Late Thursday night, operators at the South Texas Project were in the process of restarting the Unit 2 reactor. Procedure required closing the reactor’s main steam isolation valves. Rather than closing each valve individually, as is mandated in the plant’s operating procedures, operators initiated a procedure that is normally used for emergency operations, isolating all the steam valves at the same time using the solid state protection system.
According to the report posted on the NRC’s Event Notification Reports page:
The manual actuation was not initiated to mitigate the consequences of an actual event. However, the method of closing the main steam valves for this condition did not specifically require that the valves should be closed by initiating a main steam isolation signal and therefore, the safety system was unnecessarily actuated.
The report concluded that the action taken “was not part of preplanned sequence during testing or reactor operation.”
Although the safety significance of the incident may have been minimal, it implies poor training and adherence to process on the part of employees at the South Texas Project. The report did not specify any remedial procedures to prevent a repetition of the error.
