ML20150D305

Forwards LER 78-032/03L-0

ML20150D305
Person / Time
Site:	Cooper
Issue date:	10/13/1978
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20150D308	List: ML20150D305 ML20150D319
References
NUDOCS 7812050135
Download: ML20150D305 (2)

Text

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F 4 [ COOPER NUCLE AR STATION P.O. Box 98, BRO \ /NVILLE, NEUR ASKA 68321 l

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Nebraska Public

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Power Distr.ic t 1ELEmoNEs m a2s.38n October 13, 1978 f

Mr. K. V. Seyfrit U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Suite 1000 Arlingtoi , Texas 76011

Dear Sir:

Tn!s report is submitted in accordance with Section 6.7.2.B.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on September 18, 1978. A licensee event report form is also enclosed.

Report No.: 50-298-78-32 Report Date: October 13, 1978  !

Occurrence Date: September 18, 1978 )

Facility: Cooper Nuclear Station l Brownville, Nebraska 68321 l Identification of Occurrence:

A condition .vhich resulted in the limiting condition for operation established in Section 3.5. A.3(2) of the Technical Specifications.

Conditions Prio to Occurrence:

Reactor power level was steady state at approximately 70% of rated thermal power.

Description of Occurrence:

Upon completion of a torus cooling evolution, residual heat removal valve (RilR-MO-66B) was manually actuated to open. The valve did not fully open prior to receipt of a motor overload, ground alarm and breaker trip.

Designation of Apparent Cause of Occurrence:

A set screw on the valve stem retaining yoke of a Limitorque SMB-3 operator had loosened. The yoke rotated and mechanically bound the valve stem which overloaded and tripped the valve motor.

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7812050135 5

Mr. K.'V. Seyfrit October 13, 1978 Page 2.

Ana3' "s of Occurrence:

'.-MO-66B (RllR Heat Exchanger Bypass) receives an "open". signal in {

event of a low pressure coolant injection (LPCI) initiation.

valve failed partially open. This flow path, in addition to

.6 through the heat exchanger, would have allowed flow in the vent of a LPCI initiation. Upon receipt of the control room indications, the valve was manually opened. There was a redundant system availabic. There were no adverse consequences from the standpoint of public health and safety.

Corrective Action:

The valve stem retaining yoke was repositioned and the set screw which had loosened was tightened. An additional set screw was installed to mechanically lock the first set screw. A review of past LER's indicate that this event is one-of-a-kind, therefore, additional inspection of other Limitorque operators is not war-ranted at this time.

Since rely, 467 ) -

[L.C.LessorIa4 Station Superintendent Cooper Nuclear Station LCL:cg Attach.

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