ML24043A116
| ML24043A116 | |
| Person / Time | |
|---|---|
| Site: | Nuclear Energy Institute |
| Issue date: | 02/13/2024 |
| From: | Broadbent G, Pimentel F Nuclear Energy Institute |
| To: | David Garmon-Candelaria NRC/NRR/DRA/ARCB |
| References | |
| Download: ML24043A116 (22) | |
Text
©2024 Nuclear Energy Institute Greg Broadbent, Senior Staff Engineer -
Corporate Nuclear Analysis, Entergy (Retired)
Frankie Pimentel, Sr. Project Manager -
Engineering & Risk, NEI February 13, 2024 Impact of RG 1.183 R1 and SAND2023-01313 on Environmental Qualification
©2024 Nuclear Energy Institute 2 Significant changes to source term release fractions with Reg Guide 1.183 Rev. 1 and SAND2023-01313 may challenge existing EQ analyses EQ history with AST Industry analyses on potential impacts Industry conclusions Environmental Qualification
©2024 Nuclear Energy Institute 3 EQ Background Sandia Re-Baselining Report Evaluated Plants
PWR (Surry)
BWR (Grand Gulf)
Section 5 addressed EQ impacts of AST Airborne
Beta and Gamma Pool
Gamma
©2024 Nuclear Energy Institute 4 Sandia BWR Airborne EQ Results Beta Dose Gamma Dose
©2024 Nuclear Energy Institute 5 Sandia PWR Airborne Results Beta Dose Gamma Dose
©2024 Nuclear Energy Institute 6 Integrated doses calculated with TID source term bound those calculated with AST
An evaluation of the equipment qualification dose using the TID and NUREG-1465 source terms revealed that the containment atmosphere dose using the revised source term was similar since most of the dose is from noble gases, for which the two source terms are identical.
Sandia Airborne Conclusions
©2024 Nuclear Energy Institute 7 Sandia Pool EQ Results BWR
~3500 hours PWR
~1000 hours
©2024 Nuclear Energy Institute 8 Integrated doses calculated with TID source term are not bounded by those calculated with AST at later times
- ~3500 hours for BWRs
- ~1000 hours for PWRs SECY 98-154:
However, the revised source term produces somewhat higher doses later in time (after approximately 1 week in the case of the Surry analysis) due to a much higher inventory of cesium. The significance of any higher dose in the containment sump will be considered in the pilot plant reviews.
Sandia Waterborne Conclusions
©2024 Nuclear Energy Institute 9 Assessed as Generic Issue 187 Concluded no significant chance of meeting the incremental risk thresholds for backfit
- the design basis LOCA has no significant fuel damage,
- the complete washdown of all source terms into the pool is not likely,
- the suppression pool will not be a homogeneous mixture since some settling is expected,
- equipment qualified for a given period may, in practice, remain available for a much longer period,
- the lower decay heat load at later time periods will allow operators more opportunity for alternative strategies, and
- the risk significant period is limited to the first days.
GSI-187 Resolution
©2024 Nuclear Energy Institute 10 Responses to DG-1389 Comments 7-1 and 13-3 the acceptability of continuing to use TID-14844 source term methodology for EQ for licensees that have modified their licensing bases to higher burnup or enrichment than those specified in RG 1.183, Revision 0 (above the 62,000 MWd/MTU of 5 weight-percent uranium-235), has not been assessed. Therefore, when these types of significant plant modifications occur, licensees need to evaluate the impacts on EQ consistent with the modifications made and make updates as appropriate. If the licensee wishes to continue to use TID-14844 for EQ after increasing above the parameters specified in RG 1.183, Revision 0, or when making other plant modifications that affect the applicability of previously approved methods or assumptions, the licensee must demonstrate that how it is using the guidance will satisfy applicable NRC requirements.
