SU-E-T-264: New Concrete Designed and Evaluation for Megavoltage X Radiotherapy Facilities (CONTEK-RFH2).

PURPOSE The most common material for shielding is concrete, which can be made using various materials of different densities as aggregates. New techniques in radiotherapy, as IMRT and VMAT, require more monitor units and it is important to develop specifically designed shielding materials. METHODS Arraela S.L. has developed new concrete (CONTEK®-RFH2), which is made from an arid with a high percentage in iron (> 60%), and using the suitable sieve size, enables optimum compaction of the material and a high mass density, about 4.1-4.2 g/cm3 . Moreover, aluminate cement, used as base, gives high resistance to high temperatures what makes this product be structurally resistant to temperatures up to 1200 ° C. The measurements were made in a LINAC Elekta SL18 to energies 6MV and 15 MV with a field size of 10×10 cm2 for concrete samples in the form of tile 25cm×25cm with variable thickness. RESULTS The linear attenuation coefficient, μm, was determined for each energy by fitting the data to Eq. 1, where Xxm is the exposure in air behind a thickness xm of the material, and X0 is the exposure in the absence of shielding. These results are compared with the ordinary concrete (2.35 g cm-3) for 6MV and 15MV energies (Ref. NCRP Report No.151). Results are tabulated in Table1. Results of attenuation are compared with ordinary concrete in Fig. 1. CONCLUSIONS The new concrete CONTEK®-RFH2 increases photon attenuation and reduces the size of a shielded wall. A very high percentage in iron and a suitablesieve size approximately double the density of ordinary concrete. High mass attenuation coefficient makes this concrete an extremely desirable material for use in radiation facilities as shielding material for photon beam, and for upgrading facilities designed for less energy or less workload.