An Evaluation of the CRNL/CFFTP HT/HTO Discriminating Monitor

A prototype discriminating HT/HTO monitor was loaned to Harwell by CRNL to evaluate for possible use at the JET facility in the UK. The instrument was exposed to pure HT and HTO inputs at various concentrations, and its readings compared with those of a non-discriminating Harwell Ion Chamber (Model 1528) connected in series at the input. The rate of response, accuracy, separation factors and possible memory effects were studied at various humidities at ambient temperature, and the effects of varying process- and sample-air rates were investigated. Generally, the instrument was found to work well, although the response times for the HTO channel were generally rather slow (20–30 min to 90% of its asymptotic value), so that central sampling of a number of points in sequence via sampling lines and a manifold would be slow.