Застосування лужно-активованого цементу для імобілізації іоно-обмінних смол з низьким рівнем радіоактивності

All generated and collected low-level radioactive wastes (LRW) should be processed into final products for a long-term disposal without loss of their properties. Worldwide, cementation is the most widely used technology for immobilization of nuclear wastes. Due to many existing varieties of LRW some of these wastes are incompatible with the process of hydration and hardening of a cement matrix and require optimization of cement immobilization technologies. The paper presents the results of devising new formulations of multi-component alkali-activated cement, which is aimed at complex processing of low-level radioactive waste with ion-exchange resins. The radioactive wastes to be immobilized included two types of ion-exchange resins: cation- and anion-exchange resins mixed as 2:1 with pH=12 and anion-exchange resin with pH=5. Analysis of the obtained results from the developed optimal recipes proved that the properties of the final products are in compliance and in some cases even exceed those set in standards GB 7023 and GB 14569 of the P. R. China. High efficiency of the alkali-activated cement matrices for immobilization of radioactive wastes is attributed to their ability to bind radionuclides not only mechanically and adsorptionally, as it happens in case of traditional cement matrices, but also chemically–within the composition of zeolite-like hydration products of the R2O∙MeO∙Al2O3∙nSiO2mH2O or R2O∙Al2O3∙nSiO2mH2O types, where: R=Na, K, and Cs; Me=Ca, Mg, and Sr.Рассмотрены два типа радиоактивных ионообменных смол с низким уровнем активности: смесь катионной и анионной смол в пропорции 2:1 и анионно-обменная смола. Представлены результаты разработки компаундов в соответствии с требованиями стандартов КНР GB 7023 и GB 14569. Показана высокая эффективность использования шлакощелочных систем для иммобилизации радиоактивных отходов.Розглянуто два типи радіоактивних іоно-обмінних смол з низьким рівнем активності: суміш катіонної та аніонної смоли в пропорції 2:1 та аніонно-обнінну смолу.Наведено результати розробки компаундів відповідно до вимог стандартів КНР GB 7023 та GB 14569. Доведено високу ефективність використання шлаколужних систем для імобілізації рідоактивних відходів

Effect of acetylacetone on the preparation of PZT materials in sol-gel processing

Sol–gel processing is an advantageous route to produce PZT thin film materials with high quality. PZT powders and thin films with good properties were fabricated by sol–gel processing, using acetylacetone as modifier, in the study. The morphologies of PZT powders and thin films were observed by field emission microscopy, and the dielectric and properties of the PZT thin films were measured. Thermal analysis, XRD and FTIR were used to investigate the influence of ligands on the phase transformation in PZT materials, and it is found that the difficulty of decomposing acetylacetone ligands completely resulted in a higher pyrolysis temperature to form PZT with pure phase

Speciation and hydrolysis kinetics of aluminates

Abstract not available

Ефективність використання лужних гібридних цементів для імобілізації іоно-обмінних смол з низьким рівнем радіоактивності

Immobilization by cementation of anion­exchange resins is closely associated with high pH­values of a cement matrix as a result of compositional build­up of the cements used as binding agents. At high pH values the anion­exchange resins with acid reaction (pH<5) start recycling in a body of the hardening cement compound resulting in its destruction. The paper covers the results on efficiency of the hybrid alkali activated cements as binding agents which at the initial stage of hydration have high pH values of the cement stone (pH>12), thus providing a required strength gain. Later, pH values tend to lower (pH<10), thus retarding the process of resin recycling to the values which do not affect negatively durability of the resulted solidified waste forms. The examples of hybrid alkali activated cements compositional build up are provided together with physico­mechanical properties of the resulted solidified waste forms. These results show that these properties are superior to those specified in the standards of the P. R. China, these are: GB 7023 and GB 14569.Были разработаны составы матриц для утилизации анионно-обменных смол с низким уровнем радиоактивности, которые образуются как следствие работы атомных реакторов, с использованием гибридных щелочных цементов. Показаны результаты исследований эксплуатационных свойств конечного продукта (прочности, радиационной стойкости и пр.) и доказано, что по своим физико-механическим и физическим характеристикам разработанные составы соответствуют требованиям стандартов КНР GB 7023 и GB 14569Було розроблено склади матриць для утилізації аніонно-обмінних смол з низьким рівнем радіоактивності, що утворюються внаслідок роботи атомних реакторів, з використанням гібридних лужних цементів. Показано результати дослідження експлуатаційних властивостей кінцевого продукту (міцності, вилуговування, радіаційної стійкості, тощо) та доведено, що за своїми фізико-механічними та фізичними властивостями розроблені склади відповідають вимогам стандартів КНР GB 7023 та GB 1456

Effects of aluminates on the formation of geopolymers

The mechanisms of Al speciation and hydrolysis in geopolymer systems are investigated based on the partial charge model together with preliminary experimental validation. Calculation of the partial charges of species discloses that the positive partial charge of the Al atom is always higher than that of Si atom under conditions of similar pH values, suggesting greater tendency of [Al(OH)4]- tetrahedra to attract negatively charged groups from other species. Given Al atom with four hydroxyl groups under alkaline conditions and the potential to expand its coordination number with greater ease, condensation reactions involving aluminate species appear to occur much more readily. Thus, the model essentially predicts that aluminate species promote condensations reaction owing to factors such as their partial charge and the number of hydroxyl groups, implying that the solubility of aluminate sources (i.e. metakaolin) and the distribution of [Al(OH)4] - ions have an important influence on the mechanical properties of inorganic polymers. Corresponding experimental data on aluminate dissolution obtained from progressive milling of metakaolin particles demonstrated that varying particle sizes and different degrees of aggregation of metakaolin can have an important influence on inorganic polymer properties such as setting time, microstructure and compressive strength. The results indicate that milled metakaolin powders with high specific surface area have faster setting characteristics, higher compressive strength, and possess a more homogeneous microstructure, attributable to Al availability as predicted by the partial charge model

Preparation of tricalcium phosphate/alumina composite nanoparticles and self-reinforcing composites by simultaneous precipitation

Preparation of tricalcium phosphate/alumina composite nanoparticles and self-reinforcing composites by simultaneous precipitatio

Effect of acetylacetone on the preparation of PZT materials in sol-gel processing

Sol-gel processing is an advantageous route to produce PZT thin film materials with high quality. PZT powders and thin films with good properties were fabricated by sol /gel processing, using acetylacetone as modifier, in the study. The morphologies of PZT powders and thin films were observed by field emission microscopy, and the dielectric and properties of the PZT thin films were measured. Thermal analysis, XRD and FTIR were used to investigate the influence of ligands on the phase transformation in PZT materials, and it is found that the difficulty of decomposing acetylacetone ligands completely resulted in a higher pyrolysis temperature to form PZT with pure phase