Waterford - Millstone Power Station owner Dominion plans to expand its nuclear waste storage capacity more than sevenfold at the 520-acre site of its three nuclear power plants.

Ken Holt, spokesman for Dominion, said the company is seeking to increase the number of dry cask storage units at the site from 19 to 135, enough to hold all the spent nuclear fuel generated by the power plants through the decommissioning of Unit 3, the newest, in 2045.

The company already has permission from the Connecticut Siting Council to build an additional 30 of the concrete-and-steel chambers, but it has determined that it would be easier to construct all the dry cask units it will need for all three plants at once rather than incrementally, Holt said.

At present, 18 of the 19 casks are filled with spent fuel from Units 2 and 3. The expanded facility would create space for spent fuel from the decommissioned Millstone 1 plant, which is now kept in deep water pools at the site.

Dry cask is the method preferred for long-term storage by both the industry and watchdog groups such as the Union of Concerned Scientists, especially since the Fukushima nuclear disaster in Japan in March 2011, because it is better able to withstand natural disasters.

"There is a measurable risk (to the dry cask storage method), but it's an acceptably low level," said David Lochbaum, director of the nuclear safety program at the UCS. Compared to storage in spent fuel pools, he added, "there is less risk to the community.

The Nuclear Regulatory Commission authorizes dry casks as safe for the storage of nuclear fuel for 120 years. The nation's nuclear sites began installing dry casks in 1987, and "there have been no significant problems with them at any of the sites," said Tom Kauffman, senior media relations manager at the Nuclear Energy Institute, an industry group.

Nuclear fuel, after used in a reactor for about five years, no longer produces energy efficiently and must be replaced. It remains hot and highly radioactive, however, and must sit for at least five years in pools of water before it can be moved into dry casks, which use passive systems of air circulation for cooling. The radioactivity level of the spent fuel diminishes rapidly in the first five years. All of the material in the fuel rods, however, does not reach safe radioactivity levels for tens of thousands of years.

Dominion met last week with Waterford and East Lyme town officials about its plan to submit an application in August to the Connecticut Siting Council for permission to expand its storage capacity. While the nine-member council has the final authority over whether to approve the request, comments from the towns on the proposal would be taken into consideration in the decision, said Melanie Bachman, staff attorney for the council. The public also will have a chance to comment.

"We will most certainly have a public hearing on this, since it is a controversial issue and there will be a lot of public interest," Bachman said.

Bill Sheehan, chairman of the Nuclear Energy Advisory Council, a group that represents the public on issues concerning Millstone, said his group likely will comment based on a review of the design details of the proposed expansion. Dry casks, he said, are considered a safe method of nuclear waste storage, "but we don't want to have it there forever."

A decision would be made 30 to 60 days after the Siting Council hearing, Bachman said. Among the nine council members is a representative of the state Department of Energy and Environmental Protection, said Edward Wilds, director of DEEP's radiation division. Issues that could be considered by the council include the total amount of nuclear waste already stored in Connecticut. There are 412 metric tons at the decommissioned Connecticut Yankee plant in Haddam and another 1,638 metric tons in the spent fuel pools and dry casks at Millstone, Wilds said.

Though it is the third smallest state, Connecticut stores the 14th highest total amount of nuclear waste, according to the NEI. Nationally, more than 65,000 metric tons of waste have accumulated over the last 50 years from nuclear power and defense applications. No single repository for its long-term storage is on the horizon.

Waterford First Selectman Dan Steward said that while he understands Dominion's need to create more capacity for nuclear waste, he does not want the Millstone property to become a nuclear waste dump long-term. When the town first agreed four decades ago to host the nuclear power plants, he said, it did so with the belief that federal government would create a single facility to safely store the waste from the nation's 104 nuclear plants long-term, and that the individual plants would be required to hold the spent fuel for only a few years.

"Millstone has to have someplace to offload the fuel," he said. "But my concern is that the federal government has not provided for the spent fuel, and there was a commitment from the federal government that there would be a repository."

While dry cask storage is safe, provided the facilities are kept secure and off-limits to the public, keeping the waste there precludes any reuse of the Millstone site once the plants are decommissioned, Steward said.

"It's a nice piece of property on Long Island Sound," he said.

The federal government, said Tom Kauffman, senior media relations manager at NEI, is breaking its own law that requires it to have a nuclear waste repository in place by 1998. The proposal to create a repository at Yucca Mountain in Nevada was scrapped in 2009. Kauffman said the federal government should have "let the science play out" and completed its analysis of the suitability of that site before abandoning the project.

Despite frustration that a repository does not yet exist, Kauffman said there has been some recent movement towards a solution. The Blue Ribbon Commission on America's Nuclear Future, commissioned by the Obama administration after the 2009 decision to scrap the Yucca Mountain plans, released a report in January urging that action toward creation of a permanent storage facility begin, noting that such a project would take many years. It also recommended a collaborative approach with would-be host communities that takes the social, political and technical considerations into account as it proceeds, not as an afterthought.

Kauffman said Congressmen from both parties support taking steps to implement the Blue Ribbon panel's recommendations.

"Not so long ago, it was a dead end," he said. "Now there's a pathway forward."

j.benson@theday.com