ML20086D118
| ML20086D118 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon, 05000000 |
| Issue date: | 09/10/1975 |
| From: | Searls F PACIFIC GAS & ELECTRIC CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| Shared Package | |
| ML20086D112 | List: |
| References | |
| REF-SSINS-6820 730910, IEB-73-02, IEB-73-2, NUDOCS 8311300181 | |
| Download: ML20086D118 (2) | |
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EA:.C I F IC G AS AND ELECTR,IC C O M PANY
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7 7 BEALE S TREET. S A N FR ANCISCO. C ALIFO R NI A 94106. (415) 781 4211 i
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September 10,~1973 f.'.j,5f[,g.'j, aonu c. uoaaessev
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Mr. R. H. Engelken, Director Directorate of Regulatory Operations 4
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U. S. Atomic Energy Commission P. O. Box 1515 Berkeley, California 94701 ei Re:
Dockets 50-275 323 Diablo Canyon, Units 1 & 2 5
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Dear Mr. Engelken:
j Your letter of July 25, 1973 requested that we review the h
design of the control circuit for the containment ventilation system j
isolation valves at Diablo Canyon, Units 1 and 2, to determine whether the failure of a single control switch could result in the simultaneous failure of the redundant supply valves or redundant exhaust valves.
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You further requested that we provide you with the findings of this e
review and, in the event that the review indicated that such a simul-1 taneous failure could occur, that we provide a description of the cor-rective action p].anned and a schedule for its completion.
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We have reviewed the design of the control circuit for the containment ventilation system isolation valves at Diablo Canyon.
As a result, we are modifying, for each unit, the control circuit for the following valves:
FCV-660 Containment Purge Supply (Inside Containment)
FCV-661 Containment Purge Supply (Outside Containment)
RCV-ll Containment Purge Exhaust (Inside Containment)
RCV-12 Containment Purge Exhaust (Outside Containment) i These valves require air to open and fail in the closed posi-i tion upon loss of air or electrical power.
The original design provides a single manual switch in the control room which can simultaneously operate all four of these valves.
Our review has determined that a failure of this manual control switch of the kind experienced at Point Beach 2 could result in these valves remaining in the open position I
after having been opened by means of.the manual control switch.
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Mr. R. H. Engelken 2
September 10, 1973 thic event, the valves could not be closed from the manual control switch and a containment vent isolation would not result in valve clonure.
to provide two manual switches.We are modifying the control circuit design for these va Each of these switches controls one With this modification, the malfunction of a single switch can res i
in only one of the.two redundant valves failing to close.
by the redundant isolation valve. integrity is maintained, even in the event of s Containment November 1, 1973We expect '. hat this design modification will be completed by i
with necessary eq,uipment installed, by February 1, 1974.and that the design this corrective action will be completed prior to the start of pre-In any event, cperational testing and well in advance of fuel loading and initial cperation.
Very truly yours,
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