1982. “The Estimation of Airborne and Surface Contamination Resulting from the

Deposition-Resuspension Process,” Health Physics, Vol. 43, No. 2, August 1982, pp.

269-272.

IAEA, 1996. Clearance Levels for Radionculides in Solid Materials, Application of exemption

principles, IAEA-TECDOC-855, International Atomic Energy Agency, Vienna,

January 1996.
Section 9 References

9-5 NUREG-1640

IAEA, 1992. Application of Exemption of Principles to the Recycle and Reuse of Materials from

Nuclear Facilities, Safety Series No. 111-P-1.1, International Atomic Energy Agency,

Vienna, 1992.

IAEA, 1989. Evaluating the Reliability of Predictions Made Using Environmental Transfer

Models. Safety Series No. 100, International Atomic Energy Agency, Vienna, 1989.

IAEA, 1970. Monitoring of Radioactive Contamination on Surfaces, Technical Report Series

No. 120, International Atomic Energy Agency, Vienna, 1970.

ICRP 1994. Human Respiratory Tract Model for Radiological Protection, Publication No. 66,

International Commission on Radiological Protection, 1994.

ICRP, 1978. Limits for Intakes of Radionuclides by Workers, ICRP Publication 30, International

Commission on Radiological Protection, July 1978.

ICRP 1974. Report of the Task Group on Reference Man, Publication No. 23, International

Commission on Radiological Protection, 1974.

Jeffery, J. and J. Vay, 1986. Iron and Steel Industry Particulate Emissions: Source Category

Report, EPA/600/7-86/036, October 1986.

Jones, I. S. and S. F. Pond, 1964. “Some Experiments to Determine the Resuspension Factor of

Plutonium from Various Surfaces,” in Surface Contamination, Proceedings of a

Symposium held at Gatlinburg, Tennessee, June 1964.

Kalyoncu, R. S., 1996. “Minerals Yearbook, 1995: Slag—Iron and Steel,” U.S. Bureau of

Mines and the U.S. Geological Survey.

Kennedy, W. E., Jr., et al., 1981. A Review of Removable Surface Contamination on Radioactive

Materials Transportation Containers, NUREG/CR-1858, PNL-3666, Pacific Northwest

Laboratory, May, 1981.

Kennedy, W. E., Jr., and D. L. Strenge. 1992. Residual Radioactive Contamination From

Decommissioning: Volume 1, Technical Basis for Translating Contamination Levels to

Annual Total Effective Dose Equivalent. NUREG/CR-5512, U.S. Nuclear Regulatory

Commission, Washington, D.C.

Lankford, W. T., et al (eds.) 1985. The Making, Shaping and Treating of Steel, United States

Steel and Association of Iron and Steel Engineers, 10th Edition.

Layton, D. W., 1993. “Metabolically Consistent Breathing Rates for Use in Dose Assessments,”

Health Physics, Volume 64, No. 1, January 1993.
References Section 9

NUREG-1640 9-6

Logan, S. E., 1993. "Risk Assessment of Options for Disposition of EAF Dust Following A

Meltdown Incident of Radioactive Cesium Source in Scrap Steel.," S. E. Logan and

Associates, Inc., Santa Fe, NM, SELA-9301, April 1993.

Maheras, S.J., A. S. Rood, S. O. Magnuson, M. E. Sussman, and R. N. Bhatt, 1994. Radioactive

Waste Management Complex Low-Level Waste Radiological Performance Assessment. 

EGG-WM-8773.

Meck, R. A., 1992. Letter to Dr. Gordon Linsley, Scientific Secretary, Division of Nuclear Fuel

Cycle and Waste Management, International Atomic Energy Agency, November 9, 1992.

Microsoft, 1997. Microsoft Excel 97, SR-1, Microsoft Corporation, 1997.

Miller, C. W. 1984. Models and Parameters for Environmental Radiological Assessments,

DOE/TIC-11468, C. W. Miller (editor), U. S.. Department of Energy, 1984.

Mody, V., and R. Jakhete, 1988. "Dust Control Handbook," Martin Marietta Laboratories, Noyes

Data Corporation, pp. 69-79, 1988.

NCRP, 1996. NCRP Commentary 14, Guide for Uncertainty Analysis in Dose and Risk

Assessments Related to Environmental Contamination, May, 1996.

NCRP, 1984. Radiological Assessment: Predicting the Transport, Bioaccumulation, and Uptake

by Man of Radionuclides Released to the Environment, NCRP Report No. 76,

March 1984.

Negin, C.A., and G. Worku, 1992a. MicroShield, Version 4, User’s Manual, Grove 92-2, Grove

Engineering, Inc., May 1992.

Negin, C.A., and G. Worku, 1992b. RadDecay Radioactive Nuclide Library and Decay

Software Version 4, User’s Manual, Grove 91-1, Grove Engineering, Inc., April 1992.

