Simulation of a new neutron calibration laboratory in Brazil using MCNP5

Metrobras, a private company in Brazil, is developing a new laboratory for the calibration of neutron detectors in collaboration with the National Laboratory for Metrology of Ionizing Radiation (LNMRI). This work aimed at assessing neutron spectra, ambient dose equivalent rates, and neutron scattering in the calibration room of Metrobras Neutron Detectors Calibration Laboratory (LCDNM) using Monte Carlo simulation with MCNP5. Three models were simulated: vacuum, air, and the complete with the several materials employed in the actual room. Neutron spectra as a function of the distance from the source were obtained, compared, and used to calculate ambient dose equivalent at different points in the calibration room and results were compared to other neutron laboratories. Results show that LCDNM ambient dose equivalent rates are comparable to those of other neutron laboratories with 531.2 μSv . h^-1 at 100 cm from the 592 GBq activity ²⁴¹AmBe source. This work shows that LCDNM may be used as a calibration laboratory for neutron detectors in accordance with ISO 8529.