05000348/LER-2010-003
| Docket Numbersequential Revmonth Day Year Year Month Oay Yearnumber No. 05000 | |
| Event date: | 08-15-2010 |
|---|---|
| Report date: | 09-24-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3482010003R00 - NRC Website | |
Westinghouse -- Pressurized Water Reactor Energy Industry Identification Codes are identified in the text as [XX]
Description of Event
On August 15, 2010 at 0400, Unit 1 exceeded the Technical Specification (TS) time allowed to be in entered TS 3.6.5 required action for Containment Air Temperature on August 14, 2010 at 1400 due to the heating effects caused by closing Service Water (SW) from Reactor Coolant Pump (RCP) motor air cooler Motor Operated Valve (MOV) 3134 [BI]. Containment isolation was required by TS 3.6.3, Containment Isolation Valves, when during surveillance testing, MOV 3134 failed to indicate fully closed by remote indication. On August 14, 2010 at 2200, containment air temperature had not been restored and Unit 1 entered the 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> required action to be in Mode 3. A controlled ramp down to Mode 3 was begun on August 15, 2010 at 0045 but was halted when an 18 hour2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> Notice of Enforcement Discretion (NOED) was granted at approximately 0057.
When stroked closed, MOV 3134 exhibited dual indication from the control room; however the local indication showed the valve had actually closed. Local leak rate testing (LLRT) verified the condition of the valve to be closed and operable as a containment penetration isolation boundary.
Once MOV 3134 was verified to be operable, it was unlsolated and opened on August 15, 2010 at 0800. Containment temperature was restored to within TS limits on August 15, 2010 at 0823 and the NOED was exited.
In accordance with 10 CFR 50.72(b)(2)(i) for initiation of a TS required shutdown on Unit 1, a four hour non-emergency report was issued on August 15, 2010 at 0315, Event Notification number 46175.
Cause of Event
During surveillance testing, MOV 3134 failed to indicate fully closed by remote indication and required isolation by TS 3.6.3. Isolation of this penetration flow path resulted in reduced cooling of the RCP motor exhaust air. This caused containment average air temperature to rise approximately 3 degrees F and exceed the TS 3.6.5 LCO limit. Although MOV 3134 indicated closed by local indication, closure and operability could not be verified by LLRT before exceeding the TS shutdown time for high containment average temperature.
Safety Assessment This event had no adverse effect on the safety and health of the public. Although containment average temperature was slightly above the 120 degrees F TS limit; based on the Final Safety Analysis Report, a containment temperature up to 127 degrees F would not impact containment integrity or recirculation capability. The NRC determined that the requested NOED was necessary to avoid unnecessary transients as a result of compliance with the license condition and thus, minimize the potential safety consequences and operational risks.
The 18 hour2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> NOED commenced on August 14, 2010 at 2200 and contained two stipulations:
- If containment average temperature exceeds 122 degrees F, a controlled shutdown will be initiated.
Neither stipulation was challenged during the NOED period. Containment average temperature peaked at approximately 120.5 degrees F before MOV 3134 was opened and temperature decreased to below the TS limit.
The following compensatory measures were established to maintain containment average temperature below that specified in the NOED:
- Running containment mini-purge continuously
- Aligning Emergency SW to the containment coolers
- Running the containment dome recirculation fans in high speed No safety system functional failures occurred. There were no other TS required actions in effect.
There was no switchyard or grid activity being conducted or scheduled that would threaten grid stability or off-site power. In addition, no storms or high wind conditions were forecasted or occurred for the duration of the enforcement discretion. Therefore, the safety and health of the public was not adversely affected.
Corrective Action An LLRT was performed to confirm closure and operability of MOV 3134 on August 15, 2010. MOV 3134 was subsequently cycled open, closed, and open with no further anomalies.
An enhanced Apparent Cause Determination including an extent of condition was performed and corrective actions developed for the intermittent position indication on MOV 3134. The causal analysis identified that the shaft bearing material was not optimum for the SW application and change out to bronze bearings is scheduled for this and five other MOVs.
Additional Information
Previous Similar Events:
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