NUREG-1854

NRC Staff Guidance for

Activities Related to

U.S. Department of Energy

Waste Determinations

Draft Final Report

for Interim Use

U.S. Nuclear Regulatory Commission

Office of Federal and State Materials and

Environmental Management Programs

Washington, DC 20555-0001
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NUREG-1854

NRC Staff Guidance for

Activities Related to

U.S. Department of Energy

Waste Determinations

Draft Final Report

for Interim Use

Manuscript Completed: August 2007

Date Published: August 2007

Prepared by

H. Arlt, A. Bradford, N. Devaser, D. Esh, M. Fuller, A. Ridge, (NRC)

B. Brient, P. LaPlante, P. Mackin, E. Pearcy (CNWRA)

D. Turner, J. Winterle (CNWRA)

Center for Nuclear Waste Regulatory Analyses

Southwest Research Institute

6220 Culebra Road

San Antonio, TX 78238-5166

Division of Waste Management and

Environmental Protection

Office of Federal and State Materials and

Environmental Management Programs

Washington, DC 20555-0001

ABSTRACT

This document provides U.S. Nuclear Regulatory Commission (NRC) staff guidance for

conducting activities related to waste determinations. Waste determinations are evaluations

performed by the U.S. Department of Energy and are used to assess whether certain wastes

resulting from the reprocessing of spent nuclear fuel can be considered low-level waste and

managed accordingly. This guidance document applies to NRC activities that may be

conducted for the Savannah River Site (SRS) in South Carolina and the Idaho National

Laboratory (INL) in Idaho pursuant to the Ronald W. Reagan National Defense Authorization

Act for Fiscal Year 2005 (NDAA), as well as the Hanford site in Washington and the West Valley

site in New York. The guidance document discusses the background and history of waste

determinations, the different applicable criteria and how they are applied and evaluated, the

review of associated performance assessments and inadvertent intruder analyses, the removal

of highly radioactive radionuclides, and NRC's monitoring activities that will be performed at

SRS and INL in accordance with the NDAA.

iii

CONTENTS

Section Page

A B S T R A C T ................................................................. iii

LIST O F FIG U R ES ............................................................ ix

LIST O F TABLES ............................................................ x

ABBREVIATIONS/ACRONYMS ................................................. xi

IN TR O D UC TIO N ........................................................... xiii

Forew ord ................ ........................................... xiii

How To Use This Staff Guidance Document ............................... xvii

Structure of the Staff Guidance Document ................................. xviii

Updating the Staff Guidance Document ................................... xviii

Background ......................................................... xviii

The Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 ... xxi

Role of the U.S. Nuclear Regulatory Commission ............................ xxi

R eferences ......................................................... xxiii

SITE-SPECIFIC AND GENERAL INFORMATION ........................... 1-1

1.1 Site-Specific System Description Information ......................... 1-1

1.1.1 Brief Description and Scope .................................. 1-1

1.1.2 Facility Description ......................................... 1-2

1.1.3 Site Description ............................................ 1-3

1.1.3.1 Site Location and Description ......................... 1-4

1.1.3.2 Land Use ......................................... 1-4

1.1.3.3 Meteorology and Climatology ......................... 1-5

1.1.3.4 Geology and Seismology ............................. 1-6

1.1.3.5 Hydrology ........................................ 1-6

1.1.3.6 Radiological Status ................................. 1-7

1.2 Applicable Sites and W aste Criteria .................................. 1-8

1.3 Prior W aste Determinations ........................................ 1-9

1.4 References ..................................................... 1-9

2 INCIDENTAL WASTE CRITERIA ........................................ 2-1

2.1 Criteria from the Ronald W. Reagan National Defense Authorization Act

for Fiscal Year 2005 (Section 3116) .................................. 2-1

2.2 Criteria from DOE Order 435.1 ....................................... 2-1

2.3 Criteria from the West Valley Policy Statement .......................... 2-3

2.4 Com parison of Criteria ............................................ 2-3

2.4.1 "Waste Incidental to Reprocessing" and "Non-High-Level Waste" ...... 2-3

2.4.2 "Highly Radioactive Radionuclides" and "Key Radionuclides".......... 2-4

2.4.3 "Maximum Extent Practical" and "Maximum Extent Technically and

Economically Practical" .............. *.............. 2-4

2.4.4 Differences in Concentration Limits ............................. 2-5

2.4.5 Alternatives to the Performance Objectives of 10 CFR Part 61,

S ubpart C ................................................ 2-5

v
CONTENTS (continued)

Section Page

2.5 Does Not Require Disposal in a Geologic Repository ..................... 2-6

2.5.1 Areas of Review .................... .................... ..... 2-6

2.5.2 Review Procedures .......................................... 2-6

2.6 Removal of Radionuclides ......................................... 2-6

2.7 Compliance With Performance Objectives of 10 CFR Part 61, Subpart C ..... 2-7

2.8 References ........................................... ......... 2-8

3 RADIONUCLIDE REMOVAL AND CONCENTRATION LIMITS ................... 3-1

3.1 Inventory of Radionuclides in Waste .................................. 3-2

3.1.1 Areas of Review ........................................... 3-2

3.1.2 Review Procedures ......................................... 3-3

3.2 Identification of Highly Radioactive Radionuclides ...................... 3-5

3.2.1 Areas of Review ........................................... 3-5

3.2.2 Review Procedures ..................................... 3-7

3.3 Radionuclide Removal Technology Selection and Implementation .......... 3-8

3.3.1 Areas of Review ........................................... 3-9

3.3.2 Review Procedures ........................................ 3-12

3.4 Cost-Benefit Analysis ............................................ 3-14

3.4.1 Areas of Review .......................................... 3-15

3.4.2 Review Procedures ........................................ 3-19

3.5 Concentration Lim its ............................................. 3-21

3.5.1 Areas of Review ...................................... 3-22

3.5.1.1 Concentration Averaging ............................ 3-22

3.5.1.2 Consultation for Disposal Plans for Waste Exceeding

Class C .......... ........................... 3-38

3.5.2 Review Procedures ........................................ 3-38

3.6 References .................................................... 3-39

4 PERFORMANCE ASSESSMENT ....................................... 4-1

4.1 Scenario Selection and Receptor Groups .............................. 4-3

4.1.1 Areas of Review ................................... ....... 4-3

4.1.1.1 Period of Performance and Institutional Controls .......... 4-3

4.1.1.2 Scenario Identification ............................... 4-4

4.1.1.3 Identification of Relevant Features and Processes ......... 4-5

4.1.1.4 Receptor Characteristics ............................. 4-7

4.1.2 Review Procedures ......................................... 4-8

4.2 General Technical Review Procedures ............................... 4-10

4.2.1 System Description Review Procedures ........................ 4-11

4.2.2 Data Sufficiency Review Procedures ........................ 4-12

4.2.3 Data Uncertainty Review Procedures ........................ 4-13

4.2.4 Model Uncertainty Review Procedure .......................... 4-14

4.2.5 Model Support Review Procedure ............................. 4-15

4.3 Specific Technical Review Procedures ............................... 4-15

4.3.1 Climate and Infiltration ...................................... 4-16

4.3.1.1 Areas of Review .................................. 4-16

vi
CONTENTS (continued)

Section Page

4.3.1.1.1 Current Meteorology and

Precipitation at the Site ................. 4-16

4.3.1.1.2 Current Infiltration and Unsaturated Zone Flow

at the Site ............................ 4-16

4.3.1.1.3 Projected Meteorology and Precipitation

at the Site ............................ 4-17

4.3.1.1.4 Projected Infiltration and Unsaturated Zone Flow

at the Site .......... ................. 4-18

4.3.1.2 Review Procedures ................................ 4-18

4.3.2 Engineered Barriers ...................... ................. 4-21

4.3.2.1 Areas of Review .................................. 4-21

4.3.2.1.1 Features and Dimensions of the Engineered

Barrier System(s) ..................... 4-21

4.3.2.1.2 Performance of Engineered Barriers ....... 4-22

4.3.2.1.3 Integration and Interaction of Materials ..... 4-23

4.3.2.1.4 Construction Quality and Testing .......... 4-23

4.3.2.1.5 Modeling of Engineered Barriers .......... 4-23

4.3.2.2 Review Procedures ....................... .. 4-24

4.3.3 Source-Term/Near-Field Release ............................. 4-27

4.3.3.1 Areas of Review .................................. 4-28

4.3.3.1.1 Inventory of Radionuclides in Waste ....... 4-28

4.3.3.1.2 Degradation and Release From Wasteforms. 4-29

4.3.3.1.3 Source-Term Models ................... 4-29

4.3.3.1.4 Chemical Environment .................. 4-30

4.3.3.1.5 Gaseous Releases ..................... 4-30

4.3.3.2 Review Procedures ................................ 4-30

4.3.4 Radionuclide Transport ..................................... 4-32

4.3.4.1 Areas of Review .................................. 4-32

4.3.4.1.1 Air Transport ......................... 4-33

4.3.4.1.2 Surface Water Transport ................ 4-33

4.3.4.1.3 Transport in the Unsaturated Zone ........ 4-33

4.3.4.1.4 Transport in the Saturated Zone .......... 4-34

4.3.4.2 Review Procedures ... ............................ 4-35

4.3.5 Biosphere Characteristics and Dose Assessment ................. 4-38

4.3.5.1 Areas of Review .................................. 4-38

4.3.5.1.1 Exposure Pathways and Dose Modeling .... 4-39

4.3.5.1.2 Site-Specific Input Parameter Values ...... 4-39

4.3.5.2 Review Procedures ................................ 4-40

4.4 Computational Models and Computer Codes .......................... 4-40

4.4.1 Areas of Review .......................................... 4-4 0

4.4.1.1 Modeling Approach: Probabilistic or Deterministic ........ 4-41

4.4.1.2 Model Development ................................ 4-42

4.4.2 Review Procedures ........................................ 4-42

4.5 Uncertainty/Sensitivity Analysis for Overall Performance Assessment ....... 4-43

4.5.1 Areas of Review .......................................... 4-4 3

vii
CONTENTS (continued)

Section Page

4.5.2 Review Procedures .................................... 4-45

4.6 Evaluation of Model Results ....................................... 4-46

4.6.1 Areas of Review .......................................... 4-46

4.6.1.1 Defining Barrier Contributions ...................... 4-46

4.6.1.2 Evaluating Intermediate Model Results ................. 4-47

4.6.1.3 Final Dose Calculations ............................. 4-47

4.6.1.4 Comparison to Performance Objectives ................ 4-48

4.6.2 Review Procedures ....................................... 4-49

4.7 ALARA Analysis ................................................ 4-52

4.7.1 Areas of Review .......................................... 4-52

4.7.2 Review Procedures ....................................... 4-52

4.8 References .................................................... 4-53

5 INADVERTENT INTRUSION ........................................... 5-1

5.1 Areas of Review ................................................. 5-1

5.1.1 Assessment of Inadvertent Intrusion ............................ 5-1

5.1.2 , Intruder Protection Systems .................................. 5-2

5.1.3 Types of Scenarios Considered in the Intruder Analysis ............. 5-2

5.1.3.1 Intruder-Resident Scenario ........................... 5-3

5.1.3.2 Intruder-Agriculture Scenario ......................... 5-3

5.1.3.3 Intruder-Recreational Hunting/Fishing Scenario ........... 5-3

5.1.3.4 Intruder-Driller Scenario ............................. 5-3

5.1.3.5 Intruder-Construction Scenario ........................ 5-4

5.1.3.6 Other Scenarios ................................... 5-4

5.2 Review Procedures ............................................... 5-4

5.3 References ..................................................... 5-6

6 PROTECTION OF INDIVIDUALS DURING OPERATIONS .................... 6-1

6.1 Areas of Review ................................................. 6-1

6.2 Review Procedures ............................................... 6-2

7 SITE STABILITY, WASTE STABILITY, AND FACILITY STABILITY ............. 7-1

7.1 Areas of Review ............................................ 7-1

7.1.1 Siting Considerations .................. ................ 7-1

7.1.1.1 Flooding and Water Table Fluctuation .................. 7-2

7.1.1.2 Surface Geologic Processes .......................... 7-2

.7.1.1.3 Subsurface Geologic Processes ................... ... 7-3

7.1.1.4 Other Processes ................................... 7-3

7.1.2 W aste and Facility Stability ................................... 7-4

7.2 Review Procedures ................................................ 7-5

7.3 References .... ................................................ 7-9

8 QUALITY ASSURANCE PROGRAM ..................................... 8-1

8.1 Areas of Review ................................................. 8-1

8.2 Review Procedures ............................................... 8-1

viii
CONTENTS (continued)

Section Page

8.2.1 Data Validity Review Procedures ............................ 8-1

8.2.2 Software Selection and Development Review Procedures ........... 8-2

8.2.3 Analysis Review Procedures .................................. 8-3

8.3 R eferences ..... .................. ............................. 8-4

9 DOCUMENTING THE RESULTS OF THE REVIEW ......................... 9-1

9.1 General Approach to Documenting Waste Determination Reviews .......... 9-1

9.2 Request for Additional Information ................................... 9-1

9.3 Technical Evaluation Report ........................................ 9-1

9.4 Public Availability and Project Numbers ............................... 9-2

9.5 References ..................................................... 9-2

10 NDAA COMPLIANCE MONITORING .................................... 10-1

10.1 Overall Approach and Scope ...................................... 10-1

10.2 Coordinating W ith the Covered State ................................ 10-6

10.3 Compliance Monitoring Activities . ................................ 10-9

10.3.1 Technical Review Approach ................................ 10-10

10.3.2 Onsite Observation Approach .............................. 10-12

10.4 Documentation of Findings and Reporting .......................... 10-12

10.4.1 Onsite Observation Reports ................ ............... 10-12

10.4.2 Periodic Compliance Monitoring Reports ..................... 10-13

10.4.3 Noncompliance Notification Letters .......................... 10-14

10.5 References .................................................. 10-17

APPENDIX A: SECTION 3116 OF THE RONALD W. REAGAN NATIONAL DEFENSE

AUTHORIZATION ACT FOR FISCAL YEAR 2005 ................. A-1

APPENDIX B: CALCULATION TO DEVELOP BENCHMARK

AVERAGING EXPRESSIONS ................................. B-1

APPENDIX C: PUBLIC COMMENTS, ADVISORY COMMITTEE ON NUCLEAR

WASTE COMMENTS AND RESPONSES ....................... C-1

LIST OF FIGURES

3-1 Comparison of Key Assumptions of (a) the Intruder Excavation Scenario

for Part 61 and (b) Intruder Scenarios for Tank Residual Waste ............... 3-29

4-1 Geometric Relationship of the Disposal Units, Disposal Area, and Buffer

Zone of a Disposal Site ................................................ 4-8

10-1 Schematic of NRC's Compliance Monitoring Approach ..................... 10-7/8

10-2 A Control Chart Example ............................................ 10-11

10-3 Topical Areas Expected in the Periodic Compliance Monitoring Report ........ 10-15

ix
CONTENTS (continued)

Section Page

LIST OF TABLES

3-1 Potential Costs and Benefits Associated With Performing Additional

Radionuclide Removal Beyond Removal Performed to Meet the Applicable

Performance Objectives .............................................. 3-16

3-2 Assumed Conditions for the Four Scenarios Used to Develop

Averaging Expressions .............. ............................ 3-31

10-1 U.S. Nuclear Regulatory Commission's Primary Monitoring Activities for

Each of the Performance Objectives .................................... 10-3

10-2 Types of Notification Letters .......................................... 10-16

x
ACNW

ADAMS

ALARA

BTP

CERCLA

CFR

DNFSB

DOE

EPA

ET

HLW

IA

ICRP

INL

Kd

LLW

MOU

NAS

NDAA

NEPA

NRC

NRDC

NYSERDA

OMB

ABBREVIATIONS/ACRONYMS

Advisory Committee on Nuclear Waste

Agencywide Documents Access and Management System

As Low As Is Reasonably Achievable

Branch Technical Position

Comprehensive Environmental Response, Compensation, and Liability Act

Code of Federal Regulations

Defense Nuclear Facilities Safety Board

U.S. Department of Energy

U.S. Environmental Protection Agency

Evapotranspiration

High-level Waste

Interagency Agreement

International Commission on Radiological Protection

Idaho National Laboratory

Distribution coefficient

Low-level Waste

Memorandum of Understanding

National Academy of Sciences

Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005

National Environmental Policy Act

U.S. Nuclear Regulatory Commission

Natural Resources Defense Council

New York State Energy Research and Development Authority

Office of Management and Budget

xi
PA Performance Assessment

RAI Request for Additional Information

RMEI Reasonably Maximally Exposed Individual

SRM Staff Requirements Memorandum

SRP Standard Review Plan

SRS Savannah River Site

TEDE Total Effective Dose Equivalent

TER Technical Evaluation Report

TRU Transuranic

USGS U.S. Geological Survey

WIR Waste Incidental to Reprocessing

WVDP West Valley Demonstration Project

xii
1 INTRODUCTION

2

3 Foreword

4

5 In October 2004, the Ronald W. Reagan National Defense Authorization Act for Fiscal Year

6 2005 (NDAA) was enacted. Section 3116 of the NDAA gave the U.S. Nuclear Regulatory

7 Commission (NRC) new responsibilities with respect to U.S. Department of Energy (DOE)

8 waste management activities for certain radioactive material resulting from the reprocessing of

9 spent nuclear fuel within the States of South Carolina and Idaho (see Appendix A for the text of

10 Section 3116 of the NDAA). NRC's responsibilities include consulting with DOE in DOE's

11 determination of whether the waste is not high-level waste (HLW), as well as monitoring DOE's

12 disposal actions for these wastes. The concept behind this "incidental" waste is that some

13 radioactive material, resulting from the reprocessing of spent nuclear fuel, does not need to be

14 disposed of as HLW in a geologic repository. This is because the residual radioactive

15 contamination of the material, if properly controlled, is sufficiently low so that it does not

16 represent a hazard to public health and safety. Consequently, incidental waste is not

17 considered to be HLW but instead is low-level waste (LLW) or, in DOE's waste classification

18 scheme, transuranic (TRU) waste. DOE uses technical analyses that are documented in a

19 "waste determination" to evaluate whether waste is incidental, or alternatively, is HLW. A waste

20 determination is DOE's analysis of whether the waste will meet the applicable incidental

21 waste criteria.

22

23 Prior to passage of the NDAA, DOE would periodically request that NRC provide technical

24 advice for specific waste determinations. The NRC staff reviewed DOE's waste determinations

25 to assess whether there were sound technical assumptions, analyses, and conclusions with

26 regard to meeting the applicable incidental waste criteria. The staff typically evaluated DOE27 submitted information, generated requests for additional information (RAls), met with DOE

28 representatives to discuss technical questions and issues, and documented the final review

29 results in Technical Evaluation Reports (TERs). NRC's advice was provided in an advisory

30 manner and did not constitute regulatory approval. Similarly, NRC reviews of DOE waste

31 determinations under the NDAA are in a consultative role; NRC does not have regulatory

32 authority over DOE. These types of reviews were completed for waste intended to be removed

33 from tanks at Hanford (NRC, 1997a), tank closure at the Savannah River Site (SRS) (NRC,

34 2000a), waste intended to be removed from tanks at Idaho National Laboratory (INL) (NRC,

35 2002a), and tank closure at INL (NRC, 2003a).

36

37 Because the NRC expects NDAA enactment to increase the number of waste determinations

38 submitted for NRC review, NRC decided to develop NRC Staff Guidance for Activities Related

39 to U.S. Department of Energy Waste Determinations (guidance document or document). This

40 document will provide NRC staff guidance on conducting a technical review of a waste

41 determination, and monitoring activities under the NDAA, and it will help ensure consistency

42 across different reviews and different reviewers. Because the technical aspects of NRC's waste

43 determination reviews are expected to be similar for all four sites regardless of whether the site

44 is covered by the NDAA, this guidance document will address reviews for SRS, INL, the

45 Hanford site, and the West Valley Demonstration Project.

46

47

48

xiii
1 In November 2005, NRC held a public scoping meeting in Rockville, Maryland, to obtain public

2 input on the scope of the (then) draft Standard Review Plan (SRP). In addition, NRC published

3 a Federal Register notice on November 2, 2005, announcing the scoping meeting and stating

4 that written comments on the scope of the (then) draft SRP would be accepted until

5 November 25, 2005 (NRC, 2005a). The transcript of the scoping meeting is publicly available

6 in NRC's Agencywide Document Access and Management System (ADAMS) (NRC, 2005b).

7 NRC received written comments on the proposed scope of the SRP from the SRS Citizens

8 Advisory Board (CAB, 2005), the South Carolina Department of Health and Environmental

9 Control (SCDHEC, 2005), and the Washington State Department of Ecology (Washington,

10 2005), and the comments are publicly available in ADAMS.

11

12 In December 2005, the NRC published a Federal Register notice issuing draft interim guidance

13 for performing concentration averaging for waste determinations (NRC, 2005c). The Federal

14 Register notice was issued due to high stakeholder interest in obtaining the guidance as soon

15 as practicable due to the ongoing development of waste determinations. The draft interim

16 guidance was open for public comment until January 31, 2006. NRC received comment letters

17 from the State of Idaho Department of Environmental Quality (Idaho, 2006), the State of

18 Washington Department of Ecology (Washington, 2006), the State of Oregon Department of

19 Energy (Oregon, 2006), Washington Closure Hanford (WCH, 2006), the Natural Resources

20 Defense Council (NRDC, 2006), and members of the public (Greeves and Lieberman, 2006),

21 and the comment letters are publicly available in ADAMS. The concentration averaging

22 guidance that is included in this draft guidance document has been revised from the initial draft

23 document based on stakeholder comments (see Section 3.5.1.1).

24

25 This document was published for interim use and comment in May 2006. NRC accepted public

26 comments on the document until July 31, 2006. NRC received 12 comment letters during the

27 public comment period, which are addressed in this revision. Comments were received from

28 four State agencies, two public interest groups, and five individuals, and the DOE. In addition to

29 the public comments, the staff also received comments and recommendations from the NRC

30 Advisory Committee on Nuclear Waste (ACNW). After consideration of the purpose of

31 NUREG-1854, as well as in response to comments, the NRC has revised the name of the

32 document from a "standard review plan" (SRP) to a "staff guidance document." This revision

33 was made to better reflect the document's purpose. An SRP is typically used by the staff to

34 review licensing actions. Since DOE waste determinations are not licensing actions, the

35 document is being issued as staff guidance. However, the level of detail and the general

36 content of the document remain unchanged.

37

38 NUREG-1854 is a "Draft Final Document for Interim Use" because revisions to the document

39 are anticipated in the fairly near future. NRC, DOE, and the covered States are, at the time of

40 this document's publication, working to resolve a number of generic technical issues (GTI) that

41 will enable all parties to more efficiently develop and review future draft waste determinations.

42 When the GTIs are resolved, this NRC Staff Guidance Document will be updated to include the

43 GTI resolution discussions.

44

45

xiv
1 This NRC Staff Guidance Document provides direction to the NRC staff and does not set forth

2 regulatory requirements for NRC nor DOE, and compliance with this review plan is not required.

3 This NRC Staff Guidance Document will be revised and updated periodically to clarify the

4 content or incorporate modifications as needed.

5

6

7

8

9

10- -

11 La amper, Directo12 Division f Waste Management and

13 Envirdnmental Protection

14 Office of Federal and State

15 Materials and Environmental

16 Management Programs

xv

1 How To Use This Staff Guidance Document

2

3 This document provides NRC staff guidance for evaluating DOE-developed waste

4 determinations for SRS, INL, Hanford, and West Valley. The guidance document provides

5 elements the staff should review to determine whether there is reasonable assurance that the

6 appropriate criteria can be met. This guidance document also provides information about the

7 NRC's role in the waste determination process and NRC's monitoring activities under

8 the NDAA.

9

10 This document does not set forth regulatory requirements for NRC nor DOE, and compliance

11 with this guidance document is not required. Methods and approaches different from those

12 described here could be acceptable to demonstrate that there is reasonable assurance that the

13 appropriate criteria can be met. Waste determinations typically use the performance objectives

14 of 10 CFR Part 61, Subpart C, as a criterion that must be met (see Section 2); references to

15 other parts of the regulations in 10 CFR Part 61 (i.e., other than Subpart C) are included only to

16 provide information and guidance as they relate to the staff reviews.

17

18 Because waste determinations are based on meeting the performance objectives of

19 10 CFR Part 61, Subpart C, or comparable performance objectives, this guidance document

20 can help reviewers assess whether there is reasonable assurance that public health and safety

21 can be protected as described in 10 CFR Part 61, Subpart C. The term "reasonable assurance"

22 is the standard specified in the general requirement of 10 CFR Part 61, Subpart C (§61.40). In

23 the context of waste disposal activities, NRC staff develops reasonable assurance by

24 (1) evaluating the technical bases for the predicted performance of a disposal facility and

25 resulting potential doses to hypothetical receptors, (2) evaluating sources of uncertainty and

26 conservatism in -supporting analyses, and (3) determining whether, given the uncertainties, the

27 conclusions of the analysis are sound. In the review, the staff often performs independent

28 analyses to identify important assumptions in DOE's analysis so that it can assess the degree to

29 which the staff agrees with DOE's assumptions. NRC has previously indicated (NRC, 2001) the

30 term "reasonable assurance" is not meant to indicate a specific statistical standard. Specifically,

31 NRC noted that the term "reasonable assurance" is not meant to imply a requirement that

32 extreme values be used in analyses or that compliance be based on extreme values of

33 predicted dose distributions. NRC also noted that the term "reasonable assurance" was not

34 meant to indicate a significantly different standard than would be indicated by the term

35 "reasonable expectation." Regardless of the terminology applied, the review's objective is to

36 develop confidence that public health and safety will be protected.

37

38 This risk-informed and performance-based guidance document ensures that the NRC review is

39 focused on those aspects most important to health and safety. The staff intends to incorporate

40 risk insights into the review process and into the development of the staff's conclusions.

41 Because this guidance document will be used to review a potentially large number of different

42 types of waste determinations, its scope is general enough to allow the NRC staff to apply the

43 guidance to a wide range of DOE waste determinations while also containing sufficient detail to

44 ensure thoroughness and consistency of the staffs reviews.

45

46 Section 1 of this guidance document covers the site information needed to provide context to

47 the reviewer and to support a performance assessment. Section 2 discusses the incidental

48 waste criteria. Section 3 provides information on assessing removal of radionuclides and on

49 estimating waste classification. Sections 4-7 address the performance objectives of

xvii
1 10 CFR Part 61, Subpart C. Section 4 of the document provides guidance for the staff review of

2 the long-term performance assessment to evaluate the protection of the general population

3 (10 CFR 61.41). Section 5 provides guidance for the staff review of assessments of potential

4 radiation exposures to an inadvertent intruder (10 CFR 61.42). The review procedures

5 presented in Section 6 are for assessing compliance with the radiation protection standards

6 during operations (10 CFR 61.43). Section 7 of the document provides guidance for assessing

7 long-term site stability (10 CFR 61.44). Guidance for assessing the implementation of DOE

8 quality assurance programs is in Section 8, and a brief summary of how the NRC review will be

9 conducted and documented is provided in Section 9. Information regarding monitoring activities

10 is provided in Section 10.

11

12 Structure of the Staff Guidance Document

13

14 Where applicable, sections of this guidance document are divided into two subsections that

15 describe the steps of the review process.

16

17 Areas of Review. This subsection describes the scope of the review (i.e., what is to be

18 reviewed). It briefly discusses the specific types of technical information and analyses that

19 should be reviewed. The areas listed are intended to be used for broad application; therefore,

20 the listing is not exhaustive and may be supplemented for a given review, as appropriate.

21

22 Review Procedures. This subsection discusses the appropriate review topics and techniques.

23 The reviewer should generally determine that the topics listed in this section are evaluated or

24 that there is adequate technical basis to conclude that a specific topic does not need to be

25 addressed. The reviewer should evaluate whether the information provided is sufficient to

26 support the conclusions presented in the waste determination.

27

28 This guidance document covers a variety of site conditions and facility designs. Pertinent

29 review procedures are contained in each section. Because the reviews are conducted on a

30 case-by-case basis, the reviewer may emphasize particular aspects of each guidance document

31 section as appropriate. Where possible, the proposed review procedures are based on

32 applicable existing NRC guidance and previous NRC experience gained from DOE waste

33 determination reviews.

34

35 Updating the Staff Guidance Document

36

37 This guidance document will be revised and updated periodically to clarify the content or

38 incorporate modifications as the need arises. A revision number and publication date will be

39 issued as needed.

40

41 Background

42

43 The concept of incidental waste, also known as waste-incidental-to-reprocessing (WIR) or

44 non-high-level waste (non-HLW), is that some wastes can be managed based on their risk to

45 human health and the environment, rather than based on the origin of the wastes. With respect

46 to wastes resulting from the reprocessing of spent nuclear fuel, such as the tank residuals at

47 some DOE sites, some are highly radioactive and need to be treated and disposed of as HLW in

48 a geologic repository, but others do not. Incidental waste does not pose the same amount of

49 risk to human health and the environment as HLW and does not need to be disposed of as HLW

xviii
1 to manage the risks that it poses. Consequently, incidental waste is not considered to be HLW.

2 DOE uses technical analyses documented in a "waste determination" to evaluate whether waste

3 is incidental or HLW. A waste determination is DOE's analysis as to whether the waste will

4 meet the applicable incidental waste criteria and usually includes a performance assessment. A

5 performance assessment is a quantitative evaluation of potential releases into the environment

6 and the resultant radiological doses, and the evaluation is often performed using a computer

7 model (or multiple models).

8

9 The concept of incidental waste has been recognized since 1969 when the Atomic Energy

10 Commission, NRC's predecessor agency, issued for comment a draft policy statement

11 regarding the siting of reprocessing facilities in the form of a proposed Appendix D to

12 10 CFR Part 50, which addressed a definition of HLW (AEC, 1969). The draft policy statement

13 provided that certain materials resulting from reprocessing could be disposed of in accordance

14 with 10 CFR Part 20 requirements. Although the draft policy statement did not use the term

15 "incidental," the Commission intended that the term HLW not include certain wastes that were

16 incidental to reprocessing operations. However, when Appendix D was finalized as Appendix F,

17 it did not include the paragraphs on incidental waste, because the Commission wanted to

18 preserve its flexibility as to how such material should be treated. The term "incidental waste"

19 was apparently first used in NRC's 1987 advance notice of proposed rulemaking to redefine the

20 definition of HLW (NRC, 1987). However, in the 1989 final rulemaking action on disposal of

21 radioactive waste, the Commission did not redefine HLW (NRC, 1989).

22

23 In 1990, the States of Oregon and Washington petitioned the Commission to amend

24 10 CFR Part 60 to redefine HLW. The petition concerned whether Hanford tank waste was

25 subject to NRC licensing jurisdiction. In response to the petition, the Commission approved

26 specific criteria for determining whether waste was incidental and issued a Staff Requirements

27 Memorandum (SRM) dated February 16, 1993, in response to SECY-92-391, "Denial of

28 PRM 60-4: Petition for Rulemaking from the States of Washington and Oregon Regarding

29 Classification of Radioactive Waste at Hanford." NRC published the criteria in the Federal

30 Register as part of the petition denial, as follows (NRC, 1993):

31

32 (1) The waste has been processed (or will be further processed) to remove

33 key radionuclides to the maximum extent that is technically and

34 economically practical,

35

36 (2) The waste will be incorporated in a solid physical form at a concentration

37 that does not exceed the applicable concentration limits for Class C

38 low-level radioactive waste (LLW) as set out in Title 10 of the Code of

39 Federal Regulations (10 CFR) Part 61, and

40

41 (3) The waste is to be managed, pursuant to the Atomic Energy Act, so that

42 safety requirements comparable to the performance objectives set out in

43 10 CFR Part 61, are satisfied.

44

45 The performanceobjectives of 10 CFR Part 61, Subpart C, include provisions for protecting the

46 general population from releases of radioactivity, protecting individuals from inadvertent

47 intrusion, and protecting individuals during operations. The performance objectives also include

48 provisions for the stability of the site after closure.

49

xix
1 In a May 30, 2000, SRM on SECY-99-0284, "Classification of Savannah River Residual Tank

2 Waste as Incidental," the Commission indicated that a more performance-based approach

3 should be taken to determine whether waste could be classified as incidental (NRC, 2000b). In

4 effect, cleanup to the maximum extent that is technically and economically practical and

5 demonstration that performance objectives could be met (consistent with those which the

6 Commission demands for the disposal of LLW) should adequately protect the public health and

7 safety and the environment. In the Final Policy Statement for the Decommissioning Criteria for

8 the West Valley Demonstration Project at the West Valley Site, the Commission adopted this

9 performance-based approach and stated the criteria that should be applied to the incidental

10 waste determinations at West Valley, as follows (NRC, 2002b):

11

12 (1) The waste should be processed (or should be further processed) to remove

13 key radionuclides to the maximum extent that is technically and

14 economically practical; and

15

16 (2) The waste should be managed so that safety requirements comparable to

17 the performance objectives in 10 CFR Part 61, Subpart C, are satisfied.

18

19 In July 1999, DOE issued DOE Order 435.1, "Radioactive Waste Management" and the

20 associated Manual, DOE M 435.1-1, "Radioactive Waste Management Manual," both of which

21 were subsequently revised in 2001 (DOE 2001a,b). DOE M 435.1-1 states that waste

22 determined to be incidental to reprocessing is not HLW and shall be managed in accordance

23 with the requirements for TRU waste or LLW if it meets appropriate criteria. DOE M 435.1-1

24 discusses DOE's incidental waste evaluation process and the criteria for determining whether

25 waste is incidental to reprocessing.

26

27 Prior to the passage of the NDAA (see the discussion that follows), DOE had periodically

28 requested that NRC provide technical reviews of specific waste determinations. NRC provided

29 technical assistance and advice to DOE regarding DOE's waste determinations and did not

30 provide regulatory approval for DOE's actions. NRC's reviews were generally performed by the

31 Office of Nuclear Material Safety and Safeguards under site-specific reimbursable Interagency

32 Agreements (lAs) and Memoranda of Understanding (MOUs).

33

34 The staff reviewed DOE's waste determinations to assess whether DOE's technical

35 assumptions, analyses, and conclusions were reasonable and whether there was reasonable

36 assurance that the applicable criteria could be met. In general, the staff examined technical

37 areas such as estimated radionuclide inventory, technology alternatives, performance

38 assessment methodology, engineered system performance, infiltration, release and transport

39 parameters, receptor scenarios and assumptions, and uncertainty and sensitivity analysis. The

40 staff typically evaluated DOE-submitted information, generated requests for additional

41 information (RAIs), met with DOE representatives to discuss technical questions and issues,

42 and documented the final review results in Technical Evaluation Reports (TERs). Typically, the

43 staff provided the associated MOUs, lAs, and TERs to the Commission for review before taking

44 action. In addition to the review of the SRS tank closure methodology discussed above (NRC,

45 1999), the staff developed Commission papers for reviews of incidental waste determinations

46 for waste intended to be removed from tanks at Hanford (NRC, 1997b), sodium-bearing wastes

47 at the Idaho National Laboratory (INL) (NRC, 2002c), and tank farm closure at INL (NRC,

48 2003b). After completing any Commission-directed changes, the NRC staff transmitted the final

49 TERs to DOE (NRC, 1997a, 2000a, 2002a, 2003a).

xx
1 The Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005

2

3 In 2004, Senator Lindsey Graham of South Carolina introduced legislation that would allow DOE

4 to use a process similar to the incidental waste process in DOE Order 435.1 at the Savannah

5 River Site (SRS). During the development of the legislation, Congress inquired about the

6 NRC's position on incidental waste and the proposed legislation, and the Commission

7 responded in letters to Senator Inhofe on May 18, 2004, and Senator Jeffords on July 15, 2004

8 (NRC, 2004a,b).

9

10 Congress passed the NDAA on October 9, 2004, and the President signed it on October 28,

11 2004. Section 3116 of the NDAA allows DOE to continue to use an incidental waste process to

12 determine that waste is not HLW; however, the NDAA is applicable to only South Carolina and

13 Idaho and does not apply to waste transported out of these States. The NDAA requires that

14 (1) DOE consult with NRC on its non-HLW determinations and plans-and (2) NRC, in

15 coordination with the State, monitor disposal actions DOE takes to assess compliance with NRC

16 regulations in 10 CFR Part 61, Subpart C. If NRC determines that any disposal actions DOE

17 takes are not in compliance, NRC shall inform DOE, the State, and Congressional

18 subcommittees as soon as practicable. In addition, the NDAA provides for judicial review of any

19 failure of NRC to carry out its monitoring responsibilities. The NDAA is provided in Appendix A

20 of this guidance document.

21

22 The criteria contained in the NDAA for determining whether waste is non-HLW are similar to the

23 incidental waste criteria previously used by NRC and specify that such waste

24

25 (1) Does not require permanent isolation in a deep geologic repository for spent

26 fuel or HLW;

27

28 (2) Has had highly radioactive radionuclides removed to the maximum extent

29 practical; and

30

31 (3)A Does not exceed concentration limits for Class C low-level waste

32 (LLW) and will be disposed of in compliance with the performance

33 objectives in 10 CFR Part 61, Subpart C; or

34

35 (3)B Exceeds concentration limits for Class C LLW but will be disposed of

36 in compliance with the performance objectives of 10 CFR Part 61,

37 Subpart C, and pursuant to plans developed by DOE in consultation

38 with the NRC.

39

40 After NDAA enactment, the NRC staff developed an implementation plan that described how

41 the staff would carry out its new responsibilities. That plan was described in SECY-05-0073,

42 dated April 28, 2005 (NRC, 2005d). The Commission commented on and approved the staffs

43 proposed plans in an SRM dated June 30, 2005 (NRC, 2005e).

44

45 Role of the U.S. Nuclear Regulatory Commission

46

47 The four DOE sites with potential incidental waste are operating under different requirements for

48 waste evaluation and management. The NRC anticipates that SRS and INL will use the NDAA

49 requirements for waste being disposed of in the State, but could decide to use DOE Order 435.1

xxi
1 _ for waste being shipped out of the State or possibly for certain wastes remaining in the State

2 that are not covered by the NDAA (e.g., waste not covered by a State-issued closure plan or

3 permit, as stated in the NDAA). Hanford is not covered under the NDAA and could decide to

4 use the requirements of DOE Order 435.1. West Valley will use NRC's Final Policy Statement

5 for the Decommissioning Criteria for the West Valley Demonstration Project (WVDP) at the

6 West Valley Site (the West Valley Policy Statement) for waste being disposed of onsite, and

7 could decide to use DOE Order 435.1 for waste being sent offsite. Alternatively, DOE may

8 decide to apply the NDAA requirements to all of its sites for consistency. The role of NRC and

9 the scope of the staff's reviews may vary depending on the criteria being applied in a specific

10 waste determination.

11

12 The NDAA applies only to waste remaining in South Carolina and Idaho. Under the NDAA, the

13 NRC has a statutory obligation to provide consultation to DOE for such waste. NRC performs a

14 technical review of DOE's waste determinations and arrives at an independent conclusion as to

15 whether there is reasonable assurance that the NDAA criteria can be met by DOE's waste

16 management approach. However, NRC does not have a regulatory role and the final decision

17 on whether incidental waste meets the criteria rests with the DOE. Guidance on performing

18 technical reviews under the NDAA is provided in this guidance document. Also, NRC must

19 monitor DOE's disposal actions for such waste to assess compliance with the performance

20 objectives of 10 CFR Part 61, Subpart C. The NRC must report any noncompliance to

21 Congressional subcommittees, the State, and DOE as soon as practicable after discovery of the

22 noncompliance. Monitoring is discussed in more detail in Section 10.

23

24 For the West Valley site, NRC's Final Policy Statement for the Decommissioning Criteria for the

25 WVDP at the West Valley Site applies to any residual material remaining at the site, including

26 any incidental waste (NRC, 2002b). Currently at West Valley, DOE is acting as a surrogate for

27 the licensee (the New York State Energy Research and Development Authority), and NRC is in

28 an advisory role with respect to DOE's incidental waste determinations. In providing the

29 incidental waste criteria, the West Valley Policy Statement states that "it is the Commission's

30 expectation that it will apply this criteria at the WVDP at the site following the completion of

31 DOE's site activities" (NRC, 2002b). Guidance on performing technical reviews under the West

32 Valley Policy Statement is provided in this guidance document. For offsite waste disposal, it is

33 DOE's responsibility to determine which criteria are applicable; for example, DOE may decide to

34 apply DOE Order 435.1. Guidance on technical reviews of waste determinations that DOE

35 decides to perform under DOE Order 435.1 also is provided in this document. For waste

36 determinations that DOE decides to perform using DOE Order 435.1 at the West Valley site,

37 NRC provides technical advice and consultation in an advisory manner.

38

39 At Hanford, DOE is responsible for determining which criteria are applicable to incidental waste

40 determinations. DOE, the U.S. Environmental Protection Agency, and the State of Washington

41 Department of Ecology entered into the Hanford Federal Facility Agreement and Consent Order

42 (the Tri-Party Agreement) in 1989. Appendix H of the Tri-Party Agreement requires that DOE

43 "establish an interface with the [NRC], and reach formal agreement on the retrieval and closure

44 actions for single shell tanks with respect to allowable waste residuals in the tank and soil

45 column" for those tanks for which DOE could not remove 99 percent of the waste by volume

46 (DOE, 1989). NRC provides technical advice and consultation in an advisory manner for waste

47 determination reviews performed for the Hanford site, as requested.

48

xxii
1 References

2

3 Citizens Advisory Board, Savannah River Site (CAB). "Comments on NRC Standard Review

4 Plan Scope." Letter from J. Subc and R. Meisenheimer to A. Bradford, NRC. November 2005.

5

6 Greeves, J. and J. Lieberman. "Comments on U.S. Nuclear Regulatory Commission Draft

7 Interim Concentration Averaging Guidance." E-mail from J. Greeves and J. Lieberman to

8 M. Lesar, NRC. April 2006.

9

10 South Carolina Department of Health and Environmental Control (SCDHEC). "Comments from

11 the South Carolina Department of Health and Environmental Control on the Nuclear Regulatory

12 Commission Scoping of the Standard Review Plan for Waste Determination Reviews." E-mail

13 from S. Sherritt to A. Bradford, NRC. November 2005.

14

15 Idaho Department of Environmental Quality (Idaho). "State of Idaho Comments on the Draft

16 Interim Concentration Averaging Guidance for Waste Determinations." E-mail from B. Olenick

17 to A. Bradford, NRC. January 2006.

18

19 Natural Resources Defense Council (NRDC). "Comments of the Natural Resources Defense

20 Council on the Nuclear Regulatory Commission's Draft Interim Concentration Averaging

21 Guidance for Waste Determinations." E-mail from G. Fettus and M. McKinzie to A. Bradford,

22 NRC. January 2006.

23

24 Oregon Department of Energy (Oregon). "Docket Number PROJO734, PROJO735, PROJ0736,

25 and POOM-32." Letter from K. Niles to A. Bradford, NRC. January 2006.

26

27 U.S. Atomic Energy Commission (AEC). "Siting of Commercial Fuel Reprocessing Plants and

28 Related Waste Management Facilities." Federal Register, 34 FR 8712. June 1969.

29

30 U.S. Department of Energy (DOE). "Hanford Federal Facility Agreement and Consent Order."

31 May 1989.

32

33 DOE Order 435.1, "Radioactive Waste Management." DOE 0 435. August 2001a.

34

35 DOE Order 435.1, "Radioactive Waste Management Manual." DOE M 435.1-1.

36 June 2001b.

37

38 U.S. Nuclear Regulatory Commission (NRC). "Definition of High-Level Radioactive Waste,

39 Advanced Notice of Proposed Rulemaking." Federal Register, 52 FR 5992. February 1987.

40

41 "Disposal of Radioactive Wastes, Final Rule." Federal Register, 54 FR 22578.

42 May 1989.

43

44 . "Reasonable Assurance: [Disposal of High Level Radioactive wastes in a Proposed

45 Geologic repository at Yucca Mountain, Nevada; Final rule." Federal Register, 66 FR 55740.

46 November, 2001.

47

48 . "Denial of Petition for Rulemaking: States of Washington and Oregon." Federal

49 Register, 58 FR 12342. March 1993.

xxiii
1 . "Classification of Hanford Low-Activity Tank Waste Fraction as Incidental." Letter from

2 C. Paperiello to J. Kinzer, DOE. June 1997a.

3

4 . "Classification of Hanford Low-Activity Tank Waste Fraction as Incidental."

5 SECY-97-083. April 1997b.

6

7 . "Classification of Savannah River Residual Tank Waste as Incidental." SECY-99-284.

8 December 1999.

9

10 "Savannah River Site High-Level Waste Tank Closure: Classification of Residual

11 Waste as Incidental." Letter from W. Kane to R.J. Schepens, DOE. June 2000a.

12

13 . "Staff Requirements-SECY-99-0284-Classification of Savannah River Residual

14 Tank Waste as Incidental." SRM-SECY-99-0284. May 2000b.

15

16 . "NRC Review of Idaho National Engineering and Environmental Laboratory Draft Waste

17 Incidental to Reprocessing Determination for Sodium-Bearing Waste - Conclusions and

18 Recommendations." Letter from J. Greeves to J. Case, DOE. August 2002a.

19

20 . "Final Policy Statement for the Decommissioning Criteria for the West Valley

21 Demonstration Project at the West Valley Site." Federal Register, 67 FR 5003. February

22 2002b.

23

24 . "NRC Review of Idaho National Engineering and Environmental Laboratory Draft

25 Incidental Waste (Waste Incidental to Reprocessing) Determination for Sodium-Bearing Waste."

26 SECY-02-0112. June 2002c.

27

28 . "NRC Review of Idaho Nuclear Technology and Engineering Center Draft Waste

29 Incidental to Reprocessing Determination for Tank Farm Facility Residuals-Conclusions and

30 Recommendations." Letter from L. Kokajko to J. Case, DOE. June 2003a.

31

32 . "NRC Review of Idaho National Engineering and Environmental Laboratory Draft

33 Incidental Waste (Waste-Incidental-to-Reprocessing) Determination for Tank Farm Facility

34 Closure." SECY-03-0079. May 2003b.

35

36 Letter from N. Diaz, NRC Chairman, to Senator J. Inhofe. May 2004a.

37

38 Letter from N. Diaz, NRC Chairman, to Senator Jeffords. July 2004b.

39

40 . "Notice of Public Scoping Meeting and Solicitation of Scoping Comments Related to the

41 Standard Review Plan for Waste Determination Reviews." Federal Register, 70 FR 66472.

42 November 2005a.

43

44 "Waste Determination Standard Review Plan Public Meeting." November 2005b.

45

46 "Draft Interim Concentration Averaging Guidance for Waste Determinations." Federal

47 Register, 70 FR 74846. December 2005c.

48

xxiv
1 . "Implementation of New U.S. Nuclear Regulatory Commission Responsibilities Under

2 the National Defense Authorization Act of 2005 in Reviewing Waste Determinations for the

3 U.S. Department of Energy." SECY-05-0073. April 2005d.

4

5 . "Staff Requirements-SECY-05-0073-1mplementation of New U.S. Nuclear

6 Regulatory Commission Responsibilities Under the National Defense Authorization Act of 2005

7 in Reviewing Waste Determinations for the USDOE." SRM-SECY-05-0073. June 2005e.

8

9 Washington State Department of Ecology (Washington). "Comments on the USNRC Standard

10 Review Plan." Email from S. Dahl to A. Bradford, NRC. November 2005.

11

12 . "Washington Department of Ecology Comments on Docket Numbers PROJ0734,

13 PROJ0735, PROJ0736, POOM-32." Letter from S. Dahl to A. Bradford, NRC. February 2006.

14

15 Washington Closure Hanford (WCH). "Draft Interim Concentration Averaging Guidance for

16 Waste Determinations." Letter from P. Pettiette to A. Bradford, NRC. February 2006.

xxv

1 1 SITE-SPECIFIC AND GENERAL INFORMATION

2

3 1.1 Site-Specific System Description Information

4

5 This section of the guidance document describes information about a site, disposal facilities,1

6 and waste management activities that a reviewer should evaluate at the beginning of a waste

7 determination review. A reviewer should establish the proper context for the detailed technical

8 review that should be performed according to the guidance provided in Sections 2-8 of this

9 document. To accomplish this objective, the reviewer must understand how the proposed

10 waste management activities, disposal facility design, natural site characteristics, performance

11 assessment analyses, and inadvertent intruder analyses are used to support decisions based

12 on the waste determination. If practical, the reviewer should visit the site during the review.

13 The site visit should provide the reviewer with an opportunity to see many of the site features

14 and is expected to facilitate the review of information related to the waste determination.

15

16 1.1.1 Brief Description and Scope

17

18 First, the reviewer should assess the decisions to be made based on the waste determination

19 and identify the technical bases for those decisions. Thus, the reviewer should evaluate the

20 purpose and scope of the proposed waste management activities, the U.S. Department of

21 Energy's (DOE's) understanding of the applicable waste criteria for the waste determination

22 (see Section 2), and how the proposed waste management activities meet the applicable

23 criteria. Based on previous waste determinations, NRC anticipates that DOE may provide this

24 information in one or more summary documents (e.g., as in DOE, 2005a-c; Rosenberger, et al.,

25 2005; Buice, et al., 2005). Specifically, before beginning a detailed technical review, the

26 reviewer should be familiar with the following information:

27

28 - A brief description of the disposal site and surrounding areas, including the size of the

29 disposal facility and the location of the disposal facility on the larger DOE site;

30

31 9 DOE's definition of the scope of the waste determination, including an identification of

32 the waste streams to which decisions based on the waste determination will apply;

33

34 • A description of the purpose of the proposed waste management activities;

35

36 * A description of the major structures, systems, and components of the proposed

37 disposal facilities;

38

39 - The proposed schedule for relevant waste management activities;

1

As described in 10 CFR 61.2, the term "land disposal facility" means the land, building, structures, and equipment

that are intended to be used for the disposal of radioactive wastes. The term "disposal site" refers to the portion of

the land disposal facility that is used for disposal of waste. In this guidance document, unless otherwise specified,

the scope of the terms "site" and "facility" is limited to those locations and structures immediately related to the DOE

waste determination under review, and the features that could affect the performance of the proposed disposal facility

(e.g., aquifers, rivers). Unless otherwise noted, the term "site" is not intended to apply to the much larger area under

DOE control and ownership, such as the Savannah River Site or Idaho National Laboratory, except to the extent that

features of the larger DOE site may affect the performance of the proposed disposal facility. In this guidance, the

term "DOE site" refers to the entire area under DOE control.

1-1
1 * Which criteria are applicable to the waste determination (see Section 2); and

2

3 * An assessment of compliance with the applicable waste criteria, including the following:

4

5 -A list of the radionuclides considered to be highly radioactive radionuclides in the

6 context of the waste determination and a summary of the basis for their selection

7 (see Sections 2.4.2 and 3.2);

8

9 -A summary of waste removal activities, including inventories of radionuclides before

10 and after removal (see Section 3);

11

12 -The waste classification assumed by DOE, if applicable (see Section 3.5);

13

14 -A summary of results of the performance assessment and inadvertent intruder

15 analyses used to demonstrate compliance with the applicable performance

16 objectives (see Sections 4 and 5);

17

18 -The major features of the proposed activities that will ensure the safety of

19 individuals during operations (see Section 6);

20

21 - A summary of the pathways and radionuclides that dominate predicted doses to

22 members of the public and workers during operations and to members of the public

23 (including inadvertent intruders) after site closure (see Sections 4, 5, and 6);

24

25 - A summary of natural and engineered features of the disposal site that

26 significantly limit or prevent potential doses to individuals after site closure (see

27 Section 4.6.1.1); and

28

29 - The major features of the natural system and relevant waste disposal facilities that

30 could either affect or ensure disposal site stability (see Section 7).

31

32 1.1.2 Facility Description

33

34 The reviewer should evaluate the facility description to understand the role of the disposal

35 facility in the performance assessment, inadvertent intruder analysis, demonstration of the

36 protection of individuals during operations, and demonstration of disposal site stability. In

37 general, the areas of review are expected to encompass, but not necessarily be limited to, the

38 technical information described in 10 CFR 61.12(b), (c), (d), (g), and (i). Specifically, the

39 reviewer should evaluate the following information:

40

41 * A scale drawing or map of the relevant disposal unit(s) showing locations of

42 radioactivity within the disposal unit(s), including a description of structures

43 (e.g., equipment, tanks, pumps, piping, or disposal vaults) at the facility that are the

44 subject of the waste determination;

45

46 * A system description, including the geometry of structures (e.g., tanks, contaminated

47 equipment, or waste treatment facilities) and barriers (e.g., caps or vaults) that may be

48 important in developing conceptual models to assess the performance of the facility;

49

1-2
1 * A description of the major design features of the disposal facility and disposal units and

2 the relationship between the design features and performance objectives, including

3 the following:

4

5 - A 'description of design features related to the infiltration of water, integrity of covers

6 for disposal units, and disposal site drainage;

7

8 - A description of the design features related to disposal site closure including

9 features designed to limit the need for long-term maintenance and to limit the

10 potential for inadvertent intrusion;

11

12 - A description of design features related to disposal site stabilization, including the

13 structural stability of backfill, wastes, and covers;

14

15 - A description of the relationship between natural events and processes (see

16 Section 1.1.3) and the principal facility design criteria;

17

18 - A description of the physical and chemical forms of the radionuclides;

19

20 * Information about past waste management activities (e.g., addition of chelating agents,

21 waste treatment processes) to the extent that they may affect contaminant fate and

22 transport modeling or affect monitoring activities; and

23

24 - Information about previous waste releases that is relevant to potential release pathways

25 or to contamination that may affect proposed waste management activities.

26

27 In some instances, existing facilities, and especially older facilities, may not be adequately

28 described. If the information provided is incomplete, the reviewer should determine what

29 conservative assumptions are necessary to assess long-term facility performance.

30

31 1.1.3 Site Description

32

33 The reviewer should evaluate the natural and anthropogenic characteristics of the proposed

34 disposal site that may affect its ability to meet the performance objectives of 10 CFR Part 61,

35 Subpart C. It is expected that the reviewer will need the information described in this section to

36 evaluate conceptual models supporting a performance assessment (e.g., hydrologic

37 characteristics influencing radionuclide transport), inadvertent intruder analysis (e.g., the

38 presence of natural resources that could influence methods of inadvertent intrusion), evaluation

39 of doses to individuals during operations (e.g., the location of members of the public during

40 operations), and evaluation of site stability (e.g., the nature of meteorological, hydrologic, and

41 seismic disruptive events). It is anticipated that (1) the effect of individual natural and

42 anthropogenic features on waste isolation will be different at different disposal sites and (2) the

43 level of description provided may vary accordingly. In general, the areas of review are expected

44 to encompass, but not necessarily be limited to, the technical information described in

45 10 CFR 61.12(a), (d), and (h). Additional guidance on reviewing these types of information is

46 provided in other documents (see NRC, 2003a, 2000, 1988, 1982, 1981).

47

1-3
1 1.1.3.1 Site Location and Description

2

3 The reviewer should evaluate information related to the site location to understand the

4 relationship between the disposal site and regional features and to establish potential receptor

5 locations during operations and after site closure. To the extent possible, the reviewer should

6 verify the information with independent reports [e.g., U.S. Geological Survey (USGS) maps, site

7 maps, previous waste determinations, site planning documents]. Specifically, the reviewer

8 should evaluate the following information:

9

10 - A scale drawing or map of the waste disposal system and related existing or proposed

11 structures, showing sizes and locations on the DOE site;

12

13 - A scale drawing or map showing the location of the disposal site relative to prominent

14 natural features such as rivers and lakes;

15

16 - A map that shows the topography (including elevations) of the site;

17

18 - A description of the manmade features of the site that may affect the waste isolation

19 characteristics of the disposal site, such as parking lots or roads that may affect runoff

20 and recharge;

21

22 - A description of neighboring property surrounding the DOE site;

23

24 - A description of biological characteristics of the area that may influence waste isolation

25 (e.g., a description of any plants native to the region that could compromise closure caps

26 through root intrusion or the presence of burrowing animals that could compromise

27 closure caps or exhume waste); and

28

29 A scale drawing or map that shows the location of members of the public before and

30 after site closure and before and after the period of institutional controls ends, including

31 the location of inadvertent intruders after the period of institutional controls ends.

32

33 1.1.3.2 Land Use

34

35 The reviewer should evaluate past, current, and potential future land use around the site to

36 provide context for assumptions about the activities of members of the public (including

37 potential inadvertent intruders) after site closure and activities of members of the public during

38 operations. The reviewer should verify that DOE has used appropriate available data on land

39 use to support its performance assessment and inadvertent intruder analyses. Specifically, the

40 reviewer should perform the following review procedures:

41

42 - The reviewer should evaluate land uses prior to Federal control of the site and determine

43 whether any changes to the site have been made that would preclude the resumption of

44 similar activities (e.g., depletion of an aquifer).

45

46 The reviewer should assess the current uses of land neighboring the DOE site and the

47 impact these uses -may have on future use of the disposal site after the end of

48 institutional controls (e.g., the growth of a major metropolitan area neighboring the DOE

49 site could limit agricultural uses of the disposal site).

1-4
1 0 The reviewer should assess the current uses of land neighboring the DOE site and any

2 impact the current land uses may have on assumptions about the location of members

3 of the public during operations.

4

5 The reviewer should evaluate a description of ground and surface waters on or near the

6 site including information on resource type, occurrence, location, current projected uses,

7 and potential future uses (e.g., agricultural, industrial, drinking water source).

8

9 The reviewer should evaluate a description of the natural resources occurring at or near

10 the site (e.g., metallic and nonmetallic ores, fossil fuels and hydrocarbons, and mineral

11 deposits) and assess whether the exploitation of natural resources at the site could

12 affect future development of land surrounding the disposal site.

13

14 The reviewer should evaluate a description of these natural resources occurring at or

15 near the site and assess whether the exploitation of the resources could affect the

16 likelihood or potential methods of inadvertent intrusion into the disposal site.

17

18 1.1.3.3 Meteorology and Climatology

19

20 The reviewer should evaluate a description of the meteorology and climatology in the vicinity of

21 the site to determine how local weather patterns could affect the site's ability to meet the

22 performance objectives in 10 CFR Part 61, Subpart C. Thus, the reviewer should examine

23 meteorological information necessary to support estimates of infiltration, airborne dose pathway

24 analyses, and potential disruption of engineered barriers by processes such as flooding,

25 erosion, and frost heaving. Because of the long timeframes to be considered, the reviewer also

26 should verify whether DOE has provided a description of its projections of future climate

27 changes and appropriately incorporated these projections into the performance assessment.

28 Specifically, the reviewer should verify that DOE provided the following information:

29

30 - A description of the general climate of the region;

31

32 - A description of aspects of the local (site) meteorology that may affect performance

33 assessment and dose calculations (e.g., temperature, precipitation intensity and

34 duration, wind speed, wind direction, and atmospheric stability);

35

36 - A description of the projected future climate states to be considered in the performance

37 assessments, including the basis for and uncertainties in those projections; and

38

39 - A description of the sensitivity of system performance to uncertainty in future

40 climate states.

41

42 To the extent possible, the reviewer should verify site-specific information about meteorology

43 and climatology against independent information (e.g., information provided by the National

44 Weather Service or the National Oceanic and Atmospheric Administration). Projected future

45 climate states should be supported by an adequate technical basis and compared to

46 independent assessments (e.g., paleoclimate modeling performed by the National Climatic Data

47 Center) to the extent possible. Because capabilities to predict climate change continue to

48 evolve, additional information about climate change may be relevant if system performance is

49 sensitive to uncertainties in future climate states.

1-5
1 1.1.3.4 Geology and Seismology

2

3 Information about geologic processes (e.g., earthquakes, erosion, faulting) that occur at the site

4 is needed to support an assessment of site stability and to support the development of

5 conceptual models used in the performance assessment and inadvertent intruder analysis. To

6 support an assessment of how the geological and geotechnical characteristics of a site will

7 affect its performance, the reviewer should evaluate the following information:

8

9 - A description of the surface and subsurface geologic characteristics and stratigraphy of

10 the site and its vicinity;

11

12 - A description of the geomorphology of the site, including USGS topographic maps that

13 emphasize local geomorphic features pertinent to the site, particularly for processes

14 such as erosion that may affect long-term site stability;

15

16 - A description of past seismic and volcanic activity at and near the site, the features and

17 processes that caused the activity, and the potential for significant seismic and volcanic

18 activity to occur in the future;

19

20 - A description of the potential effects of seismic activity on site performance, including the

21 effects of landslides, land movement, and liquefaction;

22

23 - A description of manmade geologic features, such as mines or quarries, that may affect

24 water runoff and recharge; and

25

26 - A description of the structural stability of geotechnical features of the disposal

27 facility (e.g., slope stability, potential for subsidence of backfilled soils that could affect

28 cap stability).

29

30 To the extent possible, the reviewer should verify descriptions of the site-specific geological and

31 seismological information with independent information, such as maps and other geospatial

32 USGS-generated data.

33

34 1.1.3.5 Hydrology

35

36 The reviewer should use information about the surface water and groundwater hydrology to

37 evaluate conceptual models of how the hydrologic characteristics at the site will affect site

38 stability and radionuclide release and transport. Depending on the specific site, the reviewer

39 may need to analyze the potential impact of atypical hydrological conditions (e.g., floods).

40 Specifically, the reviewer should evaluate the following information:

41

42 A description of natural drainage and surrounding watershed fluvial features and

43 anthropogenic features that may influence surface hydrology and the potential for

44 flooding at the site;

45

46 Water resource data, including maps, hydrographs, and stream records from other

47 agencies (e.g., USGS and U.S. Army Corps of Engineers);

48

1-6
1 A description of the surface water bodies at the site and surrounding areas, including

2 the location, size, shape, and other hydrologic characteristics of streams, lakes, or

3 coastal areas;

4

5 o A description of the saturated zone, including potentially affected aquifers, the lateral

6 extent, thickness, water-transmitting properties, recharge and discharge zones,

7 groundwater flow directions and velocities, and other information that can be used to

8 support the conceptual model of the saturated zone;

9

10 * Physical parameters, such as storage coefficients, transmissivities, hydraulic

11 conductivities, porosities, and intrinsic permeabilities;

12

13 - A description of the unsaturated zone, including descriptions of the lateral extent and

14 thickness of permeable and impermeable zones; the presence, lateral extent, and

15 thickness of perched water zones; potential conduits of anomalously high flux; and

16 direction and velocity of unsaturated flow;

17

18 Physical parameters, such as porosity, water content (including temporal variation);

19 saturated hydraulic conductivity; characteristic relationships between water content,

20 pressure head, and hydraulic conductivity; and hysteretic behavior during wetting and

21 drying cycles; and

22

23 The distribution coefficients (Kd) of the radionuclides of interest and the associated

24 technical basis for their selection (e.g., site-specific values, literature compilations,

25 geochemical models).

26

27 1.1.3.6 Radiological Status

28

29 Because the DOE sites relevant to this guidance document (Savannah River Site, Idaho

30 National Laboratory, Hanford, and West Valley) have operated for decades, areas near the

31 proposed disposal facility may already be contaminated with radioactive material. In general,

32 contamination resulting from spills or other releases of radioactive material at the site is

33 addressed through alternate regulatory processes and is not within the scope of waste

34 determinations. However, existing radioactive contamination may affect or provide useful

35 information about the waste management activities proposed in a waste determination.

36 Specifically, the reviewer should evaluate information about groundwater contamination that

37 may provide relevant information about radionuclide release pathways, may constrain

38 contaminant fate and transport models, or that may complicate subsequent monitoring activities.

39 Therefore, a reviewer should evaluate information about the current radiological status of the

40 area near the proposed disposal facility and its environs, including the following information:

41

42 - A summary of areas near the proposed disposal facilities where releases of radioactive

43 material occurred in the past;

44

45 - A description of the types, forms, activities, and concentrations of radionuclides involved

46 in the release; and

47

1-7
1

2

3

4

5

6

7

8

9

10

11

12

13

A scale drawing or map of the site, facilities, and environs showing the locations of

relevant previous releases, including features such as abandoned boreholes or

disturbed soil that may affect contaminant fate and transport.

To ensure information describing the area near the proposed disposal facility is complete, the

reviewer should evaluate the purpose, major attributes, summary conclusions, and regulatory

program under which studies of existing contamination near the disposal facility were evaluated.

If significant groundwater contamination exists, the reviewer should evaluate historical

information about plume movement for comparison with the results of site-specific groundwater

models used to support the performance assessment (see Section 4) and DOE's plans to

monitor and model plume movement for coordination with NRC monitoring activities (see

Section 10).

14

15

16

17.

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

.44

45

46

47

48

49

1.2 Applicable Sites and Waste Criteria

This guidance document has been developed to address the reviews of waste determinations

for the four DOE sites that may have incidental waste:

* Savannah River Site (SRS), Aiken, South Carolina;

* Idaho National Laboratory (INL), Idaho Falls, Idaho;

* Hanford Site (Hanford), Richland, Washington; and

* West Valley Demonstration Project (West Valley), West Valley, New York.

The reviewer must determine whether DOE is using the applicable waste criteria for'a given

waste determination. The different sets of waste criteria are detailed in Section 2 of this

guidance document. Guidance for the detailed technical evaluation of whether there is

reasonable assurance that the applicable waste criteria can be met is provided in Sections 2-8

of this guidance document.

Based on previous waste determinations, it is anticipated that DOE will provide information that

addresses each of the waste criteria it considers to be applicable to a specific waste

determination. The staff should review the DOE waste determination to verify that the

applicable waste criteria have been addressed. For example, the staff should confirm whether

DOE has identified the following criteria for specific sites:

* The Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 (NDAA)

(Public Law 108-375, 2004) is applicable to certain waste disposed of in South Carolina

or Idaho subject to other requirements of the NDAA (see Section 2.1);

* The waste incidental to reprocessing criteria from DOE Order 435.1 and its associated

Manual (DOE, 2001a,b) may apply to waste in South Carolina or Idaho that is not

covered by the NDAA, waste at Hanford, or waste being shipped offsite from the West

Valley Demonstration Project (see Section 2.2); and

* The waste incidental to reprocessing criteria identified in the Decommissioning Criteria

for the West Valley Demonstration Project at the West Valley Site; Final Policy

1-8
1 Statement (NRC, 2002) are applicable to waste being disposed of on site at the West

2 Valley site (see Section 2.3).

3

4 1.3 Prior Waste Determinations

5

6 The reviewer should consider prior waste determination reviews for relevance to the

7 technical evaluation at hand and determine how the reviews might support an assessment of

8 the DOE demonstration of compliance with appropriate waste criteria. For example, the

9 reviewer could examine NRC's Technical Evaluation Reports (TERs) for tank closure at INL

10 (NRC, 2003b) and for salt waste disposal at SRS (NRC, 2005). As additional waste

11 determination reviews are completed, additional documents can be considered for each of the

12 four DOE sites previously noted.

13

14 To the extent practical, the staff should evaluate prior TERs both to gain insights from previous

15 NRC conclusions and recommendations and to understand any major changes from prior

16 analyses. Staff should particularly focus on the extent to which the prior reviews provide

17 insights into the current DOE waste determination with regard to information such as, but not

18 limited to, the following:

19

20 - Site characterization;

21

22 • Waste inventory and source term;

23

24 - Locations, descriptions, operating history, and radiological status of any facilities

25 associated with the proposed waste management activities;

26

27 * Existing and proposed waste management strategies and methodologies;

28

29 - Existing and proposed performance assessment and dose modeling methodologies

30 and results;

31

32 * Existing and proposed monitoring systems; and

33

34 - Related structures and processes DOE employed in previous waste

35 management strategies.

36

37 This evaluation may include prior waste determination reviews identified by either DOE or the

38 reviewer. To the extent practical, the reviewer should consider prior waste determinations from

39 both the site being currently evaluated and other DOE sites, if relevant.

40

41 1.4 References

42

43 Buice, J.M., R.K. Cauthen, R.R. Haddock, B.A., Martin, J.A. McNeil, J.L. Newman, and

44 K.H. Rosenberger. "Performance Objective Demonstration Document (PODD) for the Closure

45 of Tank 19 and Tank 18 Savannah River Site." CBU-PIT-2005-00106. Rev. 1. Westinghouse

46 Savannah River Company. 2005.

47

1-9
1 _ Public Law 108-375, "Ronald W. Reagan National Defense Authorization Act for Fiscal Year

2 2005." October 2004.

3

4 U.S. Department of Energy (DOE). "Radioactive Waste Management." DOE 0 435.1.

5 August 2001a.

6

7 "Radioactive Waste Management Manual." DOE M 435.1-1. June 2001b.

8

9 "Draft Section 3116 Determination Salt Waste Disposal Savannah River Site."

10 DOE-WD-2005-001. DOE-Savannah River. March 2005a.

11

12 . "Draft Section 3116 Determination Idaho Nuclear Technology and Engineering Center

13 Tank Farm Facility." DOE/NE-ID-11226. DOE, Idaho Operations Office. 2005b.

14

15 . "Draft Section 3116 Determination for Closure of Tank 19 and Tank 18 at the Savannah

16 River Site." DOE-WD-2005-002. DOE-Savannah River. September 2005c.

17

18 U.S. Nuclear Regulatory Commission (NRC). "Draft Environmental Impact Statement on

19 10 CFR Part 61 Licensing Requirements for Land Disposal of Radioactive Waste."

