ML20198P337
| ML20198P337 | |
| Person / Time | |
|---|---|
| Issue date: | 12/07/1995 |
| From: | Russell W NRC (Affiliation Not Assigned) |
| To: | Morrison D NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML20198P288 | List: |
| References | |
| FOIA-99-52 NUDOCS 9901070033 | |
| Download: ML20198P337 (3) | |
Text
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\ December 7, 1995 MEMORANDUM TO: David L. Morrison, Director Office of Nuclear Regulatory Research FROM: William T. Russell, Director ,h.), s Office of Nuclear Reactor ReguTation
SUBJECT:
THIRD SUPPLEMENTAL USER NEED REQUEST REGARDING POTENTIAL FOR LOSS OF EMERGENCY CORE COOLING IN A B0ILING WATER REACTOR DUE TO CLOGGING OF THE SUCTION STRAINERS BY LOSS-0F-COOLANT ACCIDENT GENERATED DEBRIS In memor 9da dated September 7, 1993; May 11, 1994; and November 29, 1994, the Office o. Nuclear Reactor Regulation (NRR) requested the Office of Nuclear Regulatory Research (RES) to develop a plant-specific model of a reference BWR4 with a Mark I containment (1) to estimate the likelihood that strainer clogging will result in core damage; (2) to estimate debris generation, debris transport, and debris induced head losses; and (3) to determine criteria for long-term resolution of this issue. Also, NRR has asked RES to refine and expand the analytical tools developed under the Boiling Water Reactor (BWR)
Emergency Core Cooling System (ECCS) Suction Strainer Clogging Issue. This memorandum requests additional RES support during the implementation of the resolution of the BWR ECCS Suction Strainer Clogging Issue. RES is being asked to provide additional research and technical assistance, and to expand some of the analytical tools further. RES staff has worked closely with the NRR staff to develop an appropriate resolution to this issue.
As part of the reference plant study, RES developed a calculation model, named BLOCKAGE, to estimate loss of net positive suction head (NPSH) to ECCS pumps due to strainer clogging. NRR considers this a useful tool in evaluating potential licensee resolutions for the BWR Strainer Clogging Issue.
Therefore, NRR requests that RES make BLOCKAGE applicable to containment and plant arrangements in addition to the reference plant used in the plant-specific study. Specifically, NRR would like the changes made to the BLOCKAGE code to provide the following capabilities:
(1) allow user-defined head loss correlations and multiple head loss correlations, (2) allow the code to track multiple debris types, (3) allow the user to input multiple filtration efficiencies, (4) allow suppression pool temperature and NPSH margins to vary with l time, f (5) allow the code to estimate head loss and blockage per strainer, 9901070033 990104 PDR FOIA 0 'M'IALI A99-52 PDR 99010'7003 3 h
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(2) review the models and evaluat an criteria in the forthcoming BWROG l Utility Resolution Guidance (URG) document and advise NRR on the adequacy of the models and criteria, and (3) review analytical models and approaches developed by the industry, that significantly differ from the models and approaches recommended by the NRC or the BWROG.
We ask that the additional research work be completed by the first quarter of the calendar year 1997. NRR would like RES technical assistance until all BWRs have successfully implemented fixes. This support would, therefore, be needed through the end of 1998.
Following the issuance of the final bulletin and revised regulatory guide to resolve the BWR ECCS Suction Strainer Clegging Issue, NRR will be reevaluating this issue for PWRs. RES technical assistance during this upcoming reevaluation of PWRs is also requested. NRR requests RES support in addressing the following issues during this reevaluation:
(1) review of the issues raised by SKI and STUK, (2) identification of accident aspects (including expected operator actions) which are important for debris transport and accumulation on the sump screens in large dry, sub-atmospheric and ice condenser containments, (3) identification of debris sources in PWR containments including potential sources of particulate debris, (4) identification of information or models used in the USI A-43 study that are obsolete, and (5) identification of differences between BWR and PWR analysis methods and NRC guidance, excluding any differences arising from differences in containment type.
The goal of this effort is to determine if there is need for further action to be taken for PWRs beyond that taken during the original resolution of USI A-43. The reevaluation of PWRs should be completed by the first quarter of calendar year 1997.
RES staff has worked closely with NRR staff on the BWR ECCS Strainer Clogging Issue. They have reviewed a draft of this memorandum and are in agreement with the scope of work and schedule being requested.
Contact:
R. Elliott, NRR 415-1397
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! '% December 7, 1995 MEMORANDUM T0: David L. Morrison, Director
- Office of Nuclear Regulatory Research l
FROM: William T. Russell, Director /() -
Office of Nuclear Reactor ReguTation '
SUBJECT:
THIRD SUPPLEMENTAL USER NEED REQUEST REGARDING POTENTIAL FOR ;
t LOSS OF EMERGENCY CORE COOLING IN A BOILING WATER REACTOR DUE i TO CLOGGING OF THE SUCTION STRAINERS BY LOSS-0F-COOLANT l ACCIDENT GENERATED DEBRIS In memoranda dated September 7, 1993; May 11, 1994; and November 29, 1994, the Office of Nuclear Reactor Regulation (NRR) requested the Office of Nuclear Regulatory Research (RES) to develop a plant-specific model of a reference BWR4 with a Mark I containment (1) to estimate the likelihood that strainer clogging will result in core damage; (2) to estimate debris generation, debris transport, and debris induced head losses; and (3) to determine criteria for long-term resolution of this issue. Also, NRR has asked RES to refine and expand the analytical tools developed under the Boiling Water Reactor (BWR)
Emergency Core Cooling System (ECCS) Suction Strainer Clogging Issue. This memorandum requests additional RES support during the implementation of the resolution of the BWR ECCS Suction Strainer Clogging Issue. RES is being asked to provide additional research and technical assistance, and to expand some of the analytical tools further. RES staff has worked closely with the NRR staff to develop an appropriate resolution to this issue.
As part of the reference plant study, RES developed a calculation model, named BLOCKAGE, to estimate loss of net positive suction head (NPSH) to ECCS pumps due to strainer clogging. NRR considers this a useful tool in evaluating potential licensee resolutions for the BWR Strainer Clogging Issue.
Therefore, NRR requests that RES make BLOCKAGE applicable to containment and plant arrangements in addition to the reference plant used in the plant-specific study. Specifically, NRR would like the changes made to the BLOCVAGE l code to provide the following capabilities:
(1) allow user-defined head loss correlations and multiple head loss correlations,
! (2) allow the code to track multiple debris types, (3) allow the user to input multiple filtration efficiencies,
'~ (4) allow suppression pool temperature and NPSH margins to vary with time, (5) allow the code to estimate head loss and blockage per strainer, J
9901070033 990104 PDR FOIA O'MEALIA99-52 PDR 4 9 0 ) D '7 0 0 '> 5 h
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(6) allow the code to recognize common header arrangements, and i (7) allow the user to stop the code once NPSH margin is exceeded.
It is requested that the BLOCKAGE work be completed by May 1996. NRR would also like RES to train NRR staff on the proper use of the BLOCKAGE code.
In response to our first user need memorandum on this issue, RES conducted a study of a reference BWR4 with a Mark I containment. The results of this study are documented in NUREG/CR-6226, " Parametric Study of the Potential for BWR ECCS Strainer Blockage Due to LOCA Generated Debris." The strongest aspects of the study are the wetwell debris transport and head loss models Other models contained in the study (i.e., debris ganeration, debris transport, and filtration) are suitable for assessing the severity of the blockage safety concern, but more comprehensive models will be needed for evaluating potential licensee fixes. The need for more comprehensive models was realized in meetings with the public and industry groups during the public comment period on the proposed bulletin entitled, " Potential Plugging of Emergency Core Cooling Suction Strainers by Debris in Boiling Water Reactors,"
and draft regulatory guide (proposed Revision 2 to Regulatory Guide 1.82),
" Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident." Therefore, we are asking RES to develop analytical models or approaches for debris transport in the drywell that are suitable for evaluating licensee solutions for this problem. In addition, RES technical assistance is requested in evaluating the debris generation model currently under development by the BWR Owners Group (BWROG). NRR also requests that RES conduct additional experiments to refine the filtration database used in the BLOCKAGE calculational model.
In response to our third user need memorandum concerning this issue, RES conducted a series of tests to quantify the settling characteristics of orototypical reflective metallic insulation (RMI) debris. NRR would like RES to conduct tests to quantify the head losses induced oy prototypical RMI debris across a typical suction strainer surface. Also, NRR would like the results compared to the head loss tests conducted with fibrous insulation debris to determine which debris causes more severe head losses. This information will be very useful in evaluating the issue for plants that use RMI instead of fibrous insulation.
Since the RES staff has been primarily responsible for the technical work that supports the resolution of the BWR ECCS Suction Strainer Clogging Issue, NRR would like the RES staff and its contractors to actively participate in the review of industry efforts to develop and implement adequate fixes to resolve the BWR ECCS Suction Strainer Clogging Issue. Specifically, NRR would like RES to:
(1) review BWROG and vendor strainer tests, l
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! I (2) review the models and evaluat an criteria in the forthcoming BWR0G Utility Resolution Guidance (URG) document and advise NRR on the adequacy of the models and criteria, and (3) review analytical models and approaches developed by the industry, l that significantly differ from the models and approaches I
recommended by the NRC or the BWROG.
i We ask that the additional research work be completed by the first quarter of the calendar year 1997. NRR would like RES technical assistance until all BWRs have successfully implemented fixes. This support would, therefore, be needed through the end of 1998.
, following the issuance of the final bulletin and revised regulatory guide to resolve the BWR ECCS Suction Strainer Clogging Issue, NRR will be reevaluating this issue for PWRs. RES technical assistance during this upcoming reevaluation of PWRs is also requested. NRR requests RES support in addressing the following issues during this reevaluation:
(1) review of the issues raised by SKI and STUK, (2) identification of accident aspects (including expected operator actions) which are important for debris transport and accumulation on the sump screens in large dry, sub-atmospheric and ice condenser containments, (3) identification of debris sources in PWR containments including potential sources of particulate debris, (4) identification of information or models used in the USI A-43 study that are obsolete, and (5) identification of differences between BWR and PWR analysis methods and NRC guidance, excluding any differences arising from differences in containment type.
The goal of this effort is to determine if there is need for further action to be taken for PWRs beyond that taken during the original resolution of USI A-43. The reevaluation of FWRs should be completed by the first quarter of calendar year 1997.
RES staff has worked closely with NRR staff on the BWR ECCS Strainer Clogging Issue. They have reviewed a draft of this memorandum and are in agreement with the scope of work and schedule being regtested.
Contact:
R. Elliott, NRR 415-1397 6