Monte Carlo simulations of dose distributions and dose rates of uranium-238, thorium-232, and potassium-40 using PHITS

Ionizing radiation is naturally present in the environment in the form of the primordial radionuclides and their daughter products. Since overexposure to ionizing radiation is dangerous to the human body, it is vital that there is protection against this radiations. In this present study, PHITS simulations have been performed to model photon emission of U-238, K-40 and Th-232, and to investigate how natural photon attenuators such as water, iron, glass, concrete, lead and rubber affect the effective dose rates of these radionuclides. Under normal conditions, the effective dose rates of U-238, Th-232 and K-40 are 44.96 nSv/h, 48.10 nSv/h and 2.336 nSv/h respectively. Also, the effective dose rates of the radionuclides decrease by an average of 35.1% for concrete, 19.4% for natural rubber, 20.5% for water, 36.23% for plate glass, 73.5% for iron and 90.1% for lead.