SCRIBA – At approximately 2:15 a.m. on July 12, in accordance with procedures, operators at Nine Mile Point Unit 2 took prompt and appropriate action to commence a safe, controlled shutdown of the unit.
All control rods inserted and the plant shut down as expected.
Unit 2 remains in a safe condition and the event did not pose a risk to the public.
“Based on our preliminary investigation, the shutdown occurred as the result of a loss of turbine sealing steam which resulted in reduced condenser vacuum,” said Maria Hudson, Constellation Energy Nuclear Group spokesperson.
Turbine steam sealing keeps atmospheric air on one side of the turbine casing and steam on the other side.
High-pressure steam exists at one end of the turbine and steam under vacuum exists at the other end.
Seals are used to keep the steam in and the air out.
Without the sealing steam, air would get into the turbine casing and reduce the condenser vacuum, and thus reduce the efficiency of the overall cycle.
The cause of the loss of both the primary and backup sources of sealing steam is under investigation.
Unit 1 continues to operate at full power and is not impacted.