ML20085B468

Final Deficiency Rept Re Failures of RHR Svc Water Sys Dresser Couplings & Emergency Equipment Cooling Water Sys Gasket.Initially Reported on 730507.Caused by Water Hammer When Pumps Started

ML20085B468
Person / Time
Site:	Browns Ferry
Issue date:	07/09/1973
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Kruesi F US ATOMIC ENERGY COMMISSION (AEC)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8307080149
Download: ML20085B468 (3)

Text

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ENNESSEE VALLEY A - t'HORITY CHATTANOOGA, TENNESSEE 37401 July 9, 1973

$NebE$N PARTN E A S HIP Mr. F. E. Kruesi, Director Directorate of Regulatory Operations U.S. Atomic Energy Con: mission Washington, DC 205h5

Dear Mr. Kruesi:

On May 7,1973, TVA made initial telephone report to AEC-DRO Inspector W. S. Little of coupling and gasket failures in Browns Ferry RHRSW and EECW syster:s. On June 6 we submitted an interim report on the failures. In accordance with paragraph 50 55(e) of 10 CFR 50, we submit the enclosed final report of the failure.

Very truly b urs, J. E. Gilleland Assistant to the Manager of Power Enclosure CC (Enclosure):

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

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g , ENCLOSURE FAILURES OF RER SERVICE WATER SYST4 DRESSER COUPLINGS AND EMERGENCY EQUIPMENT COOLING WATER SYSTEM GASKET Several failures of equipment in the RHRSW and EECW systems have occurred when pumps were started that supply water to these systems. In each failure, the RHRSW or EECW system had been shut down for a period of time exceeding 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

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The first failure happened on May 6, 1973. This failure was that of an orifice gasket in the diesel generator building on the EECW system. A second failure, that of a Dresser coupling in Unit 3 tunnel on the RERSW header to the 3C RHR heat exchanger, occurred on May 10, 1973. The third failure occurred on May 23, 1973; the failed equipment -was a Dresser coupling in Unit 1 tunnel on the supply to the 1A RER heat exchanger.

The last failure occurred prior to June 12, 1973 (either on June 5 or June'7) and was that of a Dresser coupling on the RHRSW line to the 1C I heat exchanger. This failure was accompanied by noticeable damage to 1 several other pieces of equipment. This associated damage included the

following: (1) loosening relief valve 23-549, (2) separation of a building seal from its pipe, and (3) displacement of hanger R-11 on the RHRSW

pipeline. ,

1 Investigation revealed that all of these occurrences were caused by water hammer taking place when the pumps to the RHRSW and EECW systems were started following a standby period for the systems. The physical configu-ration of each system is such that voids form and air collects in the high points of the pipelines during standby periods. On starting the pump, the water mass quickly compresses the air pockets with little resistance and subsequently expends its energy with the water hammer damaging portions of the system.

Both the RHRSW and EECW systems are safety related. The RHRSW system supplies cooling water to the-RHR heat exchangers that are needed when the plant is shut down. The EECW system furnishes essential. cooling water for-various pieces of emergency equipment throughout the plant, such as the diesel generators. ,

~The failure analysis of these systems. reveals the following:

1. . A single failure in either the RHRSW or' EECW system can be tolerated

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while retaining the capability of shutting down the 3-unit plant.

2. Single failures occurring simultaneously in both systems can be tolerated while maintaining the capability of safely shutting'down the 3-unit plant.

The corrective action taken to prevent recurrences of this type of trouble was to provide charging connections from head tanks in the rav service water system to the RHRSW system and south header of the EECW system.

These charging connections provide the capability of maintaining the systems continuously charged with water so that voids cannot form or air collect at high points in the pipelines of the systems.

All corrective action, except adding a charging connection to the north EECW system header, has been completed as of June 25, 1973 Temporarily, the north header is maintained charged with water by continuously pumping ,

on it with one RHRSW pump that is assigned to the EECW system. The permanent corrective action is presently being designed and will be made when the design is complete.

In addition to this action, the restraints located at the reactor building wall were redesigned and rebuilt to back up the existing ties across the Dresser couplings and to prevent the separation of the couplings caused by prensure surges in the pipeline.

Discussion of and methods of coping with excessive hydraulic forces on other safety-related fluid transport systems are given in the Browns Ferry FSAR as the response to AEC Question R6.1, dated May 22, 19731. We vill continue to take precautions to prevent excessive hydraulic forces (e.g. water hammer and steam compression) in system designs, especially

-in safety related systems which are kept in a standby condition for long periods of time.

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OTENNESSEE VALLEY A%HOAITY CHATTANOOGA, TENNESSEE l 3740'1 40

$NTS$2$N PAATN E ASHIP June 6, 1973 Mr. F. E. Kruesi, Director Directorate of Regulatory Operations U.S. Atomic Energy Commission

, Washington, D.C. 20545

Dear Mr. Kruesi:

On May 7, 1973, TVA made initial telephone report to AEC-DRO Inspector W. S. Little of some coupling and gasket failures in Browns Ferry RHR and EECW systems.

Enclosed is an interim report on these failures; investigation into their causes is continuing,and we expect to submit a final report by July 10, 1973.

[3 Very truly yours,

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/ J. E. Gilleland Assistant to the Manager of Power Enclosure CC (Enclosure):

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

Atlanta, Georgia 30303 t' o

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.. O O ENCLOSURE Failure of RER Service Water System Dresser Coupling and Emergency Equipment Cooling Water Systems Gasket Sequence of Events:

I May 3,1973,10 a.m. - RHR service water header lA Dresser Coupling ruptured in the unit 1 pipe tunnel outside the reactor building.

This occurred immediately after starting the A-2 RER service water pump at the intake building. All RER unit 1 heat exchanger valves were in the closed position. Persons working in the vicinity of the rupture reported considerable vibration and movement of the header just before rupture.

II May 6,1973, 6:10 a.m. - An orifice flange gasket in the diesel generator building supplying emergency equipment cooling water from the EECW system blev out. This occurred immediately after starting an RIS service water pump at the intake building which furnishes water to this system. Considerable pipe vibration was observed by persons in the vicinity just before the gasket failure.

III May 10,1973, lo a.m. - RHR service water header 3C Dresser Coupling ruptured in the unit 3 pipe tunnel outside the reactor building. This occurred immediately after starting RHR service water pump Al at the intake building. The "C" header was valved closed at unit 1-C, 2-C, and 3-C heat exchangers. Pump C1 was operating and the crosstie from pump C1 to C header was open and delivering approximately 2000 gpm to that line. No observation was made of vibration or movement of the piping at the time of rupture nor was the A-1 pump valved to the "C" header. Examination of the ruptured coupling indicates it may have been faulty.

IV May 23, 1973 - RHR service water header lA Dresser Coupling ruptured in the unit 1 pipe tunnel outside the reactor building. The same conditions existed as above (May 3, 1973).

The preliminary investigation indicates water hammer as the cause of failure; however, the investigation and the determination of the corrective action to be taken is continuing. We expect to provide a final report of the failure by July 10, 1973.