Antinuclear activists in Virginia, who contend that shipments of spent radioactive fuel through the state are a threat to health and safety, filed suit yesterday asking that the shipments be stopped.

The Richmond-based Virginia Sunshine Alliance and Three other plaintiffs asked U.S. District Court in the District of Columbia to stop the Nuclear Regulatory Commission from permitting the shipments. The agency has given approval to a firm that trucks between 50 and 60 large spent fuel casks annually from the Portsmouth, Va., harbor to a fuel-reprocessing plant in Aiken, S.C.

Agency officials told the court yesterday that there would be no new shipments until after next Wednesday, when District Court Judge John G. Penn will hear arguments on whether to issue a preliminary injunction in the case.

Fred Millar, spokesman for the plaintiffs, hailed the commission's statement as a victory, but agency officials disagreed, saying no shipments had been planned until after that date.

"We'll be in court next week to contest the suit," said agency Solicitor Stephen Eilperin.

The suit charges that the agency violated its own regulations by grantin temporary approval last week to shipments originating from the Portsmouth harbor in the densely populated Tidewater area. Those regulations, issued in June, require shippers to "avoid were practicable, heavily populated areas."

According to the suit, the agency's approval "was based solely on considereations of operational convenience, to the exclusion of considerations of public health and safety."

The suit also contends that the commission should have issued an environmental impact statement before approving the spent-fuel route.

It cites a 1978 report made for the agency by Sandia Laboratories of New Mexico suggesting that fuel shipments could pose "an attractive target for sabotage or theft." According to the suit, the report said deaths resulting from a release of radioactivity from spent-fuel casks in an urban area could result in hundreds of cancer deaths.

According to the suit, the agency said yesterday the shipments were approved only until the end of August, and that the commission and the shipping company, Transnuclear Inc. of White Plains, N.Y., both were searching for a safer, less-populated route for the spent fuel.