ML20036A780
| ML20036A780 | |
| Person / Time | |
|---|---|
| Issue date: | 04/27/1993 |
| From: | Correia R NRC |
| To: | Heltemes J, Russell W, Sniezek J NRC |
| References | |
| NUDOCS 9305140196 | |
| Download: ML20036A780 (2) | |
Text
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April 27,1993 t
NOTE TO:
J. Snic-zek l
W. Russell f
J. Heltemes R. Baer FROM:
R. Correia p i
SUBJECT:
NUMARC PROPOSED REVISION TO MAINTENANCE RULE REGULATORY GUIDE DISCUSSION ON EDG RELIABILITY Attached for your review and comment is NUMARC's proposed revision to the-discussion section of the draft maintenance rule regulatory guide on EDG
.i reliability.
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cc:
E.Rossi
.R.Zimmerman G.Zech G. Grant T.Foley
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W.Minners F. Cherney t
C.Berlinger M. Ring-3 T.Stetka P.0'Reilly r
C. Johnson (RES)
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industry and NRC-sponsored PRAs have shown the risk significance of emergency AC power sources. The Station Blackout (SBO) rule,10 CFR 50.63, required plant-specific coping analyses to ensure that a plant could withstand a total loss of AC power for a specified duration and to determinc appropriate actions to mitigate the effects of a total loss of AC power. During the SBO reviews, most licensees either (1) made a conunitment to implement an EDG reliability program in accordance with NRC regulatory guidance but reserved the option to latcr adopt the outcome of Generic Issue B-56 resolution; or (2) stated that they had or will implement an equivalent program; or (3) endorsed the program embodied in NUMARC 87-00 Revision 1, August 1991, GuidelineundlechnitaLBas for N11M ARC Initiatives Addressing Station Blackout at DELs (i.e., maintain the Emergency Diesel Generator (EDG) target reliability values of 0.95 or 0.975). Subsequently, all utilities docketed commitments to maintain their selected target reliability values. These values could be used as a goal or as a performance criteria for EDG reliability under the maintenancerule.
When utilitics were performing their plant-specific coping analyscs, they were allowed to use plant-speciGe unavailability data due to maintenance. 'lherefore, EDG unas ailability due to maintenance assumed in a plant specific IPE analysis could also be used as a goal or as a performance criteria under the maintenance rule.
1he maintenance rule (10 CFR 50.65(a)(3)) requires that adjustments shall be made where necessary to ensure that the objective of preventing failures of structures.
systems, and components (SSCs) through maintenance is appropriately balanced against the objective of minimizing unavailability of SSCs due to monitoring or preventive maintenance. Therefore, plant-specific EDG reliability and unavailability should be monitored as goals under 10 CFR 50.65(a)(1) or established as performance criteria under the plant's preventive maintenance program under 10 CFR 50.65(a)(2) taking into account the objectives of 10 CFR 50.65(a)(3).
If any perfonnance criterion is not met, the licensce should establish goals and monitor subsequent EDG reliability or availability under 10 CFR 50.65(a)(1). The NRC would find it acceptable if the EDG reliability values selected for compliance with 10 CFR 50.63 are monitored Iluough the use of the trigger values and monitoring methods described in Appendix D of NUMARC 87-00, Revision 1/ excluding paragraph D.2.4.4 (Problem EDG). Appropriate action must be taken by the licensee if any perforrnance criteria is not met.
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