ENS 53784
ENS Event | |
|---|---|
06:00 Dec 7, 2018 | |
| Title | En Revision Imported Date 12/21/2018 |
| Event Description | EN Revision Text: INOPERABLE CONTROL ROOM ENVELOPE
Braidwood Station was performing Control Room Envelope Testing. During testing the Station identified a failed acceptance criteria. The Control Room Envelope is a single train system and could constitute a Loss of Safety Function. If a single train system is inoperable per Technical Specifications (TS), it is Reportable as a Loss of Safety Function per 10 CFR 50.72(b)(3)(v) regardless of the system's continued ability to meet the accident analysis requirements. Both Units remain Mode 1, 100% power. The licensee will be notifying the NRC Resident Inspector. The acceptance criteria that failed was to maintain the control room pressure above the miscellaneous electrical equipment room pressure. The station has realigned ventilation to normal, and has entered TS Limited Condition for Operation (LCO) 3.7.10 condition B, which requires the station to restore to operable the control room envelope within 90 days or shutdown the plant. The station has also initiated contingency actions to verify SCBA (self contained breathing apparatus) are available and control room personnel are qualified to use SCBA.
On Wednesday, December 19, 2018, Braidwood Station concluded that the ENS notification 53784 could be retracted. It has been determined that the issue was not with the Control Room Envelope structure. Troubleshooting identified that the Unit 1 Upper Cable Spreading Room Area Supply Flow Control (OVC035Y) damper which supplies the Train A control room ventilation equipment room with air flow was not opening enough to supply the required flow. The subject duct work is shared by both A-train and B-train, and the flow through OVC035Y is controlled by a two-position actuator. The damper is less open when A-train is in operation (actuator energized) and more open when B-train is in operation (actuator de-energized). The only adjustments performed were to the actuator energized stroke limits which only affect the A train and thus a single train failure which could affect the safety function of both trains did not exist. Further calculations of unfiltered air inleakage into the Control Room Envelope (CRE) under a slightly negative differential pressure condition resulted in a calculated in leakage to the CRE of less than the maximum allowable unfiltered air inleakage for a radiological event of 436 scfm. The unfiltered air inleakage into the CRE assumed in the licensing basis analyses of Design Basis Accident consequences was never exceeded. Thus, TS Surveillance Requirement 3.7.10.4 continued to be met and entry into TS 3.7.10 Condition B was not required. The licensee has notified the NRC Resident Inspector. Notified the R3DO (Stone). |
| Where | |
|---|---|
Braidwood  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor | |
| Time - Person (Reporting Time:+24.2 h1.008 days <br />0.144 weeks <br />0.0331 months <br />) | |
| Opened: | Sam Keller 06:12 Dec 8, 2018 |
| NRC Officer: | Thomas Kendzia |
| Last Updated: | Dec 20, 2018 |
| 53784 - NRC Website
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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 %) |
WEEKMONTHYEARENS 537842018-12-07T06:00:0007 December 2018 06:00:00
[Table view]10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor En Revision Imported Date 12/21/2018 2018-12-07T06:00:00 | |