Slide 1

July 28, 2010

Nate Bixler

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,

for the United States Department of Energy’s National Nuclear Security Administration

under contract DE-AC04-94AL85000.

Review of 

Environmental 

Analysis of the 

Uranium Fuel 

Cycle 
Slide 2

Background

 SNL performed a review of 

 Title 40 CFR Part 190

 EPA’s environmental analysis of nuclear fuel reprocessing 

(EPA 1 520-9-73-003-D)

 Part of this review involved 

 Understanding EPA’s treatment of doses and health effects

 Verification of the doses and health effects

 Comparison with current methods 
Slide 3

Overview

 EPA methods

 Verification of EPA results

 Independent assessment of I-129 doses

 Summary
Slide 4

EPA Methods for Estimating Doses

 Standard methods for estimating atmospheric transport and 

dispersion

 Dose to maximally exposed individual (MEI) at site boundary (3 km)

 Regional (80-km circular area) population dose

 US population beyond the 80-km zone

 Worldwide population

 Five isotopes

 H-3 (12 years)

 Kr-85 (11 years)

 I-129 (16 million years)

 I-131 (8 days)

 Actinides (18 to 2 million years)

 Cooling time chosen to be 150 days
Slide 5

EPA Methods for Estimating Doses

 Simplifying assumptions for dose pathways

 Exposure to H-3 by ingestion of water

 Exposure to Kr-85 by immersion

 Exposure to I-129 and I-131 by ingestion of milk

 Exposure to actinides by inhalation of resuspended aerosols

 Simplifying assumptions for worldwide dose estimates

 Uniform dilution of Kr-85 throughout atmosphere

 Dilution of H-3 in circulating waters of northern hemisphere

 Assumptions for decontamination factors

 No decontamination (DF = 1) for H-3 and Kr-85

 DF = 1000 for iodines

 DF = 109 for actinides
Slide 6

Verification of EPA’s Dose Values

Average Individual and Population Doses from One-Year 

Release for 1980 Startup

MEI Regional US World

Radionuclide Organmrem

/yr

μrem/

yr

personrem/yr

μrem/

yr

personrem/yrμrem/

yr

personrem/yr

Kr-85 Effective 0.37 10 24 2 560 2 7,900

Lung 0.75 21 47 5 1,100 4 16,000

Skin 12 350 790 79 19,000 60 260,000

Gonads 0.44 12 14 3 330 2 4,600

H-3 Effective 3.2 89 200 16 3,900 0.2 1,000

Gonads 3.2 44 100 17 2,000 0.2 500

I-129

Thyroid 

Infant 1.4 40

Thyroid 

Adult 0.4 12
Slide 7

SNL Comments on EPA’s Dose Values

 Doses to MEI and region

 Atmospheric transport estimates are reasonable

 Doses from ingestion of I-129 appear to be very conservative 

(more later)

