Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment. It is typically the result of a spill or accident during the production or use of radionuclides (radioisotopes). Contamination may occur from radioactive gases, liquids or particles. For example, if a radionuclide used in nuclear medicine is accidentally spilled, the material could be spread by people as they walk around. Radioactive contamination may also be an inevitable result of certain processes, such as the release of radioactive xenon in nuclear fuel reprocessing.