Production of two-layer composites using hot press molding technique and investigation of their ionizing radiation shielding properties

In this thesis, micron-sized tungsten (W) and molybdenum (Mo) powders were incorporated into a polylactic acid (PLA) matrix at different weight ratios (5%, 10%, and 20%) using the hot press molding technique, and the effects of these additives on the shielding performance against gamma and neutron radiation were investigated. Initially, single-layer PLA–W and PLA–Mo composites were fabricated, and then a two-layer hybrid structure was formed by combining the PLA–W20 and PLA–Mo20 samples, which exhibited the highest gamma radiation attenuation capacity. The gamma radiation interaction parameters of the produced samples were evaluated through experimental measurements performed with an HPGe detector, theoretical calculations using the WinXCOM software, and Monte Carlo simulations conducted with the GEANT4-FLUKA codes. For neutron interactions, effective neutron removal cross-sections were calculated and GEANT4-FLUKA Monte Carlo simulation programs are used. The results revealed that increasing the additive ratio significantly enhanced the mass attenuation coefficient and radiation protection efficiency. The highest gamma shielding performance was observed in the 20% reinforced samples. Additionally, it was determined that increasing the layer thickness improved the overall shielding performance, as thickness directly affected the attenuation rate of radiation within the material. However, an increase in secondary radiation generation was also observed with increasing thickness. Based on annual effective dose calculations, it was found that the developed two-layer structures remained well below the permissible dose limits. These findings demonstrate that PLA-based composites, with their environmentally friendly, lightweight and non-toxic characteristics, can serve as promising alternative materials for radiation shielding applications.