ML19275A375
| ML19275A375 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 04/19/1979 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 7910040193 | |
| Download: ML19275A375 (2) | |
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.V SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S street, Box 15830, sacramento, California 95813; (916) 452-3211 April 19, 1979 Nuclear Regulatory Commission
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j Attention:
Mr. R. H. Engelken, Director
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Region V Office of Inspection &
Enforcement G'
Q 1990 ilorth California Boulevard Q
8/
Walnut Creek Plaza, Suite 202
' JUM s' Walrm Creek, California 94595 Docket No. 50-312 Rancho Seco Nuclear Generating Station, Unit No. 1
Dear Mr. Engelken:
The Sacramento Municipal Utility District has responded to IE Bulletin 79-05A in letters dated April 11, 1979 and April 16, 1979.
During telephone conversations between members of the District staff and HRC staff on April 18, 1979, further clarification of our response to Item 8 of IE Bulletin 79-05A was requested. This letter is intended to provide that clarification.
The two auxiliary feedwater systems at Rancho Seco Unit 1 are tied together with a cross-tie line connecting the two flowpaths at a point between the auxiliary feedwater pumps and the control valves located downstream from the pumps.
There are two valves in this line which are normally lef t open during plant operation. The two auxiliary feedwater pumps are powered from separate power supplies and the motor operated control valves are also powered from separate power supplies.
We feel that this arrangement prcvides the necessary independence to assure 100%
flow capacity in the event of any single failure of an active component.
The crosr-tie does not provide true system separation however so tnat operator action is required to assure 100% flow capacity in the event of a single passive failure, such as a pipe break, in the auxiliary feedwater flow path.
The steem driven ; uxiliary feedwater pump is the only pump with automatic initiation with a concurrent loss of offsite power or with a safety features initiation of auxiliary feedwater.
For this reason it is advisable to leave the cross-tie open assuring a 100$ capacity flowpath with a single failure.
In addition, we feel this cross-tie provides greater assurance of heat removal from the primary system through both steam gen +ators providing the operator more flexibility in the selection of main coolant pumps for forced primary coolant circula~ tion should-that,,,
be required.
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~ f1r. R. H. Engelken April 19, 1979 If a normal initiation of both auxiliary feedwater pumps is assumed concurrent with a pipe break in one of the auxiliary feedwater trains, the cross-tie can be closed from the control room since the cross-tie valves are powered with Class I power supplies.
We feel this requirement is outweighed by the considerations which must be given to the possibility of only one auxiliary feedwater pump starting.
If you desire any further details in our decision to operate with this cross-tie open, please advise.
Sincerely yours, k,,,
YMY
[ John d. Mattimoe Assistant General Manager and Chief Engineer cc: Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C.
20555 Robert W. Reid, Chief, Operating Reactors 1099 002"
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