How is nuclear waste stored?

Nuclear wastes consist either of fission products formed from the splitting of uranium, cesium, strontium, or krypton, or from transuranic elements formed when uranium atoms absorb free neutrons. Wastes from transuranic elements are less radioactive than fission products; however, these elements remain radioactive far longer— hundreds of thousands of years. The types of waste are irradiated fuel (spent fuel) in the form of 12-foot (4-meter) long rods, high-level radioactive waste in the form of liquid or sludge, and low-level waste (non-transuranic or legally high-level) in the form of reactor hardware, piping, toxic resins, water from fuel pool and other items that have become contaminated with radioactivity. Currently, most spent nuclear fuel in the United States is safely stored in specially designed pools at individual reactor sites around the country. If pool capacity is reached, licensees may move toward use of above-ground dry storage casks. The three low-level radioactive waste disposal sites are Barnwell located in South Carolina, Hanford located in Washington, and Envirocare located in Utah. Each site accepts lowlevel radioactive waste from specific regions of the country. Most high-level nuclear waste has been stored in double-walled, stainless-steel tanks surrounded by three feet (one meter) of concrete. The current best storage method, developed by the French in 1978, is to incorporate the waste into a special molten glass mixture, then enclose it in a steel container and bury it in a special pit. The Nuclear Waste Policy Act of 1982 specified that high-level radioactive waste would be disposed of underground in a deep geologic repository. Yucca Mountain, Nevada, was chosen as the single site to be developed for disposal of high-level radioactive waste. However, as of the late 1990s, selection of the Yucca Mountain site was controversial due to dormant volcanoes in the vicinity and known earthquake fault lines.