The Energy Department's preferred method of cleaning up 2,100 metric tons of highly radioactive spent nuclear fuel at its Hanford, Wash., plant is the most dangerous and probably the most expensive of the available options, an independent study organization charged yesterday.

According to the Institute for Energy and Environmental Research, of Takoma Park, the department's proposal to remove the stored fuel from tanks of water and process it to extract plutonium "reveals fundamentally inadequate technical analysis, a cavalier attitude toward issues of the most serious nature and a narrow-minded reluctance to consider the intent of environmental law."

The report, financed by the Washington state government, was written by Scott Saleska and Arjun Makhijani, the institute's president. Both are longtime critics of the Energy Department's weapons complex.

Makhijani said at a news conference that "there is no good way" of removing or neutralizing the spent fuel. But of all possible methods, he said, the "most irresponsible" is the plan submitted by DOE's primary contractor at Hanford: to restart Hanford's Plutonium-Uranium Extraction facility (PUREX) to process the spent fuel. This is actually "a back-door way of producing plutonium" for nuclear weapons, Makhijani said.

He said the United States has more plutonium than it needs for defense purposes. Activating PUREX to extract more would generate at least 500,000 gallons

of radioactive liquid waste that would have to be stored in Hanford's subterranean tanks, which he said might explode. He said it would be preferable, and $300 million cheaper, to leave the spent fuel where it is until an above-ground, dry cask storage system can be developed.

Department spokesman Tim Tomastik said no decision to restart PUREX has been made. He said the department was "going to determine whether or not to proceed with preparation of an environmental impact statement that would examine the options for handling the spent fuel that's in those ponds. . . . The conclusions they {the critics} are drawing are based on incorrect assumptions."

Energy Department waste management director Leo Duffy said last week that restarting PUREX was "one option" under consideration. But the text of the department's five-year plan for managing wastes at the weapons complex refers to a "final campaign to recover weapon-grade materials" from the Hanford fuel, which could only be done at PUREX.

At issue is the fate of 2,100 metric tons of spent, or used, fuel rods from the Hanford reactor known as N-reactor. That reactor, once the primary source of plutonium for nuclear weapons, has been shut down since 1988 because of similarity in design to the Soviet reactor that blew up at Chernobyl.

PUREX, built in the mid-1950s, is a huge factory-like building where chemical processes extract plutonium from the N-reactor's spent fuel. Closed in 1972, it was restarted in 1983 during the Reagan administration's defense buildup, but was shut down again for safety reasons in December 1988, leaving no outlet for the N-reactor fuel.

About half the spent fuel is in canisters that were welded shut in the 1970s. The rest is in open canisters in direct contact with the storage water. Makhijani said the Energy Department gave no explanation for failing to complete the sealing process, but Tomastik said the process is under way and Makhijani and Saleska should have known that. "One of their premises is that we are wantonly disregarding this," he said. "We have ordered the parts and it will be finished by the end of this year."