ML20112F011

Ro:On 841213,emergency Generator Stalled 45 After Assuming Emergency Electrical Loads During Emergency Generator Load Test CP-17.Cause Not Found.Stalling Did Not Recur During Subsequent Tests.Mods Will Reduce Starting Load

ML20112F011
Person / Time
Site:	University of Missouri-Columbia
Issue date:	01/11/1985
From:	Brugger R, Mckibben J MISSOURI, UNIV. OF, COLUMBIA, MO
To:	Thomas C Office of Nuclear Reactor Regulation
References
NUDOCS 8501150343
Download: ML20112F011 (3)

Text

Research Reactor Facility UNIVERSITY OF MISSOURI Research Park Columbia, Missouri 65211 Telephone (314) 882-4211 January 11, 1985 Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Mr. Cecil 0. Thomas, Chief Standardization and Special Projects Branch

Reference:

Docket 50-186 University of Missouri Research Reactor License R-103

Subject:

Emergency Generator Description At 1557 on December 13,1984 (a scheduled maintenance day) with the reactor secured, the Emergency Generator Load Test (CP-17) was performed. The emergency generator started automatically and carried the emergency electrical loads as re-quired when the emergency bus automatic transfer switch was shif ted, but stalled approximately forty-five seconds af ter assuming the emergency electrical loads.

The emergency electrical loads were returned to normal facility power and the emergency generator inspected. No cause for the failure to carry the electrical load was found. The emergency generator was manually started without shif ting the emergency electrical loads and all indications were checked normal. The emergency generator was then secured and the load test (CP-17) was again performed with the emergency generator assuming the emergency electrical loads. Therefore the emer-gency generator was operable but was in a degraded state.

Analysis The emergency generator is a 45KVA generator powered by a Ford 292 cubic inch gasoline engine with a one barrel carburetor fuel system and a 12 volt electric choke.

8501150343 850111 PDR ADOCK 05000186 a PDR 0?p 9s 6 0 COLUMBIA KANSAS CITY ROLLA ST. LOUIS an equal opportunity institution

6 f.'

.  : Director of Nuclear Reactor Regulation '

' January 11, 1985 Page 2 e

The emergency generator .was last_ load tested (CP-17) on November 15, 1984.

The emergency generator had started properly when called to start by the automatic

. ' exerciser each week and when manually started as part of reactor start-up checks.

- The emergency generator was last operated at 0700 on December 13 when the auto-matic exerciser started it and ran it for thirty minutes. Af ter 0800 that morning,

.the MURR Electronic Shop performed a scheduled semiannual Preventive Maintenance

, (P. M.) procedure and_ checklist. The P. M. calls for meggering the generator, ,

checking the motor starter and generator, inspecting for broken or damaged parts, plus changing the battery in the tachometer. All P. M. items checked satisfac-L torily.

t At 1557 the emergency generator load test (CP-17) was attempted. As stated before, the emergency generator assumed the electrical loads for approximately

- forty-five seconds. No cause for the emergency generator stalling .under load could be identified. The emergency generator was started and run unloaded with i -

' no abnormalities. The emergency generator was then electrically load tested

+

_(CP-17) four consecutive times. It was observed when starting the emergency gen- l

- erator- that -the amps per phase would differ depending on which ventilation exhaust fan started. The ventilation exhaust fans are driven by 20 HP motors and are the .

-major. load carried by the emergency generator. If the coasting down fan restarted, t the' amps per phase and electrical load on the generator was much smaller than when

[ ..

the _non-running standby . fan started.. The other variable emergency generator loads 4

are small and do not appear to have a significant affect-on the motor generator when starti ng.'

-Since the first attempt to start the emergency generator on December 13,- 1984, -

i it has started properly and handled the emergency electrical loads when re-quired. - Although we cannot determine the reason for the emergency generator to

- stall;after. assuming the electrical loads (a condition we could not duplicate), it U is felt that reducing the starting load on the emergency generator will reduce the-chance of 'the. situation happening again.

- 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 L

reactor will shut down if not.already shut down and decay heat removal willibe

-. performed 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

• insertedL position by gravity. A11' process systems are placed in the.. shutdown

,x . condition due to the failsafe design of 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 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 integrity could

not be indefinitely guaranteed if facility electrical power and emergency-generator

~

4 were not available, but the reactor would be shut'down and containment would not be-J ' required.- - >

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1 Director of fluclear Reactor Regulation January 11, 1985

- Page 3 Corrective Action The generator was manually started unloaded and operated satisfactorily.

With ' the emergency generator secured, the auto transfer switch was again tripped as per (CP-17) and .the emergency generator picked up the emergency electrical loads. . This was repeated four times, each time the emergency generator assumed the emergency electrical loads. The cause of the original failure could not be determined. However, to reduce the starting current load on the generator from the vehtilation exhaust fan motor an electrical modification will be made to the ventilation exhaust fan motor controllers. They will be modified so that the fan coasting down will be started when shifting emergency electrical loads to the emergency generator, which should reduce the load on the generator.

Sincerely, 4

J. C. McKibben Reacto Manager Endorsement: I -

Reviewed and Approved h

R. M. Brugger Director xc: . U. S. Nuclear Regulatory Commission c/o Document Management Branch James Keppler, Director Regulatory Operations - Region III Reactor Advisory Committee Reactor Safety Committee

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