20 NUREG-0782. Washington, DC. September 1981.

21

22 . "Site Suitability, Selection, and Characterization, Branch Technical Position-Low-Level

23 Waste Licensing Branch." NUREG-0902. April 1982.

24

25 . "Standard Review Plan for the Review of a License Application for a Low-Level

26 Radioactive Waste Disposal Facility." NUREG-1200. January 1988.

27

28 . "A Performance Assessment Methodology for Low-Level Radioactive Waste Disposal

29 Facilities: Recommendations of NRC's Performance Assessment Working Group."

30 NUREG-1573. October 2000.

31

32 . "Decommissioning Criteria for the West Valley Demonstration Project (M-32) at the

33 West Valley Site; Final Policy Statement." Federal Register. Vol. 67, No. 22. February 2002.

34

35 . "Consolidated NMSS Decommissioning Guidance." Vols. 1-3. NUREG-1757.

36 September 2003a.

37

38 . "NRC Review of Idaho Nuclear Technology and Engineering Center Draft Waste

39 Incidental to Reprocessing Determination for Tank Farm Facility Residuals-Conclusions and

40 Recommendations." Letter from L. Kokajko to J. Case, DOE. June 2003b.

41

42 . "Technical Evaluation Report for the U.S. Department of Energy, Savannah River Site

43 Draft Section 3116 Waste Determination for Salt Waste Disposal." Letter from L. Camper to

44 C. Anderson, DOE. December 2005.

45

46 Rosenberger, K.H., B.C. Rogers, and R.K. Cauthen. "Saltstone Performance Objective

47 Demonstration Document (U)." CBU-PIT-2005-00146. Rev. 0. Westinghouse Savannah

48 River Company. 2005.

1-10
1 2 INCIDENTAL WASTE CRITERIA

2

3 This section of the guidance document discusses the criteria against which a waste

4 determination will be reviewed. This will enable U.S. Nuclear Regulatory Commission (NRC)

5 reviewers to understand the criteria and determine how to evaluate the approaches that the

6 U.S. Department of Energy (DOE) might use to show that the criteria can be met. This section

7 provides information concerning the waste criteria from Section 3116 of the Ronald W. Reagan

8 National Defense Authorization Act for Fiscal Year 2005 (NDAA) (Section 2.1), the DOE

9 Order 435.1 "Radioactive Waste Management" and the associated manual "Radioactive Waste

10 Management Manual" (Section 2.2), and the West Valley Policy Statement (Section 2.3). In

11 general, there are several similarities between the different sets of Criteria (e.g., all of the sets of

12 criteria refer to the performance objectives of 10 CFR Part 61, Subpart C) and a few important

13 differences (e.g., not all of the sets of criteria require that certain concentration limits be met).

14 Where appropriate, consistent guidance for reviewing similar criteria is provided. Differences in

15 criteria are discussed in Section 2.4. Sections 2.5-2.7 provide information on.reviewing certain

16 criteria, some of which is described in greater detail in Sections 3-7.

17

18 2.1 Criteria from the Ronald W. Reagan National Defense

19 Authorization Act for Fiscal Year 2005 (Section 3116)

20

21 Section 3116 of the NDAA (Public Law 108-375, 2004) (see Appendix A) identifies the following

22 criteria for determining that waste is not high-level waste (HLW):

23

24 (1) The waste does not require permanent isolation in a deep geologic

25 repository for spent nuclear fuel or HLW (see Section 2.5);

26

27 (2) The waste has had highly radioactive radionuclides removed to the

28 maximum extent practical (see Sections 2.6 and 3); and

29

30 (3)A The waste does not exceed concentration limits for Class C low-level

31 waste (LLW) and will be disposed of in compliance with the performance

32 objectives in 10 CFR Part 61, Subpart C (see Sections 2.7 and 3-7); or

33

34 (3)B The waste exceeds concentration limits for Class C LLW but will be

35 disposed of in compliance with the performance objectives in

36 10 CFR Part 61, Subpart C (see Section 4.7), and pursuant to plans DOE

37 developed in consultation with NRC (see Sections 2.7 and 3.7).

38

39 As described in paragraphs (c) and (d) of Section 3116 of the NDAA, these criteria apply to

40 certain waste that will be disposed of in South Carolina and Idaho and not to waste that will be

41 transported out of those States. The NDAA may not apply to waste that does not meet other

42 criteria in the NDAA (e.g., waste not covered by State-issued closure plans or permits).

43

44 2.2 Criteria from DOE Order 435.1

45

46 DOE Order 435.1 and the related Manual 435.1-1 (DOE, 2001a,b) consider that incidental

47 waste may be either LLW or transuranic (TRU) waste and include the following two

2-1
1 corresponding sets of similar criteria for determining that waste is incidental to reprocessing.

2 Incidental wastes that will be managed as LLW will meet the following criteria:

3

4 (1) Have been processed or will be processed to remove key radionuclides to the

5 maximum extent that is technically and economically practical (see Sections 2.6

6 and 3);

7

8 (2) Will be managed to meet safety requirements comparable to the performance

9 objectives set out in 10 CFR Part 61, Subpart C (see Sections 2.7 and 4.7); and

10

11 (3) Are to be managed, pursuant to DOE's authority under the Atomic Energy Act of

12 1954, as amended, and in accordance with the provisions of Chapter IV of the

13 DOE Radioactive Waste Management Manual (DOE, 2001 b), provided the waste

14 will be incorporated in a solid physical form at a concentration that does not

15 exceed the applicable concentration limits for Class C LLW as set out in

16 10 CFR 61.55 (see Section 3.5) or will meet alternative requirements for waste

17 classification and characterization as DOE may authorize.

18

19 Incidental wastes that will be managed as transuranic wastes will meet the following criteria:

20

21 (1) Have been processed or will be processed to remove key radionuclides to the

22 maximum extent that is technically and economically practical (see Sections 2.6

23 and 3);

24

25 (2) Will be incorporated in a solid physical form and meet alternative requirements

26 for waste classification and characteristics, as DOE may authorize; and

27

28 (3) Are managed pursuant to DOE's authority under the Atomic Energy Act of 1954,

29 as amended, in accordance with the provisions of Chapter III of the DOE

30 Radioactive Waste Management Manual (DOE, 2001 b), as appropriate.

31

32 DOE may decide to apply the requirements in DOE Order 435.1 and the associated Manual

33 (DOE, 2001a,b) to waste in South Carolina or Idaho that is not covered by the NDAA, waste at

34 Hanford, or waste being shipped offsite from West Valley.

35

36 The wording in DOE M 435.1-1 does not require that DOE necessarily use the waste

37 classifications in 10 CFR 61.55 or the performance objectives in 10 CFR Part 61, and DOE has

38 the flexibility to use criteria that are different (DOE, 2001b). NRC does not have a regulatory or

39 statutory role with regard to whether the alternate criteria DOE proposed in a waste

40 determination in accordance with DOE 435.1 are acceptable. Because the alternate criteria that

41 DOE may propose cannot be known at this time, specific associated guidance cannot be

42 provided in this guidance document; however, the general approach and review areas identified

43 in the guidance document will still provide useful insights to the reviewer. In general, the NRC

44 staff review should assess whether there is reasonable assurance that the proposed alternate

45 criteria can be met and may provide an independent risk-informed, performance-based

46 assessment of whether the criteria can protect public health and safety.

47

48 In February 2002, the Natural Resources Defense Council (NRDC), Snake River Alliance, and

49 the Yakama and Shoshone-Bannock Nations filed suit against the DOE, stating that the Nuclear

2-2
1 Waste Policy Act did not allow DOE to reclassify HLW and dispose of it anywhere except in a

2 geologic repository. In July 2003, the Federal District Court in Idaho granted summary

3 judgment to NRDC and declared DOE's incidental waste process, as described in DOE

4 Order 435.1, invalid. DOE appealed the decision; in November 2004, the U.S. Court of Appeals

5 for the Ninth Circuit vacated the lower court's decision on ripeness grounds.

6

7 2.3 Criteria from the West Valley Policy Statement

8

9 The NRC's "Decommissioning Criteria for the West Valley Demonstration Project at the West

10 Valley Site; Final Policy Statement" (West Valley Policy Statement) identifies the following

11 criteria for incidental waste determinations (NRC, 2002):

12

13 (1) The waste should be processed (or should be further processed) to remove

14 key radionuclides to the maximum extent that is technically and economically

15 practical (see Sections 2.6 and 3); and

16

17 (2) The waste should be managed so that safety requirements comparable to the

18 performance objectives in 10 CFR Part 61, Subpart C, are satisfied (see

19 Sections 2.7 and 4.7).

20

21 NRC's West Valley Policy Statement provides criteria that are applicable to waste that may be

22 disposed of onsite at West Valley.

23

24 The West Valley Policy Statement also states that "the resulting calculated dose from incidental

25 waste is to be integrated with all theother calculated doses from the material remaining at the

26 entire NRC-licensed site." However, this guidance document covers only the review of

27 incidental waste determinations, not the larger analysis of whether the entire site meets the

28 West Valley Policy Statement or any other applicable requirements.

29

30 2.4 Comparison of Criteria

31

32 In general, there are several similarities between the different sets of criteria (e.g., all of the sets

33 of criteria refer to the performance objectives of 10 CFR Part 61, Subpart C) and a few

34 important differences (e.g., not all of the sets of criteria require that certain concentration limits

35 be met). Where appropriate, this guidance document provides consistent guidance for

36 reviewing those criteria that are similar, as discussed below.

37

38 2.4.1 "Waste Incidental to Reprocessing" and "Non-High-Level Waste"

39

40 Historically, the type of waste addressed in waste determinations has been referred to as

41 "waste-incidental-to-reprocessing" (WIR) or "incidental waste," and the waste determinations

42 have been called "WIR determinations." The NDAA does not use the term "incidental waste" or

43 "WIR" but instead specifies that HLW does not include wastes that meet the criteria of the

44 NDAA; therefore, DOE refers to waste that is covered by the NDAA as "non-HLW" and the

45 associated waste determinations as "non-HLW determinations." The NRC staff considers WIR,

46 incidental waste, and non-HLW to be the same type of waste; that is, they are wastes that are

47 incidental to the reprocessing of nuclear fuel and can be managed as LLW if the appropriate

48 criteria can be met. This guidance document uses the term "incidental waste" to mean both

2-3
1 "WIR" and "non-HLW waste" and uses the term "waste determinations" to mean both "WIR

2 determinations" and "non-HLW determinations."

3

4 2.4.2 "Highly Radioactive Radionuclides" and "Key Radionuclides"

5

6 The NDAA refers to "highly radioactive radionuclides," while DOE M 435.1-1 and the West

7 Valley Policy Statement both refer to "key radionuclides." The NRC staff has previously stated

8 that it believes that "highly radioactive radionuclides" are those radionuclides that contribute

9 most significantly to risk to the public, workers, and the environment (NRC, 2005). This is the

10 same concept as key radionuclides, as used in previous NRC reviews of waste determinations

11 (NRC, 2003). Therefore, for purposes of evaluating waste determinations, the NRC staff

12 considers key radionuclides and highly radioactive radionuclides to be equivalent. For ease of

13 reference, this guidance document uses the term "highly radioactive radionuclides" to also

14 mean "key radionuclides." See Section 3.2 for guidance on evaluating the identification of

15 highly radioactive radionuclides.

16

17 2.4.3 "Maximum Extent Practical" and "Maximum Extent Technically and

18 Economically Practical"

19

20 The NDAA refers to removal of radionuclides to the "maximum extent practical," while

21 DOE M 435.1-1 and the West Valley Policy Statement both refer to "the maximum extent

22 technically and economically practical." The "maximum extent practical" is similar to the

23 "maximum extent technically and economically practical," but allows for somewhat broader

24 considerations of what is practical (e.g., DOE's schedule, programmatic considerations, other

25 risk considerations such as non-radiological risk). However, in most cases, those broader

26 considerations should be evaluated in a quantitative manner; for example, schedule delays

27 could be quantified by estimating the monetary cost or the risk of delaying waste processing.

28 NRC staff believes that DOE should consider both technological and economic aspects of

29 waste removal in demonstrating compliance with the maximum extent practical criterion. For

30 ease of reference, this guidance document will use the term "maximum extent practical" to also

31 mean "maximum extent technically and economically practical." See Section 3 for guidance on

32 evaluating the removal to the maximum extent practical.

33

34 NRC staff believes that the purpose of the various criteria related to radionuclide removal is to

35 minimize the inventory of highly radioactive radionuclides disposed of as incidental waste. In

36 many cases, the intent of requiring removal of highly radioactive radionuclides to the maximum

37 extent practical can be satisfied by reducing the volume of residual waste in a contaminated

38 structure (e.g., a tank, an evaporator) to the maximum extent practical. However, evaluating

39 alternative methods of physically removing waste from a structure does not eliminate the need

40 to consider (1) whether it would be practical to remove selected highly radioactive radionuclides

41 from the waste (e.g., by chemical extraction) or (2) whether it would be practical to remove the

42 contaminated structure for disposal instead of stabilizing it and disposing of it in place. In this

43 guidance, "removal" of radionuclides refers to removal of waste from a disposal system (either

44 by removing waste alone or by removing contaminated structures that contain waste) or

45 removal of radionuclides from a waste stream (e.g. treatment of salt waste at SRS to remove

46 highly radioactive radionuclides prior to disposing of the waste), as applicable.

47

2-4
1 2.4.4 Differences in Concentration Limits

2

3 The NDAA specifies that if the waste being evaluated exceeds the concentration limits for Class

4 C waste, as given in 10 CFR 61.55, DOE must consult with NRC on the development of its

5 disposal plans for that waste. Although additional consultation is required, the NDAA does

6 not prohibit waste that exceeds Class C concentration limits from being determined to be

7 incidental waste. Although the NDAA does not specify that the waste must be in solid form, as

8 DOE M 435.1-1 does, NRC generally requires that waste be disposed of in solid form to provide

9 stability (10 CFR 61.56), and the staff believes this is appropriate for waste that is evaluated in

10 compliance with 10 CFR Part 61 stability requirements or comparable requirements.

11

12 DOE M 435.1-1 specifies that the waste must be in solid form at a concentration that does not

13 exceed the applicable concentration limits for Class C LLW as set out in 10 CFR 61.55 or that

14 the waste will meet alternative requirements for waste classification and characterization as

15 DOE may authorize. Therefore, DOE M 435.1-1 does prohibit waste that exceeds Class C

16 concentration limits from being determined to be incidental waste unless DOE authorizes

17 alternate criteria. See Section 3.5 for guidance on reviewing the evaluation of the class of the

18 waste. Because any alternate criteria that DOE may propose cannot be known at this time,

19 specific associated guidance cannot be provided in this guidance document; however, the

20 general approach and review areas identified in the guidance will still provide useful insights to

21 the reviewer. If DOE does authorize alternate criteria and NRC is reviewing the associated

22 waste determination, the reviewer should evaluate whether there is reasonable assurance that

23 the alternate criteria can be met and whether the proposed alternate criteria are protective of

24 public health and safety.

25

26 Although the West Valley Policy Statement does not include a concentration limit criterion with

27 respect to determining whether waste is incidental, it does provide that the waste should be

28 managed so that safety requirements comparable to the performance objectives in 10 CFR Part

29 61, Subpart C, are satisfied.

30

31 2.4.5 Alternatives to the Performance Objectives of 10 CFR Part 61,

32 Subpart C

33

34 The NDAA specifies that the "waste ... will be disposed of in compliance with the performance

35 objectives in 10 CFR Part 61, Subpart C." DOE M 435.1-1 and the West Valley Policy

36 Statement require that the "waste should be managed so that safety requirements comparable

37 to the performance objectives in 10 CFR Part 61, Subpart C, are satisfied." In other words, the

38 NDAA does not allow for safety requirements that are "comparable" to 10 CFR Part 61,

39 Subpart C, but instead specifies that only Subpart C can be used. For waste determinations

40 made using DOE Order 435.1 and the West Valley Policy Statement, DOE could propose

41 alternate safety requirements, as long as adequate technical basis is provided for determining

42 that the proposed alternate safety requirements are comparable to 10 CFR Part 61, Subpart C.

43 In general, because the requirements in Subpart C are NRC's performance objectives for the

44 disposal of waste in LLW facilities, strong justification for using alternative safety requirements

45 would be needed to demonstrate that public health and safety were protected, unless it can be

46 determined that the proposed alternate safety requirements are more stringent than those of 10

47 CFR Part 61, Subpart C. Because the proposed alternative safety requirements that DOE may

48 propose in the future cannot be known at this time, specific associated guidance cannot be

49 provided in this guidance document; however, the general approach and review areas identified

2-5
1 in the guidance will provide useful insights to the reviewer. See Sections 4-7 for guidance on

2 reviewing whether there is reasonable assurance that the performance objectives of

3 10 CFR Part 61, Subpart C, can be met.

4

5 2.5 Does Not Require Disposal in a Geologic Repository

6

7 The NDAA contains a criterion that the waste does not require permanent isolation in a deep

8 geologic repository for spent fuel or high-level radioactive waste. DOE M 435.1-1 and the West

9 Valley Policy Statement do not contain the same criterion with respect to incidental waste

10 determinations, although other statutes or regulations may require HILW disposal in a

11 geologic repository.

12

13 2.5.1 Areas of Review

14

15 In general, there is reasonable assurance that this criterion can be met if the two other NDAA

16 criteria can be met. In other words, if highly radioactive radionuclides have been removed to the

17 maximum extent practical and the waste will be disposed of in compliance with the performance

18 objectives in 10 CIFR Part 61, Subpart C (which are the same performance objectives NRC uses

19 for disposal of low-level waste), then this supports a conclusion that the waste does not require

20 disposal in a deep geologic repository. However, this criterion allows for the consideration that

21 waste may require disposal in a geologic repository even though the two other NDAA criteria

22 may be met. Those circumstances under which geologic disposal is warranted to protect public

23 health and safety and the environment could be considered; for example, unique radiological

24 characteristics of waste or nonproliferation concerns for particular types of material

25 (NRC, 2005).

26

27 2.5.2 Review Procedures

28

29 The reviewer should determine whether the following conditions are met:

30

31 * There is reasonable assurance that the other criteria of the NDAA can be met (see

32 Sections 2-8); and

33

34 * No other characteristics of the waste would necessitate that the waste be disposed of in

35 a deep geologic repository in order to protect public health and safety.

36

37 2.6 Removal of Radionuclides

38

39 Each of the sets of criteria governing waste determinations contains a requirement that certain

40 radionuclides be removed to the maximum extent practical. As discussed in Sections 2.4.2 and

41 2.4.3, there are differences between the radionuclide removal requirements of the NDAA, DOE

42 Order 435.1, and the West Valley Policy Statement. NDAA Criterion 2 requires that highly

43 radioactive radionuclides be removed to the maximum extent practical. DOE M 435.1-1 (DOE,

44 2001 b) and the West Valley Policy Statement (N.RC, 2002) require that key radionuclides be

45 removed to the maximum extent that is technically and economically practical. As discussed in

46 Section 2.4.3, NRC staff believes that NDAA wording provides more flexibility in demonstrating

47 compliance with this criterion. See Section 3 for detailed guidance on determining whether this

48 criterion has been met.

2-6
1 2.7 Compliance With Performance Objectives of 10 CFR Part 61,

2 Subpart C

3

4 As discussed in Section 2.4.5, there are differences between the NDAA, DOE M 435.1-1, and

5 the West Valley Policy Statement requirements regarding the performance objectives of

6 10 CFR Part 61. In most cases, the reviewer should evaluate compliance with the performance

7 objectives in 10 CFR Part 61, Subpart C.

8

9 10 CFR 61.40 requires that land disposal facilities be sited, designed, operated, closed, and

10 controlled after closure so that reasonable assurance exists that exposures to humans are

11 within the limits established in the performance objectives in 10 CFR 61.41-61.44. The

12 reviewer should evaluate compliance with this requirement by performing the reviews described

13 in Sections 4-7 of this guidance document.

14

15 To evaluate compliance with the performance objective for the protection of the general

16 population from releases of radioactivity (10 CFR 61.41), the reviewer should confirm that

17 concentrations of radioactive material that may be released to the general environment in

18 groundwater, surface water, air, soil, plants, or animals will not result in an annual dose to a

19 member of the public that is greater than 0.25 mSv [25 mrem] and will be maintained as low as

20 is reasonably achievable (ALARA). The reviewer should evaluate compliance with this

21 requirement as described in Section 4 of this guidance document. Note that although

22 10 CFR 61.41 requires that materials released to the general environment will not result in an

23 annual dose exceeding an equivalent of 25 millirems to the whole body, 75 millirems to the

24 thyroid, and 25 millirems to any other organ of any member of the public, the NRC staff uses an

25 exposure limit of 0.25 mSv [25 mrem] total effective dose equivalent (TEDE) in making this

26 assessment (NRC, 1999, 2005). See Section 4.6.1.3 for more detailed guidance about

27 dose calculations.

28

29 The performance objective for protection of individuals from inadvertent intrusion

30 (10 CFR 61.42) requires that the design, operation, and closure of the land disposal facility will

31 ensure protection of any individual inadvertently intruding into the disposal site and occupying

32 the site or contacting the waste at any time after active institutional controls over the disposal

33 site are removed. The performance objective does not provide numerical dose criteria for

34 protection for the inadvertent intruder. However, NRC typically applies a whole body-dose

35 equivalent limit of 5 mSv/yr [500 mrem/yr], as described in the Draft Environmental Impact

36 Statement for 10 CFR Part 61 (NRC, 1981), to assess compliance with 10 CFR 61.42. The

37 reviewer should evaluate compliance with this requirement as described in Section 5 of this

38 guidance document.

39

40 The performance objective for the protection of individuals during operations (10 CFR 61.43)

41 requires that land disposal facility operations will comply with the standards for radiation

42 protection set out in 10 CFR Part 20, except for releases of radioactivity in effluents from the

43 land disposal facility, which will be governed by 10 CFR 61.41. In addition, the performance

44 objective requires that radiation exposures during operations are maintained ALARA. The

45 information reviewed using Section 6 of this guidance document supports the evaluation of

46 compliance with this requirement.

47

48 The performance objective for stability of the disposal site after closure (10 CFR 61.44) requires

49 that a disposal facility be sited, designed, used, operated, and closed to achieve long-term

2-7
1 stability of the disposal site and to eliminate, to the extent practicable, the need for ongoing

2 active maintenance of the disposal site following closure so that only surveillance, monitoring, or

3 minor custodial care is required. Evaluation of compliance with 10 CFR 61.44 is limited to a

4 review of site stability, as described in Section 7. However, because the stability of a disposal

5 site is important to its long-term performance, the reviewer should ensure that the effects of site

6 instabilities identified in this part of the review are adequately modeled or bounded in the

7 performance assessment (see Section 4) and inadvertent intruder analysis (see Section 5).

8

9 2.8 References

10

11 Public Law 108-375, "Ronald W. Reagan National Defense Authorization Act for Fiscal Year

12 2005." October 2004.

13

14 U.S. Department of Energy (DOE), "Radioactive Waste Management." DOE 0 435.1. 2001a.

15

16 "Radioactive Waste Management Manual." DOE M 435.1-1. 2001b.

17

18 U.S. Nuclear Regulatory Commission (NRC). "Draft Environmental Impact Statement on 10

19 CFR Part 61, Licensing Requirements for Land Disposal of Radioactive Waste." NUREG-0782.

20 September 1981.

21

22 "Disposal of High-Level Radioactive Wastes in a Proposed Geological Repository at

23 Yucca Mountain, Nevada." Proposed Rule. Federal Register, 64 FR 8640. February 1999.

24

25 "Decommissioning Criteria for the West Valley Demonstration Project (M-32) at the

26 West Valley Site; Final Policy Statement." Federal Register, 67 FR 5003. February 2002.

27

28 . "NRC Review of Idaho Nuclear Technology and Engineering Center Draft Waste

29 Incidental to Reprocessing Determination for Tank Farm Facility Residuals-Conclusions and

30 Recommendations." Letter from L. Kokajko to J. Case, DOE. June 2003.

31

32 . "Technical Evaluation Report for the U.S. Department of Energy, Savannah River Site

33 Draft Section 3116 Waste Determination for Salt Waste Disposal." Letter from L. Camper to

34 C. Anderson, DOE. December 2005.

2-8
1 3 RADIONUCLIDE REMOVAL AND CONCENTRATION LIMITS

2

3 As discussed in Sections 2.4.2 and 2.4.3, each set of incidental waste criteria requires that

4 highly radioactive radionuclides be removed to the maximum extent practical. Because relevant

5 wastes may have a wide range of physical, chemical, and radiological characteristics, the list of

6 highly radioactive radionuclides is expected to vary among different waste determinations. In

7 general, NRC staff believes that highly radioactive radionuclides are those radionuclides that

8 contribute most significantly to risk to the public, workers, and the environment (NRC, 2005).

9

10 Depending on the circumstances, the removal of radionuclides may refer to the minimization of

11 the volume of residual waste remaining in place (e.g., removal of waste from a tank that is to be

12 closed) or to the removal of radionuclides from a waste stream (e.g., removal of radionuclides

13 from salt waste being disposed of as saltstone at SRS). Essentially, the common goal of the

14 various radionuclide removal criteria is to ensure that DOE minimizes inventory of highly

15 radioactive radionuclides in wastes that are classified as incidental.

16

17 To evaluate compliance with each of the radionuclide removal criteria, reviewers should

18 complete the following three steps:

19

20 * Evaluate the waste inventory, including sampling, analysis, calculations, and

21 uncertainties that may affect estimates of waste volumes and radionuclide

22 concentrations (see Section 3.1).

23

24 - Evaluate DOE's basis for selecting highly radioactive radionuclides (see Section 3.1).

25

26 * Evaluate the technical basis for determining whether radionuclides have been (or will be)

27 removed to the maximum extent practical by (1) evaluating DOE's selection of waste

28 removal technologies, (2) evaluating DOE's criteria for concluding that waste removal

29 activities should be stopped, and (3) evaluating the costs and benefits of additional

30 waste removal (see Sections 3.3 and 3.4).

31

32 This section provides review areas and procedures for each of these steps. In addition to the

33 radionuclide removal criterion specific to the evaluation of incidental waste at the West Valley

34 site, other radionuclide removal activities (e.g., removal of contaminated buildings) may be

35 subject to separate analyses to support NRC license modification or termination for the site as a

36 whole. Such site-wide analyses are not addressed in this guidance.

37

38 As discussed in Section 2.4.4, the NDAA and DOE M 435.1-1 require that wastes be classified

39 as a function of radionuclide concentrations; the NDAA requires classification according to the

40 concentration limits described in 10 CFR 61.55, while DOE Order 435.1 allows classification

41 either by the concentration limits described in 10 CFR 61.55 or by alternate DOE-authorized

42 requirements. Because the assessment of radionuclide concentrations is part of the

43 assessment of radionuclide inventory and is essential to waste classification, this section also

44 addresses the review of compliance with the NDAA and DOE M 435.1-1 requirements related to

45 radionuclide concentrations and waste classification.

46

3-1
1 3.1 Inventory of Radionuclides in Waste

2

3 Evaluating the inventory of radionuclides in the waste is the first step in identifying highly

4 radioactive radionuclides and the extent to which they can be removed. Radionuclide

5 inventories also are needed to develop a source term model for a performance assessment and

6 inadvertent intruder analysis (see Section 4.3.3.1.3).

7

8 3.1.1 Areas of Review

9

10 The reviewer should evaluate the description of the radionuclide inventory in the waste,

11 including radionuclide activities and waste volumes. Radionuclides with relatively high

12 solubility, low sorption, high dose conversion factors, and/or significant ingrowth are of

13 particular significance.

14

15 The reviewer should evaluate the history of the wastes of interest, including information about

16 the generation of the waste streams identified in the waste determination and any treatment

17 processes (e.g., neutralization of acidic waste) that could influence the physical, chemical, or

18 radiological characteristics of the waste. The reviewer also should evaluate previous inventory

19 estimates and the reasons for any differences between the previous estimates and estimates

20 provided in the waste determination.

21

22 The reviewer should evaluate the sampling methodologies used to determine radionuclide

23 activities, including the rationale for the sampling approach, the particular sampling points

24 chosen, and the justification for the number of samples collected. The reviewer should evaluate

25 the spatial distribution of the radionuclides within the waste, including, if appropriate, both the

26 areal and vertical distribution of radionuclides. The reviewer should ensure that the sampling

27 methodology appropriately accounted for the heterogeneity of the waste. In assessing the

28 representativeness of samples, the reviewer should consider any reasons why wastes of

29 different composition may not have been adequately sampled (e.g., if the range of sample

30 depths in a tank is limited and wastes of different composition may have stratified). The

31 reviewer should evaluate the potential effects of access limitations (e.g., waste inside of

32 abandoned equipment or in sand pads, limited available risers or limited possibilities to create

33 new sampling ports in the tops of tanks) in limiting sample locations. In addition to evaluating

34 uncertainties due to sample variability (e.g., quantified as the variability among sample

35 measurements), the reviewer should evaluate additional uncertainty in radionuclide activities

36 that would result if the samples do not adequately represent waste heterogeneity. In assessing

37 waste heterogeneity, the reviewer should consider information about activities performed to mix

38 the waste and about any areas that may have remained unmixed.

39

40 The reviewer should evaluate the analytical methods used to characterize the radionuclide

41 inventory of the waste, including information about the calibration and sensitivity of the

42 instruments used to make the measurements. Any assumptions made and reported

43 uncertainties should be reviewed as well. The reviewer should evaluate the expected impact of

44 analytic uncertainty.

45

46 DOE may estimate concentrations of radionuclides that were not measured. Inventory

47 estimates may be based on historical knowledge (e.g., tracking of waste added to tanks) or

48 other types of process knowledge (e.g., waste treatment efficiencies or ORIGEN2 calculations

49 based on cladding and fuel types, burnup levels, cooling times, and other parameters). The

3-2
1 reviewer should evaluate parameter values and assumptions used in making these estimates.

2 The applicability of process knowledge estimates to the waste conditions should be evaluated.

3 For example, results of ORIGEN2 calculations to estimate radionuclide inventories may not be

4 applicable to waste in tanks in which radionuclides may have been removed to different extents

5 because of association with different physical phases. In general, inventory estimates based on

6 historical or process knowledge and special calculations are expected to be more uncertain

7 than estimates based on sample measurements, and the reviewer should evaluate the technical

8 basis for uncertainties in the estimated values or the technical basis for concluding that the

9 estimated values are conservative. If possible, the reviewer should compare the results of

10 similar calculations (e.g., estimates based on historical information, special calculations, or

11 process knowledge) to one another. If possible, the reviewer should also compare the results of

12 calculated estimates with sampled values to assess the reliability of the estimated values.

13 Reviewers should consider whether the results of a comparison made for one radionuclide can

14 provide information about the expected accuracy of the estimated inventory of chemically similar

15 radionuclides. Reviewers should determine whether there is an adequate technical basis for

16 the accuracy of estimates based on historical or process knowledge.

17

18 The reviewer should examine the methods used to determine the volume of waste used in

19 inventory calculations (e.g., use of geostatistical methods to calculate waste volumes based on

20 camera recordings of waste in tanks) and evaluate reported uncertainties in waste volumes.

21 The reviewer should evaluate the expected impact of volume uncertainties on the results of the

22 performance assessment.

23

24 3.1.2 Review Procedures

25

26 Radionuclide inventories support the evaluation of the removal of highly radioactive

27 radionuclides as well as the development of a source-term model (see Section 4.3.3.1.3). In

28 general, reviewers should evaluate information about waste history, sampling, measured

29 radionuclide activities, waste volumes, and calculations performed to estimate radionuclide

30 inventories, as well as the technical bases for the resulting radionuclide inventory estimates. It

31 is particularly important for reviewers to evaluate the technical bases for uncertainties in

32 inventory associated with sample heterogeneity or the use of historical or process knowledge

33 and to determine whether uncertainties in radionuclide inventories have been adequately

34 represented or bounded. Specifically, the reviewer should perform the following activities:

35

36 - Evaluate information about waste generation and treatment activities, and determine

37 whether the reported radionuclide concentrations appear to be consistent with expected

38 concentrations in contributing waste streams. For example, much lower concentrations

39 of fission products (e.g., Sr-90, Tc-99, Cs-137) and elements used in fuel cladding

40 (e.g., Zr, Al) would be expected in tanks receiving primarily second- or third-cycle wastes

41 as compared to tanks receiving primarily first-cycle extraction waste.

42

43 Verify that the predicted physical and chemical forms of radionuclides are consistent with

44 the properties of contributing waste streams and previous waste management activities

45 (e.g., precipitation of radionuclides during neutralization of acidic waste, partitioning of

46 radionuclides onto zeolites).

47

48 Evaluate previous inventory estimates, and verify that the technical bases for any

49 differences between historical and current estimates are adequate.

3-3
1 * Determine whether waste samples adequately represent heterogeneity of the waste.

2 Specifically evaluate the number, location, depth, and physical phases of samples as

3 well as the expected degree of mixing of the waste. Identify any unsampled wastes

4 (e.g., waste in abandoned equipment in tanks, waste in unsampled hardened

5 mounds) and determine whether the unsampled wastes may contribute significant

6 uncertainty to total radionuclide inventories. Verify that uncertainties resulting

7 from waste heterogeneity are adequately represented or bounded in the reported

8 radionuclide inventories.

9

10 * If applicable, evaluate sampling and analysis plans and data quality assessments, and

11 verify that relevant data quality objectives are met. If the data quality objectives are not

12 met, evaluate DOE's technical basis for concluding that the data are sufficient to support

13 the inventory estimates (e.g., a comparison of sampling results to previous sampling

14 results that met data quality objectives or predictions based on other techniques).

15

16 * Verify that estimates of the number of required samples provided in the sampling plan

17 are based on accurate assumptions about the heterogeneity of the waste. For example,

18 verify that calculations of the number of samples needed to provide the desired

19 statistical power or upper confidence limits are not based on the assumption that the

20 waste is well mixed if it is not well mixed.,

21

22 * Assess the technical basis for any identified limitations in the number or locations of

23 samples (e.g., limited number of sampling ports or internal obstructions in tanks,

24 difficulties in sampling specific phases of waste, significant worker hazards), and

25 confirm that the resulting uncertainties in total inventory have been adequately

26 represented or bounded.

27

28 * Evaluate the analytical methods used to measure. radionuclide concentrations, verify that

29 the analytical techniques used have the appropriate sensitivity for the radionuclides of

30 interest, and verify that the uncertainties in the analytical -methods (e.g., due to

31 instrument calibration) are either propagated into the inventory estimates or have been

32 adequately bounded.

33

34 * Verify that DOE has adequately described sampling and analytical uncertainties and

35 properly identified the uncertainty propagated into calculations of waste inventory

36 (e.g., ensure that analytic uncertainty is not substituted for sample variability).

37

38 * Evaluate the statistical metric of radionuclide concentrations used to calculate

39 inventories in the waste determination (e.g., mean, 95-percent upper confidence limit)

40 to ensure that the technical basis for the selection is adequate and the metric is

41 properly calculated.

42

43 * Evaluate methods used to estimate the inventory of highly radioactive radionuclides, and

44 determine whether reasonable efforts have been made to base concentrations for highly

45 radioactive nuclides on sample measurements. If the concentrations of highly

46 radioactive nuclides are based on calculations or process knowledge, verify that the

47 technical justification for using calculated rather than sampled values is adequate

48 (e.g., lack of analytical techniques with appropriate detection limits).

49

3-4
1 If techniques other than site-specific measurements are used to estimate radionuclide

2 concentrations (e.g., estimates based on historical knowledge or ORIGEN2

3 calculations), verify that the techniques have been appropriately verified and validated.

4 For example, compare any estimates made prior to sampling with sampled values, and

5 verify that the estimated values were accurate or conservative or that the reasons for

6 any nonconservative estimates are understood. Ensure that comparisons of predicted

7 and measured values provide an adequate basis for the reliability of estimates of

8 chemically similar radionuclides that have not been sampled.

9

10 If estimates are based on historical data (e.g., tracking of wastes added to a waste tank)

11 or process knowledge, ensure that significant sources of uncertainty (e.g., waste stream

12 variability, unknown waste streams) have been adequately characterized and

13 propagated in inventory estimates.

14

15 If estimates are based on process knowledge (e.g., ORIGEN2 calculations), verify that

16 the effects of subsequent waste management activities (e.g., precipitation of

17 radionuclides during neutralization of acidic waste and subsequent incongruent removal

18 of waste phases) are included appropriately in inventory estimates.

19

20 Confirm that DOE has an adequate technical basis for estimating the volume of the

21 waste. Evaluate the methods (e.g., geometry, models, statistical techniques) used for

22 estimating waste volumes, and confirm that uncertainty has been considered and

23 propagated into the inventory estimate. For example, if DOE uses geostatistical

24 methods to estimate tank waste residual volumes after radionuclide removal, verify that

25 the uncertainty resulting from the geostatistical estimate is adequately reflected in

26 the analysis.

27

28 3.2 Identification of Highly Radioactive Radionuclides

29

30 As discussed in Section 2.4.2, the NRC staff believes that highly radioactive radionuclides are

31 those radionuclides that contribute most significantly to risk to the public, workers, and the

32 environment (NRC, 2005). Because highly radioactive radionuclides are defined in terms of the

33 risk they pose to various receptors, the identification of highly radioactive radionuclides is

34 sensitive to changes made in the performance assessment, inadvertent intruder analysis, and

35 calculations of worker risk. Therefore, the choice of highly radioactive radionuclides should be

36 sufficiently conservative so that all potential highly radioactive radionuclides are included, or the

37 selection process should be iterative so that a radionuclide is added to the list if changes in the

38 relevant risk calculations increase the predicted risk significance of the radionuclide.

39

40 A list of highly radioactive radionuclides is expected to be specific to a particular waste

41 determination, and radionuclides that are identified as highly radioactive radionuclides in one

42 waste determination are not necessarily expected to be identified as highly radioactive

43 radionuclides in another waste determination.

44

45 3.2.1 Areas of Review

46

47 Because highly radioactive radionuclides are defined in terms of the risks they pose to various

48 receptors (see Section 2.4.2), the selected highly radioactive radionuclides ultimately must be

49 compared to the results of risk calculations. In general, the reviewer should evaluate the

3-5
1 - contribution of radionuclides present in the waste to radiological dose to members of the

2 general public (including inadvertent intruders) and workers. These exposures are expected to

3 occur through different pathways and at different times (see Example 1). In reviewing the

4 identification of highly radioactive radionuclides, it is particularly important that the reviewer

5 evaluate the potential uncertainties in predicted receptor doses (see Example 2). Potential

6 contributions to uncertainties in performance assessment and inadvertent intruder results are

7 discussed in Sections 4 and 5, respectively. In identifying uncertainties, the reviewer should

8 consider the results of independent performance assessment and inadvertent intruder analyses.

9

10 DOE may identify highly radioactive radionuclides by starting with radionuclide inventories and

11 eliminating radionuclides from the list of potential highly radioactive radionuclides based on

12 screening criteria. In these cases, the reviewer should pay particular attention to uncertainties

13 in radionuclide inventories (see Section 3.1) and assess the reasonableness of any screening

14 criteria used to remove radionuclides from the list of potential highly radioactive radionuclides.

15

16 DOE may use additional criteria to identify highly radioactive radionuclides. For example, in its

17 draft waste determination for closure of the Idaho Nuclear Technology and Engineering Center

18 Tank Farm Facility, at INL (DOE, 2005), DOE included all radionuclides in Table I of

19 10 CFR 61.55 as highly radioactive radionuclides. In general, reviewers should focus on

20 ensuring that all risk-significant radionuclides are included as highly radioactive radionuclides,

21 and they do not need to be concerned if DOE includes additional radionuclides as highly

22 radioactive radionuclides. When assessing whether highly radioactive radionuclides have been

23 removed to the maximum extent practical, the reviewer should focus on the removal achieved

24 for risk-significant radionuclides.

25

26 Example 1

27

28 DOE estimates that preparing a certain tank for closure by removing waste from the tank and

29 stabilizing the waste heel will result in a worker dose of I person-rem, primarily due to Cs-137.

30

31 In its performance assessment, DOE estimates that a hypothetical receptor that lives 100 m

32 [330 ft] from the tank farm and uses groundwater as a drinking water source will receive a peak

33 annual dose of 0. 03 mSv [3 mrem] at 3, 000 years after the end of active institutional controls.

34 Of this annual dose, DOE estimates 0.02 mSv [2 mrem] is due to ingestion of 1-129, 0.005 mSv

35 [0. 5 mrem] is due to ingestion of Se-79, 0.004 mSv [0.4 mrem] is due ingestion of Tc-99, and

36 0.001 mSv [0.1 mrem] is due to contributions of other radionuclides. In addition, DOE also

37 predicts that a hypothetical receptor living in the same location 5, 000 years after site closure will

38 receive an annual dose of 0. 015 mSv [1.5 mrem] due primarily to ingestion of Np-237.

39

40 DOE also predicts that an individual who drills through a tank and is inadvertently exposed to

41 waste will receive a peak dose of 2 mSv [200 mrem] I year after site closure. DOE predicts that

42 1 mSv [100 mrem] of this dose is attributable to direct radiation by Sn-126, 0.6 mSv [60 mrem]

43 is due to inhalation of Pu-239, 0.3 mSv [30 mrem] is attributable to inhalation of U-235, and

44 0. 1 mSv [10 mrem] is attributable to other radionuclides.

45

46 In this case, Cs-137, 1-129, Se-79, Tc-99, Np-237, Sn-126, Pu-239, and U-235 would be

47 identified as highly radioactive radionuclides for this waste determination.

48

3-6
1 Example 2

2

3 DOE plans to close a waste tank after removing waste from the tank and stabilizing the waste

4 heel with grout. DOE estimates that these activities will result in a worker dose of 1 person-rem,

5 almost entirely due to Cs-137. In its performance assessment, DOE estimates that a

6 hypothetical receptor that lives 100 m [330 ft] from the tank farm and uses groundwater as a

7 drinking water source will receive a peak annual dose of 0.015 mSv [1.5 mrem], almost entirely

8 due to Np-237, 5,000 years after site closure. DOE also estimates that an individual who drills

9 through a tank and is inadvertently exposed to waste will receive a peak dose of I mSv

10 [100 mrem], almost entirely due to direct radiation by Sn-126. Therefore, DOE's original list of

11 highly radioactive radionuclides for the waste determination includes only Cs-137, Np-237,

12 and Sn-126.

13

14 In a sensitivity analysis performed during NRC's review, DOE uses an alternate conceptual

15 model to predict that a hypothetical receptor living 100 m [330 ft] from the tank farm who uses

16 groundwater as a drinking water source will receive a peak annual dose of 0.02 mSv [2 mrem],

17 almost entirely due to Tc-99, 2,000 years after site closure. In this case, if the alternate

18 conceptual model does not represent a very unlikely scenario, Tc-99 should be added to DOE's

19 list of highly radioactive radionuclides for the waste determination.

20

21 3.2.2 Review Procedures

22

23 The reviewer should ensure that initial identification of highly radioactive radionuclides is

24 sufficiently conservative that it does not omit radionuclides that may be predicted to cause a

25 significant contribution to risk after uncertainties in risk calculations are resolved. The reviewer

26 should then evaluate any iterative analysis that DOE uses to refine the initial list, identify those

27 radionuclides that contribute most to dose, and identify those uncertainties that are expected to

28 have the most significant affect on predicted dose. Specifically, the reviewer should perform the

29 following review procedures.

30

31 If a screening analysis is used

32

33 - Ensure that the initial list of radionuclides included in the analysis is

34 comprehensive;

35

36 - Evaluate screening criteria DOE used to eliminate potential highly radioactive

37 radionuclides (e.g., short half-life, low total activity in the waste), and verify that

38 they are reasonable and sufficiently conservative; and

39

40 - Ensure that ingrowth of daughters is considered and that parent radionuclides

41 are not inappropriately screened from analysis.

42

43 9 Verify that DOE has considered the appropriate receptors (i.e., workers and

44 members of the public including inadvertent intruders) in defining its list of highly

45 radioactive radionuclides.

46

47 9 Ensure that uncertainties in radionuclide inventories are adequately represented in initial

48 lists of radionuclides used in screening procedures (see Section 3.1).

49

3-7
1 * Ensure that uncertainties in performance assessment and inadvertent intruder analyses

2 are adequately represented in the selection of highly radioactive radionuclides (see

3 Sections 4 and 5).

4

5 * Use independent analyses to assess which radionuclides are expected to cause the

6 most significant risk to members of the public, including the inadvertent intruders. Vary

7 model parameters and assumptions to evaluate a reasonable range of alternative

8 scenarios (e.g., regarding barrier performance, biointrusion, flooding, or seismic events).

9 Examine the reasons for any differences between DOE's list of highly radioactive

10 radionuclides and the radionuclides identified as causing significant risk in the

11 independent analyses, and request additional technical basis supporting the DOE

12 analysis, as necessary.

13

14 3.3 Radionuclide Removal Technology Selection

15 and Implementation

16

17 As discussed in Section 2.4.3, "removal" of radionuclides refers to both removal of waste from a

18 disposal system (either by removing waste alone or by removing contaminated structures that

19 contain waste) and treatment of waste to remove radionuclides from the waste stream. As

20 discussed in Sections 2.4.2 and 2.4.3, there are differences between the NDAA, DOE

21 Order 435.1 (DOE, 2001), and the West Valley Policy Statement (NRC, 2002) requirements

22 regarding the extent of removal of radionuclides, and NRC staff believes the NDAA wording

23 allows for broader considerations in demonstrating compliance with this criterion. Typically,

24 however, reviewers should expect to evaluate a quantitative analysis that demonstrates that

25 radionuclides have been removed to the maximum extent practical. For example, impacts of

26 additional removal activities on removal schedules may be related to cost or worker risk.

27

28 Because DOE may submit a waste determination either before (DOE, 2005a) or after (DOE,

29 2005b) it has stopped relevant removal operations, evaluation of compliance with the

30 radionuclide removal criterion may be based on either the extent of removal DOE has

31 performed or the removal that DOE indicates it will achieve before final disposal actions are

32 taken. Thus, the reviewer may conclude either that highly radioactive radionuclides "have been"

33 or "will be" removed to the maximum extent practical. If DOE submits a waste determination for

34 INIL or SRS prior to ending removal actions, NRC staff will expect to monitor the extent of

35 radionuclide removal achieved and assess any impacts on meeting the performance objectives

36 of 10 CFR Part 61; Subpart C (Section 10), including the ALARA requirement of 10 CFR 61.41

37 (see Section 4.7). If removal activities are not completed as described in DOE's waste

38 determination, conclusions NRC, staff made regarding radionuclide removal to the maximum

39 extent practical that were based on the waste determination review may no longer be valid.

40 However, NRC will not reassess its conclusions about radionuclide removal or compliance with

41 NDAA Criterion 2 during monitoring, becaus e NRC's monitoring role under the NDAA is limited

42 to assessing compliance with the performance objectives of 10 CFR 61, Subpart C.

43

44 In general, DOE's technology selection process is expected to focus on relatively mature

45 technologies. However, less mature technologies may be relevant if DOE proposes a multistep

46 removal procedure in which some technologies may not be implemented for several years after

47 DOE's final waste determination. Reviewers also may want to note less mature technologies

48 they encounter during their reviews for possible consideration during subsequent reviews.

49

3-8
1 3.3.1 Areas of Review

2

3 As discussed in Section 2.4.3, an NRC reviewer is expected to evaluate both technical and

4 economic aspects of radionuclide removal. In general, review of the technical aspects of

5 radionuclide removal is expected to include an assessment of the technologies DOE selected to

6 perform radionuclide removal, while review of the economics of additional removal is expected

7 to include an assessment of the costs and benefits of additional radionuclide removal (see

8 Section 3.4). Although reviews of technology selection and cost-benefit analyses are expected

9 to be performed for each waste determination review, some components of the review may

10 depend on the timing of the submission of the waste determination with respect to the status of

11 removal actions. Specifically, if DOE stops relevant removal operations before submitting a

12 waste determination, the review should include an evaluation of the removal actions that have

13 occurred and the decision to stop removal activities, while reviews of waste determinations

14 submitted prior to stopping radionuclide removal operations should include an evaluation of the

15 criteria DOE establishes to determine when removal is complete.

16

17 In reviewing the selection of radionuclide removal technologies, the reviewer should evaluate

18 the decision process DOE used to select appropriate technologies as well as the final

19 technology selections. Reviewers should evaluate the range of technologies DOE considered,

20 the sources of information DOE used, and how information was used in DOE's technology

21 selection process. Information about available technologies may be found in reports generated

22 by other DOE sites, reports from third parties [e.g., the National Academy of Sciences (NAS) or

23 Defense Nuclear Facilities Safety Board (DNFSB)], and reports from industrial or international

24 sources. In addition to evaluating the range of technologies DOE considered, reviewers Should

25 evaluate whether DOE considered potentially beneficial sequencing of and synergisms among

26 different technologies.

27

28 In assessing removal actions that have been stopped, the reviewer should evaluate the

29 selection process based on the information and technologies available at the time of selection.

30 In assessing the practicality of additional radionuclide removal, the reviewer should assess

31 technologies available at the time of the review, including technologies that have been used

32 successfully at other sites are of particular interest. Reviewers should evaluate DOE's rationale

33 for selection of waste removal techniques, including a comparative assessment of the technical

34 and economic characteristics of the techniques considered.

35

36 NRC staff believes that, in many cases, the intent of requiring removal of highly radioactive

37 radionuclides to the maximum extent practical can be satisfied by reducing the volume of

38 residual waste in a, contaminated structure (e.g., a tank, an evaporator) to the maximum extent

39 practical. However, as discussed in Section 2.4.3, reviewers also should consider (1) whether

40 it would be practical to remove selected highly radioactive radionuclides from the waste (e.g., by

41 chemical extraction) or (2) whether it would be practical to remove the contaminated structure

42 for disposal instead of stabilizing it and disposing of it in place. As discussed in Section 3.4, in

43 some cases a relatively simple analysis may demonstrate that an alternative is not practical.

44

45 To the extent practical, reviewers should consider the impacts of the proposed waste

46 management activities and alternative waste management activities on the broader waste

47 management system. For example, if generating additional liquid waste presents technical

48 challenges because of tank space limitations, reviewers should consider whether alternate

49 technologies would generate less secondary liquid waste than the proposed technologies

3-9
1 (e.g., by recycling liquids rather than using clean water). Reviewers also should consider any

2 physical or chemical impacts of removal methods on downstream processes (e.g., effects of

3 oxalic acid on evaporators or vitrification equipment).

4

5 In addition to reviewing DOE's technology selection process, reviewers should evaluate the

6 technical basis for stopping removal activities. In general, the decision to terminate removal

7 activities should be based on a demonstration that additional removal would be impractical. For

8 example, a statement that 99 percent of waste has been removed from a tank is not a sufficient

9 basis for stopping removal, but a demonstration that removing the remaining waste would not

10 substantially reduce risks and would cause excessive worker dose would be sufficient. In

11 assessing the basis for stopping removal activities, the reviewer should evaluate available

12 documentation of removal goals that were established before radionuclide removal waste

13 started. The reviewer should evaluate both the technical basis for the original removal goal and

14 the consistency of the removal achieved with the removal goal. The actual extent of removal

15 achieved in terms of radionuclide inventories and the uncertainties in those inventories should

16 be reviewed as described in Section 3.1.

17

18 Although removal fractions alone are not expected to provide a basis for terminating removal

19 activities, they may help a reviewer assess the success of competing removal technologies. If

20 removal efficiencies are used to compare the success of competing technologies, reviewers

21 should ensure efficiencies are based on comparable starting points. For example, with respect

22 to removal of waste from tanks, reviewers should determine whether starting inventories were

23 based on the historical maximum radionuclide inventories, inventories after bulk removal, or

24 another baseline inventory. Comparisons are expected to be useful only if consistent baselines

25 can be established. Reviewers should note that the distinction between "bulk" and "heel"

26 removal typically is subjective.

27

28 If removal activities are stopped before removal goals are reached or if removal activities have

29 been stopped and no information about removal goals is available, reviewers should assess

30 DOE's basis for stopping removal. For example, if DOE indicates that radionuclide removal was

31 stopped because of declining removal efficiency (e.g., decreasing amount of waste removed

32 from a tank per mixing cycle), the reviewer should evaluate whether DOE considered

33 opportunities to improve effectiveness (e.g., by redirecting mixing jets). The reviewer also

34 should evaluate whether continued removal at the decreased efficiency still produces significant

35 removal. For example, removal efficiency may have declined from 5,000 liters [1,300 gal] to

36 1,000 liters [260 gal] of waste per mixing cycle, but removal of 1,000 liters [260 gal] of Waste per

37 mixing cycle may still be practical. If DOE indicates that waste removal was stopped because of

38 equipment failure, the reviewer should investigate the costs and other impacts (e.g., on

39 schedule) of replacing the failed equipment. In general, if DOE identifies schedule constraints

40 as a reason why waste removal actions are stopped or why additional removal actions cannot

41 be completed, reviewers should assess the implications of the identified schedule impacts on

42 more quantitative metrics such as cost in comparison to worker risk.

43

44 If a waste determination is submitted prior to completion (or commencement) of waste removal

45 activities, the reviewer should evaluate DOE's criteria for determining when waste removal is

46 complete. Essentially, a reviewer should evaluate the technical basis for concluding DOE will

47 meet its removal goals and the practicality of achieving a greater extent of radionuclide removal

48 than required by the DOE proposed criteria. For example, if DOE proposes that removal will be

49 complete if a certain volume of waste has been removed from a tank, the reviewer should

3-10
1 evaluate DOE's technical basis for concluding the specified volume of waste will be removed

2 and the practicality of removing a greater volume of waste from the tank. Similarly, if DOE

3. proposes to remove radionuclides from a waste stream with a chemical treatment process, the

4 reviewer should evaluate the technical basis for the predicted effectiveness of removal of

5 radionuclides from the waste stream as well as the practicality of accomplishing additional

6 radionuclide removal.

7

8 For removal activities that have not been completed, the reviewer also should identify the main

9 factors that could cause changes in the proposed approach. For example, a technology that is

10 less mature may introduce greater uncertainty in the extent of radionuclide removal that can be

11 accomplished or increase the cost of the proposed waste management activities as compared

12 to more mature technologies. To assess technological maturity, the reviewer should assess

13 information about technologies that have been used or developed at other DOE sites as well as

14 reports from third parties (e.g., NAS or DNFSB). If DOE proposes a-technology that has not yet

15 been used successfully under similar situations, the reviewer should evaluate DOE's plans for

16 changing the waste management approach to accommodate unforeseen problems (e.g., DOE's

17 plans for using alternate technologies to complete radionuclide removal if the originally selected

18 technology cannot achieve the removal goals). Additional uncertainties in the conclusion that

19 radionuclides will be removed to the maximum extent practical may result if radionuclide

20 removal plans extend over long time periods or if removal activities are not, expected to begin for

21 a significant amount of time after a waste determination is submitted (e.g., greater than 5 years).

22 These uncertainties may result because it may be difficult to conclude that the proposed

23 radionuclide removal activities will remain practical in the future (e.g.-, because of changing

24 programmatic goals). If waste treatment activities are expected to begin several years after the

25 waste determination has been submitted, the reviewer should evaluate DOE's process for

26 considering technological developments that occur after the submission of the waste

27 determination. In addition, reviewers must consider uncertainties in proposed waste

28 treatment schedules when evaluating the costs and benefits of a particular treatment approach,

29 because changes in the schedule could significantly affect the relative costs of various

30 treatment alternatives.

31

32 The primary benefit of radionuclide removal is expected to be a reduction in the risk the waste

33 will pose to the general public, including inadvertent intruders. Because the performance

34 assessment and inadvertent intruder analysis provide the basis for quantifying the risk the

35 waste will pose to members of the public, an analysis of the costs and benefits of additional

36 radionuclide removal is expected to depend in part on the performance assessment and

37 inadvertent intruder analysis dose predictions. In addition, radionuclide removal may affect the

38 risk to individuals during operations (see Section 6) or site stability (see Section 7). Therefore,

39 the reviewer should evaluate the consistency of information presented in a cost-benefit analysis

40 to support conclusions about the practicality of additional radionuclide removal with information

41 reviewed using Sections 4-7 of this guidance document. For example, if additional removal

42 would require changes to the physical or chemical form of the waste, the reviewer should,

43 evaluate the potential impacts of the changes on site stability. Similarly, if DOE indicates that

44 additional removal would cause unacceptable worker risks, the consistency of the predicted

45 worker risks due to additional radionuclide removal with the information presented regarding

46 protection of workers during operations should be evaluated. Furthermore, if changes to the

47 performance assessment or inadvertent intruder analysis are made during the review process,

48 the reviewer should evaluate potential impacts on any cost-benefit analysis used to support the

49 conclusion that highly radioactive radionuclides have been removed to the maximum extent

3-11
1 -, practical. Additional information about reviewing cost-benefit analyses is provided in

2 Section 3.4.

3

4 3.3.2 Review Procedures

5

6 Reviewers should evaluate waste management activities that DOE has performed or proposed

7 as described in the waste determination in comparison to alternate waste management

8 activities. In addition, reviewers should evaluate the technological feasibility and practicality

9 of additional removal of radionuclides. Specifically, the reviewer should perform the

10 following assessments:

11

12 Review DOE's basis for radionuclide removal technology selection. Determine whether

13 a reasonable range of potential technologies was evaluated by comparing the list of

14 technologies considered to technologies used or developed at other DOE sites, in

15 industrial applications, and in the international community, and by reviewing relevant

16 documents by other organizations, if available (e.g., NAS, DNFSB). Technologies

17 considered should include, but not necessarily be limited to, sluicing (e.g., Schlahta and

18 Brouns, 1998), mixing (e.g., Leishear, 2004; Hatchell, et al, 2001), chemical cleaning

19 (e.g., Sams, 2004), vacuum retrieval techniques (e.g., Sams, 2004), mechanical

20 manipulators (e.g, DOE, 1998; Evans, 1997), and robotic vehicles (e.g., Vesco,

21 et al., 2001).

22

23 As appropriate, determine whether DOE considered both methods to (1) remove waste

24 from the disposal system (either by reducing the volume of waste in a contaminated

25 structure or by removing a contaminated structure for disposal) and (2) remove

26 radionuclides from relevant waste streams (e.g., chemically extracting radionuclides

27 from waste that will remain in a tank).

28

29 Review DOE's documentation of its process for selecting radionuclide removal

30 technologies, and determine whether the selection process was based on appropriate

31 sources of information that were reasonably current at the time the technology selections

32 were made (e.g., expert elicitation, reports from other DOE sites, reports from industrial

33 or international sources).

34

35 Determine whether the criteria DOE used to select radionuclide removal technologies

36 are reasonable. In general, reviewers should expect that selection criteria include an

37 estimate of the likelihood of achieving removal goals With the selected technology, the

38 technological uncertainties associated with each technology (e.g., technological

39 maturity), the costs of implementing the technology, and an evaluation of the

40 system-wide impacts of using the technology (e.g., chemical effects on downstream

41 systems, generation of secondary waste streams requiring storage).

42

43 If waste treatment activities are expected to begin several years after the waste

44 determination has been submitted, evaluate DOE's process for considering

45 technological developments that occur after the submission of the waste determination.

46 Determine whether the process will require evaluation of an appropriate range of

47 alternative technologies and will allow DOE to assess whether it would be practical to

48 improve radionuclide removal by implementing a technology that was developed or

49 improved after submission of the waste determination.

3-12
2 * Examine DOE's documentation of radionuclide removal activities that have been

3 stopped, and verify that key reasons used to support the termination of removal

4 operations (e.g., availability of equipment, changes in equipment performance,

5 programmatic considerations) were reasonable. For example, if DOE cites equipment

6 deterioration as a reason for stopping removal, evaluate efforts to replace failing

7 equipment or improve equipment performance.

8

9 * Determine whether decisions to stop waste removal activities based on programmatic or

10 schedule constraints can be supported by an evaluation of the costs and potential

11 benefits of continuing removal operations.

12

13 * If predicted doses to members of the public (including inadvertent intruders) were used

14 to support the decision to stop radionuclide removal activities, determine whether

15 uncertainties in the dose estimates would significantly affect the metrics used to support

16 the decision to stop removal (e.g., cost per averted dose).

17

18 * Identify any removal goals DOE established before radionuclide removal began, and

19 determine whether the goals have been met. If the goals have been met, evaluate the

20 technical basis for the goals, and determine whether the goals were consistent with

21 radionuclide removal to the maximum extent practical (i.e., determine whether

22 significantly more radionuclide removal than required by the removal goals would have

23 been practical).

24

25 * If removal goals DOE identified prior to radionuclide removal efforts have not been met,

26 determine whether the technical basis for stopping removal prior to achieving the

27 removal goals is adequate. For example, if technological limitations are cited as the

28 reason goals were not met, the reviewer should determine why waste removal *was more

29 difficult than originally predicted (e.g., because of poor equipment performance or

30 unforeseen characteristics of the waste).

31

32 * If DOE based its decision to terminate removal activities on declining removal efficiency,

33 verify that reported removal efficiencies are reasonably reliable. For example, if

34 detectors are placed on the outside of piping to measure the activity of waste being

35 removed from a tank, verify that the detectors have the appropriate sensitivity when

36 placed outside of the pipe to provide a reliable estimate of waste removal.

37

38 * If DOE based its decision to terminate removal activities on declining removal efficiency,

39 determine whether DOE considered whether modifications to the removal process

40 (e.g., redirection of mixing jets) could improve removal.

41

42 * If DOE based its decision to terminate removal activities on declining removal efficiency,

43 determine whether DOE considered whether it would be practical to implement alternate

44 technologies or methods to improve removal.

45

46 * If removal operations have not been completed, verify that DOE's proposed criteria for

47 terminating removal operations include minimum standards that are consistent with

48 meeting the performance objectives. For example, if DOE will conclude tank waste

49 removal is complete when the removal rate decreases to a certain value, verify that the

3-13
1 criteria also contain minimum removal amounts such that the inventories of highly

2 radioactive radionuclides left in the tank (including uncertainties) will be consistent with

3 or less than the source term used in the performance assessment and inadvertent

4 intruder analysis (see Section 4.3.3.1.3).

5

6 * If removal operations have not been completed, examine DOE's criteria for terminating

7 removal operations and determine whether additional removal would be practical. For

8 example, if removal of waste in a tank is to be considered complete when the removal

9 rate drops to a certain value, determine whether continuing operation would be expected

10 to result in a cost-effective reduction in dose to a member of the public (see Section 3.4).

11

12 * If removal operations have not been completed, verify that predicted removal efficiencies

13 for proposed removal operations are supported by a sufficient technical basis. For

14 example, if waste will be treated by sorption of radionuclides onto a finely dispersed solid

15 and subsequent filtration of that solid from the liquid waste, determine whether the

16 reported predicted efficiencies of sorption and filtration are consistent with efficiencies

17 observed during laboratory or pilot-scale tests under similar conditions or similar

18 experience at DOE sites.

19

20 * Identify technological challenges DOE described as limiting factors in radionuclide

21 removal. If a stated technological challenge is expected to recur in subsequent removal

22 activities (e.g., if a waste with problematic physical characteristics is present in other

23 tanks at the site), note the challenge DOE efforts to resolve it in the TER (see Section 9).

24

25 * Review any cost-benefit analysis used to support the decision that additional

26 radionuclide removal would not be practical (see Section 3.4), and confirm that the

27 analysis supports the conclusion that highly -radioactive radionuclides have been

28 removed to the maximum extent practical.

29

30 3.4 Cost-Benefit Analysis

31

32 Section 3.3 guides reviewers evaluating whether DOE has optimized its selection and

33 implementation of radionuclide removal technologies to remove highly radioactive radionuclides

34 to the maximum extent practical. This section provides additional guidance specifically focused

35 on assessing the practicality of additional radionuclide removal, which typically is evaluated with

36 some form of cost-benefit comparison ( e.g., Gilbreath, 2005). In this guidance, the term

37 "additional removal" indicates either more radionuclide removal than DOE already has

38 performed, if DOE has terminated removal operations or more radionuclide removal than DOE

39 indicates it plans to perform if DOE has based its waste determination on removal activities

40 that are not complete. "Additional", radionuclide removal also indicates removal beyond the

41 removal performed to meet the applicable performance objectives, which must be met

42 irrespective of practicality.

43

44 In general, the reviewer should determine whether it is practical to reduce the inventory of

45 radionuclides addressed in DOE's waste determination. Although the reviewer may note

46 opportunities to optimize removal on a larger scale (e.g., by removing more waste from tanks

47 without cooling coils so that less waste will need to be removed from tanks with cooling coils to

48 meet the performance objectives), these decisions may be beyond the scope of an individual

49 waste determination. The reviewer may note these observations in a TER, but should not use

3-14
1 them as a basis for determining whether highly radioactive radionuclides have been removed to

2 the maximum extent practical.

3

4 As discussed in Section 2.4.3, the NDAA allows for a broader range of factors to be considered

5 in the evaluation of the practicality of waste removal than allowed by the Manual for DOE Order

6 435.1 or the West Valley Policy Statement. However, the NRC staff believes that these factors

7 should be quantified, to the extent possible, in terms of financial costs and potential doses to

8 workers and members of the public (including inadvertent intruders) to facilitate comparison

9 of options.

10

11 3.4.1 Areas of Review

12

13 The reviewer should evaluate DOE's description of the potential risks, costs, and benefits

14 associated with various options for additional radionuclide removal. -Costs could include, but not

15 necessarily be limited to, financial costs, delays, increases in risks to workers and members, of

16 the public, system impacts (e.g., generation of secondary waste streams requiring storage in

17 tanks), and transportation risks (if waste is moved offsite for disposal). Benefits may include,

18 but not necessarily be limited to, decreases in radiological risks to workers and members of the

19 pu 'blic (including inadvertent intruders), reduction in impacts on natural resources, and reduction

20 in costs of other entities incurred because of effects on natural resources.

21

22 Table 3-1 lists potential costs and benefits associated with radionuclide removal. In general, the

23 level of detail of the review should be based on the level of detail necessary to distinguish

24 between various options and to compare the practicality of additional removal with the

25 practicality of completed removal activities or other proposed waste management activities. In

26 many cases, a simplified screening analysis may be sufficient to eliminate particular waste

27 management alternatives. Therefore, it may not be necessary to consider all of the potential

28 costs and benefits listed in Table 3.1 in every case. The primary costs and benefits considered

29 in most cases are expected to be financial costs and increases or decreases in potential doses

30 to workers and members of the public.

31

32 The comparison of potential costs and benefits should be quantitative to the extent practical.

33 For example, if DOE indicates that additional radionuclide removal is impractical because it

34 would significantly delay its tank closure schedule, the reviewer should evaluate any increases

35 in dose or financial cost that DOE expects to result from the schedule delay. In reviewing the

36 waste determination for salt waste disposal at the Savannah River Site, NRC staff considered

37 the potential costs of schedule impacts, facility slowdown, and tank space issues in evaluating

38 the practicality of additional removal of highly radioactive radionuclides (NRC, 2005).

39

40 Although quantitative comparisons are easier to make than qualitative comparisons, qualitative

41 information that may help reviewers to compare various options (e.g., potential environmental

42 benefits) also should be considered. Furthermore, in some cases, qualitative differences are

43 recognized, and purely quantitative comparisons may be inappropriate. For example,

44 radiological risks to workers are not directly comparable, on a quantitative basis, to predicted

45 doses to members of the public, because worker risks are accepted risks, whereas members of

46 the public are likely to be unaware of, and may derive no benefit from, the actions that could

47 lead to a radiological dose.

48

49

3-15
1-

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

Table 3-1. Potential Costs and Benefits Associated With Performing Additional

Radionuclide Removal Beyond Removal Performed to Meet the Applicable

Performance Objectives

Potential Benefits Potential Costs

Averted long-term dose to members of the Radiological dose to workers due to

public, including potential inadvertent additional radionuclide removal activities

intruders

Reduction in radiological dose to workers Financial costs of additional radionuclide

because of increased waste stabilization, removal

decreased numbers of waste transfers in

tank farms, or other similar considerations

Decrease in costs of other entities, such as a Additional transportation risks

reduction in costs incurred by public water

supply utilities to meet the requirements of

the Safe Drinking Water Act

Reduction of impact on natural resources, Chemical and physical effects of removal

such as groundwater aquifers activities on downstream waste processing or

storage systems

Improvement of esthetics, changes in land Additional impacts on DOE's mission or

use, and reduction in monitoring costs* schedule

Doses to the public due to additional removal

activities

Environmental disruption due to additional

removal activities

Nonradiological workplace accidents due to

additional removal activities

*Not expected to be applicable in most cases, as discussed in the text.

