M?ssbauer and Raman spectroscopy characterization of concretes used in the conditioning of spent radioactive sources

摘要

Spent radioactive sources are considered a type of radioactive waste which must be stored properly. These sources are usually conditioned in concrete that functions as shield and physical barrier to prevent the potential migration of radionuclides, and must have suitable properties: mechanical, thermal or irradiation resistance. Concretes used in the conditioning of spent radioactive source in Mexico were tested, preparing concrete test specimens with Portland cement CPC 30RS EXTRA CEMEX and aggregates, and subjected to compression strength, γ -ray-irradiation and thermal resistance assays and subsequently analyzed by M?ssbauer and Raman Spectroscopies as well as by Scanning Electron Microscopy, in order to correlate the radiation and temperature effects on the compressive strengths, the oxidation states of iron and the structural features of the concrete. Iron was found in the concrete in Fe~(2+) and Fe~(3+) in the tetrahedral (T) and two octahedral positions (O1, O2). Radiolysis of water causes the dehydratation (200-600 kGy) and rehydratation(1000-10000 kGy) of calcium silicate hydrates (C-S-H) and ferric hydrate phases in concretes and structural distortion around the iron sites in concretes. The compressive strength of concretes are not significantly affected by γ -radiation or heat.