Characterization of neutron detectors at the IPEN/MB-01 nuclear reactor

A huge Brazilian nuclear project, the Brazilian Multipurpose Research Reactor (RMB), is being carried out and one of the project steps is to verify experimentally the physical quantities related to the operational performance of the new fuel elements. In this context, the aim of this work is to characterize the neutron detectors due to its crucial role during the nuclear reactor criticalization. A series of experiments was performed at the IPEN/MB-01 nuclear reactor in order to characterize a set of new helium-3-filled gas proportional counters. The detectors characterization procedure takes into account the operating voltage curve and the detectors dead time. The Rossi-α method was employed in order to acquire the time difference between a detected neutron pair. The dead time determination through the Rossi-α method is very important to discriminate the reflector effect over the neutron lifetimes in subcritical reactivity levels. Furthermore, the Auto Power Spectral Densities (APSD) for those new detectors were experimentally acquired and those results were compared among some well-known detectors and with theoretical simulation results using the MCNP5 code with the ENDF/B-VII.0 library neutron data.