North Anna reactor shut due to water leak
Leak of contaminated water leads to shutdown of North Anna reactor
Date published: 10/27/2009
By RUSTY DENNEN
One of North Anna Power Station’s two nuclear reactors is shut down
because of contaminated-water leaks discovered Friday afternoon.
Unit 1 was still down yesterday, said Richard Zuercher, spokesman for
Dominion power’s nuclear operations.
“We are making repairs and expect to return to service soon,” he said.
According to Zuercher and an event report yesterday by the Nuclear
Regulatory Commission, there were two issues with Unit 1′s cooling
system.
Around 4:30 p.m. Friday, a pinhole leak was discovered in the reactor
purification system. The system recycles some of the water used to
cool the reactor core.
“Operators isolated the pinhole by redirecting the water into a backup
piping system designed for this purpose,” Zuercher said. “That was
very, very small–almost like a vapor.”
But then operators discovered a water leak of more than 15 gallons a
minute from a heat exchanger on the backup system. They then swapped
the water flow back to the line with the pinhole leak and began
shutting down Unit 1.
The heat exchanger leak exceeded the regulatory limit for radioactive
contaminated water, which the NRC deemed–after the fact–to be an
unusual event. The Virginia Department of Emergency Management was
notified as a result.
An unusual event is the lowest of four levels of emergency
classification used by the NRC.
Approximately 260 gallons collected in a piping system, not on the
floor, Zuercher said.
“There was no threat to station employees, nor the public,” he said.
The North Anna plant is on the Louisa County shore of Lake Anna, near Mineral.
An unusual event was declared at Dominion’s Millstone nuclear plant in
Waterford, Conn., in April 2008.
In that incident, a coolant leak was discovered at Millstone Unit 2
when it was shut down for scheduled maintenance and refueling. It is a
pressurized water reactor like the North Anna units.
That leak between the reactor coolant system and a coolant storage
tank was captured by the tank, so there was no release of liquid to
the environment.
Rusty Dennen: 540/374-5431
