ML20041D329

Forwards B&W Sys Analysis of Loss of Feedwater Accident & Pickard,Lowe & Garrick,Inc Auxiliary Feedwater Reanalysis. Guidelines of NUREG-0737 Item II.E.1.1 & SRP Section 10.4.9 Met Subj to Addition of 4160-volt Breaker

ML20041D329
Person / Time
Site:	Midland
Issue date:	03/01/1982
From:	Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20041D330	List: ML20041D329 ML20041D335 ML20041D339
References
RTR-NUREG-0611, RTR-NUREG-0737, RTR-NUREG-611, RTR-NUREG-737, TASK-2.E.1.1, TASK-TM 16008, NUDOCS 8203050233
Download: ML20041D329 (2)

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power O Consumers General offiers: 1945 West Pernell Road, Jeckson, MI 49201 e (517) 78&O453 Jemse W Cook Vice President - Projects, Engineering and Construction March 1, 1982 O

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Washington, DC 20555

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MIDLAND DOCKET NOS 50-329, 50-330 AW SYSTEM RELIABILITY FILE: 0926 SERIAL: 16008 ENCLOSURES: (1) B&W System Analysis - LOW (2) PL&G AW Reliability Reanalysis - LOW / LOOP On January 22, 1982 CP Co met with the NRC Staff to discuss the Midland AW system unavailability. CP Co stated that the Midland AW reliability analysis, performed by PL&G, demonstrates that our system is adequate and comparable in unavailability to other systems licensed or under review. Since the assumptions and methodology used by'the Staff to set the system unavail-ability goal were not clearly defined, CP Co was unable to fully assess the acceptability of the overall Midland design against the goal.

At the meeting the Staff stated that the analysis used to obtain the AW system unavailiability should be based on the assumptions of NUREG-0611. It was brought out at the meeting and in the Commonwealth Edison Byron Unit's SER that a two pump AW system, which included the capability of powering the motor driven AW pump from either of two emergency diesels, was acceptable to the Staff if the AW system meets the unavailability goal contained in SRP 10.4.9.

The power supply arrangement for the Midland motor driven AW pump will be modified to allow a rapid alignment of the pump to either the "A" or "B" diesel. This is accomplished by providing a 4160V switchgear breaker in each cubicle supplying the motor driven AW pump. One racked to the " operate" position and the otherthat Kirk-Key arrangement racked preventsto thebothdisconnect position.

breakers from being Anrackedinterlock to the with a b N j

" operate" position at the same time will be provided. Control switches for each circuit breaker are provided in the main control room. A concern with this arrangement involves a postulated fire in the "B" switchgear room and/or

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2 "B" AFW pump cubicle located in the "B" switchgear room. The normal power path to the AFW pump runs from the "A" cubicle through the "B" cubicle and then to the pump. A fire in the "B" switchgear room hypothetically disables the turbine driven AFW pump by shorting out the "B" DC system and disables the motor driven AFW pump by shorting the 4160V power cable running through the "B" AFW cubicle to the motor driven AFW pump. The switchgear rooms do not contain any significant transient combustibles and the only installed combus-tibles are fire resistent cables. A fire within the cubicle is improbable unless maintenance work was being performed and in this event precautions are taken to allow work in a " live" cubicle. The possibility of a fire consuming the entire room is also unlikely.

The probability of a fire actually occurring and achieving this level of damage is extremely low. Still, CP Co is installing a separate electrical feed from the "A" 4160V switchgear cubicle to the motor driven AFW pump which can be used as a replacement for the normal feed in the event of such a fire.

This cable will not normally be connected at the pump and no credit for it is taken in the AFW reliability analysis.

To support the time required for manual power supply realignment, a conserva-Live B&W analysis (Enciosure 1) has been provided which demonstrates that at least 25 minutes are available with no unacceptable consequences before AFW system sta rtup is requi red. In addition, the 111dland AFW system reliability has been recalculated (Enclosure 2) using the assumptions of NUREG-0611 and utilizing dual power supplies and a 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Tech Spec requirement for unavail-ability of an AFW pump. The results demonstrate that the AFW system unavail-ability at 15 minutes is within the NRC goal.

With the addition of a 4160V breaker and retention of the original cross-connect ability, tiidland meets the guidelines of NUREG-0737, Item II.E.1.1 and SRP 10.4.9. In addition high pressure decay heat removal can also be provided by feed and bleed. If need be, CP Co can arrange a meeting to discuss the enclosures although we believe the Staff has enough information to close-out this issue.

JWC/ PEP /fms CC RJCook, ?!idland Resident Inspector RHernan, US NRC OParr, US NRC DBtliller, flidland Construction (3)

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