05000277/LER-2004-002
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
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| 2772004002R00 - NRC Website | |
Unit Conditions Prior to the Event Unit 2 was in Mode 1 and operating at approximately 99% rated thermal power in end of cycle coast down when the Technical Specification non-compliance existed on 9/7/04 to 9/8/04. There were no structures, systems or components out of service that contributed to this event.
Description of the Event
On 9/23/04, during planned refueling outage maintenance activities, maintenance technicians discovered foreign material (i.e. a bolt) in the valve body of the High Pressure Coolant Injection (HPCI) (EIIS: BJ) Turbine Exhaust Drain Line Inboard Isolation Air-Operated Valve (A0-137). It was subsequently determined that this foreign material was the cause of a previously identified failure of this valve (EIIS: ISV) to close that was discovered on 9/8/04 at approximately 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> during the performance of routine surveillance testing.
During the performance of the surveillance testing on 9/8/04, the AO-137 had split indication in the Main Control Room (MCR) after receiving a simulated high steam line flow isolation signal. The redundant valve AO-138 did indicate fully closed in the MCR. Subsequent troubleshooting resulted in several successful strokes of the AO-137 valve and the valve was able to be fully closed. In accordance with Technical Specification 3.6.1.3, Primary Containment Isolation Valves (PCIVs), the affected penetration flow path was isolated within the required completion time. Because of the unsuccessful surveillance of the AO-137 on 9/8/04, the valve was considered inoperable pending the results of maintenance that was to be performed on 9/23/04 during the refueling outage. The PCIV Technical Specification 3.6.1.3 requirement became no longer applicable on 9/15/04 when the plant reached Mode 4 (Primary Containment was no longer required to be operable) as a result of a planned shutdown for the refueling outage.
Further investigation determined that the foreign material in the HPCI system piping was originally identified to be lost during previous refueling outage maintenance activities performed in September 2002. The evaluation performed for the lost material did not result in the expecation that the material would travel to the A0-137.
However, the bolt migrated to the AO-137 valve body during a HPCI system run. The previous HPCI system run prior to the discovery of the valve seating concern was on 9/7/04 at approximately 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />. Therefore, this is considered the time that the foreign material entered the valve seat area and therefore the AO-137 is considered to have become inoperable at that time. Because the Technical Specification 4-hour Required Action to isolate the penetration was not performed until 9/08/04 by 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />, this event was determined to be a condition prohibited by the Technical Specifications in accordance with 10 CFR 50.73 (a)(2)(i)(B).
Analysis of the Event
There were no actual safety consequences associated with this event. Primary Containment Isolation valve A0-137 was considered as Technical Specifications inoperable between 9/07/04 (the date when the foreign material is assumed to have entered the A0-137 valve seating area during a routine HPCI surveillance run) and when the plant reached Mode 4 (Primary Containment was no longer required to be operable) as a result of a planned shutdown for the refueling outage.
The A0-137 valve is a PCIV located on the drain line off the HPCI turbine exhaust line, The function of the valve is to allow for controlled drainage of any condensation that may collect in the HPCI Turbine exhaust line. The valve has a safety function as a PCIV since the drain line connects to the Suppression Pool (i.e. Primary Containment). During the period of non-compliance, the redundant isolation valves were operable. Therefore, the Primary Containment isolation safety function was met throughout the period of non-compliance.
This event was not determined to be risk significant.
Cause of the Event
The cause of the failure of the valve to properly close was due to foreign material (i.e. bolt) found in the body of the valve. Further investigation determined that the foreign material in the HPCI system piping was originally identified to be lost during previous refueling outage maintenance activities performed in September 2002. The evaluation performed for the lost material did not result in the expecation that the material would travel to the A0-137. However, the bolt migrated to the A0-137 valve body during HPCI system operation. It was determined that the foreign material was from the HPCI turbine reversing chamber hardware and was in the system prior to an inspection conducted during September 2002 refueling activities. At that time, retrieval efforts were unsuccessful in locating the identified missing material.
Corrective Actions
The bolt was removed and the other areas of the HPCI turbine piping system were inspected for additional foreign material. The inspections included various search techniques including the removal of components, boroscopic inspections and breaching of piping. No additional foreign material was identified. The appropriate maintenance was performed on A0-137 valve internals. The valve was retested successfully and subsequently returned to service.
Additional corrective actions are being evaluated in accordance with the corrective action program.
Previous Similar Occurrences There were no previous similar LERs identified involving HPCI Primary Containment Isolation valves unable to close due to undetected foreign material.