[en] Full text: A life limiting factor of the austenitic steels in fuel assemblies is a functional limit due to swelling induced distortions of a fuel pin bundle in a wrapper tube. Austenitic steels are the very complex multi-components systems. Possible improvement of exploitation characteristics of ASS can be realized in increasing of stability of all structural components of ASS (defect structure elements, solid solution and precipitates), which can be achieved by optimal composition and thermo-mechanical treatment The maintenance of desirable swelling is directly coupled with maintaining a more stable microstructure during irradiation. Analysis of all structural components evolution in irradiated austenitic steels is carried out:-of dislocation structure which stability is determined by the stacking fault energy and by segregation processes possibility on the dislocation components, of solid solution state determined by point defects diffusion characteristic and by the concentration of elements radiation induced segregation of which changes the solid solution homogeneity, - of second phase precipitates the stability of which determines the radiation swelling resistance due to the increase of point defects strength and their recombination on the interface matrix-precipitate. It is shown that precipitates in irradiated austenitic stainless can be separated on two families: - Precipitates which are responsible for swelling suppression due to enhancing point defect recombination at particles-matrix inter MC (mainly TiC, NbC,VC), Fe₂P or Ni₃Ti (in a few cases). - Precipitates which serve as result of solid solution decay (especially due to removing from solution of Ni and Si as result radiation-induced segregation) and sign as loss of radiation stability at stages of structure evolution. It appears that this competition can be prolongated by optimization of composition and by the thermal-mechanical treatment. Possible mechanisms of swelling suppression in modern austenitic steels are described

[en] The system of thermals that makes the fine structure of a turbulent convective layer of a fluid is considered. A simplified probabilistic-geometrical approach is outlined that uses measurements along the observation line to determine the average in-plane parameters of the system. A dynamic equation for an isolated thermal interacting with its environment is derived. A Langevin equation similar to the stochastic equation for an ensemble of 'fast' Brownian particles is constructed for a system of thermals. The nonlinear Langevin equation for such a system leads to the associated kinetic form of the Fokker-Planck equation. It is shown that the stationary solution of the kinetic Fokker-Planck equation is identical to the Maxwell distribution and approximately consistent with the distributions measured in the turbulent convective layer of the atmosphere. (reviews of topical problems)

[en] Results of analysis of swelling behaviour of alloying austenitic steels are described from the point of view of the cooperative interaction of defect structure, solid solution decay and precipitates evolution. (orig.)

[en] Void swelling up to now is the main limiting factor for using austentic stainless steels (ASS) as structural materials for fast reactors and reactors of future generations. Attainment of commercially required high burn up of fuel (20-25% h.a.) demands structure matrials for claddings and wrappers, which must survive damages up to doses of 150-200 dpa. Now ferritic-martensitic and martensitic steels are widely considered as prospective materials for reactors of new generations including fast reactors. It demands a lot of data about swelling behaviour and features of structural changes under irradiation. It is natural to connect a loss of radiation stability with changes in their structure and composition under irradiation. Changing and degradation of original physical- mechanical properties of materials during irradiation (particular, void swelling and phase transformation) are results of evolution of complicated structure-phase interactions. Radiation resistance of steels can be improved by minor alloying elements and subsequent thermo-mechanical treatment and can be realized in increasing of stability of all structural components of theirs (dislocation structure, solid solution, precipitates system, etc.) during irradiation. Changing of Cr-content can also have an influence on radiation stability of ferritic type alloys. This paper will present results of ion and neutron irradiation of a wide spectrum of austenitic and ferritic- martensitic steels. Comparison of radiation behaviour of different steels will be done up to very high irradiation doses. Possible mechanisms of increasing radiation stability for these types of materials will be suggested. (author)

[en] Problems of life extension for working nuclear reactors and development of new-type reactors require that a lot of data be obtained about behavior of fuel and core structural materials under irradiation. Now, as part of several basic material science programs such data are being generated using charged particles accelerators. This report overviews the work performed at NSC KIPT as its contribution to the SMoRE CRP of the IAEA, to carry out a comprehensive program of simultaneous irradiation by self-ions and by helium and/or hydrogen ions of ferritic, ferritic-martensitic and austenitic steels. These alloys are attractive for use in advanced reactors, with our work focusing on high doses, high temperatures and both low-gas producing concepts and moderate to high-gas producing concepts. In this report we focus on three of our accomplishments, the first involving the development and use of triple ion irradiation to study the simultaneous introduction of displacement damage, helium and hydrogen on void swelling of austenitic steel, and the application of the results to provide a predictive swelling equation for application to VVER internals. Second, we focus on demonstrating that even in the absence of helium and hydrogen, ferritic-martensitic steel EP-450 and an ODS variant of the steel will swell significantly when irradiations are conducted to hundreds of dpa, but that ferrite grains begin to swell earlier than do tempered martensite grains. Third, we present results of some of our fundamental studies directed toward interaction and trapping of helium and hydrogen by radiation-induced microstructural sinks. (author)

No abstract available

[en] We describe the development of a large-scale high-throughput application for discovery in materials science. Our point of departure is a computational framework for distributed multi-scale computation. We augment the original framework with a specialized module whose role is to route evaluation requests needed by the high-throughput application to a collection of available computational resources. We evaluate the feasibility and performance of the resulting high-throughput computational framework by carrying out a high-throughput study of battery solvents. Our results indicate that distributed multi-scale computing, by virtue of its adaptive nature, is particularly well-suited for building high-throughput applications. (paper)

No abstract available