Study on the burn-up characteristics of a thermal neutron filter containing B4C particles for NTD-Si irradiation

We investigated an alternative irradiation method for silicon doping using a thermal neutron filter to increase the irradiation efficiency in the Japan Research Reactor No. 3 (JRR-3). Aluminum mixed B4C particles were adopted as the filter material. The burn-up characteristics of a thermal neutron filter containing a large number of B4C particles are described. We have developed a method for evaluating neutron transmissivity as Boron burning in the neutron filter and clarified the applicable scope of the method via experiments using thermal neutron filters. We derived a method by which we could calculate the suitable diameter and density of B4C particles.

► We examined the burn-up characteristics of a thermal neutron filter containing a zillion B4C particles.
► A method to evaluate the transmissive neutrons during B4C burn-up was proposed.
► The STGM calculations were compared well with those of experiments under the condition that B4C density was less than 3 wt.%.
► The effect of B4C particle size distribution was not strong under the condition that B4C density was less than 3 wt.%.