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[en] It is pointed out that definite theoretical predictions on the influence of a soft mode on the Mossbauer spectrum can not be made. Cusped-shape anomalies in the Debye-Waller factor and changes in the line shape may be possible. (author)
[en] Compounds of rare earth metals manifesting phase transitions with the change of valence and states with intermediate valence are considered. Peculiarities of the substances which are demonstrated in electronic and lattice characteristics (heat capacity, magnetic susceptibility, resistance, compressibility etc.) are discussed. It is shown that anomalies in behaviour of physical values are conditioned by peculiarities of electron energy spectrum: as to the energy states with different number of f-electrons on the centre, of the type 4fsup(n) and (4fsup(n-1) + conductivity electron) proved to be similar. Main theoretical approaches, used to describe properties of the compounds and factors, determining the character of phase transitions in them are briefly outlined. Discussion of physical nature and character of the main state of systems with intermediate valence is made
[en] Analytically studied is dynamics of steam bubble separation in case of boiling. It is shown that a non-uniform vapour flow through the steam bubble surface which is accounted for by the non-uniform temperature field in liquid in case of a bubble growth on the boiling surface may result in intensive evaporation due to the reactive efficiency of the evaporated molecules. The evaporation force which far exceeds the buoyancy force and depends upon the shape of a steam bubble causes its separation
[en] The main factors that determine the cost of high-level waste (HLW) vitrification are the waste loading (which determines the volume of glass) and the melting rate. Product quality should be the only factor determining the waste loading while melter design should provide a rapid melting technology. In reality, the current HLW melters are slow in glass-production rate and are subjected to operational risks that require waste loading to be kept far below its intrinsic level. One of the constraints that decrease waste loading is the liquidus-temperature limit. close inspection reveals that this constraint is probably too severe, even for the current technology. The purpose of the liquidus-temperature constraint is to prevent solids from settling on the melter bottom. It appears that some limited settling would neither interfere with melter operation nor shorten its lifetime and that the rate of settling can be greatly reduced if only small crystals are allowed to form
[en] Two steam explosion experiments were performed in the TROI (Test for Real cOrium Interaction with water) facility by using partially oxidized molten corium (core material), which is produced during a postulated core melt accident in a nuclear reactor. A triggered steam explosion occurred in one case, but none occurred in the other case. The dynamic pressure and the dynamic load measured in the former experiment show a stronger explosion than those performed previously with oxidic corium. Meanwhile, a steam explosion is prohibited when the melt temperature is low, because the melt is easily solidified to prevent a liquid-liquid interaction. The partially oxidized corium could enhance the strength of a steam explosion due to the thermal energy from an exothermic chemical reaction between the water and the uranium metal with a sufficient superheat extracted during melting. The melt composition effect on a steam explosion load, which was not included during the nuclear design, needs to be included in it
[en] In order to operate in reliable and safe conditions sodium Fast Reactor, it is necessary to maintain the quality of the coolant. Maintaining the sodium coolant circulating in high temperature in pure state is one of the most important conditions required for securing efficient and safe operation of these installations. The required quality of the coolant circulating in sodium cooled loops is maintained by means of special purification devices, which use different physical principles for binding the impurities that have to be removed from sodium. Cold trapping based on the crystallization of Na2O and NaH, by lowering the sodium temperature below the saturation temperature and thus creating the optimal conditions for Na2O and/or NaH nucleation and growth on a steel packing distributed in an auxiliary cooled vessel. Primary sodium purification with cold trap located in the reactor vessel has two disadvantages, transfer of a radioactive fluid outside the vessel and risk of partial draining of primary sodium. So new concept, the integrated purification system was developed for Superphenix, FBR-1&2, and BN- 1200 in order to provide high efficiency, safety, and reliability in operation. This paper deals with the developments of the integrated purification systems for the primary circuits of a SFR. The objective of the report is to provide researchers with technical information necessary for the design and construction of technological facilities for the integrated sodium purification system by reviewing the current state of technical developments for advantages, disadvantages, limitations, and safety of a integrated sodium purification system. Based on these results, a future plan for development of the integrated sodium purification system can be established.
[en] Development of supramolecular polymer has attracted much interest because of their interesting properties such as stimuli-responsiveness, recycling, self-healing and degradability, and their consequential applications. The essential feature of this class of polymers is the self-assembly of discrete monomeric subunits via non-covalent interactions or dynamic covalent bonds. Among the many monomeric subunits, pillar[n]arenes have been ideal building blocks for the fabrication of polymeric supramolecules because of their intrinsic characteristics. The ring-shaped morphologies in supramolecular polymer P are probably due to the tendency of the end-to-end connection in the solid state of long flexible supramolecular chains. The size increase of nano-rings as the stepwise addition increases might be due to the fact that the linear supramolecular polymer P in solution seems to be maintained until the nano-ring formation by solidification
[en] Based on our achievements and that of peers of home and abroad, several aspects of nodular defect are summarized and reviewed. The size, shape and surface properties of nodule seed determinate the size, boundaries continuity and topography of nodule. The seed sources are mainly the residue during the processing and cleaning of substrate, contamination from the coating chamber and particulate from the evaporation source material. The corresponding methods to eliminate the seed source are given. The electronic field enhancement is another main reason for the damage susceptibility of nodule. Laser conditioning and mitigation method can improve the capacity of laser damage resistance. (authors)
[en] The rate of spontaneous emission of an emitter placed in a disordered one-dimensional photonic crystal is analyzed. It is shown that the spontaneous emission of a dipole placed in a disordered photonic crystal can either be enhanced (if the frequency corresponds to an optical eigenmode of the structure) or suppressed (if the frequency lies in the band gap or the position of the emitter corresponds to a node in the electric- field profile of the eigenmode). It is demonstrated that, for high levels of disorder, the photonic band gap is narrowed and the emission rate at the center of the band gap becomes significantly different from zero. Furthermore, for high levels of disorder, localized states featuring significantly enhanced spontaneous emission may appear within the photonic band gap.