VERNON -- Federal nuclear regulators say storing spent nuclear fuel on-site indefinitely is safe.

The U.S. Nuclear Regulatory Commission this week released a study on the environmental impacts of storing spent nuclear fuel. The report found that dry casks designed to store spent nuclear fuel can withstand natural disasters, and the risk of a terrorist attack is unlikely.

Entergy's Vermont Yankee nuclear power plant in Vernon is scheduled to close at the end of the year for economic reasons. The Louisiana-based company plans to store spent fuel from the reactor in steel dry casks on site indefinitely.

The environmental impacts outlined in the report focus on construction and management activities of the storage site, such as exhaust emissions from transporting the fuel and disturbance to land when building the storage pad.

Dry storage process for spent nuclear fuel. Courtesy NRC
Dry storage process for spent nuclear fuel. Courtesy NRC

NRC spokesperson Neil Sheehan said spent fuel storage is safe because the used rods cool over time and their radioactive isotopes decay to harmless materials. Spent nuclear fuel consists of rods no longer able to generate electricity. There is currently no repository for the waste.

However, the report does not consider the environmental impact should the dry casks be damaged by an earthquake, flood or terrorist attack. That's "because all important safety structures, systems, and components involved with the spent fuel storage are designed to withstand these design basis accidents without compromising the safety functions," according to the report.

Arnie Gundersen, chief engineer with Fairewinds Energy Education and a longtime nuclear safety advocate, is less optimistic about the safety of long-term storage.


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"If everything goes the way the NRC plans, storing nuclear fuel can be done safely. But that's a big if," he said.

His chief concern is a terrorist attack aimed at destroying the dry casks.

"These things are sitting ducks for terrorist targets," he said. The casks can be "easily penetrated by armor-piercing equipment terrorists have."

The NRC study says the "very low probability of a successful attack ensures that the environmental risk is small."

Gundersen said Vermont Yankee also has site-specific environmental concerns such as flooding. He said the storage pad is located near the Connecticut River. If the storage pad area were flooded, he said the muddy water would clog the cask's air-cooling system.

"If mud gets into these from a flood, they won't cool themselves and then we have a big problem," he said.

Because there is currently no location to store spent nuclear waste, the NRC is proposing rules that would allow it to be stored at reactor sites around the country for longer periods.

The environmental impact statement comes after an appeals court in 2012 ruled the agency failed to evaluate the environmental impacts of its proposed rules for storing nuclear waste longer. The new rule aims to address the concerns raised by the court.

Sheehan said a presidentially appointed commission that oversees the NRC is now reviewing the proposed rule. He said the commission can approve, modify or disapprove the rule.