Gov. Roy Romer says federal officials have four months to find a disposal site for low-level nuclear waste from the Rocky Flats nuclear weapons plant or he'll try to close the plant until another site is found.

"I don't want to give anybody any indication whatsoever that they can turn a temporary storage situation into a permanent one," Romer said Monday. "The Department of Energy needs to find a solution to this."The governor's remarks came as a boxcar of low-level radioactive waste was returned to the Rocky Flats plant, about 16 miles northwest of Denver. The boxcar was headed for a temporary storage site in Idaho but Idaho Gov. Cecil Andrus sent it back Saturday, and banned further shipments to his state.

Under a state permit, up to 1,600 cubic yards of solid waste can be stored at the Department of Energy plant, which make plutonium triggers for nuclear warheads. It will take the plant about four months to reach that storage capacity.

Between now and then, Romer said, DOE officials must find another place to store Rocky Flats waste. If they don't, he said, he will move to shut down the plant.