Radioactive waste

Radioactive waste is material containing radionuclides that requires controlled handling and disposal. Its hazards and management needs depend on radionuclide type, concentration, and longevity.

Radioactive decay: The spontaneous transformation of unstable atomic nuclei, often releasing ionizing radiation. Decay lowers activity over time, but the rate varies greatly among radionuclides.
Deep geological repository: An underground facility designed to isolate radioactive waste in stable geological formations. It is a leading long-term disposal approach for spent fuel and high-level waste.
Manhattan Project: The United States-led wartime program that developed the first nuclear weapons during World War II. Its weapons production generated some of the earliest large-scale radioactive waste streams.
Interim storage of spent nuclear fuel: The temporary containment of spent nuclear fuel pending reprocessing or final disposal. Storage delays a final decision and requires continued oversight, unlike disposal intended to be permanent.
Half-life: The time required for half the radioactive nuclei in a sample to decay. Half-life helps estimate how long particular waste remains hazardous.
Spent nuclear fuel: Nuclear fuel removed from a reactor after irradiation, containing residual fissile material and radioactive fission products. It is intensely radioactive and heat-generating, requiring interim storage and a long-term management decision.
Nuclear fission: The splitting of a heavy atomic nucleus into lighter nuclei, releasing energy and often neutrons. Fission produces radioactive fragments that become major components of reactor waste.
Nuclear fuel reprocessing: The chemical separation of reusable materials from spent nuclear fuel and its remaining waste products. Reprocessing changes the waste stream but does not eliminate the need for disposal.
Ionizing radiation: Radiation with enough energy to remove electrons from atoms or molecules. Its biological effects determine the protective measures needed during handling.
Low-level waste: Radioactive waste with limited concentrations of radionuclides, generally requiring less isolation than high-level waste. Its disposal often uses engineered near-surface facilities rather than deep repositories.

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