ML19343A820

Forwards LER 80-037/03L-0

ML19343A820
Person / Time
Site:	Cooper
Issue date:	11/03/1980
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19343A821	List: ML19343A820 ML19343A829
References
CNSS-800638, IEB-80-17, NUDOCS 8011210564
Download: ML19343A820 (2)

Text

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1 .l ,y9 "T 9 COOPER NUCLEAR STATION N'

b% Nebraska' Public Power District

"^ * * "A*E, a#M;U,*".^i1' " " ' ' '

CNSS800638 November 3,1980 -

c3 C 3 R S Mr. K. V. Seyfrit, Director 6E3 $

fEh-'

U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement f.!T,0 3 Region IV Q ,,

611 Ryan Plaza Drive M Suite 1000 C '.y~

Arlington, Texas 76011

Dear Sir:

. This 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 October 6, 1980. In accordance with the requirements of IE B 211etin 80-17, Mr. Bob Spangler was notified by telephone on October 6, 1980. A licensee event report form is also enclosed.

Report No.: 50-298-80-37 Report Date: November 3, 1980 Occurrence Date: October 6, 1980 Facility: Cooper Nuclear Scation Brownville, Nebraska 68321 Identification of Occurrence:

Conditions leading to operation in a degraded mode permitted by a limiting condition for operation as delineated in Section 3.5.D of the_ Technical Specifications.

Conditions Prior to Occurrence:

. Steady state power operation at approximately 98% reactor power.

! Description of Occurrence:

During routine surveillance testing of the RHR containment cooling system, the "B" loop RHR Service Water Booster pumps would not provide the required flow. The problem appeared to be associated with the system throttle valve SW-M0-89B.

5 80112105# 3 y

s Mr. K.'V. Seyfrit November 3,1980 Page 2.

Designation of Apparent Cause of Occurrence:

The subject valve, SW-MO-89B, is a 18", 300# Globe valve manu-factured by Anchor / Darling Valve Company. The valve was disas-sembled and the disc was found separated from the stem. A skirt en the disc that centers the disc in the valve body was missing.

Further investigation revealed the missing pieces trapped in the restricting orifice downstream.

Analy;.s of Occurrence:

SW-MO-89B is the throttle valve on the discharge of the "B" Loop RHR heat exchanger for the service water side. It controls the service water flow and maintains a minimum 20 psi differential between the service water and the RRR sides of the heat exchanger.

Failure of this valve to operate made the "B" loop of the RHR system inoperable. In the event of an emergency, the "A" loop was operable as well as both diesel generators. This event presented no adverse consequences from the standpoint of public health and safety.

Corrective Action:

The disc and stem nut for SW-MO-89B were replaced. The skirt piece's were removed from the orifice downstream and the line checked visually. Upon successful completion of the repair and proving operability of the "B" loop, the "A" loop valve was dis-aasembled and inspected. This was witnessed by a vendor repre-sentative.

SW-MO-89A was in the same condition as the "B" loop valve including a missing skirt. However, the valve was operable at the time of disassembly. The disc, stem nut, and stem were replaced on this valve. The orifice downstream was removed and inspected and no debris of the missing skirt was found in the line. . It is not possible for these pieces to remain upstream of the orifice so they must have passed through the orifice. It should be noted at this point there is no other valves downstream of the orifice in either loop and these lines. discharge to the river.

The vendor has concluded that the cause of the failure is cavi-tation across the disc and they recommend that the valve disc be redesigned. They also concur that the valve will continue to be operable until the new dise design can be installed, which is anticipated to be at our next refueling critage.

Sincerely,

/I p L. C. Lessor Station Superintendent Cooper Nuclear. Station LCL:cg Attach.

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