ENS 57146
ENS Event | |
|---|---|
12:20 May 26, 2024 | |
| Title | Two of Three Essential Chilled Water Trains Declared Inoperable |
| Event Description | The following information was provided by the licensee by phone and email:
At 0210 CDT 5/24/24, essential chiller A train and cascading equipment was declared inoperable for maintenance to correct a temperature control malfunction. At 0720 CDT 5/26/24, essential cooling water B train and cascading equipment (including B train essential chiller) was declared inoperable due to a through wall leak discovered on the essential cooling water return header temperature element thermal well. This condition resulted in an inoperable condition on two out of three safety trains for the accident mitigating function, including the train A and train B high head safety injection, low head safety injection, containment spray, electrical auxiliary building heating ventilation and air conditioning (HVAC), and essential chilled water. All C train safety related equipment remains operable. This was determined to be reportable within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> as required by 10CFR50.72(b)(3)(v)(D). NRC Resident Inspector has been notified.
The following information was provided by the licensee by phone and email: This is a communication to retract the 8-hour notification Event Notification (EN) 57146 reported to the NRC pursuant to 10 CFR 50.72(b)(3)(v)(D) on 05/26/2024. Based on a subsequent engineering review of the conditions that existed at the time of discovery, it was determined that: 1) The maximum postulated leak rate, conservatively estimated, from the B Train essential cooling water return piping thermowell in the mechanical auxiliary building sump room would have been less than the administrative allowable limit for leakage in this room during a design basis accident, 2) No adjacent safety related components or functions would have been adversely affected, and 3) the return line leakage represented a negligible impact regarding essential cooling water system inventory and the system ability to cool required components. Therefore, it was recommended that the B Train essential cooling water system with the as-found leakage condition be considered operable. Therefore, this event notification is being retracted. The NRC Resident Inspector has been notified. Notified R4DO (Taylor) |
| Where | |
|---|---|
South Texas  Texas (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:+1.53 h0.0638 days <br />0.00911 weeks <br />0.0021 months <br />) | |
| Opened: | Randall Maus 13:52 May 26, 2024 |
| NRC Officer: | Natalie Starfish |
| Last Updated: | Jun 13, 2024 |
| 57146 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |