Waterford - The Millstone nuclear complex has equipment in place to prevent power loss and partial meltdowns like those occurring at reactors in Japan, plant owner Dominion said Monday.

Friday's earthquake and tsunami knocked out power that caused cooling systems to fail at three separate reactors at the Fukushima Daiichi Nuclear Power Station. The threat to the public includes the continued melting of the core, the part of the reactor where fission occurs, radiation sickness and contamination.

"This is a very extraordinary situation Japan is in - it's unprecedented," said Ken Holt, a spokesman for Dominion. "We're trying to learn as many lessons as we can about this event."

The Millstone complex sits on the edge of Long Island Sound. Its older Unit 2, which began operating in 1975 and generates 884 megawatts of electricity, is licensed through 2035. The site's Unit 3, built in 1986, generates 1,227 megawatts of electricity and has been relicensed through 2045. Millstone 1 is permanently shut down.

David Lochbaum, a nuclear engineer and director of the Nuclear Safety Program with the Union of Concerned Scientists, said in a media conference call Monday that many of the United States' 104 reactors could be similarly vulnerable.

"Any reactor design currently operating today that had been faced with an earthquake followed by a tsunami would likely be in similar situation," he said.

But here in Connecticut, U.S. Geologic Surveys show a low risk of earthquakes, though the state and southeastern Connecticut are prone to hurricanes. Millstone's two operating reactors have a few things going for them - should what Lochbaum calls "the bad day" ever occur.

Both Units 2 and 3 have two backup diesel generators each. Unlike some of the generators reportedly flooded in basements at the Japan sites, Millstone's generators are protected from possible floodwaters. Flood barriers in a concrete bunker protect the Unit 3 generators, while concrete structures with flood barriers inside are in the Unit 2 turbine building, according to Holt, the Dominion spokesman.

In addition, Units 2 and 3 are not on a list of 27 reactors that the U.S. Nuclear Regulatory Commission is reviewing for risk to seismic activity, said NRC Spokesman Neil Sheehan. Despite that, Holt said the company is reviewing its earthquake preparations and "watching for news coming out that we could apply to our own operations here."

Unlike some other reactors in the United States, Millstone Units 2 and 3 have pressurized water designs. The Japanese reactors are boiling water reactors.

The pressurized water reactors have cooling water not only in the reactor core, but in a secondary water system in the steam generator, which creates steam that spins the turbine to make electricity. The reactors also have steam-driven auxiliary feedwater pumps, which can help cool the reactor.

The pumps circulate cooling water as long as the reactor is hot enough to generate steam, so electrical power is not essential, though it is normally in use, said Holt.

Millstone also has extra battery-powered backup that can be charged while in use with an additional generator reserved for serious blackouts. The batteries would "bridge the gap" if power goes out, Holt said. Unit 2 has two eight-hour safety batteries and Unit 3 has four two-hour batteries, he said.

Japan's reactors had eight-hour batteries but they ran out, the Union of Concerned Scientists' Lochbaum said.

When the Millstone complex was built, then-owner Northeast Utilities assessed the plants for earthquake risk and flood risks and the possible loss of offsite power, said the NRC's Sheehan.

"So we'll see whether any revisions are warranted" as Japan's situation plays out, Sheehan said, as well as evaluate the lessons learned and plan accordingly.

p.daddona@theday.com

Mike DiMauro