ENS 40435
ENS Event | |
|---|---|
11:00 Jan 10, 2004 | |
| Title | Accident Mitigation - Crefs Inoperable |
| Event Description | This Notification is being made pursuant to 10 CFR 50.72 (b)(3)(v)(D).
On January 8, 2004 at 17:35 CST with the Control Room Emergency Filtration System (CREFS) inoperable for planned maintenance, CREFS failed post work testing due to system flow being higher than that allowed by technical specifications. It was originally believed that the failure was connected with the planned maintenance because the system flow rate was initially within the specifications during surveillance testing the previous day. Following system troubleshooting, at 05:00 CST on January 10, 2004, it was determined that the cause of the high flow rates was indeterminate. Based on this evaluation, it could not be determined whether the CREFS failure was independent of planned maintenance or not. Additionally, it is not immediately clear if the high flow condition would result in a loss of safety function. It was therefore conservatively determined that the condition is reportable per 10 CFR 50.72 (b)(3)(v)(D) as a failure of a single train system which could have prevented the fulfillment of a safety function that is needed to mitigate the consequences of an accident. CREFS flow rates are currently within specifications, but the system will remain inoperable until the proper surveillances have been completed. The senior NRC Resident has been notified.
The licensee retracted this event and provided the following information: On January 10, 2004, Cooper Nuclear Station [CNS] made an eight hour event notification report to the NRC pursuant to 10CFR50.72.(b)(3)(v)(D), failure of a single train system which could have prevented the fulfillment of a safety function that is needed to mitigate the consequences of an accident. In particular, testing to restore the Control Room Emergency Filter System (CREFS) to operable status following planned maintenance indicated the flow rate was greater than that allowed by Technical Specifications. It was not known whether the high flow condition would result in a loss of safety function. Flow rate was restored to within Technical Specification Limits and CREFS was returned to operable status on January 11, 2004 at 1803 hours0.0209 days <br />0.501 hours <br />0.00298 weeks <br />6.860415e-4 months <br /> Subsequent evaluation determined: 1. the high flow condition did not impact the system safety functions to maintain the Control Room at a positive pressure with respect to adjoining areas or to isolate the outside air intake on relevant Group isolation signals. 2. the CREFS safety function to limit the radiation exposure to Control Room personnel during any one of the postulated design basis events to within regulatory limits (10CFR50, Appendix A, GDC 19) was maintained during the high flow condition. 3. the design functions of CREFS for the CNS toxic hazards assessment and Fire Protection Program requirements were not affected by the CREFS high flow. The evaluation concluded the safety function of the CREFS during the high flow condition was maintained. Therefore, CNS is retracting this 10CFR50.72 Event Notification. The licensee will notify the NRC Resident Inspector. Notified R4DO (Jeffery Clark) |
| Where | |
|---|---|
Cooper  Nebraska (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:+2.8 h0.117 days <br />0.0167 weeks <br />0.00384 months <br />) | |
| Opened: | Andrew Ohrablo 13:48 Jan 10, 2004 |
| NRC Officer: | Eric Thomas |
| Last Updated: | Jan 15, 2004 |
| 40435 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |