05000263/LER-2014-005
| Monticello Nuclear Generating Plant | |
| Event date: | 03-20-2014 |
|---|---|
| Report date: | 05-19-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| Initial Reporting | |
| ENS 49938 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition |
| 2632014005R00 - NRC Website | |
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EVENT DESCRIPTION
On March 20, 2014, the Monticello Nuclear Generating Plant was in Mode 1 at approximately 93% power.
At 1020 hours0.0118 days <br />0.283 hours <br />0.00169 weeks <br />3.8811e-4 months <br />, during performance of the semi-annual fire door inspection, door-410B [DR] did not automatically close and latch as required, as a result of insufficient closing force. Door-410B is an Appendix R fire door that is required for divisional separation of safe shutdown equipment, specifically reactor level instrumentation. In this condition, divisional separation could not be assured in the event of a fire. A continuous fire watch was established and repairs were made.
At approximately 1135 hours0.0131 days <br />0.315 hours <br />0.00188 weeks <br />4.318675e-4 months <br />, door-410B repair was completed by lubrication of the door latch and adjusting the door closer. The door was then satisfactorily tested and declared functional. Therefore, the door was non-functional for approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 15 minutes.
There were no other structures, systems, or components inoperable at the start of the event that contributed to the event. Door-410B also has a High Energy Line Break function which is to remain open; this function was not compromised during this event.
EVENT ANALYSIS
The condition is reportable to the NRC in accordance with 10 CFR 50.73(a)(2)(ii)(B) for placing the plant in an unanalyzed condition that significantly degrades plant safety. The condition was reported to the NRC on March 20, 2014, in event notification 49938 in accordance with 10 CFR 50.72(b)(3)(ii)(B).
SAFETY SIGNIFICANCE
The Appendix R specified function for door-410B is to close and latch during a fire event to provide divisional separation. Door-410B is normally open and is designed to close in the event of a fire to create a fire barrier between the east and west side of the reactor building. The door was satisfactorily tested during the previous semi-annual fire door inspection on September 18, 2013.
Since the last successful testing of the door's closing function, the fire detection systems and manual suppression capability for the impacted fire zones have been functional with no fire impairments issued.
The fire detection system alarms in the Main Control Room which would result in prompt fire brigade response and fire extinguishment. Manual suppression capability consists of fire hose stations and extinguishers.
CAUSE
The cause of door-410B failure to close and latch during performance of the surveillance was determined to be insufficient closing force.
CORRECTIVE ACTION
Immediate corrective actions were to repair door-410B by adjusting the door closer and lubrication of the door latch. The door was then satisfactorily tested and declared functional. Long term corrective actions include door closer force adjustments on a periodic basis.
PREVIOUS SIMILAR EVENTS
There were no previous similar licensee event reports in the past three years. On March 22, 2010, door-410B did not automatically latch during performance of fire door inspections and was declared non- functional. The door closer was adjusted and the door was returned to functional status.
ADDITIONAL INFORMATION
Door manufacturer: WM. J. Perkinson Co., INC