ML20039F221
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f Distribution: w/ enclosure JUL 9 81977
$$ $5 M. Rushbrook
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Docket No. STN 50-561 D.
s,)) 9 MEMORANDUM FOR:
D. Ross, Assistant Director for Reactor Safety, DSS R. Tedesco, Assistant Director for Plant Systems, DSS
,p THRU:
D. Vassallo, Assistant Director for Light Water ReactNs, DPM
- 0. Parr, Chief, Light Water Reactors Branch No. 3, D&s,3/
d 4
FROM:
T. H. Cox, Project Manager, Light Water Reactors Branch Nor 3. DPM
SUBJECT:
BABC0CK & WILC0X APPEAL OF STAFF POSITION ON DECAY HEAT REMOVAL SYSTEM ISOLATION Babcock & Wilcox (B&W) is applying for a PDA on the BSAR-205 nuclear steam supply system. The Report to the ACRS was issued on July 8, 1977.
ACRS meetings are scheduled for July 27 (Subcomittee) and August (Full Comittee). The project PDD is October 4, 1977. B&W was notified on June 28, 1977, that their design provisions for DHRS isolation were unacceptable. The subject was discussed with B&W in a telephone conference on June 29 This conference included V. Benaroya (ASB),
e T. Cox (DPM), and G. Mazetis (RSB). B&W has now requested the opportunity s
to appeal the staff position to higher levels of staff management. This first appeal is directed to the Assistant Director level of management.
The meeting is arranged for 07/12 at 1:00 PM in Room P-114. This selection was based on telephone contact with the appropriate offices. F.nclosed is
.r a sumary of the respective staff and B&W positions at this tine.
The resolution of this issue is important to completion of staff review of ti.c BSAR-205 application.
If you are not able to attend, please respond indicating who your representative at the raeeting till be.
Orfdrm! sfreed by Thomas Cox. Project Manager Light Water Reactors Branch No. 3 Division of Project Management
Enclosure:
As Stated cc:
F. Schroeder, w/ enc 1.
R. Boyd, w/ encl.
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Er,c' e n e O'JTSTAN91NG ISSUE, BSAR-205, CONCERNING DHRS ISOLATION CAPABILITY I
STAFF POSITION Power supply assignment to DHR suction line isolation valves inside contairment 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 unmitigated until a valve j
was closed by an operator outside the control room.
B & W POSITION Power loss to bcth valves in one DHR train would require a mechanical failure of an electrical bus, since the bus has two power sources, l
(1) offsite and (2) diesel generator. B & W says that any single I
active component failure, up to and including the breakers on the bus feeding the Valve motors, would still leave the bus powered by one of the two available sources. B & W contends that failure of i
the bus occuring within the sixty seconds required to close the l
isolation valve after an assumed DHRS pipe break (a'so a passive failure) is a scenario too unlikely to require a modification of their current design.
1 They further contend that the NRC criteria in SRP 3.6.1 support the B & W position.
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