ML20085M135

Final Deficiency Rept Re Failure of Operator for Valve FCV-68-3 in Recirculation Loop A.Initially Reported on 740125.Tripper Spring & Safety Wire Replaced.Set Screw Tightened

ML20085M135
Person / Time
Site:	Browns Ferry
Issue date:	02/25/1974
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Knuth D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085M127	List: ML20085M135
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8311080047
Download: ML20085M135 (3)

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'" TENNESSEE VALLEY AUTHORITY ,

CHATTANOOGA, TENNESSEE 37401 4 '

February 25, 1974 O

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Mr. Donald F. Knuth, Director Directorate of Regulatory Operations Office of Regulation U.S. Atomic Energy Cournission Washington, DC 20545

Dear Mr. Knuth:

On January 25, 1974 TVA made an initial report to AEC-DRO Inspector W. S. Little of a possible deficiency involving the operator for valve FCV-68-3 in recirculation loop A at Browns Ferry Nuclear Plant unit 2. In compliance with paragraph 50.55(e) of 10 CFR 50, the enclosure is submitted as a final report on the occurrence.

Very truly yours, eta 1 J. E. G111 eland Assistant to the Manager of Power Enclosure CC (Enclosure):

Mr. Norman C. Moseley, Director Directorate of Regulatory Operations U.S. Atomic Energy Coassission Region II - Suite 818 230 Peachtree Street, NW.

Atlanta, Georgia 30303 i

8311080047 740313 4

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, BROWNS FERRY NUCIJuut PLANT UNIT 2 FAILURE OF OPERATOR FOR VALVE FCV-68-3 IN RECIRCULATION LOOP A FINAL REPORT On January 25, 1974, an initial report was made to AEC-DRO Inspector W. S.

Little of the failure of the operator for valvc FCV-68-3 in recirculation loop A at Browns Ferry Nuclear Plant, unit 2. This report was made via a telecon by F. W. Miles and A. L. Mazzetti in compliance with paragraph 50.55(e) of 10CFR50. This is the final report on the occurrence.

__ Description of the Associated Plant Equipment The subject valve-operator assembly is located in recirculation loop A in unit 2 of the Browns Ferry Nuclear Plant. This assembly is situated in the pump discharge portion of the loop. The valve is a 28-in. Darling gate valve, motor operated, with a flow rating of 45,200 gpm. Its operator is a Limitorque type SMB-3 valve control.

Description and Cause of Occurrence During Preoperational Test No. GE-8 for unit 2 of the Browns Ferry plant, the operator mechanism of FCV-68-3 in recirculation loop A malfunctioned.

The deficiency was first noticed when the valve control switch was put in the "open" position and the valve started to open. As they do ncrmally, the red and green indicating lights were illuminated while the valve was between the open and closed positions. Ilowever, the green light, which was supposed to go out when the valve was fully opened, remained on, indicating that the valve never completely opened. Af ter waiting approximately six to seven minutes for the open indication, the control switch was put in the "close" position. Both indicating lights continued to burn af ter a waiting period again of approximately six.to seven minutes, showing that the valve did not close. Investigation of the valve disclosed that the valve was stuck partially open with the motor running. The motor circuit breaker was then opened to deenergize the motor.

Disassembly of the operator mechanism. revealed that the motor pinion had slipped along the motor shaft sufficiently-to disengage the. pinion from the L

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. gear train. In audition, the pinion had struck and broken the tripinir spring of the hand wheel ricich mechanism. The set screw that normally secures the motor pinion to the notor shaf t was loose, which had allowed the pinion to slip along the shaft. The safety wire used to secure the set screw was in place; it is likely that the set screw had not been tightened when the pinion was positioned during assembly at the factory.

Corrective Measures The immediate corrective measures taken to repair the operator were to replace the tripper spring, tighten the set screw to secure the gear on its shaf t, and replace the safety wire to prevent movement of the set screw. After assembly, the Limitorque operator worked satisfactorily.

Since no other failure of this type has occurred at Browns Ferry and there are 113 operators of this type purchased for unit 2 with a corresponding number for units 1 and 3, we do not consider it to be a generic problem. We have informed the manufacturer of this failure.

Safety Implications Valve FCV-68-3 in recirculation loop A is safety-related because it must be closed in order that the LPCI system can be effective in case a LOCA were initiated by failure of primary system lines connected to recirculation pump 2B. The LPCI system is redundant to the core spray system.

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