Extraction of theoretical equation for the gamma ray buildup factor of the three-layered spherical shield

In the previous researches, several theoretical equations were presented for calculation of buildup factor of the single layer shields. Also, the theoretical equations were offered for the two-layered shield that consist of the known materials. For other possible modes of the multi-layered shield, the buildup factor are usually calculated via experimental or simulated data. The purpose of present study is the extraction of the new theoretical equation for the gamma ray buildup factor of three-layered spherical shield made of water, concrete and iron based on the Monte Carlo calculation. To this end, the gamma ray buildup factor of the three-layered spherical shield is calculated via simulation by MCNPX computational code. Finally, the theoretical equation for gamma ray buildup factor of three-layered spherical shield vs. gamma ray buildup factors and thickness of the single-layered shields is extracted through curve fitting and regression.