ML25345A138
| ML25345A138 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 12/11/2025 |
| From: | Holtec Decommissioning International, Radiation Safety & Control Services |
| To: | Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML25345A092 | List:
|
| References | |
| HDI 25-039 24-085, Rev 0 | |
| Download: ML25345A138 (0) | |
Text
RSCS Technical Support Document No.24-085 Rev 0 Probabilistic Dose Comparisons: Building Occupancy Scenario Vs. Room Renovation Scenario Prepared by:
Joseph Bisson, Technical Consultant Reviewed by:
Christopher Messier, Sr. Director of Engineering and Business Strategy Calculations Reviewed by:
Christopher Messier, Sr. Director of Engineering and Business Strategy Approved by:
Eric Darois, Executive Director Radiation Safety & Control Services, Inc 93 Ledge Road Seabrook, NH 03874 1-800-525-8339 www.radsafety.com September 17, 2024 RSCS Radiation Safety & Control Services
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 2 Table of Contents 1
Introduction............................................................................................................................ 3 2
Background............................................................................................................................ 3 2.1 Radionuclide Input........................................................................................................... 3 3
Assumptions.......................................................................................................................... 4 4
Calculations........................................................................................................................... 5 5
Results................................................................................................................................... 9 6
Conclusions......................................................................................................................... 10 7
References.......................................................................................................................... 11 List of Tables Table 1 - Radionuclide Input for RESRAD-Build.......................................................................... 3 Table 2 - Centers of the Sources.................................................................................................. 5 Table 3 - Renovation Scenario: Values for RESRAD-Build Parameters...................................... 5 Table 4 - Comparison of Doses from the Renovation Scenario and Occupancy Scenario.......... 9 Table 5 - Comparison of Probabilistic Doses from RESRAD-Build 4.0 for Selected Radionuclides............................................................................................................................. 10
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 3 1 Introduction This calculation uses the RESRAD-Build code (version 4.0) to identify risk-sensitive input parameters and estimate annual doses under the room renovation scenario. The results from these RESRAD-Build executions will be compared to the probabilistic results for the building occupancy scenario obtained using RESRAD-Build 3.5 for the Oyster Creek Nuclear Generating Station (OCNGS) documented in ENG-OCS-002 [1].
The modeling of these two exposure scenarios does not include site-specific input, allowing the results of the comparison for the two scenarios to be applied to other nuclear power plant sites.
2 Background
The exposure scenario modeled in this calculation is the room renovation scenario, which provides estimates of human radiation exposures resulting from renovation activities in a room containing residual radioactivity. The critical receptor under this scenario is a hypothetical worker assumed to perform renovation activities inside a room for a 3-month period (the duration of a renovation project given in NUREG/CR-5512 [2]). Consistent with the renovation scenario description in NUREG/CR-5512, the worker is assumed to be involved in only 1 renovation project during the year.
The exposure pathways considered are the same as those considered for the building occupancy scenario:
direct external exposure from the source (i.e., radioactive material deposited on the floor, walls, and ceiling),
external exposure from deposited material, external exposure due to air submersion, exposure due to inhalation of airborne radioactive material, and ingestion of radioactive material directly from the sources and material deposited on the surfaces.
Input parameters were treated as either deterministic (a single value is assigned) or stochastic (a probability distribution is assigned). Except for the parameters that model the room renovation scenario, input for RESRAD-Build parameters was the same as that used in the probabilistic analysis for the building occupancy scenario. This supported an easy comparison of results.
Details for the treatment and sources of input are provided in ENG-OCS-002.
2.1 Radionuclide Input RESRAD-Build parameter probabilistic analysis was performed for radionuclides listed in Table 1, which have been identified as potential contaminants for the OCNGS site [3].
Table 1 - Radionuclide Input for RESRAD-Build Radionuclide Progenya Radionuclide Progenya Am-241 Np-237, Th-229, U-233 Nb-94 C-14 Ni-63 Cm-243 Ac-227, Pa-231, Pu-239, U-235 Np-237 Th-229, U-233
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 4 Radionuclide Progenya Radionuclide Progenya Cm-244 Pu-240, Ra-228, Th-228, Th-232, U-236 Pu238 Pb-210, Po-210, Ra-226, Th-230, U-234 Cs-137 Pu-239 Ac-227, Pa-231, U-235 Co-60 Pu-240 Ra-228, Th-228, Th-232, U-236 Eu-152 Gd-152 Pu-241 Am-241, Np-237, Th-229, U-233 Eu-154 Sb-125 Te-125m Fe-55 Sr-90 H-3 Tc-99 Mn-54 aProgeny radionuclides are automatically included with input of parent radionuclide.
3 Assumptions The hypothetical worker performs renovation activities inside a room containing residual radioactivity for 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> per week over a 13-week (3-month) period during the year of exposure.
This assumption is more conservative than the 40-hour per week schedule cited for the renovation scenario in NUREG/CR-5512. Consistent with the scenario description in NUREG/CR-5512, the worker is assumed to perform one renovation project within the exposure year and receive radiation exposure only while performing the renovation activities.
The room under renovation is assumed an 8m-by-8m room with 3m walls, as defined in NUREG/CR-5512 and NUREG/CR-6755 [4]. This room size is the same as that assumed for the OCNGS building occupancy scenario and supports an easy comparison of results for the 2 scenarios. The ratios between the calculated doses for the two scenarios are expected to be approximately the same for any alternative room size.
The contaminated room includes 6 area sources: the floor, 4 walls, and the ceiling. Uniform surface contamination is assumed for each area source.
Statistical distributions from NUREG/CR-7267 [5] and NUREG/CR-6755 are assumed as input for:
deposition velocity, air exchange rate for room, re-suspension rate, indirect ingestion rate, and time for source removal.
The air release fraction for H-3 is assumed equal to 1.0. The distribution for the air release fraction from NUREG/CR-7267 is used as input for all other radionuclides.
The removable fraction is assumed equal to 0.1, consistent with the assumption made for the OCNGS building occupancy scenario.
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 5 4 Calculations Indoor Fraction: The total exposure duration is equal to 365.25 days. During that exposure period the worker receives a dose only during the fraction of the year that is spent inside the room. The indoor fraction calculated for the assumed work schedule (50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> per week) and project duration (13 weeks) is:
(50h/w)(13w/y)(1y/365.25d)(1d/24h) = 0.074.
Inhalation Rate: A gardening breathing rate equal to 1.7 m3/h is listed in Table I-11 in NUREG-1757 [6] is used to calculate input for the inhalation rate in units of m3/d. That breathing rate was selected to increase conservatism in the input for inhalation rate because it is significantly greater than the breathing rate (1.2 m3/h) listed for the renovation scenario value renovation scenario.
Input for inhalation rate is:
(1.7 m3/h)(24 h/d) = 40.8 m3/d.
Using the dimensions for the assumed room, the locations of the centers of the sources were determined as the mid-point on the X, Y, and Z-axes.
Table 2 - Centers of the Sources Source No.
Source Description Location of Center of Source (m)
X-axis Y-axis Z-axis 1
Floor 4
4 0
2 Wall 1 4
0 1.5 3
Wall 2 0
4 1.5 4
Wall 3 4
8 1.5 5
Wall 4 8
4 1.5 6
Ceiling 4
4 3
Input values for all other RESRAD-Build parameters are either deterministic input from NUREG/CR-5512 and NUREG/CR-6755 or parameter distributions from NUREG/CR-7267 and NUREG/CR-6755. Table 3 summarizes the input values for all the RESRAD-Build parameters.
