ML16342A348
| ML16342A348 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 12/22/1993 |
| From: | Faulkenberry B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Rueger G PACIFIC GAS & ELECTRIC CO. |
| References | |
| NOED-93-5-003, NOED-93-5-3, NUDOCS 9312300035 | |
| Download: ML16342A348 (6) | |
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%p*y4 Docket No. 50-323 NOED No. 93-5-003 UNITED STATES NUCLEAR REGULATORYCOMMISSION REGION V 1450 MARIALANE WALNUTCREEK. CAUFORNIA94596-5368 December 22, 1993 Pacific Gas and Electric Company Nuclear Power Generation, B14A
~77 Beale Street, Room 1451 P. 0.
Box 770000 San Francisco, California 94177 Attention:
Hr.
G.
H. Rueger, Senior Vice President and General Hanager Nuclear Power Generation Business Uni,t Gentlemen:
SUBJECT:
"NOTICE OF ENFORCEHENT DISCRETION FOR DIABLO CANYON UNIT 2 On December 18, 1993, at approximately 4:40 a.m. (all times PST), you requested by telephone that the U. S. Nuclear Regulatory Commission (NRC) exercise its discretion not to enforce compliance with the required actions of Technical Specification (TS) 3.8.2. 1, "Onsite Power Distribution."
You informed the NRC that Diablo 'Canyon Unit 2 would not be in compliance with the requirements of TS 3.8.2. 1, Action Statement b, after 5:40 a.m.
on December 18, in that inverter IY-22 would have been out of service more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and that TS 3.8.2.'1 would then require Unit 2 to be placed in hot standby within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
You stated that IY-22 had been removed from service on December 17 for inspection, maintenance, and the addition of monitoring instrumentation, and that it required unexpected repairs when you attempted to restore it to service.
You indicated that maintenance activities on IY-22, including preparation and installation of a new transformer, were in
- progress, with testing of the inverter to follow.
You requested that verbal enforcement discretion be granted for a period of eight hours to permit Unit 2 to continue operating while repairs on IY-22 were completed and tested.
You indicated that the additional 8-hour period would avoid a plant transient and reduce both operational and shutdown risk.
Your letter dated December 20-,
and revised on December 21,
- 1993, documented your verbal request.
You provided as justification,for continued operation that the distribution panel powered by inverter IY-22 (i.e.,
PY-22) was switched to the backup power source from Vital Bus G through a regulating transformer.
Although Vital Bus G is not an uninterruptible power source, you indicated that the momentary loss of this bus due to a loss of offsite power (LOOP) or due to a plant trip without a LOOP would not result in the loss of any protective features.
In
- addition, rod control was placed in manual and would not be affected by the momentary loss of power.
Other control functions were transferred to sources not powered by PY-22.
Furthermore, your letter stated that your probabilistic risk assessment (PRA) of the safety significance of the requested extension resulted in an increase of 0.4% of the total annual core damage frequency (8.8 X 10 ') due to internal events, assuming that the entire 8-hour extension 9312300035 931222 PDR ADOCK->>05000323iig P
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was used.
You also stated that the Plant Staff Review Committee (PSRC) had reviewed and approved your request before you initially contacted the NRC for enforcement discretion, and that the PSRC also reviewed and concurred with your written request.
In addition, you stated that, as a compensatory
- measure, all vital instrumentation, all six emergency diesel generators, and both offsite power sources would be maintained
- operable, and that operators would be briefed on actions to be taken in the event of a transient during the period of the enforcement discretion.
Based on our review of your justification, including any compensatory measures identified above, we have concluded that this course of action involves minimal or no safety impact, and we are clearly satisfied that this exercise of enforcement discretion is warranted from a public health and safety perspective.
Therefore, it is our intention to exercise discretion not to enforce compliance with TS 3.8.2. 1, Action Statement b, for the period from 5:40 a.m. to 1:40 p.m.
on December 18, 1993.
This letter confirms our verbal granting of enforcement discretion during a telephone call between myself and Nr. John Townsend of your staff on December 18, 1993.
- However, we will consider enforcement
- action, as appropriate, for the conditions that led to the need for this exercise of enforcement discretion.
,b-B.
H. Faulkenberry Regional Administrator CC:
Dr. Richard Ferguson, Energy Chair, Sierra Club California Hs.
Nancy Culver, San Luis Obispo Hothers for Peace Hs. Jacquelyn C. Wheeler Managing Editor, The County Telegram Tribune
- Chairman, San Luis Obispo County Board of Supervisors Hr. Truman Burns, California Public Utilities Commission Hr. Robert Kinosian, California Public Utilities Commission Robert R. Wellington, Esq.,
Diablo Canyon Independent Safety Committee Nr. Steve Hsu, Radiologic Health Branch, State Department of Health Services Hr. Peter H. Kaufman, Deputy Attorney General, State of California Christopher J. Warner, Esq.,
PG&E Hr. John Townsend, Vice President and Plant Manager, Diablo Canyon
bcc Docket File Project Inspector Resident Inspector B. Faulkenberry K. Perkins S'. Richards C. VanDenburgh R. Huey P.
Johnson S. Peterson, NRR G.
Cook J. Callan, NRR W. Russell, NRR J.
Lieberman, OE Technical Assistant H. Smith J; Bianchi J. Zollicoffer REG V
, DRP-I/II, NRR
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