Nine environmental groups sued the Nuclear Regulatory Commission on Wednesday because they said the agency hasn't addressed how to store nuclear waste even though it resumed issuing reactor licenses last week.

At issue is an NRC determination that spent fuel could be stored on site indefinitely at decommissioned reactors without posing environmental or health risks. That ruling cleared the way to end a two-year hiatus on new licensing, as a federal court had said the NRC hadn't properly evaluated health and safety risks for storing nuclear waste in absence of a permanent repository.

The groups, which include the Natural Resources Defense Council and the Southern Alliance for Clean Energy, said the issue was still unresolved in a lawsuit filed with the U.S. Court of Appeals for the District of Columbia Circuit.

“The NRC has not dealt seriously with the safety and environmental risks posed by extended spent fuel storage and disposal," said Diane Curran, a partner at Harmon, Curran, Spielberg and Eisenberg LLP, who filed the petition on the groups' behalf.

"The rule does not make findings regarding the feasibility of safely disposing of spent fuel, as required under the Atomic Energy Act," she added. "And neither the rule nor the environmental impact statement even addresses the question of whether reactors should be licensed given the environmental risks and high costs of spent fuel storage and disposal.”

They said the question of what to do with spent nuclear fuel without a permanent waste dump remains unanswered, and they contended that only a long-term site could safely resolve safety and environmental concerns.

As far as long-term nuclear repositories go, only one site has been offered — Yucca Mountain in Nevada. But the NRC says it doesn't have the money to complete a full review of the site, and Senate Majority Leader Harry Reid, D-Nev., has made it a personal goal to ensure Yucca never becomes operational.