Table 3 - Renovation Scenario: Values for RESRAD-Build Parameters RESRAD-BUILD Input Parameter Values for Sensitivity Analysis Room Renovation Scenario Parameter Treatment Value or Distribution Value/Distribution Reference Source Distribution's Statistical Parametersa 1
2 3
4 Exposure Duration (d)
D 365.25 NUREG/CR-5512 Indoor Fraction D
0.074 Based on 50 h/w for 13 weeks Evaluation Time (y)
D 1 or multiple (e.g., 1, 5, 10)
T=1 corresponds to dose over the 1st year Number of Rooms D
1 one contaminated room
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 6 RESRAD-BUILD Input Parameter Values for Sensitivity Analysis Room Renovation Scenario Parameter Treatment Value or Distribution Value/Distribution Reference Source Distribution's Statistical Parametersa 1
2 3
4 Deposition Velocity (m/s)
S Loguniform NUREG/CR-6755, NUREG/CR-7267 2.7E-06 2.7E-03 Resuspension Rate (s-1)
S Loguniform NUREG/CR-6755, NUREG/CR-7267 2.5E-11 1.3E-5 Air Exchange Rate for Room (h-
- 1)
S Truncated Lognormal NUREG/CR-6755 0.4187 0.88 0.001 0.999 Room Area (m2)
D 64 NUREG/CR-6755 Room Height (m)
D 3
NUREG/CR-6755 Time Fraction D
1 NUREG/CR-7267 Inhalation Rate (m3/d)
D 40.8 Based on 1.7 m3/h (NUREG-1757 Table I-11)
Indirect Ingestion Rate (m2/h)
S Loguniform NUREG/CR-6755, NUREG/CR-7267 2.8E-5 2.9E-4 Receptor Location x, y, z (m)
D 4, 4, 1 Center of room floor Shielding Thickness (cm)
D 0
No shielding of sources Shielding Density (g/cm3)
D 1
Input value required for code execution - no impact due to shielding thickness input Shielding Material D
Water Input value required for code execution - no impact due to shielding thickness input Number of Sources D
6 Floor, ceiling, and 4 walls External Dose Conversion Factor, (mrem/y per pCi/cm2)
D RESRAD-Build Dose Conversion Factor Library Values were from Federal Guidance Report No.12 (FGR-12).
Air Submersion Dose Conversion Factor, (mrem/y per pCi/m3)
D RESRAD-Build Dose Conversion Factor Library Values were from Federal Guidance Report No.12 (FGR-12).
Inhalation Dose Conversion Factor, (mrem/pCi)
D RESRAD-Build Dose Conversion Factor Library Values were from Federal Guidance Report No.11 (FGR-11).
Ingestion Dose Conversion Factor, (mrem/pCi)
D RESRAD-Build Dose Conversion Factor Library Values were from Federal Guidance Report No.11 (FGR-11).
Source 1: Floor Type D
area NUREG/CR-5512 Direction D
Z NUREG/CR-5512 Location of Center of Source:
x,y,z (m)
D 4, 4, 0 Center of floor Geometry D
Rectangular shape Based on length and width Source length X-axis (m)
D 8
Based on room area
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 7 RESRAD-BUILD Input Parameter Values for Sensitivity Analysis Room Renovation Scenario Parameter Treatment Value or Distribution Value/Distribution Reference Source Distribution's Statistical Parametersa 1
2 3
4 Source length Y-axis (m)
D 8
Based on room area Air Release Fraction for H-3 D
1.0 NUREG/CR-7267 Air Release Fraction (all nuclides other than H-3)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1E-06 1.0 0.07 Direct Ingestion (h-1)
D 4.91E-7 NUREG/CR-6755 Removable Fraction D
0.1 NUREG/CR-5512 Time for Source Removal (d)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1,000 100,000 10,000 Radionuclide Concentration (pCi/m2)
D 1.0 ROCs identified for the OCNGS site Source 2: Wall 1 Type D
Area NUREG/CR-5512 Direction D
Y NUREG/CR-5512 Location of Center of Source:
x,y,z (m)
D 4, 0, 1.5 Center of wall Geometry D
Rectangular shape Based on length and width Source length X-axis (m)
D 8
Based on room area Source length Z-axis (m)
D 3
Based on wall height Air Release Fraction for H-3 D
1.0 NUREG/CR-7267 Air Release Fraction (all nuclides other than H-3)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1E-06 1.0 0.07 Direct Ingestion (h-1)
D 4.91E-7 NUREG/CR-6755 Removable Fraction D
0.1 NUREG/CR-6755 Time for Source Removal (d)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1,000 100,000 10,000 Radionuclide Concentration (pCi/m2)
D 1.0 ROCs identified for the OCNGS site Source 3: Wall 2 Type D
Area NUREG/CR-5512 Direction D
