Development of an Extra-Trees-Based Program to Calculate Gamma-Ray Exposure and Energy Absorption Buildup Factors

Abstract The calculation of gamma-ray energy absorption and exposure buildup factors is studied in this paper. The GP formula requires logarithmic interpolation calculation about the photon energy and the equivalent atomic number of the material in the interpolation calculation of the fitting parameters, which leads to a complicated process of calculation of the buildup factor. In order to solve this problem, a program for buildup factor calculation based on the Extra-trees regression algorithm has been developed in this work, which can calculate the energy absorption and exposure buildup factors by inputting the photon energy and the elemental composition of the material. The code was validated across a wide range of materials by calculating the buildup factors for a variety of mixtures/compounds, including water, air, concrete, human tissues, and bricks. The tests show that the results of the program are in good agreement with the values from the ANS, GP formulas, and MCNP program. Moreover, the accuracy of the Extra-trees regression model is improved in this paper by using the GP formula to generate the buildup factors of elements 4–92 as a training set compared to using ANS data.