Investigation on distribution of radioactive substances in Fukushima, 5; Comparison of dose evaluation calculations for bremsstrahlung photons caused by high energy rays using PHITS and GEANT4 codes

Shikaze, Yoshiaki 

Among the radioactive nuclides emitted inside the nuclear reactor buildings by the Fukushima Daiichi nuclear reactor accident, high-energy beta-ray sources such as strontium-90 and yttrium-90 generate bremsstrahlung photons in the materials which constitute wall, floor and interior structure of the building. Therefore, evaluation of the bremsstrahlung radiation dose to the workers in the nuclear reactor building is important for radiation exposure management. To investigate calculation precision of the bremsstrahlung dose evaluation, the results of PHITS and GEANT4 codes were compared. In the calculation, behind various shielding plates the water cylinder was set, and the deposited energy spectrum and absorbed dose in the water cylinder by the bremsstrahlung were compared in this presentation.