85Kr in Industrial Krypton Gas: Origin, Identification and Dosimetry

Industrial krypton gas is produced by fractionated distillation of liquefied air, in which it has a natural abundance of about 1 ppmV. The radioisotope 85Kr is present in the atmosphere at a concentration of about 1.5 Bq/m3, due to continuous emissions from nuclear installations. Pure krypton gas thus will contain 0.35 MBq/kg of 85Kr, and gas cylinders will contain many MBq of the isotope, making it detectable by radiation monitors. A case of an explosion of such a cylinder inside a facory building with subsequent detection of increased radiation levels by the fire brigade, followed by evacuation of the building and decontamination of persons, is reported in the U.S. press.

We report on a case of transcontinental transport of krypton gas, triggering of a radiation alarm and subsequent in situ measurement by different radiometric techniques. Quantitative in-situ gamma spectroscopy identified the isotope 85Kr and revealed activity levels consistent with its atmospheric concentration and with measured and calculated dose rate values.

Possible other cases of such "TEARM" (technonogically enhanced artificial radioactive material) and possible techniques for detection and discrimination from attempts of nuclear smuggling are discussed.