Error evaluation in hydrogen isotope permeability measurement and the required degree of vacuum

In the measurement of the hydrogen isotope permeability of Silicon-Carbide, control and the evaluation of the wraparound through the sample holder is important problem. For this purpose, the heated holder part is enclosed by a glass tube and kept at vacuum during experiments, but detail examination about required degree of the vacuum has not be made. In this paper, the amount of the wraparound flow was evacuated by experiments and model calculations. It is found in the experiments, the flow rate from glass tube to the low pressure line is linear dependence on the tube pressure at 0.1~100 Pa, although that from high pressure line into the glass tube is proportional to square-root of pressure of the high pressure line as expected. The ratio of the wraparound flow to the mail flow during permeation measurement condition was estimated to be 6~10 % from the extrapolation of experiments results. On the other hand, the model calculation results were still one order higher than observed even when first-order dependency was assumed. The impurities on outer surface of the holder or gas are considered to limit the permeation in the experiments.