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KRYPTON GAS CYLINDERS AS A SOURCE OF RADIATION

Fischer, Helmut W.*; Bielefeld, Tom*†; Hettwig, Bernd*

doi: 10.1097/HP.0b013e3181d94ed8
Paper

A standard 40 foot shipping container with a cargo of pressurized krypton gas in 159 steel cylinders, which had triggered a radiation alarm, was investigated to address radiation safety and illicit nuclear trafficking concerns. The investigation included contamination and dose rate measurements as well as in situ high resolution gamma spectroscopy. The dose rate measurements gave a maximum value of 0.07 μSv h−1 above background (0.08 to 0.11 μSv h−1) on the cylinder surface and no detectable increase above background at distances of 1 m and higher. Contamination monitor readings showed a similar relative increase (plus 8 cpm) above background (about 12 cpm) to the dose rate readings. Quantitative gamma spectroscopy revealed a contamination of the gas with 85Kr at a level of 3.5 × 105 Bq kg−1. This value was found to be consistent with analytical and numerical estimates based on current data for atmospheric 85Kr, which is captured from ambient air together with stable krypton during the production process. This incident demonstrates an apparent lack of radiation-related knowledge by those who handle krypton gas, as well as by border control personnel and emergency responders. We therefore propose to improve labeling and documentation standards for such shipments. This effort may be facilitated by introducing the new category of “technically enhanced artificial radioactive material,” or “TEARM” (similar to the existing “naturally occurring radioactive material” or “NORM” and “technically enhanced naturally occurring radioactive material” or “TENORM” categories).

* University of Bremen, Department of Physics, Bremen, Germany; Belfer Center for Science and International Affairs, Harvard Kennedy School, Cambridge, MA.

For correspondence contact: Helmut W. Fischer, University of Bremen, Institute of Environmental Physics, Otto-Hahn-Allee 1, D-28359 Bremen, Germany, or email at hfischer@physik.uni-bremen.de.

(Manuscript accepted 15 February 2010)

©2010Health Physics Society