Waterford — Later this year, 75 tons of used radioactive fuel will be moved out of the pool of cooling water where it’s been stored for nearly 30 years and into concrete and metal casks that sit on the property of the Millstone Power Station.

The 75 tons of spent fuel, from Millstone Unit 3, will be the first batch of spent fuel to be moved from wet into dry storage since the nuclear reactor began making electricity in 1986. The transfer will happen around the same time that another 75 tons of spent fuel from Unit 2, which began operating in 1975, will also be taken out of a separate water pool at that plant and sealed inside the dry casks. All the spent fuel produced by Unit 1, which has been shut down since 1995, remains in another cooling water pool that is about two-thirds full.

“About 49 percent of all the fuel Unit 2 has used it its lifespan is already in dry cask storage,” Ken Holt, spokesman for Millstone, said Monday. “After the move later this year, 7 percent of Unit 3’s spent fuel will be in dry casks, and a little more than half of Unit 2’s.”

As workers at Millstone prepare for the spent fuel transfer, questions are being raised nationally about whether more should be done to reduce the risks of keeping large amounts of used but highly radioactive fuel in pools of water for long periods of time.

Last week, the National Academy of Sciences released a report calling on the Nuclear Regulatory Commission to re-examine its position on whether more spent fuel should be moved out of wet into dry storage more quickly. When the uranium rods that fuel the reactor are exhausted — after about 4 1/2 years of use — they are still very hot and radioactive, and must be kept in water pools for at least five years to cool before they can be moved to dry casks. But at most of the nation’s 99 operating reactors — including the two at Millstone — the spent fuel stays in wet storage for much longer, typically until the pool nears capacity.

“There’s a backlog of most of the older spent fuel in pools,” Edwin Lyman, senior scientist at the Union of Concerned Scientists, said Monday. “Now, only about a quarter of the spent fuel in the country is in dry casks.”

Lyman’s comments were prompted by the release of the National Academy of Sciences’ report, which was commissioned by Congress to determine what lessons could be learned from the 2011 Fukushima Daiichi nuclear accident and applied to improve the safety of U.S. nuclear plants.

In a statement about the report, the academy said the accident in Japan “should serve as a wake-up call” of the need to reduce the risks of storing large amounts of spent fuel in cooling water pools that could be damaged in earthquakes and tsunamis — as happened at Fukushima — as well as terrorist attacks, plane crashes and other disasters. The report notes that one of the spent fuel pools at Fukushima came dangerously close to causing a large release of radioactive material into the environment. Only an “accidental but fortuitous” leak of sea water into the pool — which had been draining out after the earthquake — prevented the water level from dropping perilously low.

In response to the report, the Concerned Scientists, a watchdog group, said the document supports their longstanding contention that the NRC should require nuclear plants to move more spent fuel into dry casks more quickly. Currently, said Lyman, plants are allowed to use “high density” spent fuel storage in the pools. The scientists group believes only “low density” storage in the water pools should be permitted, a potentially costly change that would require nuclear plants to build new dry cask storage facilities.

“Lower density would significantly reduce the risk of a spent fuel fire, which would have catastrophic consequences,” Lyman said, adding that a fire could occur if a disaster caused water to drain out of the wet pool, exposing the hot, radioactive spent fuel, Lyman said.

About 80 percent of the nation’s spent fuel, he said, could be moved into dry casks — which are considered less vulnerable to breaches during disasters. That would require a tripling of the dry storage capacity nationwide, he said.

At Millstone, the number of dry cask storage pads was increased in 2013, at a cost of about $11 million. The number of concrete pads that hold the dry casks was increased from 49 to 135 — enough for the remaining life of both operating plants. But most of the pads have not yet been fitted with the casks themselves.

Holt said the new pads “gives us more margin” to move used fuel into dry casks, but that there are no plans to expedite the transfer out of wet storage.

“The NRC maintains that both dry and wet storage is safe, and we agree with that,” he said.

In December, Millstone owner Dominion Resources notified the NRC that it had met all the new requirements imposed after Fukushima to improve safety of the wet pools. That included adding new instruments so that water levels could be measured after an accident — a lapse that came to light as the Japan disaster was analyzed.

“We also have equipment that can put water where we need it” in the event of a disaster, Holt said. That includes additional pumps and generators.

Neil Sheehan, spokesman for the NRC, said the agency is still reviewing the National Academy report, and will issue a formal response on Oct. 6.

“The NRC staff’s initial review of the report has not identified any immediate safety issues or any recommendations requiring immediate action,” he said. “The staff will continue to carefully review the report to determine if further action is warranted.”

Sheehan added that Millstone has submitted its plan on how it would keep used fuel cool and contained after a Fukushima-level disaster — one the plant was not originally designed to withstand. The NRC is reviewing the plan.

Behind the questions being raised about keeping spent fuel in wet or dry storage at the nation’s nuclear plant lies a bigger unresolved problem, Lyman of the concerned scientists group said. Because there is still no permanent national repository for spent nuclear fuel, plants are forced to store the waste on site, meaning that communities like Waterford are involuntarily housing nuclear waste dumps.

“Our position is that the federal government should be living up to its obligations to take this fuel,” Holt said.

Nuclear plant owners, Lyman said, are reluctant to add dry cask storage on site both because of the cost, and because having more casks could lessen any urgency toward creating a federal waste site. But with no significant progress in years on establishing a waste site, waiting for that to happen before steps are taken to make plants safer for the public is unwise, he said.

“Plant owners' goal is to get the spent fuel off their sites, but that isn’t going to reduce the risk while it’s still being stored there for many decades to come,” Lyman said.

j.benson@theday.com

To read the National Academy of Sciences Report, visit: http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=21874.

The Union of Concerned Scientists' response to the report can be found at: http://www.ucsusa.org/news/press_release/NAS-spent-fuel-report#.V0W_1_krLcs.