ML22235A703
| ML22235A703 | |
| Person / Time | |
|---|---|
| Site: | Nuclear Energy Institute |
| Issue date: | 08/24/2022 |
| From: | Nuclear Energy Institute |
| To: | Sean Meighan NRC/NRR/DRA/ARCB |
| Meighan S | |
| References | |
| Download: ML22235A703 (15) | |
Text
©2022 Nuclear Energy Institute
-Frankie Pimentel, Sr. Project Manager -
Engineering & Risk, NEI
-Greg Broadbent, Senior Staff Engineer -
Corporate Nuclear Analysis, Entergy
-Chad Burns, Sr. Fuels Engineer, Constellation Safety Analysis
-Brian L. Mount, Consulting Engineer, Nuclear Safety Analysis II, Dominion Energy August 24, 2022 Source Terms and Radiological Consequence Analyses
©2022 Nuclear Energy Institute 2
DG-1389 contains significant changes to BWR release fractions and timing
Doubling halogen releases can have wide-ranging impacts Charcoal/HEPA loadings and heat loads, EQ NEI Comment #4 suggests incorporating results from supporting analyses performed by staff
Many BWR plants may not be able to adopt Rev. 1 without significant licensing basis changes or plant modifications Example 1: demonstrates when applying the proposed release fractions and timing, plant will not meet the CR dose criteria for current BU and enrichment conditions Example 2: demonstrates applying credit for the condenser using the proposed methods in conjunction with the proposed release fractions and timing, plant will meet the CR dose criteria for current BU and enrichment conditions Example 3: demonstrates applying the proposed release fractions and timing to a plant already using credit for the condenser will not meet the CR dose criteria for current BU and enrichment conditions Source Terms and Radiological Consequence Analyses
©2022 Nuclear Energy Institute 3 Changes for BWR MHA-LOCA Scenario Gap In-Vessel Total Gap In-Vessel Total Noble Gases 5.00E-02 9.50E-01 1.00E+00 8.00E-03 9.60E-01 9.68E-01 Halogens 5.00E-02 2.50E-01 3.00E-01 3.00E-03 5.40E-01 5.43E-01 Alkali Metals 5.00E-02 2.00E-01 2.50E-01 3.00E-03 1.40E-01 1.43E-01 Tellurium Metals 0.00E+00 5.00E-02 5.00E-02 3.00E-03 3.90E-01 3.93E-01 Barium, Strontium 0.00E+00 2.00E-02 2.00E-02 0.00E+00 5.00E-03 5.00E-03 Noble Metals 0.00E+00 2.50E-03 2.50E-03 0.00E+00 2.70E-03 2.70E-03 Cerium 0.00E+00 5.00E-04 5.00E-04 0.00E+00 1.60E-07 1.60E-07 Lanthanides 0.00E+00 2.00E-04 2.00E-04 0.00E+00 2.00E-07 2.00E-07 Molybdenum 0.00E+00 0.00E+00 0.00E+00 0.00E+00 3.00E-02 3.00E-02 Reg Guide 1.183, Rev. 0 Draft Guide DG-1389 Nuclide Group Onset Duration Onset Duration Gap 2 min 30 min 2 min 0.16 hrs Early In-Vessel 30 min 1.5 hrs 0.16 hrs 8.0 hrs Table 4 of Reg Guide 1.183 Rev. 0 Table 5 of Draft Guide DG-1389 Release Phase BWR Release Fractions Nuclide Groups Release Timing Nuclide Group Table 5 of Reg Guide 1.183 Rev. 0 Table 14 of SAND 2011-0158 Noble Gases Xe, Kr Xe, Kr Halogens I, Br I, Br Alkali Metals Cs, Rb Cs, Rb Tellurium Metals Te, Sb, Se Te, Sb, Se Barium, Strontium Ba, Sr Ba, Sr Noble Metals Ru, Rh, Pd, Mo, Tc, Co Ru, Rh, Pd, Co Ceriums Ce, Pu, Np Ce, Pu, Np, Zr Lanthanides La, Zr, Nd, Eu,Nb, Pm, Pr, Sm, Y, Cm, Am La, Nd, Eu, Pm, Pr, Sm, Y, Cm, Am Molybdenum Mo, Tc, Nb
