高感度熱量計によるトリチウム量の絶対測定(1) : 熱量測定システムの設計・製作及び性能試験

概要

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A calorimetric system for evaluation of the absolute amount of tritium was designed and constructed, and its basic performance was tested. A calorimeter can be used to measure total energy of radiations as a calorific value. The present calorimetric system consists of a twin-type thermal conductivity calorimeter equipped with a vacuum shielding, a tritium container, total pressure gauges, a quadrupole mass spectrometer, and high-vacuum systems. A calibration curve of the calorimeter was prepared at first using two samples enclosed a given amount of Zr-Ni alloy powder only, and the following linear relation was obtained: Eout = (0.2694±0.0010) Qin, where Eout is the output (μV) from the heat sensors and Qin is the input power (μW) by Joule heating to the sample cell. In addition, the lower detection limit was estimated to be 0.15 μW from stability of the calorimeter, which corresponds to the tritium amount of 0.16 GBq. As an initial test, Zr-Ni alloy powder loaded with a given amount of tritium was used and the amount of tritium was estimated to be 26.3 GBq, which was slightly less than the tritium activity determined previously by using a small ionization chamber.
富山大学の論文