SAN FRANCISCO – A federal appeals court revoked a permit allowing new radioactive waste storage structures to be built at a California nuclear power plant, ruling Friday that federal regulators must consider the likelihood of a terrorist attack more seriously.

The 9th U.S. Circuit Court of Appeals, in the first ruling of its kind, disagreed with the Nuclear Regulatory Commission's 2003 finding that an attack was “remote and speculative” and therefore the possibility needn't be seriously considered.

The challenge to the NRC's permit allowing the storage of more radioactive spent-fuel at the Diablo Canyon nuclear power plant in San Luis Obispo County was brought by a local group, San Luis Obispo Mothers For Peace. The plant is building new stainless steel and cement storage facilities because the current waste repository at the Pacific Gas & Electric Co. site is filling up.

The court said the regulatory commission could not justify its so-called “top to bottom” security review of the nation's nuclear installations while it simultaneously declared that the risk of a terror attack cannot be quantified, Judge Sidney Thomas wrote for the three-judge panel.

The decision comes as the Bush administration and Congress are renewing their interest in nuclear power as one avenue to avoid reliance on oil from the Middle East. A broad energy bill Bush signed last summer provides incentives for building nuclear reactors, and last week Bush declared the nuclear power industry an overregulated business that needs a jump-start from Washington.

The group's attorney, Diane Curran, said the lawsuit was not intended as a tactic to shutter the facility.

“The whole purpose of this lawsuit, before they build a facility, they would have to protect it, they would have to look at ways they could protect it from a potential attack,” Curran said.

Jeff Lewis, a PG&E spokesman, said the agency has enough existing space to store spent fuel, the radioactive byproduct of generating nuclear power, until 2010.

NRC spokesman David McIntyre said the agency was reviewing the decision “to determine its exact impact and our response to it.”

Since 1986, he said, 38 operating and decommissioned power plants nationwide have won approval for new waste storage facilities. Fourteen more have said they want to add more capacity, he said.

The Department of Energy in 1998 was to have begun assisting utilities remove nuclear waste to a central repository, but the proposed location at Nevada's Yucca Mountain has been mired in litigation.

The case is San Luis Obispo Mothers for Peace v. Nuclear Regulatory Commission, 03-74628.

Editors: David Kravets has been covering state and federal courts for more than a decade.