ENS 44671
ENS Event | |
|---|---|
18:30 Nov 20, 2008 | |
| Title | Control Room Emergency Filtration System Inoperable |
| Event Description | On 20 Nov 08 at 1230, the Control Room Emergency Filtration System (CREFS) was declared inoperable due to a report that a non-running Control Room supply fan discharge damper was found partially open. Per the System Operating Procedure, the idle fan's discharge damper must be fully closed to assure operability. With the damper not closed, reasonable assurance that CREFS would fulfill its safety function could not be established.
With the Idle Control Room supply fan discharge damper not in the closed position, some portion of the air discharged from the operating Control Room supply fan will go backwards through the idle supply fan to the suction side of both supply fans. The CREFS fan discharges to the Control Room supply fan suctions. With CREFS in this as-found line-up, there is no assurance that the flow through CREFS is high enough to meet the design requirements assumed in control room occupant dose calculations. The Control Room supply fans and discharge dampers are required support features for CREFS at CNS. This is a single train system and per 10CFR50.72(b)(3)(v)(D) an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> report is required due to the fact that at the time of discovery this condition could have prevented the fulfillment of the safety function of an SSC that is required to mitigate the consequences of an accident. The licensee notified the NRC Resident Inspector. The damper was returned to a fully closed position at the time of discovery, and CREFS was returned to operable status.
This notification is being made to retract Event Notification EN# 44671 which reported a loss of safety function due to the unplanned inoperability of the Control Room Emergency Filtration (CREF) system. The CREF system was declared inoperable due to the non-running control room supply fan discharge damper found partially open on November 20, 2008. Cooper Nuclear Station has determined through further evaluation that while the CREF system was procedurally required to be declared inoperable, the ability of the CREF system to perform its safety function was not lost. Testing was performed on December 19, 2008, with the non-running control room supply fan discharge damper aligned in the as-found condition (~25% open) of November 20, 2008 and again tested with the damper aligned to 50% open. Technical Specifications surveillance flow requirements were met in both tests. Using the results of the test and inspection of the discharge damper it has been concluded that during the ten days the damper was out of position, the CREF system was still capable of performing its safety function and satisfying Technical Specifications requirements. Notified R4DO (Werner). |
| 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:+-0.1 h-0.00417 days <br />-5.952381e-4 weeks <br />-1.3698e-4 months <br />) | |
| Opened: | Randy Kouba 18:24 Nov 20, 2008 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Dec 24, 2008 |
| 44671 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |