The Nuclear Regulatory Commission, in one of its most important rule changes in three decades, has streamlined its licensing process, agreeing with industry complaints that government delays were harming the future of nuclear power in the United States.

Anti-nuclear activists were quick to assail the NRC's decision Friday.On a unanimous voice vote, the commission adopted rules that would enable a utility to receive a combined construction permit and operating license before even breaking ground on a nuclear plant project.

Under the old NRC rules, a utility had to first apply for a construction permit and then, upon completion of the plant, seek an operating license.

Industry officials charged that the two-step process gave anti-nuclear activists too many opportunities to raise issues that could delay operation of a finished nuclear plant for years.

They pointed to the Shoreham nuclear plant in New York and the Seabrook facility in New Hampshire as prime examples of how the NRC's licensing process was exploited by nuclear opponents.

In both cases, activists raised emergency planning concerns after the plants were built but before the utilities got operating licenses from the NRC. The plants have remained idle as anti-nuclear groups have pressed their contentions in lengthy NRC administrative proceedings.

Anti-nuclear groups criticized the new licensing procedure as an effort to shut the public out of NRC deliberations on whether a completed plant is safe enough to go on line.

"The burden of proof has been shifted from industry . . . to the public, which will have no timely access to the reams of technical data needed to make its case," said Scott Denman, director of the Safe Energy Communication Council.

In particular, anti-nuclear activists expressed concern the NRC may no longer hold public hearings prior to granting final permission to operate plants, as is now the case. The NRC said the new rules provided only "very limited" grounds for citizens to seek a hearing before a plant goes on line.

Industry groups expressed satisfaction with the NRC's changes.