X NUREG/CR-5512 Location of Center of Source:
x,y,z (m)
D 0, 4, 1.5 center of wall Geometry D
Rectangular shape Based on length and width Source length Y-axis (m)
D 8
Based on area Source length Z-axis (m)
D 3
Based on wall height Air Release Fraction for H-3 D
1.0 NUREG/CR-7267 Air Release Fraction (all nuclides other than H-3)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1E-06 1.0 0.07 Direct Ingestion (h-1)
D 4.91E-7 NUREG/CR-6755 Removable Fraction D
0.1 NUREG/CR-6755 Time for Source Removal (d)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1,000 100,000 10,000 Radionuclide Concentration (pCi/m2)
D 1.0 ROCs identified for OCNGS site
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 8 RESRAD-BUILD Input Parameter Values for Sensitivity Analysis Room Renovation Scenario Parameter Treatment Value or Distribution Value/Distribution Reference Source Distribution's Statistical Parametersa 1
2 3
4 Source 4: Wall 3 Type D
Area NUREG/CR-5512 Direction D
Y NUREG/CR-5512 Location of Center of Source:
x,y,z (m)
D 4, 8, 1.5 center of wall Geometry D
Rectangular shape Based on length and width Source length X-axis (m)
D 8
Based on room area Source length Z-axis (m)
D 3
Based on wall height Air Release Fraction for H-3 D
1.0 NUREG/CR-7267 Air Release Fraction (all nuclides other than H-3)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1E-06 1.0 0.07 Direct Ingestion (h-1)
D 4.91E-7 NUREG/CR-6755 Removable Fraction D
0.1 NUREG/CR-6755 Time for Source Removal (d)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1,000 100,000 10,000 Radionuclide Concentration (pCi/m2)
D 1.0 ROCs identified for the OCNGS site Source 5: Wall 4 Type D
Area NUREG/CR-5512 Direction D
X NUREG/CR-5512 Location of Center of Source:
x,y,z (m)
D 8, 4, 1.5 center of wall Geometry D
Rectangular shape Based on length and width Source length Y-axis (m)
D 8
Based on room area Source length Z-axis (m)
D 3
Based on wall height Air Release Fraction for H-3 D
1.0 NUREG/CR-7267 Air Release Fraction (all nuclides other than H-3)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1E-06 1.0 0.07 Direct Ingestion (h-1)
D 4.91E-7 NUREG/CR-6755 Removable Fraction D
0.1 NUREG/CR-6755 Time for Source Removal (d)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1,000 100,000 10,000 Radionuclide Concentration (pCi/m2)
D 1.0 ROCs identified for the OCNGS site Source 6: Ceiling Type D
Area NUREG/CR-5512 Direction D
Z NUREG/CR-5512 Location of Center of Source:
x,y,z (m)
D 4, 4, 3 center of ceiling Geometry D
Rectangular shape Based on length and width Source length X-axis (m)
D 8
Based on room area Source length Y-axis (m)
D 8
Based on room area Air Release Fraction for H-3 D
1.0 NUREG/CR-7267
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 9 RESRAD-BUILD Input Parameter Values for Sensitivity Analysis Room Renovation Scenario Parameter Treatment Value or Distribution Value/Distribution Reference Source Distribution's Statistical Parametersa 1
2 3
4 Air Release Fraction (all nuclides other than H-3)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1E-06 1.0 0.07 Direct Ingestion (h-1)
D 4.91E-7 NUREG/CR-6755 Removable Fraction D
0.1 NUREG/CR-5512, NUREG/CR-6755 Time for Source Removal (d)
S Triangular NUREG/CR-6755, NUREG/CR-7267 1,000 100,000 10,000 Radionuclide Concentration (pCi/m2)
D 1.0 ROCs identified for the OCNGS site Table 3 notes:
a Distribution Statistical Parameters:
Loguniform: 1= minimum, 2 = maximum Truncated lognormal-n: 1= mean, 2 = standard deviation, 3 = lower quantile, 4 = upper quantile Triangular: 1 = minimum, 2 = maximum, 3 = most likely Input Rank Correlation Coefficients:
Resuspension Rate and Deposition Velocity = 0.9 Time for source removal (correlation set between sources) = 0.9 5 Results The highest probabilistic dose for each radionuclide in the room renovation scenario (determined using RESRAD-Build 4.0) was compared to the highest probabilistic dose in the building occupancy scenario (determined using RESRAD-Build 3.5). The results of the comparisons are shown in Table 4.
