ML20128F508
| ML20128F508 | |
| Person / Time | |
|---|---|
| Issue date: | 02/04/1993 |
| From: | Correia R NRC |
| To: | Will Smith NUCLEAR ENERGY INSTITUTE (FORMERLY NUCLEAR MGMT & |
| References | |
| NUDOCS 9302110432 | |
| Download: ML20128F508 (2) | |
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Mr. Walter J. Smith, Senior Project Manager Nuclear Management and Resource Council 1776 Eye Street, N.W.
Suite 300 Washington, D.C. 20006-2496
Dear Mr. Smith:
The staff has reviewed the January 19, 1993 NUMARC submittal regarding emergency diesel generator reliability that was a proposed addition to the NUMARC Maintenance Rule Implementation Guideline NUMARC 93-01, revision 2A.
The wording drafted by the staff after reviewing the NUMARC proposal is _
enclosed for your information. The staff will be available to hold a public meeting to discuss this proposed addition.
Please let me know if you have any questions regarding the contents of the enclosure.
Sincerely, Orldnaldgned te Richard P. Correia, NRC Coordinator for NRC/NUMARC Maintenance Interactions cc: NRC Public Document Room DISTRjjLUTION:
Central Files PDR- .
RPEd RF J.Sniezek, ED0 W. Russell, NRR J.Heltemes, RES R.Baer, RES R.Correia, NRR 0.Rothberg, RES A.Serkiz, RES W.Mir.ners, RES J. Richardson, NRR A.Thadani, NRR C.Berlinger, NRR E.Rossi, NRR
. a , 0 .100034 T.Foley, NRR C.Petrone, NRR M. Ring, R-III T.Stetka, R-IV /
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x Enclosure Industry and NRC-sponsored PRAs have shown risk importance of reli' ability and unavailability of emergency AC power sources. The Station Blackout (SBO) rule (10 CFR 50.63) required plant specific analyses to determine appropriate.
actions to mitigate the effects of a total loss of AC power.- In.-response to-the requirements of the SB0 rule, utilities have docketed commitments to maintain the Emergency Diesel Generator (EDG) target reliability (1.e., 0.95 or 0.975) used in their plant specific analysis required by the rule. The EDG1 unavailability due to maintenance used in developing the SB0 rule was 0.007; however, utilities were allowed to use plant specific EDG unavailability data in their plant specific analyses (Regulatory Guide 1.155). Alternatively, EDG unavailability due to maintenance assumed in the plant ' specific IPE analysis could be used as an EDG target unavailability. The maintenance rule (10 CFR 50.65(a)(3) has the objective of ensuring that preventing failures of structures, systems and c uponents (SSC) through maintenance.is appropriately balanced against the unavaihbility of SSCs due to maintenance activities.
The plant specific EDG reliatility and unavailability targets discussed above should bo monitored as goals under 10 CFR 50.65(a)(1) or established as performance criteria under the plant's preventive maintenance program required by 10 CFR 50.65(a)(2) taking into account the objectives of 10 CFR 50.65(a)(3).
Examnles under 10 CFR 50.65fa)(D The utility would balance EDG reliability and unavailability and establish goals for each. The reliability goal could be met by meeting NUMARC initiative 5A reliability trigger values. The unavailability goal, =on a rolling one year basis, would be met by having fewer hours unavailable than required by the goal.
Egm_ple under 10 CFR 50.65(a)(2)
. The utility would balance EDG reliability and unavailability and' establish perforr ance criteria for each. The absence of maintenance. preventable failures or the occurrence of a single maintenance- preventable failure with appropriate root cause determination and corrective action would satisfy the EDG reliability criterion. The second EDG maintenance _ preventable failure should result in establishing goals and monitoring of subsequent EDG' reliability and availability under 10 CFR 50.65(a)(1). Performance criteria for unavailability would be met by having fewer hours unavailable on a rolling.
year basis than required by the perform'ance criteria. If the performance criteria are not met on a rolling year basis, EDG reliability and unavailability should be monitored under 10 CFR 50.65(a)(1).
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