05000354/LER-2005-004
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. | |
| Event date: | 05-09-2005 |
|---|---|
| Report date: | 07-08-2005 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| 3542005004R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric — Boiling Water Reactor (BWR/4) Chilled Water System {KM}* Control Room Emergency Filtration {VI}
- Energy Industry Identification System {EIIS} codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF OCCURRENCE
Event Date: May 9, 2005 Discovery Date: May 12, 2005
CONDITIONS PRIOR TO OCCURRENCE
Hope Creek was in operational condition 1 with reactor power at 100%. During the period that the 'A' control room emergency filtration (CREF) train was determined to be inoperable, the 'B' CREF train was out of service for maintenance. There was no other equipment out of service that impacted this event.
DESCRIPTION OF OCCURRENCE
On May 12, 2005, at approximately 1020 hours0.0118 days <br />0.283 hours <br />0.00169 weeks <br />3.8811e-4 months <br />, plant personnel reported that the guide vane pivot arm for the 1AK400 chiller {KM/CHU} appeared to have slipped. The 1AK400 chiller supports the 'A' CREF train {VI}. At that time, the 1BK400 chiller, which supports the 'B' CREF train, was removed from service for maintenance. At approximately 2004 hours0.0232 days <br />0.557 hours <br />0.00331 weeks <br />7.62522e-4 months <br />, the 1AK400 was stopped to investigate. Report from the field identified minor slippage but the guide vanes appeared to be closed. At 2008 hours0.0232 days <br />0.558 hours <br />0.00332 weeks <br />7.64044e-4 months <br />, the 1AK400 was placed in service to verify normal start capability.. Based upon these actions, plant personnel assessed that the 1AK400 was operable but degraded with the guide vane pivot arm slippage on May 12, 2005.
At 2118 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.05899e-4 months <br />, the 'B" CREF train was returned to service. At 2150 hours0.0249 days <br />0.597 hours <br />0.00355 weeks <br />8.18075e-4 months <br />, the 1AK400 chiller was removed from service to commence repair activities. Maintenance on the 1AK400 chiller was completed at 2213 hours0.0256 days <br />0.615 hours <br />0.00366 weeks <br />8.420465e-4 months <br /> and the 'A' CREF train was restored to operable status at 2253 hours0.0261 days <br />0.626 hours <br />0.00373 weeks <br />8.572665e-4 months <br />.
Subsequent to the 1AK400 chiller being declared operable, a follow up operability assessment was performed several weeks later that concluded with the guide vane pivot arm slippage, the 1AK400 chiller was not capable of performing its design function of maintaining temperatures in the control room envelope. A review of plant data determined that the guide vane slippage for the 1AK400 chiller most likely started at approximately 0950 hours0.011 days <br />0.264 hours <br />0.00157 weeks <br />3.61475e-4 months <br /> on May 9, 2005. Therefore, the 'A' CREF train was inoperable from May 9 to May 12. With the 'B' CREF train inoperable during this same time period, Technical Specification (TS) 3.0.3 would have been applicable for having both trains of CREF inoperable. TS 3.0.3 requires that within one hour action shall be initiated to place the unit in an operational condition in which the Specification does not apply. Hope Creek was in operation condition 1 through the period of time both trains of CREF were subsequently determined to be inoperable.
This event is being reported in accordance with 10CFR50.73(a)(2)(i)(B), as "a condition which was prohibited by technical specifications," and 10CFR50.73(a)(2)(v)(D), "any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to: mitigate the consequences of an accident.
The slippage of the 1AK400 guide vane actuator arm was the result of loose set screws on the drive arm and vane actuating arm. The cause of the loose set screws was determined to be the inadequate use of both internal and external operating experience. Improved practices for setting fastener parts/devices were not incorporated into maintenance procedures, work instructions or maintenance training.
PREVIOUS OCCURRENCES
A review of LERs at Hope Creek for the previous two years was performed to identify prior similar occurrences.
(CR) envelope breach", dated January 12, 2003, was reviewed for applicability. The event in LER 354/03-002-00 was attributed to a ductwork access hatch opening causing both trains of CREF to be inoperable. The corrective actions associated with that LER would not have prevented this occurrence.
involved the 'B' CREF train. The failure mechanism related to this LER was a float which became disengaged from the float arm due to improper torquing of the ball arm clamp. Corrective actions were specific to this event and would not have prevented the current event.
involved the BK400 chiller. The BK400 chiller was declared inoperable due to high evaporator pressure. The cause for the high evaporator pressure was determined to be the inability of the guide vane to properly modulate due to the pivot arm set screws not being engaged firmly enough on the shaft to prevent slippage. The corrective action consisted of revising the maintenance procedure to add guidance for dimpling the guide vane shaft to engage the setscrews in the shaft to prevent slippage. This action did not address the securing of the setscrews to prevent loosening and therefore would not have prevented the current event.
SAFETY CONSEQUENCES AND IMPLICATIONS
Although both the 'A' and 'B' CREF trains were inoperable during period from May 9 to 12, 2005, the 'A' CREF train was capable of pressurizing and filtering the control room atmosphere in the event of an accident. However, the follow up assessment determined that the 'A' CREF train was not capable of removing the heat loads from the control room envelope following a postulated design basis accident (DBA). An engineering assessment determined that based on the 'A' chiller's degraded performance, the 'A' CREF train would not have been able to maintain temperature below 85°F following a postulated DBA. As a result of increasing temperatures in the control room, operators would have initiated actions to restore the 'B' chiller to an operable status to provide the necessary cooling to the control room envelope.
A review of this event determined that a Safety System Functional Failure (SSFF) did occur as defined in Nuclear Energy Institute (NEI) 99-02. Since the capability to mitigate the consequences of an accident was impacted by having both trains of CREF inoperable, this is an NEI 99-02 SSFF.
NRC FORM.,366A U.S. NUCLEAR REGULATORY COMMISSION (1-2001) DOCKET (2)FACILITY NAME (1) LER NUMBER (6) PAGE (3)
CORRECTIVE ACTION
1. Corrective maintenance was performed on the 1AK400 chiller. The guide vane was reassembled and the set screws were properly secured.
2. Maintenance procedure SH.MD-GP.ZZ-0022 is being revised to incorporate industry guidance/practices. This procedure change will address the use of double verification of tightness/torque of fasteners and the use of chemical materials where appropriate to prevent fasteners from loosening.
3. Lessons learned from this event were provided to maintenance personnel by a "CAP ALERT" document distributed on June 22, 2005.
4. This event is being assessed for changes to the maintenance technician training program.
The above actions are being tracked in accordance with PSEG's corrective action program.
COMMITMENTS
This LER contains no commitments.