Kr-85

Krypton-85 (Kr-85) is a radioactive isotope of krypton with a half-life of approximately 10.7 years. It decays by beta emission, producing stable rubidium-85 (Rb-85). Kr-85 also emits low-energy gamma radiation, making it detectable through gamma spectrometry. It is primarily produced as a byproduct of nuclear fission in reactors and during the reprocessing of spent nuclear fuel.

Kr-85 is widely used in industry and scientific research. In industry, it is employed in gas-filled lamps and discharge tubes, where its beta particles enhance the ionization process, improving lamp performance. Kr-85 is also used in leak detection systems, where its radioactive properties allow for precise detection of leaks in sealed containers, pipelines, and other industrial equipment. Additionally, it is used in density and thickness measurement for materials, particularly in manufacturing processes, by detecting the attenuation of beta particles passing through materials.

Krypton-85 is used in powerful gas discharge lamps, used in movie projectors. It is also found in neon lamps and neon lamp starters for fluorescent lamps, but the activity for one such starter is not dangerous—usually no more than 1 kBq. Krypton-85 is inexpensive and, if the gas discharge devices remain sealed, it is absolutely safe from radiation, which is why it was widely used in this area in the past.

Kr-85 is not naturally abundant and is primarily found as a byproduct of nuclear fission in reactors. It is present in trace amounts in the atmosphere due to releases from nuclear power plants, nuclear weapons testing, and reprocessing facilities. Kr-85 is encountered in controlled environments such as industrial facilities using it for specialized applications, as well as in research laboratories studying radioactive gases. Its production and use are carefully regulated to minimize environmental and health impacts.

Significant amounts of krypton-85 are produced in the production and isotope separation of plutonium. Therefore, a sudden local increase in the concentration of this radioisotope in the air is an indicator of possible illicit plutonium production.