The vast majority of the radioactive plutonium on the planet is man-made—roughly 500 metric tons, or enough to make 100,000 nuclear weapons. Much of it is the legacy of the nuclear arms race between the U.S. and the former Soviet Union. More and more, it is also the legacy of nuclear power.
Now a team of scientists is arguing that burying plutonium is the only reasonable solution to this problematic stockpile. In a comment published in Nature in May, a group of physicists and environmental scientists recommends that the U.K. should lead the way by studying how to immobilize the “element from hell” in ceramic pucks that can be buried in deep caverns or boreholes. (Scientific American is part of Nature Publishing Group.)
So far countries have been pursuing other options. The U.K. appears to be leaning toward following the example of France and Japan in their attempts to use the plutonium in so-called mixed-oxide, or MOX, nuclear fuel, which combines oxides of uranium and plutonium. The U.S. is doing the same, spending $13 billion to turn 34 metric tons of its plutonium stockpile into MOX at a facility in South Carolina, even though it is more expensive and harder to handle than conventional fuel.
Japan, France, Russia and the U.S. have also used plutonium as fuel in so-called fast reactors, which employ neutrons to initiate fission. The problem is that these high-speed reactors require highly flammable liquid sodium, instead of water, to cool them. And there would still be radioactive material left over, thereby only delaying the problem.
So why not take the cheaper route and immobilize plutonium, then put it deep underground? That may be because finding a place to bury it has proved politically radioactive. Yucca Mountain in Nevada is no closer to being a solution for nuclear waste than in the 1980s, when it was first designated as a final resting place for radioactive residue. Nor has the U.S. adequately prepared financially for tearing down old nuclear reactors and dealing with the radioactive waste left behind, according to an April report from the Government Accountability Office.
The problem with treating plutonium “unambiguously as the dangerous weapons material that it is,” as the scientists put it, is that few want to pay to have it buried, even very deeply, anywhere near their backyard.