ML20101P973

Special Rept 92-002:on 920608,valid Failure of EDG B Occurred Due to Failure to Temp Control Valve.Caused by Failure of Two Out of Three Power Pills.Power Pills Replaced & EDG Testing Frequency Increased

ML20101P973
Person / Time
Site:	Wolf Creek
Issue date:	07/08/1992
From:	Bailey J WOLF CREEK NUCLEAR OPERATING CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
92-002, NO-92-0195, NUDOCS 9207140113
Download: ML20101P973 (4)

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J LFCREEK W@ NUCLEAR OPERATING C l

j John A. Bailey i Vice President

Operations l July B, 1992

, NO 92-0195

, U. 8. Nuclear Regu18 tory Connlosio-ATTN 1 Document Centrol Desk

Mail Station Pl-137 Washington. D. C. 20555

Subject:

Docket No. 50-482: Special Report 92-002 Gentlemen The attached Special Report is being submitted in ' accordance with Technical Specification 4.8 l.1.3 concerning a valid failure of Emergency Diesel Generator "B*.

Very truly yours,

(,

John A. Bailey &

. Vice President Opt-rations l JAB /aem t

i cci A. T. Hos. ell (NRC), w/a

! J. L. M11hoan (NRC), w/a i' G. A. Pick (NRC). w/a l

W. D. Reckley (NRC), w/a l

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i 9207140113 920708 7 Box 411 hington, KS 66839 / Phone:(316) 3648831  !

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, Attachment to NO 92-0195 Page 1 of 3 l

SPECIAL REPORT 92-002

{. Valid Failure of Emergency Diesel Gan,qrator "B" Due to Failure of a Temperature Control Valve A

This repcrt describes a valid failure of Emergency Diesel Generator (EDG)

- "B" which occurred on June 8, 1992. This report is being submitted in accordance with Technical Specifications 4.8.1.1.3 and 6.9.2.

l DF.SCR1PTION OF EVENTS 4 On June 8, 1992, at 0044 CDT, EDG *B' was started for an operability test to .

be performed in accordance with surveillance procedure STS KJ.005B, '

' Manual / Auto Start, Synchronization, and Loading of' Emergency Diesel-

! Generator NE02'. At 0058 CDT, the EDG output breaker was closed and at 0110 CDT the EDG was fully loaded. At 0124 CDT, the Control Room received a Diesel Main Bearing Temperature High alarm and at 0128 CDT a Diesel Lube 011

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Temperature High alarm was received. The Diesel Main 3 earing Temperature e High alarm is received when the temperature of one or aore of the EDG's main

, bearings le 190 degrees Fahrenheit or higher and the Diosel Lube Oil Temperature High alarm is received when lube oil tempereture is 165 degrees

. Fahrenheit or higher. Immediate attempts were initiated to lower lube oil temperature by throttling open EDG "B' Coolers Essential Service Water "B" Return Isolation Valve EF V080 and lowering EDG load. When .hese attempts l did not lower lube oil temperature, further investigations revealed that Lube Oil Cooler Temperature Contrul Valve KJ TCV134 was not operating properly. This valve regulates lube oil flow to the lube oil cooler in order to maintain the proper temperature. At 0144 CDT, the decision was made to secure the EDG-and declare it inaperable in order to determine the l cause of the problem with valve KJ TGV134. Technical Specification 3.8.1.1, wh3ch requires the inoperable EDG be restored to operable status within 72

! hours or be in at least Hot Standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and.in Cold Shutdown within the f ollowing 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />, vae entered.

l During the investigation of the failure of valve KJ TCV134, the valve was disassembled by maintt .ance personnel and the thermal assembl/es were removed. These thermal assemblies are commonly known throughout the industry as ' power pills'. The power pills are located inside the valve and provide control based on the temperature of the lube oil passing through the  ;

valve. An inspection of the power pills noted that at least~one or more of the power ullls had failed. New power pills were installed and the valve was reassembled. An EDG operability test was again performed in accordance with surveillance test procedure STS KJ-005B at 0335 CD1 on June 9, 1992.

