A nuclear activist said Friday that the owner of Millstone Power Station should remove radioactive waste from the pool atop its closed reactor, a step the company said is already under review.

Paul Gunter, director of reactor oversight for the activist group Beyond Nuclear of Takoma, Md., said Friday that Millstone owner Dominion should remove the waste from Unit 1 and put it in some of the dry-cask storage available on site, since the pool could be vulnerable if ever exposed in a catastrophe like that occurring in Japan.

Dominion spokesman Ken Holt said Friday, however, that the company had been evaluating the possibility of moving spent fuel into dry storage before the events still unfolding in Japan took place.

Japan's situation "is a factor in making our decision and will be considered when we make our decision," Holt said.

"While wet storage of fuel is safe and the way it's being stored now is safe, dry storage has some benefits to it," Holt said. "Mainly, it's a passive system. It doesn't require pumps or motors. It uses natural air circulation to keep the fuel cool."

The spent fuel pool at Unit 1, which was permanently closed in 1998, sits atop the reactor building, which is a boiling-water reactor design similar to the plants at the Fukushima Daiichi Nuclear Power Station in Japan. Two of the Fukushima reactors have experienced fire or explosions in their pools in the aftermath of the earthquake and tsunami that battered the nation's northeast coastal area last week.

The Millstone nuclear complex on Long Island Sound has two other operating reactors, Units 2 and 3, in addition to the one that's shut down. Units 2 and 3 are pressurized water reactors whose spent fuel pools are in concrete buildings adjacent to the reactors.

Twenty-three reactors in the United States are Mark 1 boiling-water reactors like those in Fukushima. Unit 1 at Millstone is a Mark 3 reactor with Mark 1 containment, Holt said.

The risk to the public involves the release of radiation during a catastrophe. Millstone Unit 1's reactor pool is covered by a vented, fire-retardant metal roof and surrounded by walls made of reinforced concrete, Holt said. But the roof could be torn off in an explosion or calamity and expose the fuel.

Dry-cask storage at Millstone today includes 19 concrete bunkers the size of one-car garages lined up hundreds of yards away from the reactors. Fourteen of those bunkers house one cannister each filled with 32 fuel assemblies from the Unit 2 reactor. Each Unit 2 assembly holds 176 used, 14-foot-long fuel rods.

Inventory needed

Gunter says President Barack Obama's call for a comprehensive review of safety issues at the country's 104 reactors should include the inventory of nuclear waste still sitting in these nuclear-waste storage pools.

"It's not just the seismic event that one needs to be concerned about; it could be an accident initiated by any kind of event," Gunter said.

Nancy Burton, an anti-nuclear activist from Redding Ridge and Mystic who called Friday for the Millstone complex to be completely closed, also noted Unit 1's vulnerability in extreme circumstances.

Moving spent fuel to dry-cask storage is complex, said Holt.

Dominion now has permission to build up to 49 bunkers but is only allowed to move waste from Units 2 or 3 into them, Holt said. The company would have to return to the Connecticut Siting Council to add more bunkers and move Unit 1 waste into the new ones, he said, adding that the NRC would also have to grant permission to move the Unit 1 fuel.

"It's a process to do it safely and right," he said.

Neil Sheehan, a spokesman for the federal Nuclear Regulatory Commission, which Obama has ordered to conduct a review, said in an e-mail it is too early to say whether that national review would include moving spent fuel into dry storage. The NRC plans to meet early next week on Obama's directive, he said.

"The NRC certainly intends to carefully study the Japanese events for implications for U.S. reactors," Sheehan wrote. "However, the immediate focus is on providing technical assistance to the Japanese and monitoring any developments there."

The Nuclear Energy Institute has also asked reactor owners to examine their safety systems in connection with fires, aircraft impact, explosions and loss of power.

On Wednesday, Dominion put together a team of engineers, operators, maintenance personnel and other key workers to look at the kinds of safety issues the Japan incident has raised and "to ensure we are prepared as we can be in the event of an event like this," Holt said.

"We're doing our own investigations," Holt said. "We want to do what we can to increase the safety of our reactors. They're safe now, but we feel we can make them safer."

p.daddona@theday.com

Day staff writer Karin Crompton contributed to this report.