Estimation of the neutron flux in the irradiation channels of a Hotwizer containing a ²²⁶Ra-Be source

Neutron irradiators using isotopic sources (Neutron Howitzer) are useful tools for elemental analysis by neutron activation, radiosensitivity studies, and detector calibration, among others. For its applications, knowledge of the neutron flux and its associated energies at the irradiation site is required. The objective of this work was to experimentally determine the flux of thermal and epithermal neutrons in the channels of a Howitzer, using the activation method of uncovered and covered gold foils with cadmium filters. The irradiation time was greater than 14 days due to the low mass of the gold samples and the relatively low neutron flux. Using the gamma spectrometry technique, the radioisotope ¹⁹⁸Au was identified by its 411.8 keV energy peak, whose net area was used to estimate the activities of gold foils. Applying the cadmium difference method, the thermal and epithermal neutron fluxes were estimated independently. Results showed thermal neutron fluxes higher than the epithermal neutron fluxes in the evaluated irradiation channels. (author)