Today’s NRC Event Reports include the incident yesterday morning at the Byron Unit 2 reactor in Illinois. There are three significant updates.
First, the reactor is still operating on power supplied by the unit’s emergency diesel generators. So, at least as of this morning’s posting, the reactor has still not been connected to offsite power. The unit is currently in Hot Standby mode, and the report indicates that plant operators intend to take the reactor to Cold Shutdown.
Second, the Event Report confirms something that was reported yesterday by local media, that smoke was observed rising from an electrical panel. This was determined to be in the Station Auxiliary Transformer (SAT.) According to the Event Report: “Smoke was observed coming from the SAT with no visible flames being apparent. This caused bus loads to trip without a complete loss of ESF busses 241 and 242. These buses were manually disconnected from the SAT, which transferred the load to the emergency diesel generators 2A and 2B.”
Third, the Event Report confirms that the reactor is being cooled by atmospheric steam dumps. The steam released contains low levels of the radioactive element tritium.
More as it becomes available.