Ceramics based on cubic zirconia--the stuff used in cheap jewelry--may be hundreds of times more effective than conventional materials for storing plutonium and other nuclear waste. But don't clean out your hope chest just yet, because many hurdles remain--both scientific and political--before governments can get over their plutonium headache.
In long-term waste storage facilities, such as the one proposed for Yucca Mountain in Nevada, radioactive materials would be stored in steel drums, buried deep underground. But the real protection against environmental damage is the material that the plutonium is immersed in. "We're working on materials that are intimately mixed with the radioactive material," says Kurt Sickafus, a materials scientist at Los Alamos National Laboratory. Most research in the U.S. has focused on glassy materials, which might last for thousands of years--but even that's not long enough to outwait plutonium, which has a half-life of 24,100 years.
In the 4 August issue of Science, calculations by Sickafus and his colleagues show that ceramics based on cubic zirconia are extremely resistant to radiation damage. The reason seems to be cubic zirconia's lattice, in which each unit consists of two zirconium atoms, two atoms of another metal such as erbium, and seven atoms of oxygen. When plutonium atoms are incorporated into this matrix, they bang on the lattice with tremendous force every time they decay. The jolt may knock zirconium atoms into spots where the erbium should be, and vice versa. Other crystals wouldn't be able to take this abuse, but zirconia can, according to the team, because those atoms have roughly the same size.
Other nuclear waste experts say the work is promising because it provides a blueprint for finding other materials that can resist radiation damage. Unfortunately, says Alexandra Navrotsky, a solid state chemist at the University of California, Davis, that doesn't mean the nuclear waste problem is solved. "There are so many factors in this business" affecting the decision on how to store nuclear waste, she says, such as cost and the hydrology and geology of the disposal site. Besides, as long as there's no agreement where to bury the waste, it won't matter how good a buffer scientists can develop.