Answer to Question #1367 Submitted to "Ask the Experts"

Q

How can I measure the noble gas concentrations in the reactor building of a nuclear power plant?

A

There are commercial systems available for measuring airborne radiological effluents from nuclear power plants. Designs of these systems depend on if they'll be needed during normal release and/or accident scenarios. Stack monitors often use simple low- and/or high-range Geiger-Mueller (GM) tubes that have been calibrated to a "standard" fission product mixture. Alternately or in conjunction, a facility design may require extraction of a slip stream of the effluent, which is passed through a series of particulate air filter, iodine cartridge, and large volume chamber for noble gas measurement. To perform noble gas measurements in a reactor building, you need to consider the range of concentrations, what you might be monitoring or having contribute to the signal (that is, fission product radioactive xenon and krypton, activated argon or nitrogen, tritium, etc.), and what ambient background and spectrum might be expected at the detector element. I'd look at commercial equipment available, in particular flow-through chambers. This could be an ionization chamber or a chamber with a solid detector element (for example, NaI), where basic gamma spectroscopy and background subtraction could be performed. See our Society's list of affiliates for possible equipment. David J. Allard, CHP