The EDG was successfully paralled to the bus and ran fully loaded for one hour as required by the surveillance test procedure. Lube oil and_ diesel main bearing temperatures remained within normal operating asnges indicating temparature control valve KJ TCV134 was functioning properly At 0536 CDT, EDG '2' was declared operable and Technical Specification 3.d.1.1 was

, exited.

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, Attachment to NO 02-019$

c Page 2 of 3 l

H ROOT _CAUSE AND_CO,J- /CMVE ACTIONS t

4 The root cause of the failure associated with the temperature control valve was the frf;ure of two out of three power pills. The power pills are hydraulic .alts that position the valve in response to temperature. They are sealeo units that contain a small cup cf wax covered by a rubber

diaphragm. Sitting on the diaphragm is a rubber / metal plug assembly. ,

Increasing the temperature within a specified range causes the wax to i expani, raising the plug a short distance out of the power pill. Three 4

power pills in series provide the f orce and travel distance necessary to

.- position the valve. The-failute of-the power pills has been attributed to

extended storage tbne prior to installation. These power pills.had been in storage for approximately four years, prior to being installed-in the j temperature control valve on Apr 1 29, 1992. Replacement frequency for

these power pills is evury five years.as' recommended-by the manufacturer and are replaced every third refueling outage. . To ensure that. newly installed power pills are not stored for an extended period of. time, the power pills *

will be procured from the manufacturer shortly before planned replacement.

i Also, an Engineering Evaluation Request has been initiated to determine the i feasibility of replacing the three temperature _ control valves associated t with the EDG with similar valves which have a msnual override. -This manual

override would allow the valve to be operated in the event that the power '

pills feiled.

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The newly installeu power pills had also been in storage for approximately 1 four years. A conservative decision was made to install these power pills

in lieu of waiting for new power pills to arrive from the manufacturer i

because of the weather conditions that were present in the area which had the possibility of interrupting offsite power during the time that the EDG ,

was inoperable. The newly installed power pills were replaced with recently

, received power pills. This was accomplished wh;1e.the EDG was out of ,

service for scheduled maintanance on July 7, 1992. +

i 'S FATLURE CLASSIFICATIOW The failure associated with the temperature contro11 valve is considered a

, valid failure in accordance with Regulatory Positien C.2.e(6) of Regulatory ,

Guide 1.106. Revision 1 since'it would ultimately have resulted in EDG '

damage or failure. This valid failure was the fift h valid ~ failure of EDG

'3" in the last 100 valid tests and therefore requires the EDG testing  !

< frequency to be increased to once every seven days as required by Table 4.8-

, 1 of Technical Specification 3.8.1.1. This increased testing frequency did not begin until June 26, 1992, because of a personnel error. The failure to i meet Technical Specification surveillance requiren.ents will be discussed in a Licensee Event Report which will be submitted pursuant to 10 CFR 1 50.73(a)(2)(1- From the time of the last valid failure of EDG "B" on= l December 9, 198^> EDG *B" had undergone 40 successful valid tests prior to I the failure on June 8. EDG 'B' was out of service for a total of'28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />, 12 minutes during this event.

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., Attachment to NO 92-0195 Page 3 of 3 EDG Reliability In response to the Station Blackout. Rule (10 CFR 50.63) Wolf Creek Nucle.u-Operating Corporatica has established an EDG reliability monitoring prograu following guidelines contained in Nucicar Management and Reaources Council  : .

(NUMARC) document 8700, ' Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors.' Including the failure of EDG *B' on June B 1992, there has been one failure in the last 20 demands, one failure in the last 50 demands, and two failures in the last 100 demands for EDGs 'A' and 'B'. This is below the trigger values for Wolf Creek Generating Station-of three failures for the last 20 demands, five failures for the last 50 demands, and eight failures in the last 100 demands, i

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