Measurement and modelling signals from an optical fission chambers during reactor irradiation

Nowadays, fission chambers are commonly used for neutron diagnostic in industrial pressurized water reactors. However, with the diversity of emerging nuclear power plant prototypes such as fusion, fast neutron or high temperature reactors, innovative neutron diagnostic system are developed by the French Alternative Energies and Atomic Energy Commission (CEA). Indeed, in some case the operating range of existing fission chambers will not be adapted to the measuring conditions. Thus, the CEA is developing a technology called optical fission chambers, where photons are collected instead of charged particles. This paper presents a macroscopic model of the signal-to-noise ratio of optical fission chamber measuring in neutron and gamma fields. Due to the novelty of this study, we expect to have a better understanding about the intensity of the different light sources. Secondly we aim to validate the developed numerical model by comparing the simulated spectra to the experimental ones. Finally, we highlight some design features which may improves the signal to noise ratio of optical fission chamber.