Neuhauser, K. S., and P. L. Kanipe, 1989. RADTRAN 4 User Guide: Technical Manual. 

SAND 89-2370, Sandia National Laboratories.

NIOSH (National Institute of Safety and Health), 1990. Pocket Guide to Chemical Hazards,

National Institute for Occupational Safety and Health, Cincinnati, Ohio.

NRC, 1994a. Staff Action Plan for an Enhanced Participatory Rulemaking for Recycle/Reuse

Criteria, SECY 94-221, U.S. Nuclear Regulatory Commission, August 19, 1994.

NRC, 1994b. Working Draft Regulatory Guide on Release Criteria for Decommissioning: NRC

Staff’s Draft for Comment, NUREG-1500, U.S. Nuclear Regulatory Commission, August

1994. 
Section 9 References

9-7 NUREG-1640

NRC, 1977. Regulatory Guide 1.109: Calculation of Annual Doses to Man from Routine

Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10CFR

Part 50, Appendix I, 1977. U.S. Nuclear Regulatory Guide 1.109, October 1977.

O’Donnell, F.R., S.J. Cotter, D.C. Kocher, E. L. Etnier, and A.P. Watson, 1978. Potential

Radiation Dose to Man from Recycle of Metals Reclaimed from a Decommissioned

Nuclear Power Plant, NUREG/CR-0134, ORNL/NUREG/TM-215, Oak Ridge National

Laboratory, December 1978.

Oak, H. D., G.M. Holter, W. E. Kennedy, Jr., and G. J. Konzek, 1980. Technology, Safety, and

Costs of Decommissioning a Reference Boiling Water Power Station. NUREG/CR0672, U.S. Nuclear Regulatory Commission, Washington, DC.

Rathje, W. L., 1991. “Once and Future Landfills,” National Geographic, May 1991.

Roseberry, A. M. and D. E. Burmaster, 1992. “Lognormal Distributions for Water Intake by

Children and Adults,” Risk Analysis, Vol. 12, No. 1, 1992. 

Royster, G. W. Jr., and B. R. Fish, 1964. “Techniques for Assessing ‘Removable’ Surface

Contamination,” in Surface Contamination, Proceedings of a Symposium held at

Gatlinburg, Tennessee, June 1964.

Sandy Cohen & Associates (SC&A), 1995. Analysis of the Potential Recycling of Department of

Energy Radioactive Scrap Metal, Sandy Cohen & Associates, Inc., August 14, 1995.

Schneider, K. J. and C.E. Jenkins, 1977. Technology, Safety, and Costs of Decommissioning a

Reference Nuclear Fuel Reprocessing Plant. NUREG/CR-0278, U.S. Nuclear Regulatory

Commission, Washington, DC.

Schneider Simon, S. L. 1998. “Soil Ingestion by Humans: A Review of History, Data, and

Etiology with Application to Risk Assessment of Radioactively Contaminated Soil,”

Health Physics, Vol. 74, No. 6, June 1998, pp. 647 - 672.

Slade, D.H., 1968. Meteorology and Atomic Energy.

Smith R.I., G. J. Knozek, and W. E. Kennedy, Jr., 1978. Technology, Safety, and Costs of

Decommissioning a Reference Pressurized Water Power Station. NUREG/CR-0130, U.S.

Nuclear Regulatory Commission, Washington, DC.

Smith, G. R., 1996. Recycling -- Nonferrous Metal, U.S. Bureau of Mines, Volume 1 - 1994.

Solomon, C., 1993. "Mineral Yearbook, 1992: Slag-Iron and Steel," U.S. Bureau of Mines,

September 1993.
References Section 9

NUREG-1640 9-8

Spangler, G. W. and C.A. Willis, 1964. “Permissible Contamination Limits,” in Surface

Contamination, Proceedings of a Symposium held at Gatlinburg, Tennessee, June 1964.

Stewart, K., 1964. “The Resuspension of Particulate Material from Surfaces,” in Surface

Contamination, Proceedings of a Symposium held at Gatlinburg, Tennessee, June 1964.

Szabo, M.F. and R.W. Gerstle, 1978. Operation and Maintenance of Particulate Control

Devices on Selected Steel and Ferroalloy Processes, EPA-600/2-78-037, PEDCo.

Environmental, Inc., prepared for the USEPA, Industrial Environmental Research Lab,

Research Triangle Park, N.C.

Till, J. E. and H. R. Meyer, 1983. Radiological Assessment; A Textbook on Environmental Dose

Analysis. NUREG/CR-3332, U.S. Nuclear Regulatory Commission, Washington, D.C.

U.S. Public Health Service, 1992. Toxicological Profile for Aluminum. Agency for Toxic

Substances and Disease Registry, U.S. Public Health Service. July 1992.

