The Nuclear Regulatory Commission acted hastily in concluding that spent fuel can be stored safely at nuclear plants for the next century or so in the absence of a permanent repository, and it must consider what will happen if none are ever established, a federal appeals court ruled on Friday.

In a unanimous opinion, a three-judge panel of the Court of Appeals for the District of Columbia said that in deciding that the fuel would be safe for many decades, the commission did not carry out an analysis of individual storage pools at reactors across the country, treating them generically instead. The commission also did not adequately analyze the risk that cooling water will leak from the pools or that the fuel will ignite, the court wrote.