Energy Absorption Buildup Factor Studies In Some Soils

Abstract

An attempt is made to generate effective atomic number, energy absorption buildup factor (EABF) in the energy region 0.015-15.0 MeV up to a penetration depth of 40 mfp for some soils. The five parameters geometrical progression (G-P) fitting approximation has been used to calculate energy absorption build-up factor (EABF). The generated energy absorption buildup factors has been studied as function of incident photon energy & penetration depth and represented graphically. Index Terms: Energy absorption build-up factor (EABF), Mean free path (mfp), Effective atomic number (Zeff ), Equivalent atomic number (Zeq). I. INTRODUCTION Today, to benefit mankind, the radiations are used in basic sciences, medicine, and industry and for generating electricity Gamma radiations occupy the highest energy among the electromagnetic radiations. The exposure to gamma radiations with human body can occur during radiological diagnosis , nuclear reactors & nuclear research establishments .The use of radiations can be biologically hazardous, there is need of restrict and controlled exposure of human beings to these radiations by using shields of proper dimensions and of an appropriate material. The study has been focused on build-up factor which plays major role during interaction of gamma rays with the chosen soils. Nuclear accidents due to natural and manmade disasters cannot be refused in future. To avoid any hazard from day to day exposure of radiation the choice of material is very important for the purpose of shielding of radiations. People involved in industries, institutions & research labs may be the victim of gamma ray exposure. For the safety of people & selection of shielding materials, build-up factors study become important. When gamma radiations interact with material through Compton scattering. The scattering results in accumulation of photons in the interacting material due to which the number of photons buildup in the materials. Two types of build-up factors namely energy absorption build-up factor (EABF) & exposure build-up factor ( EBF). The concept of buildup factor was mutually introduced by White (1) and Fano (2) recognized its importance in attenuation studies.To calculate build-up factor there are different methods like G.P. fitting method. Harima et al. 1986 (3), invariant embedding method, Shimizu, 2002 (4); Shimizu et al., 2004 (5), iterative method, Suteau and Chiron, 2005 (6) and Monte Carlo method, Sardari et al., 2009 (7). Recently American National standards ANSI/ANS-6.4.3(8) has provided buildup factor data for 23 elements, one compound and two mixtures (i.e. air and water) and concrete at energies in the range 0.015-15 MeV up to penetration depths of 40 mfp by using the G.P method. D.Sardari and S. Baradaran 2010 (9) calculated buildup factor of gamma and X-ray photon the energy range of 0.2-2.0 MeV in water and soft tissue using Monte Carlo code MCNP4C. The results are compared with buildup factor data of pure water. In each case very small deviation is observed. There are successful contributions which are based on the buildup factor studies in some soils and ceramic materials available in the literature. For example, Brar et al. (10) have studied the variation of buildup factors of soils with weight fractions of iron and silicon. Sidhu et al. (11) have studied the energy and effective atomic number dependence of the exposure buildup factors in biological samples. Manohara et al. (12) studied the variation of exposure buildup factors for heavy metal oxide glass with photon energy and penetration depth. Singh et al. (13) studied the energy dependence of total photon attenuation coefficients of composite materials Sidhu et al. (14) have studied the energy and effective atomic number dependence of the exposure build-up factors in biological samples J. S. Dhillon et al.(15) have studied Gamma Ray Photon Energy Absorption build-up Factor In Some Soil II.