In general, dose limits that are protective of human health are expected to be protective of nonhuman species as well [e.g., (ICRP, 1991)]. However, it is appropriate to consider any

significant environmental benefit or detriment that could result from additional radionuclide

removal. For example, if removing additional waste would significantly reduce environmental

risks by reducing the release of radionuclides from a waste, it would be appropriate to consider

that as a benefit of additional radionuclide removal. Alternately, if exhuming contaminated

piping would cause environmental disruption, it would be appropriate to consider that impact as

a cost of additional radionuclide removal. In addition, it is possible that releases from waste that

meets the performance objectives of 10 CFR Part 61, Subpart C, could cause wellhead

concentrations of some radionuclides to exceed U.S. Environmental Protection Agency's

Maximum Contaminant Levels. As discussed in other contexts.(e.g., NRC's guidance regarding

ALARA analyses for license termination [NRC, 2003b, Appendix N]), it is appropriate to include

3-16
1 the potential reduction in costs that other entities, such as public water supply utilities, may incur

2 to meet the requirements of the Safe Drinking Water Act as benefits of additional radionuclide

3 removal in cost-benefit analyses.

.4

5 Improved esthetics and changes in future land use typically are relevant to decisions between

6 alternatives that result in different potential land uses. These considerations are not expected

7 to apply to most waste determinations because (1) most relevant wastes are located among

8 industrial facilities that DOE intends to control for the foreseeable future and (2) most

9 radionuclide removal or disposal options are not expected to result in significantly different

10 possible land use scenarios. However, these considerations are listed as a potential benefit of

11 additional removal because some radionuclide removal options, such as exhuming tanks or

12 buried equipment, could permit different potential land uses than alternative options would

13 allow. Similarly, changes in monitoring costs are not expected to be relevant to most waste

14 determinations, because similar monitoring activities are expected to be appropriate following

15 most radionuclide removal options. However, reduction in monitoring costs are included as a

16 potential benefit because some radionuclide removal options could limit the need for certain

17 monitoring activities.

18

19 As previously noted, most cost-benefit analyses to support waste determinations are expected

20 to be relatively simple. However, in some cases, more detailed cost-benefit analyses may be

21 used to evaluate the practicality of a proposed approach. General guidance on cost-benefit

22 analysis is discussed in several reports (NRC, 1997; Office of Management and Budget, 1992,

23 2003). NRC also has developed cost-benefit analysis guidance for environmental reviews

24 (NRC, 2003a, Section 6.7) and for site decommissioning (NRC, 2003b, Vol. 2, Appendix N).

25 Cost-benefit assessment for a hypothetical low-level waste (LLW) disposal facility is described

26 in the Draft Environmental Impact Statement NRC prepared for 10 CFR Part 61 (NRC, 1981,

27 Vol. 2, Section 3.8). Reviewers may refer to these reports for general guidance about

28 cost-benefit analysis techniques and parameters. For example, if DOE presents a detailed

29 cost-benefit analysis that includes non-radiological accidents and transportation risks as costs

30 of additional radionuclide removal, a reviewer may compare the risks of fatalities due to

31 transportation and industrial accidents used in DOE's analysis to the values provided in

32 Table N.2 of NRC's guidance for license termination (NRC, 2003b). Although DOE may use

33 parameter values that differ from values presented in Office of Management and Budget (OMB)

34 or NRC guidance documents, reviewers may compare DOE's values to values presented in

35 these guidance documents to determine an appropriate level of detail for their evaluation of

36 DOE's parameter values. In general, reviewers are expected to perform a detailed review of

37 parameter values that significantly affect the analysis results and that differ from the values

38 presented in other NRC or OMB guidance.

39

40 Although many of the underlying principles and methods described in general guidance about

41 cost-benefit analyses may be applicable, certain specific aspects of the general guidance are

42 not expected to be applicable to waste determination reviews. Most notably, it is unclear

43 whether it is appropriate to apply specific cost-benefit metrics discussed in the general guidance

44 to DOE waste determinations. It appears to be more appropriate to compare the costs and

45 benefits of additional radionuclide removal to the costs and benefits of other similar DOE

46 risk-reduction activities (see Examples 1-4). In particular, the $2,000 per person-rem

3-17
1 conversion factor2 that NRC uses in some contexts (e.g., regulatory analyses, ALARA analyses

2 for license termination) may not be a useful metric to apply to waste determination reviews,

3 because the metric is based on collective dose and it is designed to be applied with economic

4 discounting. The long performance period relevant to waste determinations hinders the use of

5 any metric based on collective dose because it is unrealistic to attempt to predict what the

6 population near a disposal site will be for thousands of years after site closure. In addition,

7 NRC staff previously has recommended that the monetary value associated with averted future

8 doses not be discounted in analyses relevant to 10 CFR Part 61 (NRC, 2000).

9

10 Example 1

11

12 DOE indicates it would cost $1,000, 000 to remove an additional 4, 000 L [1,060 gal] of waste

13 from a tank and that removal would reduce the predicted 50-year dose to a member of the

14 public by 0.05 mSv [5 mremJ. Thus DOE calculates additional radionuclide removal would cost

15 approximately $20,000,000 per mSV [$200,000 per mrem] and decides not to perform additional

16 removal. The reviewer would compare this cost (normalized to dose reduction) to the

17 normalized cost DOE incurs in other similar risk-reduction activities. A finding that

18 $20,000,000 per mSv [$200, 000 per mrem] is significantly greater than the normalized cost

19 DOE typically incurs in similar risk-reduction activities would support the decision that highly

20 radioactive radionuclides had been removed to the maximum extent practical.

21

22 Example 2

23

24 DOE determines it could use a chemical process to reduce the concentration of actinides in a

25 waste stream by 85 percent at a cost of $10,000,000. Because the release of actinides from the

26 final wasteform is expected to be solubility limited, the concentration reduction is not expected

27 to significantly affect the dose to a member of the public whose primary exposure pathway is

28 groundwater consumption. However, the concentration reduction is expected to reduce the

29 estimated dose to an inadvertent intruder from 2 mSv [200 mrem] to 0.03 mSv [30 mrem]. A

30 finding that $5,900,000 per mSv averted [$59, 000 per mrem] is significantly greater than the

31 cost DOE typically incurs to avert potential doses to inadvertent intruders would support

32 the decision that highly radioactive radionuclides had been removed to the maximum

33 extent practical.

34

35 Cost-benefit analyses are expected to be relatively simple in most cases. However, significant

36 uncertainties should be considered. The main sources of uncertainty are expected to be the

37 amount of radionuclide removal that could be accomplished by implementing a particular

38 radionuclide removal technology and the resulting reduction in dose. If significant,

39 uncertainties in the cost of implementing a particular removal technology also should be

40 included, However, in many cases, uncertainties in the predicted dose may be significantly

41 greater than cost uncertainties.

42

43

2

The basis for NRC's $2,000 per person-rem metric is discussed in NUREG-1530 (NRC, 1995a).

3-18
1 Example 3

2

3 DOE determines it could remove 12, 000 L [3,200 gal] of additional waste from a tank at a cost

4 of $10,000,000. DOE also determines that removing the additional waste would reduce the

5 potential 50-year dose to a member of the public by 0. 02 mSv [2 mrem]. Based on the

6 $500,000,000 cost per mSv averted [$5, 000, 000 per mrem], DOE determines that additional

7 removal would be impractical. However, revisions to the performance assessment made as a

8 result of the review process indicate the potential dose to a member of the public is much

9 greater than originally predicted, but still within the limits established by the performance

10 objectives of 10 CFR Part 61. As a result, DOE determines that removal of 12,000 L [3,200 gal]

11 would reduce the potential 50-year dose to a member of the public by 10 mSv [1, 000 mrem]

12 (e.g., by reducing the annual dose to an individual by 0.20 mSV[20 mrem] for 50 years]. If the

13 resulting $1,000,000 cost per mSv averted [$10,000 per mrem] is similar to the cost per averted

14 dose DOE incurs in similar risk-reduction activities, the reviewer should question DOE's

15 assessment that additional radionuclide removal is not practical.

16

17 Example4

18

19 DOE determines it could use a combination of a high-pressure water jet and a new type of

20 transfer pump to remove approximately 12, 000 L [3,200 gal] of additional waste from a tank at a

21 cost of $2,000,000. However, DOE estimates that the new technology may remove as much as

22 24,000 L [6,300 gal] or as little as 6,000 L [1,600 gal] of waste from the tank. DOE estimates

23 that removal of 12, 000 L [3,200 gal] of additional waste would result in a 2 mSV [200 mrem]

24 reduction in the 50-year dose to a hypothetical member of the public. After considering

25 uncertainties in the estimate, DOE has confidence that the dose reduction resulting from

26 removal of 12,000 L [3,200 gal] would be between 0. 5 mSv [50 mrem] and 3 mSV [300 mrem].

27 DOE also estimates that the expected dose reduction would be roughly proportional to the

28 volume of waste removed. Therefore, DOE estimates that removal of 24,000 L [6,300 gal] of

29 waste would result in a potential 50-year dose reduction of 1 mSv [100 mrem] to 6 mSv [600

30 mrem] and that removal of 6, 000 L [1,600 gal] would result in a 50-year dose reduction of 0. 25

31 mSv [25 mrem] to 1.5 mSv [150 mrem]. The resulting estimated cost per averted dose would

32 range from $330,000 per mSv averted [$3,300 per mrem] to $8,000,000 per mSv averted

33 [$80,000 per mrem]. If this range spans the range of costs (normalized to dose reduction) DOE

34 incurs in similar risk-reduction activities, reviewers would need to rely on the value of the best

35 estimates of the normalized cost, the probability that the normalized cost will be significantly

36 different from the normalized costs DOE incurs to achieve similar risk-reductions, and

37 consideration of additional factors (such as unquantifiable factors listed in Table 3-1 and the

38 factors discussed in Section 3.3) to determine whether DOE has removed highly radioactive

39 radionuclides to the maximum extent practical.

40

41 3.4.2 Review Procedures

42

43 The reviewer should evaluate the risks, costs, and benefits associated with alternative waste

44 management strategies and radionuclide removal technologies to determine whether there is

45 sufficient technical justification to conclude that waste removal is complete, or whether it is

46 practical to achieve further radionuclide removal. In conjunction with the review described in

3-19
1 Section 3.3, the reviewer should support a decision regarding the practicality of additional

2 radionuclide removal by following these review procedures:

3

4 Confirm that the cost-benefit analysis includes a site-specific description of the affected

5 environment, alternative waste management strategies considered, and different

6 removal technologies evaluated. Confirm that estimated benefits of the different

7 radionuclide removal technologies and waste management strategies are clearly stated

8 (e.g., by estimating the reduction in risk or dose to the public, workers, and/or the

9 environment over time that is associated with various options).

10

11 Determine whether information about radionuclide removal technologies used in the

12 cost-benefit analysis is reasonably current. Specifically, confirm that the most

13 appropriate technologies have been considered in the cost-benefit analysis (see

14 Section 3.3), and verify that the extent of radionuclide removal that could be achieved is

15 not underestimated.

16

17 Verify that the potential benefits of additional removal are consistent with the results of

18 the performance assessment (Section 4) and inadvertent intruder analysis (Section 5).

19 Ensure that potential uncertainties in dose predictions are adequately represented in the

20 cost-benefit analysis (i.e., if doses could be significantly greater than doses assumed in

21 the cost-benefit analysis, the cost per averted dose of removing additional radionuclides

22 could be significantly lower than calculated in the cost-benefit analysis).

23

24 If a detailed cost-benefit analysis is presented, ensure that the methods and values used

25 (e.g., discounting methods and discount rates) are appropriate. A reviewer may

26 compare the methods and values used with NRC guidance such as NUREG-1757

27 (NRC, 2003b, Vol. 2, Appendix N), if appropriate. Appropriate values for use in waste

28 determinations may be different from the values recommended in guidance applicable to

29 other types of sites (e.g., the period of performance).

30

31 Determine whether the applicability of costs and benefits have been accounted for

32 appropriately. For example, if a technology must be developed to remove a component

33 from a particular waste stream (e.g., the removal of zeolite from a tank, or the removal of

34 technetium from salt waste), it may not be appropriate to attribute the entire cost of

35 technology development only to the proposed waste management activity if other

36 relevant benefits of the new technology (e.g., removal of zeolite from other tanks or

37 removal of technetium from other salt waste streams) are not included in the analysis.

38

39 If a detailed cost-benefit analysis is presented, determine whether the analysis includes

40 relevant life-cycle costs, including variable costs (e.g., labor) and fixed costs (capital

41 equipment). Verify that estimated costs and benefits are expressed in monetary terms

42 where possible and expressed in constant dollars from the most recent year for which

43 adjustment data are available.

44

45 If a detailed cost-benefit analysis is presented and if life-cycle costs are to be distributed

46 over time, verify that the cost-benefit analysis has used adequate discounting methods

47 such as those described in Office of Management and Budget (Office of Management

48 and Budget 2003, Circular A-4;1992, Circular A-94).

49

3-20
1 If a detailed cost-benefit analysis is presented, determine whether the parameters used

2 to quantify costs and benefits (e.g., transportation risks) are consistent with parameters

3 presented in other NRC or OMB guidance [e.g., Table N.2 of NRC's guidance for

4 License Termination (NRC, 2003b)]. If parameter values are not consistent with values

5 provided in other NRC or OMB guidance and the parameters significantly affect the cost6 benefit analysis results, determine whether an adequate basis has been provided to

7 justify the use of alternate values.

8

9 0 Verify that the timeframe(s) considered in the cost-benefit analysis is appropriate to the

10 alternative waste management strategies and different removal technologies considered

11 and include both short-term and long-term impacts.

12

13 - If DOE cites schedule impacts as a cost of additional radionuclide removal, determine

14 the effect of the schedule impacts on the estimated cost or predicted doses to

15 individuals (workers or members of the public).

16

17 - Evaluate whether additional protective measures could be taken to reduce worker

18 exposure if radiological risks to workers are cited as a reason why additional

19 radionuclide removal is impractical. If possible, determine whether taking additional

20 protective measures to reduce worker exposure would contribute significantly to the cost

21 of the proposed radionuclide removal activities.

22

23 To the extent practical, compare the predicted costs and benefits of additional

24 radionuclide removal to the range of costs per averted dose DOE has incurred to

25 perform similar removal activities (e.g., the costs of previous efforts to remove

26 radionuclides from the same tank or the costs to remove a similar type of waste from

27 another tank).

28

29 3.5 Concentration Limits

30

31 Waste classification is a process used to ensure that waste is properly managed (e.g., LLW

32 disposal in the near surface, HLW disposal in a geologic repository) to protect public health and

33 safety. As discussed in Section 2.4.4, the NDAA, DOE Order 435.1 (DOE, 2001), and the West

34 Valley Policy Statement (NRC, 2002) have different requirements regarding the classification of

35 incidental waste according to the waste classifications described in 10 CFR 61.55. Essentially,

36 the NDAA requires waste classification according to NRC's classification system, DOE

37 Order 435.1 requires classification according to NRC's classification system or an alternate

38 DOE-approved system, and the West Valley Policy Statement does not address waste

39 classification with respect to incidental waste. Refer to Section 2.3 for the West Valley

40 WIR criteria.

41

42 The risk from the near-surface disposal of radioactive waste is not just a function of

43 concentration, but also the volume of waste and its accessibility. The potentially unique

44 characteristics of incidental waste (e.g., depth of the waste, accessibility to intruders,

45 radiological characteristics, spatial distribution) have been considered in the development of

46 this guidance.

47

3-21
1 3.5.1 Areas of Review

2

3 To evaluate compliance with the applicable criteria of the NDAA and DOE Order 435.1,

4 reviewers should assess DOE's classification of incidental waste according to the provisions of

5 10 CFR 61.55. Because NRC's waste classification system is based on radionuclide

6 concentrations, radionuclide concentrations should be reviewed as described in Section 3.1.

7 The concentration averaging provision of 10 CFR 61.55(a)(8) is applicable to the determination

8 of the class of waste that has been mixed with or encapsulated within stabilizing material

9 (e.g., residual tank waste stabilized with grout) or has otherwise been disposed of.

10 Section 3.5.1.1 guides reviewers evaluating the concentration averaging provision of

11 10 CFR 61.55(a)(8) as it applies to incidental waste classification. Section 3.5.1.2 addresses

12 the consultation requirements of the NDAA that are related to waste classification. The use of

13 stabilizing material to protect inadvertent intruders is discussed in Section 5, and the use of

14 stabilizing material to enhance site stability is discussed in Section 7.

15

16 3.5.1.1 Concentration Averaging

17

18 The guidance for concentration averaging in this document does not replace the guidance

19 contained in the branch technical position (BTP) on concentration averaging and encapsulation

20 (NRC, 1995b) for waste classification for the commercial disposal of LLW. The guidance is not

21 intended to address all unique situations at DOE sites. However, this guidance is generally

22 applicable to the following scenarios:

23

24 - Underground waste storage tanks including waste heels, cooling coils, and residual

25 waste adhering to walls and other surfaces,

26

27 - Infrastructure used to support underground waste storage tanks such as transfer lines,

28 transfer pumps, and diversion boxes,

29

30 - Waste removed from tanks that is processed or treated for disposal in a near surface

31 disposal facility, and

32

33 - Other scenarios relating to waste determinations proposed by the DOE and accepted by

34 the NRC.

35

36 Although the concentration averaging BTP was not written to address residual contamination of

37 underground or buried structures or systems, the fundamental principles of waste classification

38 contained within the BTP apply to these systems. In addition, the fundamental principles

39 supporting the development of the waste classification system of 10 CFR Part 61 also apply to

40 waste determinations. This concentration averaging guidance clarifies the fundamental

41 principles presented in the BTP and provides specific examples that may be pertinent to DOE

42 waste determinations. The acceptable concentration averaging methods to classify waste for

43 waste determinations are based on the following fundamental principles introduced in the BTP

44 and in the analysis supporting the development of Part 61:

45

46 • Extreme quantities of uncontaminated materials should not be averaged with residual

47 contamination solely for the purpose of waste classification.

48

3-22
1 Mixtures of residual waste and materials can use a volume-! or mass-based average

2 concentration if it can be demonstrated that the mixture is reasonably well-mixed. The

3 type of averaging (volume- or mass-based) should be consistent with the units of

4 concentration specified for each radionuclide in Tables 1 and 2 of 10 CFR 61.55.

5

6 * Credit can be taken for stabilizing materials added for the purpose of immobilizing the

7 waste (not for stabilizing the contaminated structure) even if it cannot be demonstrated

8 that the waste and stabilizing materials are reasonably well mixed, when the

9 radionuclide concentrations are likely to approach uniformity in the context of applicable

10 intruder scenarios.

11

12 * Waste classification can use a risk-informed approach that calculates waste

13 classification based on the unique characteristics of a specific site (e.g., depth to waste).

14 The intruder scenarios used for waste classification should be conservative and

15 consistent with those discussed in Section 3.5 of this guidance document.

16

17 * Other provisions for the classification of residual waste may be acceptable if, after

18 evaluation of the specific characteristics of the waste, disposal site and method of

19 disposal, the performance objectives in 10 CER Part 61, Subpart C can be demonstrated

20 with reasonable assurance.

21

22 * Regardless of the averaging that is performed for waste classification purposes, the

23 performance assessment or other approach used to demonstrate compliance with the

24 performance objectives of 10 CFR Part 61, Subpart C must consider the actual

25 distribution of residual contamination in the system when estimating release rates to the

26 environment and exposure rates to onsite (inadvertent intruders) and offsite public

27 receptors. Conservative assumptions regarding the distribution of contamination

28 are appropriate.

29

30 The purpose of these principles is to prevent arbitrary or incorrect classification of materials that

31 may result in near-surface disposal of materials that are not suitable for near-surface disposal.

32 The potentially unique characteristics of incidental waste (e.g., depth of the waste, accessibility

33 to intruders, radiological characteristics, spatial distribution) have been considered in the

34 development of this guidance. Appropriate concentration averaging may indicate that waste

35 exceeds Class C concentration limits. Waste that exceeds Class C concentration limits may be

36 suitable for near-surface disposal, but the evaluation of the suitability must involve independent

37 analysis such as would be performed by the NRC under 10 CFR 61.58. NRC staff would

38 evaluate the safety of the near-surface disposal of waste that exceeds Class C concentration

39 limits on a case-by-case basis. Waste concentration is, in some cases, only one of many

40 factors that can influence risk. Waste that is greater than Class C may be determined to be

41 incidental waste and may be safely managed with near-surface disposal if it can be

42 demonstrated that the performance objectives of 10 CFR Part 61, Subpart C, are satisfied.

43 Conversely, waste may be determined to be less than Class C;- however, the waste may be

44 inappropriate for near-surface disposal because the performance objective of 10 CFR 61.41

45 cannot be satisfied. The methods described in the three categories that follow can be used to

46 determine the waste classification of waste residuals.

47

48 This guidance presents three categories of calculations (Categories 1, 2, and 3) to determine

49 waste classification for the concentrations of radionuclides in waste. The first pertains to cases

3-23
1 in which the waste can be mixed and is fairly homogeneous. The second pertains to cases in

2 which the waste cannot be well mixed and is stabilized in place to satisfy the requirements of

3 10 CFR 61.56. The third category is a risk-informed approach developed for incidental waste to

4 provide flexibility in waste classification calculations, recognizing the differences between the

5 disposal of incidental waste and commercial LLW and recognizing site-specific conditions.

6 Category 1 is the simplest approach, while Categories 2 and 3 account for more unique site

7 information but also require more effort to apply.

8

9 As the first principle indicates, extreme measures should not be taken when performing

10 concentration averaging to determine waste classification. The extremity of a measure is

11 relative to the particular averaging approach applied (i.e., Category 1, 2, or 3). The averaging

12 approaches are discussed in this guidance. For Category 1, extreme measures may include but

13 are not limited to (1) averaging assumptions that are inconsistent with the physical distribution

14 of radionuclides over the averaging volume or mass and (2) deliberate blending of lower

15 concentration waste streams with high activity waste streams solely to achieve waste

16 classification objectives, although blending may be needed for waste management purposes.

17 For Category 2, extreme measures may include but are not limited to (1) averaging over

18 stabilizing material volume or masses that are not needed to stabilize the waste per the

19 10 CFR 61.56 stability requirements and (2) averaging over stabilizing material volume or

20 masses that are not homogeneous from the context of the intruder scenarios.

21

22 Other provisions may be used for representing the distribution of radionuclides in waste and the

23 disposal system in the performance assessment calculations to determine the suitability of

24 near-surface disposal according to 10 CFR 61.58, but these other provisions do not pertain to

25 the determination of whether a waste is Class A, Class B, Class C, or greater than Class C as

26 defined in 10 CFR 61.55.

27

28 Cateaory 1--Physical Homogeneity

29

30 In general, waste will have been processed to the maximum extent practical and will have been

31 stabilized so that there is reasonable assurance that the performance objectives of

32 10 CFR Part 61, Subpart C, can be achieved. The concentrations of radionuclides in the waste

33 used to estimate waste classification can be based on the average concentration calculated

34 from the total volume or mass of the waste and processing or stabilizing materials if the

35 materials are reasonably well mixed. The type of averaging (volume- or mass-based) should be

36 consistent with the units of concentration specified for each radionuclide in Tables 1 and 2 of

37 10 CFR 61.55. The weight or volume of the container should not be included in the calculation

38 of average concentrations. The primary consideration for application of a Category 1 approach

39 is whether the distribution of radionuclides within the final wasteform is reasonably

40 homogeneous. Technical basis should be provided (e.g., sampling results, engineering

41 experience, operational constraints) to demonstrate that the waste is reasonably well mixed.

42 The preferred method to demonstrate homogeneity would be to provide a statistical measure

43 (e.g., coefficient of variation) of the variability of concentration within the waste, although this

44 may not always be practical. For homogeneous mixtures, the classification of waste residuals

45 may be based on total volume or mass of the final wasteform. If additional averaging (e.g., as in,

46 the examples in Category 2) is not applied, waste with radionuclide concentrations after mixing

47 that are greater than the values provided in Tables 1 and 2 of 10 CFR 61.55 would be

48 considered to be greater than Class C waste.

49

3-24
1 Mixing within waste or of waste with stabilizing materials may be needed for a variety of

2 reasons. Mixing of waste and stabilizing materials may help to reduce release rates to achieve

3 performance objectives. With respect to the principles of the BTP, mixing with excessive

4 amounts of stabilizing materials solely to reduce the waste concentrations to alter waste

5 classification should not be performed. In most cases, the ratio of the unstabilized to stabilized

6 radionuclide concentrations would not be significantly greater than a factor of 10 for waste

7 classification purposes. For unstabilized waste that cannot be selectively treated or removed,

8 mixing (within waste, not between waste streams) to facilitate homogenization of radionuclide

9 concentrations is appropriate. For example, mixing may be used to reduce the variability in

10 concentrations within a layer of tank waste that cannot be removed for further treatment.

11

12 Example 1-1

13

14 Liquid waste is removed from a tank, and additional fluids are added to adjust the chemistry for

15 processing. Cement and fly ash are mixed with the resultant liquid in an industrial mixer to form

16 a grout that is placed in disposal containers. The concentration of radionuclides for determining

17 waste classification is based on the total volume or mass of the final wasteform.

18

19 Example 1-2

20

21 Reducing grout is added to stabilize a tank heel (the residual layer of waste in the bottom of a

22 tank). The waste residuals in the tank are flocculated solids suspended in a liquid phase that

23 can be mobilized with the tank transfer equipment. However, the solids cannot be removed with

24 the existing equipment. The reducing grout has a relatively high viscosity such that the

25 flocculated solid residuals and remaining waste liquids can be mixed with the grout using the

26 transfer equipment prior to setting of the grout. The concentration of radionuclides for waste

27 classification is based on the total volume or mass of the waste and the reducing grout in which

28 the waste is mixed. Additional reducing grout into which little or no waste is mixed should not

29 be included in the total mass or volume used for concentration averaging.

30

31 Category 2-Stabilization to Satisfy 10 CFR 61.56

32

33 Stabilization can limit exposure to an inadvertent intruder because it provides a recognizable

34 and non-dispersible waste. For solidified liquids and solids, Section 3.2 of the BTP provides for

35 the concentration of the radionuclides to be determined based on the volume or weight of the

36 solidified mass, which is defined here to be the amount of material needed to stabilize the

37 liquids or dispersible solids to satisfy 10 CFR 61.56. Liquid waste must be solidified or

38 packaged in sufficient absorbent material to absorb twice the volume of the liquid

39 (10 CFR 61.56). However, the stabilizing material is not to be interpreted as bulk material

40 added to fill void space in the storage system or to fill void space in the equipment containing

41 the waste. Stabilization is determined with respect to the waste and not the entire disposal

42 system or unit. While stabilization of the entire disposal unit (e.g., a tank) may be necessary to

43 meet the performance objectives, it generally would not be needed to make the residual waste

44 recognizable and nondispersible.

45

46 Waste concentrations are calculated based on the volume or mass of material needed to be

47 added to liquids or dispersible solids to solidify or encapsulate them. The concentration of the

48 stabilized waste (waste plus stabilizing material) should generally be within a factor of 10 of the

49 concentration of the unstabilized waste on either a mass or volume basis. The factor of 10 is

3-25
1 based on the amount of material typically needed to stabilize waste in a solidified wasteform,

2 consistent with the principle that concentration averaging is appropriate when wastes require

3 stabilization. Most commonly envisioned stabilization techniques use cementitious materials,

4 and most cementitious wasteforms can readily achieve a minimum of 10 mass percent waste

5 loading. Additional stabilizing materials may be needed for the system or structures however,

6 they would not generally be needed for waste stabilization. Therefore, it would not be

7 consistent with the principles of classification for this category to include those materials in the

8 concentration averaging calculations. 'A more risk-informed approach that considers site9 specific conditions is found under Category 3.

10

11 For thin layers of contamination on surfaces, especially vertical surfaces, the average

12 concentration may be based on the volume or mass of a layer of stabilizing material that would

13 be needed to stabilize the waste, as discussed previously. This does not mean that averaging

14 can be performed over all materials added to fill void space in the structure. This approach is

15 justified because the concentrations would be expected to approach homogeneity with respect

16 to the intruder scenarios, and the main justification for the classification system is to protect the

17 inadvertent intruder. The concentration values found in Tables 1 and 2 of 10 CFR 61.55 were

18 derived assuming the total volume of waste exhumed by the intruder is at those concentrations

19 (although dilution of waste was considered after the waste was exhumed) therefore, a thin layer

20 of more concentrated material averaged over the same exhumed volume would achieve a

21 similar level of protection. Specific averaging volumes are not provided for this category

22 because of the site-specific nature of the waste and site-specific considerations for intruder

23 scenarios. The type of averaging (volume- or mass-based) should be consistent with the units

24 of concentration specified for each radionuclide in Tables 1 and 2 of 10 CFR 61.55. If a

25 Category 2 approach is not flexible enough for a particular waste determination, then a

26 Category 3 approach should be considered.

27

28 Example 2-1

29

30 A tank contains a heel that is 2.5 cm [1 in] thick and is composed of liquids and dispersible

31 solids. A 20-cm [8-in]-thick layer of reducing grout is needed to stabilize the waste, and an

32 additional 300 cm [120 in] of high-strength grout is added to fill void space andto provide an

33 intruder barrier. The concentration of radionuclides would be calculated by averaging over the

34 20-cm [8-in]-thick layer of reducing grout. Use of a 20-cm [8-in] layer of reducing grout in the

35 concentration calculation is based on the amount of grout that would be needed to stabilize the

36 waste if it could be removed from the tank and made into a stable wasteform. The

37 concentration of the stabilized waste (waste plus stabilizing material) would generally be within

38 a factor of 10 of the concentration in the unstabilized waste on either a mass or volume basis.

39

40 Example 2-2

41

42 The walls of a waste storage tank have a thin layer (0.1 cm [0. 04 in]) of residual contamination

43 that is not easily removed. The tank walls are 1 cm [0.4 in] thick, and the tank is contained

44 within a 0.5-m [1.6-ft]-thick vault. The contamination is not easily dispersed into the

45 environment and is located underground. Closure of the storage tank will involve filling the tank

46 and all void space with grout. The concentration of the waste for waste classification is

47 calculated based on the thickness of the contamination and a 1-cm [0.4-in]-thick layer of

48 stabilizing grout. Use of a 1-cm [0.4-in] layer of grout in the concentration calculation is based

49 on the assumption that formation of a stable wasteform is accomplished by incorporating the

3-26
1 0. 1-cm [0.04-in] layer of residual waste into a cementitious wasteform at a mass loading of

2 approximately 10 percent. The concentrations of the thin layer would be reduced by a factor of

3 10 for estimating waste classification if a volume basis were used.

4

5 Category 3-Site-Specific Averaging

6

7 This approach, accounting for site-specific conditions, may be used to determine whether

8 incidental waste is greater than Class C. A description of the calculations used to develop the

9 example generic averaging expressions found in this section is provided in Appendix B.

10

11 The risk from the near-surface disposal of radioactive waste is not just a function of

12 concentration, but also volume and accessibility. The Category 3 approach to concentration

13 averaging attempts to account for the volume of waste, concentration of waste, and accessibility

14 of the waste. Note that a number of factors (including those listed previously) specific to

15 commercial LLW disposal were considered in the Part 61 analysis to develop waste

16 classification concentration limits (NRC, 1981). Some of those factors may not apply to a

17 specific incidental waste site, or more recent information may suggest taking a different

18 approach. It is not as simple as applying a new dilution factor for an incidental waste scenario

19 and modifying the 10 CFR 61.55 waste classification concentration limits directly.

20

21 Although accessibility of the waste (e.g., depth and intruder barriers) is considered for

22 concentration averaging applied to incidental waste, managing of intruder risk with complex,

23 engineered facilities to prohibit access of the waste for very long periods of time (more than

24 500 years) is not likely to be practical. Thus, there are practical limits as to what types of waste

25 are suitable for near-surface disposal. Waste classification is a process used to ensure that

26 waste is properly managed (e.g., LLW disposal in the near surface, HLW disposal in a geologic

27 repository) to protect public health and safety.

28

29 Although multiple scenarios were considered, the limiting intruder scenario that was used (in

30 deriving the concentration limits for waste classification found in Table 1 and Table 2 of

31 10 CFR 61.55) was an intruder construction scenario (NRC, 1981). This scenario involved the

32 excavation of a foundation for a house. Approximately 232 m3 [8,190 ft 3] of waste was

33 assumed to be exhumed, and the excavation was assumed to be to a depth of 3 m [10 ft]. This

34 scenario was appropriate for the commercial disposal of LLW, which at the time was envisioned

35 to be in shallow trenches covering a large area (e.g., thousands of square meters). The

36 commercial disposal of Class C waste is required to have the top of the waste a minimum of

37 5 m [16 ft] below the top surface of the cover, or it must be disposed of with intruder barriers that

38 are designed to protect against an inadvertent intrusion into the waste for at least 500 years.

39 Tables 1 and 2 were developed so that waste generators and disposers could safely manage

40 and dispose of waste of various concentrations and compositions. The Table 1 and 2 values

41 were developed making certain assumptions regarding the exposure scenarios and radiological

42 distribution of waste that a commercial LLW facility would likely receive, and the analysis used

43 the most current information on dosimetry and disposal technology (NRC, 1981). The

44 underlying assumption of the values in Tables 1 and 2 of 10 CFR 61.55 is that the concentration

45 limits and disposal requirements ensure that an inadvertent intruder would not receive a dose

46 exceeding an equivalent of 5 mSv [500 mrem] to the whole body. For example, an intruder

47 analysis assuming an excavation scenario and Class C waste disposed of at a depth less than

48 5,m [16 ft] without an intruder barrier results in a dose substantially in excess of 5 mSv

49 [500 mrem].

3-27
1

2 Incidental waste disposal may be similar to commercial disposal of LLW in some aspects and

3 may be substantially different in other aspects. A Category 3 approach allows a reviewer to

4 account for these differences. Figure 3-1 summarizes the 10 CFR Part 61 analysis for the

5 excavation scenario and a hypothetical disposal configuration for incidental waste in a tank.

6 Whereas the excavation scenario is appropriate for relatively shallow waste, the excavation

7 scenario is not appropriate for deeper waste that is significantly below the excavation depth. In

8 these cases, a drilling scenario may be more appropriate.

9

10 The relationship between waste concentration and disposal depth was recognized in the Draft

11 Environmental Impact Statement for 10 CFR Part 61 and updates to the impacts analysis (NRC,

12 1981, 1986). Consideration was given to excavations that may be deeper than 5 meters, such

13 as for an industrial building. A subjective probability of 10 percent was assigned to the

14 likelihood that a deeper excavation would be inadvertently constructed at a LLW facility resulting

15 in disruption of the waste. Consideration was also given to robust intruder barriers and the

16 impacts they may have on safety. As noted above, robust intruder barriers are required for the

17 shallow commercial disposal of Class C waste. A robust intruder barrier was assumed to delay

18 an intrusion event for up to 500 years. However, technological limitations and uncertainties of

19 barrier performance were recognized such that even in the case of a "hot waste facility" (an

20 engineered facility that would be constructed of high-strength reinforced concrete to contain

21 high activity waste such as sealed sources), credit for the concrete as an intruder barrier for

22 time periods exceeding 1,000 years was not believed to be reasonable. For near-surface

23 disposal there were considered to be technological limitations to preventing intrusion for very

24 long periods of time.

25

26 The calculations to develop the Table 1 and Table 2 concentration limits in 10 CFR 61.55 to

27 define Class A, B, and C waste were based on a number of important assumptions and

28 considerations. Although a requirement is provided that Class C waste must either be

29 commercially disposed of at depths greater than 5 m [16 ft] or have a robust intruder barrier

30 that lasts for 500 years, the calculations assumed an excavation scenario for the intruder. The

31 calculations also assumed that a large volume fraction of the waste at a commercial LLW

32 facility would not be Class C waste. Therefore, credit for dilution or mixing of different

33 concentrations of waste was provided. The current internal dosimetry at the time, Report 2 of

34 the International Commission on Radiological Protection (ICRP-2) (ICRP, 1959), was used in

35 deterministic analyses.

36

37 Incidental waste may include many different types of waste in a variety of disposal

38 configurations. For example, incidental waste may include residual waste in piping that is near

39 the land surface and does not have a robust intruder barrier. Residual waste in a tank that is

40 much deeper than 5 m [16 ft] from the land surface and does have a robust intruder barrier may

41 also be considered to be incidental waste. Guidance for waste classification for incidental

42 waste needs to be flexible to handle these different aspects.-

43

44 The conceptual approach and example Category 3 concentration averaging expressions were

45 developed using a risk-informed approach to account for (1) depth of waste, (2) intruder

46 barriers, (3) current dosimetry, and (4) propagation of uncertainty into the concentration limits.

47 The example averaging expressions represent a conversion from the analyses used to support

48 the development of Tables 1 and 2 of 10 CFR 61.55 [Figure 3-1(a)] and calculations more

49 appropriate for incidental waste [Figure 3-1(b)]. Different approaches can be applied

3-28
1

Incidental Waste Intruder Scenario for Tank Residuals

Part 61 Intruder Construction Scenario, or Ancillary Equpiment

Excavation

'Piping

Grout/concrete

Waste

-- Well

r•3

CD

Groundwater --

Deterministic calculations.

Dosimetry - ICRP 2

Generic parameter sets " ,. " • ... (a ) . . - .. , .,

Probabilistic or deterýministic calculations

Dosimetry - ICRP 26 and 30

Site-specific parameter values or distributions

(b)

2

3

4

Figure 3-1. Comparison of Key Assumptions of (a) the Intruder Excavation Scenario for Part 61 and (b) Intruder

Scenarios for Tank Residual Waste
1 depending on the depth of the waste and whether a robust intruder barrier has been installed.

2 Four different example averaging expressions have been developed to provide flexible

3 benchmarks for the staff to use when reviewing Category 3 concentration averaging

4 approaches. It is expected that DOE will develop its own calculations to support a

5 Category 3 approach.

6

7 Depth to waste and the use of a robust intruder barrier are two primary conditions that

8 determine the type of intruder scenario most appropriate to estimate waste classification. The

9 burial depth condition is evaluated considering cover thicknesses projected over the analysis

10 period (e.g., processes that may decrease the cover thickness over time should be considered).

11 A robust intruder barrier is defined as one that will prevent intrusion into the waste for

12 500 years. Regardless of the approach that applies, the waste should be immobilized in a solid

13 physical form such that it would be recognizable as being non-native materials and it would not

14 be easily dispersed into the environment (consistent with 10 CFR 61.56). The sum of fractions

15 approach, consistent with the description provided in 10 CFR 61.55, should be applied for waste

16 containing multiple radionuclides.

17

18 The review of site-specific averaging for waste classification should apply to the following

19 conditions and assumptions:

20

21 * If the waste is buried at a minimum depth of les's than 5 mn [16 ft] and a robust intruder

22 barrier is not installed, then an excavation scenario should be assumed and applied at

23 the time of maximum dose (typically 100 years) following closure of the system. Both

24 acute (e.g., the receptor who builds the residence) and chronic (e.g., the receptor who

25 lives in the residence after construction) exposure of receptors should be evaluated and

26 the more limiting receptor type should be used to define waste classification.

27

28 * If the waste is buried at a minimum depth of less than 5 m [16 ft] and a robust intruder

29 barrier is installed, then an excavation scenario should be assumed and applied at the

30 time of maximum dose (typically 500 years) following closure of the system. A robust

31 intruder barrier is defined as one that will last 500 years. Both acute (e.g., the receptor

32 who builds the residence) and chronic (e.g., the receptor who lives in the residence after

33 construction) exposure of receptors should be evaluated, and the more limiting receptor

34 should be used to define waste classification.

35

36 If the waste is buried at a minimum depth of more than 5 mn [16 ft] and a robust intruder

37 barrier is not installed, then a drilling scenario should be assumed and applied at the

38 time of maximum dose (typically 100 years) following closure of the system. Both acute

39 (e.g., the receptor who constructs the well) and chronic (e.g., the receptor who lives in a

40 residence located where the cuttings or material from construction of the well are

41 dispositioned) exposure of receptors should be evaluated, and the more limiting type

42 should be used to define waste classification.

43

44 * If the waste is buried at a minimum depth of more than 5 mn [16 ft] and a robust intruder

45 barrier is installed, then a drilling scenario should be assumed and applied at the time of

46 maximum dose (typically 500 years) following closure of the system. Both acute

47 (e.g., the receptor who constructs the well) and chronic (e.g., the receptor who lives in a

48 residence located where the cuttings or material from construction of the well are

3-30
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dispositioned) exposures of receptors should be evaluated, and the more limiting type

should be used to define waste classification.

If a scenario other than those listed is more limiting and is reasonably likely to occur

after closure, then it should be used to determine waste classification with a site-specific

averaging approach.

Staff should verify that DOE applied these assumptions when performing site-specific

concentration averaging. Pathways considered and parameters used for each scenario should

be provided. Staff should verify that scenarios selected are consistent with Table 3-2. For

waste classification purposes, one of the four scenarios from Table 3-2 or a more limiting

scenario, must be selected if a Category 3 approach is used. The scenarios in Table 3-2 are

believed to be the limiting scenarios out of the possible combinations, as waste access time and

waste disruption process are dictated by the depth of waste and the presence or absence of a

robust intruder barrier. The waste classification system is, in part, designed to establish a

protective upper limit to the concentration (and quantity) of material that may be suitable for

near-surface disposal. Quantity of waste can be either explicitly represented in the analysis or

implicitly represented with assumptions about the disposal facility type and configuration. Use

of reasonably conservative scenarios for waste classification purposes ensures that radioactive

waste is described in a proper risk context, radioactive waste is disposed of with appropriate

controls, and classification calculations are reviewed with an appropriate level of effort to ensure

public health and safety will be protected. Because the Category 3 approach to concentration

Table 3-2. Assumed Conditions for the Four Scenarios Used to Develop

Averaging Expressions

Typical Waste Waste Disruption

Scenario Access Time* (yr) Process Receptor Type

Shallow waste, 100 Residential Construction

no intruder Construction worker-acute

barrier or

Resident-chronic

Shallow waste, 500 Residential Construction

intruder barrier Construction worker-acute

or

Resident-chronic

Deep waste, no 100 Well Drilling Well driller-acute

intruder barrier or

Resident-chronic

Deep waste, 500 Well Drilling Well driller-acute

intruder barrier or

Resident-chronic

*The maximum dose may not occur at the earliest possible waste access time, depending on the decay of parent

and in-growth of daughter radionuclides. For fission products, peak dose will likely occur at the earliest waste

access time for a given scenario.

3-31
1 averaging and thus waste classification involves a site-specific intruder analysis, it is unlikely

2 that waste estimated to be greater than Class C waste using a Category 3 approach would

3 satisfy the 10 CFR 61.42 performance objective.

4

5 Note that a number of factors specific to commercial LLW disposal were considered in the

6 10 CFR Part 61 analysis to develop waste classification concentration limits (NRC, 1981).

7 Some of those factors may not apply to a specific incidental waste site, or more recent

8 information may suggest a different approach should be taken. Adapting the waste

9 classification approach considered during the development of 10 CFR Part 61 to incidental

10 waste is not as simple as applying a new dilution factor for an incidental waste scenario and

11 modifying the 10 CFR 61.55 waste classification concentration limits directly.

12

13 Example averaging expressions were developed to provide a benchmark for staff to use to

14 review site-specific averaging for waste classification under a variety of scenarios. The example

15 averaging expressions (developed assuming a generic site and receptor characteristics) were

16 developed with moderately conservative assumptions to ensure adequate protection under most

17 conditions. For example, as explained in Appendix B, the limiting short-lived and the limiting

18 long-lived radionuclides were used to develop the constants in the example averaging

19 expressions that then would be applied to all radionuclides of that type (i.e., short-lived or long20 lived). However, site-specific conditions, particularly for water-dependent pathways, can affect

21 the amount of averaging that may be appropriate at a site. Site-specific variability can result in

22 an order of magnitude or more range for the constants in the example averaging expressions.

23 Therefore, even if the resultant site-specific averaging applied for incidental waste is consistent

24 with that estimated by staff with the relevant example averaging expression found below, the

25 averaging analysis should be carefully reviewed. The averaging expressions (benchmarks) are

26 not to be used as the basis for site-specific averaging for waste classification. They are for staff

27 use to determine when site-specific concentration averaging calculations DOE performed may

28 require additional staff review effort. A description of the development of the benchmarks are

29 found in Appendix B.

30

31 If waste is buried at depths greater than 5 m 116 ft' and a robust intruder barrier

32 is installed:

33

34 For Table 1 or Table 2 radionuclides, individual radionuclidecontribution to the sum of fractions

35 may be estimated with the following equation (drilling is assumed to occur at 500 years)

36

WC, _ (AWaste thickness(3

3Table•Value,) * ri depth .)7

38 where

39

40 i = radionuclide index

41 RC= radionuclide classification factor (unitless)

42 WC = concentration in the waste for radionuclide i in units consistent

43 with the appropriate Table value in 10 CFR 61.55

44 TableValue. = Class C concentration limit in the appropriate Table of

45 10 CFR 61.55 for radionuclide i

46 Wastethickness = thickness of the waste (m)

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40

41

42

43

44

Drill_depth = depth an intruder would likely install a well to in order to recover

resources (m)

RCj represents the contribution to the Table 1 or Table 2 sum of fractions [see

10 CFR 61.55 (a)(7)] for each radionuclide. The derivation of the constant, 7, in the

expression is discussed in Appendix B. In most cases, the resource being recovered would

be water; however, exploitation of other natural resources should be considered. The

long-lived radionuclides are only moderately more limiting than the short-lived radionuclides for

this example, therefore the same averaging can be applied to each group of radionuclides.

If waste is buried at depths greater than 5 m r16 ft1 and a robust intruder barrier is

not installed:

For Table 1 radionuclides, individual radionuclide contribution to the sum of fractions may be

estimated with the following equation (drilling is assumed to occur at 100 years)

RC, T= - 1WC .* (Waste; thickness 7 kTableli) ,Drill_ depth (3.5-2)

where

i

RCj

WCi

Tablel1

Waste thickness

Drilldepth

= radionuclide index

= radionuclide classification-factor (unitless)

= concentration in the waste for radionuclide i (in Ci/m3 or nCi/g)

= concentrations in Table 1 of 10 CFR 61.55 for radionuclide i (in

Ci/m 3 or nCi/g).

= thickness of the waste (m)

= depth an intruder would likely install a well to in order to recover

resources (m)

The RCO represents the contribution to the Table 1 sum of fractions [see 10 CFR 61.55 (a)(7)]

for each radionuclide. The derivation of the constant, 7, in the expression is discussed in

Appendix B.

For Table 2 radionuclides, individual radionuclide contribution to the sum of fractions may be

estimated with the following equation

RC, = ,Table2_Column3j) T e WCj * r.Waste- , Drill_ thickness depth 2 17,000 (3.5-3)

where

i

RCj

WCt

Table2_Column3,

Waste thickness

Drilldepth

= radionuclide index

= radionuclide classification factor (unitless)

= concentration in the waste for radionuclide i (Ci/m 3

)

= concentrations in Column 3 of Table 2 of 10 CFR 61.55 for

radionuclide i (Ci/m 3

)

= thickness of the waste (m)

= depth an intruder would likely install a well to in order to recover

resources (m)

3-33
1

2

3

4

5

6

7

8

The RC, represents the contribution to the Table 2 sum of fractions for each radionuclide. The

derivation of the constant, 17,000, in the expression is discussed in Appendix B.

If waste is buried at depths less than 5 m [16 ft] and a robust intruder barrier is installed:

For all radionuclides, individual radionuclide contribution to the sum of fractions may be

estimated with the following equation (excavation is assumed to occur at 500 years)

RCTable Va=ue i ( Waste volum (3.5-4)

9 where

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

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33

34

35

36

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38

39

40

41

i

RC1

WCi

TableValue.

Waste-volume

= radionuclide index

= radionuclide classification factor (unitless)

= concentration in the waste for radionuclide I

= Class C concentration limit in the appropriate table of

10 CFR 61.55 for radionuclide i

volume of waste (in units of M3

) in an excavation volume of 600 m3

The values for WCj and TableValue, should be expressed in the same units. The RC1

represents the contribution to the sum of fractions for each radionuclide. The derivation of the

constant, 3, in the expression above is discussed in Appendix B. When Wastevolume is

expressed in m3, the result of expression Eq. (3.5-4) is unitless.

The waste classification should also be estimated using the approach for waste buried at

depths greater than 5 m [16 ft] with a robust intruder barrier installed, and the more limiting

value should be used.

If waste is buried at depths less than 5 m [1`6 ft1 and a robust intruder barrier is

not installed:

For Table I radionuclides, individual radionuclide contribution to the sum of fractions may be

estimated with the following equation (excavation is assumed to occur at 100 years)

RC 1 = WCe - • Waste-volume

R (=TablelValue;) 3m'=- (3.5-5)

where

RC1

WC!

TablelValue.

Wastevolume

= radionuclide index

- radionuclide classification factor (unitless)

- concentration in the waste for radionuclide i = Class C concentration limit in Table 1 of 10 CFR 61.55 for

radionuclide i

= volume of waste (in units of M3 ) in an excavation volume of 600 M3

3-34
1 The values for WCj and TablelValue, should be expressed in the same units. The RC,

2 represents the contribution to the sum of fractions for each radionuclide. The derivation of the

3 constant, 3, in the expression above is discussed in Appendix B.

4

5 For Table 2 radionuclides, individual radionuclide contribution to the sum of fractions may be

6 estimated with the following equation

7 RC, T,- WC *Wastevolume*1,000m-3 (3.5-6) kTable2_Value,J

8 where

9

10 i = radionuclide index

11 RCi = radionuclide classification factor (unitless)

12 WC, = concentration in the waste for radionuclide i

13 Table2_Value, = Class C concentration limit in Table 2 of Part 61 for radionuclide i

14 Wastevolume = volume of waste (in units of m3) in an excavation volume of 600 m'

15

16 The values for WCj and Table2_Value, should be expressed in the same units. The RC,

17 represents the contribution to the sum of fractions for each radionuclide. The derivation of the

18 constant, 1,000, in the expression above is discussed in Appendix B.

19

20 The waste classification should also be estimated using the approach for waste buried at depths

21 greater than 5 m [16 ft] without a robust intruder barrier installed, and the more limiting value

22 should be used.

23

24 Example 3-1

25

26 A waste tank contains a 5-cm [2-in] layer of waste after cleaning, and the bottom of the tank is

27 roughly 10 m [33 ft] below the ground surface. Erosion processes are estimated to be negligible

28 for the foreseeable future. The average Np-237 concentration in the waste is 3,000 nCi/g. The

29 depth to the water table is 20 m (66 ft) from the ground surface at the tank location, and a

30 high-strength grout is emplaced in the tank to stabilize the residual waste and provide a robust

31 intruder barrier. Only a single radionuclide is used in this example to illustrate the calculation,

32 the waste in most real world problems would contain numerous radionuclides and would require

33 using a sum of fractions approach be used.

34

35 If the waste classification approach for a commercial LLW facility was used, the residual waste

36 would be greater than Class C because the concentration exceeds 100 nCi/g (Table 1 of

37 10 CFR 61.55). However, DOE applied a Category 3 approach and provided detailed

38 documentation of the waste classification calculations. Waste classification was based on an

39 intruder driller scenario that was assumed to occur at 100 years after facility closure. The waste

40 access time of 100 years was conservatively selected to account for uncertainty in the ability of

41 the robust intruder barrier to limit contact with the waste. DOE estimated the waste class to be

42 less than Class C (sum of fractions = 0.81) in its calculations.

43

44

3-35
1

2

3

Using the appropriate Category 3 expression, the staff calculated the waste classification for

this scenario to be less than Class C

3,0 0 0 nCi

g x 005m x 7 = 0.525 RC237 =, nCi 20m

100 - 2

g

(3.5-7)

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38

39

40

41

42

43

Because the benchmark result is reasonably consistent with the DOE estimate, staff need not

perform independent waste classification calculations and can perform a standard review of the

DOE document.

Other Provisions

10 CFR 61.58 allows the Commission to authorize other provisions to classify and characterize

waste, if after evaluating the specific characteristics of the waste, disposal site, and method of

disposal, it finds reasonable assurance of compliance with the performance objectives in

Subpart C. Demonstration that the performance objectives can be satisfied would involve a

site-specific analysis (e.g., performance assessment). 10 CFR 61.58 was intended to allow the

NRC the flexibility of establishing alternate waste classification schemes when justified by

site-specific conditions and does not affect the generic waste classifications established in

10 CFR 61.55. Thus, if the results of concentration calculations performed in a manner

consistent with the principles and examples described previously in this document indicate that

radionuclide concentrations in the waste exceed Class C limits, then the waste is greater than

Class C waste for waste classification purposes. If it can be demonstrated that the

performance objectives of 10 CFR Part 61 can be satisfied, then the waste would be suitable

for near-surface disposal.

For a performance assessment and inadvertent intruder calculation supporting 10 CFR 61.58,

the waste should be represented as it is physically expected to be present and not be averaged

over the stabilizing and encapsulating materials unless the estimated doses to the public and

inadvertent intruders would be conservative as a result of averaging. Otherwise, every attempt

should be made to represent the expected distribution of activity within the disposal system. If

the 10 CFR Part 61, Subpart C, performance objectives can be met with reasonable assurance,

then the waste is considered to be acceptable for near-surface disposal.

When performing the intruder calculations, it is not appropriate to calculate an average dose

factoring in the likelihood of the occurrence of the scenario. The likelihood of the intruder

scenario occurring is already represented in the higher limit {e.g., 5 mSv/yr [500 mrem/yr]}

applied for inadvertent intruder regulatory analysis.

Example-Other Provisions

A waste heel remains in a waste tank. The waste is well mixed with reducing grout using mixer

pumps. A high-strength grout is placed over the reducing grout to provide a robust intruder

barrier and to limit water contact with the waste. The top of the waste residuals is 10 m [33 ft]

below the ground surface. The waste has a concentration of Tc-99 of 50 Ci/m3.

3-36
1 Using a Category 1 approach the average concentration of Tc-99 in the wasteform is calculated

2 to be 6 Ci/m3 after mixing of the waste and grout; therefore the waste would be classified as

3 being greater than Class C (6 Ci/m3 is above the 3 Ci/m3 limit from Table I of 10 CFR 61.55).

4 DOE states that although the material is greater than Class C, the material is suitable for

5 near-surface disposal because the performance objectives in 10 CFR Part 61, Subpart C, can

6 be satisfied. DOE provides a performance assessment and intruder analysis for NRC staff

7 to review.

8

9 To demonstrate that the performance objectives can be satisfied, an intruder scenario is

10 evaluated in which a well driller places a well through the disposal system. In this case, the

11 acute intruder is exposed to drill cuttings (waste). The average concentration of the waste used

12 in the performance assessment calculations is calculated by assuming mixing over the volume

13 of well cuttings exhumed because the cuttings are expected to be well mixed when spread on

14 the land surface. The limiting dose impact to the intruder (well driller) from Tc-99 is calculated in

15 the intruder analysis to be 0. 057 mSv/yr [57 mrem/yr] to a chronic receptor (a resident who

16 places a garden in the area contaminated by the drill cuttings). The waste is determined to

17 impose an acceptable risk to the inadvertent intruder.

18

19 Because the rate of erosion at the site is relatively high, a second intruder scenario is evaluated

20 in which most of the cover is eroded over the analysis time period. Some cover is expected to

21 remain. The intruder is assumed to construct a home in the area over the tank. Because the

22 direct exposure pathway is the only major contributing pathway for this scenario (the waste is

23 deeper than the excavation depth), the actual waste distribution is used in the performance

24 assessment. Alternatively, the average concentration of waste over the stabilizing materials

25 could have been used in the performance assessment because there would be less shielding

26 for this calculation and the doses would likely be conservative. The cover remaining provides

27 adequate shielding to reduce the dose from direct exposure to Tc-99 to insignificant levels;

28 therefore, the waste is determined to impose an acceptable risk to the inadvertent intruder.

29

30 The dose to a public receptor, who is offsite when institutional controls are in place and at the

31 edge of a buffer zone near the closed tanks after institutional controls end, is evaluated with an

32 all-pathways performance assessment. The performance assessment represents expected

33 degradation of the system over time. The modeling of the source term represents the waste as

34 two zones: one zone of higher hydraulic conductivity and reducing conditions that persist for

35 500 years and one zone of lower hydraulic conductivity and reducing conditions that persist for

36 the entire analysis period (10,000 years). The first zone represents the wasteform located at

37 the periphery of the tank. Because of shrinkage effects or degradation of the grout itself over

38 time from various attack mechanisms, waste in the first zone may be exposed to increased

39 moisture flow and higher rates of oxidation. The second zone represents waste that was

40 immobilized in the center of the tank in the reducing grout. The concentrations of radionuclides

41 in both zones are relatively homogeneous because the waste and grout were well mixed with

42 the mixer pumps. (If the distribution of waste was heterogeneous, then the waste should have

43 been represented in the performance assessment by the expected distribution of contamination

44 within the zones or distributions that could be demonstrated to be conservative with respect to

45 release and exposure modeling. The potential pathways of water to the waste may depend on

46 the discrete features of the system [e.g., cooling coils, shrinkage effects, fractures].) The

47 limiting dose impact to the public receptor from Tc-99 is calculated in the performance

48 assessment to be 0.0 12 mSv/yr [12 mrem/yr] to a chronic receptor (a resident who has a house,

3-37
1 uses groundwater for domestic purposes, and grows produce in a small garden). The waste is

2 determined to impose an acceptable risk to the general population.

3

4 Disposal of the waste satisfies the performance objectives found in of 10 CFR Part 61,

5 Subpart C. After evaluating the specific characteristics of the waste, disposal site, and method

6 of disposal, the Commission finds reasonable assurance of compliance with the performance

7 objectives; therefore, the material is considered to be suitable for near-surface disposal.

8

9 3.5.1.2 Consultation for Disposal Plans for Waste Exceeding Class C

10

11 Waste with concentration limits above the concentration limits for Class C LLW as defined in

12 10 CFR 61.55, although generally unacceptable for near-surface disposal, may be.acceptable

13 for near-surface disposal with special processing or design. The form and disposal methods for

14 this waste must be different and generally more stringent than those specified for Class C waste

15 [see 10 CFR 61.55(a)(2)(iv)]. If DOE determines that the waste exceeds the Class C

16 concentration limits or if DOE is unable to determine whether the Class C limits are exceeded,

17 the NDAA requires that disposal must be pursuant to plans DOE developed in its consultation

18 with the Commission (see Section 2.1).

19

20 The reviewer should take a risk-informed, performance-based approach when evaluating any

21 disposal plans DOE proposed during consultations. A risk-informed, performance-based

22 approach provides DOE with the flexibility to define disposal methods for wastes that do not

23 meet the Class C concentration requirements. In conducting its review, the staff should

24 consider the following aspects of DOE's plans:

25

26 How DOE's disposal plans, with respect to form and disposal methods, are different and,

27 in general, more stringent than plans that would be proposed for disposal of Class C

28 waste; and

29

30 How DOE demonstrates compliance with the performance objectives of 10 CFR Part 61,

31 Subpart C (see Section 2 of this guidance). The review methods in Sections 4-7 of this

32 guidance document can be applied to evaluate performance assessments and facility

33 designs intended to achieve compliance.

34

35 3.5.2 Review Procedures

36

37 The reviewer should evaluate the waste classifications provided in the waste determination

38 using the information in 10 CFR 61.55. Specifically, the reviewer should confirm the

39 following information:

40

41 * The appropriate tables in 10 CFR 61.55 have been used to classify the waste.

42

43 - Uncertainties in concentrations that are used to determine waste classification have

44 been considered appropriately.

45

46 - Classification has been made based on the final wasteform(s).

47

48 - The sum of fractions has been used correctly (10 CFR 61.55), if applicable.

49

3-38
1 *The waste concentration averaging guidance (see Section 3.5.1.1) has been applied

2 appropriately. Specifically, if concentration averaging is applied, the reviewer should

3 confirm the following information:

4

5 - If a Category 1 approach is used, residual waste and other materials are

6 reasonably well mixed, and the type of averaging (volume- or mass-based) is

7 consistent with the units of concentration specified for each radionuclide in

8 Tables 1 and 2 of 10 CFR 61.55.

9

10 - If a Category 2 approach is used, credit is taken only for material needed to

11 stabilize waste rather than to stabilize a disposal facility (e.g., in most cases, the

12 ratio of the unstabilized to stabilized radionuclide concentrations would not be

13 significantly greater than a factor of 10 for waste classification purposes).

14

15 - If a Category 2 approach is used, radionuclide concentrations in waste to which

16 concentration averaging is applied are likely to approach uniformity in the context

17 of applicable intruder scenarios.

18

19 - Different waste streams have been classified separately, if appropriate.

20

21 - If a Category 3 approach is used, site-specific, risk-informed approaches have

22 selected intruder scenarios that are reasonably conservative and consistent with

23 those discussed in Section 3.5.1.1.

24

25 - If a Category 3 approach is used, adequate technical basis has been provided for

26 the performance of intruder barriers for waste classification calculations.

27

28 - If a Category 3 approach is used, the depth to waste is defined based on current

29 and future projected disposal system configurations, and intruder scenarios

30 consistent with the depth to waste have been selected for waste classification

31 calculations.

32

33 - Classification calculations using a Category 3 approach are adequately

34 described and justified. Staff may use the example averaging expressions, found

35 in Section 3.5.1.1 as a review tool. However, the example averaging

36 expressions are not to be used as the basis for classification calculations for the

37 reasons discussed in Section 3.5.1.1.

38

39 - Decay and ingrowth have been included in the classification calculations.

40

41 *In addition, if the waste exceeds Class C concentration limits, the reviewer

42 should ensure that the consultation process described in Section 3.5.1.2 is

43 applied appropriately.

44

45 3.6 References

46

47 Evans, M.S. "A Review of the EMMA Manipulator System with Regard to Waste Retrieval from

48 Hanford Underground Storage Tanks." PIT-MISC-0129. White Paper for the Tanks Focus

49 Area, Office of Science and Technology, DOE. 1997.

3-39
1 Gilbreath, K.D. "Risk Benefit Evaluation of Residual Heel Removal in Tanks 19 and 18."

2 CBU-PIT-2005-00169. Rev. 0. Westinghouse Savannah River Company, Closure Business

3 Unit, Planning Integration and Technology Department. 2005.

4

5 Hatchell, B., et al. "Russian Pulsating Mixer Pump Deployment in the Gunite and Associated

6 Tanks at ORNL." PIT-MISC-0132. American Nuclear Society Paper No. 001. April 2001.

7

8 ICRP. "Report of ICRP Committee II on Permissible Dose for Internal Radiation." International

9 Commission on Radiological Protection. 1959.

10

11 "ICRP Publication 60: 1990 Recommendations of the International Commission on

12 Radiological Protection Annals of the ICRP Volume 21/1-3." April 1991.

13

14 Leishear, R.A. "ADMP Mixing of Tank 18F: History, Modeling, Testing, and Results."

15 WSRC-TR-2004-00036. Rev. 0. Westinghouse Savannah River Company. 2004.

16

17 Office of Management and Budget. "Guidelines and Discount Rates for Benefit-Cost Analysis of

18 Federal Programs." Circular A-94. 1992.

19

20 U.S. Department of Energy (DOE). "Innovative Technology Summary Report: Light Duty Utility

21 Arm." DOE/EM-0492, OST Reference No. 85, Tanks Focus Area, Office of Science and

22 Technology, DOE. 1998.

23

24 "Radioactive Waste Management." DOE 0 435.1. August 2001.

25

26 "Draft Section 3116 Determination Idaho Nuclear Technology and Engineering Center

27 Tank Farm Facility." DOE/NE-ID-1 1226. DOE, Idaho Operations Office. September 2005a.

28

29 U.S. Nuclear Regulatory Commission (NRC). "Draft Environmental Impact Statement on

30 10 CFR Part 61, Licensing Requirements for Land Disposal of Radioactive Waste."

31 NUREG-0782. September 1981.

32

33 "Update of Part 61 Impacts Analysis Methodology." NUREG/CR-4370, Vol.1. 1986.

34

35 "Reassessment of NRC's Dollar Per Person-Rem Conversion Factor Policy."

36 NUREG-1530. 1995a.

37

38 - . "Branch Technical Position on Concentration Averaging and Encapsulation."

39 January 1995b.

40

41 "Regulatory Analysis Technical Evaluation Handbook." NUREG/BR-0184.

42 January 1997.

43

44 . "Technical Report on a Performance Assessment Methodology for Low-Level

45 Radioactive Waste Disposal Methods." SECY-00-0182. April 2000.

46

47 -. "Decommissioning Criteria for the West Valley Demonstration Project (M-32) at the

48 West Valley Site; Final Policy Statement." Federal Register,.67 FR 5003. February 2002.

49

3-40
1 . "Environmental Review Guidance for Licensing Actions Associated With NMSS

2 Programs. Final Report." NUREG-1748. August 2003a.

3

4 . "Consolidated NMSS Decommissioning Guidance." NUREG-1757. Vols. 1-3.

5 September 2003b.

6

7 . "Technical Evaluation Report for the U.S. Department of Energy, Savannah River Site

8 Draft Section 3116 Waste Determination for Salt Waste Disposal." Letter from L. Camper to

9 C. Anderson, DOE. Washington, DC. December 2005.

10

11 "Regulatory Analysis." Circular A-4. 2003.

12

13 Sams, T.L. "Stage II Retrieval Data Report for Single-Shell Tank 241-C-106." RPP-20577,

14 Rev. 0. CH2M Hill Hanford Group, Inc. May 2004.

15

16 Schlahta, S.N. and T.M. Brouns, PNNL-11906, "Tanks Focus Area FY98 Midyear Technical

17 Review." Tanks Focus Area Technical Advisory Group, Office of Science and Technology,

18 DOE. 1998.

19

20 Vesco, D.P., et al. "Lessons Learned and Final Report for the Houdini Vehicle Remote

21 Operations at the Oak Ridge National Laboratory." American Nuclear Society Paper No. 083.

22 April 2001.

23

3-41

1 4 PERFORMANCE ASSESSMENT

2

3 This section provides guidance to review the performance assessment the U.S. Department of

4 Energy (DOE) uses to evaluate dose for the nominal case (i.e., cases other than intruder

5 scenarios) to demonstrate compliance with the performance objectives of 10 CFR 61.41. The

6 term performance assessment can refer to (1) the process of estimating future radiation doses

7 to receptors or (2) a model or collection of models (e.g., process or submodels) used to

8 estimate future radiation doses to receptors. The review will encompass evaluatio'n of scenario,

9 selection, the performance of the engineered system, the release and migration of radionuclides

10 through the engineered barrier system and the geosphere, and radiation dose to the

11 receptor groups. The review should be performed in a risk-informed manner, so that the

12 reviewer is focused on those areas that have the largest impact on the estimated doses.

13 Additional guidance on developing performance assessment and dose assessment models is

14 found in NUREG-1 573 (NRC, 2000) and NUREG-1 757'(NRC, 2003). Protection of inadvertent

15 intruders (10 CFR 61.42) is discussed in Section 5, protection of individuals during operations

16 (10 CFR 61.43) is discussed in Section 6, and site stability (10 CFR 61.44) is discussed in

17 Section 7 of this guidance document. Typically, a performance assessment is developed to

18 demonstrate whether the performance objectives have been met. A performance assessment

19 is a quantitative evaluation of potential releases into the environment and the resultant

20 radiological doses. Abstraction describes the simplification of information in a performance

21 assessment. The degree of abstraction in a performance assessment model (e.g., a highly

22 abstracted, simplified model or a direct integration of complex process models) typically

23 represents a balance between practical aspects (e.g., maintaining computational efficiency,

24 allowing for efficient modification of the model, and ensuring the model can be relatively easily

25 understood and evaluated) and preserving details that may significantly affect the results. In

26 general, the complexity of the performance assessment should be commensurate with the

27 amount of support to justify the results of the assessment.

28

29 This guidance document provides a consistent set of areas of review and review procedures to

.30 ensure uniformity of reviews performed for different sites by different review teams. However,

31 the guidance document also affords flexibility to the reviewer to perform a more detailed review

32 of particular elements of the performance assessment if justified by the risk significance of the

33 elements (see Sections 4.2 and 4.6).

34

35 The performance assessment documentation will commonly justify the data used, describe the

36 models used, verify and support the models, and evaluate the impact of data and model

37 uncertainty. To evaluate uncertainty, a variety of techniques may be used, including

38 deterministic analysis with sensitivity analysis and probabilistic analysis with uncertainty and

39 sensitivity analyses. The sensitivity analysis results may be used to conduct a risk-informed

40 evaluation through the in-depth review of those parameters and processes most important to

41 system performance with respect to meeting the performance objectives.

42

43 In general, different approaches to performance assessment calculations (e.g., deterministic,

44 probabilistic) have their advantages and disadvantages. A deterministic approach can be very

45 valuable when the analysis is clearly conservative, because it makes the demonstration of

46 meeting the performance objectives more straightforward, and it can be significantly easier to

47 interpret results and explain them to stakeholders. While deterministic analysis can be a

48 suitable methodology for performance assessment, it can also present a challenge when used

49 to represent a system that responds in a highly nonlinear fashion to changes in the independent

4-1
1 variables. In addition, when numerous inputs (e.g., data or models) are uncertain, evaluating

2 the impacts of the uncertainties on the decision can be a challenge with a deterministic analysis.

