ML16341F736
| ML16341F736 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 06/07/1990 |
| From: | Zimmerman R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Shiffer J PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 9006140034 | |
| Download: ML16341F736 (6) | |
Text
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y**y4 UNITED STATES NUCLEAR REGULATORY COMMISSION REGION V 1450 MARIALANE,SUITE 210 WALNUTCREEK, CALIFORNIA94596 aux-v 1990 i~DC Docket No. 50-275 Pacific Gas and Electric Company 77 Beale Street, Room 1451 San Franci sco, Ca 1 iforni a 94106 Attention:
Mr. J.
D. Shiffer, Senior Vice President Nuclear Power Generation Business Unit Gentlemen:
SUBJECT:
TEMPORARY WAIVER OF COMPLIANCE REGARDING DIABLO CANYON UNIT 1 TECHNICAL SPECIFICATION 3.3.1 - MINIMUM CHANNELS OPERABLE REQUIREMENT FOR THE REACTOR COOLANT PUMP UNDERFREQUENCY REACTOR TRIP In your letter dated June 1,
1990, and in discussions with the NRC Staff held prior to the submission of your June 1 letter-you requested temporary relief from Technical Specification (TS) requirement 3.'3-1, Table 3.3-1, Functional Unit 16, regarding reactor coolant pump underfrequency reactor trip instrumentation.
Your letter states that you are requesting a temporary waiver of compliance in order to replace a potential transformer associated with 12kV Bus E.
In order to replace the potential transformer, all three underfrequency (UF) relays associated with Bus E will be made inoperable for a period of four hours.
You concluded that removing the Bus E UF relays from service for four hours, with the unit operating at 1005 power, results in a negligible increase in risk for the following reasons:
Reactor Coolant Pump (RCP) underfrequency protection will continue to be provided by the UF relays'ssociated with 12 kV Bus D.'ou will administratively require Bus D and Bus E to be powered from the same source.
Diverse reactor protection system trip signals associated with bus under-voltage (UV), reactor coolant pump circuit breaker position, and low primary coolant flow, provide assurance that the reactor remains protected from loss-of-flow events.
As a compensatory
- measure, an operator will be stationed with responsibilities to trip the two RCPs associated with Bus E, should an underfrequency condition occur.
Additionally, an analysis performed by Westinghouse demonstrates that should the operator fail to trip the Bus E
RCPs during a loss-of-flow event, all accident acceptance criteria are still met.
The probability of an underfrequency event occurring during the four hour period the Bus E
UF relays are removed from service is estimated to be low (less than 5E-6).
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Based on the above and based on discussions with the NRC Office of Nuclear Reactor Regulation (NRR),
a temporary waiver of compliance for the subject technical specification only is granted from 8:00 a.m.
(PDT), June 8, 1990 to expire at 8:00 a.m.
(PDT), June 15, 1990.
This temporary waiver allows for only one (1) continuous four hour period of waived compliance to occur between the aforementioned dates.
A11 other technical specification requirements remain in effect.
If our understanding of your actions or conclusions is not correct, you should promptly notify this office.
'Sincerely, R7 R,
P.
Z mmerman, Director Divis n of Reactor Safety and Projects CC:
J. Hartin, RV T. Hurley, NRR J. Taylor, EDO J.
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Project Inspector Resident Inspector G.
Cook B. Faulkenberry tl. Smith DRSP File.
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REGION Y
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RZimmerman g/ 7/90
- 8 ST COPY RE UEST COPY REQUEST Y
YES NO E
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NO YES /
NO "S
'D TO PDR YES /
NO
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