05000219/LER-2009-002
| Docket Numbersequential Revmonth Day Year Year Month Day Year N/Anumber No. N/A | |
| Event date: | 02-02-2009 |
|---|---|
| Report date: | 03-31-2009 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2192009002R00 - NRC Website | |
Plant Conditions Prior to Event
Event Date:�February 2, 2009� Event Time:�0955 Unit 1 Mode: Shutdown� Power Level: 0%
Description of Event
Note: Energy Industry Identification System (EIIS) codes are identified in the following text in brackets as [XX].
At 0955 on February 2, 2009, a Reactor Water Cleanup System [CE] heat exchanger [HX] outlet high temperature alarm and isolation signal was received. The Reactor Water Cleanup System inlet isolation valve (V-16-1) [ISV] did isolate but the heat exchanger inlet isolation valve (V-16-14) [ISV] failed to close in response to the system high temperature signal. The heat exchanger outlet high temperature isolation function is not a safety function and not a Tech Spec requirement. Later troubleshooting determined that a malfunctioning relay [RLY] prevented V-16-14 isolation from the heat exchanger outlet high temperature signal. During troubleshooting on February 3, 2009, Operations determined that since V-16-14 was a primary containment isolation valve (PCIV), this same malfunctioning relay would have also prevented that safety function and Tech Spec 3.5.A.3 applies. The latter states that with one or more automatic PCIVs inoperable, maintain at least one isolation valve operable in each affected penetration that is open and within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> either (a) restore the inoperable valve to operable status or (b) isolate each affected penetration by use of at least one deactivated automatic valve secured in the isolation position, or (c) isolate each affected penetration by use of at least one closed manual valve or blind flange. The relay problem was corrected and V-16-14 was returned to operable status at 1712 on February 3, 2009. Based on the above, the four-hour Tech Spec requirement was not achieved and this is being reported under 10 CFR 50.73(a)(2)(i)(B).
Analysis of Event:
The safety significance of this occurrence was minimal. The reactor was shutdown, having experienced a unit trip at 2156 on February 1, 2009, due to a failure of the M1A main transformer. The redundant PCIV (V-16-1) was fully operable during the time period when V-16-14 was inoperable.
Cause of Event:
Operations did not recognize the significance of the safety-related and non-safety related shared logic component interface of V-16-14. The safety-related PCIV function of the valve was not initially considered because the operating crew was focused instead on why the actuation of V-16-1 occurred. As a result, an opportunity to have discovered the inoperability prior to February 3, 2009 was missed.
Subsequent troubleshooting determined that high resistance contacts in the malfunctioning relay caused V 16-14 to become inoperable. At that point in time the appropriate Technical Specification actions were taken.
The valve was returned to operable status at 1712 on February 3, 2009.
Corrective Actions:
Operating crews were briefed on this event. The fundamental of a questioning attitude was reinforced with all operators to ensure the proper technical rigor is applied when issues are identified.
Previous Occurrences:
There have been no similar Licensee Event Report events at Oyster Creek in the last three years.
Component Failure Data
Component: RWCU System Trip Control Relay Manufacturer: General Electric Model No.# CR120AD04241AA Cause: High Contact Resistance