3 A typical one-off type of sensitivity analysis (e.g., where a single parameter is increased or

4 decreased) will only identify local sensitivity within the parameter space, such that it may not

5 clearly identify the risk implications of the uncertainty in the parameter. A probabilistic approach

6 can have distinct advantages when there are a number of uncertainties that may significantly

7 influence the results of a performance assessment or when the interdependence of parameters

8 or assumptions is not clear (e.g., for highly nonlinear problems). However, there are limitations

9 to probabilistic analysis, such as limited data to define parameter distributions and inappropriate

10 impacts on the performance metric (e.g., peak mean dose) resulting from selection of overly

11 broad parameter distributions, particularly for parameters that affect the timing of doses. Even

12 with a probabilistic approach, conceptual model uncertainty may not be explicitly represented

13 and therefore could not be assessed with uncertainty analysis. This guidance document

14 provides the details to enable the review of deterministic or probabilistic analysis. Review

15 procedures specific to each type of analysis are provided, as well as guidance to help the staff

16 determine when a deterministic analysis may not be sufficient.

17

18 The term "conservatism, " as used with respect to performance assessment, is a relative term.

19 Conservatism is typically defined with respect to what is known or sometimes with standard

20 practices that have yielded accept 'able performance (e.g., a safety factor used in the design of a

21 bridge). Th 'e use of the term "conservatism" with respect to performance assessment is typically

22 more conjectural in nature. For example, a parameter value may not be measured, and

23 therefore the analyst will attempt to select a conservative value based on professional judgment.

24 If a large amo *unt of data is available to support a performance assessment model, less

25 conservatism would be needed in the analysis. In this regard, model support (i.e., information

26 that supports the results of a model) of process model results plays a key role in developing

27 confidence in the output of performance assessment calculations. Because of the long time

28 periods for which system performance is being estimated, performance assessment models

29 cannot be validated in the traditional sense. However, multiple methods for developing

30 confidence in the model projections can be used, including laboratory experiments, alternative

31 modeling approaches, field measurements, natural analogs, and expert elicitation, among

32 others. The amount of model support provided should be commensurate with the risk reduction

33 the natural and engineered system provides. Multiple lines of evidence are particularly

34 important when the risk reduction of the systems being evaluated is large.

35

36 This section of the guidance document discusses scenario selection and receptor groups

37 (Section 4.1), general technical review procedures (Section 4.2), specific technical review

38 procedures for such areas as infiltration, engineered barriers, and source term (Section 4.3),

39 computational models and computer codes (Section 4.4), uncertainty/sensitivity analysis

40 (Section 4.5), evaluating model results (Section 4.6), and evaluating whether releases are as

41 low as reasonably achievable (Section 4.7).

42

43 During the technical review performed using the guidance in this section, the reviewer should

44 identify those factors that are important to assessing compliance with 10 CFR 61.41. By

45 applying this guidance, the reviewer should determine whether adequate support has been

46 provided for important assumptions, data, and models. Important factors may need to be

47 confirmed or verified during the monitoring process for a variety of reasons, such as use of

48 uncertain information or planned installation of an engineered system after the review. As

49 outlined in Section 10 of this guidance document, NRC will emphasize those factors during

4-2
1 monitoring. This guidance document ensures that the performance assessment is a robust

2 assessment of system performance. However, many uncertainties are associated with most

3 performance assessments, and monitoring is a mechanism to more effectively manage those

4 uncertainties. Monitoring can also evaluate new information that may confirm or refute previous

5 information. Monitoring can verify assumptions; however, the- performance assessment must be

6 adequately supported to demonstrate compliance with the performance objectives. The main

7 elements within this section (system description, data sufficiency, data uncertainty, model

8 uncertainty, and model support) were specifically developed to ensure the performance

9 assessment is technically adequate. It is reasonable to expect that key assumptions have

10 adequate technical basis and that the assumptions can be verified during monitoring.

11 Monitoring is not to be used as a substitute for inadequate information, but rather a confirmation

12 of the previous determination of adequacy considering uncertainty. The reviewer should

13 consider the sensitivity and uncertainty analysis and barrier analysis information presented by

14 DOE and discussed in Sections 4.5 and 4.6, respectively. Information supporting the

15 performance of the natural and engineered systems that provide the largest risk reduction

16 should be noted and emphasized in monitoring, as appropriate.

17

18 4.1 Scenario Selection and Receptor Groups

19

20 Scenario analysis is typically the initial step in the model development (or selection) process.

21 Evaluation and selection of applicable features and processes at the disposal site and the

22 surrounding region supports the conceptualization of the total system (i.e., disposal site and

23 surrounding area) and provides confidence in the completeness of the performance assessment

24 model. A scenario description should serve as a broad conceptual roadmap for the

25 performance assessment model, emphasizing those key features and processes that influence

26 the release, transport, and dose from radionuclides migrating from the disposal site. The

27 scenario description should provide sufficient information to understand the general spatial

28 domain and conceptualization of the performance assessment model including release

29 location(s), applicable radionuclide transport pathways, and the location and general

30 characteristics of the receptor(s).

31

32 4.1.1 Areas of Review

33

34 This section focuses on ensuring that appropriate scenarios for radionuclide release,

35 transport, and exposure of a receptor group have been considered for evaluation in the

36 performance assessment. The process for developing scenarios to evaluate in the

37 performance assessment typically includes the following steps: (1) scenario identification,

38 (2) identification of relevant features and processes, and (3) development of receptor

39 characteristics. The period of performance evaluated will influence the development of

40 scenarios for the performance assessment.

41

42 4.1.1.1 Period of Performance and Institutional Controls

43

44 Generally, a period of 10,000 years after closure is sufficient to capture the peak dose from the

45 more mobile, long-lived radionuclides and to demonstrate the influence of the natural and

46 engineered systems in achieving the performance objectives (NRC, 2000). However,

47 assessments beyond 10,000 years may be necessary to ensure (1) that the disposal of certain

48 types of waste does not result in markedly high impacts to future generations or (2) evaluate

49 waste disposal at arid sites with extremely long groundwater travel times. Periods of

4-3
1 performance shorter than 10,000 years are generally not appropriate for disposal facilities for

2 incidental waste, because of the larger fraction of long-lived radionuclides compared to a typical

3 commercial low-level waste (LLW) disposal facility. Presenting and understanding long-term

4 risk (e.g., greater than 10,000 years) can be an important part of performance assessment

5 analyses, even if those risks are not used to demonstrate compliance with the performance

6 objectives of 10 CFR Part 61, Subpart C.

7

8 The regulations in 10 CFR 61.59(b) specify that institutional controls may not be relied upon for

9 more than 100 years after closure. When 10 CFR Part 61was developed, it was envisioned that

10 LLW in a disposal facility would decay, in a maximum of 500 years, to activity levels that would

11 not pose a significant risk to an inadvertent intruder (given assumptions about waste distribution

12 and waste management practices). Significant quantities of long-lived isotopes would be limited

13 such that long-term risks to the public from disposal facility would be acceptable. In developing

14 10 CFR Part 61, NRC considered longer periods of institutional control in the Draft

15 Environmental Impact Statement (NRC, 1981). Assumptions about the persistence of

16 institutional controls in the international community were considered, and a series of public

17 meetings was conducted to get stakeholder input. The consensus among the stakeholders was

18 that it is not appropriate to assume institutional controls would last for more than a few hundred

19 years. The regulatory philosophy is that the engineered and natural system should afford

20 protection to the public. Because of the relatively large uncertainty associated with predicting

21 societal systems, total reliance on institutional controls of a site for extended periods of time

22 was not practical. For the commercial disposal of LLW, a number of requirements are imposed

23 to assure that institutional controls will be maintained for 100 years. The institutional controls

24 allow monitoring and maintenance of the disposal facility to be completed and also restrict

25 access to a disposal facility after closure.

26

27 4.1.1.2 Scenario Identification

28

29 It is generally acceptable to conduct performance assessment modeling based on scenarios

30 such as those described in NUREG-1757 (NRC, 2003, Vol. 2, Appendix I). Scenarios used in

31 the performance assessment should generally account for site-specific data and information

32 about the characteristics of the site and surrounding region (including local practices), potential

33 disruptive processes, and temporal behavior of the engineered and natural barriers. As

34 necessary, the scenarios that are evaluated in the performance assessment should be

35 constrained in a manner consistent with the relevant guidance provided in this document

36 (e.g., scenarios should be based on past, current, and projected future activities at the site).

37

38 Release and transport scenarios are likely to involve mobilization of waste by infiltrating water,

39 contamination of local groundwater and/or surface water, and subsequent use of contaminated

40 groundwater or surface water for domestic, agricultural, and recreational purposes by receptors.

41 Gaseous releases to air may also need to be addressed. Releases may occur at the source

42 location and perhaps at the receptor location (e.g., due to emanation from groundwater) at

43 some sites. Receptor characteristics and exposure scenarios may vary from site to site;

44 however, drinking water and agricultural food production (crops, livestock) commonly contribute

45 to radionuclide intake by many types of receptors. External exposure to contaminated soils and

46 inhalation of resuspended contaminants also are common exposure pathways. Recreational

47 use of surface water (e.g., fishing and swimming, including exposure to contaminated

48 sediments) may be an exposure pathway at some sites.

49

4-4
1 The reviewer should ensure that appropriate exposure pathways are included in the

2 performance analyses or that technical justification is provided to explain why certain pathways

3 may not be applicable for a particular site. For example, common exposure pathways include

4 ingestion, inhalation, and external exposures. Transport pathways may be excluded from

5 performance analysis if it can be demonstrated that there is either limited potential for

6 radionuclides to be released into a particular pathway, or the pathway is not viable (e.g., water

7 is not potable). Specific review guidance for factors that should be considered for the

8 inadvertent intrusion exposure scenario is discussed in greater detail in Section 5. Additional

9 guidance for reviewing protection of individuals during operations is provided in Section 6.

10

11 4.1.1.3 Identification of Relevant Features and Processes

12

13 Prior to conducting detailed technical reviews of the performance assessment, the scenario(s)

14 must be sufficiently described and documented to confirm that key features and processes have

15 been included in the overall system model. An acceptable dose assessment analysis need not

16 incorporate all the physical, chemical, and biological processes at the site. The reviewer should

17 ensure that the scope of the analysis and the level of sophistication of the conceptual models

18 are suitable for demonstrating compliance with performance objectives in 10 CFR Part 61,

19 Subpart C. Examples of features and processes that are commonly considered include air, soil,

20 groundwater, surface water, plant uptake, and exhumation by burrowing animals. Transport

21 and exposure pathways may be excluded from the performance assessment if it can be

22 demonstrated that there is either no potential for radionuclides to be released into a particular

23 pathway, or the pathway is not a viable transport or exposure pathway for the particular

24 scenario (e.g., groundwater is not potable). The following list of general features and processes

25 provides major elements that are expected to be considered when scenarios are developed for

26 evaluation in the performance assessment. These scenarios will be a function of the projected

27 human activities at the site, features and processes of the engineered system, and features and

28 processes of the natural system. Specific features and processes that should be considered

29 when developing submodels of the performance assessment are reflected in the review.

30 procedures of the pertinent sections. Reviewers should consider whether the following features

31 and processes are relevant:

32

33 * Human activities at the site, with emphasis on local practices, that could bring people in

34 contact with waste (e.g., water use, hunting, fishing, recreational activities such a

35 swimming and boating, habitation in dwellings, other unique. activities that involve water

36 use or ground disturbance);

37

38 * Features of the site that affect potential exposure pathways (e.g., groundwater quality

39 and aquifer productivity);

40

41 * Frequency and magnitude of disruptive processes (e.g., seismic events, floods,

42 hurricanes) and their impact on the release of waste to the environment;

43

44 * Location of surface water bodies such as streams and rivers in relation to the waste

45 disposal facility;

46

47 Features of the site meteorology affecting transport of airborne contaminants, including 48 stability class, wind speed, wind direction, temperature, and rainfall;

49

4-5
1 Features of the disposal site that may influence the degradation of engineered systems

2 and the release of radionuclides from those systems [e.g., the process of fluctuation in

3 the shallow water table at the Savannah River Site (SRS) may influence oxidation of and

4 radionuclide release from the wasteform];

5

6 Features and properties of the waste inventory, wasteform, and the facility design that

7 define the release rate of radionuclides from the disposal facility (e.g., the low hydraulic

8 conductivity of an intact cementitious wasteform may limit release of radionuclides to

9 diffusional processes);

10

11 * Features of the disposal facility that may influence the release of radionuclides from the

12 system (e.g., discrete pathways resulting from features of the system [such as sumps,

13 piping, or shrinkage of the wasteform within the disposal container]);

14

15 * Processes that influence the partitioning and mobility of the waste inventory (e.g., the

16 complexation of radionuclides by chelating agents in the waste);

17

18 - Processes that influence the ability of the wasteform to retain radionuclides

19 (e.g., seismically induced fracturing of cementitious wasteforms);

20

21 - Features of local flora that may affect the release of waste (e.g., deep rooting species

22 may reduce the effectiveness of an infiltration cap over time) or the uptake of

23 contaminants by humans and animals;

24

25 - Features of local fauna that may affect the release of waste (e.g., burrowing animals

26 may exhume waste from disposal areas) or the uptake of contaminants by humans and

27 animals (e.g., deer may access contaminated vegetation or water sources that are not

28 viable for human receptors);

29

30 Physical and chemical properties of surface soils such as hydraulic conductivity,

31 porosity, moisture characteristic curve parameters, erodibility, and distribution

32 coefficients that may influence the process of water infiltration and the retention of

33 radionuclides (e.g., sorption processes, erosion rates) at the disposal site;

34

35 Physical and chemical properties .of the saturated and unsaturated zones that influence

36 water infiltration and sorption processes (e.g., soil type, mineralogy); and

37

38 Features of the unsaturated zone (e.g., anthropogenic features such as abandoned

39 wells or natural features such as fractures) that result in discrete transport pathways or,

40 conversely, that will justify assuming porous flow.

41

42 The scenarios evaluated in the performance assessment should integrate the relevant major

43 features and processes at the site. The goal is to develop a set of reasonably anticipated

44 natural conditions, processes, and events and their impact on the engineered disposal system

45 to be represented in the site conceptual model. Processes affecting the long-term stability of

46 the disposal site should also be considered in the development of scenarios for the performance

47 assessment. For example, 10 CFR 61.13 provides specific processes that should be

48 considered, including erosion, mass wasting, slope failure, settlement of wastes and backfill,

49 infiltration through covers over disposal areas and adjacent soils, and surface drainage of the

4-6
1 disposal site. Guidance for reviewing analyses of site stability is provided in Section 7 of this

2 document. Disruptive processes such as erosion, seismic disruption, or other natural hazards

3 such as hurricanes, tornados, fires, or floods may affect the integrity of the disposal site and

4 constitute potential release mechanisms. The reviewer should appropriately consider such

5 processes and develop performance assessment scenarios for those hazards that cannot be

6 ruled out.

7

8 Specific review guidance for factors that should be considered for the inadvertent intrusion

9 exposure scenario is discussed in greater detail in Section 5. Additional guidance for reviewing

10 protection of individuals during operations is provided in Section 6.

11

12 4.1.1.4 Receptor Characteristics

13

14 Receptor characteristics may differ for air, groundwater, and surface water pathway scenarios

15 and the receptor group lifestyle habits (e.g., regional differences) may differ accordingly.

16 Receptor characteristics may also differ for onsite worker and public exposure scenarios and for

17 inadvertent intruder scenarios. The assumptions regarding receptor location and lifestyle habits

18 should be appropriately integrated into the performance model.

19

20 To demonstrate compliance with 10 CFR 61.41 or 10 CFR 61.42, a receptor should be

21 assumed to engage in residential, agricultural, or other activities that are consistent with

22 regional practices. The public receptor, protected by 10 CFR 61.41, is assumed to be located

23 at the boundary of the DOE-controlled area until the end of the active institutional control period,

24 at which point the receptor is assumed to move to the point of maximum exposure outside of the

25 disposal site. A receptor engaging in activities on the disposal site, rather than outside the

26 disposal site, is regarded as an inadvertent intruder protected by 10 CFR 61.42.

27 A disposal site consists of disposal units and a buffer zone [10 CFR 61.7(a)(2)]. For

28 convenience, the minimal area enclosing all of the disposal units in a disposal site (but not the

29 buffer zone) often is referred to as the "disposal area" (Figure 4-1). A buffer zone is a portion of

30 the disposal site that lies under the site and between the boundary of the disposal site and any

31 disposal unit. The buffer zone provides space to establish monitoring locations and to take

32 mitigative measures if needed [10 CFR 61.7(a)(2)]. An appropriate buffer zone is expected to

33 extend approximately 100 m [330 ft] from the disposal area in most cases. Alternate buffer

34 zone sizes may be acceptable if supported by technical justification. In general, appropriate

35 technical justification is expected to demonstrate that an alternate amount of space is needed to

36 implement monitoring activities or potential mitigative measures. Buffer zones should not be

37 enlarged solely to facilitate compliance with the performance objectives.

38

39 In the case of a tank farm, the tanks are expected to be regarded as disposal units and the

40 typical buffer zone is expected to extend approximately 100 m [330 ft] beyond any tank. In

41 some instances, the point of maximum exposure may be more than 100 m [330 ft],from the

42 disposal area. For example, a complex hydrogeologic system or overlap of plumes from

43 multiple sources may cause the maximum concentration of radionuclides in groundwater to

44 occur more than 100 m [330 ft] from the disposal area. In this case the location of the public

45 receptor protected by 10 CFR 61.41 would not be expected to coincide with the boundary of the

46 buffer zone.

47

48

4-7
1

2-

Disposal Ar~ea:

Boundary

Disposal St

BoundaryBuffer Zone

Each circle represents a disposal unit

3 Figure 4-1. Geometric Relationship of the Disposal Units, Disposal Area, and Buffer

4 Zone of a Disposal Site. Adapted From the Final Environmental Impact Statement for

5 10 CFR Part 61 (NRC, 1982).

6 4.1.2 Review Procedures

7

8 Details of the analysis related to the exposure pathways in the biosphere and dosimetry are

9 largely determined by the scenario and the assumed behavior of the receptor. Accordingly,

10 models related to the exposure pathways in the biosphere and dosimetry should not change

11 from one site to another unless there is a significant change in the scenario and associated

12 receptor behavior or location. In general, there are two primary areas of the dose analysis

13 where the conceptual model is expected to change from one site to another; these are related

14 to the source term (including the effects of engineered barriers on release) and environmental

15 transport. The reviewer should ensure that site-appropriate source terms and transport pathway

16 models are summarized in the conceptual model description. Source term analysis is

17 discussed in Section 4.3.3, and the principal environmental transport pathways (groundwater

18 [including transport through the unsaturated zone], surface water, and air) are discussed in

19 Section 4.3.4. The reviewer should perform the following procedures:

20

21 - Ensure that the scenarios used in the performance assessment to demonstrate

22 protection of the general population from releases of radioactivity include radionuclide

23 transport pathways via groundwater, surface water, soil (via erosion), and air, or that a

24 sufficient technical basis is provided for their exclusion. Transport pathways may be

25 excluded from performance analysis if it can be demonstrated that there is either limited

4-8
1 potential for radionuclides to be released into a particular pathway, or the pathway is not

2 viable (e.g., water is not potable).

3

4 * Ensure that disruptive processes such as erosion or seismic disturbance and natural

5 events such as hurricanes, tornados, fires, or floods have been appropriately considered

6 in the scenario selection process. For example, erosion at a waste disposal facility may

7 result in the need for development of performance assessment scenarios of waste

8 transport via suspension in surface water or atmospheric pathways.

9

10 * Ensure that adequate technical basis has been provided for screening disruptive

11 processes from representation in the performance assessment model and that disruptive

12 processes which were not screened were implemented in the performance

13 assessment models.

14

15 - Evaluate whether assumptions regarding receptor location and information defining

16 human activities, such as land use and food consumption, are appropriately chosen for

17 each exposure scenario and each exposure pathway.

18

19 - Determine whether lifestyle habits based on regional practices may be less conservative

20 than common generic lifestyle habits. Adequate technical basis should be provided for

21 locally defined lifestyle habits that are less conservative than commonly accepted

22 lifestyle habits in generic dose assessments.

23

24 * Evaluate whether information for each scenario is presented in a clear and transparent

25 manner (e.g., each pathway is listed, receptor characteristics and lifestyle behavior are

26 described, maps showing potential receptor locations with respect to the disposal site

27 are provided).

28

29 * Ensure that the public receptor location for evaluating compliance with 10 CFR 61.41 is

30 at the point of maximum exposure outside the buffer zone (see Section 4.1.1.4).

31

32 * Ensure that the buffer zone has been appropriately defined, generally not to exceed

33 100 m [330 ft] from the disposal area. The reviewer should ensure that adequate

34 technical basis is provided for a proposed buffer zone size significantly larger than 100

35 m. In general, buffer zone size is expected to be based on the amount of space needed

36 to perform monitoring activities and any necessary mitigative measures.

37

38 * Ensure that DOE has considered applicable features and processes that could

39 significantly influence disposal site performance in developing its scenarios (see

40 Section 4.1.1.3).

41

42 * Ensure that DOE has not taken credit for active institutional controls for more than

43 100 years after closure.

44

45 * Ensure that the analysis estimated performance for a period of 10,000 years to

46 demonstrate compliance with 10 CFR Part 61, Subpart C. A period of 10,000 years is

47 generally sufficiently long to (1) evaluate performance of both engineered barriers and

48 the site and (2) capture the peak doses from moderately mobile long-lived radionuclides.

49

4-9
1 * Determine, if appropriate, that DOE has evaluated doses beyond 10,000 years (e.g., for

2 strongly sorbing radionuclides or very long-lived engineered barriers) and whether those

3 doses are expected to be markedly higher than those evaluated for compliance with

4 10 CFR 61.41 (i.e., 10,000 years). If so, the reviewer should note in the Technical

5 Evaluation Report the maximum doses expected to occur after 10,000 years.

6

7 * Determine whether DOE has considered waste inventory characteristics such as activity, 8 half-life, and mobility of radionuclides in determining whether the appropriate

9 performance period should be longer than 10,000 years.

10

11 * Ensure that processes and conditions that control engineered barrier degradation, 12 water infiltration, leaching of waste,. and release and transport of radionuclides to the

13 general environment have been considered in development of scenarios for the

14 performance assessment.

15

16 * Ensure scenario descriptions and any associated figures or maps depicting scenarios

17 are supported by and consistent with the system descriptions and information regarding

18 regional features and practices.

19

20 - Verify that scenario descriptions are consistent with the models implemented in the

21 performance assessment.

22

23 - Ensure that DOE has considered the, list of general features and processes 24 provided in Section 4.1.1.3 in development of scenarios for implementation in the

25 performance assessment.

26

27 4.2 General Technical Review Procedures

28

29 The review should focus on understanding the importance of various assumptions, models, and

30 data in the performance assessment. As discussed in Section 4, the performance assessment

31 model can be a collection of other models (e.g., submodels or process models) of varying levels

32 of complexity, or it can be an integrated model. Regardless of the form of the numerical

33 representation, the performance assessment model will represent numerous processes

34 (e.g., infiltration, degradation of engineered barriers, release and transport of radionuclides,

35 exposure of receptors to radionuclides). There are general technical review procedures that are

36 applicable for all parts of the DOE performance assessment model. This section identifies

37 those review procedures that can be broadly applied. Specific review procedures are

38 identified in Section 4.3. The general technical review procedures can be divided into five

39 separate categories:

40

41 * System Descriotion: These review procedures ensure that DOE has adequately 42 described the performance assessment models and the overall disposal system and that

43 the different performance assessment models have been appropriately integrated 44 (e.g., infiltration with source term release). The description should be adequate for the

45 reviewer to understand the modeling and analyses, and if necessary, to perform 46 independent analysis of the disposal system (see Section 4.2.1.).

47

48 * Data Sufficiency: These review procedures ensure that DOE has provided sufficient

49 data to support the performance assessment models. The types of data to be

4-10
1 considered may include site-specific data (e.g., laboratory measurements and field-scale

2 measurements or experiments), data from analogous sites, data from generic sources,

3 output from detailed process-level models, and expert judgment (see Section 4.2.2.).

4

5 * Data Uncertainty: These review procedures ensure that DOE has captured the

6 variability in data and provided an assessment of uncertainty due to, the incomplete

7 knowledge of the natural system, engineered system, or inventory. Parameter

8 uncertainty can be propagated through the performance assessment by distributions of

9 variables (probabilistic analysis) (e.g., hydraulic conductivity, porosity, retardation

10 coefficient). In a deterministic analysis, the data uncertainty can be examined with

11 sensitivity analyses and bounded by the selection of conservative values (see

12 Section 4.2.3.).

13

14 * Model Uncertainty: These review procedures ensure that DOE has evaluated the impact

15 of model uncertainty and discussed the inherent uncertainties in applying predictive

16 models: .(1) over long periods of time for which direct validation is precluded and (2) to

17 complex systems for which measurement and characterization may be limited. These

18 uncertainties can be evaluated in the performance assessment by considering

19 reasonable ranges in conditions and processes to test the robustness of the model, by

20 using distributions of parameters to represent the likely ranges in conditions or

21 processes, or by bounding the effects of model uncertainty by using conservative

22 assumptions. Ideally, model uncertainty is minimized by developing as much model

23 support as practical (see Section 4.2.4.).

24

25 * Model Support: These review procedures ensure that the output from the DOE

26 performance assessment model can be supported by comparison to independent data.

27 In general, using these review procedures, the reviewer should expect to evaluate

28 multiple lines of evidence supporting the selected model (e.g., field tests or laboratory

29 tests that provide a technical basis for selecting a certain release mechanism). In

30 addition, the reviewer may conduct independent analyses for comparison of process

31 model results, or the model results may be compared to analogous systems (see

32 Section 4.2.5.).

33

34 To review the overall performance assessment, the reviewer should recognize that models DOE

35 used may range from highly complex process-level models to simplified models, such as

36 response surfaces or lookup tables. The reviewer should evaluate the adequacy of the model

37 and the supporting technical basis, regardless of the level of complexity. The reviewer should

38 determine whether uncertainties in the models and parameters are appropriately accounted for

39 in the DOE performance assessment. Specifically, the reviewer should follow the procedures

40 given in Sections 4.2.1-4.2.5.

41

42 4.2.1 System Description Review Procedures

43

44 * Examine the descriptions of design features (including engineered barriers, wasteforms,

45 and other engineered components) and the relevant natural system features (including

46 the geological, hydrological, and geochemnical aspects of the natural barriers at the site).

47 Verify that the descriptions sufficiently support the development of a conceptual model of

48 the site, including major pathways for water and radionuclide movement.

49

4-11
1 * Assess whether the design and natural system features have been adequately

2 incorporated into the performance assessment. Where simplifications are used, confirm

3 that the technical bases used to support the simplifications (e.g., modeling assumptions

4 and approximations) are adequate (e.g., verify that the potential effects of the

5 simplifications on dose predictions have been bounded) and have been documented in a

6 transparent and traceable manner.

7

8 Determine whether the conditions and assumptions used in the performance

9 assessment modeling are consistent with the design feature documentation.

10

11 Verify that the assumptions, data, and models DOE used are consistent among the

12 different parts of the performance assessment. For example, the release models used

13 in the source-term model should be consistent with the chemical environment assumed

14 for the engineered barrier system.

15

16 Confirm that common boundary and initial conditions are consistent among submodels

17 of the performance assessment (e.g., the recharge rate in saturated zone modeling

18 should be consistent with infiltration applied to the unsaturated zone if there is not

19 significant lateral flow in the unsaturated zone).

20

21 Examine how features and processes related to engineered and natural barrier system

22 performance have been included in the performance assessment model, and verify that

23 performance through time has been adequately represented. For example, if the

24 hydraulic conductivity of a barrier is expected to increase over time, verify that the

25 hydraulic conductivity value(s) used in the performance is consistent with or bounds the

26 expected degradation.

27

28 Evaluate whether conceptual models sufficiently account for the most important physical,

29 chemical, and biological processes at the site so that a more realistic representation of

30 the site would not lead to higher dose estimates.

31

32 4.2.2 Data Sufficiency Review Procedures

33

34 - Confirm that the data used to support conceptual models, process-level models, and

35 simplifications in the performance assessment are sufficient. Examine the parameters

36 used for these models, and verify that the parameters are based on adequate

37 technical basis, such as data derived from laboratory experiments, site-specific field

38 measurements, operational experience, research at comparable sites, and

39 process-level modeling.

40

41 - Confirm that DOE has provided sufficient data on the characteristics of the waste,

42 engineered barriers, and natural system to establish initial and boundary conditions

43 for models.

44

45 - Verify whether sufficient data have been collected to adequately support modeled

46 degradation of engineered barriers and near-field transport of radionuclides as well as to

47 establish important characteristics of the natural system (e.g., geochemistry, hydrology).

48

4-12
1 Verify that parameter values are derived from site-specific data when available or that an

2 analysis is included to show that data from generic sources leads to a conservative

3 assessment of performance.

4

5 Verify that data from generic sources are appropriate for the site-specific conditions or

6 materials in the performance assessment. For example, if distribution coefficients for

7 cement are taken from Bradbury and Sarott, verify that the formulations used in the

8 reference are consistent with the grout being used at the site (Bradbury and

9 Sarott, 1995).

10

11 Verify that experimental conditions for laboratory or field measurements

12 (e.g., temperature, chemistry of a solution used in a leach test) are reasonably

13 representative of expected system conditions or that an adequate assessment of the

14 impact of the differences in conditions has been provided.

15

16 Confirm that parameter values used in process-level models are appropriate for the

17 time- and space-scales of the performance assessment calculations.

18

19 Examine the initial and boundary conditions of the models, and verify that they are

20 consistent with available data.

21

22 Confirm that sensitivity or uncertainty analyses have been used to assess data

23 sufficiency. If the analyses identified significant impacts associated with the uncertainty

24 in particular data, evaluate additional data that was acquired to limit the uncertainty in

25 results to an acceptable range. As appropriate, document the associated assumption in

26 the TER.

27

28 If expert judgment is used as a basis for selecting parameter values where default model

29 parameters or site-specific data are not sufficient, evaluate the methods DOE used to

30 develop the information. Confirm the information was developed from unbiased sources

31 in a transparent and objective way [for example, see guidance in NUREG-1563

32 (NRC, 1996)].

33

34 As appropriate, verify that DOE used acceptable approaches for peer review and data

35 qualification [see guidance such as NUREG-1297 and NUREG-1298 (NRC, 1988a,b)],

36 or provided adequate justification for using alternative approaches.

37

38 4.2.3 Data Uncertainty Review Procedures

39

40 - If deterministic models are used in the performance assessment, evaluate the technical

41 bases for parameter values, assumed ranges used in sensitivity analyses to characterize

42 data uncertainty, and bounding values used in conceptual and process models.

43

44 - If a deterministic approach is used, verify that key parameter values are reasonably

45 conservative, technical basis is provided for conservative assumptions, and the

46 conservatism of values is defined on a total system level and not at the local level. For

47 example, increasing the hydraulic conductivity of saturated zone aquifers to address

48 uncertainty may be conservative with respect to contaminant travel time but may be

49 nonconservative with respect to dose as a result of increased dilution of contaminant

50 fluxes entering the saturated zone from the unsaturated zone.

4-13
1 * For deterministic or probabilistic approaches, evaluate whether statistical correlation

2 between parameters has been appropriately considered in the analysis. For example, a

3 scenario of increased infiltration may necessitate a positive correlation (with respect to

4 infiltration) of parameters related to the timing of oxidizing conditions in a wasteform and

5 the timing of degradation of a steel barrier if the model is abstracted and is not

6 representing the underlying physical processes. Verify that adequate technical basis or

7 a bounding argument is provided for unanalyzed correlations.

8

9 * If probabilistic models are used in the performance assessment, evaluate the technical

10 bases for parameter ranges, probability distributions, or bounding values. The reviewer

11 should verify that the technical bases adequately support the treatment of uncertainty

12 and variability of these parameters.

13

14 * Verify that uncertainty in initial and boundary conditions has been appropriately

15 considered and is reflected in the performance assessment models.

16

17 * Confirm that uncertainty in data from both temporal and spatial variations has been

18 incorporated into the parameter ranges (e.g., degradation of barrier performance with

19 time, spatial variation of soil properties).

20

21 - Determine whether expert judgment was used as a basis for data uncertainty, and

22 confirm the information was developed in a transparent and objective way [e.g., see

23 guidance in NUREG-1 563 (NRC, 1996)].

24

25.

26 4.2.4 Model Uncertainty Review Procedure

27

28 - Compare the models used in the performance assessment with available data such as

29 design data and verification tests for engineered barriers and wasteforms, laboratory

30 experiments, field measurements, and monitoring data. Confirm that models in the

31 performance assessment were developed considering the uncertainty and variability in

32 supporting information.

33

34 - Verify that conceptual model uncertainties are adequately described and documented.

35 Verify that the impact of model uncertainty op overall system performance was

36 properly assessed.

37

38 - Examine the mathematical models included in the performance assessment. Evaluate

39 the assumptions, the limitations, and uncertainties of the models and the bases for

40 excluding alternative models.

41

42 - Verify that the models used in the performance assessment adequately represent or

43 bound the uncertainty associated with underlying process-level models, if applicable. 44 Where appropriate, use a detailed auxiliary analysis (i.e., an analysis performed outside

45 of the overall performance assessment analysis) to verify that the DOE performance

46 assessment approach reflects or bounds the uncertainties in the process-level models.

47

48 - Verify that the selected conceptual model is conservative or more representative of

49 available supporting information relative to alternative models. Alternative models

4-14
1 considered should (1) be reasonably consistent with available information or (2) should

2 have been observed at other sites and cannot be refuted with existing information.

3

4 * Verify that quantitative evaluation of model uncertainty included the impact of data

5 uncertainty in alternative models.

6

7 4.2.5 Model Support Review Procedure

8

9 * Evaluate the output from the performance assessment, and verify that DOE has

10 compared the results with an appropriate combination of site characterization and

11 design data, process-level modeling, laboratory testing, field measurements, analogs,

12 and formal independent peer review.

13

14 - Examine the output from the mathematical models for consistency of the mathematical

15 model response with the response expected based on the description of the

16 conceptual models.

17

18 * Verify that the performance assessment model is reasonably supported by observations

19 from the site, if available. For example, compare the output from the DOE performance

20 assessment with inferences about fate and transport of radionuclides in the environment

21 developed from data for environmental monitoring of leaks and spills.

22

23 - Where appropriate, use independent analyses to evaluate selected parts of the

24 DOE performance assessment model, and assess whether the resulting doses

25 are comparable.

26

27 - If possible, perform simplified calculations of processes, and compare to the

28 intermediate outputs of the performance assessment models. For example, estimate the

29 groundwater travel time of select radionuclides using information on hydraulic gradient,

30 hydraulic conductivity, soil porosity, soil density, and radionuclide distribution

31 coefficients, and compare to the travel times generated with performance

32 assessment models.

33

34 * Confirm that DOE has identified and implemented adequate procedures to construct and

35 test its mathematical and numerical models.

36

37 4.3 Specific Technical Review Procedures

38

39 In contrast to the general review procedures presented in the previous section, this section

40 details review procedures that are specific to the different technical areas comprising

41 component models of the DOE performance assessment. These review procedures were

42 developed from experience in prior reviews and may be enhanced, modified, or supplemented

43 based on future experience. As previously discussed, a performance assessment model may

44 be a manually integrated or fully automated collection of individual models representing specific

45 technical areas and processes. The individual models are commonly referred to as component

46 models, process models, submodels, or abstractions. This terminology is used interchangeably 47 in the specific review procedures that follow. The submodels are presented in a "top-down"

48 sequence that is similar to that described in NUREG-1 573 (NRC, 2000). Not all of the specific

49 technical review procedures will apply to every waste determination, and the level of review

4-15
1 should be adjusted to reflect the significance of a given component (e.g., infiltration, engineered

2 barriers) to system performance (see Section 4.6). The topics included in the section are not all

3 inclusive; technical areas not covered should be reviewed in accordance with the general

4 technical review procedures.

5

6 It is expected that DOE will have a fairly large collection of technical reports covering a variety of

7 activities that have occurred at the DOE sites over the years. For example, hydrogeologic

8 studies and models may have been completed or developed to manage existing contamination

9 or to evaluate the performance of other disposal facilities for radioactive waste at the DOE site.

10 To the extent practical, the reviewer should consider other sources of information that may

11 support or refute the models and analysis used in the waste determination. For example, the

12 observed transport of Cs-137 from a LLW disposal facility at the DOE site may support or

13 refute the use of various values of Kd from a generic literature source used in the

14 performance assessment.

15

16 4.3.1 Climate and Infiltration

17

18 4.3.1.1 Areas of Review

19

20 This section focuses on the models and data that support climate projections, infiltration, and

21 unsaturated zone flow estimates used in performance assessments supporting waste

22 determinations. Temporal and spatial variations in processes and parameters related to

23 climate, infiltration, and unsaturated zone flow are potentially important to system performance

24 because one of the primary mechanisms of radioactivity release from a disposal facility is

25 leaching with water. A distinction between infiltration (that part of precipitation which moves

26 past the root zone) and water flow in the unsaturated zone (deeper flow whether through soil,

27 rock, or anthropogenic fill material) must be made. Infiltration can affect engineered barrier

28 performance and the release of radionuclides (see Section 4.3.2). Unsaturated zone flow is a

29 function of the physical characteristics of the unsaturated zone and the rate and distribution of

30 infiltration input to the unsaturated zone (e.g., boundary and initial conditions). Physical

31 characteristics of the unsaturated zone may be affected by anthropogenic and natural features.

32 Unsaturated zone flow affects the transport of radionuclides to the saturated zone.

33

34 4.3.1.1.1 Current Meteorology and Precipitation at the Site

35

36 The amount of water that contacts the waste is important for estimating the release of

37 radionuclides from a waste disposal facility. Knowledge of local meteorology and precipitation

38 is necessary to estimate infiltration and the potential for water to contact the waste. Current

39 information provides a baseline against which to evaluate the significance of any potential

40 changes over the period of performance (see Section 1.1.3).

41

42 Meteorological information is typically an input to calculations or models used to estimate

43 infiltration. The reviewer should evaluate information on precipitation (duration, intensity,

44 frequency, and seasonal variations of precipitation events), local air temperatures (daily and

45 seasonal variations), wind speeds and directions, and air humidity levels.

46

47 4.3.1.1.2 Current Infiltration and Unsaturated Zone Flow at the Site

48

49 The disposal horizon at most sites is located above the local water table in the hydrologically

50 unsaturated zone, sometimes also referred to as the vadose zone. Precipitation at a site can

4-16
1 follow several paths. Depending on the topography of the site and the composition of the

2 topmost soil or cover materials, Water may tend to pond in some areas or to run off. Some

3 water may penetrate only the topmost layer of soil where it may be'evaporated directly to the

4 atmosphere or be taken up by plants and then transpired back into the atmosphere.

5

6 Some fraction of the precipitation may move below the zone of evapotranspiration and contact

7 engineered barriers or other portions of the disposal system. This fraction is infiltration. Flow of

8 infiltration through the unsaturated zone will be affected by heterogeneities, fractures, and

9 anthropogenic changes and features that may lead to faster and preferred water pathways

10 (e.g., abandoned boreholes and wells). The amount of water that moves to the disposal

11 horizon, the frequency of the flow, and the spatial distribution of the flow are all potentially

12 significant to waste disposal facility performance. If waste is located below the water table, then

13 saturated zone flow would control the amount of water contacting the waste. Water contact may

14 be limited by the engineered barriers and related engineered systems.

15

16 The reviewer should evaluate the information on local soils and rocks that affect infiltration and

17 unsaturated zone flow (e.g., hydraulic conductivity, porosity, moisture content), vegetation

18 (types, distributions, seasonal changes), topography, erosion, runoff and drainage, and the

19 potential for flooding or ponding. The reviewer should examine the seasonal variation in the

20 independent variables for modeling infiltration and resultant unsaturated zone flow. For

21 example, in colder climate sites, a significant fraction of annual infiltration may result from snow

22 melt or similar processes when evapotranspiration is low. For modeling unsaturated zone flow,

23 DOE should provide properties (e.g., moisture characteristic curve parameters) that are

24 supported by empirical measurement or are sufficiently conservative (if generic information is

25 used). The reviewer should examine information provided on the spatial variability of features

26 and properties or the approach to address spatial variability. The reviewer should evaluate the

27 model support for estimates of unsaturated zone flow. Because unsaturated zone flow is

28 generally inherently more uncertain than saturated zone flow, a commensurate increase in the

29 model support or the conservatism of the analysis should be expected. The reviewer should

30 consider that spatial variability in features or hydrologic properties can affect the importance of

31 temporal variability. For example, the presence of fractures could increase the importance of

32 considering individual storm events in modeling long-term infiltration.

33

34 Information should be provided regarding the potential for perched zones to affect flow and

35 transport. If perched zones affect flow and transport, monitoring data should support the

36 location, extent, and persistence of the perched zones. Changes in operation that may affect

37 perched zones (e.g., use of percolation ponds) should be evaluated. If the perched zones are

38 important, the reviewer should determine whether DOE has evaluated the relative contribution

39 from both natural (e.g., recharge) and anthropogenic sources to the extent of the

40 perched zones.

41

42 4.3.1.1.3 Proiected Meteorology and Precipitation at the Site

43

44 The reviewer should evaluate the current information on the meteorology and precipitation at

45 the site. The reviewer should also evaluate paleoclimatic information for the site. Recent and

46 current climate data are the best available predictors of the near-term future conditions at the

47 site whereas paleoclimate data may provide a basis for interpreting potential future changes in

48 the climate. It is important to assess the DOE assumptions to extrapolate the past and current

49 information and project those values and patterns into the future. For example, climate changes

50 may be assumed to be cyclical or linked to orbital patterns (e.g., Milankovitch forcing). Climate

4-17
1 projections should cover the full duration of the performance period. The reviewer should

2 examine how uncertainties inherent in projections of future climates have been accounted for

3 and how those uncertainties have been propagated through the performance assessment,

4 as appropriate. Sensitivity of system performance to the affects from the timing of climate

5 change (e.g., infiltration rates, moisture contents, water table depth, fluvial erosion) should be

6 evaluated to identify whether climate change induced by human activities can significantly affect

7 the performance assessment results. In many cases for buried waste, the impact of climate

8 change is mitigated by the damping function of the overlying geologic materials. In addition, a

9 proper consideration of the variability in hydrologic conditions for the present day may

10 encompass many future climate states. However, because predictive capabilities for future

11 climates continue to evolve, if a significant sensitivity is identified, staff should incorporate

12 current information regarding climate change, as appropriate, into the review.

13

14 4.3.1.1.4 Proiected Infiltration and Unsaturated Zone Flow at the Site

15

16 In general, site conditions are expected to change over long time periods and to result in

17 changes to infiltration at the site. Changes to infiltration will produce changes in the unsaturated

18 zone flow. The reviewer should evaluate the available information on present day infiltration at

19 the site that may be used to project future infiltration rates. Projections of future infiltration

20 should cover the full duration of the performance period. Infiltration projections should account

21 for any construction or engineered features (see Section 4.3.2) that are designed to control or

22 reduce infiltration (e.g., caps, drainage layers, geosynthetics) or other changes to site conditions

23 that may affect infiltration (e.g., variations in precipitation, vegetation, or soil cover caused by

24 erosion). The reviewer should evaluate the integration of infiltration and water flow in the

25 unsaturated zone, if computed by different models. In reviewing barriers used to control

26 infiltration, the reviewer should evaluate any credit taken for maintenance or long-term

27 performance of these barriers after the loss of institutional controls. The relationship between

28 projected precipitation and projected infiltration should be described. Infiltration projections

29 should take into account the uncertainties inherent in such estimates and should propagate

30 those uncertainties through the performance assessment, as appropriate. Infiltration at

31 semiarid sites is generally controlled by short-duration (i.e., hourly or daily) storm events. Thus,

32 estimates of infiltration based solely on long-term (i.e., monthly or yearly) precipitation and

33 evaporation rates at a semiarid site may be misleading.

34

35 4.3.1.2 Review Procedures

36

37 To review this performance assessment submodel, the reviewer should consider the degree to

38 which DOE relies on climate and infiltration to demonstrate compliance with 10 CFR 61.41,

39 considering available sensitivity analyses, uncertainty analysis, and barrier or component

40 analysis (see Section 4.6). For example, the reviewer should perform a detailed review of this

41 area if DOE relies on estimates of infiltration that are significantly lower than natural recharge

42 values and that correspondingly produce lower release rates and provide significant delay in the

43 transport of radionuclides. If, on the other hand, DOE demonstrates that this submodel has a

44 minor impact on release rates or the transport of radionuclides to the receptor, then a simplified

45 review focusing on whether the analysis has been appropriately implemented should be

46 conducted. In general, higher infiltration rates will result in higher dose estimates, because

47 there will be higher mass flux rates of contaminants to the saturated zone. The overall dilution

48 in the calculation will be dominated by the saturated zone modeling and not the dilution in the

49 unsaturated zone (which increases with increased infiltration). In a risk-informed,

4-18
1 performance-based review, some of the following review procedures may not be necessary

2 when conducting a simplified review for models with a minor impact on performance:

3

4 * Apply the general review procedures found in Section 4.2 to the assessment of climate,

5 infiltration, and unsaturated zone flow.

6

7 * Confirm that an adequate baseline for current meteorology and precipitation at the site

8 has been used. Evaluate the adequacy of information for precipitation (duration,

9 intensity, frequency, and seasonal variations of precipitation events), local air

10 temperatures (daily and seasonal variations), wind speeds and directions, and air

11 humidity levels.

12

13 Evaluate engineered features (see Section 4.3 of this guidance) that are designed to

14 control or reduce infiltration (e.g., caps, drainage layers, geosynthetics) or other changes

15 to site conditions that may affect infiltration (e.g., variations in vegetation or erosion of

16 soil cover). Evaluate credit taken for maintenance during the institutional control

17 period and long-term, passive performance of these barriers after the loss of

18 institutional controls.

19

20 * Examine the temporal and spatial relationship between infiltration and the water table

21 elevation for those disposal sites with waste located near the water table.

22

23 * Evaluate information regarding the potential for perched water zones to affect flow and

24 transport. Activities that may affect perched zones (e.g., use of percolation ponds)

25- should be-evaluated. If perched zones are important to the performance of the site,

26 determine whether DOE has adequately evaluated the relative contributions from both

27 natural and anthropogenic sources to the extent of the perched zones.

28

29 - Verify that the data for infiltration are at appropriate time- and space-scales. Confirm

30 that adequate site-specific climatic, surface, and subsurface information is used.

31

32 - Confirm that precipitation estimates are based on long-term precipitation data that

33 adequately represent conditions at the disposal facility location. Long-term data for

34 precipitation are typically considered to extend over a period of several decades to

35 100 years.

36

37 * If estimates of infiltration are based on modeling, verify that the analysis has considered

38 seasonal variation in independent variables and short duration, large magnitude events,

39 especially when discrete high-permeability pathways are present in the near surface

40 (e.g., dessication cracks in a clay soil). The importance of temporal variability may be

41 dependent on spatial variability.

42

43 * Where applicable, confirm that adequate representation of the effects of fracture

44 properties, fracture distributions, matrix properties, heterogeneities, time-varying

45 boundary conditions, evapotranspiration, depth of soil cover, and surface-water runoff

46 and run-on is incorporated in the model or calculation.

47

48 Confirm whether uncertainty in data, because of both temporal and spatial variations in

49 conditions affecting climate and infiltration, is incorporated into the selection of

50 deterministic parameters or the definition of parameter ranges. For example, the

4-19
1 reviewer should evaluate the climatic and hydrostratigraphic parameters used in the

2 model to verify that they are consistent with site characterization data. The reviewer

3 should confirm the data is sufficiently detailed such that heterogeneities that may

4 influence the distribution and rate of liquid-water flux that has moved beyond the zone of

5 evapotranspiration (infiltration and unsaturated zone flow) have been captured.

6

7 Evaluate the assumptions DOE used to extrapolate from past climate data to

8 future climate conditions. For example, the reviewer should determine whether

9 climate changes are assumed to be cyclical or are linked to orbital patterns

10 (e.g., Milankovitch forcing).

11

12 - Verify whether climate projections cover the full duration of the performance period and

13 determine whether uncertainties in the projections are adequately accounted for and

14 propagated through the performance assessment.

15

16 - Confirm that the performance assessment incorporates the hydrologic effects of future

17 climate change that could alter the rates and patterns of present-day infiltration into the

18 unsaturated zone.

19

20 - Evaluate the sensitivity of the performance assessment to the timing of climate change

21 impacts (e.g., infiltration, saturation, water table depth, fluvial erosion) as a means to

22 evaluate anthropogenic processes affecting climate.

23

24 - Ensure that infiltration estimates are either chosen in a clearly conservative manner or

25 are supported by multiple lines of evidence. Typically, higher infiltration rates are more

26 conservative, although in some circumstances a higher infiltration rate could result in a

27 lower dose (e.g., dilution in perched water zones).

28

29 • Ensure that appropriate model support is provided for infiltration rates. For example,

30 ensure infiltration rates are consistent with calibrated recharge rates from large-scale or

31 regional flow models, other calculated values, infiltration rates from other site estimates,

32 and values estimated based on soil properties.

33

34 Because some DOE sites can be quite large, if site-specific infiltration rates developed

35 or measured from other onsite areas are used to support the estimates for the waste

36 disposal facility, confirm that they would be expected to be reasonably representative of

37 local estimates for the waste disposal facility based on similarity of important variables

38 (e.g., soil type, topography, vegetation).

39

40 Ensure that the estimates of infiltration and unsaturated zone flow have appropriately

41 accounted for anthropogenic features or actions at the site. For example, an

42 undisturbed soil profile may have an infiltration rate that is different from that for a

43 disturbed soil. Abandoned wells or other manmade features may act as discrete

44 pathways for infiltration.

45

46 ° Ensure that the parameters DOE used to model unsaturated zone flow are supported by

47 empirical measurements or that generic information sources are sufficiently

48 conservative. Confirm that DOE considered spatial variations in the properties of

49 materials when selecting parameter values.

50

4-20
1 Determine whether the impact of fractures or other naturally occurring discrete pathways

2 (such as sand lenses) have been represented in modeling flow in the unsaturated zone,

3 if applicable. Ensure that the selected model has not underestimated the potential

4 effects of preferential pathways.

5

6 Determine whether adequate model support is provided for unsaturated zone flow

7 (e.g., field-scale observations or measurements, evaluation of the transport of past leaks

8 or spills) consistent with its risk significance. If a unit gradient approach is not adopted,

9 ensure that adequate model support is provided to justify a less conservative approach.

10

11 4.3.2 Engineered Barriers

12

13 A wide variety of engineered barriers may be employed for incidental waste disposal, depending

14 on the nature of the waste and the planned disposal environment. Engineered barriers are

15 anthropogenic structures or devices intended to improve the disposal facility's ability to meet the

16 performance objectives in 10 CFR Part 61, Subpart C (10 CFR 61.2). In this document, the

17 term "engineered barrier" includes those anthropogenic barriers such as tanks, vaults, and other

18 components and systems that limit release of waste to the accessible environment (e.g., grout,

19 infiltration caps, erosion protection covers, slurry walls) or limit inadvertent intrusion into the

20 waste. In the performance assessment modeling, DOE may decide not to take credit for all

21 engineered barriers present at the site. Each type of engineered barrier will have a timeframe

22 over which it will be designed to perform its intended functions (e.g., the design life), which

23 should be justified for the specific application of the barrier. There is significant uncertainty in

24 the ability of engineered barriers to achieve the design goals when modeled performance is

25 needed for long periods of time, and the uncertainties tend to increase with increasing

26 performance periods. An engineered barrier with design goals significantly exceeding relevant

27 experience (either in degree or duration) should have a commensurately higher amount of

28 model support that the barrier will likely achieve the design goals. Regardless of the model

29 support, analysis should be performed to understand the impacts if the barrier does not achieve

30 its design goals.

31

32 4.3.2.1 Areas of Review

33

34 This section focuses on the engineered barriers DOE proposed in its waste determination and

35 performance assessment. Improvement in the disposal facility performance can be achieved by

36 limiting the amount of water that contacts the wasteform, reducing the transport of radionuclides

37 within and from the site, and providing shielding from direct exposure, among other functions.

38 In particular, the review should focus on those aspects of the engineered barriers that are most

39 critical to meeting the performance objectives in 10 CFR Part 61, Subpart C. Section 4.6

40 provides guidance to evaluate the risk significance of barriers in the context of estimated

41 disposal facility performance.

42

43 4.3.2.1.1 Features and Dimensions of the Engineered Barrier System(s)

44

45 The reviewer should evaluate the descriptions of the engineered barriers proposed for the site.

46 The description of the engineered barriers will typically include the geometry, dimensions,

47 materials, functionality, design goals, and pertinent degradation mechanisms. Engineered

48 barriers may be above grade or below grade and may be designed for physical (e.g., vaults,

49 covers, erosion control barriers, drainage systems, containers, backfill, or infill) or chemical

50 control (e.g., pH buffers, oxygen getters). Radionuclide mobility through engineered barriers

4-21
1 may be affected by both the physical state of the barrier (e.g., low permeability and porosity)

2- and chemical phenomena such as sorption, precipitation, coprecipitation, dissolution, and ion

3 exchange. The reviewer should evaluate the potential for the physiochemical conditions

4 produced by the barriers to limit radionuclide mobility (e.g., by limiting flow and maintaining

5 reducing water compositions).

6

7 The reviewer should examine the design of the waste disposal system. The design should

8 specify the dimensions, orientation, and compositions of the engineered barriers. Specifically,

9 the reviewer should examine figures and illustrations (e.g., cross sections that illustrate the

10 components of the engineered barrier system). Those portions of the design for which DOE

11 takes credit as engineered barriers should be identified. The reviewers should examine the

12 design functionality (e.g., limit water contact with the waste, limit erosion) and properties of the

13 engineered barriers (e.g., porosity, hydraulic conductivity, sorption coefficients). The reviewer

14 should evaluate the design goals and the description and analysis of pertinent degradation

15 mechanisms to verify that the engineered barrier will likely be able to achieve the design goals.

16

17 4.3.2.1.2 Performance of Engineered Barriers

18

19 The effectiveness of engineered barriers, such as engineered caps and reducing grouts, is

20 expected to diminish over long time periods. Combinations of physical and chemical processes

21 will result in changes to the original barriers that may reduce their effectiveness (e.g., formation

22 of cracks in grout, concrete, or clay). The reviewer should examine the assumptions of barrier

23 degradation and the justification and technical bases for the time period for which DOE takes

24 credit for the effectiveness of the barriers.

25

26 For engineered barriers such as engineered caps that are designed to reduce infiltration

27 through the wasteform, the reviewer should evaluate the technical basis used to support

28 estimates of physical durability with time. Conceptual models (e.g., of fracturing of a cap or

29 wasteform that may affect the physical durability) should be supported by test results that are

30 appropriate for the materials to be used in the barrier. Because of the long time periods

31 involved, the reviewer should also evaluate information provided on the impact of biointrusion

32 (e.g., root penetration, burrowing animals) on engineered barrier performance. To estimate

33 evapotranspiration cover performance, it is important to consider processes that can affect the

34 ability of the plant community to transpire water, including but not limited to variation in weather

35 conditions, biotic processes, the formation of discrete pathways, disease, land use, and

36 disruptive events such as fires. The storage capacity of the cover should be designed

37 considering the performance period and requirements for moisture management at the site. In

38 addition, the dynamics of vegetation succession on the engineered cover should be considered

39 for the period of performance.

40

41 The reviewer should evaluate the technical basis provided to support DOE estimates of the

42 chemical performance of engineered barriers and wasteforms (e.g., reducing grout, saltstone)

43 during the performance period. For example, for a reducing cementitious wasteform the

44 reviewer should examine the analysis of the effects of temporal changes in pH and redox in

45 engineered materials (such as concrete) on source term Kd values, which may determine the

46 release rates of radionuclides. The persistence of the chemical durability of a barrier may be

47 directly related to the physical properties of the barrier. Information should be provided for the

48 reviewer to evaluate the coupling of physical and chemical degradation mechanisms of barriers.

49

4-22
1 For erosion control barriers (see Section 7), the reviewer should consider rock durability,

2 gradation, cover design, stability calculations for the top slope, side slope, and apron for any

3 cover, and other considerations that are important to erosion control system performance.

4

5 4.3.2.1.3 Integration and Interaction of Materials

6

7 The assessment of the effectiveness of each engineered barrier may need to account for the

8 interaction with other engineered barriers that may be used (e.g., durability of a cement barrier

9 may be affected by corrosion of an exposed steel liner that transects the cement barrier).

10

11 The reviewer should evaluate the compositions of the materials proposed for the engineered

12 barriers, the spatial location and distribution of the materials, and potential interactions both

13 among the engineered materials and with the natural system. For example, the amount of

14 water that penetrates the engineered barriers, the composition of the penetrating water, and the

15 composition of the water after interaction with the engineered barriers and wasteforms will affect

16 the leaching of radionuclides from the wasteforms and the near-field transport of radionuclides.

17

18 4.3.2.1.4 Construction Quality and Testing

19

20 The reviewer should examine the parameters chosen to represent the engineered barriers in the

21 performance assessment and compare those parameters to the quality requirements for the

22 design and test results of the engineered barriers. Selection of deterministic parameters or

23 parameter distributions should account for expected variability in materials, construction

24 implementation, and other uncertainties (e.g., interactions among materials and with the natural

25 system; the properties of as-emplaced materials). The reviewer should evaluate tests or

26 measurements used to support parameter values implemented in the performance assessment

27 (e.g., permeability and hydraulic conductivity testing). The reviewer should evaluate information

28 developed (or the plans to develop information) to demonstrate that as-emplaced properties are

29 consistent with laboratory-measured or design values.

30

31 4.3.2.1.5 Modeling of Engineered Barriers

32

33 The objective of engineered barrier analysis is to establish model representations of the

34 physical dimensions and characteristics of designed engineered features and to determine the

35 ranges of parameter values that would reasonably represent the behavior of the features with

36 the passage of time (NRC, 2000). In developing the performance assessment model for the

37 engineered barriers, DOE should present a design concept that includes information on spatial

38 relationships among physical components (e.g., the layout and physical dimensions of a vault or

39 cover system) and the physical distribution of various types of materials that are used in the

40 facility. Not all design features will necessarily be reflected in the performance assessment as

41 engineered barriers, but DOE should identify and include those components (e.g., engineered

42 caps) and associated materials (e.g., reducing grout) that are most important to demonstrating

43 compliance with the performance objective. The reviewer should examine those DOE-identified

44 components and materials and evaluate how they are represented in the performance

45 assessment modeling of the engineered barriers.

46

47 The reviewer should evaluate the degradation mechanisms associated with the engineered

48 barriers. Barriers may degrade from internal (e.g., interaction between incompatible materials,

49 interaction with the waste) or external processes (e.g., interaction with biota, erosion, leaching

50 by infiltrating water, disruptive processes such as seismically induced cracking). Analysis of a

4-23
1 barrier system should be, performed in an integrated manner because of the potential synergism

2 between degradation mechanisms. If the analysis is performed assuming the degradation

3 mechanisms are independent, the reviewer should evaluate the information to determine

4 whether adequate basis has been provided for the analysis approach (e.g., assuming the

5 degradation mechanisms can be evaluated as independent), which may include demonstrating

6 that the degradation analysis was reasonably conservative.

7

8 The reviewer should evaluate how DOE has considered the interaction of the components of the

9 engineered system and materials in the engineered barrier system. Factors that may need to

10 be considered include (1) compatibility among materials that may come in contact with each

11 other; (2) the manner in which construction may affect system behavior (e.g., construction joints,

12 changes in geometry, penetrations); (3) the effect that failure of a design feature or some

13 portion of an engineered barrier would have on the overall behavior of the system; and (4) how

14 the degradation of material properties affects barrier performance over time (NRC, 2000). The

15 DOE performance assessment should account for relevant materials and conditions that could

16 affect release from the waste disposal system-over the service life of the engineered barriers.

17

18 The reviewer should evaluate information that DOE uses to 'support the model estimates of

19 engineered barrier performance. This may include site-specific test information, previous

20 experience with similar systems, process modeling of barrier component 'performance

21 (e.g., detailed models of an infiltration cap), field studies, natural analogs, independent peer

22 review, or additional sources of relevant information. DOE may also use preliminary analyses to

23 assess the need for additional performance enhancements that may, in turn, dictate the use of

24 improved or additional engineered barrier systems (e.g., the performance modeling of reinforced

25 concrete vaults, soil covers). In this manner, design features and the design of engineered

26 barriers would evolve from important conclusions developed with initial performance

27 assessment results. Information from these types of analyses may be factored into monitoring

28 activities (see Section 10).

29

30 4.3.2.2 Review Procedures

31

32 To review models of engineered barriers, consider the degree to which DOE relies on

33 engineered barriers and near-field radionuclide transport to demonstrate compliance with

34 10 CFR Part 61, Subpart C, and the contribution of the engineered barriers to system

35 performance (see Section 4.6). For example, if DOE relies on the engineered barriers to

36 significantly reduce the mass flux of waste from the disposal system compared to that provided

37 by the waste and natural system, then perform a detailed review of the modeling. On the other

38 hand, if DOE demonstrates the model to have a minor impact on the dose of the receptor, then

39 conduct a simplified review to determine whether the calculations of barrier performance have

40 been appropriately implemented in the performance assessment. In a risk-informed,

41 performance-based review, some of the review procedures may not be necessary when

42 conducting a simplified review for those models that have a minor impact on performance. The

43 reviewer should perform the following procedures:

44

45 * Apply the general review procedures found in Section 4.2 to the assessment of

46 engineered barrier performance.

47

48 - Evaluate the descriptions of the engineered barriers proposed for the site, and determine

49 whether the descriptions adequately describe the physical and chemical characteristics

50 of the barriers.

4-24
1 * Confirm that the design for the engineered barriers adequately provides the dimensions,

2 orientation, and compositions of the barriers. Specifically, the reviewer should examine

3 figures and illustrations (e.g., cross sections that illustrate the components of the

4 engineered barrier system).

5

6 Assess whether the descriptions of the engineered barriers adequately detail the design

7 features, the functionality (e.g., ability to limit water contact with the waste), and

8 properties (e.g., porosity, hydraulic conductivity, sorption coefficient) of the barriers.

9

10 Verify that an adequate description of the materials and methods used to construct the

11 engineered barriers has been provided.

12

13 Ensure that the description of degradation mechanisms and physical and chemical

14 phenomena that may affect the degradation of the engineered barriers is clear and

15 complete and any synergisms between mechanisms are described. For example,

16 degradation mechanisms for a cementitious barrier may include sulfate and magnesium

17 attack, carbonation, reinforcement corrosion, leaching, alkali/aggregate reactions,

18 freeze-thaw cycling, cracking (e.g., thermal, seismic-induced), and shrinkage.

19

20 - Examine the assumptions about how the barriers will degrade and the justification and

21 technical bases for the time period for which DOE takes credit for the effectiveness of

22 the barriers.

23

24 - Verify that mathematical models for the degradation of engineered barriers and

25 near-field transport of radionuclides are based on similar environmental parameters,

26 material properties, and assumptions.

27

28 - Evaluate the technical bases used to support estimates of physical durability of

29 engineered barriers with time. For example, ensure that conceptual models for

30 fracturing of a wasteform or clogging of a drainage layer in an engineered cap are

31 supported by test results that are appropriate for the materials used in the barrier.

32

33 - Evaluate the technical bases DOE provided to support estimates of the chemical

34 performance of engineered barriers and wasteforms (e.g., reducing grout, saltstone)

35 during the performance period.

36

37 - Ensure that DOE has evaluated potential changes in pore water chemistry (e.g., pH,

38 redox) with time, taking into account the amount of water expected to pass through the

39 wasteform and the proposed grout formulation (e.g., novel ingredients, cement fraction).

40

41 Ensure that DOE has adequately considered the potential for oxidizing conditions in the

42 disposal system (e.g., oxidation by aqueous or gaseous transport into the wasteform or

43 oxidation of engineered materials by interaction with the waste).

44

45 - Ensure that DOE has adequately characterized and considered the potential impact of

46 the waste on cementitious material degradation and radionuclide release (e.g., waste

47 components may increase Eh or decrease pH of the grout that is in close proximity to

48 the waste).

49

4-25
1 Evaluate the potential for the physicochemical conditions the barriers produced to limit

2 radionuclide mobility (e.g., by maintaining reducing water compositions).

3

4 Evaluate the impacts of biointrusion (e.g., root penetration, burrowing animals) on

5 engineered barrier performance, and if appropriate, verify that the impacts have been

6 appropriately represented in the performance assessment modeling.

7

8 Evaluate features, events, and processes that can affect the ability of the plant

9 community to transpire water for evapotranspiration barriers, including but not limited to

10 variability in weather conditions, biotic processes, discrete pathways, disease, land use,

11 and disruptive events such as fires.

12

13 - Ensure the storage capacity of evapotranspiration covers has been designed

14 considering the performance period and requirements for moisture management at

15 the site.

16

17 - Evaluate the compositions of the materials proposed for the engineered barriers and

18 potential interactions among the materials and with the natural system. Ensure that

19 interactions that could affect barrier degradation have been adequately represented in

20 the performance assessment.

21

22 Ensure that DOE has adequately characterized and considered the potential impact of

23 the service environment on cementitious material degradation and radionuclide

24 release. Ensure the degradation mechanisms are consistent with site conditions

25 (e.g., biodegradation [may affect C02 concentrations]; concentrations of

26 sulfate, magnesium, chloride, oxygen, and C02; hydrological cycle and potential for

27 flooding and wet/dry cycling).

28

29 Ensure that DOE has adequately characterized and considered the effects of grout

30 components on cementitious material degradation and radionuclide release (e.g., effect

31 of supplementary grout components on pH and Eh evolution and presence of deleterious

32 species that may enhance cementitious material degradation or radionuclide release).

33

34 Review grout formulations and associated design specifications for consistency with

35 performance assessment assumptions regarding the expected performance of the

36 grouts (e.g., material property assignment [hydraulic conductivity] are consistent with

37 design specifications [water-to-cement ratio]).

38

39 Review grout placement information and controls or procedures used to ensure the

40 quality of as-emplaced grout is consistent with performance assessment assumptions.

41

42 Ensure relevant features, events, and processes affecting cementitious material

43 degradation, including spatial and temporal transients, are adequately considered

44 (e.g., alternating freeze/thaw, wet/dry cycling, flooding, moisture profiles and distribution,

45 climate change, land use).

46

47 Examine the parameters chosen to represent the engineered barriers in the performance

48 assessment. Compare those parameters to the quality requirements for the design and

49 to the results of tests or measurements of the engineered barrier properties.

50

4-26
1 Evaluate any testing that supports parameter values used in the performance

2 assessment (e.g., permeability and hydraulic conductivity testing), and determine

3 whether the test conditions were representative of the expected environmental

4 conditions for the barrier. Determine whether test results have been interpreted

5 appropriately (e.g., that leach test results have been corrected for changes in surface

6 area-to-volume ratios).

7

8 Examine the engineered barrier components and materials DOE identified, and evaluate

9 how they are represented in the engineered barrier performance assessment.

10

11 Evaluate the engineered barrier component modeling in the performance assessment.

12 Examine modeling of interactions between materials, construction effects (e.g., joints,

13 penetrations), potential effects of failure of design features, and degradation of material

14 properties over time.

15

16 - Evaluate the parameters used to describe flow through and out of the engineered

17 barriers, and confirm that they sufficiently bound the flow through the barriers.

18

19 * Evaluate information used to support the engineering barrier analysis. Examine site

20 specific tests, information on previous experience with similar systems, process models

21 of barrier component performance (e.g., detailed modeling of an infiltration cap), natural

22 analogs, independent peer review, or plans to develop additional model support for

23 engineered barrier system performance.

24

25 Ensure uncertainties in cementitious material degradation were adequately considered

26 and propagated through the performance assessment model.

27

28 4.3.3 Source-Term/Near-Field Release

29

30 The modeling of the source term can be one of the most important determinants of the predicted

31 overall disposal facility performance. The source term is the inventory, physical and chemical

32 characteristics, and other properties of the waste used to estimate release rates. Source-term

33 modeling estimates the partitioning in and release of radionuclides from the disposal unit.

34 Releases generally occur by advective or diffusive mechanisms, although direct release

35 mechanisms may be possible (e.g., biointrusion, erosion). The near field is generally defined as

36 the area surrounding the waste that may have moisture flow and chemical conditions (e.g., due

37 to the presence of the waste or engineered barriers) significantly different from the natural

38 system in which the waste disposal facility is located.

39

40 The source-term analysis calculates radionuclide releases from the disposal facility as a

41 function of space and time. These radionuclide release rates can then be used as input for

42 transport models that estimate offsite releases from the facility. Radionuclides are typically

43 released from the waste or wasteform and transported in the aqueous phase, but release of

44 certain radionuclides (e.g., C-14, H-3, Kr-85) can occur in the gaseous phase. Although liquid

45 releases can be significantly constrained by limitation of the flux of water entering a disposal

46 unit, gaseous releases are relatively unconstrained because of the significantly higher rates for

47 gaseous diffusion and advection compared with diffusion and advection of radionuclides in the

48 liquid phase. Gaseous advection and diffusion may become limited at high liquid saturations.

