Part 21 Report - 1995-039
PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION I FEBRUARY 1,
1995
Licensee/Facility: Notification:
Niagara Mohawk Power Corp. MR Number: 1-95-0015
Nine Mile Point 2 Date: 02/01/95
Lycoming,New York SRI PC
Dockets: 50-410
BWR/GE-5
Subject: INOPERABLE EMERGENCY DIESEL GENERATORS (UPDATE)
Reportable Event Number: 28304
Discussion:
On January 29, 1995, NMPC commenced a shutdown of Unit 2, and declared an
Unusual Event as a result of both Emergency Diesel Generators (EDG) being
inoperable.
On January 26, 1995, during routine monthly surveillance testing, the
Division I EDG exhibited instability in the engine control system and
tripped when its output circuit breaker was tripped. Troubleshooting of
the control system indicated a problem with the electric governor or the
DC governor power supply (the engines are equipped with both electric and
mechanical governors). The applicable Technical Specification (TS)
limiting condition for operation (LCO) was entered, and the Division II
EDG was tested. No instability was noted during the run of the Div II
EDG.
After replacing the Div I EDG electric governor control card, the Div I
EDG was tested, and still exhibited instability. During subsequent
troubleshooting, excessive temperatures were noted at the base of the
governor, and it was determined that the mechanical governor was
malfunctioning. The mechanical governor was replaced and on retest, the
engine was noted to operate properly, but the governor was still
experiencing excessive temperatures. The Div II EDG was run to obtain
temperature profiles on its governor, and it was determined that its
governor was also experiencing excessive temperatures. At the end of the
test run, the Div II EDG failed to trip due to an air leak on the
pneumatic controls. The Div II EDG was declared inoperable and a reactor
shutdown was commenced (the Div II EDG was INOP, but available).
NMPC has determined that the governor coolers were receiving inadequate
flow from the jacket cooling water system, and has instituted a design
change to rectify the problem. NMPC has also determined that the
manufacturer (Cooper-Bessemer) has used several different jacket cooling
water system designs, and notified the two facilities with similar
systems (Byron and Braidwood) of the problem.
The governor on the Div II EDG has been replaced due to having been
subjected to excessive temperatures. The problem is believed to be
long-term degradation of the governor oil and mechanical components due
to the high temperatures. The governors from both engines will be sent
out for failure analysis.
As of 8:00 a.m. February 1, the modifications on both engines have been
completed, and testing of the Div II EDG is in progress (Div I EDG
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