| Site | Start date | Title | Description |
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ENS 57019 | South Texas | 10 March 2024 08:53:00 | Essential Chilled Water Trains Declared Inoperable | The following information was provided by the licensee via email:
On 3/9/2024 at 2126 CST, train C essential cooling water was declared inoperable due to a through-wall leak on the discharge vent line. This would also cascade and cause train C essential chilled water to be inoperable.
On 3/10/2024 at 0353 CDT, train B essential chilled water was declared inoperable due to chilled water outlet temperature greater than 52 degrees F following startup of essential chiller 12B. Chilled water outlet temperature was adjusted to less than 52 degrees F at 0440 CDT, and train B essential chilled water was declared operable.
This condition resulted in the inoperability of two of the three safety trains required for the accident mitigating functions including: high head safety injection, low head safety injection, containment spray, electrical auxiliary building HVAC, control room envelope HVAC, and essential chilled water.
This is an 8 hour reportable condition per 10CFR50.72(b)(3)(v)(D) because it could affect the ability to mitigate the consequences of an accident.
The licensee notified the NRC Resident Inspector. |
ENS 57010 | Comanche Peak | 5 March 2024 13:20:00 | Accident Mitigation - Loss of UPS Cooling | The following information was provided by the licensee via email:
- 8 Hour Notification was due at 1520 CST *** Follow up discussion of conditions after recovery determined that a report is required. This report restores reporting compliance.
On March 5, 2024, at 0720 CST, the X-02 118V uninterruptible power supply air conditioning (UPS A/C) unit tripped with the associated emergency fan coil units (EFCUs) shut down for planned maintenance in the area. The X-01 UPS A/C unit was declared inoperable upon discovery due to a scheduled outage of support systems (Unit 1 station service water) via the safety function determination process. This placed the site in technical specification 3.7.20 condition A, B, and C to restore the UPS A/C system within one hour. The EFCUs were restarted at 0729 which satisfied condition B and C, and X-01 UPS A/C unit was aligned to Unit 2 cooling water at 0801, exiting condition A. The condition that could have prevented the fulfillment of the safety function lasted for approximately nine minutes. Area temperatures had no notable change based on field observations during the condition.
The UPS HVAC system provides temperature control for the safety related UPS and distribution rooms during all normal and accident conditions. The UPS HVAC system consists of (a) a dedicated UPS room EFCU in each safety-related UPS and distribution room, and (b) two electrically independent and redundant A/C trains either of which can support all four safety related UPS and distribution rooms; each train consists of an air conditioning unit, ductwork, dampers, and instrumentation.
The NRC Resident Inspector has been notified. |
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