05000397/LER-2012-003
| Docket Number07 24 2012 2012 -003 -00 09 20 2012 05000 | |
| Event date: | 07-24-2012 |
|---|---|
| Report date: | 09-20-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| Initial Reporting | |
| ENS 48131 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material |
| 3972012003R00 - NRC Website | |
Plant Conditions:
At the time of event, the plant was operating in Mode 1 at 100% power. There were no structures, systems or components that were inoperable at the start of the event that contributed to the event. SGT Train B was out of service for planned maintenance and work performed as part of the maintenance contributed to the initiation of this event.
Event Description:
On July 24, 2012, at 11:22, the main control Room received both DIV 1 and DIV 2 RB HVAC board R trouble alarms indicating high secondary containment pressure and that both reactor building fans were off. In response to the alarms, operations started ROA-FN-1A and REA-FN-1A to recover reactor building ventilation.
Plant data shows that for approximately 4 and a half minutes the secondary containment vacuum was less than -0.25 inches water vacuum.
The fans were noted to have tripped during maintenance on Standby Gas Treatment (SGT) system with alarms coming in shortly after reconnecting leads to a portion of the SGT system. No deficient maintenance practices were identified however it is possible that the work being performed caused the fans to trip.
This event is reportable as an event that could have prevented fulfillment of a safety function needed to control the release of radiation and mitigate the consequences of an accident per 10CFR50.73(a)(2)(v)(C) and 10CFR50.73(a)(2)(v)(D). An 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> event notification (48131) was previously made to the NRC based on meeting the reporting criteria of 10CFR50.72(b)(3)(v)(C) and 10CFR50.72(b)(3)(v)(D).
Extent of Condition:
Extent of condition is limited to the SGT system since it is the only safety related cross divisional system at Columbia. Normal maintenance work control practices ensure operability and functionality is maintained by components out of scope of the division being worked on. The preventive maintenance work orders for both A and B SGT loop calibrations have been revised to provide information that the ROA/REA fans need to be lined up on the correct division to eliminate future trips.
Immediate Corrective Action:
Maintenance planning revised all SGT preventive maintenance tasks, to ensure SGT loop logic and ROA/REA fan trip logic conflicts are clearly defined.
Cause:
The cause of the trip was that work control does not have guidance on swapping to redundant lineups when taking systems out of service.
Operating Experience & Previous Occurrences:
Searches in the INPO database and the Energy Northwest Corrective Action Program were not able to identify related issues or previous occurrences of this event. No specific internal or external related operating experience could be found that related to this issue. As a result of the searches performed there were no missed opportunities identified that could have prevented the event.
Further Corrective Actions:
Operations work control
- rocedures will be revised to ensure that 0 erations reviews redundant lineups when 26158 R5 �NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION
CONTINUATION SHEET
work is to be performed on SGT or Reactor building fan. In addition, the Instrument Master Data Sheet for SGT is being revised to add a note about reactor building fan trip risk. An Operations support task and a note on all maintenance work orders related to SGT/RBHVAC work that will ensure a swap occurs to the alternate ROA/REA fans prior to commencing work are being added.
Assessment of Safety Consequences
This event resulted in an unplanned entry into TS 3.6.4.1 condition A. Secondary containment pressure was more than -0.25 inches water gauge for approximately four and a half minutes. The peak pressure was 0.06 inches water gauge. While the actual pressure is beyond the range allowed by technical specifications, the purpose of maintaining slight vacuum is to assist in drawdown of secondary containment to support accident response of the SGT system. Existing engineering analysis demonstrates that for this event, the drawdown credited in accident response could have been attained using the operational A train of SGT, thus there were no potential safety consequences. There were no actual safety consequences associated with this event since no events involving radiological hazards were experienced during the work activities.
Energy Industry Identification System (EIiS) Information El IS codes are bracketed [ ] where applicable in the narrative.
26158 R5