49 Gaseous and liquid releases will often be analyzed separately in performance assessment

50 analyses because of the significant differences in the nature of the releases, and because in

4-27
1 many cases, the limited inventory associated with the gaseous release and limited resultant

2 impact on performance readily lends itself to a simple bounding analysis.

3

4 4.3.3.1 Areas of Review

5

6 This portion of the review focuses on the assumptions, data, and models (conceptual and

7 computational) DOE used to develop the source term for the performance assessment model.

8 Source-term analyses calculate releases of radionuclides as a function of time and space. The

9 release rates are used as inputs to radionuclide transport models. The complexities of most

10 sites and proposed disposal approaches usually result in source-term analyses being

11 developed on a site-specific basis. Source-term modeling is commonly implemented in

12 performance assessment models with a simplified representation of both the distribution of the

13 radionuclide inventory and the physiochemnical processes associated with the partitioning of

14 radionuclides between the materials and physical phases in the disposal unit. The simplified

15 representation is abstracted for inclusion in mathematical and computer model representations

16 of the real system. The source-term model should include the effects of the degradation of the

17 wasteform and the engineered barriers, as appropriate. For example, cracking of a grouted

18 wasteform over time may lead to advective release, rather than diffusive release. In another

19 example, chemical barriers, such as reducing grout formulations, may lose their effectiveness

20 over time. The release models used in the source-term analysis should reflect the temporal

21 changes to the disposal facility.

22

23 Representing the source term in a performance assessment involves generalizing system

24 details into more simplified conceptual izations that can be modeled. Whereas the source-term

25 abstractions must adequately represent the features and processes significant to disposal

26 system performance, the abstractions must not simplify system behavior to the extent that

27 disposal system performance is significantly underestimated or unrealistically overestimated.

28

29 4.3.3.11.1 Inventory of Radionuclides in Waste

30

31 The inventory of radionuclides in the waste is used to assess the removal of highly radioactive

32 radionuclides to the maximum extent practical (see Section 3) and the concentration limit criteria

33 related to 10 CFR 61.55 (whether the waste exceeds the concentration limits for Class C waste)

34 (see Section 3.5). The inventory also provides the radionuclide inventory for which release

35 rates are estimated with source-term calculations. The radionuclide inventory evaluated in this

36 portion of the review should be consistent with radionuclide inventory used to assess.

37 compliance with the site-specific radionuclide removal and concentration limit criteria described

38 in Section 3 of this guidance document.

39

40 The reviewer should evaluate the description of the radionuclide inventory in the waste. All

41 radionuclides (particularly highly radioactive radionuclides) should be described by volume,

42 concentration, and location within the disposal system. Radionuclides with relatively high

43 solubility, low sorption, and high dose conversion factors and/or significant ingrowth are of

44 particular significance. Additional detailed guidance for reviewing radionuclide inventory is

45 provided in Section 3.1.

46

4-28
1 4.3.3.1.2 Degradation and Release From Wasteforms

2

3 The reviewer should evaluate the descriptions of the wasteforms and the representation of the

4 wasteforms in the source-term modeling. Waste is almost exclusively stabilized in a solid form

5 to reduce its mobility and dispersibility into the environment. Wasteforms can include

6 cement-solidified waste, activated metal, glass, bulk waste, and others. Wasteforms limit

7 aqueous and gaseous releases once the engineered barriers degrade. Different wasteforms

8 will have different release processes and degradation mechanisms. For example, a high-quality

9 cement-solidified wasteform may be dominated by diffusional release, whereas a glass

10 wasteform may release radionuclides mainly by dissolution of the glass matrix. In addition, the

11 release mechanisms may change during the period of performance (e.g., while diffusion may

12 dominate release from high-quality, intact cementitious wasteforms, advection may dominate

13 release from degraded or lower quality cementitious wasteforms). These differences can be

14 very important in evaluating the appropriateness of source-term models.

15

16 The reviewer should evaluate the wasteform degradation processes DOE considered and

17 evaluate how the processes are incorporated in the source-term model. Wasteform degradation

18 modes may include leaching, dissolution, and other chemical reactions with groundwaters.

19 Cementitious wasteform performance may be reduced by chemical processes such as sulfate

20 attack or carbonation or by physical processes such as cracking caused by settling or seismic

21 activity and damage by reinforcement corrosion. Degradation of the wasteform can increase

22 contact of water with the waste and can provide shortened and more permeable paths for

23 radionuclide release. Degradation can also change the type of mechanisms that dominate

24 release from the wasteform (e.g., cracking may enhance advective release).

25

26 4.3.3.1.3 Source-Term Models

27

28 The reviewer should evaluate the source-term models used. Source-term models are ultimately

29 used to estimate release rates from the disposal facility; many intermediate processes may be

30 simulated to estimate release rates. Release rates can be affected by the performance of

31 engineered barriers, as well as the specific physical and chemical properties of the disposal

32 system and the interaction of the disposal system with the natural environment (e.g., infiltrating

33 water that is high in magnesium may have an effect on cement performance). Some disposal

34 plans will require detailed consideration of these processes and conditions, whereas simplified

35 analyses may be justified for other sites and disposal options. Sites for which the source term

36 models need to be considered carefully are sites for which there is significant credit taken for

37 some aspect of the source-term modeling (i.e., low solubility limits) and for which there is limited

38 model support. Sites for which a simpler analysis is acceptable are sites for which the simple

39 analysis can be shown to be clearly conservative or for which the simple model is well

40 supported by multiple lines of evidence, including field tests that show the simple model

41 accurately represents or bounds field results. The information reviewed as part of the

42 evaluation performed for Section 4.6 should help focus the reviewer on the key aspects of the

43 disposal facility performance and should provide information to determine the importance of

44 source-term modeling and near-field release.

45

46 There are generally four types of aqueous radionuclide releases: (1) rinse release,

47 (2) diffusional release, (3) dissolutional release, and (4) partitioning release. Rinse release

48 refers to washing of radionuclides from the surface of a wasteform by infiltrating groundwater.

49 Diffusional releases occur when radionuclide movement through a porous wasteform (e.g., a

50 cement-stabilized wasteform) is limited by diffusion. Radionuclide releases resulting from

4-29
1 corrosion of an activated metal or dissolution of glass wasteforms are examples of dissolutional

2 release. Partitioning release results when radionuclide release is described by a characteristic

3 Kd or other parameter that distributes activity between phases in the system (e.g., between the

4 wasteform and liquid contacting the wasteform). Solubility limits may be very important in

5 estimating release rates with source-term models, particularly for extreme chemical

6 environments (e.g., high pH associated with pore fluids of cementitious wasteforms or

7 cementitious engineered barriers).

8

9 4.3.3.1.4 Chemical Environment

10

11 The reviewer should evaluate the chemical environments of the system. There may be spatial

12 variation in the chemical environments within the system, and they may also change over time.

13 The reviewer should evaluate the chemical environment for consistency with the degradation

14 of wasteforms and engineered barriers that may affect the chemical environment (see

15 Section 4.3.3.1.2). The chemical environment may be important for estimating the lifetime of

16 engineered barriers. The chemical environment is important to estimating radionuclide release

17 from the wasteform and transporting released radionuclides within and from the disposal facility.

18 The chemical environment is particularly important if DOE relies on solubility limits or retardation

19 of radionuclides within the disposal unit to satisfy the performance criteria. The site-specific

20 chemical environment of a disposal facility may include engineered components designed to

21 have performance-enhancing chemical properties.

22

23 4.3.3.1.5 Gaseous Releases

24

25 The reviewer should evaluate the potential for gaseous releases because some radionuclides

26 may be released in a gaseous form (e.g., C-14, tritium). The timing and rate of a gaseous

27 release will depend on the engineered barrier design. After release from the engineered

28 barriers, gaseous radionuclides can move by advection and diffusion through overlying soil or

29 other materials to reach the atmosphere. Some gaseous releases may interact with

30 components of the soil and groundwater and are not strictly controlled by advection and

31 diffusion. Gaseous releases are likely to have limited impact on most waste determinations due

32 to limited inventory, and they may be handled with relatively simple bounding calculations

33 (e.g., a box model). The reviewer should evaluate assumptions regarding the effects of

34 saturation on diffusivities and chemical and biological retention.

35

36 4.3.3.2 Review Procedures

37

38 Review the source-term modeling considering its importance to disposal facility performance as

39 evaluated in accordance with Section 4.6. If DOE relies on the source term to significantly

40 reduce or mitigate radiological impacts, then perform a detailed review of the source-term

41 modeling. If, on the other hand, DOE demonstrates that this abstraction has a minor impact on

42 the dose, then conduct a simplified review focusing on determining whether the calculations

43 have been properly implemented in the performance assessment model. The reviewer should

44 evaluate the consistency of source-term information with information provided on engineered

45 barrier systems (Section 4.3.2) and on climate and infiltration (Section 4.3.1). The reviewer

46 should verify that source-term modeling has been appropriately integrated with other models in

47 the performance assessment. In a risk-informed, performance-based review, some of the

4-30
1 review procedures may not be necessary when conducting a simplified review for those

2 models that have a minor impact on performance. The reviewer should perform the

3 following procedures:

4

5 Apply the general review procedures found in Section 4.2 to source-term and near-field

6 release modeling.

7

8 Evaluate the description of the radionuclide inventory in the waste. Confirm that

9 radionuclides are described by volume, concentration, and location within the disposal

10 system. Information evaluated should be consistent with that considered under

11 Section 3.1 of this guidance document.

12

13 - Examine the description of the wasteform, and verify that the implementation of the

14 wasteform in the source-term modeling for the performance assessment is consistent

15 with the description.

16

17 - Examine the DOE description of environmental conditions expected inside failed

18 engineered barriers and within the disposal facility environment surrounding the

19 engineered barriers. Verify that the ranges in conditions are described in sufficient detail

20 and ranges of chemical conditions have been appropriately accounted for in the

21 performance assessment.

22

23 - Evaluate potential changes to the chemical environment of the disposal system over

24 time and resulting changes in degradation of the engineered barriers and wasteforms

25 that may affect the source term and near-field transport. Verify that these potential

26 changes are consistent with the engineered barrier performance information in

27 Section 4.3.2 of this guidance document. Verify that the uncertainty in changes in the

28 chemical conditions has been propagated in the performance assessment, if needed.

29

30 Evaluate radionuclide release rate test programs and other sources of data supporting

31 the durability of and release rates from the wasteforms. Verify that the programs or data

32 sources provide sufficient and suitable data for use in the source-term abstraction.

33 Evaluate the justification for the use of test results not specifically collected from the site

34 of interest.

35

36 Evaluate the parameters used to describe flow through and out of the wasteform, and

37 confirm that they sufficiently bound the flow through the wasteform.

38

39 Evaluate the potential for gaseous releases of radionuclides. Verify that potential

40 gaseous releases are consistent with the design of the engineered barriers evaluated in

41 Section 4.3.2.

42

43 Evaluate assumptions regarding the effects of saturation on diffusivities and

44 chemical-and biological-mediated attenuation of potential gaseous releases.

45

46 Verify that DOE has adequately considered the uncertainties in the characteristics of the

47 natural system and engineered materials (e.g., the type, quantity, and reactivity of

48 material) in establishing initial and boundary conditions for conceptual models and

49 simulations of processes that affect the source term.

50

4-31
1 . Confirm that DOE has considered a range of wasteform degradation mechanisms that

2 are appropriate to the wasteform design and the physical and chemical conditions of the

3 disposal environment.

4

5 ° Confirm that data used to support the release rates were developed for materials and

6 conditions that encompassed the range of composition of the wasteform and the range

7 of chemical conditions of the disposal environment.

8

9 0 Ensure that changes in release mechanisms that could occur because of degradation of

10 the engineered barriers are appropriately accounted for (e.g., advective versus diffusive

11 release from degraded wasteforms).

12

13 * Ensure that moisture characteristic curve parameters used for near-field release

14 modeling are supported by empirical measurement or, if generic information is used, the

15 generic information is sufficiently conservative.

16

17 * Ensure that selection of Kd and solubility limit parameters used in the release model

18 adequately considered the material and chemical environment of the wasteform

19 (e.g., literature values relevant to ordinary cement may not be relevant to novel grout

20 formulations). Ensure that the effects of additives to the wasteform or barrier and the

21 presence of chelating agents in the waste have been considered in developing sorption

22 coefficients and solubility limits.

23

24 - Ensure that changes in the chemical condition of the wasteform with time (see

25 Section 4.3.3.1.2) are appropriately reflected in the release model (e.g., changes in Kd

26 and solubility limits with pH and redox conditions).

27

28 - If radionuclide release is based on linear partitioning, confirm that uncertainty in the Kd

29 values is reflected in the release model. In general, literature-based values are more

30 uncertain than site-specific values.

31

32 - Evaluate whether a solubility or partitioning release model is appropriate, and ensure

33 that it is representative or conservative.

34

35 - Ensure that the release model is calibrated to release test data, scaling for surface

36 area/volume, or that plans have been developed to acquire release rate data from

37 surrogate or actual wasteforms.

38

39 4.3.4 Radionuclide Transport

40

41 4.3.4.1 Areas of Review

42

43 This section focuses on evaluating transport of radionuclides beyond the engineered barriers.

44 Transport of radionuclides to the receptor group(s) may be through air, water, or biotic

45 pathways. The reviewer should consider the dimensions, locations, and spatial variability of the

46 various transport pathways as well as temporal variations during the compliance period. The

47 information reviewed for radionuclide transport should be consistent with the general

48 information evaluated using Section 1 of this guidance document.

49

4-32
1 4.3.4.1.1 Air Transport

2

3 The reviewer should evaluate the potential for airborne transport of radionuclides.

4 Reviewers evaluating airborne transport processes should consider both suspension of

5 radionuclide-bearing particulates and release of gaseous phase radionuclides (e.g., H-3, C-14,

6 Kr-85). The reviewer should evaluate the significance of dilution and dispersion of the airborne

7 radionuclides as they are transported in the atmosphere. Atmospheric transport of gaseous

8 radionuclides will be affected by the height of the release above ground level, the speed and

9 direction of the wind, atmospheric stability, and terrain. Radionuclide transport in the air will be

10 affected by rainfall and particulate settling.

11

12 Information DOE provided on airborne transport should be consistent with the site description

13 (e.g., meteorology) (Section 1.1.3), information on inadvertent intrusion (e.g., farming or drilling)

14 (Section 5), and climate (Section 4.3.1).

15

16 4.3.4.1.2 Surface Water Transport

17

18 -The reviewer should evaluate information provided on the potential for radionuclides to be

19 transported beyond the engineered barriers of the disposal facility via surface water. In most

20 cases, radionuclides will be transported from the waste disposal facility via other pathways

21 before being transported in surface water pathways because it is unlikely surface water will

22 directly intersect the waste disposal facility. Mechanisms for radionuclides to enter surface

23 waters include but are not limited to deposition after airborne transport, groundwater discharge,

24 and overland flow (e.g., associated with erosion). Information DOE provided on surface water

25 transport should be consistent with the information provided on climate and infiltration

26 (Section 4.3.1) and with the groundwater transport analyses for the site. The reviewer should

27 evaluate information provided on potential dilution of radionuclide concentrations by mixing of

28 disposal facility releases with surface waters. Typically, transport and residence times in

29 surface water systems are relatively short; therefore, dispersion and dilution are the dominant

30 processes that will mitigate the impact of contaminants released to most surface water bodies

31 such as streams and rivers. In addition to transport in the water itself, the reviewer should

32 consider the potential for radionuclide transport along with sediment suspended in the

33 surface water.

34

35 The reviewer should evaluate the chemistry of the surface water and host rocks and sediments

36 with respect to the potential for transport of radionuclides. The reviewer should evaluate the

37 effects of speciation of radionuclides (e.g., due to sorption, precipitation, ion exchange) in the

38 surface water if performance assessment modeling accounts for these processes. The reviewer

39 should evaluate information provided on flooding at the site (e.g., flood hydrographs, probable

40 maximum floods, maps of drainage basins, and maps of floodplains) (see Section 7).

41

42 4.3.4.1.3 Transport in the Unsaturated Zone

43

44 The reviewer should evaluate the information provided on the potential for radionuclides to be

45 transported beyond the engineered barriers of the site along groundwater pathways through the

46 unsaturated zone to the water table. Groundwater transport is among the most likely

47 processes for radionuclides to be transported from the engineered systems of the disposal

48 facility. The reviewer should examine the hydrogeologic data for the site, including the

49 stratigraphy and geologic structures (e.g., fractures) that may affect groundwater flow,

50 thicknesses of unsaturated strata, unsaturated hydraulic properties, depth to groundwater

4-33
1 (including any perched zones that may affect transport), and recharge to and discharge from the

2 site (including the potential effects of climate change). The reviewer should evaluate the

3 information provided on the potential for diffusion and mechanical dispersion during transport.

4 The reviewer should examine the significance of spatial variations in hydrogeologic properties

5 and examine the site design for information showing the positions of the engineered structures

6 and anthropogenic features (e.g., infiltration caps) that may influence the unsaturated zone

7 hydrology of the site. The reviewer also should evaluate the unsaturated zone flow and

8 transport models DOE used in its performance assessment and how output is passed from the

9 unsaturated zone flow and transport models to the saturated zone flow and transport models.

10 The staff should review the lengths of the flow paths in the unsaturated zone and evaluate the

11 travel times estimated in the analysis. Information DOE provided on groundwater transport

12 should be consistent with the information provided for the site description (Section 1.1.3),

13 climate and infiltration (Section 4.3.1), and surface water transport (Section 4.3.4.1.2).

14

15 The reviewer should evaluate the chemistry of the groundwater and host rocks and sediments

16 with respect to potential radionuclide transport, including potential changes to the chemistry of

17 the groundwater arising from interactions with the disposal system components and wasteform.

18 The reviewer should evaluate the effects of speciation of radionuclides in the groundwater

19 (e.g., due to sorption, precipitation, ion exchange, redox reactions) and the potential for colloid

20 facilitated transport. The information DOE provided should be consistent with the information

21 provided for the radionuclide inventory (Section 3.1), engineered barriers (Section 4.3.2),

22 source-term models (Section 4.3.3), and chemical environment (Section 4.3.3.1.4).

23

24 4.3.4.1.4 Transport in the Saturated Zone

25

26 The reviewer should evaluate the information provided on the potential for radionuclides to be

27 transported from the disposal facility along groundwater pathways in the saturated zone to

28 receptors. The reviewer should examine the hydrogeologic data for the site, including

29 information provided describing the aquifers, aquitards, and geologic features (e.g., fractures)

30 that may affect groundwater flow in the saturated zone. The reviewer should examine the

31 significance of spatial variations in hydrogeologic properties. The reviewer should evaluate

32 DOE estimates of recharge to and discharge from the aquifers; groundwater flow velocities,

33 gradients, and volumes; and ambient groundwater compositions. Water withdrawals and

34 pumping of saturated zone aquifers may affect flow, especially dilution of radionuclide

35 concentrations at the withdrawal point. The reviewer should evaluate information provided on

36 the potential for diffusion, mechanical dispersion, decay, and ingrowth during transport. The

37 reviewer should examine information provided on engineered structures (e.g., slurry walls) that

38 may affect saturated zone flow and transport at the site. The reviewer should evaluate the

39 saturated zone flow and transport models DOE used in the performance assessment. The staff

40 should review the lengths of the flow paths in the saturated zone and evaluate the travel times

41 estimated in the analysis. Information DOE provided on saturated zone groundwater transport

42 -should be consistent with the information provided for the site description (Section 1.1.3),

43 climate and infiltration (Section 4.3.1), surface water transport (Section 4.3.4.1.2), and

44 groundwater transport in the unsaturated zone (Section 4.3.4.1.3).

45

46 The reviewer should evaluate the chemistry of the groundwater and host rocks and sediments,

47 including potential changes to the chemistry of the groundwater arising from interactions with

48 the disposal system components and wasteform. The reviewer should evaluate the effects of

49 speciation of radionuclides in the groundwater (e.g., due to sorption, precipitation, ion

50 exchange, redox reactions) and the potential for colloid facilitated transport. The information

4-34
1 DOE provided should be consistent with the information provided for the radionuclide inventory

2 (Section 3.1), engineered barriers (Section 4.3.2), source-term models (Section 4.3.3), and

3 chemical environment (Section 4.3.3.1.4).

4

5 4.3.4.2 Review Procedures

6

7 Review the transport modeling considering the importance of this information to the

8 performance of the disposal facility as evaluated using the review procedures found in Section

9 4.6. If DOE relies on the transport modeling to significantly reduce or mitigate radiological

10 impacts, then the reviewer should perform a detailed review of the transport modeling. For

11 example, if DOE relies on retardation during transport to significantly delay the transport of

12 radionuclides, then the reviewer should perform a detailed review of the transport modeling. On

113 the other hand, if DOE demonstrates the transport modeling to have a minor impact on the

14 estimated radiological dose to the receptor, then the reviewer should conduct a simplified

15 review. In a risk-informed, performance-based review, some of the review procedures may not

16 be necessary to review models with a minor impact on predicted performance. The reviewer

17 should perform the following procedures:

18

19 * Apply the general review procedures found in Section 4.2 to the modeling of

20 radionuclide transport.

21

22 * Evaluate the potential for airborne transport of radionuclides. Verify that both

23 suspension of radionuclide-bearing particulates and release of gaseous phase

24 radionuclides are adequately considered. Examine the potential significance of dilution

25 and dispersion along the atmospheric transport path.

26

27 * Confirm that DOE has developed adequate technical basis for the dilution and

28 dispersion of radionuclides by mixing in surface waters during transport. Evaluate

29 whether adequate technical basis has been provided for incorporating the impact of

30 variability, especially temporal, in surface water dilution.

31

32 * Determine whether the development of models and data to represent the sorption and

33 speciation of radionuclides during surface water transport accounted for the chemistry of

34 the surface water and the mineralogy of sediments.

35

36 * Confirm that DOE has considered the potential for radionuclide transport along with

37 sediment moved by the surface water, in addition to transport in the water itself. Verify

38 that the models are consistent with information provided on flooding potential at the site.

39 For example, ensure that the potential for erosion and exhumation of wasteforms is

40 considered for those areas where site characteristics (e.g., gullies, steep terrain) indicate

41 that erosion is a significant process (see Section 7).

42

43 * Verify that the description of the hydrology, geology, climatology, geochemistry, design

44 features, and physical and chemical phenomena that may affect radionuclide transport

45 is adequate.

46

47 Verify that the assumptions in radionuclide transport modeling are clearly identified and

48 are consistent with the relevant data presented in the system description.

49

4-35
1 * Verify that DOE has adequately described groundwater flow directions and velocities

2 (horizontal and vertical) for each potentially affected aquifer. When applicable, the

3 groundwater hydrology should be described by making use of hydrogeologic columns,

4 cross sections, and water table and/or potentiometric surface maps.

5

6 ° Verify that the information on groundwater flow direction in each hydrological unit is

7 consistent with the information presented about receptor location reviewed in

8 Sections 1.1.3.1 and 4.1.1.4. Ensure that the groundwater flow directions are

9 consistent with placement of a member of the public at the point of highest exposure

10 outside of the disposal area to demonstrate compliance with 10 CFR 61.41.

.11

12 Confirm that DOE has sufficiently described numerical analysis techniques used to

13 characterize the unsaturated and saturated zones, including the model type, justification,

14 documentation, verification, calibration, and other associated information. In addition,

15 verify that DOE adequately described the input data, data generation or reduction

16 techniques, and any modifications to these data.

17

18 Evaluate the adequacy of the description of the effects of radionuclide

19 speciation on processes that could affect radionuclide transport in groundwater

20 (e.g., sorption, precipitation, ion exchange, redox reactions) and the potential for

21 colloid-facilitated transport.

22

23 Ensure that the selection of transport properties (e.g., Kd values) used in the unsaturated

24 and saturated zone transport models adequately considered the mineralogy and water

25 chemistry of the system.

26

27 Evaluate the technical basis for the transport parameters and determine whether DOE

28 modeling assumptions for radionuclide. transport are appropriate. For example, confirm

29 that the selected geochemical parameters (e.g., pH, redox, sorption coefficients) are

30 consistent with the expected chemical environment at the site.

31

32 Evaluate whether chelating agents or other organic solvents have been used at the site

33 and released to the environment. If chelating agents have been released, evaluate how

34 they have been considered in selecting transport properties and whether the model

35 support adequately constrains the impact of chelating agents on radionuclide transport.

36 Evaluate the technical basis on whether the impact of chelating agents on transport

37 properties is expected to persist when radionuclides may eventually be released.

38

39 Confirm that DOE has used flow and transport parameters that are based on techniques

40 that may include laboratory experiments, field measurements, information from

41 comparable sites, and process-level modeling studies conducted under relevant

42 conditions. Confirm that site-specific information was used, when available, to develop

43 transport parameters and models.

44

45 - Ensure that adequate descriptions are provided of how flow and transport data were

46 used, interpreted, and incorporated into the performance assessment parameters.

47

48 - Ensure that DOE provided hydrologic properties (e.g., moisture characteristic curve

49 parameters) for modeling unsaturated zone flow that are supported by empirical

50 measurement. If generic information is used, ensure that the properties are sufficiently

4-36
1 conservative. Verify that the information is consistent with related hydrogeologic data for

2 the site, including observed spatial variability in the hydrologic properties.

3

4 * Verify that parameter values for processes such a's matrix diffusion, dispersion, and

5 groundwater mixing are based on reasonable assumptions about climate, aquifer

6 properties, and groundwater volumetric fluxes.

7

8 * Confirm that the uncertainties in transport properties (e.g., Kd values) are reflected in the

9 unsaturated and saturated zone transport models. In general, literature-based values

10 are more uncertain than site-specific values.

11

12 * Ensure that limitations and uncertainties of the Kd model have been adequately

13 considered if a Kd model is used to represent radionuclide transport and if the transport

14 submodel has been identified as having a significant effect on dose, results (e.g., by

15 significantly delaying radionuclide arrival and resulting in significant decay). The

16 reviewer may consider "Understanding Variation in Partition Coefficient, Kd, Values"

17 (EPA, 1999).

18

19 * Examine the results of DOE field transport tests or observations of leaks and spills, and

20 verify that the performance assessment model results are consistent with the field

21 experiments or observations, or confirm that an adequate technical basis has been

22 provided to explain any significant differences. For example, the performance

23 assessment transport models should provide results that are consistent with the

24 transport of existing contaminant plumes as observed through environmental monitoring.

25

26 * Ensure that the output from the unsaturated zone flow and transport model is consistent

27 with the input into the saturated zone flow and transport model.

28

29 - If the water table is shallow and the unsaturated zone flow paths are short (less than 5 m

30 [16 ft]}, ensure that DOE has evaluated the impact of water table fluctuation and

31 provided adequate technical basis that fast pathways that would significantly affect the

32 travel time through the unsaturated zone are not present .

33

34 * Ensure that adequate, technical basis is provided represent the ingrowth of daughter

35 radionuclides in the modeling of radionuclide transport. Many computer codes assign

36 the same transport properties to the daughter radionuclides that ingrow from parents

37 during transport. If significant ingrowth can occur, the transport of daughters that are

38 more mobile than their parent radionuclide may be significantly underestimated.

39

40 * For those radionuclides for which transport in groundwater is important to estimating the

41 dose to receptors, verify that adequate model support has been provided for the

42 transport modeling such. as comparison to laboratory exper iments, field measurements,

43 observations of leaks and spills, process-level modeling studies conducted under

44 relevant conditions, natural analogs, and independent peer review. For observational

45 types of information such as monitoring of leaks and spills, confirm that the conditions of

46 the leak or spill are similar to the modeled conditions (e.g., mineralogy, pore water

47 chemistry, hydraulic properties).

48

49 * Ensure the modeling of saturated transport is consistent with site-specific information

50 about the hydrological units (e.g., information reviewed according to Section 1.1.3.5).

4-37
1 Ensure that the modeling of any units identified as aquitards is consistent with

2 information about the spatial variability of the unit. The reviewer should determine that

3 the basis for the absence of any fast pathways through the unit (e.g., areas where the

4 unit pinches out or becomes thin or has high-permeability features such as sand lenses)

5 is adequate. In some cases, it may be conservative to assume an aquitard is intact. As

6 necessary, the reviewer should consider the resolution of the characterization

7 techniques used to identify fast pathways in aquitards.

8

9 To the extent practical, consider other relevant sources of information, such as

10 characterization and modeling performed for existing contamination or other waste

11 disposal facilities at the DOE site, that may support or refute the hydrogeologic

12 conceptual model, analysis, and modeling DOE provided for the waste determination.

13

14 - Ensure that alternative modeling approaches, if applied, are consistent with available

15 data and current scientific knowledge.

16

17 - Confirm that outputs of radionuclide transport models used in the performance

18 assessment reasonably agree with or bound the results of corresponding process-level

19 models, empirical observations, or both.

20

21 - Verify that procedures to construct and test the mathematical and numerical models of

22 radionuclide transport are documented and that the procedures are based on modeling

23 approaches that have been accepted by the scientific community.

24

25 4.3.5 Biosphere Characteristics and Dose Assessment

26

27 For the purpose of this review, the biosphere is the physical environment accessed by the

28 receptor in the dose assessment. The dose assessment is that portion of the performance

29 assessment model that calculates dose to the receptor from radionuclides transported from the

30 disposal site to the biosphere. The dose assessment includes all the applicable local fate and

31 transport pathways within the biosphere that culminate in exposure to the receptor

32 (e.g., irrigation of soils with contaminated groundwater, plant and animal uptake, consumption

33 of local food products). Because offsite receptor locations can have different characteristics

34 from the disposal site and some specialized information may be needed to support the dose

35 assessment, the biosphere characteristics must be reviewed to verify that the inputs and

36 assumptions have adequate technical basis.

37

38 4.3.5.1 Areas of Review

39

40 Input parameters for dose assessments may be generally classified as behavioral, metabolic, or

41 physical. Behavioral parameters collectively describe the behavior hypothesized for the

42 potentially exposed individual; and the behavior is normally consistent with local practices

43 (e.g., time spent gardening, vegetable consumption rates). Metabolic parameters also describe

44 the exposed individual, but generally address involuntary physiological characteristics of the

45 individual (e.g., breathing rates, factors converting intake of unit activity to dose [by

46 radionuclide]). Physical parameters collectively describe the physical characteristics of the site

47 (e.g., geologic, hydrologic, geochemical, ecological, and meteorologic inputs). This section

48 focuses on the review of the physical, behavioral, and metabolic input parameters used in the

49 dose assessment modeling for the performance assessment.

4-38
1 4.3.5.1.1 Exposure Pathways and Dose Modeling

2

3 The reviewer should evaluate information provided to ensure that models of radionuclide

4 transport via groundwater, surface water, and air pathways are properly integrated with dose

5 assessment models. For example, groundwater may be used as a source of drinking water

6 (both human and livestock), to irrigate crops, and as a primary source of water for meeting

7 various domestic, commercial, and industrial needs. Therefore, scenarios involving

8 radionuclides transported in groundwater may involve dose modeling that includes'direct human

9 ingestion of contaminated water and transfer of contaminants to crops and livestock.

10 Furthermore, partitioning of contaminants to soils can result in inhalation of radionuclides either

11 as particulates suspended in air or as gases emanated from the soils. Direct exposure to

12 contaminated soils is also a potentially applicable dose pathway. Surface water transport can

13 lead to exposure pathways similar to groundwater if the surface water is used as a primary

14 source of water for municipal needs. Direct exposures can occur from contaminated surface

15 water during recreational activities such as bathing or swimming. Air transport of gaseous or

16 particulate releases can result in direct inhalation dose from breathing the air or in applicable

17 soil-related pathway exposures from deposition of particulates to the ground surface. The

18 reviewer should ensure the selected exposure pathways are reasonably complete (e.g., they

19 represent the primary means by which humans can be exposed to radionuclides released to air,

20 groundwater, and surface water) and are consistent with regional practices in the vicinity of the

21 disposal site.

22

23 Justification should be provided for excluding applicable exposure pathways or implementing

24 unique or novel approaches to modeling.

25

26 4.3.5.1.2 Site-Specific Input Parameters

27

28 The reviewer should evaluate site-specific and generic information provided for the biosphere

29 characteristics and dose assessment. When deciding whether site-specific or generic

30 information for biosphere model input parameters should be used, the reviewer would generally

31 consider the characteristics of the scenario and potential receptor groups, the modeled system,

32 what the parameters represent, and how the parameters are used in the code. Based on those

33 considerations, an input parameter value is developed that is appropriate for both the system

34 being modeled and for the conceptual and numerical models implemented by the code.

35

36 Because there is uncertainty associated with the behavior of a hypothetical receptor, it is

37 necessary to rely on generically defined receptors for behavioral and metabolic input

38 parameters. Behavioral and metabolic characteristics of receptors must be representative of

39 average members of the receptor group assumed in the modeled exposure scenario. Some

40 performance assessment codes may use default model values for the behavioral and metabolic

41 parameters. The reviewer should ensure that the use of default parameters is consistent with

42 characteristics described for the average member of the receptor group (e.g., if the average

43 member of the critical group is an adult, then it would be inappropriate to use default soil

44 ingestion rates that are appropriate for a child). Commonly, the average member of the critical

45 group is defined as an adult because adults are exposed to more pathways. However, in

46 certain scenarios with limited pathways, children may be the critical group.

47

4-39
1 4.3.5.2 Review Procedures

2

3 The following review procedures focus on evaluating the behavioral and metabolic input

4 parameters used in dose assessments for demonstrating protection of the general population

5 from releases of radioactivity. These review procedures also apply to behavioral and metabolic

6 input parameters used in dose assessments for inadvertent intruder scenarios and scenarios to

7 demonstrate protection of the public during operations. The reviewer should perform the

8 following procedures:

9

10 Examine the coupling of groundwater, surface water, and air transport models to

11 biosphere models. The transport model outputs (e.g., fluxes or concentrations at the

12 biosphere interface) should be linked or have information transferred to the applicable

13 pathways in the biosphere dose assessment model(s).

14

15 Verify that conceptual models for the biosphere include consistent and defensible

16 assumptions based on regional practices and characteristics (i.e., conditions known to

17 exist or expected to exist at the site or surrounding region).

18

19 Confirm that dose assessmentresults are provided for each exposure pathway

20 (e.g., drinking water, crops, meat, milk, fish, inhalation, external) to assess the

21 reasonableness of pathway contributions to the total dose.

22

23 * Verify input parameters and technical bases for the parameters (e.g., transfer factors,

24 consumption rates) for any pathways that are key contributors to dose or have an

25 unexpectedly high or low contribution to the calculated dose.

26

27 Verify the receptor evaluated in the dose assessment has been defined as the average

28 member of the critical group, or a more limiting definition is provided. If the average

29 member of the critical group is selected to be an adult, confirm that the adult is the

30 limiting receptor definition.

31

32 Verify that the internal and external dosimetry approach is consistent with NRC-accepted

33 dosimetry methods (e.g., ICRP 26, ICRP 72) (see Section 4.6.1.3).

34

35 Ensure that selection of the appropriate lung clearance class for inhalation dose

36 coefficients and the fractional uptake to blood for ingestion dose coefficients has an

37 adequate technical basis (e.g., based on the chemical form of the material inhaled or

38 ingested material) or that the highest (most conservative) values of available coefficients

39 are used.

40

41 4.4 Computational Models and Computer Codes

42

43 4.4.1 Areas of Review

44

45 This section focuses on ensuring that codes used to develop a performance assessment model

46 are appropriately chosen, have undergone quality assurance testing (see Section 8), and that

47 model scenarios and conceptual models reviewed as described in Section 4.1 of this guidance

48 document have been appropriately incorporated into the computational model. The reviewer

4-40
1 will benefit from familiarity with NUREG-1 757 (NRC, 2003, Vol. 2, Appendix 1), which,

2 provides guidance for selecting computer codes and incorporating conceptual models into

3 computational models.

4

5 The reviewer should evaluate information provided to ensure that acceptable quality assurance

6 code testing has been conducted (see Section 8). The reviewer. is expected to conduct a more

7 detailed and thorough review of less common codes and codes that may have been developed

8 for site-specific application. For example, to complete a review of a well-established

9 commercial product, it may only be necessary to review input files (e.g., for errors such as unit

10 conversion problems) and output files and to ensure the model has been applied over a range

11 of conditions for which the software has been validated. On the other hand, a code developed 12 by DOE or its contractors for a site-specific evaluation may require a more thorough

13 examination of the quality assurance documentation to ensure an appropriate and accurate

14 implementation of the conceptual model.

15

16 The process of developing a performance assessment model typically has many steps. A

17 number of these steps are reflected in associated review procedures in this section instead of in

18 Section 8, because the analysis steps for the performance assessment may not be explicitly

19 represented in quality assurance procedures (e.g., for data or-software) but can be important to

20 performance assessment analysis.

21

22 4.4.1.1 Modeling Approach: Probabilistic or Deterministic

23

24 DOE may select either a deterministic approach or a probabilistic approach for the analysis to

25 demonstrate compliance, with the performance objectives in 10 CFR Part 61, Subpart C. A

26 deterministic analysis uses single parameter values for every variable in the code. By contrast,

27 a probabilistic approach assigns parameter ranges to certain variables, and the code samples

28 and selects the values for each variable from the parameter probability distribution each time

29 the dose is calculated. While a deterministic analysis calculates the results from a single

30 solution of the equations each time the user runs the code, a probabilistic analysis calculates

31 hundreds of solutions to the equations using different values for the parameters from the

32 parameter ranges. The deterministic model, without additional sensitivity analyses, gives no

33 indication of the sensitivity of the results to certain parameters or of the importance of the

34 uncertainty in the parameters. Therefore, applying a deterministic approach may result in the

35 need for stronger justification of code input parameter values and may require further analysis of

36 doses using upper or lower bounding conditions to gain insights on the range of dose estimates.

37

38 A preferred method for complex assessments is to use a risk-informed approach to performance

39 assessment. This method uses probabilistic sampling for model parameters with irreducible

40 uncertainty that cannot otherwise be shown to be unimportant to system performance. In this

41 type of model, parameters that are well constrained or that can logically be shown to be of little

42 significance are assigned deterministic values, while the remaining parameters are assigned

43 probability distributions that cover the expected ranges of the parameters. Probabilistic

44 approaches to performance assessment are preferred in some situations because they readily

45 permit propagating and assessing the impact of uncertainty on the model results.

46

47 Although probabilistic approaches are preferred for complex assessments, it is acceptable to

48 use a deterministic model to demonstrate compliance with performance objectives.

49 Performance assessments may be used for many different types of problems, ranging from

50 simple to complex. A simple approach is preferable for a simple problem. This guidance

4-41
1 document provides a review framework for different approaches to performance assessment.

2 The choice of the assessment approach is also related to the model support. When the-model

3 support is extensive, the uncertainty can be constrained, thereby reducing the importance of a

4 comprehensive uncertainty analysis.

5

6 In general, if deterministic modeling is used, it should be reasonably conservative and

7 sufficiently documented so that a subject matter expert, with minimal interaction with those who

8 performed the modeling, could conclude that the analysis was conservative. Additional

9 sensitivity analyses to identify significant parameters, model components, and processes may

10 be needed if deterministic analyses are performed. Deterministic sensitivity analyses can be a

11 challenge to plan, execute, and evaluate. Nonlinearity in the model (dose) response to

12 independent parameter values can make selection of appropriate parameter sets for sensitivity

13 cases difficult. In addition, local minima or maxima in the response can occur and the

14 parameter space can be large. Review procedures are provided in Section 4.5.2 to facilitate the

15 review of deterministic sensitivity analyses.

16

17 4.4.1.2 Model Development

18

19 Sections 4.1-4.3 of this document contain guidance to ensure that the models used in the DOE

20 performance assessment (e.g., source term, water infiltration, engineered barrier performance,

21 radionuclide transport, receptor dose) are properly integrated with the overall system model.

22 The reviewer should ensure that the performance assessment models are developed with

23 proper integration of models for each of the exposure scenarios (e.g., onsite, offsite, and

24 inadvertent intruder scenarios). If a probabilistic model is used, the reviewer should ensure that

25 the number of model realizations used to estimate expected dose to a receptor is sufficient to

26 achieve a stable mean dose estimate (i.e., results do not change significantly if more model

27 realizations are simulated). Additionally, the reviewer should ensure that the numerical

28 accuracy of model calculations has been verified as part of the code development process.

29

30 4.4.2 Review Procedures

31

32 The reviewer should determine the adequacy and completeness of the quality assurance

33 documentation of the code/model (see Section 8). This review should include

34 documentation pertaining to (1) software requirements and intended use, (2) software

35 design and development, (3) software design verification, (4) software installation

36 and testing, (5) configuration control, (6) software problems and resolution, and

37 (7) software validation.

38

39 The reviewer should ensure that the computational model, is compatible with the disposal

40 site conceptual model, including the pathways and the exposure scenario. The

41 source-term assumptions of the selected code should also be compatible with the

42 site-specific source term. For example, if the code selected for source-term analysis

43 in the performance assessment does not estimate diffusive releases, the reviewer

44 should ensure that diffusive releases are not important to the performance of the

45 disposal facility.

46

47 - The reviewer should evaluate information on the limitations of the selected codes to

48 ensure that modeling results and modeling approaches are not being arbitrarily

49 constrained by the limitations of the codes selected for the analysis. For example, the

50 selected code may not be able to model the effects of preferential pathways, model

4-42
1 certain exposure pathways, or represent changes in model parameters as a function of

2 time (e.g., for barrier degradation).

3

4 * The reviewer should evaluate the code documentation to verify that the exposure

5 scenarios of the performance assessment code are compatible with the intended

6 scenarios for the site.

7

8 * The reviewer should verify that unit conversion errors have not occurred as a result of

9 the passage of information between models in the analysis.

10

11 * The reviewer should ensure that contaminant fluxes have not been arbitrarily dispersed

12 (e.g., numerically) or diluted artificially in the performance assessment modeling

13 (e.g., artificial dilution of fluxes into larger than expected depths of the s 'aturated zone

14 because of the size of finite elements in the groundwater model). A minor amount of

15 numerical dispersion may be expected.

16

17 * If a probabilistic analysis is performed, the reviewer should ensure that an adequate

18 number of stochastic realizations have been executed to produce stable output.

19

20 * If a deterministic analysis is performed, the reviewer should determine whether the

21 overall performance assessment is sufficiently conservative to account for uncertainty in

22 the parameters and models. For example, the reviewer can make a qualitative,

23 semniquantitative, or quantitative comparison of a list of conservative assumptions or

24 approaches in the analysis with a list of key parameters that were represented as

25 deterministic in the analysis but would be expected to be uncertain.

26

27 - The reviewer should ensure that the performance assessment model results are not

28 sensitive to time stepping or spatial discretization of the model domain.

29

30 - The reviewer should ensure the performance assessment codes properly account for

31 radionuclide decay and ingrowth. The codes should provide a mechanism to track the

32 amounts of radioactivity throughout the disposal system and site over the performance

33 period, including which environmental media the radionuclides are present in or

34 associated with.

35

36 * The reviewer should ensure that the treatment of the transport properties assumed for

37 daughter radionuclides created during a transport leg do not underestimate dose. For

38 example, many dose modeling codes do not assign new properties to daughter

39 radionuclides that are created during transport and can overestimate transport times for

40 daughters that are more mobile than the parent (e.g., Np-237 ingrowth from Am-241).

41

42 4.5 Uncertainty/Sensitivity Analysis for Overall

43 Performance Assessment

44

45 4.5.1 Areas of Review

46

47 General approaches to handling data and model uncertainty are described in Section 4.4.1j..

48 As discussed previously, probabilistic approaches to performance assessment are preferred in

49 most cases because they readily permit the propagation and assessment of the impact of

4-43
1 uncertainty on the model results. However, use of a deterministic model to demonstrate

2 compliance with performance objectives is acceptable. In general, if deterministic modeling is

3 used, it should be reasonably conservative such that a subject matter expert, with minimal

4 interaction with those who performed the assessment, could conclude that the analysis

5 was conservative.

6

7 For modeled processes and input parameters that are highly uncertain and cannot clearly be

8 established as conservative, sensitivity analyses are necessary to establish the relative

9 importance of these processes and parameters to the performance assessment dose

10 calculations. A summary of different methods for sensitivity and uncertainty analyses can be

11 found in NUREG-1757 (NRC, 2003, Vol. 2, Appendix I, Section 1.7) and in NUREG-1573 (NRC,

12 2000, Section 3.3.2).

13

14 As discussed previously, different approaches to performance assessment calculations

15 (e.g., deterministic, probabilistic) have their advantages and disadvantages with regard to

16 uncertainty and sensitivity analysis. While deterministic analysis can be a suitable approach for

17 performance assessment, it can also present a challenge for a dynamic system that responds

18 nonlinearly to the independent variables. When there are numerous inputs (e.g., data or

19 models) that are uncertain, evaluating the impacts of the uncertainties on the decision can be

20 difficult. Typical one-off type of sensitivity analysis where a single parameter is increased or

21 decreased will only identify local sensitivity within the parameter space such that it may not

22 clearly identify the risk implications. A deterministic approach can be useful to bound

23 uncertainty when the analysis can be demonstrated to be conservative. A probabilistic

24 approach can have distinct advantages when there are a number of uncertainties that may

25 significantly influence the results of a performance assessment. For example, the uncertainty

26 introduced by the changing effectiveness of a chemical barrier over time may be represented by

27 selecting appropriate ranges in the transport parameters for the barrier. If a probabilistic

28 approach is used for the performance assessment, the reviewer will need to determine whether

29 there is significant "risk dilution" affecting the calculation results. Risk dilution results when

30 overly broad parameter distributions are selected, primarily for processes that affect the timing

31 of impacts that are expected to occur in the performance period. For example, selection of an

32 overly broad range for the distribution coefficient for Tc-99 in the saturated zone may result in

33 the estimated time of arrival of the contaminant at a receptor location being artificially extended

34 over the period of performance, thereby "diluting" the risk at any one point in time.

35

36 If DOE has performed a deterministic performance assessment, then the reviewer should

37 examine the sensitivity analyses DOE provided. Review the basis for selecting the parameters

38 and combinations of parameters used in the sensitivity analysis. The ranges in the parameters

39 selected should be consistent with the variability and uncertainty in the parameters, and the

40 selected ranges should provide the reviewer confidence that the effects of the uncertainty on'

41 performance are bounded. The reviewer should examine the technical basis used to support

42 the variability and uncertainty. Appropriate combinations of parameters should be used to

43 capture the interdependence of key parameters. The reviewer should consider combinations of

44 parameter values that are likely to occur as a result of common causes.

45

46 Key parameters for further evaluation in sensitivity analysis may be defined with a variety of

47 different approaches, and the appropriateness of the approaches is problem dependent. It is

48 anticipated that the sensitivity analysis and the performance assessment overall may be an

49 iterative process. The initial approach evaluated may not be the final approach selected.

50 Regardless of the process, the reviewer should keep in mind that the purpose of the sensitivity

4-44
1 analysis is to evaluate uncertainty and variability in the assessment.' One of the simplest

2 methods utilizes a top down approach where risk reduction of each component (e.g., infiltration,

3 unsaturated zone, wasteform, engineered barriers, saturated zone, biosphere characteristics) of

4 the performance assessment model is identified by starting with a hazard and calculating how

5 each component reduces the risk from the hazard. Subsequently, within the most important

6 components, a quantitative or qualitative evaluation of the parameters is performed to identify

7 those that are most likely to influence the output from the component. Complications arise

8 because an individual component's importance in the system can be relative to the performance

9 of other components. Sections 4.6.1.1 and 4.6.1.2 provide more detail on the process of

10 evaluating models. Developing an understanding of the importance of parameters and models

11 in a performance assessment is a time-consuming process that is best accomplished by

12 exploring a variety of approaches.

13

14 Because conceptual models are sometimes developed based on limited data, in some cases

15 more than one possible interpretation of the site can be justified based on the existing data.

16 This uncertainty should be addressed by developing multiple alternative conceptual models and

17 implementing the conceptual model that most conservatively estimates the dose or best

18 represents the available data. Alternatively, DOE could provide analyses for multiple

19 conceptual models to develop a range of dose estimates. Consideration of unrealistic and

20 highly speculative conceptual models should be avoided. Consistent with the overall dose

21 modeling framework of starting with simple analyses and progressing to more complex

22 modeling, as warranted, the analyst may want to begin with a simple, conservative analysis that

23 incorporates the key site features and processes and progress to more complexity only as site

24 data merit. A simple representation of the site, in itself, does not mean that the analysis is

25 conservative. The reviewer should evaluate whether DOE has presented information

26 demonstrating that its simplification is justified, based on what is known about the site and the

27 likelihood that alternative representations of the site would not lead to higher calculated doses.

28

29 4.5.2 Review Procedures

30

31 For deterministic analysis, evaluate the adequacy of the process for determining key

32 model parameters.

33

34 If a deterministic model framework is adopted, ensure that key model parameters are

35 either conservative, well justified, or that sensitivity analyses have been provided to

36. demonstrate the overall risk significance of the parameters.

37

38 If conservatism is used as a basis to select deterministic parameter values for the

39 sensitivity analysis, evaluate whether conservatism has been defined locally or globally.

40 For example, stating that the selected saturation value is conservative because it has

41 been set to 1.0 (the highest value expected) and that a saturation of 1.0 maximizes

42 contaminant transport because it maximizes relative permeability is a local argument if a

43 cementitious wasteform is involved. Carbonation of cements is maximized at

44 intermediate values of saturation (due to transport of carbon dioxide in the gas and

45 liquid phases). Carbonation of a cementitious wasteform may eventually disrupt

46 the engineered barrier, resulting in higher release rates compared to assumed

47 saturated conditions.

48

49 If the performance assessment is complex, verify that the technical basis for the

50 conservatism of the sensitivity analysis is supported in at least a semiquantitative

4-45
1 fashion, such as a diagram showing the parameters being evaluated and which

2 submodels of the performance assessment that the parameters affect and in what way.

3 A complex performance assessment would have characteristics such as but not limited

4 to (1) integrated submodels that respond nonlinearly to changes in parameters, (2) many

5 uncertain parameters, (3) high temporal and spatial variability of processes and

6 properties, and (4) many integrated submodels.

7

8 Evaluate the ranges of parameters used in sensitivity analysis, and verify that they

9 reasonably cover the expected ranges.

10

11 Ensure that appropriate combinations of parameters have been used in sensitivity

12 analysis to capture the interdependence of key parameters. For example, consider

13 (1) combinations of parameters affecting radionuclide release that may be physically

14 coupled, such as increased infiltration that may result in more rapid engineered barrier

15 and wasteform deterioration and increased release rates from the wasteform;

16 (2) combinations of parameters used to represent processes that would be expected to

17 occur together, such as cracking of a wasteform due to seismic activity that may affect

18 both physical and chemical durability of the wasteform; and (3) combinations of

19 parameters affecting transport such as decreased Kd values for chemically similar

20 radionuclides due to an external factor (e.g.; leaching of alkalinity from a

21 disposal facility).

22

23 If a deterministic analysis with a sensitivity analysis has been performed and if resources

24 allow, perform an independent probabilistic assessment to evaluate the DOE analysis.

25

26 If DOE has adopted a probabilistic framework, evaluate whether it is sufficient to support

27 understanding of the overall risk significance of uncertain model input parameters.

28

29 If DOE has adopted probabilistic analyses, the reviewer should ensure that unrealistic

30 ranges in parameter distributions that could result in "risk dilution" are not used. This is

31 especially important when the parameter distribution is assigned based on generic or

32 literature information and when the parameter influences the timing of the occurrence of

33 the peak dose (e.g., Kd distributions).

34

35 As appropriate, ensure that DOE has considered alternative conceptual models and

36 that demonstrations of compliance with performance objectives are based on

37 well-supported conceptual models or the most conservative model that is consistent with

38 site characteristics.

39

40 4.6 Evaluation of Model Results

41

42 4.6.1 Areas of Review

43

44 4.6.1.1 Defining Barrier Contributions

45

46 The prior sections of this guidance document address the review of detailed descriptions of

47 engineered and natural barriers and their implementation in the performance assessment

48 model. The reviewer should ensure that the DOE discussion of performance assessment

49 results includes a quantitative and qualitative analysis and description of how engineered and

4-46
1 natural barriers in the performance assessment model limit or prevent doses. The reviewers

2 should use information defining barrier contributions to risk-inform their review.

3

4 The term "barrier" as used in this context, applies to engineered or natural components of the

5 system that may reduce or mitigate risks. Engineered components may be those components

6 specifically designed for the waste disposal facility (e.g., an infiltration cap), or in the case of

7 closure of a waste storage facility, those components of the waste storage facility not

8 specifically designed for long-term performance but that may affect the long-term performance

9 of the system (e.g., a vault holding an underground tank). Results may be provided for intact

10 versus failed (or realistically degraded) barrier performance for individual barriers (and

11 collections of barriers) to gain insights into the importance of barriers on the performance

12 assessment results. In addition, results may be presented with only the natural system or only

13 the engineered system present in the analysis to show the relative contribution of the

14 engineered and natural systems to overall performance of the waste disposal facility. Without

15 an analysis of barrier contributions, the influences of barriers on performance assessment

16 results may not be transparently described or self-evident. In this regard, staff should verify that

17 DOE adequately describes the contributions of key engineered and natural barriers to the

18 performance assessment results. The reviewer should ensure that information about the barrier

19 functions, including the magnitude of the impact of the barrier function on estimated doses, is

20 reasonable and consistent with the descriptions of the engineered barriers (see Section 4.3.2)

21 and characteristics of the disposal site.

22

23 4.6.1.2 Evaluating Intermediate Model Results

24

25 The main purpose of the performance assessment model is to estimate potential long-term

26 radiological dose to receptors. Typically, a large amount of intermediate outputs (such as

27 infiltration through a cap or the fractional release rate from a wasteform) is produced during

28 execution of a performance assessment model. In addition to evaluating the contribution of

29 engineered barriers to reduce or mitigate radiological dose, the reviewer should evaluate

30 intermediate outputs of performance assessment models to understand the interactions of

31 barriers and any possible masking effects of barriers. For example, the infiltration rate through

32 an engineered cap may not be risk significant if the hydraulic properties of the wasteform limit

33 flow to lower values. However, in this case, the engineered cap may be providing a redundant

34 performance function, and it may also be contributing to mitigating degradation mechanisms of

35 the wasteform associated with water flow (e.g., leaching). As appropriate, the reviewer should

36 examine the intermediate results of the performance assessment calculations to understand the

37 integration of the performance assessment models.

38

39 4.6.1.3 Final Dose Calculations

40

41 Numerous NRC guidance documents recommend approaches and specific dose conversion

42 factors used in performance assessments. These include NUREG-1573 (NRC, 2000), which

43 provides guidance on the use of pathway dose conversion factors for calculating doses via

44 potential exposure pathways, and NUREG-1757 (NRC, 2003, Vol. 2, Appendix I), which

45 provides guidance on the use of dose conversion factors such as those developed by the

46 U.S. Environmental Protection Agency (EPA) and published in Federal Guidance Reports 11

47 and 12 (EPA, 1988,1993).

48

4-47
1 The reviewer should assess the dose conversion factors for inhalation and ingestion to

2 ensure that the factors used are those developed by EPA, published in Federal Guidance

3 Report No. 11 (EPA, 1988). Similarly, the reviewer should ensure that the EPA external dose

4 factors published in Federal Guidance Report No. 12 (EPA, 1993) were used. These dose

5 factors were selected to ensure consistency of the dosimetry models used in deriving these

6 factors with NRC regulations in 10 CFR Part 20. The reviewers should evaluate the dose

7 conversion factors used to analyze external doses to ensure the factors are appropriate for the

8 thickness, shielding, and extent of contamination.

9

10 This guidance document advocates the use of dosimetry consistent with 10 CFR Part 20. This

11 ensures that compliance calculations between 10 CFR 61.41 and 10 CFR 61.43 remain

12 consistent, as discussed in NUREG-1573. The proposed rule for 10 CFR Part 63, "Disposal of

13 High-Level Radioactive Wastes in a Proposed Geological Repository at Yucca Mountain,

14 Nevada; Proposed Rule," states

15

16 "As a matter of policy, NRC considers 0.25 mSv [25 mrem] TEDE as the

17 appropriate dose limit within the range of potential doses represented by the

18 current 10 CFR 72.104 limit of 0.25 mSv [25 mrem] (whole body), 0.75 mSv

19 [75 mrem] (thyroid dose), and 0.25 mSv [25 mrem] (to any other critical organ)

20 (NRC 1999)."

21

22 As 10 CFR 61.41 has the same standard as 10 CFR 72.104, this policy is applicable, and

23 therefore, incidental waste determinations may use total effective dose equivalent (TEDE)

24 without specific consideration of individual organ doses. Intruder calculations should be based

25 on 5 mSv [500 mrem] TEDE limit, without specific consideration of individual organ doses, to

26 ensure consistency between 10 CFR 61.41 and 10 CFR 61.43. Because of the tissue weighting

27 factors and the magnitude of the TEDE limit, specific organ dose limits are not necessary for

28 protection from deterministic effects.

29

30 DOE may use the latest dose conversion factors (e.g., ICRP-72). While not completely

31 identical in detail, NRC would generally consider 0.25 mSv [25 mrem] effective dose to be the

32 same as 0.25 mSv [25 mrem] TEDE for these problems. However, the use of dose conversion

33 factors for individual radionuclides or by pathways (i.e., DOE should use the alternate dosimetry

34 for all parts of the analysis [10 CFR 61.41, 61.43, and intruder analyses] and for all

35 radionuclides). The exception to this statement is for direct exposure pathways, which were not

36 updated in ICRP-72. Therefore, older dose conversion factors for direct exposure pathways

37 may be combined with newer dose conversion factors for inhalation and ingestion pathways.

38 Scenarios and critical group assumptions should account for age-based considerations.

39

40 4.6.1.4 Comparison to Performance Objectives

41

42 The postclosure performance assessment is used to demonstrate compliance with

43 10 CFR 61.41, "Protection of the general population from releases of radioactivity,"

44 which states

45

46 "Concentrations of radioactive material which may be released to the general

47 environment in groundwater, surface water, air, soil, plants, or animals must not

48 result in an annual dose exceeding an equivalent of 25 millirems to the whole

49 body, 75 millirems to the thyroid, and 25 millirems to any other organ of any

50 member of the public. Reasonable effort should be made to maintain releases

4-48
1 of radioactivity in effluents to the general environment as low as is

2 reasonably achievable."

3

4 The 0.25 mSv/yr [25 mrem/yr] limit applies for the postclosure period of a disposal facility. NRC

5 expects DOE to express this limit in TEDE (NRC, 2005, 1999, Footnote 1). For probabilistic

6 performance assessment models, it is acceptable to use the peak of the mean dose history to

7 demonstrate compliance with this performance objective.

8

9 The reviewer should evaluate that the appropriate dose limits are applied. To evaluate whether

10 the performance objectives in 10 CFR 61.41 can be met, probability can be considered in the

11 consequence analysis, and the annual dose limit to the member of the general public is

12 0.25 mSv [25 mrem] (NRC, 2005, 1999, Footnote 1). For example, disposal facility

13 performance may be severely affected by a low-frequency, large-magnitude seismic event. In

14 this case, it would be appropriate to factor in the event probability when estimating the risk to

15 the public. In estimating dose to an inadvertent intruder (see Section 5), however, the

16 probability of the intrusion in the stylized analysis is assumed to be 1, and a higher annual dose

17 limit of 5 mSv [500 mrem] is assumed for an inadvertent intruder (NRC, 1981).

18

19 The limit provided in 10 CFR 61.41 {0.25 mSv/yr [25 mrem/yr]} applies to the cumulative

20 impacts from the LLW disposal units that could contribute to the receptor dose (e.g., tanks in a

21 tank farm subject to past, present, and future waste determinations). Because the amount of

22 waste associated with future determinations will not be known in the present, the reviewer will

23 need to consider estimated doses in previous waste determinations for different sources

24 (i.e., those not part of the current waste determination) that could contribute to receptor doses.

25 Eventually, demonstration of compliance with 10 CFR 61.41 will be based on the maximum

26 dose to a receptor from all disposal units subject to waste determinations. All disposal units

27 may not contribute to receptor doses at a particular location (e.g., groundwater flow paths may

28 be in different directions due to the presence of a groundwater divide). The reviewer should

29 note in the TER the cumulative impact from past and current waste determinations.

30

31 Demonstration of stability of the disposal site after closure requires a separate technical

32 evaluation, and review procedures for this performance objective are described in Section 7 of

33 this guidance document. Reviewers of the postclosure performance assessment models should

34 evaluate whether the site stability performance objective is met because long-term site stability

35 is typically an important assumption in the performance assessment conceptual model.

36

37 4.6.2 Review Procedures

38

39 The following review procedures focus on ensuring that performance assessment model results

40 are sufficient for comparison to performance objectives. The reviewer should perform the

41 following review procedures:

42

43 - Examine the descriptions of the methodology used for conversion of internal and

44 external exposure to dose.

45

46 - Ensure the dose conversion factors or correction factors DOE used in the analysis of

47 external doses are appropriate forthe thickness, shielding, and extent of contamination.

48

49 - Ensure that the dose conversion factors selected are consistent with the dosimetry

50 model (e.g., FGR 11 and 12 values are used with ICRP 26 and 30).

4-49
1 • If ICRP-72 values are used, ensure the alternate dosimetry is used for all parts of the

2 analysis (10 CFR 61.41, 61.43 and intruder analyses) and for all radionuclides. An

3 exception would be to use FGR 12 values for direct exposure pathways while using

4 ICRP-72 values for inhalation and ingestion, because the direct exposure values were

5 not updated in ICRP-72.

6

7 Ensure that solubility classes were conservatively selected or technical basis has been

8 provided for selecting less conservative values.

9

10 Review the DOE description of the comparison of performance assessment model

11 output to the applicable performance objectives in 10 CFR Part 61, Subpart C. Ensure

12 that the description includes an appropriate performance measure such as peak of the

13 mean dose for probabilistic assessments or peak dose for deterministic assessments.

14

15 Ensure that descriptions of performance assessment results are sufficient to permit

16 comparison of model results to the performance objective of 10 CFR 61.41.

17

18 Ensure that DOE is using the appropriate dose limit from 10 CFR 61.41 for the public

19 during the period after active institutional controls.

20

21 Ensure that probabilities have been appropriately applied to the determination of

22 whether the performance objective in 10 CFR 61.41 can be met, if necessary.

23

24 Evaluate compliance with 10 CFR 61.41 by ensuring that the maximum cumulative dose

25 to a public receptor from disposal units evaluated in past waste determinations and the

26 present waste determination does not exceed 0.25 mSv/yr [25 mrem/yr]. The reviewer

27 should assess whether the location of the receptor that is expected to receive the

28 maximum cumulative dose was appropriately determined or bound (e.g., impacts from

29 each disposal unit were assumed to be along the same groundwater flow path).

30

31 Evaluate the sensitivity/uncertainty analyses provided with the performance assessment

32 to determine whether the analyses are sufficient to permit evaluation of model sensitivity

33 to uncertain processes and input parameters.

34

35 Verify that modeled processes and input parameters are treated in a manner that is

36 either demonstrably conservative, sufficiently constrained by site data, or otherwise

37 demonstrated to contribute to an insignificant uncertainty effect on modeled

38 dose estimates.

39

40 Ensure that DOE has addressed uncertainty in the timing of the peak dose if a

41 deterministic analysis is used. The reviewer should evaluate whether significant peak

42 doses occur after the period of performance and whether uncertainties in any of the

43 transport or release models or parameters would be sufficient to move the peak doses

44 into the performance period.

45

46 Ensure that DOE has provided an adequate technical basis to explain differences

47 between current and past modeling of the disposal facility, as appropriate.

48

4-50
1 * Verify that DOE has provided a complete description of all the key barriers included in

2 the performance assessment model. This review should be integrated with the detailed

3 technical reviews conducted in Sections 2-8.

4

5 • Verify that the DOE description and analysis of performance assessment results

6 provides a complete (qualitative and quantitative) analysis and description of barrier

7 contributions to performance assessment results. The discussion of results should

8 include a transparent description of how the modeled disposal site system is functioning,

9 with an emphasis on barriers to release and transport that affect the magnitude or timing

10 of estimated doses. A brief example of the type of information that may be included in

11 such a barrier performance analysis description is provided in the following paragraph:

12

13 The engineered cap reduces infiltration to the waste from 25 cm/yr [10 in/yr] to 1 cm/yr

14 [0.4 in/yr] for 1,000 years. Without the engineered cap present, the dose only increased

15 a factor of 2 from the nominal case because of the low hydraulic properties of the

16 wasteform. In the case of the cap failing and the wasteform degrading hydraulically, the

17 dose is increased by a factor of 20 from the nominal case. The chemical properties of

18 the wasteform provide a significant barrier to radionuclide release, even if the system

19 does not perform as intended from a hydrologic standpoint. Without the chemical

20 properties of the wasteform, the dose would increase an additional factor of 100,

21 primarily as a result of the release of relatively strongly sorbing Np-237 and Pu-239.

22

23 Following review of the DOE description of performance assessment results, ensure an

24 adequate technical basis is provided for barrier capabilities that contribute significantly to

25 performance assessment results (i.e., those barriers that significantly reduce estimated

26 doses or significantly delay the estimated doses). The characteristics of the barriers

27 should be described in detail to provide confidence in the performance capabilities of

28 the barriers.

29

30 Evaluate whether the DOE performance assessment has appropriately accounted for

31 applicable barrier interactions (e.g., change or variation in chemistry that degrades an

32 engineered barrier could also influence sorption or source term release estimates).

33 Analysis of the performance of individual barriers one at a time may be incomplete,

34 because this type of analysis may miss plausible and potentially important interactions of

35 features and processes that can amplify impacts on system performance.

36

37 Evaluate whether the modeling of barriers in the performance assessment appropriately

38 accounts for and propagates applicable uncertainties and variabilities or (in particular for

39 deterministic analyses) that barriers are represented conservatively.

40

41 Verify that the description of each barrier is consistent with the detailed description and

42 supporting information for barrier features and capabilities.

43

44 Evaluate intermediate results from the DOE performance assessment to understand the

45 interactions of barriers and any possible masking effects of barriers. Verify that

46 intermediate results (e.g., fluxes, travel times) are physically reasonable.

47

4-51.
. m • m ......

1 4.7 ALARA Analysis 2

3 This part of the review focuses on assessing compliance with the requirement in 10 CFR 61.41

Sfit releases of radioactivity in effluents from the disposal facility to the general environment be

5 maintained as low as is reasonably achievable (ALARA). The review of the postclosure

6 performihas-s&iýýment to determine compliance with the dose requirements of 10 CFR 61.41

7 is•id98 d in Secbtids 4 1-t'.6. Revi'w of the performance objective for maintaining radiation

8 ekxp"osures to individuals'duiing oiT'tions ALARA, as required in 10 CFR 61.43, is discussed in

9 Section 6 of this guidance document.

10

11 4.7.1 Areas of Review

12

13 In general, the conclusion that proposed waste management activities will result in the removal

14 of highly radioactive radionuclides to the maximum extent practical (see Section 3) supports the

15 conclusion that releases of radioactivity in effluents from the disposal site will be maintained

16 ALARA. Thus, a reviewer should begin the evaluation of compliance with the ALARA

17 requirement of 10 CFR 61.41 by completing the review described in Section 3 of this guidance

18 document. In addition, because steps taken to stabilize waste also are expected to limit

19 radionuclide release from the disposal facility, stabilization activities also are relevant to the

20 assessment of compliance with the requirement to maintain effluents ALARA. Therefore, a

21 reviewer should evaluate DOE's description of actions taken to stabilize the waste to minimize

22 the release of radionuclides from the disposal facility (e.g., efforts to optimize solidification of

23 liquid wastes or efforts to optimize mixing or encapsulation of residual tank waste with grout).

24 The review should be focused on the dominant pathways of radionuclide release from the

25 disposal facility and the factors causing the most uncertainty in release rates, as determined in

26 DOE's performance assessment and independent analyses.

27

28 4.7.2 Review Procedures

29

30 After completing the review described in Section 3 of this guidance document, the reviewer

31 should identify the dominant pathways of radionuclide release from the disposal site based on

32 the results of DOE's performance assessment and any independent analysis used in the review

33 described in Sections 4.1-4.6 of this guidance document. When identifying dominant release

34 pathways, the reviewer should also identify key uncertainties that may affect which factors

35 dominate radionuclide release (e.g., placement of waste in areas thought to be especially prone

36 to the development of preferential pathways for infiltrating water may cause significant

37 uncertainty in releases to groundwater). In general, the reviewer should determine what steps

38 have been taken to limit the release of radionuclides through the dominantý release pathways

39 and to limit the potential for high release rates due to alternate release fTf~an-ism.--

40 Specificafl-'; the reviewer should perform the following activities:

41

42 * Confirm that DOE has provided sufficient support for the performance assessment that

43 the dose requirements of 10 CFR 61.41 can be met (see Sections 4.1-4.6).

