| The radioactive wastes disposal and disposition is always one subject for nuclear science, due to a potential secular hazards radioactivity. For safety reasons, most of radioactive wastes require solidification into waste forms for final disposition. As crystalline waste forms, it offers inherently low leach rate, negligible thermal expansion, and ability to immobilize high concentration of waste in high density phases. Therefore, the synroc solidification is considered to be an optimal method to immobilized radioactive waste. In recent decades, a lot of manpower and material resources have been spent to immobilize radwaste in synroc. However, investigations mainly emphasized the ability of the host phase to accommodate nuclides immobilized and resist irradiation damage, etc. Few works were performed to reveal the influence of daughter on the structure and stability of solidified body. In the process of decay, parent nuclide is not only release energetic particles, but also generate new daughters. Generally, the oxidation state and radius are different between the radioisotope parent and daughters, which may greatly change structure, chemical stability and high radiation resistance of solidified body. To evaluate the long-term stability of radwaste forms, it is not only regard irradiation effect, but also decay product, especially, the combined action of daughters and energetic particles for the immobilization of radionuclides resulting from their decay.In this paper, the isotopes of 90Sr and 90Y were employed to research the parent and daughter for 90Sr decay, and incorporated into artificial rock matrix during synroc preparation. An external electron irradiation was used to simulate beta irradiation of strontium, and immersion test to simulate underground water. And that discussed the effect of electron irradiation, and combined effects of electron irradiation and simulative 89Y daughter on properties of 90SrTiO3 ceramic. The impact of 90Zr daughter on 9OSrTiO3 structure was also discussed based on the density functional theory, revealing the changes of 90SrTiO3 ceramic like phase composition, structure transformation and stability change, etc. Finally, we provide the chemical evolution and stable daughter phases of 90SrTiO3.(1) The SrTi1-xZrxO3 synroc were synthesized from powders that were generated in the sol-spray pyrolysis. It was found that the sintered pellets reveal rather dense micro structures and pure phases at 1250℃. Although, the mechanical property of solidified body was improve by the substitute Zr4+for Ti4+, due to the increased bond strength of Zr-O bond in this system, the structural transition from higher symmetry to lower symmetry was observed when the x value increases, and durability properties was not improved.(2) The Sr1-xYxTiO3 synroc were synthesized using Y2O3, SrTiO3 and Ti2O3 as raw material in an arc furnace in argon atmosphere with repetitive turnings. The effect of 89Y daughter on SrTiO3 structure and physicochemical property was researched, due to the difference in radius and oxidation between 88Sr and 89Y. The results indicated that it is very important to obtain Sr1-xYxTiO3 with high phase purity by mixing Ti4+ together with Ti3+, and keeping Ti3+ constant. The substitute Y3+ for Sr2+ greatly improves the mechanical properties in the solid solution, but was not chemical durability.(3) To reveal the effects 90Sr decay on structure, physical properties and chemical durability of SrTiO3 ceramic, the SrTiO3 and Sr0.9Y0.1TiO3 ceramics were irradiated by electron irradiation. These results indicated that the SrTiO3 ceramic exhibits excellent resistance under the coaction of both electron radiation and 89Y, and retain the stable structure. And that an acceptable structure model was provided only when considered 90Sr and 90Y, due to 90Y decay 90Zr with a half-life of 64 h.(4) The dopant formation energies, unit cell volume, bond distance and angle of Sr1-xZrxTiO3 with different Zr compositions are calculated based on density functional theory. The results indicated that the substitute Zr4+ for Sr2+ leads to a decrease in unit cell volume, bond distance and angle in the perovskite structure, while formation energies show an increase, suggested this system is more unstable. However, the local environment of coordination atom will be change due to the difference in oxidation state and radius between the Zr4+ and Sr2+, which can form stable orthorhombic phase by relaxing structure, and further confirmed that the daughter are a key factor influencing the stability of SrTiO3 ceramic.
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