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Bogdanov R.V.,Saint Petersburg State University | Kuznetsov R.A.,Saint Petersburg State University | Epimahov V.N.,Alexandrov Research Institute of Technology NITI | Titov A.V.,Saint Petersburg State University | Prudnikov E.E.,Saint Petersburg State University
Recent Patents on Engineering | Year: 2013

The paper presents new polyphase ceramic waste forms (matrices) of aluminosilicate-phosphate type synthesized from natural bauxites and apatite ore tailings. This ceramic material is named "geoceramics" by the authors. The optimum composition of the waste matrix is selected (Cs2O, P2O5, SiO2, and Al2O3) and a cost-saving method for synthesis of matrices capable to accommodate up to 12 wt. % of cesium and 6 wt. % of strontium isotopes is developed. Phases which immobilize cesium isotopes are identified. It is shown that waste forms which are close in stoichiometric composition to pollucite (CsAlSi2O6) have the best resistance to water. The rate of cesium leaching (R) from these waste forms is 2·10-6 g/cm2day in the kinetic region. Heat treatment and cooling of the matrix material does not affect the immobilization performance of the proposed waste forms. In some cases, a positive effect is achieved by using the sol-gel method which can reduce the grain sizes, resulting in a decrease in the leach rate of cesium to 1·10-6 g/cm2day. The leach rate of strontium is below the detection limit of atomic absorption spectrophotometers (0.3 · 10-6 g/cm2day). © 2013 Bentham Science Publishers. Source


Bottomley D.,Itu Institute For Transurane | Stuckert J.,KIT Campus Nord | Hofmann P.,KIT Campus Nord | Tocheny L.,ISTC Krasnoproletarskaya 32 34 | And 21 more authors.
Nuclear Engineering and Design | Year: 2012

The International Science and Technology Center (ISTC) was set up in Moscow to support non-proliferation of sensitive knowledge and technologies in biological, chemical and nuclear domains by engaging scientists in peaceful research programmes with a broad international cooperation. The paper has two following objectives: • to describe the organization of complex, international, experimental and analytical research of material processes under extreme conditions similar to those of severe accidents in nuclear reactors and, • to inform briefly about some results of these studies. The main forms of ISTC activity are Research Projects and Supporting Programs. In the Research Projects informal contact expert groups (CEGs) were set up by ISTC to improve coordination between adjacent projects and to encourage international collaboration. The European Commission was the first to use this. The CEG members - experts from the national institutes and industry - evaluated and managed the projects' scientific results from initial stage of proposal formulation until the final reporting. They were often involved directly in the project's details by joining the Steering Committees of the project. The Contact Expert Group for Severe Accidents and Management (CEG-SAM) is one of these groups, five project groups from this area from the total of 30 funded projects during 10 years of activity are detailed to demonstrate this: (1) QUENCH-VVER from RIAR, Dimitrovgrad and IBRAE, Moscow, and PARAMETER projects (SF1-SF4) from LUCH, Podolsk and IBRAE, Moscow; these concerned a detailed study of bundle quenching from high temperature; (2) Reactor Core Degradation; a modelling project simulating the fuel rod degradation and loss of geometry from IBRAE, Moscow; (3) METCOR projects from NITI, St. Petersburg on the interaction of core melt with reactor vessel steel; (4) INVECOR project, NNE Kurchatov City, Kazakhstan; this is a large-scale facility to examine the vessel steel retention of 60 kg corium during the decay heat; and finally, (5) CORPHAD and PRECOS projects, NITI, St. Petersburg undertook a systematic examination of refractory ceramics relevant to in-vessel and ex-vessel coria, particularly examining poorly characterised, limited data or experimentally difficult systems. © 2012 Elsevier B.V. All rights reserved. Source


Elshin A.,Alexandrov Research Institute of Technology NITI
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

This paper describes an application of the surface harmonics method to derivation of few-group finite difference equations for neutron flux distribution in a 3D triangular-lattice reactor model. The Boltzmann neutron transport equation is used as the original equation. Few-group finite difference equations are derived, which describe the neutron importance distribution (the multiplication factor in the homogeneous eigenvalue problem) in the reactor core. The derived finite difference equations remain adjoint to each other like the original equation of neutron transport and its adjoint equation. Non-diffusion approximations apply to calculation of a whole reactor core if we increase the number of trial functions for describing the neutron flux distribution in each cell and the size of the matrices of the few-group coefficients for finite difference equations. © Springer International Publishing Switzerland 2015. Source


Granovsky V.S.,Alexandrov Research Institute of Technology NITI | Khabensky V.B.,Alexandrov Research Institute of Technology NITI | Krushinov E.V.,Alexandrov Research Institute of Technology NITI | Vitol S.A.,Alexandrov Research Institute of Technology NITI | And 8 more authors.
Nuclear Engineering and Design | Year: 2014

During a severe accident with core meltdown, the in-vessel molten core retention is challenged by the vessel steel ablation due to thermal and physicochemical interaction of melt with steel. In accidents with oxidizing atmosphere above the melt surface, a low melting point UO2+x-ZrO 2-FeOy corium pool can form. In this case ablation of the RPV steel interacting with the molten corium is a corrosion process. Experiments carried out within the International Scientific and Technology Center's (ISTC) METCOR Project have shown that the corrosion rate can vary and depends on both surface temperature of the RPV steel and oxygen potential of the melt. If the oxygen potential is low, the corrosion rate is controlled by the solid phase diffusion of Fe ions in the corrosion layer. At high oxygen potential and steel surface layer temperature of 1050 °C and higher, the corrosion rate intensifies because of corrosion layer liquefaction and liquid phase diffusion of Fe ions. The paper analyzes conditions under which corrosion intensification occurs and can impact on in-vessel melt retention (IVR). © 2014 The Authors. Source


Bechta S.V.,Alexandrov Research Institute of Technology NITI | Granovsky V.S.,Alexandrov Research Institute of Technology NITI | Khabensky V.B.,Alexandrov Research Institute of Technology NITI | Krushinov E.V.,Alexandrov Research Institute of Technology NITI | And 13 more authors.
Nuclear Technology | Year: 2010

In case of in-vessel corium retention during a severe accident in a light water reactor, weakening of the vessel wall and deterioration of the vessel steel properties can be caused both by the melting of the steel and by its physicochemical interaction with corium. The interaction behavior has been studied in medium-scale experiments with prototypic corium. The experiments yielded data for the steel corrosion rate during interaction with UO 2+X-ZrO2-FeOy melt in air and steam at different steel surface temperatures and heat fluxes from the corium to the steel. It has been observed that the corrosion rates in air and steam atmosphere are almost the same. Further, if the temperature at the interface increases beyond a certain level, corrosion intensifies. This is explained by the formation of liquid phases in the interaction zone. The available experimental data have been used to develop a correlation for the corrosion rate as a function of temperature and heat flux. Source

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