RESRAD-OFFSITE Code and
Derivation of Cleanup Criteria
Presented at EMRAS II NORM & Legacy Sites WG Meeting
Charley Yu, PhD, CHP
RESRAD Program Manager
Environmental Science Division
January 27, 2010
RESRAD Development Timeline
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RESRAD Family of Codes
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EXPOSURE PATHWAYS CONSIDERED IN RESRAD
(Subsistence Farming Scenario)
Plant
Foods
Milk
Meat
Dust,
Radon
Soil
Ingestion
Infiltration
External
Radioactively Contaminated Material in Soil
Leaching
Groundwater
Drinking
Water
Fish
Surface
Water
EXPOSURE PATHWAYS CONSIDERED IN RESRAD
(Industrial Use Scenario)
Dust,
Radon
Drinking
Water
Soil
Ingestion
Infiltration
External
Radioactively Contaminated Material in Soil
Leaching
Groundwater
Surface
Water
RESRAD PATHWAYS
Pathway Analysis - nine environmental pathways
• Direct Exposure
• Inhalation
• Ingestion of plant
foods
• Ingestion of meat
• Ingestion of milk
• Ingestion of aquatic
foods
• Ingestion of water
• Ingestion of soil
• Radon
SINGLE RADIONUCLIDE GUIDELINE
• RESRAD calculates homogeneous soil
guidelines (DCGL’s) for each radionuclide
specified by the user for the applicable
exposure pathways
• Guidelines are concentrations of radionuclides
in soil for which the basic dose limit will not
be exceeded over the selected time horizon
(usually 1000 years following remedial action)
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RADIOLOGICAL RELEASE CRITERIA
• HE (t) < HEL
• HE (t) = dose from all pathways (mSv/year)
• HEL= basic dose limit
= 0.25 mSv/year
SINGLE RADIONUCLIDE GUIDELINE
• Gi
• Gi (t)
= minimum Gi (t) for t < 1000 years
=
H EL
DSR i ( t )
• DSRi (t) =  DSR ip ( t )
p
= dose/source concentration ratio for
radionuclide i at time t (mSv/year
per Bq/g)
DOSE CONVERSION FACTORS
• External exposure pathway:
- infinite depth volume factors (mrem/yr per pCi/g)
• Inhalation pathway:
- inhalation factors
• Ingestion pathways
- ingestion factors
References: External DCFs - Federal Guidance Report No.12 (1993)
Inhalation/Ingestion DCFs - FGR No.11 (1988)
SLOPE FACTORS USED IN RESRAD
• Units of Sfj,p:
For external radiation -- risk/yr per pCi/g
For inhalation and ingestion pathways-- risk/pCi
• Source of Sfj,p:
EPA publications -- HEAST (2001)
Federal Guidance Report # 13 (1999)
• Morbidity
• Mortality
Note: Values of Sfj,p include contributions from associate
decay products with half-lives < cutoff, which are assumed
to be in equilibrium with their parent principal radionuclide.
ANALYSIS OF MULTIPLE SCENARIOS
• Current use and plausible future use scenarios can
be easily simulated
• One or more exposure pathways may be added or
suppressed
• Occupancy factors and consumption parameters
may be tailored according to the scenario being
simulated
• Typical exposure scenarios include industrial,
recreational, residential, and subsistence farming
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WATER PATHWAY MODELS
• Leaching model: sorption-desorption ion
exchange
-
Input of distribution coefficient (Kd)
Input of groundwater concentration
Input of solubility limit
Input of leach rate
Correlation of Kd with soil-plant transfer factors
• Independent transport of daughter
radionuclides
• Radionuclide transport models:
Nondispersive flow or mass balance
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SPECIAL MODEL FOR RADON
• Radionuclides:
- radon-222 and progeny
- radon-220 (thoron) and progeny
• Multimedia radon transport:
- soil
- water
- building materials
• Ingrowth from parents:
- Uranium and thorium series
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RESRAD PARAMETER DATABASE
• Decay and ingrowth data
• Dose conversion factors
• Cancer slope factors
• Food transfer factors (plant/soil, meat/feed,
milk/feed, fish/water)
• All 838 radionuclides contained in ICRP-38
are in RESRAD database (New DECDATA
>1200 radionuclides are being included)
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SITE SPECIFIC INPUT PARAMETERS
• Physical parameters (size, depth, density, porosity,
diffusion coefficient)
• Hydrological parameters (hydraulic conductivity,
gradient, soil b parameter, water table depth)
• Geochemical parameters (distribution coefficient,
leach rate, solubility)
• Meteorological parameters (precipitation,
evapotranspiration, erosion, runoff, mass loading
• Usage and consumption parameters (inhalation,
irrigation, ingestion, occupancy)
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PROBABILISTIC RESRAD Codes
Developed probabilistic modules for RESRAD
(onsite) (6.0), RESRAD-BUILD (3.0), and
RESRAD-OFFSITE (2.0)
• Identified key parameters and compiled parameter
distribution data for probabilistic analysis
• Developed integrated RESRAD codes to perform
probabilistic dose assessment for site-specific
analysis
• Developed postprocessor to analyze and display
probabilistic results
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PROBABILISTC vs. DETERMINISTIC ANALYSIS
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COMPILATION OF PARAMETER DISTRIBUTIONS WAS A
MAJOR EFFORT
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0.08
L ognormal D istribution
18
16
F req uen cy
14
U nde rlying  = 2.296
U nde rlying  = 1.276
0.07
L ow e r L imit = 0.18
0.06
U ppe r L imit = 320
0.05
12
10
0.04 f(x)
8
0.03
Fre que ncy
6
f(x)
0.02
4
0.01
2
0
0
0
10
20
30
40
50
60
70
80
90
100
110
120
T h ic kn e ss o f U n sa tu ra te d Zo n e (m )
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Derivation of Site-specific
Cleanup Criteria
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Procedures to Determine & Apply Site-Specific Guidelines
 Determine exposure scenario(s)
 Determine exposure pathway(s)
 Gather data
 Understand calculations
 Calculate guidelines
 Set cleanup criteria for the site
 Cleanup
 Postremediation dose assessment
Use RESRAD Family of Codes
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EXPOSURE SCENARIOS
Exposure scenarios may be classified as:
• Expected
• Plausible
• Unlikely
Typical exposure scenarios:
• Industrial use
• On-site resident (variations: suburban or
subsistence farmer)
• Recreational use
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NATURAL URANIUM CLEANUP CRITERIA CONSIDERATION
DSR U  nat  wU  234  DSR U  234   wU  235  DSR U  235 
 wU  238  DSR U  238 
GU  nat  HEL / DSR U  nat
The activity-based weighting factors for natural
uranium (wU-23*) are:
wU-234 = 1/2.046 = 0.489
wU-235 = 0.046/2.046 = 0.0225
wU-238 = 1/2.046 = 0.489
RESIDUAL RADIOACTIVE MATERIAL GUIDELINES FOR THE
ELZA GATE SITE
Guideline (pCi/g)*
Radionuclide
Scen. A
Scen. B
Uranium-234
Uranium-235
Uranium-238
Uranium-Tot
2400
450
1600
1800
5400
1100
3600
4000
Scen. C
590
150
430
470
Scen. D
120
47
120
120
A = Industrial-use scenario (current use)
B = Recreationist
C = Residential-use scenario (pond water)
D = Residential-use scenario (well water)
Guideline set by DOE: 70 pCi/g (2590 Bq/kg) Total Uranium
* Based on dose limit of 1 mSv/yr
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Application of DOE’s ALARA Policy
Uranium Cleanup Guidelines at Elza Gate
Volume (CY)
50000
40000
30000
20000
10000
0
5
25
35
50
100
U-238 Cleanup Guidelines (pCi/g)
Note: volume estimate based on DOE’s residual contamination
guidelines for Ra-226, Th-230, Th-232, and a variable U-238 guideline.
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Derivation of Soil Guidelines (DCGLs)
Plant
Foods
Dose Limit/
Constraint
(100 / 25
mrem/yr)
Milk
Meat
Dust
Soil
Ingestion
Radioactively Contaminated Material in Soil
External
Leaching
Groundwater
Drinking
Water
Single
Radionuclide
DCGLs
Fish
Surface
Water
Operational
DCGLs
R

r 1
Cr
DCGL
1
r
Sum of Ratios
Regulations
Pathway Analysis
Field Implementation
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POSTREMEDIATION DOSE ASSESSMENT FOR THE ELZA
GATE SITE
Average Radionuclide Concentrations:
4.9 pCi/g U-238 (measured)
4.9 pCi/g U-234, 0.22 pCi/g U-235 (derived)
Dose Rate
(mrem/yr)
Scen. A
Scen. B
Scen. C
Scen. D
1.5
0.66
12
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A = Industrial-use scenario (current use)
B = Recreationist
C = Residential-use scenario (pond water)
D = Residential-use scenario (well water)
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Summary
• RESRAD has been in existence for more than 20 years
• RESRAD is the most extensively tested, benchmarked, verified, and
validated code in the environmental risk assessment and site cleanup field
• RESRAD has been widely used by federal and state agencies and their
contractors
• Over 100 training workshops have been sponsored by DOE, NRC, EPA,
DOD, and state agencies
• Many universities have used RESRAD as a teaching and research tool
• Many papers and theses have been published based on RESRAD (some in
foreign languages)
• RESRAD has been widely used nationally and internationally.
• Comprehensive supporting documents are available for the application of
RESRAD
• RESRAD is continuously maintained and improved
• RESRAD can be downloaded free of charge
Thank You!
RESRAD Web Site:
http://www.evs.anl.gov/resrad
Email: [email protected]
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