Vermont Yankee reported a steam leak to the NRC yesterday. During quarterly startup of the High Pressure Coolant Injection (HPCI) system for surveillance, “audible and visual indications of steam leakage were observed,” according to an Event Report posted today to the NRC website.
An associated fire alarm signal was received in the control room as a result of rising temperature in the Reactor Building. As a result, employees were evacuated from the building.
Operators were dispatached to the fire control panel in the Reactor Building and confirmed that there was no fire. The HPCI system was iolated, and temperatures in the Reactor Building began to decrease.
Cause of the leak is still being investigated, but until the problem is repaired, the HPCI system has been declared inoperable. As per usual operating procedure, absence of the HPCI is not considered sufficient reason to reduce the power output of the reactor.