A radiation shielding study for radiotherapy rooms: an application for barium concrete

To ensure the protection of individuals, different materials have been used as shielding from ionizing radiation, among them the barium sulfate (barite) stands out for presenting good attenuation of photon beams for distinct energies, including those used in radiotherapy. In this context, this work provides three compositions of barium concretes: T.REF (reference), T.10% SA (with 10% replacement of Portland cement with silica fume) and T.10% CV (with 10% replacement of Portland cement with fly ash) to investigate shielding effects against ionizing radiation generated by radiotherapy equipment. Concrete samples were characterized with respect to bulk density and axial compression strength. Regarding the effectiveness of the shielding, measurements of attenuation of the primary beam generated by a linear accelerator were carried out, for maximum acceleration voltages of 6 MV and 10 MV, as a function of the thickness of the samples. The density measurements show that the concretes were classified as 'normal' as stated in NBR 8953. In the compressive strength tests, the concretes were in line with structural and severity criteria, according to NBR 6118. Concerning the shielding of ionizing radiation, the barium concrete T.10%CV showed the greater efficiency among all the proposed compositions, reducing the thickness of the wall of radiotherapy rooms by 80.91% with an attenuation of 95% of incident radiation. This trace is composed of fly ash, a residue from the burning of coal in thermoelectric plants. Therefore, in addition to proposing a reuse method and an adequate destination for solid waste, it was possible to reduce the consumption of clinker; the material responsible for most gaseous emissions in the cement manufacturing process. Furthermore, other barium concretes as T.REF and T.10%SA also proved to be suitable for application in protective barriers in radiotherapy rooms, although they presented lower attenuations than T.10%CV. (author)