Optimizing the performance of a neutron detector in the power monitoring channel of Tehran Research Reactor (TRR)

In this study, a general theoretical model is presented to calculate the current–voltage characteristics and associated sensitivity for a fission chamber. The chamber was used in a research nuclear reactor and a flux-mapping experiment was performed. The experimental current measurement in certain locations of the reactor was compared with the theoretical model results. The characteristic curves were obtained as a function of fission rate, chamber geometry, and chamber gas pressure. An important part of the calculation was related to the operation of the fission chamber in the ionization zone and the applied voltages affecting two phenomena, recombination and avalanche. In developing the theoretical model, we used the MCNP Monte Carlo code for fission rate and the SRIM program for ion-pairs computations. The theoretical model together with the above-mentioned codes was used to evaluate the effects of different applicable variations on the chamber's parameters.