ML18024B541

Forwards LER 79-043/03L-0

ML18024B541
Person / Time
Site:	Cooper
Issue date:	01/23/1980
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML18024B542	List: ML18024B541 ML18024B543
References
NUDOCS 8002280420
Download: ML18024B541 (3)

Text

COOPER NUCLEAR STATION Q Nebraska Public Power District P.O. BOX 98, BROWNVILLE, NEBRASKA 68321 TELEPHONE (402) 825-3811 CNSS8ggg68 January 23, 1980 Mr. K. V. Seyfrit U.S. Nuclear Regulatory Commission

'ffice 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 December 28, 1979. A licensee event report form is also enclosed.

Report No.: 50-298-79-43 Report Date: January 23, 1980 Occurrence Date: December 28, 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.

Description of Occurrence:

During a routine plant tour, a pinhole leak was discovered in a weld downstream of the "A" & "B" REC pumps.

Designation of Apparent Cause of Occurrence:

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

Analysis of Occurrence:

This defect does not prevent continued operation of this system or its associated systems. The weld is located'n the'ownstream side of the "A" GIld "B" REC pumps and on the upstream side of the "A"

REC heat exchanger. During normal operation, one heat exchanger supplies both loops of the REC Critical Service Supply Header, the Drywell Supply Header, and the Non-Critical Supply Header.

(IPr 008880 <<0

Mr. K. V. Seyfrit January 23, 1980 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 the growth is very slow. There have been no complete failures of pipe welds in similar systems due to the same assumed failure mechanism.

Should the growth rate start to accelerate, it would be detected by the Operations Staff's daily surveillance 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 the 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 water 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 pin-hole leak. A metallurgical analysis is being performed on a failed weld from an earlier event by the General Electric Company; The analysis will be reviewed and corrective action 'taken based upon this analysis.

Sincerely, L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg

'Attach.

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