ML20040H484

Ro:On 820111,automatic Starter Circuit Failed to Start Emergency Generator on Loss of Site Electrical Power.Caused by Inability of Generator Choke to Compensate for Lower Ambient Temp Due to Extreme Cold Weather

ML20040H484
Person / Time
Site:	University of Missouri-Columbia
Issue date:	02/10/1982
From:	Alger D, Mckibben J MISSOURI, UNIV. OF, COLUMBIA, MO
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8202180299
Download: ML20040H484 (2)

Text

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Research Reactor Facility UNIVERSITY OF MISSOURI Research Park Columbia, Missouri 65211 February 10, 1982 Telephone (314) 882-4211 o 9N.

Director of Licensing #

U. S. Nuclear Regulatory Commission ,

D,d k 1,igggg'g,du 9f Washington, D. C. 20555 -

Reference:

Docket 50-186 c 7I982 University of Missouri E di.u tag b License R-103 , ic,. #

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Subj ect: Difficulty in starting the , g emergency electrical generator.

Description During the January 11, 1982 maintenance day with the reactor shutdown, the automatic starter circuit failed to start the emergency generator on a loss of site electrical power. Operations' personnel inspected the emergency generator and manually started it within twelve minutes of the loss of site electrical power.

Therefore the emergency generator was operable but in a degraded state.

Analysis The emergency generator is a 45KW generator powered by a Ford 292 cubic inch gasoline engine with a one barrel carburetor fuel system. The generator is located in the north tower, an enclosed concrete and steel structure located on the north face of our containment building. fhe enclosure has an electrical heat-ing coil to maintain the temperature above 50 F.

January 10 agd 11 were gery cold days with a low of -19 F and wind chill in-dexes between -50 F and -60 F. This caused U the north0 tower to be cooler than normal, with the temperature being between 40 F and 50 F. The loss of site elec-trical power occurred at 0716 on January 11, 1982. The cranking limiter trip se-cured the starter motor after the starter had run for one minute without the engine starting. The Shift Supervisor and Maintenance Engineer inspected the emergency generator, found the " fail to start" light on and cleared it, then verified that gasoline was available in the day tank. Next, they attempted to start the generator manually but had to cover part of the air intake to increase the choking to get it to start. The generator started and was supplying the emergency electrical loads by 0728.

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. a Director of Licensing February 10, 1982 Page 2 The emergency generator has been starting properly since January 11, 1982.

The failure to automatically start, as can best be determined, was the inability of the generator's choke to compensate for the lower ambient temperature caused by the extreme cold weather.

The analysis for loss of electrical power with the reactor operating at 10MW and the emergency generator failing to start is covered in Hazards Summary Report (HRS), Addendum 5, Section 2.4.1, 2.4.2, and 2.5. In this dual failure mode, the reactor will shutdown if not already shutdown and decay heat removal will be performad indefinitely by the in-pool heat exchanger. The control blades are released on loss of electrical current to their electromagnets and drop to the full inserted position by gravity. All process systems are placed in the shut-down condition due to the failsafe design of these systems; i.e. the redundant (only one is required) primary in-pool heat exchanger valves 546A and B open by spring actuation placing the convection cooling in-pool heat exchanger in service.

This failsafe design of the system permits shutdown decay heat removal with no electrical power (Appendix D of Addendum 4 to HSR). The containment building in-tegrity could not be indefinitely guaranteed if facility electrical power and emergency generator were not available, but the reactor would be shutdown and containment would not be required.

Corrective Action

, The emergency generator was manually started and supplied the emergency elec-trical loads within twelve minutes. The University maintenance personnel performed

an engine tuneup but found nothing out of adjustment. The generator was load tested on January 11 and 25, and February 8,1982; additionally it has been exer-cised at least weekly and has started properly every time.

The generator will be started weekly to be reasonably assured of its proper operation.

Sincerel ,

0 v J. C. McKibben Reactor Manager Endorsement:

Reviewed and Approved -

g, g Don M. Alger Acting Director JCMK:vs cc: U. S. Nuclear Regulatory Commission c/o Document Management Branch James Keppler, Director Regulatory Operations - Region III Reactor Advisory Committee Reactor Safety Conmittee John H. Tolan, Radiation Safety Officer

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