In environments where nuclear safety and radiation protection are required, radioactive contamination is a concern. Radioactive substances can appear on surfaces, or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirable, and processes can give rise to their presence in such places. Several examples of radioactive contamination include:
* residual radioactive material remaining at a site after the completion of decommissioning of a site where there was a nuclear reactor, such as a power plant, experimental reactor, isotope reactor, or a nuclear powered ship or submarine
* ingested or absorbed radioactive material that contaminates a biological entity, whether unintentionally or intentionally (such as with radiopharmaceuticals
* escape of elements after nuclear accident, such as the contamination of Iodine-131 and Caesium-137 after the nuclear disaster in Chernobyl, Ukraine.
Note that the term "radioactive contamination" may have a connotation that is not intended. The term refers only to the presence of radioactivity and gives no indication itself of the magnitude of the hazard involved. However, radioactivity can be measured as a quantity in a given location or on a surface, or on a unit area of a surface, such as a square meter or centimeter.
Like environmental monitoring, radiation monitoring can be employed to catch contamination-causing activities before much harm.