Нормы безопасности Международного агентства по атомной энергии (МАГАТЭ) содержат принципы, требования и рекомендации по обеспечению безопасности и являются согласованным и общепринятым ориентиром эффективного выполнения международных обязательств стран, использующих атомную энергию в мирных целях. Действующие нормы Агентства применимы, как правило, к наземным стационарным атомным электростанциям с водоохлаждаемыми реакторами мощностью от 600 до 1 500 МВт. Для других типов реакторов, включая инновационные разработки, в том числе атомные станции малой мощности, некоторые положения по безопасности могут оказаться неприменимыми или же применимыми с определенными изменениями. В статье представлены основные результаты анализа применимости стандартов МАГАТЭ к проекту реакторной установки РИТМ-200Н для наземных атомных станций малой мощности. The International Atomic Energy Agency (IAEA) safety standards contain safety principles, requirements and recommendations and are a consistent and generally accepted guideline for the effective fulfilment of international obligations of countries that use nuclear energy for peaceful purposes. The current Agency standards are generally applicable to land-based stationary nuclear power plants with water-cooled reactors with a capacity ranging from 600 to 1 500 mW. For other types of reactors, including innovative designs such as small nuclear power plants, some safety provisions may not be applicable or may be applicable with certain modifications. The paper provides the main results of the analysis of the applicability of the IAEA standards to the design of the RITM-200N reactor plant for land-based small nuclear power plants.

The history of the development and adoption of reliability analysis of equipment and systems as well as probabilistic safety analysis in the practice of design and operation of nuclear installations is presented. The basic characteristics of the developed software systems for performing probabilistic safety analysis of installations during the design process, risk monitoring during operation of NPP, reliability monitoring of ship installations, and nuclear power plants operating as intended as well as information about their adoption in operating facilities are presented. It is shown that digital technologies are being actively adopted in the analysis and monitoring of safety.

The OKBM Afrikantov infrastructure created for performing probabilistic safety analysis of nuclear installations used for different purposes is briefly described. The research in which the enterprise participated is presented. Included are the Voronezh nuclear plant with an AST-500 reactor for supplying heat, commercial uranium-graphite reactors ADE-2, -4, -5, a reactor installation with a high-temperature gas-cooled reactor GT-MGR [gas turbine, modular helium reactor], and reactor installations for nuclear-powered icebreakers. Except for a nuclear installation, a probabilistic safety analysis was performed for a water-cooled storage facility for spent nuclear fuel at the Mining and Chemical Combine. The results of a probabilistic safety analysis for the floating power-generating unit Akademik Lomonosov as well as for the fast sodium-cooled reactors BN-600 and -800 are examined. It is noted that such an analysis is an effective tool for developing measures to improve the safety of nuclear reactor installations of different types and classes.

Testing and experimental substantiation are a significant and integral part at all phases of the life cycle of reactor equipment. The Research and Testing Complex (RTC) operates at OKBM Afrikantov to ensure that these tasks are successfully fulfilled. The RTC provides the opportunity of performing a wide range of research and testing during the creation of reactor installations as well as the development of the main and auxiliary equipment for the nuclear energy industry. The most significant work performed on the experimental base at OKBM in the last 15–20 years reduces to neutronics and thermotechnical studies of cores and FA, testing equipment for naval and civilian ship reactor installations and NPP, experimental substantiation of systems and study of processes occurring in them and the elements of the equipment in nuclear installations, and the study of the corrosion and strength properties of materials. Work on modernization of currently operating and creation of new test stands is ongoing at the RTC.

The effect of severe plastic deformation by rotary forging on the mechanical properties and the corrosion resistance of a pseudo-α-titanium PT-7M alloy is studied. The corrosive character of fracture the fine-grained alloy under hot salt corrosion (HSC) conditions is found to change: pitting corrosion at the onset of recrystallization processes changes into intercrystalline corrosion. The HSC resistance of the fine-grained PT-7M titanium alloy is shown to depend on the structure–phase state of grain boundaries, whose intense migration with developing recrystallization leads to “sweeping out” of corrosion-hazardous alloying elements (aluminum, zirconium) from the crystal lattice of the titanium alloy.

The corrosion–fatigue fracture of an ultrafine-grained Ti–2.2Al–2.5Zr pseudo-α titanium alloy (PT-7M alloy), which is used in atomic power engineering, is studied. The formation of an ultrafine-grained structure by rotary forging is found to increase the corrosion–fatigue strength. The parameters in Basquin’s equation are determined, and the slope of the σa–log N fatigue curve is shown to nonmonotonically depend on the temperature of annealing of the ultrafine-grained alloy.

The basic results of computational and experimental studies of passive systems of emergency heat removal in application to ship and portable reactor facilities are presented. The methodological correlations for calculations of heat removal systems with condensation of steam in a bundle of inclined tubes under mixed convection conditions in the presence of non-condensing gases and the true volume steam content in a vertical large-diameter tube are developed. The optimization of the cooling loops of systems performing emergency heat removal at pressure close to atmospheric and suggestions for improving a passive system of emergency heat removal from a reactor are discussed.

