YUCCA MOUNTAIN

To understand the politics, you have to look at the history of the nuclear indus­try. In the early years of the nuclear industry, it was thought that spent nuclear fuel would be reprocessed to remove the plutonium and uranium. But President Gerald Ford halted the reprocessing of commercial reactor fuel in 1976, and President Jimmy Carter shut down the construction of the reprocessing plant in Barnwell, South Carolina, in 1977 because of fears that reprocessed plutonium would be used in nuclear weapons (8, 12). The Nuclear Waste Policy Act of 1982 (13) specified that the federal government was responsible for finding a suitable site for disposal of high level waste from spent nuclear fuel and authorized the US Department of Energy (DOE) to evaluate sites and recommend three. It gave the Nuclear Regulatory Commission the authority to set regulations on the construc­tion and operation of the facility and gave the EPA the authority to set standards for radiation exposure to the public. Thus, three different government bureaucra­cies would be responsible for nuclear waste storage. Furthermore, the act required that nuclear power utilities pay into a Nuclear Waste Fund (NWF) at the rate of one-tenth of a cent per kWh of electrical energy produced to pay for the evalua­tion and development of a waste disposal site, which was to be opened by 1998. According to an official audit of the NWF, as of September 30, 2012, the total nuclear utility payments plus interest totaled $43.4 billion with expenditures of $11.4 billion. The value of Treasury securities held by the NWF totaled $38.7 bil­lion (14). Utilities are suing the DOE because it has not provided a facility to store nuclear waste as provided in the Nuclear Waste Policy Act and should therefore not continue to collect the fee (15).

The DOE began exploring various geological sites for long-term storage of spent nuclear fuel, including sites in Texas, Washington, and Nevada. The deci­sion for the best site was not made by scientists, however, but by “the best geolo­gists in the U. S. Senate” (16), who chose Yucca Mountain in southern Nevada. It happened that the Speaker of the House was Jim Wright from Texas, and the vice president of the United States, George H. W. Bush, was also from Texas, so Texas was not chosen. Tom Foley, from the state of Washington, was the House Majority Leader, so Washington was not chosen. It seemed that nobody wanted a nuclear waste repository in his state. But this left Nevada, and Harry Reid—the first-term senator from Nevada—did not have the political power to oppose it. So Yucca Mountain was chosen by Congress in 1987 as the sole long-term site for com­mercial spent nuclear fuel disposal based on political considerations, not on what was the best geological site. In effect, the decision was rammed down the throat of Nevada, and Nevadans did not exactly take it lying down.

Harry Reid subsequently became the Majority Leader of the Senate, which put him in a position to block the site, and he has vigorously worked to do so (16). He has, in fact, accomplished that, at least temporarily. Since President Obama needed Senator Reid’s support to accomplish other objectives, he cannot support Yucca Mountain when Reid is so opposed to it. In June 2008 the DOE formally submitted a license application for Yucca Mountain to the NRC, which it sub­sequently withdrew because President Obama provided no funding. Instead, in 2010 President Obama directed the Secretary of Energy, Steven Chu, to establish a Blue Ribbon Commission on America’s Nuclear Future to study the issues of spent nuclear fuel disposal (17). Ultimately, the courts will decide whether work on Yucca Mountain should go forward.

So much for the politics. What about the scientific and engineering consid­erations of Yucca Mountain or other long-term waste disposal sites? The major consideration is for a site to have a stable geology in a very dry region. As humans, most of us have little sense of the time involved in geological processes. The dawn of agriculture began just about 10,000 years ago, so nearly the entire lifetime of human societies is encompassed in the time frame for the decay of spent nuclear fuel to the level of the uranium ore it originally came from. It is natural to think that we cannot possibly predict what will happen in the next ten or hundred thou­sand years in human society. A million years is but a blink of an eye in geological processes, however, so it is not so difficult to imagine that very stable geologi­cal formations can be found that are adequate to store nuclear waste. After all, the uranium that is mined to make nuclear fuel has been around since the earth formed 4.5 billion years ago.

Nature has already provided a clear demonstration that nuclear wastes can be contained for millions of years in geological formations. A natural deposit of ura­nium (the Oklo deposit) with about 3% 235U formed in Gabon, Africa, about 2 bil­lion years ago. This concentration of 235U is similar to the concentration in nuclear power reactors and could undergo sustained fission under the right conditions, which existed in the uranium deposit. More than a dozen sites existed in the ura­nium deposits where controlled fission reactions occurred for hundreds of thou­sands of years, producing about 15 gigawatt years of power (18). But how could we possibly know that nuclear fission occurred 2 billion years ago? As discussed earlier, when 235U undergoes fission, it produces fission products and transura — nics, new elements that were not there previously. Also, the 235U gets used up when it fissions, so the percentage of 235U in the uranium ore will be lower than it should be. Both of these were discovered in the uranium ore from Oklo. The natural reactor existed so long ago that all of the plutonium has long since decayed away, as well as the short-lived fission products such as 137Cs and 90Sr, but other reactor-specific, very long-lived isotopes still exist. The long-term waste from the reactor was in the same geological formation as the uranium, and this formation was sufficiently stable to contain the fission products for 2 billion years.

Yucca Mountain is a 6-mile long ridge located in the Nevada Test Site where nuclear weapons were tested during the Cold War, approximately 100 miles northwest of Las Vegas and about 30 miles northeast of Death Valley. Eruptions of a caldera volcano millions of years ago produced ash and rock, which melted and fused to become layers of volcanic tuff. Subsequent tilting along fracture lines formed the ridge that is now called Yucca Mountain (19). The site is in an unpopulated arid desert of rabbitbrush, cacti, grasses, and a few yucca. About $9 billion has been spent on research and development of the site, making it the most intensively studied geology on earth. Alternating layers of hard, fractured tuff and soft, porous tuff with few fractures permeate the mountain, making it a complex geology.

There are three good reasons that Yucca Mountain would be a good burial site, though. One is that the region is very dry, with only about 6 inches of rainfall a year, which mostly evaporates or is taken up by plants. A second reason is that the water table is very low, so that the repository would be about 1,000 feet below the mountain ridge yet still about 1,000 feet above the water table. The third reason is that the layers of tuff contain minerals called zeolites and clay that serve to trap radioisotopes that might eventually get dissolved in water and migrate through the mountain (20). Even if radioisotopes could eventually get into the water table, Yucca Mountain is in a hydrologic basin that drains into Death Valley. On the way it would flow under Amargosa Valley, the desert valley about 15 miles away from Yucca Mountain that has a population of about 1,500 people.

What do we have to show for the $9 billion? The DOE excavated a 25-foot bore­hole sloping down into the mountain about a mile, then turning and after about 3 miles reemerging from the ridge. Rooms and side tunnels have been created to do research on the geology and water infiltration, and sophisticated computer mod­els have been created to model radionuclide movement over time. A fully devel­oped site would have about 40 miles of tunnels to store casks containing the spent nuclear fuel from reactors and other high level waste. Waste would be stored in double-walled, corrosion resistant cylinders 2 meters (about 6.6 feet) in diameter and 6 meters long. The cylinders would be covered with a ceramic coating and a drip shield to further protect against water and then backfilled with a clay soil that would absorb radioisotopes in the spent nuclear fuel (20). Yucca Mountain is designed for retrievable storage of nuclear waste according to the governing law, although it would eventually be permanently sealed.

There are several plutonium isotopes and other transuranics that are produced by neutron capture during burn-up of nuclear fuel. Anti-nuclear activists like Helen Caldicott cite the long lifetimes of 239Pu and other transuranics to fuel fears about spent nuclear fuel. Since the half-life of 239Pu is 24,100 years, surely it is going to be a big problem, right? Actually 239Pu is not the real problem because it will be adsorbed by the clay and zeolite in the rock and also is not readily soluble in water. After all, the half-life of 235U is 700 million years and the half-life of 238U is 4.5 billion years, the age of the earth, and they are in geologically stable formations! To see what the real problem is, we have to dig a little deeper into the nuclear transformations in the waste. I mentioned earlier that 241Pu was the most serious problem, but why is that? After all, the half-life of 241Pu is only 14.7 years, so there will be almost none left in 150 years. When a radioisotope decays, some­thing else is created. In the case of 241Pu, it p-decays to form americium (241Am) with a half-life of 432 years, which hangs around a lot longer. But 241Am a-decays into neptunium (237Np), which has a half-life of 2.1 million years. And that is the real problem. It turns out that neptunium is about 500 times more soluble in water than plutonium, even though neither one is absorbed very well by the human digestive system. So the real radiation concern at Yucca Mountain is not plutonium but neptunium. That is why the main study of radiation from Yucca Mountain is concerned with modeling the transport of neptunium, not pluto­nium. Scientists from Los Alamos National Laboratory have concluded that the various levels of containment at Yucca Mountain will contain the neptunium for more than 10,000 years. In fact, they concluded that it would take at least 100,000 years for the radiation level to reach 20 mrem/yr (0.2 mSv/yr) (20).