Current Staff Position on EQ
©2024 Nuclear Energy Institute 11 Simplified EQ models consistent with Sandia work Relative comparison of 4 cases
TID-14844
RG 1.183 Rev. 0
DG-1389
SAND2023-01313 Source terms updated to RADTRAD standard BWR & PWR inventories NUREG/CR-6604 Sources (Ci/MW) NOT changed for different cases Release Fractions ARE updated for each case Airborne Evaluation Sprayed CMT Un-Sprayed CMT PWR Dose Model Sprayed CMT Un-Sprayed CMT BWR Dose Model Drywell
©2024 Nuclear Energy Institute 12 Doses Evaluated in Sprayed CMT compartment Beta Doses based on Infinite Cloud Gamma Doses from 18 energy group MCNP model
GGNS dimensions Airborne Model dose point 62 ft 2811 Gamma Model
©2024 Nuclear Energy Institute 13 BWR Beta Results 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.E+09 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 Integrated Dose (Rads)
Hours BWR Airborne Integrated Beta Dose TID-14844 Reg Guide 1.183 Rev. 0 DG-1389 SAND2023-01313
©2024 Nuclear Energy Institute 14 BWR Gamma Results 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 Integrated Dose (Rads)
Hours BWR Airborne Integrated Gamma Dose TID-14844 Reg Guide 1.183 Rev. 0 DG-1389 SAND2023-01313
©2024 Nuclear Energy Institute 15 PWR Beta Results 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.E+09 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 Integrated Dose (Rads)
Hours PWR Airborne Integrated Beta Dose TID-14844 Reg Guide 1.183 Rev. 0 DG-1389 SAND2023-01313
©2024 Nuclear Energy Institute 16 PWR Gamma Results 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 Integrated Dose (Rads)
Hours PWR Airborne Integrated Gamma Dose TID-14844 Reg Guide 1.183 Rev. 0 DG-1389 SAND2023-01313
©2024 Nuclear Energy Institute 17 TID airborne doses still bounding!
Consistent with original Sandia results Airborne Conclusions
©2024 Nuclear Energy Institute 18 Pipe Model Gamma shine to an ECCS pump room 100-foot section of 24-inch Schedule 30 pipe Gamma Doses from 18 energy group MCNP model No Beta contribution
Low beta penetration through water and pipe wall Pool Evaluation
©2024 Nuclear Energy Institute 19 BWR Pool Results 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 Integrated Dose (Rads)
Hours BWR Pool Integrated Dose TID-14844 Reg Guide 1.183 Rev. 0 DG-1389 SAND2023-01313
~350 hours
RG 1.183 Rev. 0 cross-over point earlier than Sandia prediction due to higher cesium activities in standard RADTRAD source terms
Sandia appeared to use low-burnup inventories
©2024 Nuclear Energy Institute 20 PWR Pool Results 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 Integrated Dose (Rads)
Hours PWR Pool Integrated Dose TID-14844 Reg Guide 1.183 Rev. 0 DG-1389 SAND2023-01313
©2024 Nuclear Energy Institute 21 Existing TID-Based Pool EQ Calculations NOT Bounding after ~10 hours Many of the Qualitative Arguments in the GSI-187 resolution are still valid
- the design basis LOCA has no significant fuel damage,
- the complete washdown of all source terms into the pool is not likely,
- the suppression pool will not be a homogeneous mixture since some settling is expected,
- equipment qualified for a given period may, in practice, remain available for a much longer period 10CFR50.49 (e)(4) requires EQ be based on the most severe design basis accident MHA is well beyond design basis, developed to meet the 50.67 requirements of substantial meltdown of the core with subsequent release of appreciable quantities of fission products.
Pool Conclusions
©2024 Nuclear Energy Institute 22 TID airborne doses still bounding TID waterborne continue to be exceeded at later times Cross-over point moves earlier than previous studies Most previous justifications in GSI 187 resolution still apply Impact continues to have no significant chance of meeting the incremental risk thresholds for backfit TID-14844 continues to meet the requirements in 10CFR50.49 TID-14844 continues to be applicable for all EQ analyses using RG 1.183 Rev. 1 and SAND2023-01313 releases Overall Conclusions