ML18053A532
| ML18053A532 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 08/24/1988 |
| From: | Berry K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8809010087 | |
| Download: ML18053A532 (3) | |
Text
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consumers Power POWElllN&
ll/llCHl&AN"S PRO&RED General Offices:
1945 West Parnall Road, Jackson, Ml 49201 * (517) 788-1636 August 24, 1988 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT -
INTERPRETATION OF TECHNICAL SPECIFICATION 3.7 Kenneth W Berry Director Nuclear Licensing A review of power supplies, for the instrument AC bus (Y-01) and the preferred AC buses (Y-10, Y-20, Y-30 and Y-40), revealed common mode failures of safety systems which can occur when the alternate power supply from the instrument AC bus via the bypass regulator to a preferred AC bus is used.
The difficulties that occur, due to powering a preferred AC bus from the bypass regulator, are:
- 1. If a preferred AC bus is powered from the bypass regulator, it is receiving power from the Engineered Safeguards Bus rather than from a battery and. inverter.
Therefore, if offsite power is lost, the preferred AC bus must be supplied by the diesei generator.
This not only causes a dependency on the proper functioning of the diesel generator, but causes a momentary loss of power while the diesel generator is starting.
- 2. Since both supplies to the bypass regulator are presently fed from "left channel" 2400 VAC bus 1-C, placing "right channel" preferred AC bus Y-20 or Y-40 on the bypass regulator would create cross channel dependencies.
Both 9f these difficulties were created by an NRG-initiated change to the supplies for bus Y-01 (which supplies the bypass regulator) from the original configuration*where Y-01 was fed, through a:n automatic transfer switch, from either bus 1-C or 1-D.
The difficulties which would occur due to operation with Y-20 or Y-40 on the bypass regulator wi.th a concurrent loss of offsite power are a less limiting subset of those which would occur when operating with the No. 2 station battery out of service with a concurrent loss of offsite power for the following reasons:
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Nuclear Regulatory Commission Palisades Plant Interpretation of Technical Specification 3.7 August 24, 1988
- 1. If a preferred AC bus is on the bypass regulator, that bus becomes dependant on bus l~C for power.
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- 2. If the No. 2 battery is out of service, BOTH preferred AC buses on that side become dependant on proper operation of the opposite 2400V AC bus.
The impact of losing power to a single preferred AC bus is less limiting than the loss of that bus, plus another preferred AC bus.
Therefore, operating with either Y-20 or Y-40 on the bypass regulator is less of a concern than operating with the No. 2 station battery out of service.
- The case of Y-10 or Y-30 being powered by the bypass regulator is not a subset (from a consequences standpoint) of having battery No. 1 out of service since, when one of these buses is on the bypass regulator, restoring preferred bus power is dependent on proper operation of Bus 1-C versus when battery No. 1 is out of service; restoring power to the preferred buses is dependent on proper operation of the opposite channel, Bus ID.
Based on an engineering review of particular loads on preferred AC buses Y-10 and Y-30, it has been determined that placing Y-10 on the bypass regulator is bounded by an inoperable station battery No. 1, but that Y-30 on the bypass regulator is not bounded by an inoperable station battery No. 1.
This is primarily due to Y-30 powering the auto-close relay for D-G 1-1 output circuit breaker.
Current Palisades Technical Specifications do not address energizing a preferred AC bus from the bypass:,."regulator, al though this mode of operation is described in the FSAR.
Technic.~i Specification 3. 7.2.h establishes a 24-hour time limit for an inoperable static;m battery.
Technical Specification 3. 7. 2. g establishes an eight-hour time limit for an inoperable preferred AC bus.
Combustion Engineering (C-E) Standard Technical Specification 3.8.3.1 ACTION b (2) provides a 24-hour time limit to re-energize an AC vital bus from its associated inverter connected to its associated DC bus.
Based on time limits in C-E Standard Technical Specifications and Palisades Technical Specifications time limit for an inoperable station battery and concerns described above, Palisades is establishing the following requirement in conjunction with Technical Specification 3.7.2 for energizing a preferred AC bus from the bypass regulator:
Preferred AC Bus Being Powered By the Regulator
- 1. One of preferred AC buses Y-10; Y-20 or Y-40 may be energized from the bypass regulator for up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> provided the reactor protection and engineered safety feature systems supplied by the remaining three preferred AC buses are all operable.
- 2. Preferred AC bus Y-30 may be energized from the bypass regulator up to eight hours provided the reactor protection and engineering safety feature systems supplied by the remaining three preferred AC buses are all operable.
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Nuclear Regulatory Commission Palisades Plant Interpretation of Technical Specification 3.7 August 24, 1988 3
The outstanding Technical Specification Change Request for Technical Specification 3.7, "Electrical Systems", submitted by Consumers Power Company letter dated March 25, 1986 will be revised during the restructured Technical Specifications rewrite to reflect the above time limits for energizing a pref erred AC bus from the bypass regulator.
In addition, Consumers Power is evaluating a possible modification of the power supplies to the bypass regulator based on the potential benefit gained from changing the power sources.
Kenneth W Berry Director, Nuclear Licensing CC Administrator, Region III, NRC NRC Resident Inspector - Palisades OC0888-0100-NL04