NUREG/CR-5234, Submits Comments on Draft NUREG/CR-5234, Value Impact Analysis for Generic Issue 51:Improving Reliability of Open- Cycle Svc Water Sys
| ML20245G842 | |
| Person / Time | |
|---|---|
| Issue date: | 04/21/1989 |
| From: | Barrett R Office of Nuclear Reactor Regulation |
| To: | Berlinger C Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19306D150 | List: |
| References | |
| RTR-NUREG-CR-5234, TASK-051, TASK-51, TASK-OR NUDOCS 8905030247 | |
| Download: ML20245G842 (2) | |
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... .o-1 [sOQtc %, UNITED STATES nClosure 2 y g NUCLEAR REGULATORY COMMISSION r,, ;E WASHINGTON. o. C. 20655 f
%, p APR 211989 r MEMORANDUM FOR: Carl Berlinger, Chief Generic Communications Branch Division of Operational Events Assessment FROM: Richard J. Barrett, Chief Risk Applications Branch Division of Radiation Protection and Emergency Preparedness
SUBJECT:
RAB COMMENTS ON DRAFT NUREG/CR-5234 ,
"VALUE IMPACT ANALYSIS FOR GENERIC ISSUE 51: !
IMPROVING THE RELIABILITY OF OPEN-CYCLE SERVICE WATER SYSTEMS" i i
REFERENCE:
(1) Operating Experience Feedback - Service Water System l Failures and Degradations NUREG-1275, Vol. 3, Nov.1988 In response to an informal request from your staff, RAB has conducted a limited review of the subject draft report developed by PNL. This review 3 focused on the PRA related information of the report, such as; experience data, and a:,somptions, .and models used to assess the impact of Service Water Systems i (SWS) failure on core-damage frequency. Our review involved a comparison between tAe PNL report and reference (1) report developed by the AEOD staff.
We found serious disagreement between the two studies in the assumptions and results, especially in the magnitude of SWS contribution to core damage frequency. It is our view that the difference between the two studies resulted from the following:
a) The RSSMAP SWS and CCWS models used by PNL are outdated. Common cause failures are not properly considered in these nodels, and major advancements in modeling these two systems have occurred since the WASH-1400 models were developed. (As an example, the NUREG-1150 Peach Bottom PRA shows the Emergency Service Water System contributing to almost all of the dominant nquences either by directly failing a system or indirectly causing failure as a result of loss of cooling to the DGs).
b) The experience data sample examined by PNL is smaller and older when compared to' that examined by AE0D.
c) It is true that clogging and biofouling are more serious for backups or standby loops. However, PRA takes full credit for these loops when SWS unavailability is quantified.
it is our conclusion that the PNL estimate of SWS contribution to CDF Heneg,per (10- plant yesr) is an underestimate. In addition, uncertainties associated l with this estimate (which were not addressed by the authors) seem to be substantial
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-Our findings were _ informally. communicated to your staff on April 3rd.- If you ;
-have any questions regarding our commer,ts, please contact A. El-Bassioni of say i
staff (x21094).- ,
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R c ard J. Barrett, Chief Risk Applications Branch Division of Radiation Protection and Emergency Preparedness Office of Nuclear Reactor Regulation-
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