ML17173A553

Forwards LER 78-068/03L-0

ML17173A553
Person / Time
Site:	Dresden
Issue date:	01/18/1979
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML17173A554	List: ML17173A553 ML19269C171
References
79-51, NUDOCS 7901290263
Download: ML17173A553 (3)

Text

CommonwA Edison Dresden Nuclear Power Station R.R. #1 Morris, Illinois s<f450 Telephone 815/942-2920 January 18 , 1979 BBS LTR 1/79-51 James G. Keppler, Regional Director Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Gl~n Ellyn, IL 60137 Reportable Occurrence Report 1178-068/031-0, Docket.II 050-237 is hereoy submitted to your office.in accordance with Dresden Nuclear Power Station Technical Specification 6. 6. B. 2. (b),

conditions leading to operation in a degraded mode permitted by a limiting condition for operation or plant shutdown required by a limiting condition for operation.

ens on Station Superintendent Dresden Nuclear Power Station BBS:lg Enclosure cc: Director of Inspection & Enforcement Director of Management Information & Program Control File/NRC RtQULf\TORV DOCKET FILt CC':'Y

.790129D.+63

ATTACHMENT TO LICENSEE EVENT REPORT 78-68/03L-0 COMMONWEALTH EDISON COMPANY (CWE)

DRESDEN UNIT-2 (ILDRS-2)

DOCKET /1050-237 During normal oµeration with "A" recirc pump suction valve out-of-service in the op~n position, the breaker for the bypass valve around the recirc pump discharge valve was found thermally tripped after the valve opened. The recirc pump suction valves are presently normally kept OOS in .the open position to elimin-ate the possibility of a spurious closure of the valve during a hypothetical loss-of-coolant accident. The recirc pump discharge bypass valves are nor-mally open to prevent stagnation of the water in the bypass line, but the valve had been closed and reopened after an earlier recirc pump trip.

The low pressure coolant injection system would normally inject into the "B" recirc loop during a loss-of-coolant accident, and this loop was un-affected by this event. However, with this breaker tripped, had the low pressure coolant injection (LPCI) loop-select logic system been required to select the "A" recirc loop for LPCI injection, the bypass valve would not ~ave shut upon signal and some of the LPCI flow could have been di-verted backwards through the bypass valve, the recirc pump, and its suction valve, into the core annulus region.

Calculations indicate that the flow from the 16 inch diameter LP9I injection line which might have been diverted through the 4 inch diameter bypass valve line wa:s minor. Approximately* 2800 gpm could conservatively have been diverted. All four LPCI pumps were operable and each pump is rated at 6000 gpm. Technical Specifications require three LPCI pumps to be operable to deliver the design required 14,500 gpm LPCI flow.

Later testirig could not identify any discrepancies with the operation of the bypass valve. Since the valve is infrequently used, the probable cause was dry packing which affected the opening torque and caused the thermal over}oad condition. Subsequent cycling probably lubricated the packing such that the problem did not ~eoccur. The valve stem will be lubricated during the next refueling outage *

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jDuring normal operation with "A" recirc pump suction valve OOS open, breaker for pump C£II] I discharge oypass valve was found thermally tripped. Had LPCI injection into A loop

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-i:::cill !Later tests found no anomalies with valve operation. Since valve is infrequently usedj ITEJ 1-prooaf>le cause was dry packing which led to thermal overload. Packing and stem wil 1 oe lubricated during next refueling outage.

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