Stability of NaI(Tl) Detector for Tritium Monitor of BIXS Use to Hot Environment

Beta ray induced X-ray spectrometry (BIXS) is one of the methods applicable to tritium gas monitor. It can measure tritium by counting the X-ray that is induced by interaction between the beta ray of tritium and the materials. Tritium gas monitor of BIXS use installed into Tritium Process Laboratory (TPL) in Japan Atomic Energy Agency (JAEA) uses NaI(Tl) as the scintillator. In this work, the NaI scintillator and the photo-multiplier that can work at 150°C have been installed instead of the ordinary scintillator and photo-multiplier. And, the sample gas such as He, T₂, or T₂ (1%)/He mixture was introduced into the tritium gas monitor kept at 120°C. Then, the counting rate was observed. The counting rate at 120°C was about a half of that at the room temperature. The counting rate after the heating was almost same with that before the heating. So, the deterioration of the scintillator by the heating has not been observed.