ML20084U884

Final Deficiency Rept Re Failure of Two Switches.Initially Reported on 730508.Failure Probably Caused by Water Hammer During Refilling of Reactor Bldg Closed Cooling Water Sys

ML20084U884
Person / Time
Site:	Browns Ferry
Issue date:	07/06/1973
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Kruesi F US ATOMIC ENERGY COMMISSION (AEC)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8306290346
Download: ML20084U884 (3)

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Mr. F. E. Kruesi, Director Directorate of Regulatory Operations U.S. Atomic Energy Commission Washington, DC 205h5

Dear Mr. Kruesi:

On May 8, 1973, TVA made initial report by telephone to AEC-DRO Inspector W. S. Little of the failure of two flow switches at Browns Ferry Nuclear Plant unit 1. On June 6,1973, we submitted an interim report on these failures. In accordance with paragraph 50.55(c) of 10 CFR 50, we submit the enclosed final report of the failure.

Very truly yours, f tv' 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 f

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ENCLOSURE FAILURE OF RBCCW FLOW SWITCHES FIS-68-53 AND FIS-68-66 An initial report of the failure of flow switches FIS-68-53 and FIS-68-66 at the Browns Ferry Nuclear Plant (Unit 1) was made by telephone to W. S. Little, AEC-DB0 Region II Inspector on May 8, 1973, in compliance with 10 CFR 50.55(e). An interim report on these failures was submitted on June 6, 1973.

Se glass graduated flov tubes and the glass observation vindous on the above flow switches were found to be brohen about 2 days after the integrated leakage rate test of the primary containment had been co=pleted. In addition, four other flow switches had their glass observation vindous broken. Be containment had been pressurized to 49 psig during General Electric Test 14.

• Each of the broken switch's f1cv tubes is located in a cooling water discharge i

l line from the seal cavity of each recirculation pu=p. Be cooling water is fed from the reactor building closed cooling water (RBCCU) system. .

. It is postulated that the observation vindown i=ploded when the contain=ent was pressurized or, more probable, due to a water hn er that occurred after

• l the test was over. A water bn cr probably occurred during the refilling

, of the RBCCW cyste=, which had been drained and isolated as part of the preparations for doing General Electric Test 14. Be flow tubes could only have been broken by a water hr"- er and not external pressure because they are designed for internal pressure and were tested to 225 psig. De manifacturer verified that an external pressure of 49 psig would not have caused these thick-valled flow tubes to break.

Scre are two separate proble=s related to the class breakage. Se first

~ is the broken observation vindows, which only serve as protection ccainst .

dust.- As such, their function is not necessary and their failure is of no consequence except for depositing broken glass inside the containment. He

, second and most serious of the proble=s is the loss of inventory from the d -* -

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O P3CCW systc=, which is a closed system. Be RBCCW ' system is required to provide cooU.ng functions for the rceirculation pu p seals, the contain=ent I coolers, fuci pool cooling, and other miscellaneous loads. Ec P3CC'.i systc= ,

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has been previously upgraded to scic=ic class 1 requirements to be consistant i with its i=portance. Since draining the system is not preventable by rc=otely operated valves, the inclusion of glass flov tubes is a marginal practice. Bus, all of the glass co=poncnts will be rc=oved to prevent future breakage of these co=ponents. E c observation vindows will be I rc=oved before we exceed a power level of 1 percent. Ec class graduated flow tubes were replaced as a te=porary reasure stile suitable retal replace =ents are ordered. De cctc1 replacccents vill be installed at the first refueling outage on Unit 1. Units 2 and 3 vill have the metal ones instaued before a power level of 1 percent is exceeded.

Se RBCCil system is nor-n11y maintained full of water with a head tank to absorb pressure surges. Adequate precautions were probably not taken in

! refilling the system after the containment leakage tests and a violent l pressure surge or water hc==cr occurred. In the future, proper precautions vill 4 be tchen to prevent such surces or vater hc==crs fror occurring whenever the system is-refilled. H e operating instructions will bc codified to .

caphasize that the systc= should be vented and gradually refilled in strict -

accordance with the original procedure that was used when the system was

. initially filled without causing any descGo. If the system is 'in a state stereby venting end, refilling are required while the glass f1cv tubes are installed, these co=ponents should be accessible and they vill be inspected during and Mter the filling process.

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June 6, 1973 Mr. F. E. Kruesi, Director Directorate of Regulatory Operations U.S. Atomic Energy Con =ission Washington, DC 205h5

Dear Mr. Kruesi:

On May 8, 1973, TVA made initial report by telephone to AEC-DRO Inspector W. S. Little of the failure of two flow switches at Browns Ferry Nuclear Plant unit

1. In accordance with paragraph 50.55(e) of 10 CFR 50, we submit the enclosed interin report of the failure.

Very truly, yours, M

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 V : ,NA 1

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P ENCLOBUBE  :

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FAILURE OF FLOW SWITC11ES FIS-68-53 AND FIS-68-66 An initial report of the failure of flow switches FIS-68-53 and FIS-68-66 at the Browns Ferry Nuclear Plant (Unit 1) was made by telephone to W. S. Little, AEC-DRO, Region II Inspector on May 8,1973, in compliance with 10CFR50.55(e). This is an interim report on those failurcs.

The glass graduated flow tubes and the glass windows on the above flow switches were found broken after the integrated leakage rate test of the primary containment had been completed. The containment had been pressurized to 49 psig during General Electric test No.14. The switches had been tested to 225 psig. Each failed switch is located in a cooling unter a discharge line from the seal cavity of each recirculation pump. The seal cavity cooling water is supplied from and returns to the reactor building closed cooling water system.

We are continuing our investigation into the determination of the safety A

implications of these failures and the corrictive measures required.

final report is expected to be submitted by July 6, 1973. .

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