ML20085G596

AO BFAO-50-259/7461W:on 741227,dampening Pins in Main Steam Line high-flow Pressure Switch Snubbers Installed W/O Proper Review & Authorization.Caused by Personnel Error. Procedures Revised

ML20085G596
Person / Time
Site:	Browns Ferry
Issue date:	01/06/1975
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Case E US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085G600	List: ML20085G596 ML20085G614 ML20085G628
References
NUDOCS 8308290199
Download: ML20085G596 (2)

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ABNORMAL OCCUPRENCE REMET Report No.: 3FAO-50-259/7461W Report Date: January 6,1975 Occurrence Date: Dece=ber 27, 1974 Facility: Browns Ferry Nuclear Plant unit 1 Identification of Occurrence Instanation of da=pening pins in =ain stea=line high-flow pressure switch snubbers without proper review and authorization.

Conditions Prior to Occurrence Unit 1 had been operated up to 100-percent rated power.

• Descrintion of Occurrence The snubber bodies for the =ain stec=line high-flow pressure switches were installed in May 1972 The authorization for this instanation did not provide for the installation of da=pening pins.

On March 4,1974, to aH-inte the cause of spurious isolations, da=pening pins were instaned in position No. 9 as reco== ended by the sten: supply contractor.

Desismatien of Arnarent Cause of Occurrence Installation of these pins was witnessed and docu=ented. It was not recognized that the authorization to instan the snubber bodies had not provided for

_ dc=pening pins and that a separate safety review would be required.

Analysis of Occurrence Snubbing adjustment No. 9 provides a s=all a=ount of da=pening, increasing the response time of .1 second for 80-percent fun scale to .3 second for 80-percent full scale. idhen it was recognized that proper review had not been perfor=ed before dc=pening pin installation, a design study and safety analysis were performed which authori=ed snubbing adjustment No. 7 providing 1.2 seconds for 80-percent full scale response. Since the existing da=pening was less than that later deter ~ined satisfactory, there was no adverse effcet of this occurrence

' on the health and safety of the public, the only adverse effect being the potential for reducing plant availability.

. Corrective Action Plant procedures for reviewing and approving modifications have been revised

_ several times since the date of initial da=pening pin installation. The latest procedural revision was October 16, 1974 The improvements brought about by these procedural revisions reduce considerably the potential for similar occurrences in the future. '

Failure Data 8308290199 750106 '

PDR ADOCK 05000259 S PDR No previous failures.

Republicsnubbers-1/4"NPT,SS Catalog No. 60n e 4

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t TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374ot

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Nr. Edson G. Case ,

Acting Director of Licensing a .

Office of Regulation

/~ ~'@b>b U.S.' Atomic Energy Co= mission Washington, DC 205h5

Dear Mr. Case:

1 TEIGiESSEE VALLEY AUTHORITY - BRO'ANS' FERRY UUCLEAR PIANT UNIT 1 -

DOCKET EO. 50-259 - FACILITY OPEFATING LICENSE DPR ABNORMAL OCCURTC:: ICE REPORT BFAO-50-259/7461W-The enclosed report is to provide details concerning installation of despening pins in main stecaline high-flow preccure suitch snubbers without proper review and authorication and is submitted in accordance with Appendix A to Regulatory Guide 1.16, Revit, ion 1, Octcher 1973 f

This event occurred on Brovns Ferry nuclear Plant unit 1 on December 27, 1974

-i Very truly yours, TEliHESSEE VALIa":Y AUTHORITY A

' (.E4UV E. F. Thomas Director of Power Production Enclosure CC (Enclosure):

Mr. Nor=an C. Moseley, Director Region II Regulatory Operations Office, USAEC 230 Peachtree Street, HW., Suite 818 Atlanta, Georgia ~30303

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