U.S. Public Health Service, 1990. Toxicological Profile for Copper. Agency for Toxic

Substances and Disease Registry, U.S. Public Health Service. December 1990.

USBM, 1997. “Recycling -- Nonferrous Metals,” Minerals Yearbook, U.S. Bureau of Mines.

USBM, 1985. Mineral Facts and Problems. Bulletin 675.

Venturini, J. L., 1970. Operating Experience with a Large Baghouse in an Electric Arc Furnace

Steelmaking Shop, Journal of the Air Pollution Control Association, Volume 20, No 12,

December 1970.

Yu, C., C. Loureiro, J. J. Cheng, L. G. Jones, Y. Y. Wang, Y. P. Chia, and E. Faillace, 1993. 

"Data Collection Handbook to Support Modeling the Impacts of Radioactive Material in

Soil," ANL/EAIS-8, April.
Glossary

glossary-1 NUREG-1640

GLOSSARY OF TERMS

(* = terms that are defined specifically for this analysis; others use standard definitions)

average member of the critical group: A hypothetical individual that represents the average

(mean) member of the critical group in terms of potential dose. 

bias: The tendency for an estimate to deviate from an actual or real event. Bias may be the

tendency for a model to over- or underpredict. (Till and Meyer 1983)

bremsstrahlung: Photons emitted from an atom as a result of an electron losing energy as it

passes near the highly charged nucleus of a heavy element.

byproduct: See co-products

*clearance: The release of sources of radioactive material from regulatory control. Clearance of

items could result in reuse, recycle, or direct disposal of equipment or material.

*clearance level: The level of activity or activity concentration at which clearance occurs.

*cleared material: Equipment or material that has been cleared from regulatory control.

confidence interval: The lower and upper end points of an interval from a distribution. For

example, the interval from the 5th-percentile value to the 95th-percentile value is a “90%

confidence interval” because it contains 90% of the estimated values in the distribution

(95% minus 5%).

conservative bias: Intentional bias toward overestimation. (Till and Meyer 1983)

co-products: In the context of refinery co-products, this term refers to the major products

resulting from the refining of scrap metal. These co-products (also referred to as

byproducts) are refined metal, slag, baghouse dust, and off-gas.

critical group: The group of individuals reasonably expected to receive the greatest exposure to

residual radioactivity for any applicable set of circumstances (10CFR20.1003). In this

analysis for clearance of equipment and material, there is a critical group for each

radionuclide evaluated. In this analysis, the critical group for each radionuclide is the

group of individuals described in the exposure scenario that results in the highest mean

dose factor for that radionuclide. 

*critical-group dose factor: The point-estimate dose factor for the average member of the

critical group. This is the mean (average) dose factor from the distribution of dose factors

calculated for the critical group for each radionuclide. For each material analyzed, there is

a critical-group dose factor for each radionuclide.
Glossary

NUREG-1640 glossary-2

deep dose equivalent: (Hd), which applies to external whole-body exposure, is the dose

equivalent at a tissue depth of 1 cm (1000 mg/cm2). (10CFR20)

descriptive statistics: Simple statistical measures that characterize a distribution of values. These

are also refered to as moments of a distribution. Common descriptive statistics include the

mean, the variance, and the standard deviation. 

deterministic: A model whose output is predetermined by the mathematical form of its equations

and the selection of a single value for each input parameter. (NCRP 1984)

dose equivalent (HT): the product of the absorbed dose in tissue, quality factor, and all other

necessary modifying factors at the location of interest. The units of dose equivalent are

the rem and sievert (Sv). (10CFR20)

dose factor: A radionuclide-specific, hypothetical, dose calculated for the average member of a

critical group, normalized to a unit radionuclide concentration in cleared material (i.e.,

μSv/a per Bq/g). The point estimate for the dose factor is the mean of the distribution of

possible dose factors.

effective dose equivalent (HE): the sum of the products of the dose equivalent to the organ or

tissue (Hr) and the weighting factors (Wr) applicable to each of the body organs or tissues

that are irradiated (HE = WTHr). (10CFR20)

element-dependent parameter: Typically refers to a parameter whose value is specific to a given

element, and therefore may be different for every element.

exposure scenario: The set of circumstances that define a potential situation that could result in

an exposure to an individual or group of individuals. Exposure scenarios are used to

model potential doses resulting from reuse, recycle and disposal of material.

*geometry factor: The dose rate from an external source of radiation from a specific source and

source-receptor relationship.

Latin Hypercube sampling: A sampling method for probabilistic uncertainty analysis that divides

a probability distribution into intervals of equal probability. Compared with conventional

Monte Carlo random sampling, Latin Hypercube sampling is more precise because the

entire range of the distribution is sampled in a more even, consistent manner. Latin

Hypercube sampling was used in this analysis.

licensed material: source material, special nuclear material, or byproduct material received,

possessed, used, transferred or disposed of under a general or specific license issued by

the Commission. (10CFR20)
Glossary

glossary-3 NUREG-1640

mass loading: A factor that relates concentration of a constituent in soil to the concentration of

that constituent in air. 

