A Monitor for the Separate Determination of HT and HTO

We have constructed a prototype monitor that discriminates between tritiated water (HTO) and tritiated hydrogen (HT) in air. The separate determination of these two species is based upon their different permeation rates through the polymer Nafion (DuPont). A single diffusion stage using this material is sufficient to reduce the concentration of HT relative to HTO by a factor of 103 while still maintaining an acceptable time response. The HTO contribution to the measured HT concentration is also small. The electronic and mechanical design of this monitor is outlined and some preliminary test results presented.