Development of a new Monte Carlo based transport code to calculate photon exposure build-up factors in various shielding arrangements

Abstract

A Monte Carlo method based gamma transport code MCBLD has been developed to estimate gamma exposure build up factors and dose rate in single, multi-layer shielding arrangements. Various gamma photon interactions like photo electric effect, bound electron coherent scattering (Thomson), bound electron incoherent (Compton) scattering, pair production and annihilation gamma photons have been considered. Exposure buildup factors for various shield materials like water, iron, lead, and uranium, ordinary and heavy concrete have been evaluated for various thicknesses as well as for different energy. Results have been compared for different codes/methods like EGS4, MCNP, CAPO, and GP fitting method. The double layer buildup factor is the building block of the empirical formulae used to calculate multilayer buildup factor. These empirical formulae are established mostly by fitting single material buildup factor data obtained using Monte-Carlo method based code. To check the validity of MCBLD code, Double layer transmission exposure buildup factor (DEBF) has been calculated and compared for water-iron system. This MCBLD code has also been utilized to evaluate the dose rate for multi-layer shielding problem consisting of water, iron and lead.