| Site | Start date | Title | Description |
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ENS 57128 | Cook | 15 May 2024 08:27:00 | Unit 2 Manual Reactor Trip | The following information was provided by the licensee via email:
On May 15, 2024 at 0427 EDT, DC Cooks Unit 2 reactor was manually tripped due to difficulty maintaining steam generator water levels.
DC Cook Unit 2 had removed the main turbine from service at approximately 0354 EDT during a planned down-power to repair a steam leak on the high pressure turbine right outer steam/stop control valve upstream drip pot. Stable steam generator water levels were unable to be maintained. As a result, DC Cook Unit 2 was manually tripped with reactor power stabilizing at approximately 20 percent.
This notification is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B), Reactor Protection System actuation as a four hour report, and under 10 CFR 50.72(b)(3)(iv)(A), specified system actuation of the Auxiliary Feedwater System, as an eight hour report.
The reactor trip was not complicated and all plant systems functioned normally. The DC Cook NRC Resident Inspector was notified. |
ENS 57124 | South Texas | 12 May 2024 21:41:00 | Automatic Reactor Trip | The following information was provided by the licensee via email and phone:
At 1641 CDT on May 12, 2024, with Unit 2 in Mode 1 at 15 percent power, the reactor automatically tripped due to a unit auxiliary transformer lockout. During the trip, all control rods fully inserted. The cause of the transformer lockout is currently unknown. Emergency diesel generator (EDG) 21 and 23 actuated and all three engineered safety feature (ESF) busses were energized.
All equipment responded as expected except for steam generator power operated relief valve (PORV) 2C which failed to open when required in automatic, and the load center (LC) E2A output breaker which failed to close automatically but was closed manually. Steam generator PORV 2C did open when placed in manual, although it subsequently failed to full open and was then closed. Primary system temperature and pressure are currently being maintained at 567 degrees/2235 psig following start of reactor coolant pumps 2A and 2D.
Due to the reactor protection system actuation (RPS) while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). This event is also being reported per 10 CFR 50.72(b)(3)(iv)(A) as an event that resulted in a valid actuation of the emergency diesel generators. There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
South Texas Project Unit 2 was in Mode 1 at 15 percent power due to performance of testing and analysis on the main turbine prior to the RPS actuation.
- * * UPDATE FROM ROBERT DEWOODY TO BRIAN P. SMITH ON MAY 22, 2024 AT 1805 EDT * * *
The following information was provided by the licensee via email and phone:
South Texas Project is submitting the following correction to the event notification:
The steam generator (SG) power operated relief valve (PORV) 2C did not fail to open automatically. System pressure during this event did not reach the automatic setpoint for the PORV (1225 psi), and there was no demand for it to open automatically. During the event, SG PORV 2C was taken to manual and it went full open when the up button was pushed slightly. It went closed when the down button was pressed to close it manually. In addition, the load center E2A output breaker initially failed to close automatically, however, after operations placed it in pull-to-lock and returned the hand switch to automatic, it closed automatically.
Notified R4DO (Dixon). |
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