ML022550613
| ML022550613 | |
| Person / Time | |
|---|---|
| Site: | Saxton File:GPU Nuclear icon.png |
| Issue date: | 07/31/2002 |
| From: | Saxton Nuclear Experimental Corp |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML022550613 (19) | |
Text
License Termination Plan Dose Modeling Issues Meeting Saxton Nuclear Experimental Corporation (SNEC)
Rockville, MD July 31, 2002
Dose Modeling Issues
"* Radionuclide reduction
"* Dose modeling logic
"° Parameter justification
"* Subsurface regions
"* Dilution factor
"° Exposure pathways
"* DCGLs
Radionuclide Reduction
- SNEC Calculation E9000-01-030
-Eleven nuclides identified
- Seven nuclides deselected
- Based on <1% of the mix and <10% of
- Totaling 3.45% or 0.86 mrem of the 25 the dose mrem limit
- This dose will be accounted for during the FSS survey planning phase
Radionuclide Reduction SNEC Radionuclide List H-3 Eu-152 C-14 Pu-238 Co-60 Pu-239 Ni-63 Pu-241 Sr-90 Am-241 Cs-137
Dose Modeling Logic
- Used RESRAD 6.1
- Probability used for Sensitivity Analyses
-Deterministic used to calculate the DCGLs
Parameter Justification
- Selected based on our previous meeting
- DandD Metabolic and Behavioral (M/B) default parameters used
-Parameter justification will be described in Chapter 6 of the LTP
Start Select nuclide Create RESRAD input file with distribution from H&A, D&D and RESRAD defaults Create NRC-directed correlations between input parameters Execute RESRAD In Probabilistic Mode Examine MC summary report Is correlation higher no Examine PCC than PCC for first 6 sensitivities ExaminesPC Examine PRCC sensitivities I-=
Identify those input parameters for which:
I Sensitivity Coefficienti
>0.25 from 6 tables Print sensitive variables for calc.
package Begin to rerun RESRAD-Default case in probabilistic mode with only sensitive parameters varying iImport LHSBIN.DAT table into Excel and identify means, 25% and 75% values for sensitive parameter distributions Print mean s
25, 75 values for caic. package
Edit RESRAD input file to include 25% value as bas e-deterministic input for each sensitive parameter that is negatively correlated (sens.parameter -e-0.25)
SEdit RESRAD file to Include 75%
value as base-deterministic value input for each sensitive parameter that is positively correlated (>0.25)
Replace base-deterministic value]
for sensitive parameters with statistical mean value for those parameters for which mean is not bounded by 0.25 & 0.75 %
~Replace S/
I base-deterministic V
I KD with 75% sample no statistic value Replace base-deterministic KD with lowest Argonne value
Suspend RESRAD probabilistic assessment Execute nuclidelsite-specific file In deterministic mode Print peak dose/year/pathway summary for calc. package Calculate DCGL based on 25 mrem/yr Calculate DCGL based on 4 mrem/yr limit Print DCGL for calc. package
Approach Conservatisms
- 4 mrem per yea
° Including subsu S
r drinking water rface excavation scenario Lowest Kd value
- By using 25 &75 versus the mean
Modeling Assumptions
"* Fill
"* Overburden
"* Bedrock
Subsurface Modeling
- Broken into three regions and seven pathways
- Bedrock
- Drinking water only
- SSGS backfill
"* All pathways
"* Drinking water (Excavated I undisturbed)
- Spray pond (overburden)
"* All pathways
"* Drinking water (Excavated / undisturbed)
Excavation Scenario Mixed fill &
overburden from excavation
_A_
Mixed fill & rubble from excavation
-:4:-
SSGS Basement Spray Ponds
& Most of the SNEC Site 1+/-
Dilution Factor
° 50 % dilution based on:
NRC 1986 "Update of Part 61 Impacts Analysis Methodology" NRC 1999 "Preliminary Guidelines for Evaluating Dose Assessment in Support of Decommissioning"
Exposure Pathways Atmospheric Transport
DCGLs
Proposed DCGLs K
Proposed Composite NRC screening DCGL's DCGL's (pCilg)
SJuly-02
-May-99 25 mrem/y Limit APu-241 2.3*r2.31 C-14 5.4*
12 Co-60
- 3. 5
- 3. 8 Cs-37
- 6. 6 11 Eu-1 52
- 10. 1
- 8. 7 H331.
1" 110 Ni-63 747 2100 Pu-238 0.42' 2.5 Pu-239 0.37*"
2.3 Pu-241 19.88*
72 Sr-90
- 0. 61" 1.7
- Based on the 4 mrem limit.
Next Steps
"* NRC feedback
"* Next meeting dates