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Vitrification is the most effective method for the immobilization of hazardous waste by incorporating toxic elements into a glass structure. Iron phosphate glasses are presently being considered as matrices for the storage of radioactive waste, even of those which cannot be vitrified using conventional borosilicate waste glass. In this study, a structural model of 60P2O5-40Fe2O3 glass is proposed. The model is based on the crystal structure of FePO4 which is composed of [FeO4][PO4] tetrahedral rings. The rings are optimized using the DFT method and the obtained theoretical FTIR and Raman spectra are being compared with their experimental counterparts. Moreover, the proposed model is in very good agreement with X-ray absorption fine structure spectroscopy (XANES/EXAFS) and Mössbauer spectroscopy measurements. According to the calculations the Fe(3+) is in tetrahedral and five-fold coordination. The maximal predicted load of waste constituents into the glass without rebuilding of the structure is 30 mol%. Below this content, waste constituents balance the charge of [FeO4](-) tetrahedra which leads to their strong bonding to the glass resulting in an increase of the chemical durability, transformation and melting temperatures and density.

Vitrification is the most effective method of the hazardous waste immobilization. Toxic elements are incorporated into glass structure. Iron phosphate glasses are presently being considered as a matrix for storage of the radioactive waste which cannot be vitrified using a conventional borosilicate glass. Influence of Na 2 SO 4 as one of the components such the waste on thermal properties and crystallization ability of iron phosphate waste glass was studied. It was observed that Na 2 SO 4 decreases transformation temperature and increases DC p . The glass characteristic temperatures, glass crystallization ability, and crystallizing phases were determined. Na 2 SO 4 increases the glass crystallization ability which could be related with DC p heat capacity accompanying glass transition changes. The glass internal structure rebuilding, accompanying the sodium content increase, is considered. It is shown that DC p is a suitable, structure-sensitive glass crystallization ability, parameter.

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Vitrification is currently considered to be an effective method for immobilization of radioactive waste. It is based on the enclosing of harmful elements in the structure of the glass. This work presents the results of studies on the thermal properties of glasses from P 2 O 5 -Al 2 O 3 -Na 2 O and P 2 O 5 -Al 2 O 3 -Fe 2 O 3 -Na 2 O systems for rendering nuclear waste in the form of salts such as sulfates, halides, and phosphates with high sodium content. These substances are not accepted by borosilicate glass, commonly used up to now for nuclear waste immobilization. Formation of sinters of glass-waste mixtures was selected as the method for immobilization, and the thermal chemistry of this process was studied. CaCl 2 was used as the model chloride waste substance. The process of immobilization consists of its sintering with Na, Al, Fephosphate glasses containing more than 50 wt% P 2 O 5 as the amorphous matrix. Thermal analysis showed that all glasses exhibit an ability for crystallization, with that the intensiveness of this process is determined by the chemical composition of these glasses. The addition of Fe 2 O 3 to the glass intensified crystallization process. Leaching of components of sinters tests established that glass containing Fe 2 O 3 in its composition most effectively binds waste in comparison to Al 2 O 3 containing phosphate glass. The test results allow for the statement that the waste substance in the form of chloride salts such as CaCl 2 is stable bound in the glass-crystalline sinters, which ensures its effective immobilization.