Radioactive Waste

Radioactive wastes are grouped into three categories: high-level waste, low-level waste, and transuranic waste. High-level waste emits intense levels of ionizing radiation for a relatively short time, and then emits lower levels for a much longer time. Most high-level waste is used nuclear fuel rods, which must be removed from the reactor core about every 2–4 years. Large quantities of high-level wastes are also associated with the production and disposal of nuclear weapons. In 2000, about 44,000 tons (40,000 tonnes) of spent fuel were stored at commercial nuclear power sites in the United States, a quantity expected to rise to 116,000 tons (105,000 tonnes) by 2035.

Low-level waste emits small amounts of ionizing radiation, usually for a long time, and it tends to be a high-volume waste. Low-level waste is produced from a variety of sources, such as filters and other cleaning material from nuclear plants, and used low-level radioisotopes from hospitals, universities, and industry. For example, in nuclear generating stations, tiny quantities of some radioactive materials may leak from the reactor. To protect the workers and the ambient environment, this radioactivity is removed with filters, which must periodically be replaced, becoming low-level waste.

Transuranic waste results primarily from the fabrication of plutonium as well as research activities at defense installations. Transuranics are elements, not found in nature, that are heavier than uranium. Most transuranics have special properties that increase the probability of causing damage to living tissue. Transuranic elements are found in both high-level and low-level radioactive waste. They can be separated from low-level waste, and are then treated as high-level waste.