Self-propagating high-temperature synthesis of the high- current emission lanthanum and niobium contained ceramics

The paper describes the production of metal-ceramic high-current emitters containing lanthanum hexaboride LaB[6] by self-propagating high-temperature synthesis. Tests of emitters as explosive-emission cathodes in an OMEGA-350 microsecond accelerator are presented. Experiments show that when a metal-ceramic cathode is used, the emitted energy was 12-17% higher than that produced by tungsten and graphite cathodes and the beam "signature" is a circle with a small (~ 15%) variation in radius

Structural Modification of La[2]O[3]-TiO[2]-B Mixture After Mechanical Activation

Accelerators require development of new and more powerful installations, generating the streams of the charged particles, affecting the development of machine building industry, energy power industry and other fields of science and technology. Great attention is paid not only to the modernization of the installations, in whole, but also to their individual elements. Cathode is the most important element of the installations, generating the stream of charged particles. Using lanthanum hexaboride as a cathode material allows getting maximum efficiency of cathode assembly due to the thermodynamic and emission properties of lanthanum hexaboride. This paper studies the properties changes of lanthanum oxide mixture, titanium and boron oxides under the influence of mechanical activation to obtain the final product, based on lanthanum hexaboride and titanium diboride, corresponding to the high performance properties of the emitter. The study resulted in determination of time and frequency of mechanical activation to obtain the particles with the smallest average size of 6.3 microns for the mixture of lanthanum oxide, titanium and boron oxides powders

Mechanical activation influence on the morphological properties of La[2]O[3]-TiO[2]-B

The influence of mechanical activation of the powder mixture used to obtain the high-perfomance cathode for accelerating engineering with the SHS-method has been explored. The mechanically processed mixtures have been morphologically analyzed. The optimal modes of mechanical activation have been determined for the mixture

Synthesis and properties of the materials obtained by SHS mode for radiation protection

The article shows the process of protective composite materials manufacturing. Also, the analysis of experimental results concerning the composite materials protective properties is given. The advantages of SHS method are considered in comparison with traditional materials. The uniqueness of SHS obtained products based on combination of nuclear-physical properties and parameters is presented

Effect of the Compaction Pressure and Ni Content on the Modified Aluminum-Based Perovskite Synthesis Designed to Immobilize the Radioactive Waste in Combustion Mode

The article deals with the synthesis of perovskite-like ceramics matrix material for immobilization of radioactive waste by SHS method. The dependence of the compaction pressure on the synthesis of the samples was established. Synthesis conditions for the matrix with the desired properties of the composition were determined that is acceptable for reliable isolation of radionuclides throughout the long-term storage of waste. The maximum amount of aluminum perovskite is observed when the initial mixture compaction pressure equal to 30 MPa and 25% wt. Nickel

Mathematical modeling of combustion wave propagating in SH-synthesis of functional borides used to protect from mixed ionizing radiation

This work describes the mathematical model of SHS combustion wave propagating in the system of W-B. The model is based on the heat equation. The result of modelling is a forecast of SH-synthesis temperature regime in this system what allows forecasting a phase composition and thermal stresses. The model checking was realized in the experiment in the synthesis of this system in a laboratory-scale plant including the SHS reactor. The presented model is in agreement with the experiment in a maximum synthesis temperature and the curve rate of synthesis carrying out

Mathematical modeling of combustion wave propagating in SH-synthesis of functional borides used to protect from mixed ionizing radiation

This work describes the mathematical model of SHS combustion wave propagating in the system of W-B. The model is based on the heat equation. The result of modelling is a forecast of SH-synthesis temperature regime in this system what allows forecasting a phase composition and thermal stresses. The model checking was realized in the experiment in the synthesis of this system in a laboratory-scale plant including the SHS reactor. The presented model is in agreement with the experiment in a maximum synthesis temperature and the curve rate of synthesis carrying out

Evaluation of neutron activation of intermetallic matrices for dispersive nuclear fuel obtained by SH-synthesis

The paper describes a technique for obtaining intermetallic matrix materials based on Zr-Al and Ni-Al systems for dispersive nuclear fuel. This type of fuel is planned to be used in existing and future high-temperature nuclear reactors. Physical and mathematical modelling of the process of activation of matrices by neutron radiation showed that upon reaching the value of thermal neutron fluence of the order of 2.76·1021 n·cm-2 , the activity of Zr-Al and Ni-Al matrices was 1.3·1010 and 0.2·1010 Bq/g, respectively. The analysis showed that in terms of exposure of irradiated fuel it is preferable to use a matrix based on the zirconium-aluminium system