44

45 - Determine whether vwaste is placed in-are66sthat are susceptible to the formation of

46 preferenrtial pIathWays for infiltrating water (e.g., along joints between dissirmiAIE

47 materials) and whether appropriate steps have been taken to move waste from those

48 areas, if-practical.

49

4-52
1 Determine whether appropriate efforts have been made to optimize the solidification of

2 -any relevant liquid waste (in general, wastes containing more than 1 percent residual

3 liquid by volume are not suitable for near-surface disposal [10 CFR 61.56]).

4

5 If stabilizing material is added to a waste, determine whether appropriate efforts have

6 been made to optimize mixing or encapsulation of the waste with the stabilizing material

7 (e.g., evaluate the selection of methods used to optimize mixing of residual waste and

8 grout in tanks).

9

10 To the extent possible, the determination of whether efforts to optimize waste stabilization are

11 appropriate should be evaluated based on quantitative measures, using procedures similar to

12 those discussed in Section 3. For example, if releases from wastes located along the edges of

13 a tank contribute significantly to releases of radionuclides into groundwater or contribute

14 significant uncertainty to the expected releases from the site, the reviewer should evaluate

15 DOE's selection of options available to move or stabilize the wastes present along the edge of

16 the tanks. Procedures similar to those used to evaluate DOE's selection of technologies

17 available to remove the waste from the tank, as described in Section 3, should be considered.

18 Similarly, to determine whether actions that could stabilize waste are practical, it may be

19 necessary to compare the costs and benefits of additional stabilization, as described in

20 Section 3.4.

21

22 4.8 References

23

24 Bradbury, M. and F.A. Sarott. "Sorption Databases for the Cementitious Near-Field of a L/ILW

25 Repository for Performance Assessment." PSI Bericht 95-06, Wurenlingen and Villigen,

26 Switzerland: Paul Scherrer Institut. 1995.

27

28 U.S. Environmental Protection Agency (EPA). "Federal Guidance Report No. 11: Limiting

29 Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for

30 Inhalation, Submersion, and Ingestion." EPA-520/1-88-020. September 1988.

31

32 . "Federal Guidance Report No. 12: External Exposure to Radionuclides in Air, Water

33 and Soil." EPA-402-R-93-081. September 1993.

34

35 . "Understanding Variation in Partition Coefficient, Kd, Values." EPA-402-R-99-004A.

36 August 1999.

37

38 U.S. Nuclear Regulatory Commission (NRC). "Draft Environmental Impact Statement on

39 10 CFR Part 61 Licensing Requirements for Land Disposal of Radioactive Waste."

40 NUREG-0782. September 1981.

41

42 . "Final Environmental Impact Statement on 10 CFR Part 61 Licensing Requirements for

43 Land Disposal of Radioactive Waste." NUREG-0945. 1982.

44

45 . "Generic Technical Position on Peer-Review for High-Level Nuclear Waste

46 Repositories." NUREG-1297. February 1988a.

47

48 . "Generic Technical Position on Qualification of Existing Data for High-Level Nuclear

49 WasteRepositories." NUREG-1298. February 1988b.

4-53
1 . "Branch Technical Position on the Use of Expert Elicitation in the High-Level

2 Radioactive Waste Program." NUREG-1563. November 1996.

3

4 . "Disposal of High-Level Radioactive Wastes in a Proposed Geological Repository at

5 Yucca Mountain, Nevada." Proposed Rule. Federal Register, 64 FR 8640. February 1999.

6

7 . "A Performance Assessment Method For Low-level Waste Disposal Facilities:

8 Recommendations of NRC's Performance Assessment Working Group." NUREG-1573.

9 October 2000.

10

11 "Consolidated NMSS Decommissioning Guidance." Vols. 1-3. NUREG-1757.

12 September 2003.

13

14 "Technical Evaluation Report for the U.S. Department of Energy, Savannah River Site

15 Draft Section 3116 Waste Determination for Salt Waste Disposal." Letter from L. Camper to

16 C. Anderson, DOE. December 2005.

17

4-54
1 5 INADVERTENT INTRUSION

2

3 The performance objective for protection of the inadvertent intruder is provided in

4 10 CFR 61.42. Specifically, the staff review should confirm whether the design, operation, and

5 closure of the land disposal facility will ensure protection of an individual inadvertently intruding

6 into the disposal site and occupying the site or contacting the waste at any time after active

7 institutional controls for the disposal site are removed. The performance objective in

8 10 CFR 61.42 does not provide a numerical dose criteria for protection from the inadvertent

9 intruder. In previous waste determination reviews (NRC, 2000a, 2003a, 2005), the U.S. Nuclear

10 Regulatory Commission (NRC) has applied the whole body-dose equivalent limit of 5 mSv/yr

11 [500 mrem/yr] described in Section 4.5 of Volume 2 from the Draft Environmental Impact 12 Statement for 10 CFR Part 61 (NRC, 1981) to assess intruder scenarios. When evaluating

13 protection of the inadvertent intruder, NRC assumed that active institutional controls would be

14 maintained for 100 years following permanent closure [10 CFR 61.59(b)].

15

16 Additional guidance on intruder analysis can be found in NUREG-0782 (NRC, 1981, Vol. 2,

17 Chapter 4), NUREG-1 200 (NRC, 1988), and NUREG/CR-4370 (Oztunali and Roles, 1986).

18 Performance assessment modeling approaches are discussed in Section 4 of this guidance

19 document, and additional guidance for developing performance assessment and dose

20 assessment models can be found in NUREG-1573 (NRC, 2000b) and NUREG-1757 (NRC,

21 2003b). Specific guidance on the period for active institutional controls is provided in

22 Section 4.1.1.1, and the influence of regional practices on scenario identification is discussed in

23 Sections 4.1.1.3 and 4.1.1.4. Protection of individuals during operations is discussed in

24 Section 6, and site stability is discussed in Section 7 of this guidance document.

25

26 5.1 Areas of Review

27

28 In evaluating the intruder protection system proposed by the U.S. Department of Energy (DOE),

29 reviewers should consider the operations, procedures, materials, barriers, and structures

30 designated to provide this protection. Active protection systems may be effective during a

31 100-year period of institutional control, but given the long time periods considered in

32 performance assessment used to predict potential doses following permanent closure of the

33 facility, reviewers may need to consider the performance of engineered and natural systems as

34 passive barriers to intrusion. A passive barrier is a barrier that may perform its intended

35 functions without active monitoring and maintenance. The reviewer should take a risk-informed,

36 performance-based approach to reviewing any site-specific intruder analysis and inadvertent

37 intruder protection systems DOE proposed, and the reviewer should evaluate the parameters

38 used in the intruder analysis in the context of regional practices. This approach provides DOE

39 with flexibility in analyzing intruder scenarios to demonstrate compliance with the performance

40 objectives of 10 CFR 61.42.

41

42 5.1.1 Assessment of Inadvertent Intrusion

43

44 The reviewer should assess DOE-provided information regarding estimates of the potential

45 dose to an inadvertent intruder. Because many intruder scenarios may be simpler and involve

46 less integration of submodels compared to the public dose scenarios evaluated for compliance

47 with 10 CFR 61.41, a more simplified analysis could be performed. Intruder scenarios

48 commonly involve disruption of the waste disposal facility and exhumation of waste, with

49 resultant calculations of dose. The reviewer will need to consider the complexity of the intruder

5-1
1 ' scenarios and determine whether the analysis was sufficiently detailed to account for important

2 features, events, and processes. The review of the nominal case performance assessment is

3 described in Section 4 of this guidance document. The reviewer should consider the guidance

4 found in Section 4, as needed, for review of inadvertent intruder scenarios. In most cases, the

5 reviewer will only need to consider the guidance found in this section for inadvertent intruder

6 analysis. The reviewer should evaluate the following information regarding inadvertent intrusion:

7

8 Technical bases and associated analyses used to define the intruder scenarios. This

9 should include aspects such as the behavior of the intruder, timing of the intrusion, and

10 the exposure pathways simulated in the intruder analysis.

11

12 Assumptions and parameters used in developing the intrusion assessment,

13 characteristics of the intrusion event, how uncertainties are considered in the analysis,

14 and resultant conditional doses for each intruder scenario. The assumptions in the

15 intruder analysis should be consistent with past, current, and projected regional

16 practices and the performance assessment (see Section 4).

17

18 5.1.2 Intruder Protection Systems

19

20 As discussed in Section 4.1.1.1, active institutional controls are limited to 100 years or less after

21 closure, but DOE may propose passive systems to protect from inadvertent intrusion. The

22 reviewer should examine any DOE-proposed intruder protection system. This could include

23 engineered barriers (caps, rock layers) or waste system placement and burial (e.g., depth to

24 waste) to reduce the potential for inadvertent intrusion. As specified in 10 CFR Part 61, intruder

25 barriers should prevent or limit intrusion for 500 years for Class C waste. After 500 years, the

26 activity of Class C waste would decay such that an inadvertent intruder would be protected if

27 they contacted the waste. The service life for an intruder barrier for greater than Class C waste

28 may need to be considerably longer than for Class C waste, and technical justification for

29 long-term performance may be considerably more challenging. As discussed in Section 3.2.2 of

30 NUREG-1573, service lives for engineered barriers, on the order of a few hundred years, are

31 considered credible if justified by adequate technical analyses and data (NRC, 2000b). The

32 reviewer should review how the features of the engineered barriers and projected service

33 lifetimes are incorporated in the intruder analysis. Depth to waste is an important consideration

34 in defining intruder scenarios, because some scenarios may not be credible if the waste is

35 generally inaccessible. The reviewer should review the projected depth to waste for the waste

36 disposal system being evaluated and how the depth may change during the performance period

37 (e.g., because of erosion).

38

39 5.1.3 Types of Scenarios Considered in the Intruder Analysis

40

41 Future human behavior cannot be accurately predicted over hundreds to thousands of years.

42 To address this uncertainty, hypothetical intruder scenarios are designed to bound the exposure

43 to the intruder while avoiding speculation about future human activities. The regulations in

44 10 CFR 61.42 do not specify that a particular scenario be used to demonstrate compliance. In

45 developing intruder scenarios, it is anticipated that DOE will assume humans will continue

46 normal land use activities that are consistent with recent past (e.g., a few decades) and current

47 regional practices after active institutional controls are no longer enforced. DOE is not expected

48 to provide probability estimates for the individual scenarios, but conditional doses should be

49 estimated for each scenario considered in the inadvertent intruder analysis. To the extent that

5-2
1 DOE has provided an analysis of various intruder scenarios, the reviewer should evaluate the

2 site-specific scenarios using the guidance in Section 5.2. This may include one or more of the

3 following scenarios.

4

5 5.1.3.1 Intruder-Resident Scenario

6

7 This scenario assumes that after the end of active institutional controls, an intruder (i.e., the

8 resident intruder) inadvertently constructs a house at and lives on the waste disposal area. The

9 reviewer should assess the location of the resident intruder relative to the waste disposal

10 system, the behavior attributed to the intruder, and the timing of the intrusion. The reviewer

11 should examine dose pathways assumed for this scenario (e.g., direct exposure, ingestion

12 [drinking water, vegetables, soil], inhalation) and the parameters and calculations used to

13 estimate intruder doses. The intruder-resident is typically assumed to have a garden that is

14 used to raise produce (for chronic exposures). The resident intruder may also be exposed to

15 contaminated drill cuttings that resulted from installation of a well for domestic purposes (see

16 Section 5.1.3.4).

17

18 5.1.3.2 Intruder-Agriculture Scenario

19

20 This scenario assumes that after the end of active institutional controls, a farmer lives on and

21 consumes food crops grown and animals raised on the disposal area. The reviewer should

22 assess the location of the intruder relative to the waste disposal system, the behavior attributed

23 to the intruder, and the timing of the intrusion. The reviewer should examine dose pathways

24 assumed for this scenario (e.g., direct exposure, ingestion [drinking water, plant products,

25 animal products, soil], inhalation) and the parameters and calculations used to estimate intruder

26 doses. The intruder-agriculture is typically assumed to have a garden that is used to raise

27 produce (for chronic exposures). The reviewer should examine the extent to which the intruder

28 analysis accounts for ground-disturbing activities by the farmer (e.g., plowing, spreading drill

29 cuttings). Additional description of this scenario is provided in NUREG-0782 (NRC, 1981,

30 Appendix G).

31

32 5.1.3.3 Intruder-Recreational Hunting/Fishing Scenario

33

34 In this scenario, a hunter/fisher is assumed to visit the site, perhaps on a periodic basis, and

35 to consume game and fish taken from the site, but otherwise not reside on the site. Fish

36 and game ingestion pathways may need to be included for the intruder-resident or

37 intruder-agriculture scenarios, but generally they result in limited relative contribution to

38 total dose for these scenarios and can be eliminated from inclusion. The reviewer should

39 assess the behavior attributed to the intruder and the timing of the intrusion. The reviewer

40 should examine dose pathways assumed for this scenario (e.g., direct exposure, inadvertent

41 soil ingestion, inhalation, ingestion of fish and game), the parameters and calculations used to

42 estimate intruder doses, and the time the intruder is at the site.

43

44 5.1.3.4 Intruder-Driller Scenario

45

46 This scenario assumes that after the end of active institutional controls, a well is drilled into the

47 waste disposal system. The well may be for domestic water use, irrigation, or the exploration or

48 recovery of natural resources. If natural resources other than water are identified (see

49 Section 1.1.3.2), additional drilling scenarios may be proposed. In a drilling scenario, an acute

50 intruder is assumed to be the person (or persons) who installs the well and is exposed to drill

5-3
1 cuttings during well installation. The reviewer should assess the behavior attributed to the

2 intruder and the timing of the intrusion. The reviewer should examine dose pathways assumed

3 fr this scenario (e.g., direct exposure, inadvertent ingestion of soil, inhalation), the parameters

' ana calculations used to estimate intruder doses, and the time spent to install the well.

5 Additional description of this scenario is provided in NUREG/CR-4370 (Oztunali and

6 Role,. 1986). Exposure of a resident or farmer to drill cuttings left on the land surface after the

7 instznial on of a well would be considered Lider Section 5.1.3.1 or Section 5.1.3.2, respectively

8 •this ý referred to as a chronr',z scenariojb

9

10 5.1.3.5 Intruder-Ccnsýruction Scenario 11

12 In this scenario, it is assumed that after the end of active institutional controls, a construction

13 project begins at the site with associated earthmoving activities, resulting in disruption of the

14 disposal facility and potential exposure of waste to the environment. The reviewer should

15 assess the behavior attributed to the intruder and the timing of the intrusion. The reviewer

16 should examine dose pathways assumed for this scenario (e.g., direct exposure, inadvertent

17 ingestion of soil, inhalation) and the time spent at the site. Additional description of this

18 scenario is provided in NUREG-0782 (NRC, 1981, Appendix G).

19

20 5.1.3.6 Other Scenarios

21

22 There may be other less common scenarios proposed on a site-specific basis. As with the

23 previous scenarios, the reviewer should assess the behavior attributed to the intruder and the

24 timing of the intrusion. The reviewer should examine dose pathways assumed for the scenario,

25 the time spent at the site, and the parameters and calculations used to estimate intruder doses.

26 The reviewer should assess whether the other intruder scenarios are appropriate and

27 sufficiently conservative.

28

29 5.2 Review Procedures

30

31 The reviewer should evaluate the types of scenarios DOE considered in the intruder analysis

32 and confirm that the scenarios considered are appropriate for the site. Specifically, the reviewer

33 should perform the following activities:

34

35 - Verify that assumptions and parameters used in defining the exposed intruder, including

36 location and behavior of the intruder, timing of the intrusion, and exposure pathways, are

37 consistent with the current regional practices. For example, at a site with shallow water

38 resources and low-strength surface geologic materials, local drilling companies may not

39 typically be equipped to drill through buried, high-strength engineered materials.

40 However, at a site with high-strength geologic materials (e.g., basalt) and deep water

41 resources, drilling companies may be commonly equipped to drill through an

42 underground engineered structure (inadvertently).

43

44 Verify that assumptions and parameters used in defining the exposed intruder are

45 consistent with the assumptions and parameters used in the performance assessment

46 that is reviewed using Section 4 of this guidance document. For example, confirm that

47 the same radionuclide inventories are used for both the performance assessment and

48 the intruder analysis.

49

5-4
I Assess whether, in the selection of intruder scenarios, DOE considered wasteform and

2 barrier degradation (e.g., it may be safe to rule out drilling for the first 1,000 or 2,000

3 years as a result of the presence of intruder barriers or other wasteform characteristics,

4 but drilling may become more plausible as the wasteform or barriers degrade).

5

6 * Verify that the time of intrusion assumed in the analysis produces the maximum dose.

7 For example, an intrusion event at 100 years may produce the maximum dose from

8 short-lived fission products, but the maximum dose from the daughters of long-lived

9 isotopes may occur after 1,000 years.

10

11 * Verify that the wasteform properties and the disposal facility design (including natural

12 and engineered barriers designed to protect inadvertent intruders) considered in the

.13 intruder analysis are consistent with the DOE-conducted performance assessment and

14 are reviewed under Section 4 of this guidance document.

15

16 - Confirm that DOE does not use the probability of an intrusion to reduce the potential

17 consequences estimated in the intruder analysis.

18

19 - Evaluate active institutional controls proposed in the waste determination, and assess

20 the time period for which DOE assumes they are effective.

21

22 * Verify that proposed intruder barriers are appropriately represented in conceptual and

23 numerical models used to simulate long-term performance. In particular, evaluate

24 whether degradation of intruder protection systems is appropriately considered in the

25 intruder analysis and that credit for the passive performance of intruder barriers is limited

26 to 500 years or is otherwise justified.

27

28 - Verify that adequate technical basis is provided for parameters used in the intruder

29 analysis, in particular for site-specific, regionally based values that are less conservative

30 than nationally based generic parameters.

31

32 - Verify that the area over which contaminated material is dispersed is appropriate for the

33 scenario. For example, the area required to distribute contaminated soil and waste from

34 the excavation of a foundation for a residence will b 'e considerably larger than the area

35 required to distribute contaminated drill cuttings.

36

37 * If a garden is assumed in the scenario, verify that the garden size is appropriate and

38 consistent with regional practices. Verify that the garden size is consistent with the

39 assumed yields of produce from the garden.

40

41 * Evaluate whether the DOE assessment of inadvertent intrusion provides reasonable

42 assurance that an inadvertent intruder will be sufficiently protected, based on an

43 understanding of assumptions and parameters of the analysis, characteristics of the

44 intrusion event, and consideration of uncertainties in the analysis. Compare the intruder

45 doses calculated in the intruder analysis to the 5 mSv/yr [500 mrem/yr] standard

46 described in NUREG-0872 (NRC 1981, Vol. 2, Section 4.5). Evaluate the DOE

47 identification and summary of key assumptions and parameters that most strongly

48 influence the dose results for the inadvertent intruder analyses.

49

5-5
1-.. 5.3 References

2

3 Oztunali, 0.1. and G.W. Roles. "Update of Part 61: Impacts Analysis Methodology,

4 Methodology Report." NUREG/CR-4370. NRC. 1986.

5

6 U.S. Nuclear Regulatory Commission (NRC). "Draft Environmental Impact Statementon 10

7 CFR Part 61 Licensing Requirements for Land Disposal of Radioactive Waste." NUREG-0782.

8 September 1981.

9

10 . "Standard Review Plan for the Review of a License Application for a Low-Level

11 Radioactive Waste Disposal Facility." NUREG-1200. NRC. January 1988.

12

13 . "Savannah River Site High-Level Waste Tank Closure: Classification of Residual

14 Waste as Incidental." Letter from W. Kane to R.J. Schepens, DOE. June 2000a.

15

16 . "A Performance Assessment Methodology for Low-Level Radioactive Waste Disposal

17 Facilities: Recommendations of NRC's Performance Assessment Working Group."

18 NUREG-1573. October2000b.

19

20 . "NRC Review of Idaho Nuclear Technology and Engineering Center Draft Waste

21 Incidental to Reprocessing Determination for Tank Farm Facility Residuals-Conclusions and

22 Recommendations." Letter from L. Kokajko to J. Case, DOE. June 2003a.

23

24 . "Consolidated NMSS Decommissioning Guidance." Vols. 1-3. NUREG-1757.

25 September 2003b.

26

27 "Technical Evaluation Report for the U.S. Department of Energy, Savannah River Site

28 Draft Section 3116 Waste Determination for Salt Waste Disposal." Letter from L. Camper to

29 C. Anderson, DOE. December 2005.

30

5-6
1 6 PROTECTION OF INDIVIDUALS DURING OPERATIONS

2

3 The performance objective for protection of individuals during operations is provided in

4 10 CFR 61.43. Specifically, the staff review should confirm whether the design, operation, and

5 closure of the facility will provide reasonable assurance that the radiation protection standards

6 in 10 CFR Part 20 will be met. This includes doses both to workers and members of the

7 public during operations. In addition, 10 CFR 61.43 requires that every reasonable effort will

8 be made to maintain radiation exposures as low as is reasonably achievable (ALARA). The

9 U.S. Department of Energy (DOE) is self-regulating with respect to operational activities and

10 uses the regulations in 10 CFR Part 835, "Occupational Radiation Protection," to set

11 operational dose limits for workers and members of the public and to demonstrate ALARA. The

12 waste criteria discussed in Section 2 of this guidance document do not confer regulatory or

13 statutory authority on the U.S. Nuclear Regulatory Commission (NRC) with regard to DOE

14 operational activities.

15

16 In demonstrating that there is reasonable assurance that the 10 CFR Part 61.43 performance

17 objectives Will be met, DOE can reference the applicable portions of 10 CFR Part 20 and

18 provide the corresponding requirement of 10 CFR Part 835. Given the role of NRC with respect

19 to incidental waste activities, the portions of 10 CFR Part 20 that are relevant in this context are

20 the dose limits for radiation protection of the public and workers during disposal operations and

21 not those requirements regarding general licensing, administrative, programmatic, or

22 enforcement matters intended for NRC licensees. Therefore, the applicable portions of

23 10 CFR Part 20 are

24

25 * 10 CFR 20.1101(d) 10 CFR 20.1206(e)

26 • 10 CFR 20.1201(a)(1)(i) 10 CFR 20.1207

27 ° 10 CFR 20.1201(a)(1)(ii) ° 10 CFR 20.1208(a)

28 ° 10 CFR 20.1201(a)(2)(i) ° 10 CFR 20.1301(a)(1)

29 ° 10 CFR 20.1201(a)(2)(ii) ° 10 CFR 20.1301(a)(2)

30 • 10 CFR 20.1201(e) ° 10 CFR 20.1301(b)

31

32 These dose limits generally correspond to the dose limits in 10 CFR Part 835 and relevant DOE

33 Orders and guidance that establishes DOE regulatory and contractual requirements for DOE

34 facilities and activities. On the basis of this equivalence, the reviewer need only evaluate how

35 the DOE regulations and limits would be implemented at the site. As the Ronald W. Reagan

36 National Defense Authorization Act for Fiscal Year 2005 (NDAA) (see Appendix A) requires,

37 NRC will monitor compliance with 10 CFR 61.43, as discussed in Section 10 of this guidance

38 document, for waste that is subject to the NDAA.

39

40 6.1 Areas of Review

41

42 This part of the staff review focuses on the DOE-identified operational dose limits and the

43 commitments made to meet them. Releases of radioactivity from facility effluents are governed

44 by the requirements of 10 CFR 61.41, as discussed in Section 4 of this guidance document.

45 Other doses are governed by 10 CFR 61.43, which references 10 CFR Part 20. The reviewer

46 should determine what regulations and limits will be used to establish operational dose limits for

47 any proposed facilities and activities and what approaches and radiation protection programs

48 will be used to ensure that doses are maintained ALARA. The reviewer should evaluate

6-1
1 estimated doses to both workers and members of the public during operations. Typically, the

2 estimated dose to the public is calculated at the boundary of the facility where active institutional

3 controls are not in effect (i.e., the fence line of the larger DOE site), but it may include the dose

4 to members of the public who visit the site. As necessary, the reviewer should also examine

5 selected portions of DOE operational documents to learn how DOE implements its worker

6 protection program. For example, DOE may have radiation protection programs, documented

7 safety analyses, or relevant access controls and training.

8

9 6.2 Review Procedures

10

11 It is anticipated that DOE will continue to reference the regulations and limits set forth in

12 10 CFR Part 835 to establish operational dose limits and to demonstrate that doses are

13 maintained ALARA for proposed waste management activities. The implementation of these

14 commitments and compliance with the requirements and limits will be ensured through DOE's

15 own regulations and assessed during NRC monitoring (see Section 10). The review for this

16 section should therefore focus on (1) DOE commitments to adhere to the appropriate

17 regulations and (2) descriptions of how the regulations are implemented with respect to the

18 waste determination. Based on this assumption, the reviewer should perform the

19 following procedures:

20

21 Determine whether DOE has identified either 10 CFR Part 20 or 10 CFR Part 835 as the

22 basis for its radiation protection programs and dose limits. If DOE has identified other

23 limits, ensure that these regulations and limits provide protection from radiation exposure

24 that is comparable to the NRC requirements in 10 CFR Part 20 or 10 CFR Part 835.

25

26 Evaluate the appropriateness and adequacy of DOE estimates of doses that may be

27 received by both workers and members of the public during operations due to the waste

28 being evaluated, and determine whether the doses are less than those in

29 10 CFR Part 20 or 10 CFR Part 835 (e.g., 50 mSv/yr [5 rem/yr] for workers, 1 mSv/yr

30 [100 mrem/yr] to a member of the public from sources other than effluents}. Review the

31 approaches and methods that assure the estimated doses will not be exceeded. The

32 doses may be estimated by assessing the doses received from comparable activities at

33 the site.

34

35 - Determine whether DOE has appropriate procedures and processes for ensuring that

36 doses remain below applicable limits (e.g., a radiation protection program or safety

37 analyses reports). Because DOE is a self-regulating Federal agency with a history of

38 estimating and managing doses, the reviewer should apply the appropriate level of detail

39 in reviewing this area (e.g., reviewing the assumptions made in accident analyses is

40 typically not necessary).

41

42 Verify that DOE will follow an ALARA philosophy. Confirm that management

43 commitments, facility designs, and operations programs designed to control radiation

44 exposure will be implemented to maintain doses ALARA. As necessary, examine

45 selected portions of DOE operational documents to learn how DOE implements its

46 worker protection program.

47

48 Review any additional measures that DOE uses to ensure that radiation exposures will

49 be ALARA.

6-2
1 7 SITE STABILITY, WASTE STABILITY, AND FACILITY STABILITY

2

3 7.1 Areas of Review

4

5 This section focuses on reviewing factors that could affect the stability of the proposed disposal

6 site, including the potential effects of erosion, flooding, seismicity, and other disruptive

7 processes. This section also addresses stability of the waste and engineered features of a

8 disposal facility. The performance objectives for disposal site stability after closure are provided

9 in 10 CFR 61.44, which states that the disposal facility must be sited, designed, used, operated,

10 and closed to achieve long-term stability of the disposal site and to eliminate, to the extent

11 practicable, the need for ongoing active maintenance of the disposal site following closure.

12

13 The long-term performance of the disposal site depends on the stability of the natural

14 environment of the site, the disposal facility design, and the physical stability of waste disposed

15 of at the facility. Disruptive events that are part of the natural environment have the potential to

16 significantly degrade waste isolation by directly or indirectly affecting the engineered barriers or

17 the wasteform. In general, disposal sites should not be susceptible to erosion, flooding,

18 seismicity, or other disruptive events to such a degree or frequency that waste isolation is

19 compromised. In addition to natural site instabilities, waste and disposal facilities also may be

20 subject to instabilities because of waste characteristics (e.g., differential settling caused by

21 voids in the waste) or facility design (e.g., long-term physical instability of vaults due to

22 cracking). The relative importance of these processes may vary from site to site, and the level

23 of detail of the review is expected to vary accordingly. Review areas are expected to include,

24 but not necessarily be limited to, the technical areas described in 10 CFR 61.13(d) (i.e., erosion,

25 mass wasting, slope failure, settlement of wastes and backfill, infiltration through covers over

26 disposal areas and adjacent soils, and surface drainage of the disposal site).

27

28 7.1.1 Siting Considerations

29

30 The performance objective for site stability (10 CFR 61.44) requires, in part, that facilities be

31 sited to achieve long-term stability. Although a waste determination may pertain to disposal in a

32 facility that already has been sited (e.g., in-situ stabilization of residual waste in tanks), the siting

33 considerations described in 10 CFR 61.50 should be reviewed because many of them identify

34 processes that may affect long-term disposal site stability.1 Processes that may affect site

35 stability include, but are not necessarily limited to, flooding, runoff from upstream drainage,

36 erosion, water table fluctuation, discharge to surface waters on the disposal site, subsurface

37 geologic processes (e.g., seismic activity), slumping, landsliding, weathering, retrieval of

38 subsurface natural resources, and activities at nearby facilities that could affect waste isolation.

39 The reviewer should evaluate the consistency of the disposal site with the siting considerations.

40 If there is significant potential for site instability, the reviewer should evaluate the measures

41 taken to assure waste isolation despite the potential site instabilities.

42

1

Another important purpose of the disposal site suitability requirements of 10 CFR 61.50 is to ensure that new waste

sites are located in areas that can be modeled defensibly and monitored effectively. Therefore, some of the siting

requirements, such as avoiding areas where nearby facilities or activities would significantly mask environmental

monitoring programs, are not related to site stability.

7-1
1 7.1.1.1 Flooding and Water Table Fluctuation

2

3 Flooding, ponding, and periodic immersion of waste due to water table fluctuation all can affect

4 the stability of the waste and disposal facility by accelerating wasteform and barrier degradation.

5 To assess the potential for flooding and immersion of the waste due to water table fluctuation,

6 the reviewer should evaluate site-specific hydrologic data, as described in Section 1.1.3.5. This

7 includes evaluating rainfall intensity, the time of concentration of rainfall events, rainfall

8 distributions, infiltration losses and surface runoff, and how these factors are considered in

9 selecting probable maximum flood and the design basis flooding event. Estimates of the

10 probable maximum flood and design basis flooding event should be consistent with climate

11 projections that cover the full duration of the performance period, including uncertainties in

12 those projections (see Section 4.3.1.1.3). Additional guidance on reviewing flooding information

13 is provided in NUREG-1620 (NRC, 2003a, Section 3) and other U.S. Nuclear Regulatory

14 Commission (NRC) guidance documents (NRC, 2005a, 2002).

15

16 To evaluate the potential for inundation of the waste by water table fluctuation, the reviewer

17 should evaluate the historical record of water table depths in the area as well as information

18 about the seasonal fluctuation of the depth of the water table. The reviewer should evaluate

19 information about the wells from which the water table data were taken, including information

20 about temporary surface features (e.g., paved areas on the surface near disposal units) that

21 could artificially depress the water table elevation in wells near the proposed disposal site. In

22 addition, if the waste is located near the zone of water table fluctuation, the reviewer should

23 assess the potential rise in the water table due to potential increases in precipitation that could

24 be caused by natural climate change during the 10,000-year performance period. As discussed

25 in Section 4.3.1.1.3, the sensitivity of water table elevation to anthropogenic climate change can

26 be assessed by assuming any projected change in the water table elevation due to climate

27 change will occur sooner than expected due to natural climate cycling. If wastes may be

28 located in the zone of water table fluctuation during the performance period, the reviewer should

29 examine the technical basis for the predicted effect of the periodic inundation of the waste on

30 the stability of the wasteform and relevant engineered barriers.

31

32 7.1.1.2 Surface Geologic Processes

33

34 Surface geologic processes such as erosion, mass wasting, slumping, and landsliding can have

35 a significant effect on disposal site stability. Of the four sites discussed in this guidance, these

36 processes are expected to have the greatest effect on the stability of disposal areas at the West

37 Valley site. The reviewer should assess the potential for significant geological surface

38 processes by reviewing historical information about such processes in the area (e.g., historical

39 records of landslides near the site) and by reviewing information about site geomorphology as

40 described in Section 1.1.3.4. The potential for surface geologic processes to affect site stability

41 should account for short duration, large magnitude events (e.g., design basis rainfall events).

42 The frequency and magnitude of these events should be consistent with climate states

43 projected to occur during the performance period. Because there are other large sources of

44 uncertainty in the prediction of surface geologic processes, including uncertainty resulting from

45 present-day variability in rainfall events, predictions may not be sensitive to uncertainty in future

46 climate states. If site stability is sensitive to uncertainty in future climate states, staff should

47 incorporate current information regarding climate change into the review, as appropriate.

48

49 The reviewer should evaluate the design of engineered barriers proposed to provide long-term

50 erosion protection. While active maintenance of erosion control systems may be assumed

7-2
1 during a period of institutional controls (100 years or less; see Section 4.1.1.1), longer term

2 erosion protection should rely on robust passive controls. To assess erosion control barriers,

3 the reviewer should consider rock durability; gradation; cover design; stability calculations for

4 the top slope, side slope, and apron for any cover; and other construction considerations that

5 are important to the performance of the erosion control system. Additional guidance about

6 reviewing the design of erosion control barriers is available in NUREG-1623 (NRC, 2002). As

7 described in NUREG-1623 and NUREG-1620 (NRC, 2003a, 2002), a review of proposed

8 erosion control measures also includes an assessment of the response of the engineered

9 system to flooding and precipitation events. Specifically, erosion barrier designs should account

10 for the selection of an appropriate design basis flood or rainfall event, control of gully initiation

11 and gully development, and the occurrence of flow concentrations and drainage network

12 development. As noted in Section 7.1.1.1, estimates of the design basis flood or rainfall event

13 should be consistent with climate projections that cover the full duration of the performance

14 period, including uncertainties in those projections.

15

16 7.1.1.3 Subsurface Geologic Processes

17

18 The reviewer should assess the potential for subsurface geologic processes, such as faulting or

19 seismic activity, to affect the site and proposed waste containment structures. For example,

20 although earthquakes are not frequent at the Savannah River Site, the Charleston earthquake

21 of 1886 had a magnitude estimate of M 7.3 with an epicenter approximately 144 km [90 mi] from

22 the Savannah River Site (NRC, 2005b). Such history indicates the need to evaluate the seismic

23 stability of the proposed waste containment structures and supporting soils; historic seismic

24 data should be reviewed in light of the most recent understandings of seismicity in the region

25 should be reviewed. The evaluation should include recurrence intervals, magnitudes, and

26 durations, as well as factors that contribute to peak ground acceleration such as underlying

27 geologic structures, and the stratigraphy and lithologies of the site. The predicted effects of

28 seismic events on waste isolation should be evaluated, and any aspects of the disposal plans

29 designed to mitigate the potential effects of seismic events on waste isolation should be

30 reviewed. Additional guidance on reviewing information related to seismic events is provided in

31 NUREG-1804 (NRC, 2003b).

32

33 Vulcanism is not expected to affect the stability of any of the sites discussed in this guidance.

34 Furthermore, the dose to an individual directly intruding into waste (see Section 5) is expected

35 to bound the probability-weighted potential doses due to vulcanism. For these reasons,

36 reviewers are not expected to assess the potential impacts of vulcanism unless new information

37 becomes available that indicates that (1) the potential for vulcanism at any of the relevant sites

38 is substantially greater than currently estimated and (2) the effects of vulcanism may not be

39 bounded by the dose to a potential inadvertent intruder.

40

41 7.1.1.4 Other Processes

42

43 Other natural processes may affect the long-term stability of the disposal site. These processes

44 can include biological processes such as biointrusion into waste or closure caps (e.g., by plant

45 roots or burrowing animals), weather-related hazards such as tornadoes and hurricanes, or

46 other hazards such as fires. During the operations period and the period of active institutional

47 controls, it is anticipated that DOE will have operational procedures (e.g., fire control) to limit the

48 effects of these processes. For the period following the end of institutional controls, these

49 processes should be considered on a case-by-case basis, depending on their potential to

50 disrupt the waste isolation capabilities of the disposal site. In many cases involving waste

7-3
1 buried at several meters depth, occasional surface events such as tornadoes and fires are not

2 expected to have a significant effect on disposal facility stability; one notable exception is for

3 evapotranspiration covers, because the plant community is susceptible to surface events such

4 as fires. The potential effects of near-surface processes on engineered barriers should be

5 bounded and, if necessary, evaluated in greater detail.

6

7 In addition to these natural processes, human activities also may affect site stability. For

8 example, the siting requirements of 10 CFR 61.50 indicate potential concerns associated with.

9 retrieval of natural resources, activities at neighboring facilities, and population growth.

10 Reviewers should assume that DOE will limit the effects of anthropogenic disruptive processes

11 during the period of institutional controls (e.g., by limiting access to the site). To evaluate the

12 expected impact of human activities occurring after the institutional control period, the reviewer

13 should evaluate whether stabilizing features of the site will sufficiently limit the impact of human

14 activities on site stability. Because reprocessing waste typically includes long-lived

15 radionuclides, it would be unrealistic to attempt to predict population growth and future human

16 activities that may occur at the site during the entire period of interest (i.e., thousands of years).

17 Thus the reviewer should evaluate elements of the site designed to limit human intrusion

18 (e.g., disposal depth, recognizable wasteform, engineered intruder barriers) and determine

19 whether they provide reasonable assurance that human activities will not adversely affect site

20 stability during the performance period.

21

22 7.1.2 Waste and Facility Stability

23

24 In addition to the stability of the natural site, compliance with the performance objective for

25 disposal site stability depends on the stability of the waste and engineered barriers of the

26 disposal facility. Some of the concerns regarding the stability of low-level waste are related to

27 the stability of typical commercial Class A wastes, such as contaminated lab trash, clothing, or

28 plastics, and are not expected to be relevant to waste determinations. However, other aspects

29 of the stability of wastes described in 10 CFR 61.56(b), such as the structural stability of waste

30 under the overburden expected after site closure, the effect of radiation and changing chemical

31 conditions on the structural stability of the waste, the presence of free water in the waste, and

32 the presence of void spaces in the waste (e.g., in abandoned equipment), may be pertinent to

33 incidental wastes and should be reviewed. Similarly, the technical areas expected to affect

34 disposal site stability described in 10 CFR 61.51, including (1) the design of covers to limit water

35 infiltration, to direct water away from the waste, and to resist degradation by surface geologic

36 and biotic processes; (2) the design of surface features to direct surface water drainage away

37 from disposal units at velocities and gradients that will not result in erosion;- and (3) the design

38 of the disposal site to minimize the contact of percolating or standing water with wastes after

39 disposal are all expected to be relevant to an assessment of disposal facility stability in the

40 context of a waste determination.

41

42 In addition to the stability concerns specifically described in 10 CFR Part 61, the reviewer

43 should also evaluate the potential for structural degradation of wasteforms and containment

44 structures (e.g., tanks, vaults) more specific to waste determinations (see Section 4.3.3). For

45 example, in many cases, waste may be mixed with or encapsulated by a cementitious material.

46 If so, the reviewer should evaluate the potential for structural degradation due to leaching,

47 sulfate attack, carbonation, corrosion of embedded metals, and cracking caused by various

48 mechanisms (e.g., shrinkage, differential settling, seismic activity) (see Section 4.3.2.2).

49 Additional guidance about evaluating the degradation of cementitious materials is available in

50 NUREG/CR-5542 (Walton, et al., 1990) and NUREG/CR-5666 (Clifton and Knab, 1989).

7-4
1 Degradation of the wasteform and containment facilities can increase groundwater penetration

2 into the waste and can provide enhanced paths for release of radionuclides. Typically, there

3 are large uncertainties associated with predictions of long-term wasteform degradation and

4 facility stability, and simplified analyses may bound the expected degradation (and the effects of

5 this degradation on performance) projected to occur during the performance period.

6

7 7.2 Review Procedures

8

9 To evaluate compliance with the site stability performance objective (10 CFR 61.44), the

10 reviewer should assess the expected occurrence of the disruptive processes described in

11 Section 7.1 and evaluate the potential effects of the disruptive processes on disposal facility

12 performance. The level of detail of the review should depend on the potential for significant site

13 instability (e.g., flooding, erosion, seismicity) and the degree to which disruptive processes

14 could affect disposal facility performance. If the disposal site has a significant potential for

15 instability, the reviewer should perform a detailed review of the processes that could cause

16 instability and the elements of the proposed facility designed to ensure waste isolation in light of

17 the potential instabilities. If, on the other hand, there is little potential for significant disposal site

18 instability, then the reviewer should conduct a simplified review focusing on the technical bases

19 for this conclusion.

20

21 This part of the review is limited to an assessment of site stability. However, processes that

22 cause significant disposal site instability are expected to affect the long-term performance of the

23 disposal site. For example, increased infiltration due to disruption of a closure cap by

24 biointrusion or erosion may have significant effect on radionuclide release and may need to

25 be considered in the performance assessment (see Section 4). Similarly, structural

26 degradation of wasteforms or intruder barriers would be expected to have a significant effect

27 on the plausibility of potential inadvertent intruder scenarios (see Section 5). Thus, the reviewer

28 should coordinate the review of site stability with the review of compliance with other

29 performance objectives of 10 CFR Part 61, Subpart C. The reviewer should perform the

30 following procedures:

31

32 Confirm that the evaluation of flooding scenarios has accounted for flooding of adjacent

33 streams, as applicable, and localized flooding of drainage channels and protective

34 features. Verify that DOE has properly used the probable maximum

35 precipitation/probable maximum flood in determining the design flood event (NRC, 2002,

36 Appendix D; 2003a, Section 3.2.2).

37

38 Confirm that the probable maximum flood is consistent with, but not based solely on an

39 extrapolation of the historic flood record. Ensure that the technical basis for the

40 probable maximum flood includes calculations based on the most severe reasonably

41 possible rainfall events that could occur as a result of a combination of the most severe

42 meteorological conditions occurring over a watershed (probable maximum precipitation).

43

44 Verify that estimates of the probable maximum precipitation and probable maximum

45 flood are consistent with climate states that are expected to occur during the

46 performance period. Verify that the effects of uncertainties in projected climate states

47 are appropriately incorporated into or bounded by estimates of the probable maximum

48 precipitation and probable maximum flood.

49

7-5
1 If the historic maximum regional floods exceed or closely approximate the proposed

2 probable maximum flood estimates, perform a detailed evaluation to determine the basis

3 for the estimates. Compare basin lag times, rainfall distributions, soil types, and

4 infiltration loss rates to determine whether there is a logical basis for the probable

5 maximum flood values being less than historic floods.

6

7 If DOE uses detailed computer models to support its design flood determinations,

8 confirm the adequacy of the various input parameters to the model, including, but not

9 limited to drainage area, lag times and times of concentration, design rainfall,

10 incremental rainfall amounts, temporal distribution of incremental rainfall, and

11 runoff/infiltration relationships.

12

13 * Determine whether the waste is likely to be located in the zone of water table fluctuation

14 during the 10,000-year performance period. Specifically, the reviewer should:

15

16 Evaluate the historical record of water table depths in the area as well as

17 information about seasonal fluctuations of water table depths. The reviewer

18 should examine precipitation data corresponding to the period of historical water

19 table data to determine whether the water table data were taken during an

20 adequately representative period of precipitation (e.g., that well data do not

21 represent a period of relatively low precipitation).

22

23 Ensure that the assessment of the waste location with respect to the water table

24 is not affected by temporary surface features (e.g., paved areas on the surface

25 near disposal units) that could artificially depress the water table elevation in

26 wells near the proposed disposal site.

27

28 Determine whether the waste may be located in the zone of water table

29 fluctuation during the 10,000-year performance period because of potential

30 changes in precipitation due to climate change. Note that either a rise or fall in

31 the water table (due to wetter or drier future climates) could cause the waste to

32 be located in the zone of water table fluctuation, depending on whether the waste

33 is currently located above or below the water table (e.g., some tanks in H tank

34 farm at SRS are partially submerged). Evaluate the potential impacts of

35 anthropogenic climate change by assuming that changes in water table elevation

36 may occur sooner than would be predicted based on natural climate cycling.

37

38 If the waste may be located in the zone of water table fluctuation during the

39 performance period, examine the technical basis for the predicted stability of the

40 disposal site and wasteform in detail, and ensure that the potential effects of

41 water table fluctuation on disposal site stability have been adequately

42 represented or bounded (e.g., effects on wasteform degradation, barrier

43 degradation, sudden radionuclide releases due to episodic submersion of waste).

44

45 * Verify that the analysis of potential erosion at the site includes an assessment of floods,

46 flood velocities, design features, and rock durability that is comparable to those

47 described in NUREG-1623 (NRC, 2002, Appendix D).

48

7-6
1 Confirm that estimates of the potential for surface geologic processes such as erosion,

2 slumping, slope failure, and landsliding are consistent with historical site information

3 (e.g., information about landslides at the site) and site geomorphology.

4

5 * Verify that estimates of the potential effects of surface geologic processes, including

6 erosion, slumping, slope failure, and landsliding, account for short-duration, large

7 magnitude events (e.g., design basis rainfall events).

8

9 0 Verify that the analysis of potential erosion, slumping, slope failure, and landsliding are

10 consistent with projections of climactic conditions that cover the duration of the

11 performance period, including potential changes in the frequency or magnitude of

12 short-duration, large magnitude events.

13

14 Evaluate the sensitivity of site stability to the timing of the effects of climate change

15 (e.g., changes in precipitation, infiltration, flooding, soil saturation, water table depth,

16 erosion, and landsliding) as a means to evaluate the potential effects of anthropogenic

17 processes affecting climate change.

18

19 If the estimated impacts of flooding, water table fluctuation, or surface geologic

20 processes are sensitive to uncertainty in climate change, consider bounding

21 assumptions based on current information about climate change, as appropriate.

22

23 If erosion is expected to have a significant effect on site stability, evaluate whether the

24 erosion protection design is sufficient to avoid the need for ongoing active maintenance

25 at the site. Specifically, determine the adequacy of the following technical areas, as

26 appropriate to the proposed design:

27

28 Treatment of the banks of natural channels, including armoring and designs to

29 place riprap as a protective measure against flood erosion;

30

31 Stability estimates for the top slope, side slopes, and apron, including design flow

32 rate, depth of flow, design discharge, angle of repose, specific gravity, rock sizes,

33 and other parameters;

34

35 The design of diversion channels, outlets, and discharge areas, including the

36 parameters used to define the erosion protection such as flow rates, flow depths,

37 shear stresses, erosion protection (riprap), rock size, and the effects of

38 sediment accumulation;

39

40 Rock durability testing of proposed rock sources, especially with regard to clay

41 content, to ensure that durable rock will be used;

42

43 - Determination of allowable shear stresses and permissible velocities for any soil

44 or vegetative cover, including an assessment of the cover performance in a

45 degraded state;

46

47 - Information on types of vegetation proposed and their abilities to survive

48 natural phenomena and expected natural vegetation progression (e.g., grass

49 cover being replaced by tree cover over time);

50

7-7
1 -. Construction considerations such as plans, specifications, inspection programs,

2 and quality assurance/quality control programs to assure that adequate

3 measures are being taken to construct the design features according to accepted

4 engineering practices; and

5

6 - Information, analyses, and calculations of input parameters to models used.

7

8 Verify that the description of the potential for seismic events is derived from the historical

9 record, paleoseismic studies, or geological analyses. Evaluate recurrence intervals and

10 magnitudes of past events, and determine whether the reported potential for seismic

11 events is consistent with the historical record.

12

13 Determine whether seismic events that are likely to occur during the performance period

14 are likely to have a significant impact on the stability of the disposal facility by causing

15 structural damage to wasteforms or engineered barriers (e.g., cracking of grouted

16 wasteforms or vaults).

17

18 Assess the potential disruption of wasteforms or engineered barriers (e.g., caps

19 designed to limit infiltration) by intrusion of roots or burrowing animals by evaluating

20 biological information relevant to the site. If populations of burrowing animals are

21 identified or if deep-rooted plant species are expected to grow on the site (e.g., if the site

22 is expected to revert to forests) during the performance period, determine whether

23 disposal site features designed to limit the effects of biointrusion are adequate to

24 maintain site stability.

25

26 Determine whether there are natural resources at the site such that exploitation of the

27 natural resources (e.g., mining for mineral ore) would affect site stability. If so,

28 determine whether features of the wasteform or disposal site (e.g., a recognizable

29 wasteform or engineered barriers) would be sufficient to alert individuals to the presence

30 of waste or otherwise limit their impact on site stability (see review procedures related to

31 engineered barriers and wasteform degradation in Sections 4.3.2 and 4.3.3).

32

33 - Determine whether current or expected activities at nearby facilities (e.g., use or

34 decommissioning of neighboring chemical processing facilities on the DOE site) may

35 affect site stability. If so, determine whether disposal site features designed to limit the

36 effects of the activities are sufficiently robust to provide reasonable assurance that site

37 stability will be maintained (see review procedures related to engineered barriers and

38 wasteform degradation in Sections 4.3.2 and 4.3.3).

39

40 If there are significant quantities of long-lived radionuclides at the site, determine

41 whether wasteforms are likely to remain sufficiently identifiable and intruder barriers are

42 likely to remain sufficiently robust to provide reasonable assurance that human activities

43 will not compromise site stability thousands of years after site closure (see review

44 procedures related to engineered barriers and wasteform degradation in Sections 4.3.2

45 and 4.3.3).

46

47 Determine whether disruptive events such as hurricanes, tornadoes, and fires could

48 cause significant site instability, and if so, what aspects of the facility are designed to

49 maintain site stability if the disruptive events occur.

50

7-8
1 ° Verify that the waste will remain structurally stable under the overburden expected after

2 site closure.

3

4 • Verify that the effects of radiation and any changes expected in chemical conditions

5 (e.g., because of infiltrating groundwater or corrosion of embedded metal) will not cause

6 instability of the waste as emplaced after closure.

7

8 Verify that the presence of free water in the waste will be minimal (e.g., less than

9 1 percent by volume) and that there will not be significant void spaces in the waste

10 (e.g., inside abandoned equipment) that could cause differential settling of the waste or

11 engineered barriers.

12

13 Verify that covers have been designed to limit water infiltration and to direct infiltrating

14 water away from the waste. Verify that any surface features of the disposal facility have

15 been designed to direct surface water drainage away from disposal units at velocities

16 and gradients that will not result in erosion.

17

18 If wastes will be mixed with or encapsulated by cementitious material, determine the

19 potential for significant structural degradation due to leaching, sulfate attack,

20 carbonation, or corrosion of embedded metals. Because of the large uncertainty in

21 potential degradation through these processes, use simplified analyses to bound the

22 expected degradation during the performance period. If there is significant potential for

23 structural degradation of the wasteform or cementitious engineered barriers because of

24 these processes, the potential effects on radionuclides release or plausible inadvertent

25 intruder scenarios should be represented or bounded in the performance assessment

26 (see Section 3) or inadvertent intruder analysis (see Section 4).

27

28 7.3 References

29

30 Clifton, J.R. and L.I. Knab, "Service Life of Concrete." Final Report. NUREG/CR-5466.

31 September 1989.

32

33 U.S. Nuclear Regulatory Commission (NRC). "Design of Erosion Protection for Long-Term

34 Stabilization." Final Report. NUREG-1623. September 2002.

35

36 . "Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites

37 Under Title II of the Uranium Mill Tailings Radiation Control Act of 1978." NUREG-1620. June

38 2003a.

39

40 "Yucca Mountain Review Plan." NUREG-1804. July 2003b.

41

42 "Consolidated NMSS Decommissioning Guidance. Updates to Implement the License

43 Termination Rule Analysis." Draft Report for Comment. NUREG-1 757, Supplement 1.

44 September 2005a.

45

46 . "Final Safety Evaluation Report on the Construction Authorization for the Mixed Oxide

47 Fuel Fabrication Facility at the Savannah River Site, South Carolina." NUREG-1821. March

48 2005b.

49

7-9
1 Walton, J.C., L.E., Plansky, and R.W. Smith. "Models for Estimation of Service Life of Concrete

2 Barriers in Low-Level Radioactive Waste Disposal." Final Report. NUREG/CR-5542.

3 September 1990.

7-10
1 8 QUALITY ASSURANCE PROGRAM

2

3 Quality assurance, in the context of this guidance document, comprises all of the planned and

4 systematic actions necessary to provide adequate confidence that the applicable incidental

5 waste criteria will be met. An adequate quality assurance program is essential to ensuring that

6 the key information relied upon to make incidental waste determinations is correct and accurate.

7

8 This review verifies that the U.S. Department of Energy (DOE) has applied quality assurance

9 measures to its data collection, analyses, waste determinations, and performance assessments.

10 This guidance document provides risk-informed and performance-based approaches for

11 evaluating quality assurance information. The adequacy of quality assurance measures will be

12 determined using a sample of analyses selected based on their risk significance, and

13 conclusions will be based on impacts of any identified deficiencies on performance. For

14 example, a quality assurance deficiency of a risk-significant element of the performance

15 assessment may have a minor, moderate, or major impact on the results of the analysis. The

16 reviewer should consider both the severity and the pervasiveness of deficiencies when

17 evaluating the adequacy of quality assurance measures. The reviewer should use this

18 guidance in reviewing quality assurance measures that apply to DOE waste determinations and

19 performance assessments. Section 17.6 of NUREG-1757, Volume 1, Revision 1, provides

20 U.S. Nuclear Regulatory Commission (NRC) regulatory guidance pertinent to quality assurance

21 as applied to decommissioning sites (NRC, 2003). The reviewer may consider this guidance

22 when evaluating DOE's quality assurance program as applied to the waste determination.

23

24 8.1 Areas of Review

25

26 The NRC staff should evaluate a sample of the analyses associated with Areas of Review

27 identified in Sections 2-7 of this guidance document. The analyses should be selected based

28 on high or medium risk areas with regard to meeting the performance objectives of

29 10 CFR Part 61, Subpart C, and other applicable criteria. The risk importance of an analysis is

30 likely to vary from facility to facility.

31

32 8.2 Review Procedures

33

34 8.2.1 Data Validity Review Procedures

35

36 The reviewer should examine the data used to support waste determinations and performance

37 assessments to determine whether (1) the data are traceable to their sources through all

38 calculations and data reductions, and the data are transparent in their use and (2) the data have

39 been obtained or qualified under an acceptable quality assurance program, such as but not

40 limited to an NRC-approved quality assurance program developed to meet the requirements of

41 10 CFR Part 50, Appendix B, or are otherwise documented and validated. Specifically, the

42 reviewer should ensure the following conditions are met:

43

44 Data are identified in a manner that facilitates traceability to associated documentation

45 back to the source and clearly identifies qualification status (e.g., qualified, unqualified,

46 or accepted, such as for a physical constant). Traceability is the ability to trace

47 the history, application, or location of an item and like items or activities through

48 recorded identification.

49

8-1
1 * Any changes that affect data identification (e.g., category or use/application) are made in

2 a manner that preserves traceability.

3

4 * Data used as direct input to scientific analysis or performance modeling are qualified or

5 are validated by other comparable methods.

6

7 * If data are not collected under an acceptable quality assurance program, the data are

8 qualified by one or more of the following processes: equivalent quality assurance

9 program, comparison to corroborating data, confirmatory testing, or peer review

10 (NRC, 1988).

11

12 * Documentation regarding data traceability and qualification is transparent and identifies

13 the principal lines of investigation considered. A document is transparent if it is

14 sufficiently detailed as to purpose, method, assumptions, inputs, conclusions,

15 references, and units so that a person technically qualified in the subject can understand

16 the document and ensure its adequacy without recourse to the originator.

17

18 * The data reduction process is described in detail sufficient to allow independent

19 reproducibility by another qualified individual. Data reduction includes processes that

20 change the form 'of expression, quantity of data or values, or number of data items.

21 Verify that data reduction inputs, outputs, and computational methods are documented.

22

23 8.2.2 Software Selection and Development Review Procedures

24

25 The reviewer should assess the software DOE used in the waste determination and

26 performance assessment to determine whether (1) the software has been endorsed for NRC

27 use or (2) DOE has demonstrated that the software adequately represents the processes or

28 systems for which it is intended. The reviewer should evaluate whether the software

29 development and approaches to software validation are planned, controlled, and documented.

30 Planning for validation identifies the validation methods and validation criteria used.

31

32 The reviewer should assess controls applied to software to ensure that the software supporting

33 waste determinations or performance assessments is qualified for use and has been developed,

34 tested, and controlled under suitable conditions.

35

36 Specifically, the reviewer should ensure the following conditions are met:

37

38 . NRC has endorsed the software for use in licensing activities. If the software has been

39 endorsed, then the reviewer would, in general, not need to exercise the review

40 procedures specific to software quality assurance that follow.

41

42 * The software performs intended functions, provides correct solutions, and does not

43 cause adverse unintended results.

44

45 * Software verification and validation activities were planned, documented, and performed

46 for each item of software.

47

48 * Software that was verified and validated and was subsequently changed has undergone

49 additional verification and validation, and documentation of the additional verification and

50 validation has been developed.

8-2
1 * The software development and maintenance process proceeded in a planned, traceable,

2 and orderly manner, using a defined software life-cycle methodology.

3

4 ° A software configuration management system has been established.

5

6 ° Requirements controlling software procurement and services are established to assure

7 proper verification and validation support, software maintenance, configuration control,

8 and performance of software audits, assessments, or surveys. Requirements for

9 suppliers reporting software errors to the purchaser and, as appropriate, the purchasers

10 reporting software errors to the supplier are identified.

11

12 • If a defect was identified in software that adversely affects the results of previous

13 software application, the condition adverse to quality was documented and controlled.

14

15 8.2.3 Analysis Review Procedures

16

17 The reviewer should assess the analysis to determine that the analysis was transparently

18 documented, the objective and use of the software are described, and the software was not

19 used outside of the range of its intended functions. Specifically, the reviewer should ensure that

20 the following conditions are met:

21

22 • The definition of the objective (intended use) of the software has been provided;

23

24 - The description of the conceptual model implemented in the software is clear;

25

26 • The software has not been used in a manner that is inconsistent with the conceptual

27 model implemented in the software;

28

29 • Identification of inputs to the software and their sources has been provided;

30

31 • Discussion of mathematical and numerical models that are used in the software is

32 provided, including governing equations, formulas, algorithms, and their scientific and

33 mathematical bases;

34

35 • Associated software used, computer calculations performed, and basis to permit

36 traceability of inputs and outputs have been identified;

37

38 * Discussion of initial and boundary conditions is provided;

39

40 - Model limitations (e.g., data available for model development, valid ranges of model

41 application, spatial and temporal scaling) are discussed; and,

42

43 • Software execution is appropriate with the various sources of uncertainties (i.e.,

44 conceptual model, mathematical model, process model, system model, parameters).

45

46

8-3
1 8.3 References

2

3 U.S. Nuclear Regulatory Commission (NRC). "Generic Technical Position on Qualification of

4 Existing Data for High-Level Nuclear Waste Repositories." NUREG-1298. Washington,

5 DC. February 1988.

6

7 . "Consolidated NMSS Decommissioning Guidance." Vols. 1-3. NUREG-1757.

8 Washington, DC. September 2003.

8-4
1 9 DOCUMENTING THE RESULTS OF THE REVIEW

2

3 9.1 General Approach to Documenting Waste

4 Determination Reviews

5

6 As described in the U.S. Nuclear Regulatory Commission's (NRC) implementation plan for

7 waste determination reviews conducted under the Ronald W. Reagan National Defense

8 Authorization Act for Fiscal Year 2005 (NDAA) (NRC,. 2005a), the general approach the NRC

9 staff will use will be similar to previously completed waste-incidental-to-reprocessing (WIR)

10 reviews (NRC, 2000, 2002, 2003). Reviews not conducted under the NDAA will be conducted

11 in a similar manner. As discussed in Section 2, however, due to differences between the

12 criteria in the NDAA and those used in previous NRC reviews, there may be some technical

13 differences in the reviews. This section of the guidance document provides guidance on the

14 process for conducting and documenting a review.

15

16 9.2 Request for Additional Information

17

18 The first step in the review process will be the U.S. Department of Energy's (DOE) submittal of a

19 draft waste determination and supporting documentation, including a performance assessment

20 if necessary. Using the guidance described in Sections 1-8 of this document, the NRC staff will

21 review whether DOE's assumptions, analyses, data, documentation, modeling, and conclusions

22 are technically adequate, accurate, and in accordance with the appropriate waste criteria. If the

23 reviewer does not receive sufficient information to determine that there is reasonable assurance

24 that the waste criteria can be met or if the reviewer has questions about the DOE-provided

25 information, the NRC staff should develop a Request for Additional Information (RAI). An RAI is

26 a list of questions needing DOE responses so NRC staff can complete its review. The staff's

27 RAI should be risk-informed and focus on those areas that are most likely to affect the staff's

28 conclusions. The RAI should be as complete as possible so that only one RAI is needed. In

29 addition to responding to the specific questions raised in the RAI, DOE may decide to revise the

30 waste determination itself, or the supporting documentation or modeling, based on NRC's

31 questions and comments. If the information DOE provided in its initial submittal is sufficient for

32 the reviewer to determine whether there is reasonable assurance that the applicable waste

33 criteria can be met, then the staff does not necessarily need to prepare an RAI and can prepare

34 its Technical Evaluation Report (TER) (see Section 9.3). NRC's role in evaluating waste

35 determinations is consultative; as such, DOE has final authority to determine whether the

36 applicable waste criteria can be met.

37

38 9.3 Technical Evaluation. Report

39

40 The TER documents the NRC staff's analyses and conclusions for a specific waste

41 determination. The TER should include descriptions of DOE's approach, what was reviewed by

42 the staff, the assumptions made in conducting the review, the major sources of uncertainty in

43 DOE's analysis, and the conclusions as to whether there is reasonable assurance that each

44 applicable waste criterion can be met (see Sections 2-7). The amount of discussion in the TER

45 for a specific area should be commensurate with its importance to NRC's conclusions.

46 Examples of areas typically covered in a TER are waste inventory, identification of highly

47 radioactive radionuclides, infiltration, wasteform degradation, near field transport, and

48 hydrology. Specific TER sections may be developed as necessary to evaluate those aspects

49 that are most significant for a specific waste determination. The TER may also include, in an

9-1
1 appendix, recommendations for DOE's consideration; the purpose of the recommendations is to

2 communicate actions that DOE might consider to further improve its waste management

3 approach. These do not need to be implemented for the applicable waste criteria to be met.

4

5 For waste determination reviews conducted under the Ronald W. Reagan National Defense

6 Authorization Act for Fiscal Year 2005 (NDAA) (see Section 2), the TER should also identify the

7 key aspects that are important to assessing compliance with 10 CFR Part 61, Subpart C. These

8 key aspects will be one facet of the NRC's monitoring role under the NDAA for a particular

9 waste determination (see Section 10). Ideally, the detailed technical evaluation will have been

10 completed during consultation with DOE and prior to the initiation of NRC's monitoring activities

11 which begin when DOE issues the final waste determination document. NRC staff should

12 review DOE's final waste determination document and evaluate any differences between it and

13 the draft waste determination document.

14

15 9.4 Public Availability and Project Numbers

16

17 The Commission has directed the staff to ensure that the technical basis for its decisions

18 regarding draft waste determination reviews under the NDAA are as "transparent, traceable,

19 complete, and as open to the public and interested stakeholders as possible" (NRC, 2005b). To

20 fulfill that direction, the documents associated with DOE's waste determinations and NRC's

21 reviews should be made publicly available, both for reviews that are being conducted for sites

22 under the NDAA and those that are not. This includes the waste determinations, supporting

23 references, NRC's RAI, DOE's RAI responses andsupporting references, meeting summaries,

24 TERs, and any other relevant documents submitted by DOE or issued by NRC. One exception

25 may be documents that DOE cannot publicly release because of security concerns. For

26 discussion of public availability of reports related to monitoring under the NDAA, see Section 10.

27

28 For ease of finding and obtaining documents, the NRC staff has established project numbers for

29 incidental waste activities at the sites, as follows: Savannah River Site is PROJ0734, Idaho

30 National Laboratory is PROJ0735, Hanford is PROJ0736, and West Valley is POOM-32.

31 These project numbers should be entered into the "Docket Number" field in NRC's Agencywide

32 Documents Access and Management System (ADAMS).

33

34 9.5 References

35

36 U.S. Nuclear Regulatory Commission (NRC). "Savannah River Site High-Level Waste Tank

37 Closure: Classification of Residual Waste as Incidental." Letter from W. Kane to

38 R.J. Schepens, DOE. June 2000.

39

40 - . "NRC Review of Idaho National Engineering and Environmental Laboratory Draft Waste

41 Incidental to Reprocessing Determination for Sodium-Bearing Waste-Conclusions and

42 Recommendations." Letter from J. Greeves to J. Case, DOE. August 2002.

43

44 . "NRC Review of Idaho Nuclear Technology and Engineering Center Draft Waste

45 Incidental to Reprocessing Determination for Tank Farm Facility Residuals-Conclusions and

46 Recommendations." Letter from L. Kokajko to J. Case, DOE. June 2003.

47

9-2
1 -. "Implementation of New U.S. Nuclear Regulatory Commission Responsibilities Under

2 the National Defense Authorization Act of 2005 in Reviewing Waste Determinations for the

3 U.S. Department of Energy." SECY-05-0073. April 2005a.

4

5 . "Staff Requirements-SECY-05-0073-1mplementation of New U.S. Nuclear

6 Regulatory Commission Responsibilities Under the National Defense Authorization Act of 2005

7 in Reviewing Waste Determinations for the USDOE." SRM-SECY-05-0073. June 2005b.

8

9-3

1 10 NDAA COMPLIANCE MONITORING

2

3 Paragraph (b)(1) of Section 3116 of the Ronald W. Reagan National Defense Authorization Act

4 for Fiscal Year 2005 (NDAA) (see Appendix A) requires that the U.S. Nuclear Regulatory

5 Commission (NRC)" ... in coordination with the covered State, monitor disposal actions taken

6 by the Department of Energy ... for the purpose of assessing compliance with the performance

7 objectives set out in subpart C of part 61 of title 10, Code of Federal Regulations." The NDAA

8 requires that NRC report any noncompliance to Congress, the State, and the U.S. Department

9 of Energy (DOE) as soon as practicable after discovery of the noncompliant conditions and

10 states that NRC's monitoring is subject to judicial review. However, the NRC does not have

11 regulatory or enforcement authority over DOE. The NDAA applies only to South Carolina and

12 Idaho, and these are the States in which NRC would monitor DOE's disposal of incidental

13 waste. NRC does not have a monitoring role at Hanford, because Washington is not included

14 as a covered State in the NDAA.

15

16 For West Valley, the NRC license is currently in abeyance while DOE completes its

17 responsibilities under the West Valley Demonstration Project Act (WVDPA). The WVDPA

18 requires that NRC establish decommissioning criteria for the site. NRC published those criteria

19 in 2002 (NRC, 2002) and included criteria for determining whether certain waste disposed of

20 onsite is incidental waste; however, NRC does not have regulatory or enforcement authority

21 over DOE under the WVDPA. Although the WVDPA does assign a monitoring role to NRC at

22 West Valley, at this point, NRC staff has not performed a technical evaluation of a waste

23 determination at WVDP to assess compliance with safety requirements comparable to the

24 performance objectives in 10 CFR Part 61, Subpart C. Therefore, the West Valley site is not

25 included in the following discussion of monitoring. Monitoring approaches and activities relating

26 to incidental waste disposal actions for WVDP can be included in a revised and updated version

27 of the guidance document when relevant. If the license is reinstated and responsibility for the

28 entire site returns to the licensee (the New York State Energy Research and Development

29 Authority [NYSERDA]), NRC will retain the same monitoring and inspection responsibilities that

30 it has for other licensees under the Atomic Energy Act with respect to ensuring that the site

31 meets all applicable regulatory requirements.

32

33 10.1 Overall Approach and Scope

34

35 The NDAA requires NRC to monitor DOE's disposal actions to assess compliance with the

36 performance objectives in 10 CFR Part 61, Subpart C. The NDAA also directs the NRC to issue

37 a report to Congress, the covered State, and DOE if it determines that disposal actions DOE

38 takes are not in compliance with the performance objectives. The act does not provide NRC

39 with any regulatory or enforcement authority. Accordingly, NRC monitoring activities will be

40 limited to those activities deemed necessary to assess whether there is reasonable assurance

41 that compliance with the performance objectives will be achieved.

42

43 As stated in SECY-05-0073 (NRC, 2005), the staff intends to carry out its monitoring role in a

44 risk-informed and performance-based manner. A cornerstone of the staffs intended approach

45 is to identify key aspects of DOE's disposal actions that should be monitored. Identifying these

46 key aspects is expected to be part of a technical evaluation to assess whether DOE's proposed

47 waste disposal actions will comply with 10 CFR Part 61, Subpart C, performance objectives.

