ML19210D694

Forwards LER 79-029/03L-0

ML19210D694
Person / Time
Site:	Cooper
Issue date:	11/09/1979
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19210D695	List: ML19210D694 ML19210D699
References
CNSS790579, NUDOCS 7911270460
Download: ML19210D694 (2)

Text

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COOPER NUCLEAR STATION P.O. BOX 98, BRoWNVILLE, NEBRASKA 68321 Nebraska Publ.ic Power D. is tr.

ic t TEtEmoNe m .2s48n CNSS790579 November 9, 1979 Mr. K. V. Seyfrit U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.4 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on October 12, 1979. A li-censee event report form is also enclosed.

Report No.: 50-298-79-29 Report Date: November 9, 1979 Occurrence Date: October 12, 1979 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

Degradation of the Reactor Equipment Cooling (REC) System piping.

Conditions Prior to Occurrence:

Steady state power operation at approximately 96% reactor power.

Des,cription of Occurrence:

During a routine plant tour, a pinhole leak was discovered in the upstream weld of cl.a supply isolation valve of the south critical header of the Reactor Equipment Cooling System. The valve ident-ification is REC-711MV.

Designation of Apparent Cause of Occurrence:

The apparent cause of the veld failure is unknown at this time.

Analysis of Occurrence:

This defect does not prevent continued operation of this system or its associated systems. This weld is located on the upstream side ,

of the south critical loop isolation valve of the Reactor Equipment Cooling System. This loop furnishes cooling water to the "B" & "D" Residual Heat Removal Pump gland water heat exchangers and the cooling water-fo the fan coil units in the following areas; HPCI /400lk room, RHR pump room southwest corner, and the Core Spray pump room in the southeast corner of the Reactor Building. 5 1398 182 y'f 7011270 46 o

Mr. K. V. Seyfrit November 9, 1979 Page 2.

Operating experience with failures of this same type in non-es-sential portions of the Reactor Equipment Cooling System and the Turbine Equipment Cooling System indicate the crack is tight and growth is very slow. There have been no complete failures of pipe welds in similar systems due to the same assumed failure mechanism.

In the event the indication accelerated its growth, daily surveil-lance by the operating staf f would detect this and corrective action would be taken. Should the failure go unnoticed during normal operation, plant indications such as the system surge tank low level alarm or Reactor Building sump high level alarms would indicate the problem to the operators. During normal operation failure of this weld would necessitate isolating the "A" REC Heat Exchanger and operating the "B" REC Heat Exchanger for non-critical service. In the event the critical service header was required, the "B" REC Heat Exchanger would be available for cooling wcLer and the redundant crosstie to the Service Water System would be avail-able to both critical loops.

This occurrence presents no adverse consequences from the stand--

point of public health and safety.

Corrective Action:

During the next shutdown of sufficient length the subject weld will be repaired. A patch has been installed to control the pinhole leak. A metallurgical analysis is being performed on a failed weld from an earlier event by the Ge cral Electric Company. The an-alysis will be reviewed and corrective action taken based upon this analysis.

Sincerely,

.s

.f & /W L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg } h ,.)

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