©2022 Nuclear Energy Institute 4 Example 1: BWR-6, Mark-III Containment BWR/6, Mark-III Containment Standard Leakage Paths MSIV leakage Containment leakage ESF liquid leakage into Secondary CMT Main Steam Credit No credit for MSL deposition past the outboard MSIV Credit for MSIV Leakage Control System initiation at 20 minutes 99% SGTS filters, ~1 hour holdup
©2022 Nuclear Energy Institute 5 Results from Proposed Reg Guide Changes 0
1 2
3 4
5 6
7 Reg Guide 1.183 Rev. 0 DG-1389 Control Room Dose (Rem TEDE)
Control Room Dose Other Alkali Metals Halogens Noble Gases 10CFR50.67 Acceptance Criterion Release Group Reg Guide 1.183 Rev. 0 DG-1389 Noble Gases 1.12E+00 1.42E+00 Halogens 2.30E+00 3.86E+00 Alkali Metals 4.46E-01 1.48E-01 Other 2.46E-01 3.97E-01 Total 4.11E+00 5.83E+00 Offsite Doses Control Room Doses 0
1 2
3 4
5 6
7 8
9 10 Exclusion Area Boundary Low Population Zone Dose (Rem TEDE)
Location Offsite Doses Reg Guide 1.183 Rev. 0 DG-1389 Dose Location Reg Guide 1.183 Rev. 0 DG-1389 9.71 9.55 (2-4 hrs)
(7.9-9.9 hrs)
Low Population Zone 6.20 8.00 Control Room 4.11 5.83 Exclusion Area Boundary
©2022 Nuclear Energy Institute 6 Results from Proposed Reg Guide Changes 0
0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0
1 2
3 4
5 6
7 8
9 Fraction of Core Inventory per Hour Hours BWR Halogen Release Rates Reg Guide 1.183 Rev. 0 DG-1389 0
1 2
3 4
5 6
7 8
9 10 0
2 4
6 8
Ending Time of 2-hour Window (Hours)
Exclusion Area Boundary Dose Reg Guide 1.183 Rev. 0 DG-1389 DG Release Rates Lower than Rev. 0 DG Release Rates Lower than Rev. 0 Extended-Release Duration leads to later EAB peak
©2022 Nuclear Energy Institute 7 Main Steam Credit 300 scfh total / 150 max individual line Credit for Aerosol Deposition between intact MSIVs, MSIV to TSV, and TSV through Condenser using RG 1.183 Table A-1 Addition of Condenser Removal Mechanisms Containment Elemental Iodine Plateout from Wetted Surface Containment Aerosol Deposition (Powers 10% model)
No Suppression Pool Scrubbing Leakage Paths MSIV leakage Containment leakage ESF Leakage Example 2: BWR-4, Mark-I Containment
©2022 Nuclear Energy Institute 8 MSIV Aerosol Changes Elemental Deposition - no change to MSL methods, no credit in condenser Example 2: BWR-4, Mark-I Containment Leak Path Removal Coefficient
[1/hr]
Leak Rate
[scfh]
Volume
[ft^3]
Effective Filter Efficiency
[%]
RG 1.183 Rev. 0
[AEB 98-03]
0-10 hr 10+hr 0-10 hr 10+hr 0-96 hr Intact inner MSIV to intact outer MSIV 1.8 1
150 66.05 44.2%
30.6%
93.8%
0.7 150 869.96 85.3%
80.2%
97.5%
Failed line outer MSIV to TSVs 1
0.7 150 869.96 85.3%
80.2%
97.5%
TSV to Condenser 0.015 0.012 300 300000 93.8%
92.3%
0%
©2022 Nuclear Energy Institute 9 No Condenser Strict reduction in deposition Unviable increase in CR dose Results from Proposed Reg Guide Changes Control Room LPZ EAB RG 1.183 R0 4.44E+00 2.59E+00 5.42E+00 RG 1.183 R1 5.16E+01 1.99E+01 1.11E+01 Delta 1061%
667%
105%
