ML20085F741

AO BFAO-50-259/753W:on 750226,main Steam Relief Valve PCV-1-4 Lifted Prematurely & Did Not Reseat Until Reactor Pressure Reached 480 Psig.Cause Unknown.Leakage Suspected. Valves Replaced

ML20085F741
Person / Time
Site:	Browns Ferry
Issue date:	03/07/1975
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Case E Office of Nuclear Reactor Regulation
Shared Package
ML20085F728	List: ML20085F726 ML20085F741 ML20085F790
References
NUDOCS 8308230160
Download: ML20085F741 (3)

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o o ABiORMAL OCCURREriCE REPORT Report No.: BFAO-50-259/753W -

Report Date: March 7, 1975 Occurrence Date: Februar/- 26, 1975 Facility: Browns Ferry Nuclear Plant unit 1 Identification of Occurrence -

Premature lift of main steam relief valve PCV-1-4.

Conditions Prior to Occurrence The unit was starting up following a trip. ,

Description of Occurrence During startup of the unit following a trip, PCV-1-4 lifted prematurely at approximately 800 psig and did not resent until the reactor pressure reached 480 psig. Upon identification of the valve malfunction, the reactor was shut down to replace this valve and another valve, PCV-1-5, which showed erratic discharge tailpipe temperatures. During startup of the unit after replacement of PCV-1-4 and PCV-1-5 and following a satisfactory leak test at 1,000 pai, PCV-1-22 and PCV-1-23 lifted prematurely. The reactor was shut down to replace PCV-1-22 and FCV-1-23 and to check the pilot steqe leakage of the remaining seven relief valves.

Designation of Apparent Cause of Occurrence PCV-1-4 was manuany actuated imediately 1'o11owing a unit trip from full power earlier in the day. The exact cause of the valve to prematurely open during the restart is not known at this time; however, pilot valve leakage is suspected.

The valve will be disassembled and inspected to determine the cause of the malfunction. Valves PCV-1-22 and FCV-1-23 will also be inspected to determine the cause of premature opening.

Analysis of Occurrence

' No damage to systems, cc=nonents, or structures was experienced; no personnel injuries or exposures were involved; no radioactive materials were released; and there were no adverse effects to the public health and safety as a result of thic occurrence.

• Corrective Action PCV-1-4, PCV-1-22, and PCV-1-23 were replaced with spare relief valves because of their premature lifting. PCV-1-5 was replaced with a snare valve because tailpipe te.'peratures indicated that the valve was leaking through. A nitrogen bubble check was performed on the pilot stage of the remaining seven relief valves in place. The results indicated excessive pilot-stage leakage.

These 830G230160 750731 PDR ADOCK 05000259 S PDR e

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~2- j j Corrective Action (continued) seven relief valves (PCV-1-18, 19, 30, 31, 34, 41, and 42) were repinced with spares to ir: prove unit reliability. Disasse=bly of the removed valves will supply information for use in determining corrective and l preventive measures if needed. A supplemental report vill be issued when the results are available.

Failure Data PreviousfailuresarereportedonAbnormalOccurrenceReportsBFAO-50-260/7430'f; BFAO-50-260/7429W; BFAO-7426W, unit 1; BFAO-749W, unit 1; BFAO-7349W, unit 1; and BFAO-7314W, unit 1. s-Target Rock Corporation - Model 67F - Safety / Relief Valve - Size 6" inlet; l

10" outlet 1,200 psi design pressure Capacity 800,000 lb/hrsaturatedsteam o

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" "'M Mr. Edson G. Case p.,[

Acting Director of Licensing U.S. Nuclear Regulatory Comission QTp# - '

Washington, DC 20545

Dear Mr. Cace:

THINESSEE VALLEY AUDIORITY - BRO'ANS FERRY INCLEAR PLANT UNIT 1 -

DOCITT NO. 50-259 - FACILITY OPERATING LICHISE DPR ABNORIEL OCCURRENCEREPORTBFAO-50-259/753W

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The enclosed report is to provide details concerning a premature lift of the main stean relief valve PCV-1-4 and is submitted in accordance with Appendix A to Regulatory Guide 1.16, Revision 1, October 1973. This event occurred on Browns Ferry nuclear Plcnt unit 1 on February 26, 1975.

Very truly yours, TENNESSEE VALLEY AUTIIORI'lY 4 E. F. omas Director of Power Production Enclosure CC (Enclosure):

!!r. Norman C. Ibsoley, Director U.S. Nuclear Regulatory Commission Regiona1 0ffice 1 230 Peachtree Street, IN., Suite 818 Atlanta, Georgia 30303 l

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o 2717 l . An Equal Occor* unity Employer r

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