48

10-1
1 To the extent possible, the staff will conduct its technical evaluation during the consultation

2 process and leverage insights gained through the consultation process to identify key aspects of

3 DOE's waste disposal system that should be monitored to assess compliance with NRC's

4 10 CFR Part 61 performance objectives. Staff intends to use risk insights gained through its

5 technical evaluation to gauge the relative importance of key modeling assumptions or model

6 parameters DOE uses to demonstrate performance objectives will be met. Assumptions,

7 parameters, and features that are expected to have a large influence on the performance

8 demonstration and/or have relatively large uncertainties will be considered key aspects of the

9 waste disposal system. Monitoring is a good mechanism to manage those uncertainties, and

10 NRC staff should monitor the disposal actions with which these key assumptions, parameters,

11 and features are associated. Monitoring is also a way to evaluate new information that may

12 potentially support previous information or assumptions. In either case, the performance

13 assessment in DOE's final waste determination document to demonstrate compliance with the

14 performance objectives must continue to be adequately supported. System description, data

15 sufficiency, data uncertainty, model uncertainty, and model support ensure the performance

16 assessment is technically adequate; these are the main elements in the general technical

17 review procedures as described in the early part of this guidance document. NRC staff also

18 recognizes that some uncertainties will exist at the time that decisions are to be made.

19 Although it is not practicable to require a performance assessment to be assumption free, it is

20 reasonable to expect that key assumptions have a technical basis supported by data and

21 information. Monitoring is not to be used as a substitute for inadequate information, but rather

22 to manage the uncertainty and to support the previous determination of adequacy considering

23 uncertainty. Focusing on the most risk-significant aspects of the performance demonstration

24 will allow staff to optimize its resources.

25

26 The NDAA indicates NRC must monitor DOE's disposal actions to determine whether the

27 actions are in compliance with the performance objectives of 10 CFR Part 61, Subpart C.

28 Because the performance objectives include a general requirement that there is reasonable

29 assurance that exposures to humans will not exceed the limits established in 10 CFR 61.41

30 through 44, DOE's disposal actions would be out of compliance if NRC no longer had

31 reasonable assurance that the requirements of 10 CFR 61.41 through 44 would be met. As

32 described in Sections 4-7 of this guidance document, NRC staff typically derives assurance that

33 the requirements of 10 CFR 61.41 through 44 will be met on predictions of long-term site

34 performance. Therefore, monitoring to assess compliance with the performance objectives is

35 expected to include activities necessary to maintain confidence in DOE's predictions of

36 long-term site performance. Although environmental monitoring (i.e., monitoring the

37 environment for changes and collecting environmental data) is expected to provide the most

38 clear and straightforward way to assess the performance of a disposal facility, in practice, there

39 are limitations to solely relying on environmental data to evaluate the performance of the type of

40 disposal facilities that are the subject of DOE's waste determinations. Because DOE typically

41 relies on a number of engineered features (e.g., grout, concrete vaults, specialized covers) to

42 close their facilities, it may be several decades or centuries before any radioactive materials are

43 expected to be released from the disposal facility and could thereafter be detected. While

44 observing DOE actions and reviewing environmental data are expected to be components of

45 NRC's monitoring activities, building confidence in DOE's selection of parameters and models

46 will be a critical monitoring activity. Accordingly, it is important for staff to use the performance

47 assessment to identify those aspects of the disposal system that have the largest influence on

48 performance so that these areas can be the focus of NRC's monitoring activities. In addition, it

49 is important for staff to monitor those parts of the disposal system with the greatest amount of

50 uncertainty that NRC's performance objectives will be met.

10-2
1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

The staffs approach to assessing compliance with the performance objectives will generally

consist of two primary activities: (1) conducting technical reviews of DOE data and analyses

and (2) physically observing DOE's disposal actions through onsite visits. Table 10-1 shows

the expected primary monitoring activities for assessing compliance with each of the

performance objectives.

Based on the NRC staffs technical evaluation, NRC may conclude that a number of key

aspects associated with DOE's performance assessment should be monitored to assess

compliance with the performance objectives. For example, DOE may be able to demonstrate

that the performance objectives will be met based upon a demonstrably conservative analysis,

in which case, less uncertainty would exist regarding assumptions and parameters important to

meeting the performance objectives. On the other hand, the staffs technical evaluation may

Table 10-1. U.S. Nuclear Regulatory Commission's Primary Monitoring Activities for Each of the

Performance Objectives

Performance Objective Primary Monitoring Activities

10 CFR 61.40-General Requirements Addressed through compliance with

10 CFR 61.41-44

10 CFR 61.41 -Protection of General Population 1. Review information and observe actions

relevant to key aspects important to

demonstrating compliance with 10 CFR 61.41

2. Review DOE environmental monitoring results

3. Review DOE sampling data and inventory

estimates

4. Observe environmental sampling and data

collection activities

5. Review updates to DOE's performance

assessment

10 CFR 61.42-Protection of Inadvertent Intruder 1. Review information and observe actions

relevant to key aspects important to

demonstrating compliance with 10 CFR 61.42

2. Review intruder barrier and erosion control

designs that can be used to prevent intruder

scenarios

3. Similar compliance monitoring activities that

are affiliated with 10 CFR 61.41

10 CFR 61.43-Protection of Individuals During 1. Review DOE worker and public radiation

Operations records

2. Review DOE and covered state environmental

monitoring data, offsite dose calculations, and

radiological assessments

10 CFR 61.44-Site Stability 1. Observe construction of engineering features

and their maintenance

2. Observe for signs of structural failure

3. Review design and design changes of the

engineered features

10-3
1 conclude that there are key aspects of the performance assessment where a significant amount

2 of uncertainty exists and continues to exist during the decision making process. In either case,

3 staff should remain aware of the implementation of DOE's waste management approach and

4 any developments that may challenge the support of DOE's assumptions or analyses. The key

5 aspects listed in the TER are not intended as an all-inclusive list of monitoring activities, and the

6 number or types of monitored activities may change as more is learned about the disposal

7 methods or as DOE's disposal plans proceed. NRC staff performing the monitoring should

8 evaluate revisions to DOE's modeling or disposal plans.

9

10 Once NRC has completed its technical evaluation and DOE has issued a final waste

11 determination, NRC staff should have completed or be in the process of completing a

12 compliance monitoring plan for carrying out its specific monitoring activities. Ideally, NRC will

13 develop and be prepared to implement its monitoring plan before DOE initiates waste disposal

14 activities. Consultations with DOE should ensure, to the extent practical, that NRC's

15 compliance monitoring plan is in place before waste determination activities begin. Waste

16 removal or retrieval may be the exception; this disposal action is different from other waste

17 determination activities in that waste retrieval may be in progress when the final waste

18 determination has been issued, or waste retrieval activities may be completed. NRC staff will.

19 monitor waste retrieval activities after DOE issues the final waste determination. NRC's

20 compliance monitoring plan will identify the specific activities that will be undertaken to assess

21 DOE's compliance with each of the performance objectives. Specific elements of the monitoring

22 plan will be established based upon the individual waste determination. However, some

23 elements are expected to be common to most monitoring plans and important to waste isolation,

24 including (1) reviewing the final disposal facility inventory of radionuclides, (2) reviewing updates

25 to DOE's performance assessment, (3) observing the construction and maintenance of

26 engineered systems (e.g., vaults and covers), (4) reviewing radiation records, (5) reviewing

27 environmental data, and (6) observing environmental sampling.

28

29 Under DOE Order 435.1, DOE must maintain its performance assessment, which is used as the

30 primary basis for demonstrating that the performance objectives will be met during the

31 compliance period. Performance assessment maintenance can include conducting research,

32 implementing field studies, and performing monitoring needed to address uncertainties or gaps

33 in existing data. Under DOE Order 435.1, DOE must annually determine the continued

34 adequacy of its performance assessment based upon the results of its data collection and

35 analysis from its research, field studies, and monitoring. In addition, DOE must provide annual

36 summaries of conclusions and recommendations from its performance assessment and identify

37 any needed revisions. Because someof the data collected and/or research undertaken by DOE

38 to maintain its performance assessment could provide additional support for some of the key

39 aspects identified by the staff in its TER, DOE's activities are expected to have a direct bearing

40 on NRC's monitoring activities. In addition, under DOE Order 435.1, DOE must develop a

41 monitoring plan for internal use, and NRC staff may request a copy of this plan. The

42 environmental monitoring plan is designed to address measurement and evaluation of releases,

43 migration of radionuclides, disposal unit subsidence, and changes in disposal facility and

44 disposal site parameters that may affect long-term performance.

45

46 A key part of NRC's monitoring plan development is coordinating with the covered State to

47 identify monitoring activities that will help NRC perform its responsibilities under the NDAA. To

48 the extent that it is able, NRC will take full advantage of the covered State's regulatory programs

49 related to monitoring of the disposal facility. For example, the covered State may have specific

10-4
1 requirements related to well construction and sampling that may help NRC ensure that wells are

2 properly installed and reliable samples are collected and analyzed.

3

4 Once NRC develops a compliance monitoring plan, a copy will be provided to DOE and the

5 covered State. Further, compliance monitoring plans will be publicly available and accessible

6 through NRC's website. After NRC has developed its monitoring plan for a specific waste

7 determination, it will perform the activities described in the plan. Plan implementation may

8 begin with NRC sending a written request to DOE for the data, studies, or analyses identified in

9 the monitoring plan. NRC staff will also request that DOE provide a schedule of its waste

10 disposal activities. After NRC has received the requested information from DOE, staff will

11 technically review the information. In addition, staff should coordinate an onsite observation

12 schedule with DOE and the covered State.

13

14 If NRC is unable to obtain needed information from DOE in order to complete NRC's monitoring

15 activities, key assumptions and aspects relied upon to demonstrate compliance with the

16 performance objectives may no longer be adequately supported, and NRC staff may no longer

17 have reasonable assurance that the performance objectives will be met. In this case, NRC will

18 inform DOE, Congress and the covered State by issuing a Type III noncompliance notification

19 letter (see Section 10.4.3).

20

21 If, during the technical reviews or onsite observations, NRC staff obtains data and information

22 that indicate that key assumptions and aspects relied upon to demonstrate compliance; with one

23 or more performance objectives are no longer adequately supported, the staff will evaluate the

24 information to determine its significance in the context of potential noncompliance with a

25 performance objective. Staff will need to evaluate whether one or more of the performance

26 objectives will likely not be met. Even if a key assumption relied upon to demonstrate

27 compliance with one or more performance objectives is no longer supported, DOE may be able

28 to demonstrate that the performance objective(s) will be met by demonstrating that the key

29 assumption is compensated by conservative assumptions in other parts of the analysis. It is

30 anticipated that the performance assessment overall may be an iterative process because an

31 individual component's importance can be relative to the performance of other components

32 (e.g., subsequent iterative analyses would need to clearly show that an unsupported

33 assumption would cause the performance objective[s] not to be met). Understanding the

34 importance of parameters and model components and their interrelationships with one another

35 is best accomplished by exploring a variety of approaches. Accordingly, the staff will need to

36 confer with DOE before concluding that there is no longer reasonable assurance that a

37 performance objective will be met in the future. Once the staff determines that there is no

38 longer reasonable assurance that a performance objective will be met, NRC has an obligation to

39 notify Congress, the covered State, and DOE as soon as practicable in the form of a notification

40 letter (Type II) from the Chairman of NRC. A Type I letter would state that there are sufficient

41 indications that DOE is currently not meeting the requirements of 10 CFR 61.41-61.44. The

42 types of notification letters are discussed in more detail in Section 10.4.3.

43

44 NRC staff should document the findings of its assessment in a periodic compliance monitoring

45 report. At this time the staff intends to develop these periodic reports on an annual basis (see

46 Section 10.4.2). This periodic report should identify the status of monitoring activities

47 (i.e., open, closed, open-noncompliant). In addition, the periodic report will identify changes

48 that should be made to NRC's monitoring activities for the upcoming year. NRC will also

49 request that DOE provide an updated schedule of waste disposal activities for NRC planning

50 purposes (e.g., to enable the observation of disposal actions). The periodic compliance

10-5
1 monitoring report should document any significant changes to the disposal design. If the

2 changes are significant, the periodic monitoring report should recommend that the compliance

3 monitoring plan be revised. It is probable that the compliance monitoring plan will need to be

4 updated and revised as plans for the disposal site are revised or finalized. Monitoring activities

5 should focus on risk-significant features and processes that are part of finalized designs for

6 engineered barriers and not on the details for designs that are still tentative or under

7 development. For example, a final decision on erosion and infiltration controls may not be made

8 until years after disposal actions involving grouting are expected to be completed. Similarly,

9 new designs not considered in the original waste determination may be developed based on

10 new research. Updating monitoring activity details during revisions to the monitoring plan

11 would, therefore, need to reflect and emphasize the revised or final design plans.

12

13 The NDAA does not specify how long the NRC is responsible for assessing compliance,

14 therefore, the monitoring activity is indefinite. In general, it is envisioned that the level of

15 NRC-required effort will vary over time, with an initially higher level of effort needed early in the

16 process to review information and observe actions that may potentially support key assumptions

17 and parameters made as part of DOE's disposal actions. As the monitoring activities close, the

18 scope of NRC's monitoring efforts should be reduced. Figure 10-1 shows the general process

19 the Commission will follow to carry out its monitoring responsibilities and when issuing Type II

20 and III noncompliance notification letters.

21

22 10.2 Coordinating With the Covered State

23

24 As previously stated, a key part of NRC's monitoring responsibilities under the NDAA is to

25 coordinate monitoring activities with the covered State. As part of the general monitoring

26 process, it is recommended that discussions with the covered State concerning monitoring

27 occur during the waste determination review. Discussions with the State will enable NRC staff

28 to determine the type of activities the State will be undertaking in terms of monitoring

29 compliance with its regulatory requirements and enable the covered State to understand the

30 type of activities that NRC will be undertaking. Insights gained through these discussions may

31 help the two parties coordinate their activities in order for NRC to meet its NDAA monitoring

32 responsibilities. In some cases, NRC may be able to rely upon State-obtained information.

33 NRC will need to periodically communicate with the State to ascertain any changes in the

34 State's permitting requirements because changes may affect the type and frequency of some of

35 the DOE-collected data.

36

37 NRC staff will keep the covered State informed of its monitoring activities. NRC staff should, at

38 appropriate times, observe specific DOE activities at the site and review records. The covered

39 State will be notified of planned onsite observations and may participate if it so decides. Onsite

40 observation reports summarizing findings and results will be provided to the covered State.

41

42 NRC will provide a draft copy of the monitoring plans for the State's comment prior to finalizing

43 the plans. NRC will also share with the State any letters sent to DOE indicating possible

44 compliance concerns. The staff expects to meet periodically with DOE and the covered State

45 throughout the early stages of monitoring to ascertain the need for changes to the NRC's

46 compliance monitoring plan. These meetings will provide opportunities to discuss the status of

47 NRC monitoring activities and identify potential problems. Further, these meetings will provide

48 opportunities to discuss specific monitoring activities (e.g., onsite observations) planned for the

49

10-6
1

2

3 Figure 10-1. Schematic of NRC's Compliance Monitoring Approach

4

10-7
2

2

<~t~ ~t~yCopy ofreport is

assessment indicateý NR~ouet t rvddt h 1Sfindings&% in scýed §tate an d'

pefrane 'ý-Ys0perioolo monitoring -Zls rnaidlpubll'c.~

Met? 6conffnue

No

3 Figure 10-1 (continued). Schematic of NRC's Compliance Monitoring Approach

10-8
1 upcoming year, and allow the State to identify how it may want to participate in the

2 planned activities.

3

4 10.3 Compliance Monitoring Activities

5

6 The objective of NRC's monitoring is to assess whether DOE's disposal actions are in

7 compliance with the performance objectives in 10 CFR Part 61, Subpart C. Subpart C contains

8 a general requirement (10 CFR 61.40), requirements for protection of the general population

9 from releases of radioactivity (10 CFR 61.41), protection of individuals from inadvertent intrusion

10 (10 CFR 61.42), protection of individuals during operations (10 CFR 61.43), and stability of the

11 disposal site after closure (10 CFR 61.44). NRC staff will focus monitoring activities on those

12 waste disposal aspects that may affect whether the performance objectives can be met at the

13 present time and in the future.

14

15 The status of technical review and onsite observation activities is expected to fall into one of

16 three categories: (1) closed, (2) open, or (3) open-noncompliant. Staff will only monitor

17 activities that are categorized as open or open-noncompliant. The distinction between the last

18 two categories is made primarily to distinguish between monitoring activities that are merely

19 ongoing and monitoring activities that are ongoing and about which NRC has issued a

20 notification letter of noncompliance. A simplified example follows: if NRC staff reviewed data

21 used to support DOE's assumption(s) regarding the creation of reducing conditions in the

22 wasteform (due to the addition of ground blast furnace slag to-the grout), and NRC staff

23 concluded that DOE's assumption could no longer be supported, then, after a noncompliance

24 notification letter had been sent, this monitoring activity would be given the status of

25 open-noncompliant pending further review and discussion with DOE. Alternatively, DOE could

26 demonstrate reducing conditions in the grouted wasteform are no longer necessary for

27 demonstrating compliance with the performance objectives such that NRC could conclude with

28 reasonable assurance that the disposal facility will meet the performance objective(s) and that

29 the monitoring activity status is open while disposal action is ongoing.

30

31 In the periodic compliance monitoring report, the technical review activities and the onsite

32 observation activities will be given a status of either closed, open, or open-noncompliant.

33 This is the tracking mechanism that allows NRC staff to quickly see which activities have been.

34 concluded and which activities need special attention. Each monitoring activity, whether

35 technical review or onsite observation, is associated with a disposal action and should be so

36 identified in the relevant compliance monitoring plan. The active phase of the disposal actions

37 occurs during the time of operations that NRC defines as the time during which DOE carries out

38 its waste disposal actions, through the end of the institutional control period. Waste disposal

39 actions are considered to include performance assessment revisions, waste removal, grouting,

40 stabilization, observation, maintenance, or other similar activities. A technical review activity

41 that requires NRC staff to review information on curing techniques for grout would be associated

42 with the disposal action of grouting, while an onsite observation activity that requires NRC staff

43 to observe the construction of an engineered surface cover would be associated with the

44 disposal action of stabilization. For example, assume the results of the technical review for

45 curing techniques could no longer support key aspects of grouting, and there was no

46 reasonable assurance that one or more of the performance objectives would be met. NRC

47 would send a noncompliance notification letter stating that the grouting disposal action is not in

48 compliance with the performance objectives of 10 CFR Part 61 even if the other monitoring

49 activities relating to grouting have a status other than noncompliant.

10-9
1 The NRC staff should accurately track the status of open or open-noncompliant activities in the

2 periodic compliance monitoring report (see Section 10.4.2). As DOE's performanrce

3 assessment is revised and updated, it is conceivable that new issues that NRC staff determines

4 are important to DOE's compliance demonstration will be identified and should be monitored.

5 Therefore, as NRC proceeds with its monitoring activities, it is anticipated that new monitoring

6 activities could be developed and that the list of monitoring activities could change as some

7 activities are closed and new activities are opened. A closed activity can be reopened if new

8 information becomes available.

9

10 If monitoring activities provide information that there is no longer reasonable assurance that the

11 performance objectives will be met, then that monitoring activity may be close to being

12 categorized as open-noncompliant. If NRC staff determines that DOE is not in compliance with

13 one or more performance objective(s), staff should document its findings so that this can be

14 conveyed to DOE. DOE should be afforded an opportunity to provide additional information,

15 analyses, and/or insights that could help the staff reach a final conclusion. If it is still

16 determined that there is no reasonable assurance that one or more performance objectives will

17 be met, NRC staff will categorize the monitoring activity as open-noncompliant and send out a

18 notification letter that DOE is not in compliance (see Section 10.4.3).

19

20 10.3.1 Technical Review Approach

21

22 This section of the guidance document describes the general approach that the staff will take in

23 its review of technical information such as data, studies, experiments, and analyses specifically

24 identified to be addressed during monitoring. NRC technical review activities will consist of two

25 primary activities: reviewing data related to DOE's waste disposal actions and reviewing DOE's

26 performance assessment. Along with reviewing DOE's performance assessment, NRC staff will

27 review studies and analyses that support the performance assessment. The level of detail of

28 the performance assessment review will depend on whether DOE revises its performance

29 assessment, the extent of these changes, and how these changes and their effects are

30 documented and referenced. Most of NRC monitoring activities related to technical reviews (as

31 opposed to onsite observations) will be designed to assist in assessing compliance with

32 10 CFR 61.41 and 61.42 because the compliance demonstration relies upon long-term

33 predictive analyses. Most NRC technical reviews will focus on addressing uncertainties in these

34 predictive analyses. In review of data, staff will need to ensure that there is reasonable

35 confidence in the quality of the data in terms of its traceability, reproducibility, and

36 representativeness. Thus, the staff may need to review the approach DOE used to ensure the

37 quality of its data.

38

39 Environmental data should be sampled frequently and periodically and subsequently evaluated

40 and compared to an established metric that can be used to identify potential concerns. The

41 charting approach recommended by the U.S. Environmental Protection Agency (EPA) for

42 determining the adequacy of cleanup at Superfund sites may be useful for deciding when the

43 environmental data indicates a potential problem (EPA, 1989). Under the EPA charting

44 approach, the data for each sampling location would be charted as a function of time. A

45 potential concern would be indicated when either a specific number of consecutive samples

46 exceed the long-term average (or predisposal average) or there are a specific number of

47 consecutive increases in samples. This approach, used in the way control charts detect

48 significant deviations in an industrial process, is easy to use and should provide a fairly reliable

49 means of discerning an early indication of potential problems. In applying control charts for

50 industrial processes, eight consecutive numbers are generally used to indicate a change in the

10-10
1 process. This results in a very low probability of incorrectly concluding that there is a change in

2 the process (0.8 percent), assuming the data are independent. For environmental data, this

3 level of precision is not needed; therefore, it is generally recommended to use five to seven

4 consecutive points to indicate of a change in the system (EPA, 1989). Because the intent is

5 only to provide an early indication of potential concerns, an even lower precision is warranted;

6 therefore, it is. recommended that the staff use 3 to 4 consecutive points to indicate potential

7 concerns. Figure 10-2 provides an example of a control chart. In this example, four

8 consecutive data points are above the predisposal average and thus would be interpreted as an

9 early indication of a potential problem. Note that in the example, the contaminant concentration

10 levels are below the concentration that would give a dose of 25 mrem/year. However, because

11 four consecutive points are above the long-term average, this should be interpreted as a

12 change in the system that warrants further evaluation.

13

14 Key aspects identified within the TER for the waste determination will need to be assessed

15 through the review of data, studies, experiments, and/or analyses carried out by DOE. Staff

16 should review available studies and reports to see whether conclusions DOE reached continue

17 to be supported. In reviewing results from experiments, the staff should consider whether or not

18 appropriate approaches were used, and the results can be extrapolated to a larger scale and/or

19 over a longer time period. In reviewing DOE analyses, especially DOE's performance

20 assessment, the staff should ensure that sufficient data continues to support assumptions within

21 the analyses and that the appropriate range of data to account for variability, the appropriate

22 consideration of model uncertainty, and the adequacy of the model support is still valid.

23 Modeling results should have either adequate model support or appropriate conservative

24 assumptions or parameter values. In general, the results from one model should not be used as

25 the sole support for another model. The amount of support that is provided for models that form

26 the basis for conclusions is a key issue. In reviewing DOE analyses, the staff should consider

29

Concentration = dose limit

0 0

'C 0

E0 0

(:)

0 Predtsposal Average

0

Time

30 Figure 10-2. A Control Chart Example

10-11
1 individual analyses in the context of the overall performance demonstration (i.e., how well the

2 analyses comport with other analyses and the significance of the results from an individual

3 analysis in the context of the overall performance demonstration). To the extent practical, staff

4 should perform its own independent analyses to substantiate results from DOE's analysis and to

5 understand the important aspects of the analysis.

6

7 As staff completes its technical review and depending on the type of monitoring activity,

8 compliance monitoring activities may be discontinued and given a status of closed following the

9 approach described in the specific compliance monitoring plans. Any activity that is closed will

10 be documented as such in the periodic compliance monitoring report (see Section 10.4.2).

11

12 10.3.2 Onsite Observation Approach

13

14 As previously mentioned, there are generally two primary approaches staff uses to assess

15 compliance with the performance objectives in 10 CFR Part 61, Subpart C: technical reviews

16 and onsite visits or observations. In coordination with the covered State, NRC staff will, at

17 appropriate times, go to the site to observe and review certain operations as they are being

18 performed. NRC onsite observations may include activities such as (1) observation and review

19 of data collection activities, (2) observation of grout preparation and pouring, (3) review of

20. radiation records and associated program elements, and (4) observation of construction of

21 engineered features and their maintenance. Onsite observations should be conducted using a

22 performance-based approach. Observations should focus on direct observation of work

23 activities, interviews with workers, demonstrations of tasks, visual review of the construction of

24 facilities, and where appropriate, a review of selected records. A direct examination of these

25 activities and discussions with cognizant workers will help provide important insights and is

26 preferable to a review of selected records alone. NRC staff must be prepared to meet all

27 DOE-established entry requirements. This includes, but may not be limited to, use of personal

28 protective equipment, viewing of a site-specific safety video, or meeting any special

29 requirements for entering certain environments.

30

31 The frequency of periodic observations of DOE's waste disposal activities may be dependent on

32 DOE plans and should be selected based on the stage of waste disposal. DOE's radiation

33 protection program is expected to be sufficiently mature and is expected to have had

34 demonstrated adequate protection. Therefore, these observations involving protection of

35 individuals during operations will focus primarily on confirming that DOE radiation protection

36 plans for the specific waste disposal activities are consistent with the overall radiation protection

37 program cited in the waste determination as the basis for demonstrating compliance with the

38 10 CFR 61.43 performance objective. After the NRC staff has gained an understanding of the

39 scope of the radiation protection program, future assessments may be greatly scaled back and

40 focus primarily on program changes.

41

42 10.4 Documentation of Findings and Reporting

43

44 10.4.1 Onsite Observation Reports

45

46 NRC staff participating in onsite observations will be required to develop a report after each site

47 visit. This report will provide a written summary of what was done on the site visit and list any

48 results obtained through the activities performed at the site. The report is expected to include a

49 list of the participants, a description of the activities undertaken, and staff assessment of

10-12
1 materials evaluated or direct observations. This report will also describe which onsite

2 observation activities identified in the compliance monitoring plan were carried out during the

3 onsite observation. In addition, the report should clearly indicate which activities remain open

4 and are to be continued in the future and which have been satisfactorily completed and given

5 the status of closed. The report of the onsite monitoring results will be provided to DOE and

6 covered State by letter within 60 days following the site visit.

7

8 10.4.2 Periodic Compliance Monitoring Reports

9

10 Staff will periodically document its findings for the various technical reviews and onsite

11 observations completed in a monitoring report.1 In addition to the onsite observation findings

12 made during the year, the periodic report will also document the staff s technical reviews of

13 data, its review of reports or analyses to address key aspects, and its review of any updates or

14 revisions to DOE's performance assessment.

15

16 In documenting its review, the staff will describe what was reviewed, its findings on whether

17 there are indications that there is no longer reasonable assurance that the performance

18 objectives will be met for the entire performance period (this will include a description of

19 the specific performance objectives that apply), and the basis for the staff findings

20 (e.g., independent analyses conducted by the staff, supporting studies, expert opinion). In

21 addition, the staff should describe any recommended action that should be undertaken to close

22 open activities.

23

24 The periodic compliance monitoring report should also serve as a vehicle for tracking the status

25 of the monitoring activities in terms of whether the activity is considered closed, open, or

26 open-noncompliant. For any activity that was previously closed but is being reopened, the staff

27 should describe its basis for reopening the activity and its expected plans for monitoring the

28 activity. The periodic compliance monitoring report should also describe any new monitoring

29 activities identified during the year and the basis for opening the new activity. For open and

30 open-noncompliant activities, the staff should also identify any activities that are expected to be

31 carried out for the upcoming year. For activities that have been closed, the staff should

32 document its basis for closing the review and any conditions that could prompt its reopening.

33 For noncompliant activities, the periodic compliance monitoring report should document any

34 actions or results that might change the status. In addition to giving the status of each

35 monitoring activity, the periodic compliance monitoring report should identify which disposal

36 action each monitoring activity is associated with, as previously documented in the compliance

37 monitoring plan (see Section 10.3).

38

39 It is envisioned that staff will meet with DOE and the State on an periodic 2 basis to discuss the

40 status of the monitoring program. The staff may use this meeting to help identify potential

41 revisions to the monitoring program.3 NRC will take the lead in setting up such a meeting,

'It is anticipated that during the early phases of carrying out its monitoring activities, the NRC will develop an annual

report.. However, as the monitoring program progresses and the number of monitoring activities diminish, the staff will

need to reassess whether less frequent reporting is warranted.

2The frequency of these meetings is expected to change as implementation of the NRC monitoring program

progresses. As the number of monitoring activities diminish, NRC staff will reevaluate the meeting frequency.

3

This could also include determining the need for less frequent reporting and meetings.

10-13
1 including developing the agenda and making the meeting notices (these meetings are expected

2 to be open to the public). Given that there may be some public interest in such meetings, some

3 of the meetings may be held in the vicinity of the site; therefore, the NRC staff may need to work

4 with DOE and/or the State in securing an appropriate meeting facility. Staff should describe

5 conclusions and followup actions that come out of this meeting in the periodic compliance

6 monitoring report.

7

8 The monitoring report should describe any developing issues or potential problems that should

9 be brought to the attention of management. For example, the staff may have identified issues

10 through either its technical review or onsite observations that are not significant enough to

11 indicate that there is no longer reasonable assurance that the performance objectives will be

12 met, but issues that could potentially affect the performance demonstration may be present.

13 Such issues will be discussed through normal correspondence for issues associated with

14 technical reviews, and through exit meetings and onsite observation reports for issues identified

15 during onsite observations. In addition, developing issues or potential problems identified

16 through technical reviews or onsite observations will be included in the annual monitoring

17 reports. The disposition of any issues raised during the previous year should also be described

18 in the report.

19

20 Figure 10-3 shows the topical areas that are likely to be covered in the periodic compliance

21 monitoring report. A copy of the report will be provided to DOE and the State for information

22 purposes. In addition, the report will be made publicly available on NRC's website.

23

24 10.4.3 Noncompliance Notification Letters

25

26 In accordance with the NDAA, NRC is required to inform DOE, the covered State, and Congress

27 if it considers any of DOE's waste disposal actions to be noncompliant with the performance

28 objectives of 10 CFR Part 61, Subpart C. The specific congressional committees that NRC is

29 required to inform are the Committee on Armed Services, Energy and Commerce, and

30 Appropriations in the House of Representatives, and the Committee on Armed Services, Energy

31 and Natural Resources, Environment and Public Works, and Appropriations in the Senate. In

32 addition, the noncompliance notification letter will be made publicly available on NRC's website.

33 NRC is required to make this notification as soon as practicable after discovery of

34 noncompliant conditions.

35

36 As NRC staff carries out its monitoring activities as outlined in the compliance monitoring plan,

37 preliminary assessments will indicate whether DOE's disposal actions are considered to be in

38 compliance with the performance objectives. There are three primary reasons that DOE

39 disposal actions could be found noncompliant: (1) if there are sufficient indications that the

40 requirements of 10 CFR 61.41 through 44 are currently not being met, (2) if there are sufficient

41 indications that there is no longer reasonable assurance that the performance objectives will be

42 met in the future, or (3) if key aspects relied upon to demonstrate compliance with one or more

43 performance objectives are no longer supported due to the lack of supporting information

44 obtained during the monitoring period.

45

46 With respect to the first primary reason, possible indications that the requirements of

47 10 CFR 61.41 through 44 are currently not being met would be environmental concentrations at

48 locations where individuals could be exposed that would give a dose exceeding the dose criteria

49 set by the performance objective(s). Other possible indications that the performance objectives

10-14
Topical Areas

Onsite Observations

* Areas reviewed

0 Preliminary assessments

* Basis for preliminary assessments

* Recommended actions

Technical Reviews . Areas reviewed

* Preliminary assessments

0 Basis for preliminary assessments

0 Recommended actions

New and Reopened Activities

" Area of concern

" Significance to performance demonstration

• Expected monitoring activities

Open-Noncompliant Activities

" Basis for status

" Actions or results that might change the status

Table Matching Each Monitoring Activity with Disposal Action

Summary of Periodic Meeting

Revisions to the Disposal System Designs and the Compliance Monitoring Plans

Potential Problems

Activities Closed

Figure 10-3. Topical Areas Expected in the Periodic Compliance

Monitoring Report

1 are currently being exceeded would be radiation doses to workers or members of the public that

2 exceed the dose limit.

3 With respect to the second reason, NRC staff note that 10 CFR 61.40 is not met as soon as

4 there is no longer reasonable assurance that the requirements of 10 CFR 61.41-61.44 will not

5 be met at any time during the performance period. Given the nature of the highly engineered

6 facilities involved, evidence of problems with meeting the performance objectives may not be

7 observable for hundreds of years in the future. Thus, solely relying upon observable failure of

8 the system may not allow the NRC to make a timely notification as required by the NDAA. In

9 addition, assessing compliance for some performance objectives (e.g., 10 CFR 61.42) is difficult

10 to accomplish through direct observation. Thus, the second means by which NRC may make a

10-15
1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

finding of noncompliance is through predictive modeling that indicates that there is no longer

reasonable assurance that the performance objectives will be met for the entire performance

period. For example, predicted or expected technical information on a key assumption was

replaced with conflicting new information. Key in this sense means that without the assumption,

demonstrating compliance with the performance objectives may not be possible. Another

indication would be if trends in the data indicate that at some future time the performance

objectives criteria would be exceeded.

The third way in which the performance objectives may not be met is when key aspects relied

upon to demonstrate compliance with one or more performance objectives are no longer

supported due to the lack of supporting information obtained during the monitoring period (see

Section 10.1).

Given the different types of noncompliance, NRC anticipates using several different types of

notification letters. These letters are listed in Table 10-2. A Type I letter would state that there

are sufficient indications that the requirements of 10 CFR 61.41 through 44 are currently not

being met. Within the letter, NRC would document the basis for the indications that the

performance objectives are currently not being met and describe the performance objectives. A

Type II letter would document the basis for the indication that there is no longer reasonable

assurance that the performance objectives will be met for the entire performance period and

Table 10-2. Types of Notification Letters

Type Notification Signature Distribution

I Noncompliance Chairman DOE, covered State,

Indication that the requirements of 10 and Congress

CFR 61.41 through 44 are currently

not being met

if Noncompliance Chairman DOE, covered State,

Indication that there is no longer and Congress

reasonable assurance that the

performance objective(s) will be met in

the future

III Noncompliance Chairman DOE, covered State,

Lack of supporting information: and Congress

Key aspects relied upon to

demonstrate compliance with the

performance objective(s) are no longer

supported

IV Concern NRC Staff DOE and covered

Concerns with the performance Management State

demonstration

V Resolution NRC Staff DOE and covered

Resolution of concerns with the Management State

performance demonstration

10-16
1 would describe the specific performance objectives that may not be met. A Type III letter would

2 document the lack of supporting information during the compliance monitoring period. This

3 letter would include the basis for such a conclusion and describe the performance objective(s)

4 lacking supporting information. Because of their significance and distribution, Type I-Ill letters

5 would be sent out under the signature of the NRC Chairman. While each of the three types of

6 notification letters is important, the Type I letter is the most serious because it pertains to an

7 immediate potential threat to public health and safety.

8

9 Prior to sending out Type I-Ill letters, NRC will review its concerns in a letter (Type IV) to DOE

10 and the State. This will give the State an opportunity to provide input and comment and provide

11 DOE with an opportunity to provide information that demonstrates its disposal actions are in

12 compliance with the performance objectives. Assuming that DOE provides information to

13 support its performance demonstration, NRC will review this information and decide whether it is

14 sufficient to conclude that there is reasonable assurance that the performance objectives will be

15 met. If the staff determines that, based on the information DOE provided, there is sufficient

16 basis to conclude that DOE is in compliance, NRC will send out a notification of resolution letter

17 (Type V). Type IV and V letters will be made publicly available on NRC's website. These letters

18 formally document resolution of the issue. If the staff determines that, based on the information

19 DOE provides, there is still a basis for concluding that DOE is noncompliant, NRC will send out

20 the noncompliance notification letter (i.e., Type I-Ill).

21

22 Because NRC does not have regulatory or enforcement authority over DOE, it is the role of

23 Congress, the covered State, and DOE to determine what, if any, actions will be taken in

24 response to a noncompliance notification letter. The noncompliance notification letter will

25 emphasize that the status of the disposal action may change to something other than

26 noncompliant depending on the type of information NRC receives in the future. Any subsequent

27 change in the status of the disposal action from noncompliant will be documented in the periodic

28 compliance monitoring report, which will be publicly available. NRC staff will continue to monitor

29 DOE's disposal actions after issuance of the noncompliance notification letter.

30

31 10.5 References

32

33 U.S. Environmental Protection Agency (EPA). "Statistical Analysis of Ground-Water Monitoring

34 Data at RCRA Facilities, Interim Final Guidance." Office of Solid Waste, U.S. Environmental

35 Protection Agency. Washington, DC. February 1989.

36

37 . "Decommissioning Criteria for the West Valley Demonstration Project at the West Valley

38 Site: Final Policy Statement." Federal Register, 67 FR 5003. February 2002.

39

40 U.S. Nuclear Regulatory Commission (NRC). "Implementation of New U.S. Regulatory

41 Commission Responsibility under the National Defense Authorization Act of 2005 in Reviewing

42 Waste Determinations for the U.S. Department of Energy." SECY-05-0073. April 28, 2005.

43

44

45

10-17

APPENDIX A

SECTION 3116

OF THE RONALD W. REAGAN NATIONAL DEFENSE AUTHORIZATION ACT

FOR FISCAL YEAR 2005

SEC. 3116. DEFENSE SITE ACCELERATION COMPLETION.

(a) IN GENERAL- Notwithstanding the provisions of the Nuclear Waste Policy Act of 1982,

the requirements of section 202 of the Energy Reorganization Act of 1974, and other laws

that define classes of radioactive waste, with respect to material stored at a Department of

Energy site at which activities are regulated by a covered State pursuant to approved

closure plans or permits issued by the State, the term "high-level radioactive waste" does

not include radioactive waste resulting from the reprocessing of spent nuclear fuel that the

Secretary of Energy (in this section referred to as the "Secretary"), in consultation with the

Nuclear Regulatory.Commission (in this section referred to as the "Commission"),

determines-

(1) does not require permanent isolation in a deep geologic repository for spent fuel

or high-level radioactive waste;

(2) has had highly radioactive radionuclides removed to the maximum extent

practical; and

(3)(A) does not exceed concentration limits for Class C low-level waste as set out in

section 61.55 of title 10, Code of Federal Regulations, and will be disposed of-:-

(i) in compliance with the performance objectives set out in subpart C of part

61 of title 10, Code of Federal Regulations; and

(ii) pursuant to a State-approved closure plan or State-issued permit,

authority for the approval or issuance of which is conferred on-the State

outside of this section; or

(B) exceeds concentration limits for Class C low-level waste as set out in section

61.55 of title 10, Code of Federal Regulations, but will be disposed of-

(i) in compliance with the performance objectives set out in subpart C of part

61 of title 10, Code of Federal Regulations;

(ii) pursuant to a State-approved closure plan or State-issued permit,

authority for the approval or issuance of which is conferred on the State

outside of this section; and

(iii) pursuant to plans developed by the Secretary in consultation with

the Commission.

(b) MONITORING BY NUCLEAR REGULATORY COMMISSION- (1) The Commission shall,

in coordination with the covered State, monitor disposal actions taken by the Department of

Energy pursuant to subparagraphs (A) and (B) of subsection (a)(3) for the purpose of

assessing compliance with the performance objectives set out in subpart C of part 61 of title

10, Code of Federal Regulations.

(2) If the Commission considers any disposal actions taken by the Department of Energy

pursuant to those subparagraphs to be not in compliance with those performance

objectives, the Commission shall, as soon as practicable after discovery of the noncompliant

A-1
conditions, inform the Department of Energy, the covered State, and the following

congressional committees:

(A) The Committee on Armed Services, the Committee on Energy and Commerce,

and the Committee on Appropriations of the House of Representatives.

(B) The Committee on Armed Services, the Committee on Energy and Natural

Resources, the Committee on Environment and Public Works, and the Committee on

Appropriations of the Senate.

(3) For fiscal year 2005, the Secretary shall, from amounts available for defense site

acceleration completion, reimburse the Commission for all expenses, including salaries, that

the, Commission incurs as a result of performance under subsection (a) and this subsection

for fiscal year 2005. The Department of Energy and the Commission may enter into an

interagency agreement that specifies the method of reimbursement. Amounts received by

the Commission for performance under subsection (a) and this subsection may be retained

and used for salaries and expenses associated with those activities, notwithstanding section

3302 of title 31, United States Code, and shall remain available until expended.

(4) For fiscal years after 2005, the Commission shall include in the budget justification

materials submitted to Congress in support of the Commission budget for that fiscal year (as

submitted with the budget of the President under section 1105(a) of title 31, United States

Code) the amounts required, not offset by revenues, for performance under subsection (a)

and this subsection.

(c) INAPPLICABILITY TO CERTAIN MATERIALS- Subsection (a) shall not apply to any

material otherwise covered by that subsection that is transported from the covered State.

(d) COVERED STATES- For purposes of this section, the following States are

covered States:

(1) The State of South Carolina.

(2) The State of Idaho.

(e) CONSTRUCTION- (1) Nothing in this section shall impair, alter, or modify the full

implementation of any Federal Facility Agreement and Consent Order or other applicable

consent decree for a Department of Energy site.

(2) Nothing in this section establishes any precedent or is binding on the State of

Washington, the State of Oregon, or any other State not covered by subsection (d) for the

management, storage, treatment, and disposition of radioactive and hazardous materials.

(3) Nothing in this section amends the definition of "transuranic waste" or regulations for

repository disposal of transuranic waste pursuant to the Waste Isolation Pilot Plant Land

Withdrawal Act or part 191 of title 40, Code of Federal Regulations.

(4) Nothing in this section shall be construed to affect in any way the obligations of the

Department of Energy to comply with section 4306A of the Atomic Energy Defense Act (50

U.S.C. 2567).

(5) Nothing in this section amends the West Valley Demonstration Act (42 U.S.C. 2121a

note).

(f) JUDICIAL REVIEW- Judicial review shall be available in accordance with chapter 7 of

title 5, United States Code, for the following:

(1) Any determination made by the Secretary or any other agency action taken by

the Secretary pursuant to this section.

A-2
(2) Any failure of the Commission to carry out its responsibilities under

subsection (b).

A-3

APPENDIX B

CALCULATION TO DEVELOP BENCHMARK AVERAGING EXPRESSIONS

This section describes the calculations used to develop the benchmark expressions for

Category 3 concentration averaging. The primary purpose of the example averaging

expressions is to provide a benchmark for the staff to use when reviewing site-specific

averaging for waste classification. The benchmark provides a comparison point for what can be

complex calculations involving numerous uncertain parameters and assumptions. This

appendix is not intended to provide a full description of an internal staff review tool. A full

description may be developed at a later date if warranted and if sufficient resources are

available.

B.1 Development of Example Averaging Expressions

A description of the calculations used to develop the example averaging expressions for

Category 3 are provided in this section. Conceptually, the approach is based on the

following equation

C=j *Vi *Xijj Dij (B-1)

where

i= the analysis index (set to either 61 or N)

S= the radionuclide index

C.i = the concentration of radionuclide j for analysis i

V= the volume of waste exhumed for analysis i

Xj= a conversion factor for analysis i and radionuclide j to convert a source

into an intruder dose

Dij = the resultant dose to the intruder for analysis i from radionuclide j

The analysis index is either the Part 61 waste classification analysis (61) or the new analysis for

incidental waste (N). Equation (B-i) can be written for both the old Part 61 waste classification

analysis and the new analysis for incidental waste, and the two equations can be combined as

Eq. (B-2)

CNj * VN K XNJ D N.j

C 61,j V61 X 61,j D 61,j

The conversion factor X.j essentially represents the dose analysis to convert a quantity and

distribution of radionuclide j into dose for analysis i. Many variables go into the conversion

factor X.j1 , including but not limited to dosimetry, parameters, uncertainty treatment, and

assumptions. The ratio of XNJ to X-I.j in equation B-2 would look something like

X.J DosimetrYNj ParametersN.j 1'*/UncertaintyN"" Assumptions" N.

X61,j Dosimet. 6 ,* Parameters)6,) Uncertaity 6 tj Assumpions 6 j (B-3)

B-1
Although the Part 61 analysis could be duplicated to define the variables influencing X)61,, the

effort required would be substantial. A simpler but valid approach was used to develop the

example averaging expressions for staff to use as a review tool. If it can be assumed for the

Part 61 analysis that waste at the Class C limit for each radionuclide j multiplied by a conversion

factor X] resulted in a dose of 5 mSv [500 mrem] for the excavation intruder, then all of the

variables except a new constant [1N 61 * XN,/X61j] can be fixed in Eq. (B-2) without knowing the

exact contribution of each of the terms in (B-3). Equation (B-2) can be solved for the term

[1N 61 * XN,j/X 61,j] to yield the constants used in the example averaging expressions provided in

Section 3.5.1.1. To apply the analysis to a drilling scenario as opposed to an excavation

scenario simply requires defining VN with respect to the primary variables affecting drilled

waste volume.

The steps to complete the calculations were as follows:

(1) Assume the Class C concentration values provided in Tables 1 and 2 of 10 CFR 61.55

would result in a 5 mSv [500 mrem] dose from each radionuclide for a typical

commercial low-level waste disposal facility and the excavation intruder scenario using

ICRP-2 dosimetry (for internal exposures, external exposures were also considered),

the assumptions, and the scenario parameters for the dose assessment of a commercial

low-level waste facility.

(2) Use unit concentrations of each radionuclide (concentrations are either volume based or

mass based consistent with Tables 1 and 2 of 10 CFR 61.55) as input and calculate the

mean dose impact using ICRP 26 and 30 dosimetry with probabilistic calculations for

each of the four scenarios described in Section 3.5.1.1 (shallow waste with no intruder

barrier, shallow waste with an intruder barrier, deep waste with no intruder barrier, deep

waste with an intruder barrier). For the four scenarios, the conditions for the calculation

are shown in Table 3-1.

(3) Calculate a Part 61 dose concentration ratio defined as the inadvertent intruder dose

limit {5 mSv [500 mrem]} divided by the Table 1 and 2 Class C concentration value. This

ratio provides impact per unit concentration resulting from the parameters, assumed

dilution, and dosimetry approach for the Part 61 analysis.

(4) For each radionuclide for two receptor types (acute and chronic), two disruption

processes (drilling and excavation), and two waste access times (100 years and

500 years), calculate a new dose concentration ratio defined as the mean dose result

for each radionuclide from the probabilistic calculations mentioned in Step (2) divided by

the unit concentrations used as input for those calculations. The mean dose result

should be selected in the year of peak dose following the intrusion event. For most

calculations, the peak occurs in the year of the intrusion event. This ratio provides the

impact per unit concentration for the parameters, assumed dilution, dosimetry, and

uncertainty in the new calculations. Choose the limiting value by receptor type (acute or

chronic) for each of the four scenarios (drilling at 100 years, drilling at 500 years,

excavation at 100 years, and excavation at 500 years).

(5) The new dose concentration ratio and the Part 61 concentration ratio are input into

Eq. B-2, and the equation is rearranged to solve for an appropriate constant (the new

dose concentration ratio is DN,/CN,j; the Part 61 concentration ratio is D 6 1 ,/C 6 1 ,j; VN is

known for the calculation).

B-2
(6) The scenario-specific classification expression is developed based on the constant

defined in Step (5) that is based on the primary variables of interest for the scenario

(e.g., waste volume or waste thickness and drilling depth). If drilling depth is fixed at a

site, then waste thickness would be the primary variable for a deep waste scenario. The

primary variables of interest were selected to be those variables that directly define the

amount of mixing for a scenario. Other variables could be selected, if necessary.

(a) For probabilistic calculations, the new dose concentration ratio is a matrix

of results by (radionuclide, scenario). Each element of the matrix is a

distribution of results.

(b) The classification expression is developed by taking the mean result for the

limiting long- and short-lived radionuclides (e.g., for the resident postdrilling

scenario at 500 years, the limiting long-lived radionuclide is Np-237). The

limiting long- and short-lived radionuclides were used to simplify the

expressions (i.e., to avoid developing a vector of constants by radionuclide

for the classification expressions).

(c) The classification expressions for deeper waste (drilling scenarios) were

developed using Equation B-2 with VN defined with appropriate drilling

scenario parameters (e.g., waste thickness).

The classification expressions provide the same protection per unit of material exhumed as the

concentration limits in Table 1 and 2 and the Part 61 analysis provides; that is, both are based

on an intruder dose of 5 mSv [500 mrem].

The radiological assessment method to develop the example averaging expressions calculated

total effective dose equivalent (TEDE) as the product of radionuclides concentrations in

environmental media and pathway dose conversion factors (PDCFs). The PDCFs were derived

similarly to the method of Kennedy and Strenge (1992) for converting residual contamination

into TEDE. The concentrations in environmental media were estimated by first calculating

mixing of a user-defined source for a given intruder scenario (e.g., intruder drilling chronic,

intruder construction acute), then applying simple mass transfer models to estimate radionuclide

concentrations in air, water, and soil to account for radionuclide decay including ingrowth of

daughters, sorption, solubilities, hydrologic transport, and other mass transfer and partitioning

processes. The pathways considered for the acute scenarios were inhalation, direct radiation,

and inadvertent soil ingestion. In addition to the acute pathways, consumption of plants and

animals were considered for the chronic pathways. Other pathways may need to be considered

in the site-specific analysis (e.g., dependent on site conditions, the drinking water pathway may

or may not be substantially delayed and the impacts smaller than the direct waste exposure

pathways). To develop the benchmark expressions, the animal consumption pathway was not a

dominant contributor for limiting short-lived (Cs-1 37) and long-lived (Np-237) radionuclides. In

addition, the scenario was defined as a resident but not a resident-farmer, thereby making the

animal pathway less credible. Therefore, the animal pathway was not implemented in the final

calculations. For the excavation chronic scenario, the resident was assumed to grow food

crops and was exposed through ingestion of the food crops. Plant/soil concentration ratios

were used to estimate the amount of radioactivity taken into the plant from a unit activity in the

soil. Four different plant parts were estimated separately: leafy, root, fruit, and grain.

Parameter uncertainty was explicitly considered in many of the inputs. Data used in the

analysis were consistent with previous assessments of Kennedy and Strenge (1992) and

B-3 *
regulatory products (e.g., RESRAD, D&D). The dynamic simulation software package

GoldSim® was used to perform the analysis.

Probabilistic analysis was used in the development of the example averaging expressions to

account for variability and uncertainty (e.g., uncertainty in soil-to-plant transfer factors). A

probabilistic assessment is preferred, but it is not required to develop site-specific (Category 3)

averaging expressions. Parameters that should be varied or evaluated with sensitivity analysis

are determined on a case-by-case basis. In the analysis used to develop the example

averaging expressions provided in Section 3.5.1.1, the new dose concentration ratio,

regardless of radionuclide, was sensitive to drilling scenario related parameters such as drilling

depth, waste thickness, garden area, and drill cuttings distribution area. The new dose

concentration ratio for excavation scenarios, regardless of radionuclide, was sensitive to the

excavation-related parameters such as waste volume in the excavation and excavation volume.

Parameters that directly define the concentration of waste in the environment after disruption

can confidently be assumed to be important. For this analysis, the short-lived radionuclides

were limited by Cs-137, and the long-lived radionuclides were limited by Np-237. Direct

radiation exposure and plant consumption were the primary pathways for Cs-1 37, with

inhalation and inadvertent soil ingestion secondary pathways. The doses from these pathways

are sensitive to exposure times, consumption rates, soil-to-plant transfer factors, dose

conversion factors, and transmission factors. For Np-237, the plant pathway and external

radiation exposure were the primary pathways, with inhalation and inadvertent soil ingestion

providing less than 10 percent of the total dose. Sensitive parameters were similar to those for

Cs-137.

References

ICRP. "Report of ICRP Committee II on Permissible Dose for Internal Radiation." International

Commission on Radiological Protection. 1959.

U.S. Nuclear Regulatory Commission (NRC). "Residual Radioactive Contamination From

Decommissioning." NUREG/CR-5512. October 1992.

B-4
APPENDIX C

PUBLIC COMMENTS, ADVISORY COMMITTEE ON NUCLEAR WASTE COMMENTS

AND RESPONSES

NUREG-1 854, "Standard Review Plan for Activities Related to U.S. Department of Energy

Waste Determinations," was published for interim use and comment in May 2006. NRC

received public comments on the document, and they were accepted until July 31, 2006. NRC

received 12 comment letters during the public comment period, which are addressed in this

appendix. Comments were received from four State agencies, two public interest groups, and

five individuals. In addition to the public comments, the staff also received comments and

recommendations from the NRC Advisory Committee on Nuclear Waste (ACNW). The ACNW

comments and recommendations are also addressed in this appendix.

NRC staff reviewed each of the comments received. Some of the comments were very similar

to other comments. Similar comments were grouped and were given a single response.

Several comments were outside the scope of NUREG-1854.

Public Comments

COMMENT: One commenter suggested that the guidance document should address climate

change induced by increased carbon emissions.

RESPONSE: The review guidance directs NRC staff to consider the impact of short-duration,

large magnitude events. Emphasis has been added in Sections 4.3.1 and 7.1.1.2 for those

cases where fluvial erosion, flooding, slope failure, or landsliding may be significant. For most

deeply buried waste systems, the impact of human-induced climate change is mainly expected

to affect the timing of the change in climatic conditions at the waste but not the magnitude of the

conditions, due to the damping function of the overlying geologic system. Temperatures and

precipitation could increase or decrease depending on the particular site (e.g., local climates

can be affected opposite to the global climatic trend). For wetter conditions, increasing

infiltration rates using higher moisture contents and providing shallower water tables (at times

earlier than would be estimated by consideration of the natural cycling of climate) would be an

appropriate mechanism to test the sensitivity of the assessment potential doses or site stability

to human-induced climate change. As the commenter noted, the main exception may be for a

waste disposal system expected to be affected by surface geologic processes such as fluvial

erosion, slope failure, or landsliding. Assessment of long-term surface geologic processes has

many uncertainties, only one of which is the effect of climate change. If the assessment

identifies a large sensitivity of system performance to uncertainty in the effects of climate

change, bounding assumptions or the use of designs that mitigate the impacts should be

evaluated. Guidance Sections 1.1.3.3, 4.3.1,7.1, and 7.2 have been revised to address

uncertainties in climate projections.

Predictive abilities for future climates continue to evolve. NRC staff involved in waste

determination reviews will continue to remain abreast of developments regarding climate

change, incorporating new information as appropriate.

COMMENT: One commenter suggested that NRC should reference the 2000 waste

determination review for the Savannah River Site in Section 1.3 of the guidance document.

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RESPONSE: The two prior waste determination reviews listed in Section 1.3 of the guidance

document were included only as examples. There was no intent to provide an exhaustive list of

prior waste determination reviews.

COMMENT: One commenter suggested that DOE's draft waste determination, its supporting

technical basis documents, and any relevant NRC-generated documents should be made

publicly available on NRC's website at the earliest possible time. The commenter also

recommended that relevant documents should be made available prior to a draft comment

period for any Technical Evaluation Report (TER) NRC staff generates to document its review of

a waste determination.

RESPONSE: As described in Section 9.4 of the draft guidance, NRC staff will make relevant

documents generated by NRC or submitted by DOE available on its website, with the possible

exception of documents withheld because of security concerns. In practice, NRC staff

publishes externally generated public documents to its Agencywide Documents Access and

Management System (ADAMS) as soon as practical after it receives them. NRC staff typically

publishes NRC-generated public documents to ADAMS'within five days. NRC does not intend

to publish draft versions of its TERs for public comment. Although the TER is not published for

public comment, NRC does make its request for additional information public and conducts

public meetings on specific waste determinations to assure the staff's review process is as

transparent as possible. No changes have been made to the guidance in response to

this comment.

COMMENT: One commenter agreed with the NRC that prior waste determinations should be

reviewed and appropriately considered when reviewing DOE waste determinations at hand.

The commenter also suggested that NRC analyze DOE waste determinations against National

Academy of Sciences (NAS) recommendations. Furthermore, the commenter suggested that if

a DOE waste determination was found not to be in full compliance with NAS recommendations,

then the NRC "should not recommend going forward with the waste determination."

RESPONSE: The NRC Staff disagrees with the commenter's suggestion that the NRC should

formally evaluate DOE waste determinations against the NAS recommendations. The staff

believes that the NAS study (National Academy of Sciences, 2006) provides valuable

recommendations, perspectives, and insights, but that it does not establish a set of criteria that

must be met. NRC staff will continue to remain abreast of relevant NAS studies and the

associated valuable insights.

COMMENT: Two commenters made suggestions on a number of aspects related to the

dosimetry used in the performance assessment.

RESPONSE: The guidance document advocates the use of dosimetry consistent with

10 CFR Part 20. This ensures that compliance calculations for 10 CFR 61.41 and

10 CFR 61.43 remain consistent, as is discussed in NUREG-1 573, "A Performance

Assessment Methodology for Low-Level Radioactive Waste Disposal Facilities."

The proposed rule for 10 CFR Part 63, "Disposal of High-Level Radioactive Wastes in a

Proposed Geological Repository at Yucca Mountain, Nevada; Proposed Rule," states

"As a matter of policy, NRC considers 0.25 mSv [25 mrem] Total Effective Dose

Equivalent (TEDE) as the appropriate dose limit within the range of potential

C-2
doses represented by the current 10 CFR 72.104 limit of 0.25 mSv [25 mrem]

(whole body), 0.75 mSv [75 mrem] (thyroid dose), and 0.25 mSv [25 mrem] (to

any other critical organ)." (64 FR 8644)

As 10 CFR 61.41 has the same standard as 10 CFR 72.104, this policy is applicable, and

therefore, waste determinations will use TEDE without specifically considering individual organ

doses. In addition, the guidance specifies that intruder calculations should also be based on

5 mSv [500 mrem] TEDE calculations without specifically considering individual organ doses, to

be consistent with the dosimetry used for 10 CFR 61.41 and 10 CFR 61.43. Because of the

tissue weighting factors and the magnitude of the TEDE limit, specific organ dose limits are not

necessary to protect from deterministic effects.

Currently, NRC has a policy of allowing licensees to use these systems on a case-by-case basis

if they request. While not identical, NRC would equate 0.25 mSv [25 mrem] effective dose the

same as 0.25 mSv [25 mrem] total effective dose equivalent. In NUREG-1757, Volume 2,

Appendix 1.5.3.2, NRC addresses the issue for long-term performance assessment within the

scope of decommissioning. The guidance states

"Licensees may request an exemption from Part 20 to use the latest dose

conversion factors (e.g., International Commission on Radiation Protection

[ICRP] Report 72). Scenarios and critical group assumptions should be revisited

to look at age-based considerations. Licensees may not 'pick and choose'

dosimetry methods for radionuclides (e.g., Federal Guidance Report No. 11 for

six radionuclides and current International dose conversion factors for

three radionuclides)."

DOE is not a licensee and would not require an exemption to use the alternate dosimetry.

However, the guidance for WIR would be consistent with the guidance for decommissioning in

that DOE should use the alternate dosimetry for all parts of the analysis (10 CFR 61.41, 61.43,

and intruder analyses) and for all radionuclides. An exception may be for direct exposures,

which were not updated for ICRP-72 and therefore would need to use the FGR-13 values.

Additionally, staff would consider whether age-specific scenarios or exposure groups could

result in higher doses.

COMMENT: One commenter expressed concern with the term "as DOE may authorize" in

Section 2.4.4 as it related to waste that exceeds Class C concentration limits. The commenter

suggested that this phrase might be construed to mean that DOE may call anything incidental

waste and handle it any way that it "deems proper."

RESPONSE': The staff disagrees with this assertion and points out that in the same section of

the guidance, the reviewer is directed to evaluate whether there is reasonable assurance that

DOE alternate criteria for waste that exceeds Class C concentration limits are protective of

public health and safety.

COMMENT: One commenter asked whether the term "comparable" meant that DOE could

exceed the 10 CFR 61 limits by any amount DOE wished.

RESPONSE: Section 2.4.5 of the guidance explains that DOE could propose to dispose of

waste that is not covered by the Ronald W. Reagan National Defense Authorization Act for

Fiscal Year 2005 (NDAA) in accordance with alternate safety requirements. However, DOE

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is expected to provide an adequate technical basis that demonstrates that the proposed

alternate safety requirements are "comparable" with the 10 CFR Part 61, Subpart C,

performance objectives. To date, DOE has not proposed any criteria other than 10 CFR Part

61, Subpart C.

COMMENT: One commenter noted that an interim report about tank wastes at Savannah River

Site (SRS) produced by the National Academy of Sciences (National Academy of Sciences,

2005) indicated that the authors had not seen analyses supporting DOE's claim that it would be

impractical to dismantle and remove underground tanks used to store reprocessing waste.

RESPONSE: DOE's environmental impact statement for tank closure at SRS includes

estimates of worker dose and financial costs that would be likely to result from exhumation of

tanks at SRS, but does not include detailed supporting analyses. NRC staff recognizes that the

estimated risks and costs associated with exhuming the tanks are uncertain because DOE has

not previously performed similar activities.

Section 3.3 of the draft guidance directs reviewers to evaluate whether DOE considered

technologies that minimize the volume of residual waste as well as technologies that selectively

remove one or more highly radioactive radionuclides from the waste. In addition to these

alternatives, it also is appropriate to consider the practicality of removing contaminated

equipment for disposal instead of stabilizing it in place. Thus, it appears to be appropriate to

consider the practicality of exhumation and disposal of waste tanks. NRC staff expects that the

level of detail presented in any such analysis would be based on the level of detail necessary to

distinguish exhumation from other options and may be limited by the uncertainty in available

information. Text has been added to Sections 2.4.3 and 3.3 of the guidance to clarify this point.

COMMENT: A member of the public expressed the opinion that the $2,000 per person-rem

conversion factor discussed in Section 3.4 of the draft guidance does not place an appropriate

value on human life. The commenter expressed concern that the conversion factor will be

devalued by inflation and suggested that an appropriate cost-benefit metric should be related to

mortality data and appropriate discounting rates.

RESPONSE: NRC uses a $2,000 per person-rem conversion factor in regulatory analyses and

some types of ALARA analyses. As described in NUREG-1 530 (NRC, 1995), the factor is

based on a representative value of a statistical life of $3 million multiplied by a risk coefficient of

7 10-4 per rem. This risk coefficient accounts for the chance an exposed individual will

experience nonfatal cancer, fatal cancer, or serious genetic effects, and a judgment of the

severity of the nonlethal effects. The factor applies only to individuals receiving low doses of

radiation that are below NRC's dose limits. It does not apply to deterministic health effects that

could result from high doses to particular individuals, including early fatalities, because no death

will ever be "acceptable" to NRC in the sense that NRC would regard it as a routine or

permissible event. As discussed in NUREG-1530, NRC's dollar per person-rem conversion

factor is revised periodically to account for changes in the value of the dollar (i.e., the effects of

inflation), new research addressing the appropriate value of a statistical life, or changes in

recommended radiation risk coefficients. In applying the conversion factor to future averted

doses, NRC staff use economic discounting to adjust monetary values to present-day values.

Section 3.4.1 of the draft guidance describes reasons that NRC's $2,000 per person-rem

conversion factor is not expected to be applicable to DOE waste determinations. In response to

C-4
comments received about the applicability of collective dose metrics, this discussion has been

expanded in the revised guidance.

COMMENT: Two commenters expressed opinions about the identification of highly radioactive

radionuclides. One commenter suggested that NRC should ensure that long-lived mobile

isotopes, such as Tc-99 and 1-129, be designated as highly radioactive radionuclides.

Another commenter observed that all radionuclides that contribute significantly to the dose to a

potential receptor at any time during the period of assessment should be identified as highly

radioactive radionuclides.

RESPONSE: As described in Section 3 of the draft guidance, NRC staff believes that highly

radioactive radionuclides are those radionuclides that contribute most significantly to risk to the

public, workers, and the environment. Because highly radioactive radionuclides are defined in

terms of the risk they pose to various receptors, there is no single list of highly radioactive

radionuclides that is used in all waste determination reviews. Rather, the choice of highly

radioactive radionuclides is expected to be specific to each particular waste determination.

NRC staff agrees with the commenter's observation that all radionuclides that contribute

significantly to the dose to a potential receptor at any time during the period of assessment

should be identified as highly radioactive radionuclides for the relevant waste determination.

To clarify these points, an example has been added to Section 3.2 illustrating the selection of

highly radioactive radionuclides when doses occur through different pathways and at

different times.

The other commenter stated that NRC must ensure that adequate protection from long-lived

mobile isotopes is achieved. NRC staff understands that the potential risks from long-lived,

mobile radionuclides must be assessed carefully and believes that the review guidance

provided in Sections 4 and 5 of the draft guidance will facilitate assessment of these risks.

However, NRC staff notes that, as described in Section 10 of the guidance document, NRC's

role is limited to assessing whether appropriate performance objectives will be met, rather than

ensuring that appropriate performance objectives will be met, because NRC does not have

regulatory authority over DOE's disposal actions.

COMMENT: Two commenters expressed opinions about the types of costs and benefits that

should be included in the evaluation of radionuclide removal. One commenter expressed

concern that the draft guidance does not direct reviewers to consider all relevant requirements

or the full range of costs associated with the proposed disposal actions. As examples of

additional requirements that should be considered, the commenter cited State laws, Federal

laws such as the Comprehensive Environmental Response, Compensation, and Liability Act

(CERCLA), Tribal treaty rights, requirements for the prevention of the spread of contamination,

and requirements for the protection of groundwater for its best beneficial use. As an exampje of

an additional cost that should be considered, the commenter cited costs associated with

damage to natural resources and expressed the specific concern that the impact of uranium and

technetium on groundwater at the Hanford site could be "immense." Another commenter

expressed the view that scheduling and programmatic considerations should not be included in

the assessment of whether highly radioactive radionuclides have been removed to the

maximum extent practical. Specifically, the commenter expressed the opinion that such

considerations are "beyond the bounds" of the fundamental principles of health physics,

including the principle that doses should be maintained as low as is reasonably

achievable (ALARA).

C-5
RESPONSE: NRC staff recognizes that additional State, Federal, and Tribal requirements may

apply to the DOE at sites discussed in the draft guidance. The draft guidance does not direct

reviewers to assess compliance with these additional requirements, because they are beyond

the scope of NRC's authority. NRC staff understands that compliance with these regulations

and obligations is likely to impose costs on DOE. However, because DOE must comply with

applicable regulations and treaty obligations no matter which radionuclide removal activities

are performed, the cost of complying with these obligations would not affect the analysis of the

practicality of performing additional radionuclide removal. Therefore, the guidance has not

been changed to direct reviewers to consider the costs of complying with these additional

requirements.

The commenter's suggestion that the guidance should direct reviewers to consider costs

associated with damage to natural resources is consistent with the guidance document review

procedure that directs reviewers to consider reduction in risk or dose to the public, workers, and

the environment as benefits in any cost-benefit analysis that supports a decision about the

practicality of additional radionuclide removal. To clarify this point, a table listing reduction in

impacts on natural resources as a potential benefit of additional radionuclide removal has been

added to Section 3.4 of the guidance document. Similarly, the potential environmental impact of

additional radionuclide removal activities (e.g., disruption due to exhumation of buried piping) is

included as a potential cost of additional radionuclide removal.

The dose standards set in 10 CFR Part 61, Subpart C are protective of public health and safety,

therefore, NRC staff does not agree that waste that meets the performance objectives would

result in "immense" costs due to groundwater contamination. However, it is possible that

releases of waste that meet the performance objectives of 10 CFR Part 61, Subpart C, could

cause wellhead concentrations of some radionuclides to exceed U.S. Environmental Protection

Agency's (EPA's) Maximum Contaminant Levels. As discussed in other contexts [e.g., NRC's

guidance regarding ALARA analyses for license termination (NUREG-1757, Appendix N)], it is

appropriate to include the potential cost reductions that other entities, such as public water

supply utilities, may incur to meet the requirements of the Safe Drinking Water Act as benefits of

additional radionuclide removal in cost-benefit analyses. Therefore, text has been added to

Section 3.4 to explain this point, and potential cost reductions of other entities have been

included in the new table of potential costs and benefits added to Section 3.4.

Although it can be appropriate to consider potential environmental impacts, NRC staff has not

changed its guidance that the primary costs and benefits of additional radionuclide removal are

expected to be financial costs and changes in the potential doses to workers and members of

the public. Doses to workers and members of the public, as well as financial costs, are

expected to be the primary considerations because waste that meets the performance

objectives is expected to be protective of public health and safety. NRC staff recognizes that

the relevant sites may have significant existing environmental contamination due to historical

practices or accidents. However, remediation of this contamination is beyond the scope of the

guidance, which pertains only to waste determined to be non-high level waste (HLW) pursuant

to the NDAA or other applicable criteria, as discussed in Section 2 of the guidance document.

As described in Section 2.4 of the guidance document, NRC staff has concluded that the

unqualified use of the word "practical" in the NDAA Criterion 2 allows for a relatively broad range

of topics to be considered. NRC staff disagrees with the opinion that it is inappropriate to

consider impacts on DOE's mission or schedule in assessing compliance with NDAA

Criterion 2, because such impacts affect the practicality of radionuclide removal activities.

