ML20090E179

AO 50-220/74-6:during Releak Testing,Msiv Leaked Excessively.Cause Unknown & Being Investigated.Valve Will Be Inspected

ML20090E179
Person / Time
Site:	Nine Mile Point
Issue date:	04/29/1974
From:	Perkins T, Schneider R NIAGARA MOHAWK POWER CORP.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
References
4224, AO-50-220-74-6, NUDOCS 8303140070
Download: ML20090E179 (4)

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U.S. AEN!3 ER. .. .T NIAGARA MOHAWK POWER CORPORATION $\ 8k,"M" Ell! 52;t!48 I Ok NtAGARA . MOHAWK fa g 300 ERIE BOULEVARD WEST SYRACUSE. N. Y.13202 April 29, 1974 Mr. Donald J. Skovholt 60-2.%0 Assistant Director for Reactor Operations Division of Reactor Licensing United States Atomic Energy Commission Washington, D.C. 20545

Dear Mr. Skovholt:

In accordance with Technical Specifications 1.136 and 4.3.3e for Nine Mile Point Unit 1, the enclosed Abnormal Occurrence Report is-sub-mitted. This report is in accordance with the format set forth in . Regulatory Guideline 1.16.

Very truly yours, Mh R.R. Schneider Vice President - Electric Operations.

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Y ' ABNORMAL OCCURRENCE REPORT

1. Report No. 74.'6 2a. Date April 20,-1974 i.

2b. Occurrence Date April 19, 1974

3. Facility Nine Mile Point Unit 1 '

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4. Identification of Occurrence Excessive Main Steam Line Isolation Valve Leakage.

5. Conditions Prior to Occurrence .

Unit I was shutdown for annual refueling.

6. Description of Occurrence During the process of re-leak testing the MSIV's (AOR'50-220/74-3).

the procedure ^ called for low leakage outside isolation valves and a retest of them. During the retest the outside valve leakage (approx.

95 SCFM) exceeded 12.9 SCFil limit. This valve had'already satisfied the leakage test. on April 2, .1974, therefore the reason for excessive leakage on April 19, 1974 could be attributed to-a not fully closed.

valve or particles trapped under the seat of the valve. - Since the unit was shutdown during this period no hazard.was presented to the general public.

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Designation of Apparent Cause of the Occurrence

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Still under investigation.

8. Analysis of Occurrence.

The Main Steam Line Isolation Valve leakage-through the outside:

valve, would not -present a problem during a shutdown, howeverf priorc to returning the unit to service all valves will be retested. ~ _

-9. Corrective Action The valve will_be inspected to determine the' exact cause of: excessive leakage. ; If.in~ fact,: particles were. caught under the seat it 'may

. become necessary to relapithe valve. -

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10. -Failure Data -

- At least one of these valves has failed to achieve the necessary leak tightnes_s during the annual? test while the unit is shutdown. Therefore,

.an outside. consultant has been retained tofstudy,-examine and recommend- ~

... corrective action. Resulte of this study and corrective actions will be. submitted when available.

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W: HR.JAMESP.O'hY RO:1 OteC0rv PROM: MR. T110 MAS J. PERKINS NINE MILE POINT APRIL 20,1974 ABNORMAL OCCURRENCE 50-220-74-6 MSIV LEAKAGE PURSUAhT TO TECIDilCAL SPECIPICATIONS 1.13 e WE ARE REPORTING AS AN ABNORMAL OCCURRENCE DIE FAILURE OF MSIV #112 TO PASS A LEAK RATE TEST AS ESTABl.I$HED IN TECHNICAL SPECIFICATION 4.3.3.e (4) NINE MILE POINT NUCLEAR STATION LNIT #1.

ON APRIL 2,1974, IN ACCORDANCE WIm TECIDi! CAL STECIPICATION 4.3.3.e (0.' THIS VALVE WAS LEAK TESTED AND SUCCESSFULLY PASSED DIE TEST (11H.7.85 SCFil LEAKAGE. 111E LIMIT FOR INDIVIDUAL VALVE LEAKAGE HAS BEEN ESTABLISHED AS 12.9 SCFH. ON fitAT SAME DAY, AS REPORTED, TILE TWO INSIDE MSIV's FAILED TO PASS THE LEAK RATE TEST.

PRIOR TO RETESTING T1lE FAILED INSIDE VALVES A CHECK WAS MADE OF TUS CdJTSIDE VALVES. LEAKAGE T11RU #I12 WAS DISCOVERED TO BE EXCESSIVE (98.4 SCFH).

11{E CAUSE FOR Tills CilANGE IS UNDER INVESTIGATION ALTHOUGH IT IS SUSPEC11ED BLAT DIRT PARTICLES MAY HAVE BEEN TRAPPED UNDER THE SdAT OR TIlAT VALVE PACKING LEAKAGE MAY HAVE CAUSED T111S CHANGE.

11tE UNIT WAS D0hN FOR REFUELING AT THE TIME SO NO HAZARD WOULD HAVE BEEN PRESEhTED TU die GENERAL PUBLIC. THE VALVE HAS BEEN DEMONSTRATED D) BE WIUlIN SPECIFICATIONS IFNEDIATELY FOLLOWING SHUTDOWN.

THOMAS J. PERKINS STATION SUPERINTENDEhT as mm s

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