*material flow model: A model that describes the flow of material and associated radioactivity

during recycle.

mean: The arithmetic average of a population— i.e., the sum of all of the values in the population

divided by the number in the population. (see geometric mean)

median: Strictly, a value in a distribution such that there is a 0.5 probability that the actual value

of the variable is less than that value. In common usage, it is the value in a distribution

such that half of the values are bigger, and half of the values are smaller.

model: A mathematical abstraction of an ecological or biological system, sometimes including

specific numerical values for the parameters of the system. (NCRP 1984).

parameter: Any one of a set of variables in a model whose values determine model predictions. 

(Till and Meyer 1983).

*partitioning: The differential movement of one material as compared to another material. For

this analysis, partitioning is used in the context of the steel refining process, specifically

during melting in a furnace.

mass partitioning: the redistribution of mass during melting in a refinery furnace. The

mass of the material in a furnace is distributed to refined metal, slag, and dust

during the refining process.

element partitioning: the redistribution of chemical elements during melting in a refinery

furnace. The elements in the material in a furnace are distributed to refined metal,

slag, dust, and offgas during the refining process depending on their chemical

characteristics.

percentile: Strictly, a value in a distribution, expressed as a percentage, such that there is a given

probability that any value in the distribution is less than that value. In common usage, it is

the value in a distribution such that the given fraction (percentage) of values are less than

that value. For example, 95% of the values in a distribution are less than the 95-percentile

value.

probabilistic model: A system whose input and output is expressed as a distribution of possible

values. The output distribution results from uncertainty in the input parameters.

probability distribution: A set of all possible values of a parameter, and their associated

probability. The probability distributions used in this analysis are uniform, triangular,

normal, and lognormal.
Glossary

NUREG-1640 glossary-4

progeny: The nuclide resulting from the radioactive disintegration of a radionuclide, formed

either directly or as the result of successive transformations in a radioactive series. 

Progeny may be either radioactive or stable.

radionuclide: An atom that, due to its atomic instability, undergoes spontaneous nuclear

disintegration. Nuclear disintegration is accompanied by the emission of charged particles

and/or photons, and results in the formation of another, distinct atom (see progeny).

radionuclide-dependent parameter: A parameter whose value is specific to a given radionuclide,

and therefore may be different for every radionuclide. 

radionuclide-independent parameter: A parameter whose value is not specific to a given

radionuclide, and therefore is the same for every radionuclide.

realistic: Typical of a real-life situation, and therefore likely to be observed in real life. An

accurate representation of a reasonably foreseeable real-life situation.

*recycle: Conversion of materials (i.e., steel, copper, aluminum, concrete) present in components

from a nuclear facility to form new products through normal industrial processes, which

would then be available in the public sector. 

*refining: In the context of clearance of equipment and material, refining means melting in a

furnace at a metals refinery. Refining results in the production of the co-products refined

metal, slag, baghouse dust, and off-gas. 

*reuse: Transfer of a functional component or material from a nuclear facility without any

processing, to some other application where it would be used to carry out its original

function.

saturated zone: That portion of porous ground media in which the interconnecting interstices are

filled with water. (Till and Meyer 1983)

*scrap material: manufactured items or parts that are no longer useful for their original purpose

that have value as material for reprocessing.

secondary ingestion: accidental or unintentional ingestion of material (also sometimes referred to

as “inadvertent ingestion).” In this analysis, secondary ingestion applies to the

unintentional ingestion of soil and dust.

sensitivity: The mathematical sensitivity of the model predictions to selected perturbations of

model parameters. (NCRP 1984)

sensitivity analysis: Identification of the relative contribution of the uncertainty in a given model

component to the total uncertainty in the model result. (NCRP 1996)
Glossary

glossary-5 NUREG-1640

spreadsheet: A calculational computer software application.

total effective dose equivalent (TEDE): the sum of the deep-dose equivalent (for external

exposures) and the committed effective dose equivalent (for internal exposures). 

(10CFR20)

uncertainty: The lack of sureness or confidence in the predictions of models. (NCRP 1984)

uncertainty analysis: The computation of the total uncertainty induced in the output by

quantified uncertainty in the inputs and models, and the attributes of the relative

importance of the input uncertainties in terms of their contributions. (NCRP 1996)

uniform distribution: A distribution of values such that all values are equally likely to occur, or

alternatively, equally likely to be sampled during conduct of an uncertainty analysis.

unsaturated zone: The portion of porous media in the ground where the interconnecting

interstices are only partially filled with fluid. (NCRP 1984)