ML20079K749

Ro:On 831215,emergency Generator Gasoline Engine Electrical Interlock Protective Circuit Tripped.Caused by Bent & Nearly Grounded Electrical Connecting Wire Spade Lug.Trip Sensor Leads Placed to Prevent Grounding

ML20079K749
Person / Time
Site:	University of Missouri-Columbia
Issue date:	01/13/1984
From:	Alger D MISSOURI, UNIV. OF, COLUMBIA, MO
To:	Thomas C Office of Nuclear Reactor Regulation
References
NUDOCS 8401250128
Download: ML20079K749 (3)

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Research Reactor Facility UNIVERSITY OF MISSOURI Research Park Columbia Misso: n 65211 January 13, 1984 Telephone (314) 882-4211 Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Mr. Cecil 0. Thomas, Chief Standardization & Special Projects Branch

Reference:

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

Subject:

Emergency Generator

Description:

At 1515 on December 15, 1983, with the reactor operating at full power, it was discovered the emergency generator gasoline engine electrical interlock protective circuit was tripped. The protective circuit is designed to turn off the emergency generator on either high coolant temperature, low oil pressure, or engine overspeed condition. The emergency generator will not start with the protective circuit in the tripped condition. Af ter the tripped condition was reset, the motor generator started and was run unloaded for 30 minutes. There-fore, the emergency generator was capable of being operated, but was in a re-duced state since it would not have automatically assumed the emergency electrical loads on a loss of site power. This is a deviation from Technical Specification 3.10.a.

Analysis:

At 1515, December 15, while completing the Mechanical Routine Patrol, a machine shop employee discovered the trip light indicating on the emergency generator control panel. The machinist reset the tripped condition, notified the machine shop supervisor and the shif t supervisor, who immediately started the engine and verified it operable. The emergency generator is housed on the third level of the north tower of the facility. Access to the towers is from the outside on the laboratory roof. The emergency generator is only o'oserved when completing the daily meciqnical routine patrol and reactor operations 8401250128 '340113 PDR ADOCK C,5000186 S PDR Y.f COLUMBIA KANSAS CITY ROLLA ST. LOUIS Of L

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routine patrol every four hours. The emergency generator is started and run for thirty minutes. weekly via an auto start exerciser clock normally set for 0800 each Thursday morning. Because of a site electrical outage and nainte-nance work performed the day befort, the exerciser clock was off by one hou" nd twenty five minutes which would indicate that it. started or tried to start

. dt 0925. The generator weekly exercise was not observed by the control room operators. However, because of earlier routine patrol observations, it is felt the trip condition-most likely occurred at that time.

A check of the engine oil level showed it to be full, and cooling water c cto the engine was available. On investigation of the protective trips, the high i _ temperature tripped at 220*F (140*F normal operating temperature), the high RPM overspeed trip occurred at 2150 RPM (1800 RPM normal operating speed), and the low oil pressure tripped .at 10 psig (45 -50 psig normal operating pressure).

All trip values are in the acceptable range.

On investigation of the high temperature sensor, it was discovered that

, the electrical connecting wire spade lug was bent so that it.was nearly grounded.

-Slight pressure on _ the wire would cause a grounding condition to occur. The three protective trips are wired in parallel, and on protective. trip actuation close the ground circuit, energize the protective relay and secure the engine.

. Because the engine starter cranking limiter did not trip, it is suspected that the engine either started and ran, or tried to start; and either by heat ex-

pans' ion or vibration resched the tripped condition observed. The spade lug was repositioned and verified to be free and clear. The previous day, the thermostat on the engine was replaced and then the emergency generator was satisfactorily load tested. The thermostat is located immediately adjacent to the temperature sensor, and it is suspected that the electrical connecting wire spade lug was bent during- this maintenance. Since this incident, the generator has run weekly on its automatic execiser and CP-17, the electrical load compliance test,has been performed.

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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 (HSR), 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 performed indefinitely by the in-pool heat exchanger. The con-trol 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 shutdown condition'due to the failsafe design of these systems;

. i.e. the.redun' dant (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 integrity could not be indefinitely guaranteed if facility electrical power and etergency generator were not available, but the reactor would be shutdown and containment would not be required.

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• Director of Nuclear Reactor Regulation

' January 13, 1984 Page 3 ,

Corrective Action:

'The tripped condition was reset and the emergency generator was manually started and run for 30 minutes. Each protective trip has been tested to en-sure it was operating properly. All-of the trip sensor leads on the emergency generator have been placed so as to prevent an inadvertent grounding.

. The emergency generator has been successfully load tested on the sub-sequent two maintenance days: December 29, 1983 and January 12, 1984. - The cause of. this problem was reviewed with personnel who perform maintenance on 'the emergency generator- to avoid a reoccurrence on this or similar equip-ment.

Sincerely, J.' C. McKibben Reactor Manager Endorsement:

Reviewed and Approved Dm LOQ Don M. Alger l Associate Director JCMK:vs-cc: U. S.' Nuclear Regulatory C'ommission c/o Document Management Branch-James Keppler, Regional Administrator Region Operations - Region III Reactor Advisory Committee

, Reactor Safety Committee

. John H. Tolan, Radiation Safety Officer 1

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