Characteristics of a promising tritium process monitor detecting bremsstrahlung X-rays

The characteristics of a tritium process monitor detecting bremsstrahlung X-rays with a NaI(Tl) scintillation counter were examined with pure tritium in a concentration range of 102–108 GBq/m3. The measurement principle of this type of tritium process monitor is observing the bremsstrahlung X-rays generated by the interaction between beta particles from tritium and a gold film coated on the inner surfaces of a small measuring cell. A linear relationship between the counting rate of bremsstrahlung X-rays and the tritium concentration was observed for the concentration range of 102–106 GBq/m3, and the sensitivity of the monitor was determined to be about 0.5 GBq/m3/cpm in this concentration range. A linear response of this monitor was also observed for a tritium mixture diluted with deuterium. In addition, as an example of its practical use, this monitor was confirmed to be applicable to tracing 3He release from a uranium bed during heating. These results show that this type of tritium monitor is very promising as a process monitor for the fuel processing system of fusion reactors.