Comparison Of Gamma Ray Shielding Strength Of Lead, Aluminium And Copper From Their Experimental And MCNP Simulation Result
Nwosu, O. B
Keywords: Nuclear radiation shielding, gamma rays, MCNP simulation, linear attenuation coefficient
Abstract: Gamma ray shielding experiments and simulation of it with MCNP code was carried out with three metallic materials; Copper, Aluminium and Lead using 10mCi 0.662KeV Cs-137 gamma ray source. The study was to understand the attenuation strength of these materials in relation to one another; and the behaviour of the emergent photon intensities in relation to the thickness of the shield. These materials of different thicknesses were placed in turns behind the radiation source and the emergent radiation was counted using NaI (TI) detector. These arrangements were again simulated using MCNP4c codes and the results equally presented and compared with that from the experiment.It was discovered that photon shields, unlike those for charged particles, are governed by the exponential decay law and the flux of shielded photons is a complex mixture of scattered and unscattered photons; and that increase in the thickness of the absorber lowers the photo peak intensity detected.It was equally noticed that while only 0.6cm thickness of lead was required to reduce the gamma photon intensity to half of its original value, about 1.8cm of Copper and 3.6cm of aluminium was required to do the same work lead has done, showing lead as a far better absorber of gamma photon than copper and aluminium and can be used to shield against gamma ray; in turn, copper is a better absorber than aluminium. The relationship in the absorbing properties of these three materials in terms of their half thickness th1/2could be expressed thus:th1/2lead =1/3th1/2copper = 1/6th1/2aluminium. Interesting to note isthe striking similarities between the two sets ofgraphs fromMCNP simulation and experiment.This goes to show the simulation work as veritable tool for modelling certain real life situations, and very useful in particles transport equations.
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