ENS 49631
ENS Event | |
|---|---|
23:00 Nov 25, 2013 | |
| Title | Breach Sizes Exceeded for Control Room Envelope |
| Event Description | On December 13, 2013 it was determined that a reportable condition has existed at Columbia Generating Station since 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> [PST] on November 25, 2013.
At 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on November 25, 2013, the Control Room Envelope (CRE) was declared inoperable based on the inability to ensure that the Control Room Emergency Filtration (CREF) System would be able to maintain a positive differential pressure with all areas surrounding the CRE boundary. Columbia does not have the installed instrumentation to directly monitor the differential pressure between the Main Control Room (MCR) and certain areas adjacent to the MCR. The pressure in the adjacent areas is controlled by placing conservative limits on allowed breach size for these adjacent areas. On November 25, 2013, it was identified that the combined breach size associated with several doors in these adjacent spaces resulted in exceeding the allowed limit. Based on exceeding the allowed breach size limit to the adjacent areas, the Control Room Envelope was declared inoperable, and Technical Specification Action Statement 3.7.3.B.1 was entered. An additional breach was discovered on 12/05/13 from a hole in ductwork passing through the cable spreading room, which is one of the adjacent areas to the CRE boundary, and that condition was added to the existing action statement 3.7.3.B.1. These are conditions that could have prevented fulfillment of a safety function of structures that are needed to mitigate the consequences of an accident and are reportable under 10 CFR 50.72(b)(3)(v)(D). The licensee notified the NRC Resident Inspector.
In the case of this event, the Control Room Envelope (CRE) was declared inoperable and Technical Specification Action Statement 3.7.3.B.1 was entered conservatively based upon limited knowledge at the time of discovery. There is no installed differential pressure indication between the CRE and this area adjacent to the Main Control Room (MCR), therefore conservatively this adjacent area is included in the CRE, and leakage is administratively controlled. The leakage between the MCR and the adjacent area included in the CRE exceeded this administrative limit. Testing performed on November 20, 2013, prior to the December 13, 2013 reported events, as well as testing after the event, January 10, 2014, has demonstrated that the leakage identified does not prevent the Control Room Envelope (CRE) from establishing and maintaining the required differential pressure to ensure fulfillment of its required safety function for Control Room Habitability. The ability of the Control Room Emergency Filtration (CREF) system to perform its function of pressurizing and maintaining the Main Control Room positively pressurized with respect to its surroundings was not lost due to the leaking doors and duct specified in the event. Performance of the surveillance without these breaches sealed validated this conclusion. The event described above should not have been reported, as the Control Room Envelope was always operable and capable of fulfilling its safety function with the existing breaches and did not constitute a reportable event as conditions that could have prevented fulfillment of a safety function of structures that are needed to mitigate the consequences of an accident under 10 CFR 50.72(b)(3)(v)(D). The licensee notified the NRC Resident Inspector. Notified the R4DO (Spitzberg). |
| Where | |
|---|---|
Columbia Generating Station  Washington (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+428.73 h17.864 days <br />2.552 weeks <br />0.587 months <br />) | |
| Opened: | Quoc Vo 19:44 Dec 13, 2013 |
| NRC Officer: | Pete Snyder |
| Last Updated: | Jan 21, 2014 |
| 49631 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |