Ignoring a fresh commitment by the Reagan administration to support nuclear fuel reprocessing in the United States, owners of the only commercial reprocessing plant in America have now written the plant off their books as a failure.

Allied Corp. announced Thursday that it intends to close its Barnwell, S.C., nuclear fuel plant by 1983 if no buyers come forward to take over the plant.

The announcement came a week after President Reagan announced that he was lifting the ban imposed by two previous presidents on domestic fuel reprocessing, which involves extracting the still-usable uranium and plutonium from spent nuclear fuel from commercial plants and converting it to nuclear fuel or weapons.

In his policy statement, which was intended to revive the moribund nuclear industry, Reagan also offered financial incentives to help private reprocessing plants make it without government help.

But Allied went ahead with the write-off nonetheless. Gerald Halvorsen, vice president of the subsidiary that operates Barnwell, said that in the current economy nuclear plants are not willing to buy reprocessed fuel for commercial reactors. This is because the studies and impact statements required in transporting and using plutonium are so expensive.

"Until the government makes a commitment to purchase reprocessed fuel, no one is going to go into this business," Halvorsen said. "In President Reagan's statement he indicated they would study it. While that's commendable, they are going to have to do more than that."

Allied had hoped that the government would buy reprocessed fuel from Barnwell for the Clinch River (Tenn.) Breeder Reactor.

Allied's announcement continues the bleak forecasts for the nuclear industry. An Allied management report on Barnwell, quoted in the prestigious Energy Daily newsletter, said there were four reasons why Barnwell is a bad risk as a venture, reasons that seem counter to the new White House assurances:

Some future president might impose a reprocessing ban again.

Operators have no assurance that the Nuclear Regulatory Commission will license a reprocessing plant, in addition to the fact that the obstacles in the way of getting such a license are large.

The United States still has no nuclear waste management program.

It is possible that the National Environmental Policy Act would apply to Barnwell, thus making an environmental impact statement necessary for the facility. This would raise new questions about storage and use of the plutonium, and open the way to lawsuits from those who oppose the plant.

Secretary of Energy James B. Edwards has been a strong supporter of the Barnwell plant, and tried to get the government to buy it. Reagan refused.