Investigating the radiation protection properties of new heavy nanoconcretes for using in the construction of megavoltage radiotherapy rooms

Abstract

High density concretes are used to build radiation therapy bunkers to increase the available space. Adding neutron and photon attenuating compounds in the form of nanoparticles to concrete improves the attenuation of photons and neutrons. Material and Methods: The Monte Carlo MCNPX code was used for the simulation. The linear attenuation coefficients of nanoconcretes containing Osmium, Iridium and Barite were calculated for the photon energy spectra of 6 and 18 MV and the energy of cobalt 60. Neutron Macroscopic cross sections of nanoconcretes containing Gadolinium oxide, Graphite, Cadmium oxide and Ammonium paratungstate were calculated for fast neutron beam energy. The scattering fluences of photons and neutrons were calculated for nanoconcrete samples. The photon and neutron fluences reached the beginning of the maze and the entrance door of the maze were calculated for nanoconcrete samples containing Ammonium paratungstate and Osmium for the photon energy spectra of 18 MV and the neutron energy spectra output from the linear accelerator. Results: Nanoconcrete containing 30% Barite, with 27.57% and nanoconcrete containing 30% Osmium, with 26.82%, showed the highest linear attenuation coefficient compared to ordinary concrete for the photon energy spectra of 18 MV. Nanoconcretes containing Ammonium paratungstate showed a higher macroscopic cross section at all neutron beam energies than other samples. For both 6 and 18 MV photon energy spectra, the nanoconcrete sample containing 20% Ammonium paratungstate and 20% Osmium showed the highest photon scattering fluences. The photon fluence reaching the entrance door of the maze of the radiotherapy bunker was 7.4 times lower when the walls were filled with nanoconcrete samples containing 20% Osmium and 20% Ammonium paratungstate than when the walls were filled with ordinary concrete. In the case of neutron fluence, this ratio was 1.7.