College of Engineering Oregon State University DOE’s Graded Approach for Evaluating Radiation Doses to Biota: Derivation of Screening and Analysis Methodologies

College of EngineeringOregon State University

DOE’s Graded Approach for Evaluating Radiation Doses to Biota: Derivation of Screening and Analysis

Methodologies

KA Higley, Oregon State University;

Oregon State University

Nuclear engineering & Radiation Health Physics

Overview Technical Marching Orders

Goals Limitations Conditions

Derivation of Technical Method Assumptions Screening Phase Analysis Phase

Product: Electronic Spreadsheets Ongoing Development / Implementation Issues



Technical Marching Orders Goal:

Simple, defensible, user friendly method

Limitations & Conditions: Utilize existing generic & site-specific data Broad-based application (mice to elephants) Provide departure point for in-depth analysis

Applicable to multiple media: Soil Sediment Water



Biota Dose Evaluation Methodology Technical Approach

Basic method & assumptions External dose calculation Internal dose calculation

Screening phase (Lumped Parameter) Detailed Analysis (Kinetic/Allometric)

Quality Assurance Uncertainty analysis Real-world verification



Basic Method

Dose: function of contaminant concentration in environment sum of internal & external contributions

Evaluate for unit contaminant concentration (e.g., 1 Bq g-1) single media (e.g., soil)

Ratio calculated dose to standard (e.g., 0.01 Gy d-1) Back calculate media limit Use sum of fractions approach for:

multiple media multiple nuclides



External Dose Calculations Homogeneous nuclide distribution Infinite source Infinitesimal receptor organism Source & receptor geometry:

water & soil sediment



Internal Dose Assumptions Organism is a “blob” of tissue

All decay energies retained in tissue (i.e., infinite receptor)

Alpha dose-modifying factors (i.e., wR = 20)*

Chain-decay progeny included (E.F. = 1)* Nuclides homogeneously distributed

* user can modify



Screening Phase Calculations

Predictive (empirical) parameters Ratios concentration in organism to surrounding media CR Biv

Literature values available Many nuclides Plant to soil Aquatic species to water

Allows back-calculation of media concentration corresponding to limiting internal dose



Selecting Target Organisms Dose standard

aquatic animals terrestrial plants terrestrial animals

Anything left out?



Screening Method Example - Plant Utilizes lumped parameter, Biv

Derives limiting soil value

Allows modification of screening limit where data on Biv available

isoilextiiniiv

planti

DCFDCFB

kgBqS

ps ,,,,

1

,

01.0

)(



Site Specific Screen (Fail Initial Screen) Step 1

lumped parameters too restrictive Examine and modify Bivs using general literature

Step 2 No literature values available or no benefit Begin more detailed analysis

Step 3 Secondary method Choose kinetic/allometric approach Consider site-specific parameters Re-visit estimate of internal tissue concentration Account for finite contamination Point of departure - lumped parameter values



Analysis Phase: Areas of Modification

inhalationingestion

external

Internalpathways are reexaminedfirst



Kinetic Approach, Internal Exposure

Input Rate Loss RateBody

Burden

ee TimExposureConstantRateLoss

RateLoss

RateInputBurdenBody 1



Body Burden Estimates

time

q

Function of: Body mass Intake rate Loss rate Exposure time

Need to address: varying mass intake exposure period



Useful Relationships Allometric Relationships

Y = X

Cross species relationships Empirically obtained Derived from energy/nutrient transport limitations

Mass and Metabolic Rate M3/4 (Ingestion, Inhalation) M1/4 (Life-span) aMx (biological elimination rate)

Mass and Home Range M~3/4 (Defining exposure areas)



Combining Kinetic & Allometric Methods

Allows prediction of body burden for any body mass lifespan loss rate

Can be tailored to specific species Stochastic analysis used to ground truth

approach and compare to “lumped” parameters



Pathways Included in Allometric Method

Riparian Animal TerrestrialAnimal

WaterPath

External External

Ingestion (water,food)

