Vitrification of Nuclear Wastes by Complex Sol-Gel Process

Abstract

For synthesis of silica glasses designed to contain high-level nuclear wastes，a patented complex sol-gel process has been used. Surrogates of the nuclear waste elements Cs, Sr, Co, and Nd (generically denoted Me) were used. Gels in the forms of powders and sintered compacts were prepared by hydrolysis and polycondensation of tetraethoxide/Me nitrate solutions, which contained ascorbic acid as a catalyst. Transformation to final products was studied by thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction. Preliminary testing of Me leaching was also completed in water. Most of the final products were porous; only a single dense form was resistant to leaching.

Optimization of Working Conditions for Perovskite-Based Gas Sensor Devices by Multiregression Analysis

“…e concentration of oxygen vacancies depends on both the oxygen partial pressure and the temperature, according to the principle of Le Chatelier. Indeed, oxygen vacancies formation is promoted under high temperature and low oxygen partial pressure according to endothermic reaction (1), while oxygen vacancies refilling is promoted under low temperature and high oxygen partial pressure in agreement with the exothermic reaction (2) [17,18]:…”

“…is scenario drives scientific research priorities to develop technologies for sustainable productive systems in order to increase the process efficiency. Among these, nuclear and fuel cell are promising green power technologies, but they have open challenges yet, such as the issues related to the nuclear waste management [1] and fuel cell reliability [2], respectively. For these reasons, the research is currently focused on developing facilitative technologies to control the conventional unsustainable technology in order to convert it to a sustainable one.…”

“…where O X O is oxygen with neutral charge sitting on the perovskite lattice site and V € O is oxygen vacancy with double positive charge, following the Kroger-Vink notation. At the same time, oxygen vacancies formation leads to an increase in free-electron concentration, while oxygen vacancies refilling leads to an increase in free electronichole concentration: in other words, reactions (1) and (2) act as self-doping processes, where oxygen vacancy is a donordopant and oxygen is an acceptor-dopant. In addition, the concentration of both electron and holes depends on the energy bandgap and temperature because high temperature promotes electrons from the valence band to the conduction band [19].…”

Combustion synthesis of LaFeO3 sensing nanomaterial

“…For addressing that issue, engineering research has been focusing on nuclear and fuel cell technologies [1][2][3][4][5][6]. However, since nuclear waste management [7,8] and fuel cell reliability [9][10][11][12][13][14] are unresolved challenges, these technologies appear to be unsustainable and unfeasible. Currently, the green economy strategy is developed for addressing all issues with proactive balanced approaches.…”

Low-temperature capacitive sensor based on perovskite oxides

“…However, challenges in nuclear waste management [1,2], hydrogen production and fuel cell reliability preclude the sustainability and the feasibility of these technologies [3][4][5][6][7][8][9][10][11][12][13][14]. For this reason, it is of great interest to improve the conventional combustion processes for developing sustainable energy converters.…”