©2022 Nuclear Energy Institute 10 Results from Proposed Reg Guide Changes RG 1.183 Rev. 0 Control Room EAB LPZ Containment Leakage 2.61E-01 2.92E+00 3.14E+00 ESF Leakage 5.84E-02 6.74E-01 3.87E+00 MSIV Leakage 4.44E+00 5.42E+00 2.59E+00 Containment Shine 3.17E-02 0.00E+00 0.00E+00 External Cloud 1.30E-02 0.00E+00 0.00E+00 CR Filter Shine 3.15E-03 0.00E+00 0.00E+00 TOTAL 4.81E+00 9.01E+00 9.60E+00 RG 1.183 Rev. 1 Control Room EAB LPZ Containment Leakage 9.80E-02 1.42E+00 3.25E+00 ESF Leakage 3.05E-02 1.09E+00 5.95E+00 MSIV Leakage 2.89E+00 4.51E-01 4.76E-01 Containment Shine 3.17E-02 0.00E+00 0.00E+00 External Cloud 1.30E-02 0.00E+00 0.00E+00 CR Filter Shine 3.15E-03 0.00E+00 0.00E+00 TOTAL 3.07E+00 2.96E+00 9.68E+00 Results with condenser compartment added to Rev. 1 case
©2022 Nuclear Energy Institute 11 Results from Proposed Reg Guide Changes 0.00E+00 2.00E+00 4.00E+00 6.00E+00 8.00E+00 1.00E+01 1.20E+01 Control Room EAB LPZ REM TEDE Dose Location BWR/4, Mark 1 RG 1.183 Rev. 0 RG 1.183 Rev. 1 Results with condenser compartment added to Rev. 1 case
©2022 Nuclear Energy Institute 12 400 scfh total / 200 max individual line Currently credits condenser for aerosol & elemental I removal Current model is AEB 98-03 for deposition Table A-1 applied directly to compartments Example 3: BWR-5, Mark-II Containment
©2022 Nuclear Energy Institute 13 Results from Proposed Reg Guide Changes
Control Room resulting dose very high through failed line (MSL B)
Overall decrease in Iodine removal without compensation.
Control Room LPZ EAB MSIV A 3.20E+00 2.54E-02 6.18E-02 MSIV B 1.61E+01 5.61E-02 2.99E-01 ECCS 2.47E-02 1.73E-02 3.09E-02 Containment Leakage 5.12E-01 9.89E-02 6.96E-01 Total 1.98E+01 1.98E-01 1.09E+00
©2022 Nuclear Energy Institute 14 State-of-the-Art Reactor Consequence Analyses (SOARCA) project results1 include the suppression pool in their models and indicate that all modeled accident scenarios, progress more slowly and release smaller amounts of radioactive material than calculated in earlier studies
PWRs saw these expected impacts while BWRs did not Reg Guide should not unduly penalize BWRs Potential Resolutions
Update BWR release fractions with more applicable accident scenario selection
Consider suppression pool scrubbing credit in BWR release fractions NUREG/CR-6153 provides one scrubbing model through SRVs A small DF of just 2 would be adequate to resolve the issue 1 ML20304A339 - NRC Brochure-State-of-the-Art Reactor Consequence Analyses: Using decades of research and experience to model accident progression, mitigation, emergency response, and health effects Discussion
©2022 Nuclear Energy Institute 15
Additional concerns with addressing TFGR - no guidance is provided in the DG to address TFGR due to high burnup pellet fragmentation in non-LOCA accidents that predict fuel failure aside from reactivity insertion accidents that are addressed in RG 1.236
High burnup-related TFGR guidance for non-LOCA DBAs should be provided
For non-LOCA DBA with fuel overheating, guidance should identify the specific non-LOCA DBAs that are impacted and include applicable TFGR guidance in the relevant Appendices Source Terms and Radiological Consequence Analyses