ML18059A986
| ML18059A986 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 05/06/1994 |
| From: | Rogers D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-GTECI-048, REF-GTECI-049, REF-GTECI-NI, TASK-048, TASK-049, TASK-48, TASK-49, TASK-OR GL-91-11, NUDOCS 9405160130 | |
| Download: ML18059A986 (3) | |
Text
consumers Power l'OWERIN&
/llllCHl&AN'S l'RO&RESS Palisades Nuclear Plant:
27780 Blue Star Memorial Highway, Covert, Ml 49043 May 6, 1994 Nuclear Regulatory Commission Document Control Desk Washington, DC 200555 David W. Rogers Plant Safety and Licensing Director DOCKET 50-255 - LICENSE DPR-20 -PALISADES PLANT - UPDATE TO FORMER RESPONSE TO GENERIC LETTER 91-11, RESOLUTION OF GENERIC ISSUES 48, "LCOs FOR CLASS lE VITAL INSTRUMENT BUSES," AND 49, "INTERLOCKS ANO LCOs FOR CLASS lE TIE BREAKERS" 0
Consumers Power Company responded to Generic Letter (GL} 91-11 on January 21, 1992. This letter provides an update to that response, describing a different method of complying with the requirement to ensure the plant has procedures that include time limitations for vital AC buses and inverters. The remainder of the January 21, 1992 response to GL 91-11 remains unchanged.
Palisades refers to its vital AC buses as "Preferred AC buses" and to the alternate source for these buses as the "Bypass Regulator". A single Bypass Regulator serves as the alternate source for all four Preferred AC buses, and incorporates a physical interlock to prevent its powering more than one preferred AC bus at a time. It is not an "uninterruptable" source.
If a preferred AC bus were powered from the Bypass Regulator during a loss of offsite power, the bus would be de-energized for about 10 seconds but would be repowered when a diesel generator start was completed.
Palisades Technical Specifications do not explicitly address the use of inverters. At the time of the initial response to GL 91-11, Palisades used an administrative control, Standing Order 54, to limit the time when a Preferred AC bus was powered from the Bypass Regulator to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> limit* had been established due to the discovery of potential equipment failures from a loss bf offsite power concurrent with a Preferred AC bus powered from the Bypass Regulator. Modifications to the plant circuitry eliminated these possible failures and the time limitation was removed from Standing Order-54 without realizing that-it had -been referenced -in our response to GL 91-11.
This oversight was identified during our configuration control project reviews and a corrective action document was initiated. During the evaluation of the corrective document, a review of the effects of a 10 second power interruption on the preferred AC bus loads was completed.
The conclusion was that the Preferred AC buses should be considered inoperable when powered from the bypass regulator.
A CMS' ENERGY COMPANY
2 Therefo.re, Palisades currently limits the time when a Preferred AC bus is not powered from the associated inverter to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, in accordance with Technical Specification 3.7.2g, which provides required action for an inoperable Preferred AC buses.
The limitations on Preferred AC buses have been removed from Standing Order 54, since none of those limitations were more limiting than specification 3.7.2g. A search of maintenance history over the past 5 years disclosed no occurrences where a Preferred AC bus was powered from the Bypass Regulator longer than allowed by the Technical Specifications.
A Technical Specifications change request is currently being prepared to update the entire electrical section. That change will emulate the CE Standard Technical Specifications, NUREG 1432, and provide explicit LCO, required actions, and surveillance for both the inverters and Preferred AC buses.
~lJ.~
David W Rogers, Safety and Licensing Director CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades
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CONSUMERS POWER COMPANY To the best of my knowledge, the contents of this letter, which updates the response to Generic letter 91-11, are truthful and complete.
By
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Robert A. Fenech, Vice President Nuclear Operations Sworn and subscribed to before me this ~ti day of May 1994.
LeAnn Morse, Notary Public Berrien County, Mi~higan Acting in Van Buren County, Michigan My commission expires Febr-uary 4, 1997.
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