Secondary Standardization of Neutron Fluence Fields at the Argonaut Reactor - IEN: Assessment of Calibration and Irradiation Metrological Capacity for Samples and Instruments

Abstract

This article evaluates the secondary standardization of neutron fluence fields at the Argonaut Reactor of the Nuclear Engineering Institute (IEN). The study focused on the utilization of the Bonner Sphere Spectrometer (BSS) to determine the neutron spectrum at different positions of the lateral channel (plug 1) of the reactor, essential for characterizing radiation fields in complex environments. Measurements were conducted at varying distances (100 cm to 250 cm). The decrease in counts with increasing diameter indicated a higher presence of neutrons in the absorption energy range (0.1 eV to   2 MeV) for the 2", 3", and 5" spheres, but the 3" sphere exhibited different behavior, suggesting a greater presence of neutrons between 0.1 eV and 700 keV. As the BSS was moved away from the neutron source, the reduction in counts was expected. However, for the 8", 10", and 12" spheres, the analysis revealed a convergence of curves to a union of values between 0.1 eV and 6 MeV. These findings highlight the importance of precise neutron fluence characterization for dosimetric calibration. The data also serve as a basis for validating computational models in neutron metrology, contributing to the enhancement of nuclear research infrastructure. The Precision Long Counter (PLC) will be set up in future studies to complement BSS measurements, further advancing neutron detection capabilities.