 US doses

 Atmospheric transport estimates are reasonable

 Minor conservatisms

 Worldwide doses

 Doses from ingestion of H-3 appear to be conservative because 

dilution is into a small fraction (1.8%) of surface waters
Slide 8

EPA Methods for Estimating Health Effects

 Health effects are assumed to be proportional to 

population doses

 Health effects are estimated for 40 years of plant 

operation

 SNL confirmed EPA health effect predictions to within 

3%
Slide 9

Verification of EPA’s Health Effect Values

Radionuclide Organ Estimated Health Effects from 40 Years of Operation

3 km Regional US World Total

Kr-85 Effective 6.0E-6 0.38 9.0 130 140

Lung 1.5E-6 0.094 2.2 30 32

Skin 1.5E-6 0.095 2.3 30 32

Gonads 5.2E-6 0.17 4.0 55 59

H-3 Effective 5.2E-5 3.2 62 16 82

Gonads 3.9E-5 1.2 24 6 31

I-129 Thyroid 

Infant 8.6E-6

Thyroid 

Adult 8.7E-8
Slide 10

Motivation for an Independent Evaluation of 

Iodine-129 Doses Using MACCS2

 Iodine-129 appeared to be the limiting isotope in terms 

of regulation

 A DF of 1000 would be difficult to achieve

 Iodine-129 dose estimates in the EPA report seemed 

larger than expected

 Some of the assumptions associated with the food-chain 

pathway were difficult to reconstruct and evaluate

 Some of the assumptions seemed very conservative
Slide 11

Comparison of I-129 Ingestion Assumptions 

EPA assumptions

 Annual release is continuous

 Exposure is by consumption of 

milk

 0.76 l/dy for infants

 0.5 l/dy for adults

 Deposition velocity is 0.5 cm/s

 I-129 in thyroid is based on lower 

than average level of stable iodine 

in environment

 Milk is produced where it is 

consumed

 No remediation or limits on 

ingestion doses are considered

MACCS2 assumptions

 Annual release occurs in 1 hr

 Exposure is by consumption of 

milk and other foodstuffs

 Typical food basket 

 0.27 l/dy milk for adults

 Deposition velocity is 0.5 cm/s

 I-129 in thyroid is based on 

metabolic model used in ICRP-72 

and FGR-13

 Milk and other food are produced 

where they are consumed

 No remediation or limits on 

ingestion doses are treated
Slide 12

Averaging Over Annual Weather Data Is 

Equivalent to a Continuous, Annual Release

Continuous Release (EPA)

 Fraction of annual release 

travels in a direction (based 

on wind rose)

1-Hour Release (MACCS2)

 Entire annual release 

travels in a direction in a 

single weather trial

 Fraction of the weather 

trials travel in a direction 

(based on wind rose)

 Average is the same for any 

result that behaves linearly

[ ,

Average ] =
Slide 13

Other MACCS2 Assumptions

 Calculations based on recycling plant collocated with 

Sequoyah NPP

 Weather data

 Population (about 1 million within 80 km) 

 Other site information (30% of land used for farming, etc.)

 Standard choices for 

 Atmospheric transport and dispersion

 Resuspension of deposited aerosols

 Food chain parameters
Slide 14

Food Basket Assumptions

 EPA analysis only considers doses from milk

 MACCS2 normally considers a typical food basket

 Based on typical diet at the time of NUREG-1150

EPA MACCS2

Milk 188 100

Grains 69

Leafy Vegetables 11

Roots 26

Fruits 46

Legumes 26

Beef 59

Poultry 9

Other Meat 10

Consumption Rate (kg/yr)

Food Type
Slide 15

Population Dose Comparison

 Table compares EPA and MACCS2 population doses assuming iodine DF = 1

 Compared with the EPA analysis

 Milk dose is a factor of 8 lower

 Ingestion dose is a factor of 2.5 lower

Effective Thyroid Effective Thyroid

Direct Inhalation 9 179

Groundshine 36 42

Resuspension Inhalation 12 236

Ingestion 27000 562 11194

Milk 27000 194 3873

Grains 38 765

Leafy Vegetables 51 1026

Roots 50 1002

Fruits 74 1467

Legumes 42 842

Beef 111 2216

Poultry 0 3

Other Meat 1 0

Annual Dose (Person-rem)

EPA

MACCS2 without 

Ingestion Limits

Dose Pathway
Slide 16

Beef

20%

Legumes

8%

Fruits

13%

Roots

9%

Leafy Vegetables

9%

Grains

7%

Milk

34%

Evaluation of Dose Pathways

 Ingestion dominates the thyroid 

dose pathways

 Milk comprises about one-third of 

the ingestion dose

Relative Contribution 

From Dose Pathways

Relative Contribution 

From Food Types

Ingestion

96%

Groundshine

0%

Direct 

Inhalation

1%

Resuspension 

Inhalation

2%
Slide 17

Dose at Site Boundary

 MACCS2 ingestion 

dose at site boundary

 140 mrem if food 

is grown at site 

boundary

 11 mrem if food is 

grown within 80 

km

Average Dose to Individuals

0

20

40

60

80

100

120

140

160

180

1 10 100

Distance from Site (km)

Dose (mrem)

Direct Exp. 

Local Ingestion

Average Ingestion

Direct Exp. + Ave. Ing.

Dose (mrem/yr)

EPA 400

MACCS2 Direct Exposure 6

MACCS2 Local Ingestion 140

MACCS2 Average Ingestion 11

MACCS2 Dir. Exp. Plus Ave. Ing. 17

Adult Thyroid Dose at Site Boundary
Slide 18

Summary

 Sandia has reassessed and confirmed EPA analysis

 Some EPA assumptions are conservative

 EPA estimates of I-129 regional doses

 Reasonable for population dose

 Conservative at site boundary because food is assumed to be 

produced there

 EPA restrictions on site boundary dose (25 mrem/yr) 

could be achieved with DF =1 for I-129