抄録
The present paper describes monitors for the detection of β-ray and γ-ray radionuclides in He gas recovered from the cryogenic irradiation equipment reported in the preceding publication (I).
The γ-ray monitor consists of a 2″×2″φ Nal (Tl) scintillation counter in the monitor vessel and the β-ray monitor is composed of thin box-type ionization chambers piled in three layers which can measure separately the radioactive concentrations of the groups consisting of low, medium and high energy β-emitters.
The performance tests of these detectors revealed a typical sensitivity of 3.5×10-3Bq/cm3 for a low energy β-emitter such as tritium in He gas. In addition, satisfactory selection of the three energy groups of β-emitters was demonstrated using 133Xe in the β-ray monitor.
