This wind-swept volcanic ridge, which rises above the cratered desert flats where America long has tested its nuclear weapons, is emerging as a leading candidate to become the tomb for the nation's growing accumulation of deadly atomic wastes.
While nine sites in six states are reluctant contenders to become the first burial ground for wastes that will remain highly radioactive for thousands of years, this desolate mountain 100 miles northwest of Las Vegas appears certain to be one of the finalists when the list is cut to three early next year.
Nuclear waste disposal has always seemed to be one of those esoteric environmental problems that belonged to the future. But, without a plan for disposing permanently of the radioactive spent fuel fast filling temporary storage pools alongside reactors, many U.S. atomic power plants will be unable to operate much longer. And without nuclear power it is not clear how the United States can meet its foreseeable energy needs.
The selection of a permanent repository took on a new urgency, moreover, with last month's Supreme Court decision letting states block construction of atomic power plants until an adequate federal waste-disposal plan is implemented.
The Nuclear Waste Policy Act, which President Reagan signed into law on Jan. 7, requires that extensive exploratory activities be conducted at three potential repository sites before one finally is selected in March, 1987.
Seven of the sites under consideration are located atop salt deposits in Utah, Texas, Louisiana and Mississippi. The outcry at initial hearings in those states suggests that they are highly susceptible to what politicians call the "NIMBY syndrome"--Not In My Back Yard.
"I think it's obvious that with any type of waste facility selection you are going to have a lot of public concern," said Michael Lawrence, deputy director of the Energy Department office managing the disposal program. "If you add to that the fact that we are dealing with radioactive waste, it is going to be even greater." But at least one salt site will be selected as a finalist.
The other two under consideration are this one at Yucca Mountain, an outcropping of compacted volcanic ash known as "welded" tuff, and the Hanford site on the Columbia River plateau in southeastern Washington, which sits atop thick layers of basalt, a dense form of hardened lava.
The prospect of putting the radioactive wastes under those sites seems to be meeting less vehement local opposition, undoubtedly due at least in part to their location on vast Energy Department reservations long dedicated to the production or testing of nuclear weapons.
Since the Nuclear Waste Policy Act calls for investigation of diverse types of geologic formations as possible burial sites, the fact that Nevada is the only tuff candidate and Hanford the only basalt one has led many to view their inclusion in the final three as a foregone conclusion.
The Yucca Mountain site was first identified as a potential nuclear waste repository in the late 1970s.
The Nevada Test Site, where more than 600 nuclear weapons have been detonated over the past three decades, covers a huge expanse of desert approximately the size of Rhode Island. While the early atomic tests here involved bombs mounted on towers or dropped from planes, all tests since July, 1962, have been set off in underground shafts or tunnels.
The Hanford reservation, a 570-square-mile desert site east of the Cascade Mountains, has been used since 1943 to produce plutonium for nuclear weapons. At its peak in the 1960s, Hanford had nine reactors, strung along the banks of the Columbia River, turning out bomb-grade plutonium. Only one still operates.
"Basically, the view was that these two places already were contaminated with radioactive material and there was very little chance this land mass would be turned back to the public domain in an uncontrolled way, so what we had to determine was whether or not they would be geologically acceptable," said Donald R. Vieth, director of the Energy Department's Waste Management Project Office in Las Vegas.
At first, the hunt at the Nevada site for a suitable geologic formation centered on granite, another lava-formed hard rock that miners view as close to ideal for building the maze of underground tunnels and vaults that would comprise a radioactive waste repository.
But no suitable granite site could be pried away from the weapons testers. As a result, exploratory efforts here since mid-1979 have centered on the tuff underlying Yucca Mountain, which straddles the Nevada Test Site's western boundary.
"At first, we really weren't all that positive about it," Vieth said. "Yucca Mountain certainly didn't fit the stereotyped view of what a repository site should look like, the nice flat plains of Kansas or Texas."
The slopes of the ridge are lined with faults, the calling card left by ancient earthquakes. And looking westward into the desert from the crest of Yucca Mountain, one sees cinder cones that testify to the area's history of volcanic activity.
While the National Academy of Sciences said in a report on geologic repositories issued this month that the "frequency of major earthquakes" in this area remains an issue, it added that "Yucca Mountain is remarkably free of recorded earthquake epicenters even though parts of the surrounding area are very active."
Moreover, geologists and hydrologists discovered a feature of Yucca Mountain that makes it uniquely attractive among the locations under consideration for the first burial site, a very deep water table that would permit construction of a repository in the "unsaturated zone" above standing water.
The water table at Yucca Mountain is about 1,800 feet below the surface. And government experts now are looking at a stratum 1,200 feet underground as the location for a nuclear waste repository.
"Solids that are buried 1,200 feet underground just don't come back to the surface on their own," Vieth said. "Water really is the only viable mechanism by which radionuclides are going to come out of a repository and come back to man's environment."
The Yucca Mountain area gets about 6 inches of rain per year, most of which runs off without penetrating the surface. Only about 5 percent of this 6 inches, officials said, would percolate down through the rock, pass through a repository and ultimately reach the water table.
"So there would be moisture in a repository here, but not a puddle," Vieth said. "That's why being above the water table is so attractive."
Beyond that, one of the desirable properties of tuff is that it is "highly sorptive." This means that if water passing through the waste repository picks up dangerous radionuclides some of those elements would interact chemically with the tuff, be removed from the water and remain trapped in the rock.
Finally, hydrologists said that if all barriers to release of radioactive elements from a repository in Yucca Mountain failed, water containing the radionuclides ultimately would reach the environment 35 miles away in the desert, a process estimated to take 21,000 years.
"It appears that there is no surface water into which potentially contaminated ground water can discharge," the academy's report said.
However, because of the lack of surface water in this desert region, more "attention must be focused on possible use of the potentially contaminated ground water by humans, for potable water and irrigation," the report added.
Beyond tuff's attractive properties from the standpoint of isolating nuclear waste, it has been shown by the weapons program to be a good engineering material, officials said.
"We have built tunnels in tuff 1,400 feet down for weapons tests. And for 20 years we have been setting bombs off in those tunnels, and they are still standing," Vieth said. Some of these tunnels are 30 feet in diameter, more than twice the size of the structure envisaged for a waste repository.
"So we have an awful lot of hands-on experience for 20 years at this site in terms of how to design and build these underground structures," Vieth said. "We now are feeling very positive that the Yucca Mountain site is technically suitable. We think it would be a reasonable one to pursue."