ML20116E262

Ro:On 960701,emergency Generator Shutdown on High Coolant Temp.Caused by Sheared Water Pump Shaft.Replaced Defective Pump

ML20116E262
Person / Time
Site:	University of Missouri-Columbia
Issue date:	07/30/1996
From:	Mckibben J, Meyer W MISSOURI, UNIV. OF, COLUMBIA, MO
To:	NRC (Affiliation Not Assigned), NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9608050176
Download: ML20116E262 (3)

Text

, . i Research Reactor Center Research Park I

UNIVERSITY OF MISSOURI-COLUMBIA Columbia, Missouri 65211 Telephone (573) 882-4211 FAX [573] 882-3443

]

I July 30,1996 Director of Nuclear Reactor Regulation ATTN: Document ControlDesk Mail Station PI-37 U.S. Nuclear Regulatory Commission Washington,DC 20555

REFERENCE:

Docket No. 50-186 University of Missouri Reseamh Reactor License R-103

SUBJECT:

Report as required by Technical Specification 6.1.h.(2) regarding a determination that, subsequent to a week's reactor operation, the Emergency Generator would not have been operable DESCRIPTION At 0640 on July 1,1996, with the reactor secured for regularly scheduled maintenance, a temperature coolant alarm indicated for the Emergency Generator (EG). The EG had started automatically and was running as pan of its nonnal 30 minute unloaded weekly exercise.

A senior operator investigated the alarm and found that coolant temperatum indicated greater than 200 F. The normal running temperatum of the EG is 185 to 190 F. Several minutes after the operator arrived at the EG, the EG shutdown on high coolant temperature approximately 25 minutes into its 30 minute exercise.

Because the EG was unable to run its intended 30 minutes during its weekly exercise, one may conclude that it would hrve been operable for only a short duration if called upon during the previous week's reactor operation from June 24 to July 1,1996. The EG had been exercised satisfactorily on June 24,1996. Technical Specification 3.10(a) states "the recctor shall not be operated unless the emergency electrical generator is operable."

AN A LYSIS The MURR Emergency Generator is a 275 kW generator powered by a Cummins 6-cylinder, water-cooled turbo-charged diesel engine. It has been in service since August 1,1989, and had 260 hours0.00301 days <br />0.0722 hours <br />4.298942e-4 weeks <br />9.893e-5 months <br /> of operation at the time of the coolant temperature shutdown. The emergency electrical system load for MURR is between 50 to 60 kW with the exhaust fan in slow speed, and between 75 to 90 kW with the exhaust fan in fast speed. When the EG starts after a loss of normal electrical power its load is 50 to 60 kW, as the exhaust fan starts in slow speed.

9608050176 960730

{DR ADOCK 05000186 PDR Z.7ll281 751 an equal opporhJrwly ashttAlon rE2.2 0500 3 'I o

Leuer to Director of Nuclear Reactor Regulation July 30,1996

'Page tuo De EG is exercised automatically in the unloaded condition for 30 minutes every week to verify its operability. It is also exercised unloaded before reactor startup if the reactor is shutdown for more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The EG is load tested on a quarterly basis by performing compliance procedure CP-17. Prior to this failure, the EG had been last load tested on June 10,1996.

The reactor was shutdown for the scheduled maintenance day at 0400 on July 1,1996. The EG automatically started and was near completion of hs weekly unloaded 30 minute exercise when a coolant temperature alarm was indicated at 0640. A senior operator investigated the alarm and noted the temperature indication was > 200 F. The EG shutdown on high coolant temperature i several minutes later. The coolant temperature shutdown is one of three automatic protective shutdowns for the EG (others are overspeed and low oil pressure).

l Reactor and Facility Operations staff began evaluations of the EG but were unable to determine l the cause of the high coolant temperature.

t The vendor for the EG was contacted and a technician was sent to troubleshoot the problem.

By 1500 on July 1, the techniciau decided the most likely cause was fouling of the coohng system radiator, although he could not rule out a problem with the water pump which has plastic composite vanes. Funher maintenance to evaluate the EG failure, acquire spare parts, and have the  ;

l radiator cleaned would take several days, so MURR staff asked the vendor to supply a replacement emergency diesel for the week's reactor operation. Repair of the installed EG was scheduled for the following Monday, July 8.

l The vendor supplied a 125 kW diesel generator which was connected into the MURR l emergency distribution center by about 2245 on July 1,1996. The portable EG was load tested by

j. MURR compliance procedure (CP-17) on July 1 prior to resuming reactor operation. It was load tested again on July 8 after the week's operation to verify its capability to have supplied emergency electrical power if it had been needed during the previous week's run while the installed EG was l out of service.

Two vendor technicians continued repair of the EG on Jitly 8 by removing the water pump for inspection. The water pump shaft was found to have sheared between the bearing and the pump.

l This was not expected by the vendor because the EG had only 260 hours0.00301 days <br />0.0722 hours <br />4.298942e-4 weeks <br />9.893e-5 months <br /> of operation. The vendor l

technicians completed repairs to the MURR EG by the aftemoon of July 8. The MURR EG was ,

j then load tested by compliance test CP-17 to verify it was fully operable.

l The analysis for loss of electrical power with the reactor operating at 10 MW and the EG failing to start is covered in Hanards Summary Report (HSR), Addendum 5, Section 2.4.1,2.4.2, and 2.5. In this dual failure mode, the reactor will shut down if not already shut down and decay heat removal will be performed indefinitely by the in-pool heat exchanger. The control blades are releesed on loss of electrical current to their electromagnets and drop to the full insened position by

graviN. All process systems are placed in the shutdown condition due to the fail-safe design of l these systems; i.e., the redundant (only one is required) primary in-pool heat exchanger valves 546 A and B open by spring actuation, placing the convection cooling in-pool heat exchanger in L service. This fail-safe design of the system permits shutdown decay heat removal with no

electrical power (Appendix D of Addendum 4 to HSR). The containment building integrity could not be indefinitely guaranteed if facility electrical power and emergency generator were not available, but the reactor would be shut down and secured, so containment would not be required.

4 d ,- _ ,,m-. -- - -

2 -

l 1xtter to Director of Nuclear Reactor Regulation July 30,1996 I Page three I l

CORRECTIVE ACTION When the cause of the EG coolant high temperature shutdown was not evident, MURR staff called in vendor technicians to evaluate the problem. During the week between technician visits,

, MURR staff reviewed preventive maintenance procedures to determine if any recommended maintenance had been missed which could have contributed to radiator fouling. None of the

recommended maintenance items had been missed.

i a

The vendor technicians found the sheared water pump shaft during their repair work on July 8.

i The root cause of this problem is attributed to a defective water pump shaft. Inspection of the shaft

! revealed rust in the shear area indicating the shaft may have been cracked for some time. The i

defective pump was replaced with a new pump. No other corrective action was determined to be l required.

Sincerely, ENDORSEMENT:

{

Reviewed and Approved f

p i

Walt A. MeyerJr. J. Charles McKibben Reactor Manager Associate Dimetor l

xc: Mr. Alexander Adams, Jr., USNRC .

! Regional Administrator, NRC, Region III

( Dr. John P. McCormick, Interim Vice Provost for Research '

i and Graduate School Dean, UMC  ;

Reactor Advisory Committee

! Reactor Safety Subcommittee j

@4 N41MPT7!30/fh ll CHRISTINE M.ERRANTE Notary Public-Notary Seal STATE OFMISSOURI Boone County My Commission Expires: April 14,1999