Dominion: Preliminary Findings Point To Electric Circuit Card Glitch At Millstone Unit 3
WATERFORD, Conn. – Dominion (NYSE: D) said
Wednesday that preliminary findings reveal a failed electrical circuit card
initiated a shut down Sunday of Millstone Power Station Unit 3.
The electrical circuit card caused Millstone
Unit 3 operating systems to shut down the reactor automatically because it detected
a signal of low steam pressure in the secondary system. This false indication
caused a main steam line isolation, which resulted in the opening of a safety
valve as designed. Steam safety valves functioned properly except one valve
that closed slightly later than operators expected. That valve will be replaced
prior to unit restart.
Based on operators’ analysis of the steam
flow, Dominion declared an "Alert" at Millstone Unit 3 early Sunday.
The "Alert" classification is the second lowest of the four U.S. Nuclear
Regulatory Commission’s emergency classifications.
The NRC Region I office in King of Prussia, Pa.,
has begun a special inspection to Millstone to review the event and Dominion’s
corrective actions. Dominion will cooperate fully with the NRC team.
"We have replaced the circuit card and successfully
tested the new one, and we are checking the unit’s other safety equipment,"
said J. Alan Price, Millstone site vice president. "We should finish our
preliminary report in the next few days, assist the NRC team with its independent
inspection and be prepared to return the unit to service shortly. Above all
else, we will ensure the unit is safe to operate before we return it to service."
The 1,150-megawatt unit shut down automatically.
Reactor operators cooled the unit safely and ended the alert Sunday evening.
There were no injuries and no radioactive materials were released as a result
of this event.
The alert did not affect Millstone Unit 2, an
870-megawatt unit that is in the midst of being refueled. Millstone Unit 1,
a 660-megawatt unit, is shut down and is being decommissioned.
Dominion is one of the nation's largest producers
of energy, with an energy portfolio of about 28,100 megawatts of generation,
about 6 trillion cubic feet equivalent of proved natural gas reserves and 7,900
miles of natural gas transmission pipeline. Dominion also operates the nation's
largest underground natural gas storage system with more than 965 billion cubic
feet of storage capacity and serves retail energy customers in nine states.
For more information about Dominion, visit the company's Web site at www.dom.com.
