ML20064L134
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UNITED STATES
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9, AE00/E212 NUCLEAR REGULATORY COMMISSION 7
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'%,,,, /,a FEB 2 41982 F
MEMORANDUM FOR:
Richard H. Yo11mer, Director j
Division of Engineering i
Office of Nuclear Reactor Regulation Roger J. Mattson, Director Division of Systems Integration f%
office of Nuclear Reactor Regulation
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FROM:
Carlyle Michelton, Director Office for Analysis and Evaluation of Operational Data
SUBJECT:
SPURIOUS TRIP OF THE GENERATOR LOCK 0UT RELAY ASSOCIATED WITH A DIESEL GENERATOR UNIT
References:
(1) Arkansas Power and Light Company, " Licensee Event Report: 81-014/01T-0 dated December 16,1981," Plant Unit: Arkansas Nuclear One Unit Number 1, Cocket No.:
50-313 l
(2) Arkansas Power and Light. Company, " Licensee Event Report: 81-014/01T-1 dated December 31,1981," Plant-Unit Arkansas One Unit Number 1, Docket No: 50-313 The reference license event reports provide a description and also other infonnation relating to an event which cccurred at Arkansas Nuclear One (Unit Number 1) involving the generator lockout relay associated with a diesel generator unit.
On November 19, 1981 while operating at approximately 90% of full power, an alann actuated alerting operations personnel that the generator lockout relay associated with.the Number 1 diesel generator unit had tripped. Further, investigation into this occurrence by the licensee revealed that the C 3
phase high speed differential relay had activated and this action in turn caused a generator lockout relay to trip even though the associated diesel generator unit was not operating at the time. A walk-through by persons in the area revealed that the diesel generator exciter cubicle door may have been opened and reclosed, possibly with sufficient force to cause spurious operation of this differential relay (General Electric Model 12 CFD12BIA).
Subsequent investigation demonstrated sensitivity of this relay to mechanical shock.
In addition, a preliminary result of this investigation concluded that this relay did not meet seismic qualifications as applied in this design when the diesel generator unit is in the standby mode. This conclusion was based on a review of the seismic qualifications for this relay which indicated that this quali,fication was perfonned with the relay in an energized state;but no such qualification was perfonned with the relay in a de-energized state.
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? l Multiple Addressees I
i Based on our review of the referenced _ licensee event reports we believe there is i
a need to explicitly verify that the seismic qualification for all protective devices used in the control and protection circuitry for diesel generator units has been acceptably performed with these devices in their energized, de-energized, This verification is recommended since for a tripped and non-tripped states.
given device, details relating to its specific application may not have beenWe also believe t factored into the seismic qualification of that device.
the verification of seismic qualification of these devices, special consideration should be given to those designs which use solid state circuitry, since this type of circuitry is more susceptible to spurious actuations due to normal or abnormal levels of in-plant vibrations and any associated electromag interference.
failures of diesel generator units during and following a seismic event.
Further, based on our review we propose, for your consideration, that the design of the diesel generator system in a nuclear plant should include provisions to preclude spurious operation of protective devices from diesel generator is not in operation.
For example, in appropriate permissive interlocks in the protective circuitry.the abo an engine speed relay interlock to preclude spurious operation of the generator differential relay from actuating the lockout when the diesel engine is not
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running.
Carlyle Michelson, Director Office for Analysis and Evaluation of Operational Data cc:
H. Denton, NRR D. Ei senhut, NRR G. Lainas, NRR Z. Rosztoczy, NRR M. Srinivasan, NRR l
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