ENS 44354
ENS Event | |
|---|---|
16:41 Jul 17, 2008 | |
| Title | Degraded Control Room Ventilation Envelope |
| Event Description | At 1141 on Thursday, July 17, 2008, Braidwood Station determined that the Control Room Envelope (CRE) boundary had a degraded condition based on data obtained during performance of differential pressure testing performed in accordance with Technical Specification (TS) 5.5.18, 'Control Room Envelope Habitability Program.' Degradation of the CRE boundary was identified that could have prevented the Control Room (VC) Ventilation Filtration System from performing its safety function due to the potential for a greater amount of unfiltered inleakage into the CRE than assumed in the licensing basis analysis for Design Basis Accident consequences. The differential pressure test results identified slightly negative pressures as compared to outside air in some areas of the CRE that do not include spaces that control room occupants inhabit during accident conditions.
In accordance with the requirements of TS 3.7.10, 'VC Filtration System,' Condition B, mitigating actions have been implemented to lessen the effect on CRE occupants from the potential hazards of a radiological or chemical event or a challenge from smoke. Actions are in progress to resolve the CRE degraded condition. This event is being reported under 10CFR50.72(b)(3)(v)(D) as an 8-hour report as a condition that at the time of discovery could have prevented the fulfillment of the safety function of a system needed to mitigate the consequences of an accident. A Licensee Event Report will be submitted under 10CFR50.73(a)(2)(v). The licensee informed the NRC resident.
The licensee is retracting this report based on the following: On July 17, 2008, NRC Notification 44354 was conservatively made pursuant to 10 CFR 50.72(b)(3)(v)(D) related to the failure of a control room envelope (CRE) differential pressure test. This was the first time this test methodology had been used at Braidwood Station. Specifically, based on the test results, the unfiltered CRE inleakage could not be confirmed as being bounded by the values assumed within the accident dose analyses and hence the Control Room Ventilation (VC) Filtration System could have been prevented from performing its specified safety function. Subsequent evaluation has determined that the VC Filtration System was capable of performing its specified safety function to maintain CRE habitability, since the identified condition would not have resulted in a greater amount of unfiltered inleakage into the CRE than assumed in the licensing bases analyses. Therefore, this event notification is being retracted. The causes for the test failure were attributable to an incorrect test methodology and minor CRE boundary imperfections that had existed since plant construction. These CRE minor imperfections were present during performance of the last CRE unfiltered air inleakage test performed in 2004, which produced acceptable results. Both of these causes were corrected and the test reperformed with acceptable results. Evaluation of this event notification is documented in the corrective action program. The NRC resident has been notified of this retraction. Notified R3DO (Passehl). |
| Where | |
|---|---|
Braidwood  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.2 h0.133 days <br />0.019 weeks <br />0.00438 months <br />) | |
| Opened: | Ryan Fruth 19:53 Jul 17, 2008 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Sep 10, 2008 |
| 44354 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Braidwood with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
WEEKMONTHYEARENS 519592016-05-25T19:15:00025 May 2016 19:15:00
[Table view]10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Discovery of Non-Conforming Conditions During Tornado Hazards Analysis ENS 464142010-11-12T14:18:00012 November 2010 14:18:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Control Room Outside Air Intake Noble Gas Channel Setpoints Non-Conservative ENS 462032010-08-24T16:40:00024 August 2010 16:40:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Essential Service Water Placed in a Line-Up That May Have Prevented Its Safety Function ENS 443542008-07-17T16:41:00017 July 2008 16:41:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Degraded Control Room Ventilation Envelope 2016-05-25T19:15:00 | |