A deep underground salt chamber designated for the first U.S. tests of permanent radioactive waste disposal will probably collapse years before the tests can be completed, mining experts told Congress on Thursday.
The conclusion, disclosed as the Department of Energy pushes to clear the final legal obstacles to testing its $800-million nuclear waste disposal project in the New Mexico desert, raised the specter of additional costs in a project already years behind schedule. It could bring further delay in the staggering task of cleaning up polluted nuclear weapons sites.
According to nine government, industry and university scientists appearing before a House Government Operations subcommittee, the ceiling of the chamber in which the Energy Department hopes to store the first bins of nuclear waste this summer probably will begin to collapse within the next two to three years.
By present estimates, that would be six to seven years before completion of tests that will determine whether the facility can safely be used to dispose of toxic and radioactive wastes from nuclear weapons plants.
Rock falls have already occurred as chambers mined from the rock salt deposits nearly 20 years ago undergo natural processes.
The problem disclosed Thursday arises from the fact that the repository outside Carlsbad, N. M., has to undergo a 10-year research program before the massive underground mine can be cleared as a dump for material that will remain lethal for tens of thousands of years.
Salt deposits were chosen because the chambers hollowed out 2,150 feet below the surface will naturally close, crushing the containers of waste and sealing the material into the seamless formation.
Under an agreement with the Environmental Protection Agency, the Energy Department hopes to begin this summer shipping the first of 4,250 barrels of waste to New Mexico to be placed in one of the 56 rooms, each 300 feet long, carved from southeastern New Mexico salt.
The casks will be monitored over the next 10 years to measure the effects of corrosion and of hydrogen gas generation by organic materials in the plutonium-contaminated refuse, to determine whether it will be safe to dump hundreds of thousands of barrels of waste in the caverns.
During the test period, the Energy Department and Westinghouse, the site's operating contractor, will be required to keep the facility in a condition allowing the material to be removed in the event unsafe conditions develop.
Also on Thursday, a House Interior subcommittee approved legislation that would remove one of the last obstacles to opening the controversial repository for tests, approving a bill that would transfer the 10,000-acre site from Interior Department ownership to the Energy Department.
Energy Department officials indicated Thursday that they intend to proceed with plans to begin testing the facility in spite of the estimates that the test chamber's lifetime may be no more than another two or three years.
Appearing before a House Government Operations subcommittee, Leo P. Duffy, director of the Energy Department's Office of Environmental Restoration and Waste Management, said the chamber adjacent to the one now awaiting arrival of the first containers can be modified, with structural steel holding up the ceiling long enough for the tests to be completed.
Another room could be mined out for the tests, he said, but it would cost about $1 million, as compared to $250,000 to install steel supports in the existing room.
In either case, he said, the plan would be to transfer the material from the initial storage space into the modified chamber.
In a test chamber, heated to accelerate the closure process, there have been major ceiling collapses within the last year, causing opponents of the project to renew charges the repository is inherently unsafe.
But Duffy said the collapses had been accurately predicted. Workers, he said, would have sufficient warning time to remove the waste from its first storage room into the reinforced chamber during the test period.
In addition to the problem of the closing test chambers, Rep. Mike Synar (D-Okla.) said, the Energy Department has other major hurdles to overcome before it will be able to proceed through all the phases of the test program, which is designed to store representative samples of all the country's defense waste products.
Among the problems, he cited the failure thus far to develop a satisfactory seal for closing the repository's individual test chambers once they are filled.