Severe accidents in NPP with VVER can be accompanied by hydrogen entering the containment space. The aim of the present work is an experimental and computational study of the possibility of hydrogen stratification in the containment in a scenario replicating the sequence of events occurring during a severe accident with hydrogen emission in a light-water reactor taking account of the impact of accident control on the distribution of a light gas. Euratom and the government corporation Rosatom performed the studies as part of two parallel projects – ERCOSAM and SAMARA. The experimental studies show that heat exchangers aand recombiners do bring about complete mixing of the light gas; a sprinkler system affords mixing of the stratified layer. The experimental studies confirm the results of numerical modeling.

A high-efficiency once-through steam generator is used in the RITM-200 reactor for the universal nuclear icebreaker. The new design necessitated experimental validation of the technical characteristics of the steam generator taking into account the integral arrangement of the steam-generating block. To this end a model of the steam-generator cassette was developed and tested at OKBM Afrikantov. The experimental studies of the model of the steam-generator cassette confirmed the heat-engineering and hydrodynamic design characteristics of the steam generator in the RITM-200 reactor.

Проведены исследования влияния интенсивного пластического деформирования (ИПД) на структурно-фазовое состояние границ зерен псевдо-alpha-титанового сплава Ti-4Al-2V (промышленное обозначение ПТ3В). Установлено, что повышение прочности, пластичности и коррозионной стойкости титанового сплава связано с формированием ультрамелкозернистой структуры. Показано, что повышение коррозионной стойкости в условиях горячей солевой коррозии обусловлено диффузионно-контролируемым перераспределением атомов алюминия и ванадия на границах зерен титана, сформированных в процессе теплой ИПД. DOI: 10.21883/PJTF.2017.10.44617.16580

The influence of the structural-phase state of grain boundaries in a Ti4Al2V (commercial PT3V grade) pseudo-alpha-titanium alloy on its susceptibility to hot-salt intergranular corrosion (IGC) has been studied. It is established that IGC-tested alloy samples exhibit corrosion-induced defects of two types. More extended defects of the first type occur at the V-rich boundaries of coarse grains, while short defects of the second type reside at the grain boundaries with composition close to that of the grain body. The existence of the two types of IGC defects is explained by the classical theory of galvanic microcouples (microcells), according to which the IGC intensity is proportional to the difference of corrosion-active impurity concentrations between the grain boundary and body.

The influence of severe plastic deformation on the structural-phase state of grain boundaries in a Ti–4Al–2V (commercial PT3V grade) pseudo-alpha-titanium alloy has been studied. It is established that increase in the strength, plasticity, and corrosion resistance of this alloy is related to the formation of an ultrafine- grained structure. In particular, it is shown that an increase in the resistance to hot-salt intergranular corrosion is due to diffusion-controlled redistribution of aluminum and vanadium atoms at the grain boundaries of titanium formed during thermal severe plastic deformation.

Проведены исследования влияния структурно-фазового состояния границ зерен псевдо-alpha-титанового сплава Ti-4Al-2V (промышленное обозначение ПТ3В) на склонность к горячей солевой межкристаллитной коррозии (МКК). Показано, что после испытаний на МКК в сплаве наблюдаются два типа коррозионных дефектов. Более протяженные дефекты МКК первого типа располагаются по границам крупных зерен, обогащенных ванадием, а короткие дефекты второго типа --- по границам зерен, имеющих химический состав, мало отличающийся от состава тела зерна. Наличие двух типов дефектов МКК объясняется классической теорией возникновения микрогальванических пар, в соответствии с которой интенсивность МКК пропорциональна разности концентраций коррозионно-опасных примесей между границей и телом зерна.

The article presents the results of experimental investigation of the physical and mechanical properties and corrosion resistance of submicrocrystalline titanium alloy PT3V (Ti-Al-V system industrial alloy). The titanium alloy structure control using the ECAP technique is shown to improve the SMC alloy thermal stability together with its strength, plasticity, hot salt corrosion and corrosion fatigue resistances. A qualitative explanation of observed patterns is proposed.

Equipping new-generation nuclear power plants with passive means for controlling unanticipated accidents is one of the most promising directions for increasing safety, which is being implemented in the AES-2006 design for the site of the Leningradskaya nuclear power plant. An urgent problem is to obtain experimental validation of the passive system for removing heat from the protective envelope during unanticipated accidents with loss of coolant from the first loop in the case where the active systems fail. A particularity of the system is its state of constant readiness. The system functions with natural circulation of the coolant in both loops. Considering the importance of the passive heat removal system for ensuring the localizing properties of the protective envelope, OKBM Afrikantov has developed a large-scale stand and performed experimental investigations on validation of the effectiveness and serviceability of the cooling loop of a passive system for removing heat from the protective envelope.

The concept of risk is now no longer of academic interest only, since it is widely used in legislative acts. In the present paper risk is defined mathematically as a measure of the possible danger of an object (phenomenon) that can be expressed as a distribution function of a multidimensional random quantity characterizing the different types of possible harm due to the object (phenomenon under study). Some numerical characteristics or parameters of risk are examined. It is shown that using the average value of the consequences of accidents at objects as a risk parameter is of limited application. Various directions of the application of risk to the safety of nuclear power plants are analyzed. The most important application of the methodology of risk analysis is a systems investigation of the "weak links" in safety measures with the generation of recommendations for preventing and limiting the consequences of accidents.