Simulation of a suitable neutron and gamma shield for IECF device in different working modes by MCNPX code and studying its lithium production

In this work, the IECF device using the MCNPX code was simulated and parameters such as lethargy as well as cross-sections, changes in neutron flux and dosimetry and suitable multi-layer shields were studied. To secure the device from radiation hazards at different work intensities and in addition to the role of shielding, the role of producing materials such as lithium, the required simulations were done and the necessary shield thicknesses were determined. From the intensity of 106s−1 which is used for nuclear laboratories in universities up to neutron production 1012s−1 which is used for the BNCT method, an optimal shield thickness is required. For the first layer, a material with an average mass number was chosen to absorb the highest amount of energy and produce the lowest amount of gamma in inelastic scattering with fast neutrons. The produced gammas are also absorbed by concrete. For the thickness changes of different layers, in addition to measuring the remaining energies in the neutron flux, the cross-sections corresponding to those energies were also measured in order to calculate the required shield thicknesses for different powers of the device in different working conditions. After determining the type of different materials suitable for shielding, dosimetry was performed according to the ICRP60 standard and by making the necessary changes in the thickness of the layers, the neutron and gamma doses were reduced to the standard level. Also, the fluxes of thermal, epithermal and fast neutrons were measured in different shielding layers. Finally, for all calculated neutron production intensities, the necessary shielding thickness was determined for safe operation of the device. As a result of this study, by modifying and improving the method of determining the required thickness of the shield for different intensities, the smaller and more suitable thickness for the intensity of 109s−1 was determined. This improvement and reduction in the thickness of the shield caused a reduction in the weight of the total shield and a reduction in the cost of shield construction while maintaining radiation safety according to ICRP60 standards. The idea of lithium production by IECF device using the materials of this shielding was simulated by MCNPX code. Boric acid was investigated and studied as a suitable material for lithium production. After performing the simulation and calculations, the amount of 1 Kg of lithium per month of device working for 8 h per day was obtained which is a valuable amount and it is possible to increase its production.