05000482/LER-2015-004
| Docket Number | |
| Event date: | 05-05-2015 |
|---|---|
| Report date: | 09-14-2015 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4822015004R01 - NRC Website | |
PLANT CONDITIONS PRIOR TO THE EVENT
Mode - 1 Power - 100% There were no systems, structures or components (SSC) that were inoperable at the start of the event and contributed to the event.
DESCRIPTION
On April 24, 2015, Wolf Creek Generating Station (WCGS) was in Refueling Outage 20. Procedure STS GT-002, "Ctmt Purge Supply/Exhaust Iso Valve Verification," was performed in preparation from changing from Mode 5 to Mode 4. This procedure closes the containment (Ctmt) shutdown purge valves [EIIS: JM- V] and removes the motive force from them. The motive force is an air supply valve that is locked closed.
During this procedure, the motive force (air supply) for valves GTHZ0007 (Ctmt shutdown Purge Supply Inside Ctmt Iso Butterfly Valve) and GTHZ0009 (Ctmt shutdown Purge Exhaust Outside Ctmt Iso Butterfly Valve) were locked closed and independently verified.
On April 26, 2015, procedure STS KJ-001A, "Integrated D/G and Safeguards Actuation Test — Train A," was being performed. During the pre-test alignment for this procedure, valves GTHZ0007 and GTHZ0009 were required to be placed in the open position. Procedure STS KJ-001A does not realign the air supply valves for the Ctmt shutdown purge valves, so the air supply valves were placed in the Locked Component Log to track their status. On April 26, 2015 at 1215 Central Daylight Time (CDT), the air supply valves for valves GTHZ0007 and GTHZ0009 were opened and documented in the Locked Component Log. During the post-test alignment of procedure STS KJ-001A, valves GTHZ0007 and GTHZ0009 were closed. But the air supply for valves GTHZ0007 and GTHZ0009 were not locked closed since procedure STS KJ-001A did not address them. The restoration section of procedure STS KJ-001A was performed by a different crew than initially opened the valves and they did not recognize the air supply valves were being controlled by the Locked Component Log.
On April 28, 2015, at 0144 CDT, the plant entered Mode 4. As part of the Mode 4 preparations, procedure AP 21G-001, "Control of Locked Component Status," was reviewed per procedure GEN 00-002, "Cold Shutdown to Hot Standby," step E.24. This review did not find the air supply valves that were required to be locked closed before entry into Mode 4, as they had been signed off in procedure AP 21G-001 as locked closed on April 24, 2015. The Locked Component Log was not reviewed immediately prior to the mode change.
On May 5, 2015, the Locked Component Log was being consolidated and it was discovered that the air supply valves for GTHZ0007 and GTHZ0009 still indicated they were in the open position. On May 5, 2015, at 1000 CDT, Limiting Condition for Operation (LCO) 3.6.3 was declared not met and Condition A entered for the air supply valves not being in the locked closed position. On May 5, 2015, at 1120 CDT, Condition A of LCO 3.6.3 was exited when both air supply valves were verified to be locked closed.
REPORTABILITY
Technical Specification (TS) 3.6.3, "Containment Isolation Valves," requires each containment isolation valve shall be operable in Modes 1, 2, 3, and 4. To be operable, valves GTHZ0007 and GTHZ0009 must be closed with the motive force removed. TS LCO 3.6.3 was determined to be not met on May 5, 2015 at 1000 CDT when it was discovered that the motive force for valves GTHZ0007 and GTHZ0009 was not removed. TS 3.6.3 Condition A, Required Action A.1, requires the affected penetration flow path to be isolated within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Investigation showed that the air supply valves were not locked closed from April 28, 2015, at 0144 CDT, when the plant entered Mode 4, through May 5, 2015, at 1120 CDT.
This event is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B) as an operation or condition which was prohibited by TS, when it was determined that the Conditions and Required Actions of LCO 3.6.3 and LCO 3.0.4 were not met for valves GTHZ0007 and GTHZ0009.
CAUSE
Decisions to only track components listed in the manual Locked Component Log during plant start-up, allowed a mode change with components out of position. Components required to be locked closed for mode change, were repositioned to open by a different procedure after they had been formally verified for the mode change, without ensuring a new tracking mechanism was in place. The procedure STS KJ-001A, which required the Ctmt shutdown purge valves to be open in order to check the auto closure function, did not contain steps to open them or verify restoration of the air lineup.
CORRECTIVE ACTIONS
On May 5, 2015, at 1120 CDT, the air supply valves for GTHZ0007 and GTHZ0009 were locked closed and verified, removing the motive force.
Procedure AP 21G-001 has been revised to ensure an Equipment Out of Service Log (EOL) entry is made for components which are required to be locked by Technical Specifications.
SAFETY SIGNIFICANCE
The safety significance of this event was low. Though the motive force was not removed, valves GTHZ0007 and GTHZ0009 were closed in their safeguards position. In addition valves GTHZ0007 and GTHZ0009 have redundant valves in series that were closed with the motive force removed. Each penetration flow path had one operable valve that was closed with its motive force removed.
OPERATING EXPERIENCE/PREVIOUS EVENTS
None