Will US dump nuclear waste at sea again?

A US Navy plan to sink old nuclear submarines offshore is raising a swell of opposition against using the oceans as dumping grounds for radioactive waste.

Several European nations dump nuclear waste at sea, and until 1970, the United States did so, too. But since then, the environmental view that land disposal of nuclear waste was preferable has prevailed in the US.

But as America's nuclear waste - both military and civilian - continues to pile up in temporary land storage sites, deep-sea areas are getting a fresh appraisal. Some oceanographers say initial data indicate disposal of the low-level contamination on nuclear submarines (after their fuel has been removed) may be safe.

But in the absence of more complete studies showing such dumping is safe, it should not be done, says Clifton Curtis, an environmental attorney representing (on this issue) a dozen environmental organizations, including the Wilderness Society, Sierra Club, Friends of the Earth, and the Environmental Defense Fund.

The sinking of old nuclear submarines could be ''just the thin edge of quite a large wedge'' of many uses of the ocean as a nuclear dumping ground, says Gordon Thompson, a staff scientist for the Union of Concerned Scientists. And although one submarine might be no problem, Navy estimates of up to 120 submarines to dispose of in the next 30 years concern him, he says.

Ray Johnson, who manages ocean programs for the US Environmental Protection Agency, says the EPA has received a number of inquiries from hospitals, pharmaceutical firms, and state governments about use of the ocean as a dumping ground for low-level nuclear waste, including waste from nuclear reactors.

The US dumped low-level nuclear waste in the ocean from the late 1940s till 1970, mostly in the '50s and '60s, Mr. Johnson says. But in 1970 the federal Council on Environmental Quality recommended the seas be used only as a last resort. Since then the US has not used the ocean for nuclear dumping - a de facto moratorium, since under US law it still has been allowable.

Now, however, both the Navy and the Department of Energy (DOE) are considering applying for EPA permits to use the ocean for nuclear dumping.

In a move that has critics concerned, the EPA is revising its regulations to require that ocean dumping of nuclear waste be considered ''equally as an option'' to land disposal, says the EPA's Johnson.

The DOE has some 100,000 cubic yards of radioactive soil left over from the Manhattan Project (which developed the first US atomic bomb). The soil is now stored in a parking lot under a plastic covering in Middlesex, N.J., says the EPA's Johnson.

The soil's level of radioactivity is only ''slightly higher'' than natural background levels of radiation, he says. One plan is to dump the soil with no containers, since the contamination in the soil would far outlast any possible container, he said.

Critics, including California state Sen. Barry Keene, are worried about the long time that some kinds of radioactive isotopes in the metal of the nuclear submarines would last. Mr. Keene is especially concerned that one of the two sites being studied by the Navy is about 185 miles southwest of Cape Mendocino, Calif., at a depth of about 14,000 feet. (The other site is about 230 miles southeast of Cape Hatteras, N.C., at about 17,000 feet, but other sites may be chosen eventually.)

Some radioactive elements present in the submarines may not even be known, says Homer Ibser, a physicist at California State University at Sacramento and a participant in the original Manhattan Project.

Chances of the submarine sinking being harmful are ''very remote,'' but ''it needs to be proven that it is safe,'' says Charles Hollister, of Woods Hole (Mass.) Oceanographic Institution, who has studied ocean bottoms for 15 years. He strongly opposes putting high-level nuclear waste on the ocean floor, however.

Ross Heath, dean of the School of Oceanography at Oregon State University, says radiation risks to man and the environment from deep-water sinking of nuclear submarines is ''so minuscule'' that the final decision will be a political one, not a technical one. His staff is assisting the Navy in its site research.

The EPA's Johnson says that in a small sampling of barrels used in past US nuclear dumping in the ocean, 25 percent showed signs of ''being crushed (and) could be leaking.''

The Navy plans to finish an environmental impact statement this summer on the nuclear submarine ocean disposal, the first step toward seeking an EPA dumping permit.