Table 4 - Comparison of Doses from the Renovation Scenario and Occupancy Scenario Radionuclide Probabilistic Dose (mrem/y) by Scenario Occupancy Renovation O:R Ratio Am-241 3.07E-03 1.17E-03 2.6 C-14 1.38E-07 1.54E-07 0.9 Cm-243 1.43E-03 7.79E-04 1.8 Cm-244 1.01E-03 6.16E-04 1.6 Co-60 3.71E-05 1.15E-05 3.2 Cs-137 1.27E-05 6.16E-06 2.1 Eu-152 2.08E-05 5.88E-06 3.5 Eu-154 2.13E-05 6.34E-06 3.4 Fe-55 1.72E-08 3.34E-08 0.5 H-3 2.37E-09 4.05E-10 5.9 Mn-54 4.63E-06 1.30E-06 3.6 Nb-94 3.50E-05 8.90E-06 3.9
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 10 Radionuclide Probabilistic Dose (mrem/y) by Scenario Occupancy Renovation O:R Ratio Ni-63 6.48E-08 5.35E-08 1.2 Np-237 3.91E-03 1.42E-03 2.8 Pu-238 2.34E-03 1.02E-03 2.3 Pu-239 3.10E-03 1.13E-03 2.7 Pu-240 3.09E-03 1.13E-03 2.7 Pu241 3.83E-05 2.29E-05 1.7 Sb-125 5.79E-06 1.71E-06 3.4 Sr-90 1.20E-05 1.32E-05 0.9 Tc-99 1.44E-07 1.22E-07 1.2 Except for C-14, Fe-55, and Sr-90, the room renovation doses were less than the OCNGS building occupancy doses. It is recognized that the ratios are based on probabilistic doses from 2 versions of RESRAD-Build, 3.5 and 4.0. The low (<1.0) ratios for C-14, Fe-55, and Sr-90 were investigated by recreating the OCNGS building occupancy scenario in RESRAD-Build 4.0. In addition, H-3, Cs-137, and Am-241 were included to evaluate the consistency of the difference between doses from the two scenarios. The results are provided in Table 5.
Table 5 - Comparison of Probabilistic Doses from RESRAD-Build 4.0 for Selected Radionuclides Radionuclide Probabilistic Dose (mrem/y) by Scenario Occupancy Renovation O:R Ratio C-14 5.45E-07 1.54E-07 3.5 Fe-55 1.12E-07 3.34E-08 3.4 Sr-90 4.17E-05 1.32E-05 3.2 H-3 1.23E-09 4.05E-10 3.0 Cs-137 2.21E-05 6.16E-06 3.6 Am-241 2.20E-03 1.17E-03 1.9 Cm-243 1.47E-03 7.79E-04 1.8 Pu-238 1.92E-03 1.02E-03 1.9 Pu-241 4.34E-05 2.29E-05 1.9 6 Conclusions Except for C-14, Fe-55, and Sr-90 results, the building occupancy scenario modeled with RESRAD-Build 3.5 produced higher annual doses than the room renovation scenario modeled with RESRAD-Build 4.0. The differences between the building occupancy doses and the room renovation doses observed in Table 4 reflect the combined difference between the 2 scenarios and RESRAD-Build versions 3.5 and 4.0.
Table 5 indicates that the doses are greater by a factor of approximately 2 or more for the building occupancy scenario than for the room renovation scenario when both scenarios are run on RESRAD-Build 4.0.
Probabilistic Dose Comparisons:
RSCS TSD 24-085 Building Occupancy Scenario Vs. Room Renovation Scenario Rev 0 Page 11 The modeling of the 2 scenarios did not include site-specific information allowing the application of results to other nuclear power sites.
7 References
- 1.
ENG-OCS-002, RESRAD-Build Input Parameter Sensitivity Analysis - OCS, May 2022
- 2.
NUREG/CR-5512, Residual Radioactive Contamination from Decommissioning, Volume 1: Technical Basis for Translating Contamination Levels to Annual Total Effective Dose Equivalent, October 1992
- 3.
Radionuclide Selection for DCGL Development - Oyster Creek Station Site Characterization Project, January 2022
- 4.
NUREG/CR-6755, Technical Basis for Calculating Radiation Doses for the Building Occupancy Scenario Using the Probabilistic RESRAD-Build 3.0 Code, February 2002
- 5.
NUREG/CR-7267, Default Parameter Values and Distribution in RESRAD-ONSITE V7.2, RESRAD-BUILD V3.5, and RESRAD-OFFSITE V4.0 Computer Codes, February 2020
- 6.
NUREG-1757, Volume 2, Consolidated Decommissioning Guidance: Characterization, Survey, and Determination of Radiological Criteria, July 2022