The US Environmental Protection Agency (EPA) was given responsibility for setting the radiation standards to be used for Yucca Mountain, and it issued stan­dards in June 2001. However, the EPA was sued and the US District Court of Appeals ruled that the EPA’s standards did not adequately take into account a 1995 National Academy of Sciences report (21), so EPA revised its radiation standards. The current EPA rules require that groundwater near Yucca Mountain can have no more radiation than is allowed by current groundwater standards nationwide, which is a maximum dose of 4 mrem per year (0. 04 mSv/yr) to an individual drink­ing the water. The external dose is limited to 15 mrem/yr (about the equivalent of a chest X-ray) for the next 10,000 years to an individual who might live in the area. Because of the court ruling, the EPA then required that the dose to an individual be no more than 100 mrem/yr (1 mSv/yr) from 10,000 to one million years (22).

The DOE believes that the multiple barriers it has designed for the containers, the geology, and the low water infiltration at the site will be able to meet these extremely stringent standards. But what is the worst that could happen? Recall that after about 15,000 years the toxicity of the spent nuclear fuel is reduced to that of the uranium ore from which it originally came. So, in effect, the waste storage site has become a radiation deposit not much different than a natural deposit of uranium ore. One of the concerns about Yucca Mountain is that we have no idea whether human society will exist in the area in 10,000 years, let alone one million years. So let’s suppose that society continues for the next 10,000 years. Because of global warming (if we haven’t solved the problem), it is likely that the area will be much drier than now, so there will probably be no agriculture and little chance that radiation would enter the groundwater. But what if it is actually a wetter cli­mate? If the society living then is more advanced than we are now, they will be well aware of the effects of radiation and will be able to minimize any effects on humans in the area. If we have bombed ourselves back to the Stone Age, then the primitive people will not be able to build and operate wells that would get water from hundreds of feet below the valley, so they would not be exposed to ground­water in any case. So society would either be advanced enough to deal with a little extra radiation or too primitive to be exposed to it.

There are numerous sites in the United States where groundwater exceeds the EPA standards because of natural uranium and radium in the soil, so it would not be a catastrophe if radiation from Yucca Mountain actually got into groundwater and exceeded current EPA standards. What about the standard of not exceeding 1 mSv/yr for the next million years? The natural exposure to radiation in the sparsely populated Amargosa Valley is 1.30 mSv/yr, which is less than the US average (23). Recall that the background radiation from natural sources for US citizens is about 3.20 mSv/yr, but some of us are exposed to a lot more radiation than that. The average for Colorado, where I live, is about 4.5 mSv/yr because Colorado is at a high elevation, causing increased exposure to cosmic radiation, and there is a lot of uranium and radium in the granite of our mountains. There are communities at particularly high elevations in Colorado, such as Leadville, where the radiation level is much higher than the Colorado average (about 5.5 mSv/yr). Just from that fact alone, the concern about an additional 1 mSv to people living near Yucca Mountain in tens or hundreds of thousands of years becomes trivial. Their total dose would still be less than the average dose to other US citizens and about half the dose that millions of Coloradans get every year! And Colorado has the fourth lowest death rate in the United States from cancer (24).

But that is not the end of the story either. The average exposure of US citizens to radiation from medical procedures is an additional 3.0 mSv/yr, a factor which has increased five-fold over the last two decades. If the people in the Amargosa Valley in a few thousand years are in a primitive society, they will probably not be get­ting a lot of CT scans, so their radiation doses will be much lower than that of US citizens now. And finally, it is highly likely that research will continue in the pre­vention and treatment of cancer so that it will be a much more treatable disease.

So, as far as an enhanced radiation exposure from storing spent nuclear fuel in a stable geological site such as Yucca Mountain, that is trivial compared to the exist­ing exposures of millions of people, and the enormous public concern is really just a tempest in a teapot. As I said earlier, the problem of long-term storage of nuclear waste is a political problem, not a scientific or engineering problem. We simply lack the political will to make intelligent decisions and instead get caught up in outlandish “what-ifs" And we waste billions of dollars studying and litigating a problem to death instead of just taking care of it.

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