05000263/LER-2001-004
| Docket Number | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2632001004R00 - NRC Website | |
FACILITY NAME(1) DOCKET LER NUMBER (6) PAGE (3)
MONTICELLO NUCLEAR
GENERATING PLANT 05000263 Description On February 16, 2001, while operating at 100% power and during review of an operations manual change, the system engineer recognized space heaters' for the Combustible Gas Control (CGC)2 System recombiner3 reaction chamber and the recombiner blower4 motor-5 had not been tested as required by plant Technical Specifications.
Both trains of CGC Systems were declared inoperable on February 16, 2001 due to a failure to comply with the surveillance requirements of Technical Specification 4.7.E.1.b to perform a resistance to ground test on all heater electrical circuits. A 30-day LCO was entered per Technical Specification 3.7.E.3.
This check had been performed, as specified, for the recombiner main heater circuits, but not for the space heaters in the recombiner enclosure or in the blower motor.
The primary purpose of the space heaters is to prevent excessive moisture buildup in these components. The space heaters are not required for operability, however, they should have been tested based on the Technical Specification requirement (i.e. "all heaters").
Failure to perform the resistance to ground checks of the space heaters did not affect CGC functionality based on the following:
A trickle heater "power on" light on the recombiner provided assurance the space heaters were operating properly.
Cyclic megger checks of the CGC recombiner main heaters and blower motors have shown acceptable results. This demonstrates no excessive degradation of these components.
Semi-annual and cyclic surveillance tests of the CGC Systems have not shown a problem with these components.
The heater circuit resistance to ground surveillance procedures were revised to include the space heaters and were issued on February 22, 2001. These procedures were successfully run on February 23, 2001. Both trains of CGC were declared operable, and the 30-day LCO was exited.
1 EIIS Component Code: EHTR 2 EIIS System Code: BB 3 EIIS Component Code: RCB 4 EIIS Component Code: BLO 5 EIIS Component Code: MO FACILITY NAME(1) DOCKET LER NUMBER (6) PAGE (3)
MONTICELLO NUCLEAR SEQUENTIAL NUMBER
Event Analysis
Analysis of Reportability This event was determined to be reportable as a condition prohibited by the Technical Specifications in accordance with 10 CFR 50.73(a)(2)(i)(B). Technical Surveillance requirement 4.7.E.1.b requires performance of a resistance to ground test on all heater electrical circuits. Contrary to this, only the safety related primary heater elements had been tested.
Safety Significance
The safety significance to this event was low. The safety related primary recombiner heater elements had been tested as required. The space heaters for the recombiner reaction chamber and for the recombiner blower motor had not been tested. At time of discovery, indicator lights on the CGC system control panel indicated the heaters were operating properly. The surveillance test procedures were revised to include the additional heaters, and were successfully run. This event had no impact on the health and safety of the public.
Cause
The cause of this event is a failure to realize that the supporting surveillance procedures did not meet the Technical Specification requirements. The condition is due to a lack of awareness and is cognitive in nature.
Corrective Actions
The heater circuit resistance to ground surveillance procedures were revised to include the space heaters and were issued on February 22, 2001. These procedures were successfully run on February 23, 2001. Both trains of CGC were declared operable at 1539, and the 30-day LCO was exited.
This event and the lessons learned will be the subject of training for the MNGP Engineering Technical staff.
Failed Component Identification None FACILITY NAME(1) DOCKET LER NUMBER (6) PAGE (3)
MONTICELLO NUCLEAR YEAR SEQUENTIAL REVISION
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