85Kr

85Kr is a radioactive isotope of krypton (atomic number 36) with a mass number of 85. It decays by beta minus emission to rubidium-85, with a half-life of 10.76 years. The decay process releases beta particles and, occasionally, gamma radiation from the excited state of the daughter nucleus.

85Kr is produced as a fission product in nuclear reactors and during the reprocessing of spent nuclear fuel. It also occurs in trace amounts in the atmosphere from natural processes, but the anthropogenic contribution has increased since the mid-20th century due to nuclear activities. As a noble gas, 85Kr cannot react chemically and can mix with air and other gases.

Because of its inert nature and beta emission, 85Kr is used as a tracer gas in leak-testing procedures for sealed containers and pipelines, and in the calibration of radiation detectors and various gas-flow experiments. It is valued for its ability to be detected without chemical interaction with the surrounding materials.

Exposure to 85Kr is typically a concern only if the gas is inhaled in significant quantities; external exposure is generally low due to its low energy beta emission. Its long half-life means it persists in the environment for decades after release, so releases are regulated and monitored under nuclear safety and environmental policies, with containment and filtration used in facilities handling krypton isotopes.

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