Design calculation of a vertical thermal neutron beam for neutron radiography at Esfahan MNSR

In this paper, the MCNPX code is applied for feasibility study of using the Isfahan MNSR as a neutron source for neutron radiography. To produce a good neutron beam in terms of intensity and quality, the aluminum (Al) with thickness of 0.7 cm, and bismuth (Bi) and lead (Pb) with thickness of 1 cm are used as the fast neutron filter, and the gamma filter, respectively. The L/D ratio of the designed neutron radiography facility is 90 and the diverging angle is 2.1degree. The thermal neutron flux, the ratio of thermal neutron to gamma dose rate, and the thermal neutron content at the beam exit plane are evaluated 1.47E+05 n/cm2.s,  2.96E+06 n/cm2.mR, and 92.5%, respectively. If such thermal neutron beam is built in Isfahan MNSR, many practical and scientific applications of the NR would be realized.