Scientists at the Oak Ridge National Laboratory have said that it is technically feasible for a "bandit nation" to produce enough plutonium from uranium to make a crude atomic bomb in six months.

This conclusion came from a paper connected with the design of a production facility the scientists drafted for their own use, but which has been circulating in Washington.

Opponents of President Carter's policy to curb plutonium production say the draft design undercuts one of the key assumptions of the President's plan.

Proponents of limits on the spread of nuclear power see the design as a conspiracy to sabotage their position.

The Carter administration is against the proliferation of power plants that use or produce plutonium because it has said that a nation in possession of such a facility could easily divert the metal to the making of nuclear weapons.

The White House has said that a country depied plutonium and wanting nuclear weapons would have to make them from urantium, a process that had been presumed to be so involved that it would be obvious from aerial wurveillance, take a lot of money and involve at least two years' work, which would give other countries time to detect such a move and stop it.

But in a report identified as "intra-laboratory" correspondence, scientists at Oak Ridge said that any nation that wanted to could build in six months a plant to extract plutonium from spent uranium fuel and then begin production of that plutonium inside of a week.

Once in production, the plant could make enough plutonium every month for 10 nuclear weapons, the report said.

In the design of what the report calls a "quick and simple" reprocessing plant, nothing is automated. A winery, dairy or oil refinery could be converted to plutonium extraction, the report says. It also assumed that a country wanting to make plutonium for weapons would have "adequate and ready funds" and a "sympathetic and friendly populace."

The plant design is written up in a 23-page report from D. E. Ferguson to Floyd L. Culler, deputy director of the Oak Ridge National Laboratory.

Culler said he asked for the report as the result of a conversation he had at the State Department with Carl Walske, president of the Atomic Industrial Forum, and Joseph S. Nye. deputy under secretary of state for security assistance and an architect of the Carter policy on plutonium and the spread of nuclear weapons.

"I told Nye that I didn't think a two-year lead time without plutonium or a complex reprocessing plant was realistic," Culler said in a telephone interview."I told him i felt the time involved if a country really wanted to get there in a hurry wasn't nearly that long."

Culler said he had no idea how and why the report was being circulated in Washington. He said he delivered it to Nye at the State Department about a month ago and didn't say "it should or shouldn't be distributed."

Critics of the Carter plan say the Oak Ridge report deals a blow to the Carter policy against plutonium spread. They sau it proves that elaborate reprocessing is not needed and that fast breeder plants are not needed to produce plutonium for bombs round the world.

One source in the Department of Energy questioned why the report was being circulated in Washington, saying it sounded as if White House policy on plutonium was being undermined by Oak Ridge National Laboratory.