Investigation of X- and gamma ray photons buildup in some neutron shielding materials using GP fitting approximation

In the present work, the gamma ray energy absorption (EABF) and exposure (EBF) buildup factors have been calculated by using the five parameter geometric progression (GP) fitting formula for some neutron absorbent materials (H3BO3, Na2H4O7, NaCl) and neutron moderator hydrocarbons (C5H12, C6H14, C7H16, C20H42, C40H82) in the energy region 0.015-15 MeV up to a penetration depth of 40 mfp (mean free path). From the results, it has been concluded that the buildup of photons is less in NaCl when compared with other materials for the lower penetration depths (<15 mfp for EABF, <10 mfp for EBF) whereas for photon energies higher than 3 MeV less buildup of secondary gamma rays occur in HC based materials than the other ones at higher penetration depths (>15 mfp for EABF, >10 mfp for EBF). The present results have been compared with MCNP calculations for various energies at 1 mfp and a good correspondance has been obtained. (c) 2012 Elsevier Ltd. All rights reserved.