Ingestion (water)

Sediment External ---------Ingestion

Soil -------- ExternalIngestion (soil,food)Inhalation (soil)



Allometric & Kinetic Approach

isoilext

eff

iin

animallterrestriai

DCFWk

DCF

kgBqS

,,

,

1

,

001.0

)(

30.002.1

76.0

1

75.0

1

481.0

70

Wk

iv

effe

WMIT

PT

ffBWdc

a



Method Assessment Graded Approach provides for consistency

between screening and analysis phase Allometric predictions compared to real data

Uncertainty analysis (90th percentile?) Sensitivity Analysis

Initial results look very promising Additional analysis continuing



Input Parameter ValuesAssumption: Ratio of active to basal metabolic rate Cell: B7

Normal distribution with parameters:Mean 2.00Standard Dev. 0.20

Selected range is from 0.50 to 3.00Mean value in simulation was 2.00

Assumption: Fraction of energy ingested that is assimilated Cell: B8



Assumption: Caloric value of food Cell: B9



1.40 1.70 2.00 2.30 2.60

Ratio of activ e to basal metabolic rate

0.05 0.35 0.65 0.95 1.25

Fraction of energy ingested that is assi

2.00 3.50 5.00 6.50 8.00

Calor ic v alue of food

75.070Wdc

ar



Output Distributions



Electronic Spreadsheets Encodes Method

Microsoft Excel®

Visual Basic®

Undergoing Review















Riparian worksheet continued



Riparian, continued







Terrestrial Animals, continued



Terrestrial Animals, continued



Ongoing Issues

Multi-component retention functions Additional Nuclides Technical Accuracy Chain-Decay Nuclides (equilibrium fraction = 1) Internal Dose Factors

Radiation weighting factor for - emitters

Adjustment Factors size of contaminated zone & organism home range subsurface contamination



Comparisons - Sediment

A comparison of sediment BCGs

1.E+00

1.E+02

1.E+04

1.E+06

1.E+08

1.E+10

Am-241

Ce-144

Cs-135

Cs-137

Co-60

Eu-154

Eu-155

H-3I-129

I-131Pu-239

Ra-226

Ra-228

Sb-125

Sr-90Tc-99

Th-232

U-233

U-234

U-235

U-238

Zn-65

Zr-95

Nuclides

BC

G(B

q/k

g)

ORNL Sediment Benchmarks BDAC sediment BCGs



Comparisons - SoilA comparison of soil BCGs

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

Am-241

Ce-144

Cs-135

Cs-137

Co-60

Eu-154

Eu-155

H-3I-129

I-131Pu-239

Ra-226

Ra-228

Sb-125

Sr-90Tc-99

Th-232

U-233

U-234

U-235

U-238

Zn-65

Zr-95

Nuclides

BC

G(B

q/k

g)

RESRAD 15 mrem soil BDAC soil BCGs



Comparisons - Water

A comparison of water BCGs

1.E+00

1.E+02

1.E+04

1.E+06

1.E+08

1.E+10

Am-241

Ce-144

Cs-135

Cs-137

Co-60

Eu-154

Eu-155

H-3I-129

I-131Pu-239

Ra-226

Ra-228

Sb-125

Sr-90Tc-99

Th-232

U-233

U-234

U-235

U-238

Zn-65

Zr-95

Nuclides

BC

G(B

q/k

g)

DOE 5400l NRC Reg Guide DOE water BCGs



Summary & Conclusions Method undergoing QA/QC checks

reality check on lumped parameters

Additional refinement expected: data printouts more logical progression

One-year trial application



For further information Contact (in lieu of S. Domotor)

Kathryn Higley

[email protected]

541-737- 0675

Department of Nuclear Engineering


Corvallis OR 97331-5902

Documents

College of Engineering Oregon State University DOE’s Graded Approach for Evaluating Radiation Doses to Biota: Derivation of Screening and Analysis Methodologies