05000325/LER-2012-006
| Brunswick Steam Electric Plant (Bsep), Unit 1 | |
| Event date: | 09-19-2012 |
|---|---|
| Report date: | 11-19-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3252012006R00 - NRC Website | |
Energy. Industry Identification System (EIIS) codes are identified in the text as [XX].
Introduction Initial Conditions At the time of the event, Unit 1 was in Mode 4, at 0 percent of rated thermal power (RTP). The Emergency Diesel Generators (EDGs) [EK], offsite power, and required Emergency Core Cooling systems were operable.
Reportability Criteria Secondary containment [NG] operability was not maintained during an Operation With a Potential for Draining the Reactor Vessel (OPDRV) activity and Required Action C.2 of Technical Specification (TS) 3.6.4.1, "Secondary Containment," was not completed. This condition is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as operation prohibited by the plant's TSs.
Event Description
On September 15, 2012, Unit 1 began a forced outage to replace a 1B recirculation pump seal. On September 17, 2012, with the unit in Mode 4, a clearance was hung on the 1B recirculation loop [AD] and the recirculation pump suction and discharge isolation valves were isolated to provide the reactor coolant system (RCS) boundary. After the valves were isolated, there was approximately 10 gpm leakage by the seats. In order to set working conditions in the pump, a drain path was established to drywell floor drains to maintain the pump assembly water level high enough to provide radiation shielding yet low enough to facilitate the seal replacement.
Subsequently, on September 19, 2012, at approximately 0330 hours0.00382 days <br />0.0917 hours <br />5.456349e-4 weeks <br />1.25565e-4 months <br /> Eastern Daylight Time (EDT), secondary containment [NG] airlock doors were opened to facilitate additional ventilation flow to the reactor building, thereby improving working conditions. Secondary containment was considered available, but not operable. The decision to open the secondary containment airlock doors was based on BSEP established guidance that leakage through mechanical joints (e.g., valve or flange packing leaks, seat leakage through an isolation valve, flange leakage) is not an OPDRV. The NRC Senior Resident Inspector questioned this position and the NRC concluded that the activity did constitute an OPDRV. Secondary containment was restored to operable status at approximately 2120 hours0.0245 days <br />0.589 hours <br />0.00351 weeks <br />8.0666e-4 months <br /> EDT on September 19, 2012.
Event Cause The cause of this event was inappropriate application of guidance in plant procedure 001-01.01, "BNP Conduct of Operations Supplement." When BSEP implemented the guidance of EGM 11-003, "Enforcement Guidance Memorandum on Dispositioning Boiling Water Reactor Licensee Noncompliance with Technical Specification Containment Requirements During Operations With a Potential for Draining the Reactor Vessel," dated October 4, 2011, an OPDRV was defined as any activity that could potentially Event Cause (continued) result in draining or siphoning the reactor vessel below the top of the fuel, without taking credit for mitigating measures. This is consistent with EGM 11-003. However, the procedure also included a qualifying statement that leakage through mechanical joints (e.g., valve or flange packing leaks, seat leakage through an isolation valve, flange leakage, etc.) is not an OPDRV. This guidance was inappropriately used to conclude that the conditions established to perform the 1B recirculation pump seal replacement were not an OPDRV.
Safety Assessment The safety significance of this condition is considered minimal. At the time of the event, Unit 1 was in Mode 4, at 0 percent of RTP. The EDGs, offsite power, and required Emergency Core Cooling systems were operable. As such, the available makeup capability far exceeded the 10 gpm valve seal leakage rate.
Corrective Actions
The following corrective actions were completed.
- Secondary containment was restored to operable status at approximately 2120 hours0.0245 days <br />0.589 hours <br />0.00351 weeks <br />8.0666e-4 months <br /> EDT on September 19, 2012.
- A standing instruction was issued to ensure secondary containment remained operable during work activities associated with 1B and 1A reactor recirculation pump seals.
The following corrective action is planned.
- Plant procedure 001-01.01 will be revised to delineate conditions of an OPDRV and differentiate between implementation of EGM 11-003 and other conditions. This revision is currently planned to be completed by February 28, 2013, prior to the next scheduled outage for either unit.
Previous Similar Events
A review of LERs and corrective action program condition reports identified the following previous similar occurrence.
- LER 1-2012-002, dated May 12, 2012, reported planned implementation of the guidance of EGM 11-003, "Enforcement Guidance Memorandum on Dispositioning Boiling Water Reactor Licensee Noncompliance with Technical Specification Containment Requirements During Operations With a Potential for Draining the Reactor Vessel," dated October 4, 2011. Since this was a preplanned activity, there were no corrective actions that could have prevented the event discussed in LER 1-2012-006.
Commitments No regulatory commitments are contained in this report.