Investigations of the vaccum system with a orifice in the hydrogen concentration meter; Studies of leak detector developments on LMFBR's SG

Kuroha, Mitsuo; not registered; Daigo, Yoshimichi; not registered

One of PNC designed in-sodium type hydrogen meters which have been developed to use as the water leak detectors for the Monju's steam generators was modified in the vaccum system in order to measure the pumping speed of the ion pump during the operation. The modification was to increase the pressure drop between the ionization vaccum gauge and the ion pump by installing a orifice in front of the ion pump. As the result, it could be attained to estimate accurately the permeability factor K for the hydrogen through Ni membrane. The factor of K obtained is 110 cm Torr/sec, and the pressure dependence in the low pressure range is rather smaller than published datas. It is found through the disccusions that the relationship between P (partial pressure of hydrogen in sodium) and the measured pressure P (pressure in vaccum side) is not expressed empirically by the half-power low, but followed by the pressure dependence of K reported. The best pair of the Ni membrane area and the orifice conductance is disccusd to dynamic vaccum system of the PNC designed in-sodium hydrogen meter. Also, it is concluded for the in-sodium hydrogen meter with a orifice using in the Monju's operation conditions that less than a quater of Ni membrane area adopted at present is usefull, and more than one year of the ion pump operation period without the change of the calibration curve can be attained.