We generalize the celebrated results of Bernhard Riemann and Gaston Darboux: we give necessary and sufficient conditions for a bilinear form to be flat. More precisely, we give explicit necessary and ...sufficient conditions for a tensor field of type (0, 2) which is not necessary symmetric or skew-symmetric, and is possibly degenerate, to have constant entries in a local coordinate system.
The article presents the main provisions of the concept of the design of the SVBR-100 civilian reactor that meets the requirements for Generation IV nuclear technologies, which is being developed on ...the basis of a critically analyzed experience in developing and operating lead-bismuth-cooled reactor plants. The authors describe the current status of the project and the prospects for the use of such reactor plants in the nuclear power industry after demonstrating their reliability and safety in the operating conditions of a pilot commercial power plant.
The article is devoted to the history of the creation of lead-bismuth-cooled reactor units (RUs) for nuclear-powered submarines (NPSs), which were developed in the absence of the necessary knowledge ...and experience, as well as under strict deadlines for completing work, which practically excluded the possibility of carrying out related full-scale scientific research. This led to a number of failures at the stage of developing this unique technology, the causes of which were later identified and eliminated. The authors explain the reasons for choosing a lead-bismuth eutectic alloy as a coolant, outline the main scientific and technical problems solved in the course of developing a lead-bismuth-cooled reactor unit, including those related to the coolant and corrosion resistance of steels, consider issues of ensuring radiation safety during work related to the release of polonium, ensuring the reliability of steam generators, incidents and accidents that occurred during the period of operation and ways to eliminate their causes.
The article considers EP823 12% Cr ferrite-martensite steel, selected in terms of the material for fuel rod claddings, as well as the control and protection elements of BREST OD-300 and SVBR-100 ...reactors. Based on the analysis of the published results of non-isothermal circulation facility tests, a comparison of EP823 steel corrosion rates in a liquid lead and lead-bismuth eutectic system demonstrated their proximity.
Accumulation of plutonium extracted from the spent nuclear fuel (SNF) of light water reactors is one of the central problems in nuclear power. To reduce out-of-the-reactor Pu inventory, leading ...nuclear power countries (France, Japan) use plutonium in light water power reactors in the form of MOX fuel, with half of Pu fissioning in this fuel. The rest of Pu cannot be reused easily and efficiently in light water reactors because of the high content of even isotopes. Plutonium for which there are no potential consumers is accumulated.
Unlike thermal reactors, fast reactors take plutonium of any isotopic composition. That makes it possible to improve plutonium isotopic composition and to reduce the fraction of even isotopes to the level that allows reuse of such plutonium in thermal reactors.
The idea of changing the isotopic composition of Pu in fast reactors is well-known. The originality of the research lies in applying this idea to combine the fuel cycles of fast and thermal reactors. Pu isotopic composition can be improved by combining certain operational activities in order to supply fuel to thermal and fast reactors. Scientific and technological justification of the possibility will let Russian BN technologies and French MOX fuel technologies work in synergy with thermal reactors.
Possible options of organization of two-component energy system with closed nuclear fuel cycle (CNFC) and new business potential associated with provision of CFC services to foreign customers are ...examined.
Dominating role in the development of nuclear power generation is assigned to VVER reactors with gradually increasing fraction of sodium-cooled fast breeder reactors (FR) incorporated within the joint nuclear fuel cycle operated on MOX-fuel.
Components of such energy system perform the following functions:
1. Fast reactors:
Generate electric power in base-load mode (possibility of fine tuning of reactor power within limited range (100 – 75 – 100%) is assumed);
Utilize waste and/or regenerated uranium for re-fueling power reactors, produce plutonium applicable to the maximum extent for manufacturing MOX-fuel for VVER reactors;
Incinerate long-lived highly radioactive wastes – minor actinides separated during reprocessing spent nuclear fuel of FR and VVER reactors.
2. VVER reactors:
Generate electricity in compliance with manoeuvrability requirements imposed by the utility company operating the energy system;
Utilize MOX-fuel instead of UO
2
fuel;
Are offered for export with the option of returning SNF back to Russia;
Plutonium extracted from VVER spent fuel is used for manufacturing MOX-fuel for SFR.
3. Nuclear fuel cycle facilities:
Provide reprocessing of SNF from VVER and SFR with extraction of nuclear materials for recycling;
Use depleted or reprocessed uranium and plutonium extracted from spent nuclear fuel for manufacturing MOX-fuel;
Provide partitioning of RAW for subsequent utilization of minor actinides and reduction of risks of proliferation of nuclear materials, conditioning and disposal of RAW.
Russia possesses capacities for establishing the two-component system with CNFC, as well as the new business approach to rendering CNFC services to foreign customers.
Nous étudions dans cet article des suites de métriques à aire et courbure bornées sur une surface compacte S. Nous démontrons que, si la structure conforme reste bornée, alors ou bien il existe une ...sous-suite convergente, ou bien il existe un point où une certaine quantité positive de courbure se concentre. Ce niveau de concentration est calculé, (dans le cas où la courbure est bornée uniformément, ce niveau est 2π).
In this paper, we study sequences of metrics on a compact surface S, with bounded area and curvature. We prove that, if the conformal structure of these metrics remains bounded, then either the sequence has a convergent subsequence or there exists a point at which a certain amount of positive curvature concentrates. This level of concentration is computed. (When the curvature is uniformely bounded, then this level is 2 π.)
On the equation DutHDu=G Bandyopadhyay, S.; Dacorogna, B.; Matveev, V. ...
Nonlinear analysis,
January 2022, Letnik:
214
Journal Article
Recenzirano
In this article, we want to find a map u:Ω¯→Rn solving, in Ω, the equation u∗H=Gi.e.DutHuDu=Gand coupled, on ∂Ω, either with the Dirichlet–Neumann problem u=φandDu=Dφor the purely Dirichlet problem ...u=φwhere Ω⊂Rn is a bounded open set, G,H:Rn→Rn×n and φ:Ω¯→Rn are given. We discuss the case where G and H are not necessarily symmetric or skew-symmetric, but have invertible symmetric parts.
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