ML18054A829

LER 89-012-00:on 890607,failed yoke-nut Threads Results in Inoperable Containment Isolation Valve.Caused by Excessive Disc/Stem Loading.Isolation Valve Repaired & Repacked W/Graphite Packing During Upcoming outage.W/890707 Ltr

ML18054A829
Person / Time
Site:	Palisades
Issue date:	07/07/1989
From:	BORDINE T C, KOZUP C S CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-012, LER-89-12, NUDOCS 8907110161
Download: ML18054A829 (4)

Text

PDWERINli MICHlliAN'S PRDliRESS General Offices: 1945 West Parnell Road, Jackson, Ml 49201 * (517) 788-0550 July 7, 1989 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 -LICENSE DPR-20 -PALISADES PLANT -* LICENSEE EVENT REPORT 89-012 -FAILED YOKE-NUT THREADS RESULTS IN INOPERABLE CONTAINMENT ISOLATION VALVE Licensee Event Report (LER)89-012 (Failed Threads Results in Inoperable Containment Isolation Valve) is attached.

This event is reportable to the NRC per 10CFR50.73(a)(2)(i) . .

Thomas C Bordine Plant Licensing Administrator CC Administrator, Region III, USNRC NRC Resident Inspector

-Palisades Attachment 8907110161 890707 PDR ADOCK 05000255 S . PDC OC0789-0151-NL04 A G1it5 CNE'RGY COMPANY

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At 2130 on June 7, 1989, an Auxiliary Operator was unable to fully close the inboard Safety Injection Tank sampling and drain line containment isolation valve, MV-3234A [JM;ISV], after opening the valve to sample one of the -Safety Injection Tanks. The valve yoke-nut threads had been stripped, rendering it impossible to fully close and lock the valve. MV-3234A was declared inoperable.

The downstream isolation valve, MV-3234, was immediately verified to be locked closed. The reactor was critical with the Plant operating at 80 percent of rated power when the failure was NllC"-.. *identified.

Containment isolation valve MV-3234A is a 2 inch manual valve and is one of two manual valves in series which isolate containment penetration MZ-33. By 0035 on June 9, 1989, a temporary mechanical block was placed on MV-3234A to hold it closed. The applicable Technical Specification leak rate surveillance was satisfactorily performed.

The mechanical block was replaced by a stem positioning device on June 15. After the LLRT, MV-3234 was declared operable at 2235. The failure of the valve yoke-nut threads has been attributed to excessive disc/stem loading caused by the valve stem binding in the asbestos packing. The manufacturer has recently changed the packing for new valves of this type to graphite packing. I I NRC For"' lllA 19-631 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION U.S. NUCLEAR REGULATORY COMMIS&ION APPROVED OMB NO EXPIRES: 8/31185 FACILITY NAME 111 DOCKET NUMeER 121 LEll NUM9Ell Ill ,AOE Ill PAL!SADES NUCLEAR PLANT 2 5 5 8 9 0 1 2 0 0 0 2 OF 0 0 5 0 0 0 TEXT l/f --* ....-. .,. -NltC Fonrt.-..'111171 Nl'IC FOl'IM 19-631 Description At 2130 on June 7, 1989, an Auxiliary Operator was unable to fully close the inboard Safety Injection Tank sampling and drain line containment isolation valve, MV-3234A [JM;ISV], after opening the valve to sample one of the Safety Injection Tanks. The valve yoke-nut threads had been stripped, rendering it impossible to fully close and lock the valve. MV-3234A was declared inoperable.

The downstream isolation valve, MV-3234, was immediately verified to be locked closed. The was critical with the Plant operating at 80 percent of rated power when the failure was identified.*

Containment isolation valve MV-3234A is a 2 inch manual valve and is one of two such valves in series which isoiate containment penetration MZ-33. MV-3234A is a Vogt, model SW12401, manual v.alve. Palisades Technical Specification (TS) 3.6.1.a requires that containment integrity be maintained unless the reactor is in the cold shutdown condition.

TS L4.a defines containment integrity to exist when all nonautomatic containment isolation valves and blind flanges are closed. As noted in a letter from Consumers Power to the NRC dated June 2, 1982 and a TS change request for Palisades submitted to the NRC on September 15, 1988, "Section 3.6.4.c of the CE Standard Technical Specifications (STS) permits containment isolation valves to be inoperable provided the affected penetration is isolated by closing at least one manual valve within four hours." Upon discovery of the failed isolation valve, the downstream manual valve, MV-3234, was verified to be locked closed. Consistent with the intent of the June 2, 1982 letter, the Plant entered a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Limiting Condition for Operation.

An NRC Resident Inspector was verbally informed of the situation on June 8, i989 and also informed of Consumers Power's intent to proceed with repairs to the valve and to maintain MV-3234 locked closed. At 0035 on June 9, 1989, a temporary mechanical block was placed on

• MV-3234A, locking the valve closed. TS Surveillance Procedure R0-32-33, "Local Leak Rate Test (LLRT) Procedure for Penetration MZ-33," was performed and, after completion of administrative requirements, MV-3234A was declared operable.

On June 15, 1989, the mechanical block on MV-3234A was removed and a stem positioning device was installed.

This modification restored the capability to stroke MV-3234A.

TS Surveillance Procedure R0-32-33 was again performed satisfactorily and MV-3234A was declared operable at 2235. 3

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• Jo * * \. . . .. , .... NRC Form JMA 19-831 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION U.S. NUCLEAR REGULATORY COMMISSION APPFIOVEO OMB NO JtsO--OtQ.C EXPIRES; B/31 JBS FACILITY NAME 111 DOCICET NUMHR 121 LElll Nl.Mellll Ill PAGE 131 YEAR PALISADES NUCLEAR PLANT O 5 O O 0 2 5 5 8 9 -0 1 2 -0 0 0 3 OF 0 3 TEXT l/f""""" -* --* .,. -NltC Form .m..'111171

"'RC FORM 19-831 Cause Of The Event The failure of the valve yoke-nut threads has been attributed to excessive disc/stem loading. To prevent damage to the valve stem threads, the yoke-nut is designed to fail first when an overloading*

condition occurs. Per the manufacturer (Henry Vogt Machine Company), a condition could exist where, if asbestos packing is installed, the valve stem could bind, thus requiring an excessive amount of torque to operate the valve. Vogt has changed from asbestos packing to graphite packing in recent years. MV-3234A . was packed. with asbestos prior to failure. Note that the downstream isolation valve MV-3234 experienced a similar failure on October 9, 1988. MV-3234 was replaced and declared operable at 0415 on October 27, 1988. The Plant was in cold shutdown during this period. Corrective Action MV-3234A will be repaired and repacked with graphite packing during an upcoming outage. An inspection of all Vogt _model SW12401 valves installed in the Plant or in stock will be performed to ensure all stems are properly lubricated and are packed with graphite packing. This will reduce the probability of similar failures in the future. Analysis Of The Event During the time that MV-3234A was declared inoperable, MV-3234 was operable and locked closed. Containment Integrity was maintained and no threat to health and safety of the public was presented.

This event is being reported per 10CFRS0.73(a)(2)(i)(B) as an operational condition prohibited by TS. Additional Information For additional information regarding containment isolation valves, reference Licensee Event Report 89-009.