Statistical discrimination based monitor for radioactive gases and vapors

The statistical discrimination method is based on the dependence of the k-factor on the relative values of the ionization current components in a mixed nuclear radiation field. Although the functionality of the schemes using the statistical discrimination method for measuring different radioactive gases and vapors is not the same, the basic structures are quite similar. They all consist of a gas flowing ionization chamber (with a sampling pump), a preamplifier, a data acquisition system and a personal computer. As a consequence, a multifunctional monitor for radioactive gases and vapors has been taken into consideration. A special designed software allows for tuning the monitor on different gases (vapors) and on the associated radiation field (i.e. natural radiation background or gamma-ray field). The experimental dependence of the gamma perturbed radon volume activity measurement on the (unperturbed) radon volume activity, for a perturbing superposed 10 μGy/h gamma-ray field, proves that the gamma-ray field does not change the measured radon volume activity values, in the frame of the assumed uncertainties. The uncertainties increase, from about 10 % for volume activities exceeding 500 Bq/m3 to 26% for the lowest (29 Bq/m3) measured volume activity. An analog experimental dependence for tritium in a gamma-ray field led to similar conclusions. (authors)