Determination of Neutron Flux and Neutron Fluence from the Signal Current of a Self-Powered Rhodium Detector

Self-powered neutron detectors are suitable for continuous flux measurements and were used to monitor some of Gulf General Atomic’s irradiation experiments in the Engineering Test Reactor in connection with the development of fuel for high temperature gas-cooled reactors. For the purpose of detector current data reduction, the special case of a rhodium detector is analyzed and explicit solutions for the neutron flux and neutron fluence are developed. The solutions describe the time-dependence of flux and fluence for detector irradiation times ≳1 h. Independent variables are the detector current and its time derivative, both of which are functions of time. Constants appearing in the equations are the neutron flux, the corresponding electrical current and its time derivative at the time of calibration, the decay constant of 104Rh (4.36 min), and the effective cross section for 103Rh(n,γ)104Rh reactions.