A Comparative Calculation of Dose Rate Using Rad Pro Calculator for Shielding Requirements of Cobalt-60 and Cesium-137 Sources.

Abstract

A Comparative Calculation of Dose Rate Using Rad Pro Calculator for Shielding Requirements of Cobalt-60 and Cesium-137 Sources at CERT was carried out using seven shielding materials: Lead, Concrete, Iron, Uranium, Lead glass, Aluminum and Tungsten by the Rad Pro Calculator. The study was to understand the attenuation strength of these materials in relation to one another and the behavior of the photon dose rate in relation to the thickness of the shield. These materials of varying thicknesses were placed in between the radiation source and the detector and the dose rate were calculated. It has been observed that each of the results has a similar behavior, in that the photon dose rate is inversely proportional to the absorber thickness in an almost exponential form. As the absorber’s thickness increases, the photon dose rate decreases; conversely. From a given distance, the result of these seven  absorbing materials (Lead, Concrete, Iron, Uranium, Lead glass, Aluminum and Tungsten) look very similar, but on a closer look, one will identify a striking and important differences amongst these seven  materials especially tungsten. While only 6cm thickness of tungsten is required to reduce the photon dose rate of 5mCi of  ⁶⁰Co at 1 meter distance from the source to detector to 0.08µSv/h, 6cm of uranium thickness reduces it to 0.11µSv/h , 10cm of Lead glass thickness is required to reduce it to 0.08µSv/h,12cm of lead reduce to 0.07µSv/h,22 cm of Iron shielding reduce the dose rate to  0.07µSv/h,42cm of Aluminum shielding reduce the dose rate to 0.11µSv/h, 70cm of concrete shielding require to reduce the dose rate to 0.06µSv/h. This then goes to show that uranium is a far better absorber of ⁶⁰Co gamma photon when compared to tungsten, lead glass, lead, iron, aluminum and concrete can be used to shield against gamma ray. Conversely, 3cm of uranium shielding is require to reduce the photon dose rate of 22mCi of Cs-137 at 1m from the source to detector to 0.05µSv/h, 4 cm of tungsten to 0.07µSv/h, lead glass to 0.05µSv/h, lead to 6 cm to 0.07µSv/h, 16cm of iron shielding to 0.07µSv/h, 32cm of aluminum shielding to 0.09µSv/h, 55cm of concrete shielding to 0.08µSv/h.  In conclusion, Rad Pro Calculator simulation is a veritable tool for modeling certain real life situations, and very useful in shielding calculation. The  result have also show that out of the seven  materials, tungsten and uranium is a better shield because it requires just a few thicknesses of it to cut down the photon dose rate to acceptable limit, then followed by lead glass, lead, iron, aluminum and concrete being the least