Investigation of the recombination losses in a three-electrode cylindrical ionization chamber developed for gamma ray dosimetry of fission product activity

A three-electrode ionization chamber has been designed and developed for the gamma ray dosimetry of fission product activity and reported elsewhere. In this paper, the (I, V) characteristics of the chamber filled, with argon gas at 1.24 MPa (180 psi) pressure, for fission product gamma rays from spent fuel have been studied. To do so, the chamber was irradiated with gamma rays using different numbers of (i.e. up to 4) spent fuel elements. The plateau region is reached above 1200 V and the detector operating voltage is found to be 2 kV. It is observed that in the plateau region the slope increases with an increase in the exposure rate. The (1I, 1V) and (I, 1V2) characteristic curves reveal the presence of the initial and volume recombination losses. The volume recombination losses are found to be smaller than the initial recombination losses. Both these losses increase with the increasing exposure rate but the increase in the volume recombination losses is slightly greater than that of the initial recombination losses.