ML20039F226

Forwards Summary of NRC & B&W Positions on Decay Heat Removal Sys Isolation Capability of B-SAR-205

ML20039F226
Person / Time
Site:	05000561
Issue date:	07/01/1977
From:	Cox T Office of Nuclear Reactor Regulation
To:	Parr O Office of Nuclear Reactor Regulation
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References
FOIA-80-515, FOIA-80-555 NUDOCS 8201120223
Download: ML20039F226 (2)

Text

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Distribution w/ enclosure:

Docket File LUR #3 T. Cox-

0. Parr Dockct flo. STil 50-561 tiOTE T0: Olan D. Parr, Chief, Light Uater Reactors, Branch No. 3, Division of Project Management FROM:

Thomas Cox, Project flanager, Light Water Reactors, Branch tio. 3 Division of Project Manggement

SUBJECT:

B & W APPEAL OF STAFF POSITI0ft Oil DilRS ISOLATI0tl CAPABILITY, BSAR-205 Attached is a sumary of the Staff and B & W positions on the subject issue.

I expect that an Assistant Director Level review meeting will be necessary within a week or two. This would involve R. Tedesco, D. Ross and D. Vassallo.

Thomas Cox, Project Manager Light Water Reactors, Branch tio. 3 Division of Project flanagement

Enclosure:

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OUTSTANDIfiG ISSUE, BSAR-205, CONCERfilfiG DHRS ISOLATION Cp?Mi!.ITY STAFF POSITION Power supply assignment to DHR suction line isolation valves inside containment is such that the two valves in series in one of the two redundant trains take power from the same electrical bus.

In the event of a DHR pipe break outside containment, followed by a single failure of the bus, the control room operator would be unable to isolate the train having the failed bus. We find this unacceptable because the pipe failure would then be unmi ated until a valve was closed by an operator outside the contro room.

B & W POSITION Power loss to both valves in one DHR train would require a mechanical failure of an electrical bus, since the bus has two power sources, (1) offsite and (2) diesel generator. B & W says that any single active component failure, up to and including the breakers on the bus feeding the valve motors, would still leave the bus powered by aflure of the bus occuring within the sixty seconds required to close the isolation valve after an assumed DHRS pipe break (also a passive failure) is a scenario too unlikely to require a modification of their current design.

They further contend that the flRC criteria in SRP 3.6.1 support the B & W position.

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