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For timely and prompt detection of the inter-circuit depressurization of the steam generator of the “sodium-water” type in the 2nd circuit, continuous monitoring of the content of hydrogen, as a product of the interaction of sodium with water, is carried out in all operating modes. However, in reality, the main source of hydrogen in the sodium of the 2nd circuit is the process of electrochemical corrosion of 10X2M steam generator steel in a steam-water medium, the speed of which is never zero and is controlled at the minimum achievable level by means of the water-chemical regime of the 3rd circuit. At the same time, during the operation of the steam generator, deposits of corrosion products accumulate on the surface of the structural steel from the side of the 3rd circuit. The removal of deposits is carried out with the help of operational chemical flushes (ECPs). However, during the ECP, the corrosion rate of steel inevitably increases significantly (by about three orders of magnitude), which leads to an increase in the concentration of hydrogen in water and in sodium. This phenomenon has previously caused concern to the operational services of nuclear power plants due to the likely through-corrosion during regular ECP (every year, one of the three steam generators is washed). However, it is unacceptable to operate a steam generator without ECP, and to reduce the corrosion rate of steel of steam generator pipes in a steam-water environment, after ECP, a chemical passivation stage is carried out with different formulations, the effectiveness of which is different. This article presents a physical model of the mass transfer of corrosive hydrogen in a steam generator during chemical washing, passivation and start-up of the steam generator. An operational criterion for evaluating the effectiveness of passivation by the rate of increase in the concentration of hydrogen in the sodium of the second circuit during the subsequent start-up of BN-600 steam generators is proposed: if the rate of increase in the concentration of hydrogen in the 2nd circuit is less than 0.05 ppm/h, then passivation is effective, if more than the passivation formula requires revision. For BN-800 steam generators, the technology of passivation after ECP has not yet been determined, the article proposes a calculated criterion for its efficiency of 0.015 ppm/h.

Analysis of the dynamical regime changes in the stratosphere during different phases of the Sudden Stratospheric Warming (SSW) that has been observed in January 2013 is presented. The different mechanisms of SSW influence on the tropospheric circulation through the stationary planetary waves (SPWs) reflection and/or increase in SPWs activity due to nonlinear interaction with the mean flow and their subsequent propagation into the troposphere are discussed. Three-dimensional wave activity flux and its divergence are determined using the UK Met Office data; the synoptic situation and its changes during the SSW events are analyzed. The wave activity penetrates downward from stratosphere into the troposphere and can affect weather processes during the SSW and right afterwards. It is this time that polar anticyclones can be formed at high latitudes, which quickly go southward along meridional directions and then deviate to the East at middle latitudes. Interestingly, the locations of polar anticyclone formations and subsequent displacements correspond to the regions of maximal horizontal wave activity fluxes connected with stratospheric processes. The results obtained allow us to suggest that accounting of stratospheric processes and their influence on the troposphere in winter season can improve the middle-range forecast of anticyclone formation and cold weather events at middle latitudes.

Computational studies of experimentally validated method of solid-phase oxidation of alkali metals in application to the decommissioning of the BR-10 research reactor are presented. Computational-theoretical studies were performed for the method where alkali metals are mixed with oxidizers (granulated slag from copper smelting operations) by pumping alkali metal along a down pipe beneath a layer slag into the reaction chamber.

In this paper the influence of solar activity on variability of the springtime transition dates of stratospheric circulation is investigated. To detect the influence, the springtime transition and solar activity datasets were grouped according to the phases of the Quasi-Biennial Oscillation (QBO). It was obtained that there is a dependence of spring transition dates on solar activity. In case of dividing data on early and later spring transition, the stronger influence of solar signal is revealed at late spring transition. It was also shown that under high solar activity conditions, the relation between spring transition dates and solar activity is stronger than at low one.

NCEP/NCAR (National Center for Environmental Prediction – National Center for Atmospheric Research) data have been used to estimate the long-term variability of the mean flow, temperature, and Stationary Planetary Waves (SPW) in the troposphere and lower stratosphere. The results obtained show noticeable climatic variabilities in the intensity and position of the tropospheric jets that are caused by temperature changes in the lower atmosphere. As a result, we can expect that this variability of the mean flow will cause the changes in the SPW propagation conditions. The simulation of the SPW with zonal wave number m=1 (SPW1), performed with a linearized model using the mean flow distributions typical for the 1960s and for the beginning of 21st century, supports this assumption and shows that during the last 40 years the amplitude of the SPW1 in the stratosphere and mesosphere increased substantially. The analysis of the SPW amplitudes extracted from the geopotential height and zonal wind NCEP/NCAR data supports the results of simulation and shows that during the last years there exists an increase in the SPW1 activity in the lower stratosphere. These changes in the amplitudes are accompanied by increased interannual variability of the SPW1, as well. Analysis of the SPW2 activity shows that changes in its amplitude have a different sign in the northern winter hemisphere and at low latitudes in the southern summer hemisphere. The value of the SPW2 variability differs latitudinally and can be explained by nonlinear interference of the primary wave propagation from below and from secondary SPW2.

The northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The Arctic-boreal natural environments play a crucial role in the global climate via albedo change, carbon sources and sinks as well as atmospheric aerosol production from biogenic volatile organic compounds. Furthermore, it is expected that global trade activities, demographic movement, and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but also is able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX sets a research approach by which large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land-Atmosphere-Aquatic-society continuum in the northern Eurasian region. We introduce here the state of the art for the key topics in the PEEX research agenda and present the future prospects of the research, which we see relevant in this context.

The Northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The arctic-boreal natural environments play a crucial role in the global climate via the albedo change, carbon sources and sinks, as well as atmospheric aerosol production via biogenic volatile organic compounds. Furthermore, it is expected that the global trade activities, demographic movement and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but is also able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX is setting a research approach where large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land–atmosphere–aquatic–society continuum in the Northern Eurasian region. We introduce here the state of the art of the key topics in the PEEX research agenda and give the future prospects of the research which we see relevant in this context.