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Information × Registration Number 0217U003333, 0113U002171 , R & D reports Title Research of physical-chemical principal for "Shelter" object fuel-contaiming materials degradation process when its controlled custody and conversion popup.stage_title Head Gabelkov Sergey Vladimirovich, Доктор фізико-математичних наук Registration Date 30-03-2017 Organization Institute for Safety Problems of Nuclear Power Plants popup.description2 Objects of researches - lava-like fuel-containing materials of "Shelter" object; their physical and chemical properties, processes, which pass and/or passed in lava-like fuel-containing materials, aerosol. An aim of work authentication and study of basic physical and chemical processes in fuel-containing materials of "Shelter" object, determination of their interconnection and degree of cross-coupling, improvement of evolution model of lava-like fuel-containing materials (LFCM) for prognostication of degradation of their structure and basic physical-chemical properties. Methods of researches methodology of measuring of microhardness; methodology of determination of durability at an axleloading, methodology of determination of volumes of pore channels for extraction of working liquid from them at evaporation, method of ceramographics for research of microstructure, method of the hydrostatical weighing for determination of imaginary closeness, method of aquatic picnometrics for determination of picnometric closeness. Results and their novelty - pore space of "Shelter" LFCM object is investigated. The new constituent of LFCM pore space is revealed - nano-scale pore channels with diameter less than 40 - 60 nm, which are the result of ?-particles tracks association, that appeared at radionuclides ?-decay. Nanochannels were connected with each other and with an external environment by gas pores. The model of degradation of microstructure and physical-chemical properties of LFCM is created. Physical-chemical processes which determine the LFCM microstructure evolution are distinguished. The stages of degradation and their duration are determined: forming of open porosity due to formation of framework of open pore nanoscale channels (10 - 12 years); oxidization of uranium oxides at inclusions due to penetration of air (6 - 12 years); forming of cracks (a few years); interaction of uranium oxides with water (from a few years to decades). It is shown that in nearest 5 - 10 years degradation of brown and black LFCM ceramics will be slowed substantially. LFCM self-irradiation will not result in considerable increase of amount of nano-scale pore channels. The process of oxidization of uranium oxides completed in inclusions. Forming of new cracks and/or development of already existing stopped practically. Penetration of water in LFCM through cracks to uranium oxides inclusions will be slowed substantially. Formation of hydrates and soluble connections of uranium and transuraniums also will be slowed considerably. At a receipt and further treatment LFCM will collapse on particles with the middle sizes of 100 - 200 micrometers, which are pricked out from LFCM by a few cracks, and small clusters of particles of uranium oxides with sizes 5 - 15 micrometers, which can easily collapse to nano-scale (5 - 50 нм) particles. These particles will form aerosols which are of large danger for a men. The process of crystallization of glass-matrix can become basic in 10 - 15 years. Crystallization of 20 - 40 % glass-phase will result in destruction of LFCM to the particles with the sizes of 20 - 100 micrometers and to the exit from LFCM of practically all present uranium oxides includings and increase in ten times (to 50 t) amount of nano-scale and submicrones powders of uranium oxides in "Shelter" object. The results of researching work do not have analogues in world practice. Destruction of LFCM surface in apartment 304/3 arose up, probably, in the places of the UO2 increased concentration. For tearing away of dust with the certain activity from the dry surface of LFCM it needs approximately in 7 times less than for tearing away from a water-treated surface. High speed of formation and collection of radioactive dust corresponds to a period directly after drying out of lava. Total activity of settled dust and, in approaching of full consideration, lifted from LFCM, for a 823 days (from them a 413 days are water-treated state) is 495,5 Бк - it is 2,15 кБк/м2 per year or 0,59?10-3 Бк/of см2 per day. The tendency of daily-average increasing of dust alpha-activity on more than 3% per year is revealed/ Relative concentration of particles with the aerodynamic diameter less then 0,8 micrometers in alpha-active dust which settled on filters grew with the increase of accumulation time of dust. Formation and further crushing of alpha-active dust require for explanation bringing in at least two independent mechanisms of dispergating. The following mechanisms proposed: destruction of matrix due to deformation at volume uranium expansion at further-oxidation in incorporated particles of UO2; and division of phases on split surface created, that formated at fragments destruction. The basic practical conclusion of work is that releasing LFCM capillary structure from water after their drying out at conditions of new confinement can result to substantial intensification of process of UO2 further-oxidation in lava and, as a result, to considerable increase of alpha-active dust amount. Application spheres an increase of nuclear, radiation and ecological safety of ChNPP' 4th block, treatment with lava-like fuel-containing materials. Product Description popup.authors popup.nrat_date 2020-04-02 Close