05000354/LER-2004-008
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. | |
| Event date: | 8-29-2004 |
|---|---|
| Report date: | 10-27-2004 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material |
| 3542004008R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric — Boiling Water Reactor (BWR/4) Leak Monitoring System {IJ/DEf}* *Energy Industry Identification System {EIIS} codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF OCCURRENCE
Event Date: August 29, 2004 Discovery Date: August 29, 2004
CONDITIONS PRIOR TO OCCURRENCE
Hope Creek was in Operating Condition 1 (Power Operation), at the time of discovery. At the time of the Nuclear Measurement and Control (NUMAC) analog card failure, the inboard isolation valve was in an open condition with power removed to perform a channel functional test. All required structures, systems or components were operable at the start of this event.
DESCRIPTION OF OCCURRENCE
On 08/29/04 at 1928 hours0.0223 days <br />0.536 hours <br />0.00319 weeks <br />7.33604e-4 months <br />, an alarm was received in the control room indicating the Reactor Water Cleanup (RWCU) high differential flow isolation channel for the outboard RWCU supply isolation valve was inoperable. The alarm was the result of the Leak Detection System (LDS) {IJ/DET} initiating a system failure signal. At the time, the functional test for the inboard RWCU high differential flow isolation channel was being performed. During the channel functional test, power to the inboard isolation valve was removed to permit continued RWCU system operation while the isolation function was tested. With the outboard isolation actuation channel inoperable and the inboard isolation valve deenergized in the open position, a break in the RWCU system may not have resulted in a required isolation. This condition could have resulted in the unintended release of radioactive material.
The condition was caused by the coincidental failure of a NUMAC analog card and the channel functional test being performed on the other isolation valve. The NUMAC system performs a continuous diagnostic. The cycle of the self test is approximately one minute. Upon receiving the leak detection system trouble alarm, the RWCU system was removed from service to comply with Technical Specification 3.3.2-1, action 23, which requires closure of the affected isolation valves within one hour.
Corrective maintenance included removal and replacement of the NUMAC card. The system was tested successfully and declared operable. The failure of the component was due to a random failure event.
The Technical Specification was entered as required and the system was returned to operable condition within the allowed outage time.
This event is being reported in accordance with 10CFR50.73 (a) (2) (v) (C), any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material.
- The inability to isolate the RWCU system was caused by the coincidental failure of the NUMAC analog circuit card and the system functional test being performed on the other isolation valve. The cause of the failure of the NUMAC analog card was due to a random component failure on the card.
PREVIOUS OCCURRENCES
A review of LERs for the two prior years at Hope Creek and Salem was performed to determine if similar event had occurred. There were no previous occurrences of this type report during that period.
SAFETY CONSEQUENCES AND IMPLICATIONS
There were no safety consequences associated with this event since there was no unmonitored or unplanned radiological effluent release associated with this event. Operations isolated the RWCU system within one hour from the failure of the NUMAC circuit card.
A review of this event determined that a Safety System Functional Failure (SSFF) as defined in Nuclear Energy Institute (NEI) 99-02 has occurred. With the outboard isolation actuation channel inoperable and the inboard isolation valve deenergized in the open position, a break in the RWCU system may not have resulted in a required isolation. This condition could have resulted in the unintended release of radioactive material.
CORRECTIVE ACTION
Corrective actions included:
- Isolated the RWCU system within one hour;
- Determined that a component in the differential flow monitoring system had failed;
- Replaced the failed component and performed a system retest;
- Preventive maintenance for the NUMAC drawers will be established.
COMMITMENTS
This LER contains no commitments.