Development of matrix material based on aluminate perovskite for immobilization of actinides by self-propagating high-temperature synthesis

Актуальность исследования обусловлена необходимостью разработки способа получения перспективных минералоподобных матричных материалов, предназначенных для иммобилизации наиболее опасных с точки зрения захоронения высокорадиоактивных отходов атомной промышленности. Применение технологии самораспространяющегося высокотемпературного синтеза для получения таких материалов является более ресурсосберегающим и не требует сложного технологического оборудования и проведения комплексных операций по сравнению с традиционными способами получения. Цель: определить и предложить способ получения алюмината неодима в качестве матричного материала актиноидной фракции радиоактивных отходов. Объекты: алюминат неодима NdAlO3 со структурой минерала перовскит; неодим, являющийся имитатором трёхвалентной фракции радиоактивных отходов. Методы: оценка и анализ получения матричного материала путем компьютерного моделирования процесса самораспространяющегося высокотемпературного синтеза; проведение лабораторных экспериментов по синтезу алюмината неодима; определение фазового состава разрабатываемого материала методом рентгенофазового анализа. Результаты. Описана расчетно-теоретическая модель определения принципиальной возможности процесса самораспространяющегося высокотемпературного синтеза матричного материала на основе алюмината неодима, предназначенного для иммобилизации высокоактивных радиоактивных отходов. Методы численного моделирования позволили рассмотреть различные реакции синтеза такого материала и определить максимально возможное количество включения имитатора трехвалентных актиноидов. Так, для получения NdAlO3 необходимо использовать СВС-реакцию образования алюминий-никеля с дополнительным включением не более 46 мас. % системы Nd2O3-Al2O3 (соотношение компонентов оксидов 3,3:1) в исходную шихту смеси. Базируясь на результатах разработанной модели, было проведено экспериментальное исследование по синтезу матричного материала. Определены оптимальные условия подготовки шихты компонентов: плотность исходной системы не должна превышать 5,29 г/см3, что соответствует давлению прессования 40 МПа; максимально возможное включение Nd2O3-Al2O3 в систему Ni-Al - не более 40 мас. %. Проведенный рентгенофазовый анализ показал наличие фазы алюмината неодима во всех синтезируемых образцах, максимальная доля NdAlO3 достигается при синтезе образца с 40 мас. % добавки Nd2O3-Al2O3 и давлением прессования 30 МПа. Таким образом, использование ресурсоэффективной и простой технологии самораспространяющегося высокотемпературного синтеза позволяет получить надежный матричный материал для иммобилизации радиоактивных отходов.The relevance of the research is determined by the need to develop the method for obtaining mineral-like matrix materials intended for immobilization of the most hazardous radioactive waste of the nuclear industry. The use of the self-propagating high-temperature synthesis technology to obtain such materials is more resource-saving and does not require complex technological equipment and operations compared to traditional ways of production. The main aim of the research is to define and propose a method for producing neodymium aluminate as a matrix material for the actinide fraction of radioactive waste. Objects of the research are neodymium aluminate NdAlO3 with the structure of the mineral perovskite, which is used as an imitator of the trivalent fraction of radioactive waste. Methods: evaluation and analysis of the matrix material creation by computer modeling of the self-propagating high-temperature synthesis; laboratory experiments on the synthesis of neodymium aluminate; determination of the morphological composition of the material by XDR phase analysis Results. The paper describes a theoretical and simulation model for determining the fundamental possibility of the self-propagating hightemperature synthesis of a matrix material based on neodymium aluminate, intended for immobilization of high-level radioactive waste. Numerical simulation methods allowed us to consider various synthesis reactions of such material and determine the maximum possible amount of inclusion of a trivalent actinide simulator. Thus, it is necessary to use the reaction of SH-synthesis of aluminum-nickel with an additional content of no more than 46 wt. % of Nd2O3-Al2O3 (oxide component ratio of 3,3:1) system in the initial mixture to obtain NdAlO3. The experimental study was carried out on the synthesis of the matrix material based on the results of the developed model. The authors have determined the optimal conditions for preparation of the components batch: the initial system density should not exceed 5,29 g/cm3 which corresponds to pressure of 40 MPa; the maximum possible inclusion of Nd2O3-Al2O3 into Ni-Al system is not more than 40 wt. %. The performed XRD analysis showed the presence of a neodymium aluminate phase in all synthesized samples; the maximum proportion of NdAlO3 is achieved during the synthesis of a sample with 40 wt. % of Nd2O3-Al2O3 additive and pressure of 30 MPa. Thus, the use of a resource-efficient and simple technology of self-propagating high-temperature synthesis makes it possible to obtain a reliable matrix material for radioactive waste immobilization