Nuclear waste is the radioactive byproduct of a nuclear fuel reaction. Nuclear waste is categorized in three ways: high-level waste, mid-level waste and low-level waste. Each level corresponds to the radioactivity absorbed by an object in and around a nuclear reactor.
High-level waste is typically the spent fuel rods that are used in nuclear reactors to aid in the generation of electricity. The average time nuclear fuel rods spend in a nuclear reactor before they become nuclear waste is approximately three years. The average level of radioactivity measured in spent fuel rods is approximately 95 percent. Due to its high level of radioactivity, high-level waste must be handled with extreme care, so many protocols are used to lessen the likelihood of contaminating the environment. An example of this is encasing spent fuel rods in layered containers and storing the containers in specially designed storage facilities.
Mid-level waste typically comprises such materials as steel components around the nuclear reactor that do not require cooling and effluents like chemical sludge. The average level of radioactivity measured in mid-level waste is approximately 4 percent.
Low-level waste typically comprises cloths, tools and other materials used in the maintenance of nuclear reactors. Additionally, low-level waste includes the radioactive byproducts generated in the medical, mining and space industries. The average level of radioactivity measured in low-level waste is approximately 1 percent.