C-6
Furthermore,.Section 3.4 directs reviewers to consider scheduling or programmatic

considerations in terms of potential dose to workers or members of the public and financial

costs. Changes in potential dose and financial costs attributable to schedule or mission impacts

appear to be no less applicable to the assessment of compliance with NDAA Criterion 2 than

any other financial costs or effects on dose associated with radionuclide removal. NRC staff

also disagrees with the commenter's statement that such considerations are beyond the bounds

of the ALARA principle and note NRC's definition of the ALARA principle explicitly includes "societal and socioeconomic considerations" in addition to technical and economic

considerations (see 10 CFR 20.1003). For these reasons, no changes have been made to the

guidance document in response to this comment.

COMMENT: One commenter noted that differences between the commercial disposal of

low-level waste (LLW) and incidental waste make it inappropriate to apply the Class C

concentration limits developed for commercial LLW to incidental waste.

RESPONSE: In response to this comment and other related comments, the guidance

document sections related to concentration averaging have been revised. Details of the

changes to the guidance are discussed in more detail later in this appendix.

COMMENT: One commenter expressed disagreement "with the NRC's characterization that

DOE may implement Order 435.1's waste incidental to reprocessing (WIR) evaluation criteria to

reclassify HLW in States not covered by the NDAA."

RESPONSE: The NDAA only applies to the States of South Carolina and Idaho. For waste

determinations that DOE may make that are not covered under the requirements of the NDAA,

the NRC has no role in a DOE decision to use DOE Order 435.1. The guidance document

describes a systematic review process NRC staff will use to ensure consistency in its reviews of

waste determinations, whether they are performed under the criteria specified in the NDAA or

another set of criteria. Page xix of the guidance document has been clarified.

COMMENT: One commenter expressed concern that NRC may decide not to apply the same

criteria to DOE's waste determination activities as to the New York State Energy Research and

Development Authority's (NYSERDA's) license termination activities.

RESPONSE: The NRC's West Valley Policy Statement sets forth the criteria NRC staff will use

to evaluate DOE's incidental waste determinations at the West Valley site. The Commission

noted that it included WIR criteria in the Policy Statement "in light of the fact that the site will

ultimately revert to control by NYSERDA under an NRC license [and so] both NYSERDA and

NRC have an interest in ensuring that the incidental waste determination [made by DOE] need

not be revisited." The Policy Statement further notes that "[c]onsistent with the overall approach

in applying the [License Termination Rule] to the WVDP and to the entire NRC-licensed site

following conclusion of the WVDP, the resulting calculated dose from the incidental waste is to

be integrated with all the other calculated doses from material remaining ... at the entire

NRC-licensed site."

COMMENT: A number of commenters expressed opinions on the ratio specified in the

Category 2 approach for concentration averaging (factor of 10 for the ratio of unstabilized to

stabilized radionuclide concentrations for waste classification purposes); some stated that it was

too large and others that it was too small.

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RESPONSE: The Category 2 approach to averaging is intended to be a risk-informed approach

balancing the desire to consider aspects specific to waste classification for incidental waste with

maintaining consistency with past principles while ensuring protection of public health and

safety. 10 CFR Part 61 addresses stabilization of waste for disposal, but it is for the scenario of

waste that can be well mixed with a stabilizing agent and placed in a container for shipment and

disposal. The concentration averaging guidance for commercial low-level waste disposal

addresses many common situations and different waste types.

The Category 2 approach is consistent with the principle expressed in 10 CFR Part 61 that

averaging over the waste is permitted. Waste in incidental waste determinations may be bulk

waste that can be mixed with a stabilizing agent, but it may also be thin layers of material that

adhere to surfaces within large, engineered storage systems. The Category 2 approach is a

simple and straightforward method of estimating concentrations for waste classification

purposes without explicitly developing all of the constraining conditions and factors for every

imaginable problem.

The stabilizing agent most commonly considered (to date) for incidental waste is cement or

grout. A cementitious wasteform should readily be able to achieve a waste loading of 10 mass

percent and probably higher. Therefore, the factor of 10 derived from this simple approach

provides a reasonable boundary for determining when a straightforward waste classification

argument can be made (based on the need to stabilize waste) and a more risk-based approach

may be necessary (based on the need to stabilize waste in a particular disposal system). The

factor of 10 is not arbitrary; rather, it is based on waste stabilization experience with

cementitious materials.

A Category 3 approach has been developed to allow greater flexibility to consider the unique

aspects of incidental waste classification. It is not an arbitrary mechanism to reclassify waste;

rather, it is a risk-informed approach to recognizing the differences between incidental waste

disposal scenarios and commercial low-level waste disposal scenarios. The greater flexibility

comes with the expense of the increased burden of more detailed calculations and more review

effort by NRC staff. The concentration averaging guidance has been revised in Section 3.5.1.1,

and a new appendix (Appendix B) has been added describing the approach.

COMMENT: One commenter expressed the opinion that the types of concentration averaging

approaches that are acceptable would not be protective.

RESPONSE: Concentration averaging that may be performed for waste classification purposes

may be different from the approaches used to represent waste in a performance assessment.

The guidance indicates that either the actual distribution of waste or a distribution that is

conservative with respect to the estimated risk calculations needs to be considered in the

performance assessment.

COMMENT: One commenter expressed concern that NRC may allow the disposal of wastes

that do not meet the Class C concentration requirements.

RESPONSE: The NDAA allows DOE, in consultation with NRC, to dispose of waste that does

not meet Class C concentration limits in South Carolina and Idaho, provided certain

requirements are met. One of these requirements is that the performance objectives of

10 CFR Part 61, Subpart C, be met such that public health and safety is protected.

C-8
If NRC determines that a proposed approach would not likely be protective of public health and

safety, regardless of the class of the waste, that conclusion would be made and documented in

the relevant TER. Note that many additional factors (other than concentration) contribute

directly to the acceptability of waste disposal, including depth of the waste, physical and

chemical form of the waste, engineered barriers, natural barriers, and waste

management practices.

COMMENT: One commenter suggested that the guidance sections related to radionuclide

inventory, identification of highly radioactive radionuclides, and removal of highly radioactive

radionuclides should include review procedures that direct reviewers to prepare concise

statements documenting the uncertainties in DOE's analyses and NRC's conclusions about the

adequacy of DOE's technical bases for its conclusions.

RESPONSE: NRC staff agrees that it is essential to document the main sources of uncertainty

in analyses supporting waste determinations. Each set of review procedures the commenter

highlighted includes procedures that direct reviewers to evaluate the uncertainty in DOE's

analyses. The review procedures also provide guidance about the likely sources of uncertainty

in each technical area.

NRC staff disagrees with the commenter's suggestion that the sets of review procedures are the

appropriate places to provide guidance about review documentation. Instead, text has been

added to Section 9 of the guidance, which provides guidance about review documentation to

remind reviewers that a TER should include a description of the major sources of uncertainty in

DOE's analyses. No change was made to the guidance document to indicate that reviewers

should document their conclusions about the adequacy of DOE's technical bases, because

Section 9 of the draft guidance indicates that a TER should document the staffs conclusions as

to whether there is reasonable assurance that the applicable criteria can be met.

COMMENT: Two commenters expressed concerns about review guidance related to

radionuclide removal activities that DOE plans to begin several years after a waste

determination is submitted. One commenter suggested NRC should remove guidance that

directs reviewers to evaluate DOE's plans to consider technological improvements that occur

after submission of a waste determination if radionuclide removal activities are expected to

begin 5 or more years later. The commenter expressed the opinion that it is unrealistic to

expect that a new technology or method that could offer a measurable improvement in

radionuclide removal without significantly increasing removal uncertainties could be introduced

only 5 years after DOE performed its initial technology selection. The commenter also

expressed the concern that continued consideration of technological improvements after

submission of a waste determination could delay radionuclide removal and increase removal

costs. Another commenter expressed the opposing opinion that NRC staff should refuse to

review any waste determination that pertains to removal actions that would not occur for several

years and recommended DOE should not submit a waste determination until it can

"demonstrably prove" that its actions will comply with the NDAA provisions.

RESPONSE: NRC staff understands the concern that evaluating radionuclide removal

technologies after submitting a waste determination could delay radionuclide removal or

stabilization. However, NRC staff cannot conclude that highly radioactive radionuclides will be

removed to the maximum extent practical if radionuclide removal technologies are selected

significantly in advance of removal activities and no effort is made to consider whether

application of improved technologies or methods could substantially improve radionuclide

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removal. NRC staff recognizes that the complete period of development of many radionuclide

removal technologies may be longer than 5 years. However, NRC believes that 5 years is a

reasonable amount of time for an existing technology that is considered to be technologically

"immature" at the time of the waste determination to be further developed and tested so that its

implementation would not significantly increase the uncertainty in predicted

radionuclide removal.

NRC staff also understands the concern that the conclusions of a review performed prior to

radionuclide removal are likely to be more uncertain than the conclusions of a review performed

after radionuclide removal is complete. However, NRC staff disagrees with the view that NRC

should refuse to review waste determinations submitted several years before radionuclide

removal actions are implemented. NRC staff expects that, in most cases, waste determinations

will be submitted less than 5 years before waste removal activities begin and that the guidance

about technological developments that occur after submittal of a waste determination will apply

to a small number of cases. However, in some cases, radionuclide removal plans may be

sufficiently complex that some of the proposed removal actions must be planned several years

in advance, and the removal actions may not be implemented for several years after the draft

waste determination is submitted to the NRC for review (e.g., plans for salt waste disposal at

SRS). In the TER documenting the review of a waste determination, NRC staff would discuss

the major sources of uncertainty in DOE's conclusions, describe the key assumptions in DOE's

analyses, and indicate whether there is reasonable assurance that DOE's assumptions

are valid.

The commenter's specific recommendation that DOE should submit waste determinations only

when it can prove that its actions will comply with the provisions of the NDAA does not appear

to be applicable to determinations relevant to Hanford and West Valley, because the NDAA

does not apply to those sites. NRC staff reviews waste determinations related to Hanford and

West Valley only at DOE's request and believes it is appropriate for DOE to request a review

whenever the review would be most useful to DOE. Although the conclusions of reviews

performed at an early stage of planning are likely to be more uncertain than the conclusions of a

review performed later, early interaction with DOE provides NRC staff an opportunity to assess

DOE's disposal plans and, in its advisory role, recommend ways in which DOE's disposal

actions or analyses may be made more robust.

NRC staff expects DOE to submit waste determinations relevant to SRS and Idaho National

Laboratory (INL) when DOE concludes it has demonstrated the provisions of the NDAA will be

met. NRC staff will then draw its own conclusions based on its review. If radionuclide removal

activities have not been completed at the time of the review, NRC staff would identify the final

radionuclide inventory as a key assumption to be verified during monitoring. In addition, NRC

staff would evaluate the technical bases for the conclusion that the projected degree of

radionuclide removal would be achieved. Although NRC staff will assess the validity of DOE's

assumptions as part of its monitoring activities at SRS and INL, NRC staff bases its review

conclusions on the data and analyses available at the time of its review. Therefore, significant

uncertainty in the final inventory could prevent NRC staff from concluding that there is

reasonable assurance that the performance objectives of 10 CFR Part 61, Subpart C, will

be met.

Because NRC staff have concluded (1) it can be appropriate to review waste determinations

that pertain to activities that will not be implemented for several years after the waste

determination is submitted and (2) in those cases, it is appropriate for NRC staff to evaluate

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DOE's program for monitoring developments in radionuclide removal technologies, no changes

were made to the guidance in response to these comments.

COMMENT: A commenter identified a need for improved clarity in Example 2-2 of the

concentration averaging section.

RESPONSE: The staff agreed with the comment, and the example in Section 3.5.1.1 has

been clarified.

COMMENT: One commenter noted that, if radionuclide removal is not complete when a waste

determination is reviewed, NRC staff should verify the final extent of radionuclide removal

achieved. The commenter suggested that the need for verification should be stated explicitly in

the sections of the guidance related to radionuclide removal (Section 3.3) and monitoring

(Section 10).

RESPONSE: Section 3.3 of the draft guidance indicates that, if DOE submits a waste

determination prior to ending removal actions, NRC staff will expect to monitor the extent of

radionuclide removal achieved and assess any impacts of changes to the extent of radionuclide

removal on meeting the performance objectives of 10 CFR Part 61, Subpart C. Section 3.3 has

been clarified to indicate that NRC staff would expect to monitor the final radionuclide inventory

only at SRS and INL. NRC staff would assess the impacts of any differences between the

expected and actual extent of radionuclide removal achieved at Hanford only at DOE's request.

As described in the guidance introduction, NRC's role with respect to license amendment or

termination at West Valley is distinct from any consultation DOE may request regarding waste

determinations relevant to the site. NRC staff expects to assess the final radionuclide inventory

at West Valley at the time of license termination.

Section 3.3 of the draft guidance also indicates that, if removal activities are not completed as

described in DOE's waste determination, NRC staffs conclusions about radionuclide removal to

the maximum extent practical (NDAA Criterion 2) may no longer be applicable. The guidance

does not indicate that NRC staff would reassess compliance with NDAA Criterion 2 based on

the actual extent of radionuclide removal achieved, because the NDAA limits NRC's monitoring

role to assessing compliance with the performance objectives of 10 CFR Part 61, Subpart C.

However, as described in Section 4.7 of the guidance, compliance with the ALARA requirement

of the performance objective for the protection of the general public from releases of

radioactivity (10 CFR 61.41) is based in part on removal of highly radioactive radionuclides to

the maximum extent practical. Thus, verification of the extent of radionuclide removal achieved

would be included in NRC's monitoring role for SRS and INL in the context of the ALARA

requirement of 10 CR 61.41.

Section 10 of the guidance describes the general framework of NRC monitoring pursuant to

the NDAA. As indicated in Section 10, detailed instructions to NRC staff are provided in

site-specific monitoring plans rather than in the guidance itself. However, Section 10 does

indicate that NRC staff performing monitoring activities should verify DOE's key assumptions

and lists the final inventory as an example of an assumption that is likely to be important to

assessing compliance with the performance objectives of 10 CFR Part 61, Subpart C.

COMMENT: One commenter expressed an opinion on the inappropriateness of using

deterministic analysis for incidental waste performance assessments and the difficulty in

selecting conservative deterministic parameters.

C-1l
RESPONSE: The staff agrees that certain types of problems are very challenging to evaluate

with a deterministic performance assessment. As a generality, this would include complicated,

highly uncertain problems that respond to independent variables in a highly nonlinear way.

However, there may be cases where a deterministic analysis, with a comprehensive sensitivity

analysis, can provide adequate basis to make a decision. In addition, there may be cases

where a simple conservative calculation may be used to demonstrate compliance. The

guidance document must apply to many different types of problems, and therefore the flexibility

to use different approaches has been maintained. To ensure that an appropriate analysis

approach has been used in the performance assessment, specific review procedures were

provided in Section 4.4.2. These review procedures have been enhanced in the revised

guidance. Note that when appropriate, NRC staff will perform independent probabilistic analysis

to enhance the review of DOE analysis. Independent analysis helps the staff to better evaluate

the DOE evaluation of uncertainty.

COMMENT: One commenter suggested the need to enhance the review procedures related to

flow paths for transport to include manmade connections.

RESPONSE: NRC Staff agrees with this comment and has revised the review procedures in

Section 4.3.4.2.

COMMENT: One commenter suggested that the review procedures related to the presence of

fast pathways through aquitards needed to be enhanced.

RESPONSE: NRC Staff agrees with this comment and has enhanced the relevant review

procedure in Section 4.3.4.

COMMENT: One commenter suggested that enhancing the review procedures in Section 4.3

was needed to add the consideration of past, present, or future plumes of organic solvents that

may affect radionuclide transport.

RESPONSE: A review procedure addressing organic solvents has been added to

Section 4.3.4. Adequate model support is needed for radionuclide transport projections. If

model support is adequate, it should be unlikely that organic solvents may have modified the

vadose zone or an aquifer such that transport times are greatly overestimated. Nonetheless,

modification of the natural system from past site uses should be considered, particularly if

radionuclide transport in natural materials significantly reduces risk.

COMMENT: Two commenters recommended changes to NRC's guidance that, in most cases,

a buffer zone is expected to extend approximately 100 m [330 ft] from the disposal area. One

commenter recommended that the guidance should indicate that a buffer zone should never

extend more than 30 m [100 ft] from the waste and should explicitly state that a buffer zone

should not allow for dilution to achieve compliance, including compliance with applicable

drinking water standards. The commenter also expressed the view that institutional controls

should not be assumed to last for more than 100 years. Another commenter expressed an

opposing view and suggested that buffer zones for DOE non-HLW sites should typically be

larger than buffer zones for commercial LLW sites to account for DOE facilities near

reprocessing wastes (e.g., production reactors or chemical reprocessing facilities near tank

farms). The commenter also noted that NRC had previously accepted DOE's use of a buffer

zone larger than 100 m [330 ft] in a waste determination review performed at DOE's request

(NRC, 2000).

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RESPONSE: The 100 m [330 ft] buffer zone size recommended in the draft guidance is

intended to be consistent with the purpose of a buffer zone as described in 10 CFR 61.7(a)(2),

which is to provide a controlled area to establish monitoring locations and to take mitigative

measures if needed. When drafting 10 CFR Part 61, NRC considered requiring that buffer

zones extend a minimum of 30 m [100 ft] from the waste to allow sufficient space for monitoring

and mitigative measures, if necessary. In comments on the draft rule, several individuals

recommended that this minimum requirement be removed and that appropriate buffer zone

sizes be evaluated on a case-by-case basis. In addition, the Army Corps of Engineers noted a

30 m [100 ft] buffer zone may not allow sufficient space for taking remedial action (NRC, 1982).

Because NRC staff originally had intended to evaluate the appropriate size of a buffer zone on a

site-specific basis, NRC decided not to include a specific size requirement for buffer zones in

10 CFR Part 61 (NRC, 1982). NRC staff has not changed its view that it is appropriate to

consider the appropriate size of a buffer zone on a case-by-case basis and therefore did not

alter the draft guidance to indicate buffer zones should never extend more than 30 m [100 ft]

from the waste. Instead, text was added to Section 4.1.1.4 to remind reviewers of the purpose

of a buffer zone.

NRC staff believes that, in most cases, a 100 m [330 ft] buffer zone will allow sufficient space

for performing monitoring activities and mitigative measures (if necessary). Although buffer

zones larger than 100 m [330 ft] may be acceptable, in general, buffer zones should not be

enlarged solely to increase radionuclide dilution. NRC staff agrees with the commenters'

suggestion that neighboring facilities may necessitate a buffer zone greater than 100 m [330 ft],

but only if it is demonstrated that the neighboring facilities would prevent appropriate monitoring

programs or any necessary mitigative actions from being implemented in a 100 m [330 ft] buffer

zone. The commenters' suggestion that a buffer zone should be extended "based on source

terms in the vicinity of the tanks such that the public should not have access" appears to imply

that a buffer zone could cover any area that DOE intends to control to prevent public access.

Thus the merit of the suggestion depends on what assumption NRC should make about the

amount of time DOE should be required to maintain control of the land.

As described in the draft guidance, NRC staff assumes that DOE will actively control public

access for 100 years after disposal site closure. NRC staff has previously considered whether

the 100-year period of institutional controls specified in 10 CFR Part 61 should be extended

(NRC, 1982). Although considered in the context of commercial LLW sites, the previous

deliberations are relevant to waste determination discussions because 10 CFR Part 61 requires

that, after closure, control of commercial LLW sites be transferred to the Federal or a State

government [10 CFR 61.59(a) and 10 CFR 61.59(b)]. A number of individuals commenting on

the draft version of 10 CFR Part 61 suggested that the period of institutional controls should be

extended because the Federal or a State government could be expected to survive for much

longer than 100 years. However, the 100-year limit is not based on how long the government is

expected to survive, but on how long the government should be expected to provide active

custodial care of the waste. Furthermore, intrusion into waste is not expected to result from the

demise of the government, but rather from an error (NRC, 1982). In regional workshops and

written public comments on a draft version of 10 CFR Part 61, a consensus was developed

supporting the 100-year limit. Based on these and other considerations, NRC staff concluded

that 100 years is an appropriate limit for reliance on institutional controls.

Because many radionuclides typical of reprocessing waste have half-lives of several thousand

years or more, in some cases the peak dose to a potential receptor is predicted to occur several

thousand years after site closure. Thus, any suggestion that the size of a buffer zone should be

C-13
based on DOE's institutional control of the land would need to anticipate governmental control

of the land for several thousand years and provide justification that the institutional controls

would be durable throughout the period. Therefore, the guidance has not been changed to

indicate that DOE non-HLW disposal sites generally should have larger buffer zones than

commercial LLW disposal sites.

The commenter is correct in noting that, in a review of a waste determination performed in 2000,

NRC staff agreed that it was reasonable for DOE to postulate a buffer zone larger than 100 m

[330 ft]. That review was performed at DOE's request prior to promulgation of the NDAA.

Because NRC was advising DOE at DOE's request, NRC performed an analysis based on the

buffer zone size agreed to by DOE and the South Carolina Department of Health and

Environmental Control, which had regulatory authority over aspects of DOE's tank closure plan.

During the review, NRC~staff requested that DOE evaluate predicted doses to a potential

receptor closer to the tank farm, including 100 m [330 ft] from the tanks, to assess the sensitivity

of dose to receptor location. Since that time, NRC performed an additional review of a waste

determination for SRS (NRC, 2005) and three reviews of waste determinations for INL (NRC,

2002, 2003, 2006). In all of these determinations, DOE used a 100 m [330 ft] buffer zone, which

NRC staff concluded was appropriate.

The commenter also correctly noted that, in some cases, the point of maximum exposure for the

public may be more than 100 m [330 ft] from the disposal area. For example, a complex

hydrogeologic system or overlap of plumes from multiple sources may cause peak

concentrations of radionuclides in groundwater to occur more than 100 m [330 ft] from the

disposal area. In a recent review of a waste determination for tank closure at INL (NRC, 2006),

NRC staff agreed that it was appropriate to assume that a member of the public was located

600 m [200 ft] from the tank farm because that was the point DOE expected would yield the

maximum greatest dose (for evaluation of 10 CFR 61.41). In this case, DOE assumed the

buffer zone extended 100 m [330 ft] from the disposal area. To clarify this point, text has been

added to Section 4.1.1.4 of the guidance to indicate that, to evaluate compliance with

10 CFR 61.41, a public receptor should be assumed to be located at the point of maximum

exposure beyond the buffer zone, and the point of maximum exposure may not coincide with

the boundary of the buffer zone.

NRC staff agrees that a buffer zone should not be enlarged solely to allow for radionuclide

dilution and has amended Section 4.1.1.4 to make this point. However, NRC staff notes that it

does not assess compliance with drinking water standards. As discussed in the guidance

document introduction, NRC's role is limited to assessing compliance with the performance

objectives of 10 CFR Part 61, or potentially, for West Valley and Hanford, performance

objectives comparable to the performance objectives of 10 CFR Part 61. NRC staff recognizes

that EPA or the affected States may implement regulatory programs for groundwater protection

and expects that DOE and the affected parties will agree on any buffer zones that are relevant

to the applicable regulations. These buffer zones may not coincide with buffer zones NRC and

DOE used for waste determinations.

COMMENT: One commenter asked whether DOE's standards for the protection of public

health and safety would be equivalent to NRC's standards.

RESPONSE: As described in Section 2 of the draft guidance, the waste determination criteria

relevant to Hanford and West Valley are similar but not identical to the criteria that apply to SRS

and INL. At SRS and INL, the applicable criteria (established in Section 3116 of the NDAA)

C-14
require that waste meets NRC's performance objectives for the land disposal of radioactive

waste (10 CFR Part 61, Subpart C). Thus, in waste determinations relevant to SRS and

INL, there would be no difference between the DOE-applied standards and NRC's

performance objectives.

DOE Order 435.1 and the West Valley Policy Statement indicate that waste may meet

requirements that are "comparable to" NRC's performance objectives. Thus, in waste

determinations relevant to Hanford and West Valley, there may be differences between the

DOE-applied standards and NRC's performance objectives. If DOE proposes to apply

requirements different from the performance objectives of 10 CFR Part 61, Subpart C, in a

waste determination and if DOE consults with NRC about the determination, NRC staff would

expect to discuss any differences between DOE's proposed requirements and NRC's

performance objectives in a TER. As described in the guidance introduction, NRC's role with

respect to waste determinations at West Valley is governed by the West Valley Policy

Statement and NRC's role with respect to waste determinations at Hanford is at DOE's request.

Because these points are explained in the Introduction and Section 2 of the draft guidance, no

changes have been made to the guidance document in response to this comment. It should be

noted that to date, DOE has not proposed any criteria other than that found in 10 CFR Part 61.

COMMENT: One commenter asked what is the likelihood that waste will be isolated from the

biosphere for the time that it is required to be isolated.

RESPONSE: The probability that waste will remain isolated, or what fraction of the waste is

released and when, is estimated in the performance assessment calculations. With a properly

designed waste disposal system, most of the radioactivity should decay in place prior to

eventual degradation of the facility.

COMMENT: One commenter suggested that NRC should provide the models and all model

parameters and assumptions to interested parties upon public request.

RESPONSE: The NRC documents its review in requests for information and TERs, which are

available to the public. To risk inform the review, NRC staff may perform independent technical

analyses and develop computational models. The analyses and models are a review tool to

inform the evaluation and are not the basis for conclusions. Conclusions of a waste

determination review are based on DOE analyses and models and their associated results.

NRC does not intend to make internal review tools publicly available. In the course of a review,

NRC staff attempts to evaluate any information relevant to the technical review, including

information from non-DOE sources. NRC staff willingly considers analysis performed by

other stakeholders.

COMMENT: One commenter suggested that there is little evidence that institutional controls

can be maintained for periods even approaching 100 years.

RESPONSE: Consistent with 10 CFR Part 61 for commercial LLW disposal, active institutional

controls are assumed to be maintained for 100 years following closure of an incidental waste

system. The only direct information to support the validity of the assumption is the Beatty,

Nevada LLW facility that has been successfully closed, monitored, and maintained since 1992.

Operating LLW facilities have not had inadvertent uses of their sites. DOE sites have

maintained both active and passive institutional controls for 50 years or more. For a commercial

LLW facility, there are requirements of the land owner or custodial agency with respect to

C-1 5
institutional controls, which provide the primary basis for assuming a 100-year effectiveness

period. DOE has requirements for control and maintenance of its sites.

COMMENT: One commenter pointed out that 10 CFR 61.41 specifies the dose limit to "any

member of the public." The commenter suggested that the guidance document should provide

additional guidance for either deterministic or probabilistic assessments as to the desired

endpoint and confidence bounds for analysis.

RESPONSE: Section 4.3.5.1.2 discusses the average member of the critical group, which is

the receptor definition NRC uses for dose assessments. A corresponding review procedure has

been added to Section 4.3.5.2. Section 4.6.2 provides a review procedure to ensure that

appropriate performance measures have been used in the performance assessment. For a

deterministic analysis, it is peak dose. For a probabilistic analysis, it is peak mean dose.

For most probabilistic assessments, the mean dose is a high percentile of the resulting

dose distribution.

COMMENT: One commenter stated that NUREG-1757 was incorrectly referenced as

requirements in Section 8, that the requirements of 10 CFR Part 50, Appendix B, do not apply,

and that graded quality assurance should be followed.

RESPONSE: The incorrect reference in Section 8 has been changed. The reference to

10 CFR Part 50, Appendix B, was only provided as an example of an acceptable quality

assurance program to ensure data quality, and therefore, the reference is appropriate and has

been maintained. The staff agrees that graded quality assurance may be used, and additional

text has been added to Section 8.

COMMENT: Two commenters stated that the content of the draft monitoring section of the

guidance document went beyond what was intended under the NDAA. The commenter

suggested that monitoring should focus on measurements that indicate overall performance of

the facility, similar to monitoring performed at other contaminated sites where environmental

monitoring is emphasized. Furthermore, the commenters suggested that monitoring to

substantiate DOE's assumptions and analyses is impractical in an annual monitoring cycle,

while reviewing site monitoring reports and other environmental reports is very appropriate and

consistent with NRC practice.

RESPONSE: Section 10 (Monitoring) of the guidance document has been extensively revised

and now discusses how NRC interprets its role in monitoring disposal actions under the NDAA

and how this differentiates from environmental monitoring. The new section on overall

approach and scope of NDAA compliance monitoring in the guidance document states that the

NDAA indicates NRC must monitor DOE's disposal actions to assess whether the actions are in

compliance with the performance objectives of 10 CFR Part 61, Subpart C. Because the

performance objectives include a general requirement that there is reasonable assurance that

exposures to humans will not exceed the limits established in 10 CFR 61.41 through 44, DOE's

disposal actions would be out of compliance if NRC no longer had reasonable assurance that

the requirements of 10 CFR 61.41 through 44 would be met. As described in Sections 4-7 of

this guidance document, NRC staff typically derives assurance that the requirements of

10 CFR 61.41 through 44 will be met on predictions of long-term site performance. Therefore,

monitoring to assess compliance with the performance objectives is expected to include

activities necessary to maintain confidence in DOE's predictions of long-term site performance.

Although environmental monitoring (i.e., monitoring the environment for changes and collecting

C-1 6
environmental data) is expected to provide the most clear and straightforward way to assess the

performance of a disposal facility, in practice there are limitations to solely relying on

environmental data to evaluate the performance of the type of disposal facilities that are the

subject of DOE's waste determinations. Because DOE typically relies on a number of

engineered features (e.g., grout, concrete vaults, specialized covers) to close their facilities, it

may be several decades or centuries before any radioactive materials are expected to be

released from the disposal facility, and thereafter be detected. While observing DOE actions

and reviewing environmental data are expected to be components of NRC's monitoring

activities, building confidence in DOE's selection of parameters and models will be a critical

monitoring activity. Accordingly, it is important for staff to use the performance assessment to

identify those aspects of the disposal system that have the largest influence on performance so

that these areas can be the focus of NRC's monitoring activities. In addition, it is important for

staff to monitor those parts of the disposal system with here there is the greatest amount of

uncertainty that NRC's performance objectives will be met.

COMMENT: Two commenters suggested that the West Valley site should be included in the

discussion of monitoring in the guidance document. One of the commenters pointed out that

the West Valley Demonstration Project Act calls for NRC to monitor DOE's activities at West

Valley for the purpose of assuring public health and safety and believes that this is similar to

NRC's role under the NDAA. The commenter believes that NRC's monitoring at West Valley is

a good example of how monitoring can and should be performed and should provide a

benchmark to measuring monitoring proposals under the NDAA.

RESPONSE: NRC staff believes that there are important differences between its monitoring

role under the NDAA and at West Valley. NRC's monitoring role under the NDAA is narrowly

focused on assessing DOE's compliance with the performance objectives set out in 10 CFR

Part 61, Subpart C. As explained in the guidance, a large part of this responsibility is predictive

in nature in that NRC must assess whether it continues to have reasonable assurance that the

performance objectives will be met in the future. NRC's role at West Valley is broader inthat

NRC monitors all of DOE's activities under the demonstration project and the focus is more on

ongoing activities such as those associated with the environmental monitoring program,

disposal area maintenance, and review of reports and analyses. NRC examines the future

status of the West Valley site by participating in the preparation of the environmental impact

statement and by verifying DOE's compliance with NRC's decommissioning criteria. At this

point, no WIR waste determination process has been started at West Valley. If appropriate,

guidance on monitoring disposal actions pursuant to a waste determination at West Valley may

be included in a revised version of this guidance document.

COMMENT: Two commenters questioned how NRC staff planned to monitor different aspects

of disposal actions (e.g., how would NRC staff monitor infiltration rates and wasteform

degradation?). In addition, one of the commenters suggested that certain monitoring activities

are unrealistic or unnecessary. The examples provided were (1) monitoring intrusion

performance would not be pertinent until well beyond the 100-year institutional control period

(2) protection of individuals during operation and offsite releases are well covered by various

DOE orders consistent with 10 CFR Part 20 and duplicate monitoring efforts are not needed;

(3) monitoring each batch of waste and actual sampling of some or all the batches by NRC staff

seems unreasonable and is not required; and (4) monitoring the performance assessment

process and its updates is not normally part of the monitoring program.

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RESPONSE: To confirm key aspects of or assumptions used in DOE's performance

assessment to demonstrate compliance, NRC staff will carry out technical review and onsite

observation activities. If infiltration rates and wasteform degradation were identified -as being

key aspects in NRC's technical evaluation, monitoring activities could include observing relevant

experiments, reviewing the results of experiments, and reviewing analyses or expert elicitation

regarding the long-term performance of the infiltration barrier or wasteform. Specific examples

of technical information evaluated for monitoring of infiltration and wasteform performance could

include reviewing moisture characteristics for the grout, curing time and techniques for the

grout, and information on the dissolution of salts and low solubility matrix phases within

the grout.

To assess the potential for noncompliance in the future for a particular performance objective

(e.g., 10 CFR 61.42), key aspects of the performance demonstration should be monitored in the

present. This could include monitoring activities that substantiate which erosion control designs

adequately prevent inadvertent intrusion and onsite observations of the construction of an

erosion barrier. Potential long-term compliance monitoring activities to substantiate key aspects

of DOE intruder analyses may include assessing erosion cover maintenance including

maintenance to control subsidence, biotic intrusion, and vegetative cover performance.

Monitoring activities to assess compliance with 10 CFR 61.43 are not expected to duplicate

DOE efforts, but instead will help to understand and assess DOE's monitoring program. This

will be done in a graded approach that will require fewer NRC monitoring activities as the

monitoring period continues.

NRC staff plans to observe waste sampling activities, review waste sampling data, review

DOE's waste sampling plans, and review quality assurance procedures for waste sampling to

substantiate stated radioactive inventory. If a key aspect of DOE's performance demonstration

is that the highly radioactive radionuclide concentrations in the waste would not be greater than

the projected concentrations that were used to support DOE's waste determination, then NRC

staff would request information about radionuclide concentrations. However, NRC staff does

not plan to perform waste sampling, but instead is expected to observe and review DOE's waste

sampling activities.

DOE's performance assessment is a critical element of its demonstration of compliance with the

performance objectives for 10 CFR 61.41 and 42 because it forms the primary basis for

concluding that the performance objectives will be met. Because the performance assessment

is important to the performance demonstration, NRC staff must evaluate the adequacy of

revisions and updates to it. The depth of the performance assessment review will depend on

the type of changes to DOE's performance assessment and how these changes and the

impacts of the changes are documented and referenced.

COMMENT: Three commenters correctly pointed out that the NDAA has no requirements for

DOE to submit a monitoring plan to the NRC and that NRC staff should be cognizant that DOE

will not develop a monitoring plan to solely meet the NDAA because it is an NRC responsibility.

RESPONSE: NRC is cognizant that it is NRC's responsibility to monitor DOE's disposal actions

to assess compliance with the performance objectives set out in 10 CFR Part 61, Subpart C,

and that, although DOE is required to develop a monitoring plan for DOE's internal use under

DOE Order 435.1, it is NRC's responsibility to develop a monitoring plan to meet the

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requirement stipulated under NDAA, Section 3116, Paragraph (b)(1). Section 10 has been

clarified on this point.

COMMENT: Two commenters pointed out that NRC had oversight for both the Hanford and

Barnwell disposal sites until the 1990s. NRC inspectors and headquarters staff inspected both

facilities each year and reviewed the annual monitoring data to assure that the site continued to

operate in compliance with the 10 CFR Part 61, Subpart C, performance objectives. Further,

the commenter suggested that the covered States and NRC could conduct similar

environmental monitoring visits as often as necessary for.NRC to fulfill its obligations under

the NDAA.

RESPONSE: For most facilities, DOE currently relies on robust engineered barriers to isolate

waste and contaminants, and it may be several decades or centuries before radioactive

materials are expected to be released from the disposal facility. In comparison, the Hanford and

Barnwell disposal sites rely on relatively simply designed facilities with fewer engineered

barriers, unlike the potential non-high-level waste disposal sites covered under the NDAA.

Although NRC relied more on environmental data and the activities of the State inspectors for

monitoring information during this time period, NRC was engaged and active in long-term

performance issues, as demonstrated by its examination and review of various issues by the

Office of Research. For example, the Office of Research performed research on the use of

engineered surface covers to enhance waste isolation over longer periods. Therefore, NRC

intends to use both onsite observation as well as review of any DOE research and other

activities related to long-term performance to ensure there will be reasonable assurance that the

performance objectives will be met.

COMMENT: Two commenters suggested that there was a need for dialogue and possible

resolution of compliance issues before noncompliance notification letters are sent. The

commenters further stated that DOE would expect to resolve compliance issues before such

notifications were needed. Other comments stated that draft noncompliance notification letters

should be provided to DOE, and that comments from DOE and the covered State on the

compliance issues be released together with the final noncompliance notification letter.

RESPONSE: Section 10 of the guidance document has been revised. A graded approach is

described in which DOE is given the opportunity to understand NRC's concerns with respect to

compliance issues and DOE is allowed time to identify an appropriate path forward and to

respond. The guidance document section on noncompliance notification letters states that

"Prior to sending out Type I-Ill letters, NRC will review its concerns in a letter

(Type IV) to DOE and the State. This will give the State an opportunity to provide

input and comment and provide DOE with an opportunity to provide information

that demonstrates its disposal actions are in compliance with the performance

objectives. Assuming that DOE provides information to support its performance

demonstration, NRC will review this information and decide whether it is sufficient

to conclude that there is reasonable assurance that the performance objectives

will be met. If the staff determines that, based on the information DOE provided,

there is sufficient basis to conclude that DOE is in compliance, NRC will send out

a notification of resolution letter (Type V). Type IV and V letters will be made

publicly available on NRC's website. These letters formally document resolution

of the issue. If the staff determines that, based on the information DOE provides,

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there is still a basis for concluding that DOE is noncompliant, NRC will transmit

the noncompliance notification letter (i.e., Type I-Ill)."

In addition, the periodic compliance monitoring report should also serve as a vehicle for tracking

the status of the monitoring activities in terms of whether the activity is considered closed, open,

or open-noncompliant. Before the periodic compliance monitoring report would be published, it

is envisioned that staff will regularly meet with DOE and the State to discuss the status of the

monitoring program. This meeting could be especially useful in discussing activities that are still

open, the actions that are needed to close activities, and potential areas of concern.

The NDAA does not require NRC and NRC does not intend to provide DOE with a draft periodic

noncompliance notification letter, nor does NRC intend to simultaneously release potential DOE

and State comments on the draft noncompliance notification letter with a final noncompliance

notification letter. However, all types of notification letters (listed in Table 10-2 of the guidance

document: noncompliance, concern, and resolution) and the periodic compliance monitoring

report will be made publicly available and will be accessible on NRC's website.

COMMENT: Three commenters provided comments related to the covered State's role in

NDAA compliance monitoring. One comment suggested that monitoring should not be modified

to satisfy the requirements of the covered State's role unless NRC needs that information to

carry out its responsibility. Another comment recommended that additional consultation should

occur with the covered State to ensure that the essential components of monitoring under the

NDAA are addressed in the monitoring chapter of the guidance document.

RESPONSE: NRC staff agrees that monitoring activities should not be modified to satisfy the

requirements of the covered State's role unless NRC needs that information to carry out its

responsibility under the NDAA. With regard to consultations with the covered state, the revised

monitoring section of the guidance document states that

it is recommended that discussions with the covered State concerning

monitoring occur during the waste determination review. Discussions with the

State will enable NRC staff to determine the type of activities the State will be

undertaking in terms of monitoring compliance with its regulatory requirements,

and enable the covered State to understand the type of activities that NRC will

be undertaking. Insights gained through these discussions may help the

two parties coordinate their activities in order for NRC to meet its NDAA

monitoring responsibilities. In some cases, NRC may be able to rely upon

State-obtained information."

COMMENT: Three commenters provided comments related to the covered State's role in

determining what actions would be taken in response to a noncompliance notification letter.

The commenters suggested that the State is not necessarily in a position to take action. One

commenter suggested that it is possibly inappropriate to say that the covered State has specific

regulatory authority at the DOE site and that it would be more appropriate to say that the

covered State may have specific regulatory authority at the DOE site.

RESPONSE: Section 10 of the guidance document has been modified to clarify the covered

State's role with regard to any potential regulatory authority.

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COMMENT: One commenter suggested that the number of DOE site visits seemed inadequate

and that local residents should be included in site visits.

RESPONSE: Section 10 of the guidance document has undergone extensive revision since the

draft document was published. Section 10 now contains a complete discussion about the need

for onsite observation visits and the resources needed when NRC staff goes to the site to

monitor DOE waste disposal actions. The number of onsite visits needed will depend on the

nature and number of monitoring areas and the status of DOE activities. As monitoring

proceeds, new monitoring areas could be developed. However, it is expected that NRC's

monitoring activities will decrease over time. DOE controls access to DOE sites, and NRC has

a very limited role with regard to who should have access to the DOE site. Further, NRC will

prepare reports after each site visit that documents the results of each visit. The reports will be

publically available.

COMMENT: One commenter suggested that NRC include information in the guidance

document regarding how DOE and NRC will comply with the National Environmental Policy

Act (N EPA).

RESPONSE: Because NRC's role is limited to reviewing-DOE actions, NRC is not required to

prepare an Environmental Impact Statement under the NEPA requirements. DOE is

responsible for fulfilling its own NEPA requirements, and the NRC has no role or authority over

those activities. No changes were made to the guidance as a result of this comment.

COMMENT: One commenter suggested that the guidance document is based on the flawed

assumptions that barriers will perform as designed for very long periods of time and that

institutional controls will be maintained in perpetuity.

RESPONSE: The guidance document is not based on the assumption that institutional controls

will be maintained in perpetuity; rather, it is assumed that institutional controls will be maintained

for 100 years, consistent with the institutional control period for commercial LLW facilities. The

document does provide review procedures to evaluate the performance of engineered and

natural barriers. Reviewers are directed to consider relevant experience and uncertainties in

the estimates of long-term barrier performance.

COMMENT: Two commenters suggested that complex geology can invalidate the assumption

of plug flow in homogeneous materials.

RESPONSE: The review guidance does not presuppose that flow will be in homogenous,

isotropic media. Rather, review procedures are provided to evaluate uncertainty in flow paths,

particularly flow in preferential pathways.

COMMENT: Two commenters pointed out that isotopes of uranium, technetium, iodine,

neptunium, americium, selenium, and cobalt form anions in soil and that the soils do not easily

retain anions (with specific reference to the Hanford site).

RESPONSE: The guidance document provides review procedures for evaluating radionuclide

sorption in a variety of materials, including natural materials, considering site-specific

conditions. The staff agrees that the electrical charge on the chemical species can significantly

affect transport phenomena.

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COMMENT: One commenter pointed out the need to consider complexities when evaluating

evapotranspiration (ET) barriers.

RESPONSE: The staff agrees that assessing ET covers must consider variation in processes

at an appropriate temporal scale. New review procedures have been added in Section 4.3 to

provide guidance specific to ET barriers.

COMMENT: Three commenters pointed out that the NDAA did not have any legal standing in

the States of Washington and New York.

RESPONSE: On page xviii of the guidance document, it states that the NDAA is applicable only

in the States of South Carolina and Idaho.

COMMENT: One commenter suggested that the guidance allows averaging of stabilizing

materials and grout, while specifically directing that such averaging is not to be used in

performance assessments.

RESPONSE: Averaging is allowed for waste classification because the exposure scenarios

used to develop the classification limits would be expected to result in mixing of waste and

nonwaste during waste exhumation. Averaging is also allowed in the performance assessment

calculations if the assumption of waste distribution can be demonstrated to be conservative. If it

cannot be demonstrated to be conservative, then the actual distribution of the waste in the

system should be used to most accurately represent the release of waste into the environment.

No changes to the guidance have been made to address this comment.

COMMENT: One commenter expressed concern that NRC's evaluation of compliance with the

performance objectives of 10 CFR Part 61, Subpart C, will not provide adequate protection if the

requirements of other parts of the regulation are not met.

RESPONSE: NRC staff understands the commenter's concern that 10 CFR Part 61 was

intended to be applied in its entirety, but disagrees with the commenter's conclusion that NRC

must evaluate compliance with all requirements of 10 CFR Part 61 to be sufficiently protective.

NRC staff believes that compliance with the performance objectives of 10 CFR Part 61,

Subpart C, will protect public health and safety. Furthermore, 10 CFR Part 61 was designed to

be applied to commercial LLW disposal facilities. Consequently, many of the requirements of

10 CFR Part 61, such as Subpart E requirements for financial assurances, are not applicable to

a Federal agency. With respect to waste determinations performed pursuant to the NDAA, NRC

staff notes it is statutorily limited to assessing compliance with the performance objectives of

Subpart C of 10 CFR Part 61. Similarly, NRC staff expects to assess whether waste at Hanford

or West Valley will meet the performance objectives of Subpart C, or comparable performance

objectives, because Subpart C is specified in the relevant criteria (see Sections 2.2 and 2.3).

As noted in the guidance, staff is directed to consider other parts of the regulation, as

appropriate, to provide additional context for certain review areas. For example, the guidance

directs staff to consider disruptive processes listed in the siting requirements in 10 CFR 61.50

when assessing compliance with the site stability performance objective (10 CFR 61.44).

COMMENT: One commenter suggested that NRC and DOE have misconstrued the meaning of

the term "waste incidental to reprocessing" and should "cease efforts to justify the incidental

waste concept as anything other than a recently created fiction."

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RESPONSE: NRC staff disagrees with the commenter's view that the concept of incidental

waste is novel or that the historical development of this concept as described in the Background

section of the Introduction is not supported by the cited documents. NRC for many years has

employed criteria to determine that certain reprocessing wastes do not need to be disposed of

in a geologic repository because they are "incidental" wastes; see, e.g.,States of Washington

and Oregon: Denial of Petition for Rulemaking, 58 FR 12342, 12345; March 4, 1993.

COMMENT: One commenter expressed the view that the statement in the Introduction that

DOE could use the criteria in DOE Order 435.1 to make an incidental waste determination is

inaccurate because when the U. S. Court of Appeals for the Ninth Circuit vacated the decision

of the U.S. District Court of Idaho [NRDC v. Abraham, 271 F.Supp.2d 1260 (D. Idaho 2003)], it

did so only on the basis of ripeness and the criteria are in plain violation of the Nuclear Waste

Policy Act of 1982. See NRDC v. Abraham, 388 F.3d 701 ( 9 th Cir. 2004).

RESPONSE: NRC recognizes that the commenter disagrees with the views of the Government

in the above-referenced litigation on the legality of making incidental waste decisions under

DOE Order 435.1. However, the Ninth Circuit's action vacating the District Court's decision

means that there is no court decision barring DOE from using the criteria in DOE Order 435.1 to

make an incidental waste determination.

COMMENT: One commenter expressed the view that the guidance in the draft document

cannot be applied legally to make WIR waste determinations at the West Valley site because it

appears that any use of WIR determinations at that site would violate both the Nuclear Waste

Policy Act of 1982 (NWPA) and the West Valley Demonstration Project Act of 1980 (WVDPA).

The commenter stated that, in both of these laws, Congress created waste classification

systems that define high-level waste (HLW) in a way that cannot be overruled by NRC. The

commenter expressed the concern that NRC was providing DOE with "de facto" authority to

dispose of its wastes onsite at the eventual expense of New York. Another commenter has

serious doubts about whether the WIR criteria can be used at West Valley.

RESPONSE: The NRC does not agree that the definitions of "high-level waste" in either the

NWPA or the WVDPA conflict with the ability to make WIR waste determinations. The NRC has

explained its view that Congress' definitions of HLW in those Acts incorporated the

understanding of the Atomic Energy Commission and of the NRC that HLW does not include

incidental waste, see, e.g., Proposed Rule: Disposal of Radioactive Waste, 53 FR 17709

(May 18, 1988). Thus, NRC's participation in a WIR determination does not "overrule" the

statutory definitions of HLW. The WVDPA requires NRC to prescribe decontamination and

decommissioning criteria to be used by DOE at West Valley. In doing so, NRC established the

criteria to be used by DOE for WIR determinations at West Valley, see Decommissioning

Criteria for the West Valley Demonstration Project (M-32) at the West Valley Site; Final Policy

Statement, 67 FR 5003, 5011-5012 (Feb. 1, 2002), but DOE relies on its own statutory authority

in making WIR determinations.

COMMENT: The same commenter objected to the suggestion in the guidance that DOE

Order 435.1 may authorize WIR determinations for waste sent offsite from the West Valley site

for the same reasons as expressed in the previous comment.

RESPONSE: DOE's ability to make WIR determinations does not conflict with the NWPA or the

WVDPA for the same reasons as given in the previous response.

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COMMENT: One commenter suggested that the procedures and requirements set forth in the

guidance document should be codified into regulations and applied to all sites where WIR

determinations are permitted.

RESPONSE: The guidance document does not contain requirements for NRC or DOE; rather,

it provides guidance to the NRC staff for evaluating DOE-developed waste determinations for

SRS, INL, Hanford, and West Valley. As explained in the Introduction, the criteria used by DOE

in making WIR determinations is dependent upon the relevant statutory regime governing the

site. NRC does not have regulatory authority over DOE with respect to its WIR determinations

and so would not be able to adopt regulations applying to DOE in this matter.

COMMENT: One commenter suggested that "Considering the factors for compliance with the

performance objectives when reviewing the West Valley determination would seem appropriate

if it is the NRC intent to rely on it when the license is reinstated. In this way the NRC staffs

developing the factors are fully aware of the determination and its basis."

RESPONSE: The NRC staff agrees that any factors important to compliance with the incidental

waste criteria may need to be considered during the analyses of any proposed West Valley

license modification or termination. At the time of this writing, DOE has not informed the NRC if

or how DOE plans to submit waste determinations for any onsite incidental waste disposal at

West Valley (e.g., as separate analyses or as part of a decommissioning plan). Therefore, the

method of documenting any incidental waste analyses will necessarily be decided at a later

date. Section 9 of the guidance document was clarified as a result of this comment.

Advisory Committee on Nuclear Waste (ACNW) Comments

COMMENT: The ACNW noted that radionuclide removal efficiency is not a meaningful

measure of risk. The Committee recommended that the review guidance concerning DOE's

decision that radionuclides have been removed to the maximum extent practical should focus

on reducing risk from the residual radionuclide inventory and the costs (e.g., financial costs,

potential increases in worker risk) of achieving risk reduction.

RESPONSE: NRC staff agrees with the Committee's view that radionuclide removal efficiency

is not a direct measure of risk. In general, no statement of removal efficiency alone is expected

to provide a sufficient basis to conclude that radionuclides have been removed to the maximum

extent practical. Text has been added to Section 3.3 to emphasize this point.

However, there are several reasons that NRC staff may need to review radionuclide removal

efficiencies. In general, the term "removal efficiency" may refer to fraction of waste removed

from a contaminated structure or the fraction of a radionuclide removed from a waste stream

(e.g., by chemical removal methods). Thus, radionuclide removal efficiencies often are directly

related to radionuclide inventory, which typically has a significant effect on the potential doses

from a disposal facility. If radionuclide removal is not complete when NRC staff reviews DOE's

draft waste determination, NRC staff may evaluate DOE's projected removal efficiencies and

associated uncertainties as one aspect of its evaluation of radionuclide inventory. In addition,

efficiencies may be used as one part of the demonstration that radionuclides have been

removed to the maximum extent practical or the demonstration that potential doses to members

of the public will be ALARA (as required by 10 CFR 61.41). For example, projected removal

efficiencies may be used as a factor to compare alternate radionuclide removal methods or

technologies. In addition, DOE may cite declining removal efficiency as a reason for ceasing

C-24
removal activities [e.g., as in waste determinations performed for tank closure at INL and SRS

(DOE, 2005a, b)]. If DOE reports declining removal efficiency to show a chosen technology has

performed to the limit of its usefulness, reviewers must verify the removal efficiencies to

evaluate DOE's basis for ceasing removal activities. The review areas and review procedures

related to removal efficiency have been revised to clarify appropriate uses of removal

efficiencies. In addition, new review procedures have been added so reviewers can evaluate

whether DOE considered options to improve removal efficiencies.

NRC staff agrees with the Committee's comment that the review of DOE's decision that

radionuclides have been removed to the maximum extent practical should focus on the potential

reduction of risk from the residual radionuclide inventory and the costs of achieving risk

reduction. NRC staff believes Section 3.4 of the guidance focuses on this comparison. The

draft document also includes guidance for staff reviewing DOE's identification of highly

radioactive (or key) radionuclides and DOE's selection of radionuclide removal technologies and

methods. NRC staff believes that these areas of review are appropriate and has retained these

sections of the guidance.

COMMENT: The ACNW recommended that a traditional approach to collective dose should not

be used to evaluate DOE's decision that highly radioactive (or key) radionuclides have been

removed to the maximum extent practical and suggested that the dose to the reasonably

maximally exposed individual (RMEI) or average member of the critical group should be

used instead.

RESPONSE: Section 3.4.1 of the draft guidance describes reasons that the $2,000 per

person-rem factor that NRC uses to convert collective dose to a dollar value in some contexts

(e.g., regulatory analyses and ALARA analyses for license termination) may not be applicable to

DOE waste determinations. As described in the draft guidance, it appears to be more

appropriate to compare the costs and benefits of additional radionuclide removal to the costs

and benefits of other similar DOE activities.

In its comments, the Committee referenced a previous letter to the Commission in which the

Committee expressed its view that collective dose has little value as an absolute measure of

risk (ACNW, 2005). In that letter, the Committee also stated that collective dose is useful for

comparing different management options (e.g., in ALARA analyses). NRC staff agrees with this

position (NRC, 2005) and believes analyses of the practicality of additional radionuclide removal

are similar to ALARA analyses in that the essential decision is whether more should be done to

reduce doses once the applicable dose limits are met. Furthermore, NRC staff believes that

DOE should choose how to quantify benefits of additional radionuclide removal and that the

review guidance should prepare reviewers to evaluate a variety of potential cost-benefit

comparisons. Thus references to collective dose calculations have not been removed from

Section 3.4.1, but the text has been revised to shift the emphasis from traditional collective dose

metrics to comparisons based on doses to individuals (e.g., the RMEI or average member of the

critical group). Additional detail has been added to the discussion of potential difficulties

associated with quantifying benefits in terms of collective dose in analyses supporting

waste determinations.

COMMENT: The ACNW made several specific recommendations about factors that should be

considered in NRC's review of DOE's selection of radionuclide removal technologies. In

addition, the Committee recommended that NRC staff should monitor the status of less mature

radionuclide removal technologies for potential future consideration.

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RESPONSE: NRC staff agrees with the Committee's recommendation that the review of DOE's

radionuclide removal technology selections should focus on systematic consideration of the

integrated cost, technology maturity, and extent to which additional radionuclides might be

removed by less mature technologies. Section 3.3 of the guidance focuses on these

considerations. The draft guidance directs reviewers to verify that DOE considered an

appropriate range of technologies, including technologies developed across the DOE complex.

In response to the Committee's comments, text has been added to Section 3.3 to direct

reviewers to evaluate whether DOE considered information from international and

industrial sources.

The Committee also noted that application of a suite of technologies may be more successful

than repeated application of a single technology and recommended that the review of

technology selection also include consideration of any potentially beneficial sequencing of and

synergism among candidate technologies. NRC staff agrees with this position and has added

similar text to the review areas and review procedures of Section 3.3. In addition, new review

procedures have been added to direct reviewers to verify that DOE considered whether

modifying its approach (e.g., redirecting mixing jets or pumps) or applying an alternate

technology could practically improve removal.

NRC staff agrees with the Committee's recommendation that NRC staff should monitor the

status of less mature radionuclide removal technologies for potential future consideration and

have noted this suggestion in Section 3.3. However, as the Committee recommended,

technology selections in waste determinations are expected to focus on relatively mature

technologies. One possible exception may be waste determinations that DOE submits several

years before beginning radionuclide removal, in which case NRC staff may make an extra effort

to learn about less mature technologies that may be mature by the time DOE begins removal

activities. However, in most cases, reviewers are not expected to focus on less mature

technologies during the review of a waste determination. Therefore, NRC staff have not added

any review procedures specifically related to less mature technologies to the review guidance.

COMMENT: The ACNW commented that the guidance should indicate that there may be

circumstances where blending of different waste classes may be appropriate.

RESPONSE: Additional emphasis has been added to the existing text to indicate that blending

of waste streams should not be undertaken solely for the purpose of waste classification.

COMMENT: The ACNW commented extensively on the concentration averaging guidance, and

they recommended developing a more risk-informed approach consistent with the specific

characteristics of the waste, disposal site, and method of non-HLW waste disposal.

RESPONSE: The concentration averaging guidance has been revised to add a third approach,

labeled Category 3. The new approach is more risk informed in that it allows consideration of

the appropriate intruder scenario when determining waste classification. Specific example

averaging expressions for different scenarios have been developed for staff to use as

benchmarks when reviewing waste classification calculations. However, the Category 3

approach entails a greater burden in completing the classification calculations and in staff

review effort of those calculations. Note that a number of aspects specific to the disposal of

commercial LLW were considered when the concentration limits and classification system found

in 10 CFR 61.55 was developed. Therefore, development of concentration averaging for

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non-HLW is significantly more complicated than simply taking the concentration limits in

10 CFR 61.55 and correcting for a new dilution volume consistent with a new intruder scenario.

COMMENT: The ACNW commented that the guidance should not indicate a need for more

stringent disposal requirements for greater than Class C waste because of large variation in the

natural system capabilities to isolate waste from site to site.

RESPONSE: The guidance about the stringency of disposal requirements for greater than

Class C waste comes from the agency position in 10 CFR Part 61. The staff agrees that some

sites may have natural system characteristics that result in a higher likelihood for waste

isolation. However, the waste classification system (concentration limits), is more directly

related to intruder scenarios that are not strongly influenced by natural system characteristics,

but are more strongly influenced by the depth and distribution of waste and especially the

disposal requirements.

COMMENT: The ACNW recommended deleting the guidance that the intruder scenario should

not be probability weighted.

RESPONSE: The staff disagrees that the guidance should be deleted. The likelihood of an

intruder event occurring (of a future person or persons intruding into a commercial waste facility)

is highly uncertain. The regulatory framework for the commercial disposal of LLW considered

that it would be unlikely that someone would disrupt waste in the future, but not impossible.

Therefore 10 CFR 61.42 was developed (based on reasonably conservative scenarios that were

not highly speculative) to ensure, in the event someone intruded into the waste disposal facility,

that public health and safety would be protected. The primary disruptive scenarios that were

envisioned were drilling to recover water or other resources or construction of a residence.

To allow the probability weighting of intruder scenarios could appear to be more risk informed

(e.g., risk = probability times consequence). However, the calculation of risk needs to include

the impact of uncertainty. Even over the last 200 years, society has changed dramatically.

Many natural processes can be forecast with some degree of confidence over long periods of

time. However, human activities are more uncertain because they are nonstationary.

The intruder dose limit that is commonly applied (though it is not specified in the regulation) is

5 mSv [500 mrem]. The consequence value is 20 times larger (and therefore the implied

probability of the scenario occurring is 20 times smaller) for the intruder compared to the offsite

member of the public. In addition, the consequence value of 5 mSv [500 mrem] is generally

comparable to the average level of exposure to a member of the public from other sources. The

current approach ensures that the maximum dose a member of the public would receive is

5 mSv [500 mrem] in the unlikely event that the intruder scenario would occur.

Note that waste depth is a primary determinant to the likelihood that waste may be disrupted,

and waste depth is considered when defining the appropriate intruder scenario.

COMMENT: The ACNW commented on a number of aspects regarding probabilistic and

deterministic approaches to performance assessment.

RESPONSE: The guidance document clearly indicates the preference for a probabilistic

performance assessment, including discussion in Sections 4.0 and 4.4.1.1 on the advantages of

the approach. Section 4.5 provides review procedures specific to assessing sensitivity and

C-27
uncertainty when a deterministic performance assessment has been completed. Specific

review procedures are provided for data uncertainty, model uncertainty, and model development

for probabilistic and deterministic analysis. Waste determinations may be performed for many

different types of waste and systems. The guidance document adequately directs the staff

assessment of both types of analyses and helps staff determine when a deterministic analysis

may be insufficient. If there are a number of key uncertainties, a factorial analysis of parameter

and model uncertainty with a deterministic model should be able to assess the impacts of

uncertainty, albeit in a somewhat more cumbersome way, just as a probabilistic assessment

would. Model support is a much more direct determinant of performance assessment adequacy

than the technique used to perform the assessment.

COMMENT: The ACNW commented that the information supporting the performance

assessment should be robust and that postclosure monitoring should not be relied upon as a

substitute for inadequate information.

RESPONSE: The intent of the guidance document is to ensure that the performance

assessment is a robust assessment of system performance. However, many uncertainties are

associated with most performance assessments, and monitoring is a mechanism to manage

those uncertainties. Monitoring is also a way to evaluate new information that may confirm or

refute previous information. Assumptions are part of any analysis, including performance

assessments. Monitoring can be used to verify assumptions; however, the staff agrees that the

performance assessment must be adequately supported to demonstrate compliance with the

performance objectives. The main elements within Section 4 (system description, data

sufficiency, data uncertainty, model uncertainty, and model support) were specifically developed

to ensure a technically adequate performance assessment. However, the staff also recognizes

that some uncertainties will be unable to be reduced when decisions are to be made. It is not

practical to require an assumption-free performance assessment. It is reasonable to expect that

key assumptions have adequate technical basis and that the assumptions can be verified during

postclosure monitoring. Monitoring is not to be used as a substitute for inadequate information,

but rather a confirmation of the previous determination of adequacy considering uncertainty.

The guidance has been clarified in Sections 4 and 10.

COMMENT: The ACNW commented on a number of aspects related to the dosimetry used in

the performance assessment.

RESPONSE: The guidance document advocates the use of dosimetry consistent with

10 CFR Part 20. This ensures that compliance calculations between 10 CFR 61.41 and

10 CFR 61.43 remain consistent, as is discussed in NUREG-1573, "A Performance

Assessment Methodology for Low-Level Radioactive Waste Disposal Facilities."

The proposed rule for 10 CFR Part 63, "Disposal of High-Level Radioactive Wastes in a

Proposed Geological Repository at Yucca Mountain, Nevada; Proposed Rule," states "As a

matter of policy, NRC considers 0.25 mSv [25 mrem] Total Effective Dose Equivalent (TEDE) as

the appropriate dose limit within the range of potential doses represented by the current

10 CFR 72.104 limit of 0.25 mSv [25 mrem] (whole body), 0.75 mSv [75 mrem] (thyroid dose),

and 0.25 mSv [25 mrem] (to any other critical organ)." (64 FR 8644)

As 10 CFR 61.41 has the same standard as 10 CFR 72.104, this policy is applicable and

therefore, Waste Incidental to Reprocessing (WIR) determinations will use TEDE, without

specific consideration of individual organ doses. In addition, the guidance specifies that intruder

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calculations should also be based on 5 mSv [500 mrem] TEDE calculations, without specific

consideration of individual organ doses, to be consistent with the dosimetry used for

10 CFR 61.41 and 10 CFR 61.43. Because of the tissue-weighting factors and the

magnitude of the TEDE limit, specific organ dose limits are not necessary to protect from

deterministic effects.

A current NRC policy allows licensees to use these systems on a case-by-case basis if they

request them. While not completely identical in detail, NRC would equate 0.25 mSv [25 mrem]

effective dose as the same as 0.25 mSv [25 mrem] total effective dose equivalent. In

NUREG-1757, Volume 2, Appendix 1.5.3.2, NRC addresses the issue for long-term

performance assessment within the scope of decommissioning. The guidance states

"Licensees may request an exemption from Part 20 to use the latest dose

conversion factors (e.g., ICRP 72). Scenarios and critical group assumptions

should be revisited to look at age-based considerations. Licensees may not 'pick

and choose' dosimetry methods for radionuclides (e.g., Federal Guidance Report

No. 11 for six radionuclides and current International dose conversion factors for

three radionuclides)."

DOE is not a licensee and would not require an exemption to use the alternate dosimetry.

However, the guidance for WIR would be consistent in that DOE should use the alternate

dosimetry for all parts of the analysis (10 CFR 61.41, 61.43, and intruder analyses) and for all

radionuclides. An exception may be for direct exposures, which were not updated for ICRP-72

and therefore would need to use the FGR-1 3 values. Additionally, staff would consider whether

age-specific scenarios or exposure groups could result in higher doses.

References

Advisory Committee on Nuclear Waste (ACNW). "Comments on USNRC Staff

Recommendation of (sic) the Use of Collective Dose." Letter from M. Ryan to N. Diaz, NRC.

September 2005.

National Academy of Sciences (NAS). "Tank Waste Retrieval, Processing, and On-Site

Disposal at Three Department of Energy Sites." 2006.

International Commission on Radiological Protection (ICRP). "ICRP Publication 60: 1990

Recommendations of the International Commission on Radiological Protection Annals of the

ICRP Volume 21/1-3." April 1991.

U.S. Nuclear Regulatory Commission (NRC). "Response to Letter from the Advisory Committee

on Nuclear Waste, Dated September 30, 2005, on 'Comments on USNRC Staff

Recommendation of (sic) the Use of Collective Dose.'" Letter from N. Diaz to M. Ryan, ACNW.

October 2005.

"Reassessment of NRC's Dollar Per Person-Rem Conversion Factor Policy."

NUREG-1530. December 1995.

"A Performance Assessment Methodology for Low-Level Radioactive Waste disposal

Facilities." NUREG-1573. October 2000.

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* "Decommissioning Criteria for the West Valley Demonstration Project at the west Valley

Site; Final Policy Statement." Federal Register, 67 FR 5009. February 2002.

"Consolidated Decommissioning Guidance." NUREG-1757, Vol.2. September 2006.

U.S. Department of Energy (DOE). "Draft Section 3116 Determination Idaho Nuclear

Technology and Engineering Center Tank Farm Facility." DOE/NE-ID-11226. DOE, Idaho

Operations Office. 2005a.

U.S. Department of Energy (DOE). "Draft Section 3116 Determination for Closure of Tank 19

and Tank 18 at the Savannah River Site." DOE-WD-2005-002. DOE-Savannah River. 2005b.

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NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

(9-2004) (Assigned by NRC, Add Vol., Supp., Rev., NRCMD 3.7 and Addendum Numbers, if any.)

BIBLIOGRAPHIC DATA SHEET

(See instructions on the reverse) NUREG-1854

2. TITLE AND SUBTITLE 3. DATE REPORT PUBLISHED

NRC Staff Guidance for Activities Related to U.S. Department of Energy Waste Determinations MONTH YEAR

August 2007

4. FIN OR GRANT NUMBER

5. AUTHOR(S) 6. TYPE OF REPORT

NRC: H. Adt, A. Bradford, N. Devaser, D. Esh, M. Fuller, A. Ridge

CNWRA: B. Brient, P. LaPlante, P. Mackin, E. Pearcy, D. Turner, J. Winterle

7. PERIOD COVERED (Inclusive Dates)

8. PERFORMING ORGANIZATION - NAME AND ADDRESS (IfNRC, provide Division, Office or Region, U.S. Nuclear Regulatory Commission, andl mailing address, if contractor,

provide name and mailing address.)

Division of Waste Management and Environmental Protection Center of Nuclear Waste Regulatory Analysis

Office of Federal and State Materials and Environmental Management Programs Southwest Research Institue

U.S. Nuclear Regulatory Commission 6220 Culebra Road

Washington, D.C. 20555-0001 San Antonio, TX 78238-5166

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (If NRC, type "Same as above", if contractor, provide NRC Division, Office or Region, U.S. Nuclear Regulatory Commission,

and maiing address.)

Same NRC address as above

10. SUPPLEMENTARY NOTES

PROJ0734, PROJ0735, PROJ0736, POOM-32

11. ABSTRACT (200 words or less)

This document provides guidance to the staff of the U.S. Nuclear Regulatory Commission (NRC) for conducting activities

related to waste determinations. Waste determinations are evaluations performed by the U.S. Department of Energy and are

used to assess whether certain wastes resulting from the reprocessing of spent nuclear fuel can be considered low-level waste

and managed accordingly. This guidance document applies to NRC activities conducted for the Savannah River Site (SRS) in

South Carolina and the Idaho National Laboratory (INL) in Idaho pursuant to the Ronald W. Reagan National Defense

Authorization Act for Fiscal Year 2005 (NDAA). The document also applies to the Hanford site in Washington, and the West

Valley site in New York. The guidance document provides information regarding the background and history of waste

determinations, the different applicabe criteria and how they are applied and evaluated, and NRC's monitoring activities that will

be performed at SRS and INL in accordance with the NDAA.

12. KEY WORDS/DESCRIPTORS (List words or phrases that will assist researchers in locating the report.) 13. AVAILABILITY STATEMENT

Incidental waste. High-level waste tanks. Waste determinations. WIR. Waste incidental to unlimited

reprocessing. Savannah River site. Idaho National Laboratory. Hanford. West Valley. 14. SECURITY CLASSIFICATION

(This Page)

unclassified

(This Report)

unclassified

15. NUMBER OF PAGES

16. PRICE

NRC FORM 335 (9-2004) PRINTED ON RECYCLED PAPER
Federal Recycling Program

UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON, DC 20555-0001

OFFICIAL BUSINESS