ML20085G596
| 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: |
| References | |
| NUDOCS 8308290199 | |
| Download: ML20085G596 (2) | |
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" o 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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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374ot
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Nr. Edson G. Case Acting Director of Licensing
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Office of Regulation
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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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