Oak Ridge, Tenn. — More than 35 years after accumulating its first nuclear waste, the United States is not likely to put any of it in permanent disposal sites before 1994, according to the latest federal estimates.
But as far away as 1994 may seem, the fact that such a timetable is being used represents a new stage in the national problem of nuclear waste disposal -- the decision stage.
The timetable also means going ahead with, without fully testing, what researchers say is one of the most promising protective materials for use with high level nuclear waste -- monazite, an extremely stable form of phosphate.
"We're no longer talking, we're making decisions," says John Greeves, project manager of high-level waste technology for the Nuclear Regulatory Commission (NRC).
Though federal decisions still have not been made on the best protective material to coat or blend with nuclear waste and on the safest sites for buying it, a series of target dates have been established for making these decisions, apparently in response to growing pressure from the public, Congress, and even among nuclear waste researchers.
"Scientists are beginning to feel the need to make a decision and show the public we can handle it [nuclear waste]," says John Moore, a researcher at Oak Ridge National Laboratory (ORNL) here. The need is clear: By the year 2000, according to the Department of Energy (DOE), there will be some 90,000 tons of uranium waste from commercial reactors and some 320,000 cubic meters of high-level defense nuclear waste in the US.
"I think we've got to get on with it," says Ray Walton, DOE program manager for long-term, high-level nuclear waste technology. The DOE is not waiting for more definitive monazite test results.By the end of this year the DOE plans to decide on a single protective material for two years of intense study.
Initially, the chosen method will be applied to defense waste. But it could be used later for commercial nuclear waste, according to DOE officials. If further tests on monazite prove it is better than the chosen method, it could be used in the future. DOE officials add.
Other decision dates in the waste disposal process, according to the NRC's John Martin, director of waste management, include DOE selection of the first waste burial sites by 1985 and NRC licensing of the developed sites by 1994.
In June, the NRC issued a proposed federal standard for nuclear waste disposal: zero leakage of radiation for 1,000 years. The DOE calls the standard too conservative and not supported by evidence that human health requires so stringent a standard. ORNL researchers here call it an impractical standard.
"You don't get the escape [of radioactive material] down to zero; you get it way, way down," says Ray Blanco, ORNL manager for radioactive waste research and development.
Even the NRC's Greeves says "there's no such thing as a completely effective barrier."
By most scenarios, nuclear waste would be coated or blended with a neutralizing substance that would block almost all escape of radioactive materials. Then the treated waste would be packed into containers and buried far beneath the surface of the earth, probably in granite, salt, or basalt. Such dry mineral repositories are preferred to minimize or avoid any contact between the waste and underground water supplies.
ORNL researchers doubt there ever will be any contact with water in such sites.
The French currently are burying nuclear waste incorporated in borosilicate glass, storing it in temporary, near-surface pits. But tests have shown that at temperatures above 350 degrees centigrade and in contact with water of brine, the borosilicate glass "did not hold up to expected federal standards," says the DOE's WAlton. Thus the DOE search for an alternative.
Higher temperatures occur when large quantities of waste are stored in close proximity, says Walton. So the search for an alternative is "kind of an economic thing" to allow best maximum use of a disposal site, he adds.
There are six alternatives to borosilicate glass on the DOE's pared-down list.
The monazite process is not on the current DOE list because it is in such early research stages. But it appears to offer "the most promising approach" in control of actinides, the longest lasting and potentially most dangerous forms of radiation, says ORNL researcher Marvin Abraham.
The stability of monazite -- its tightness of form -- is its attraction. ORNL scientists are trying to produce a synthetic monazite and blend the waste into it at high temperatures. ORNL researchers think the cost of the monazite method of treating nuclear waste will not be out of line with other alternatives. But, they say, a few more years research is needed to perfect the method.