Tests in an MR reactor of experimental fuel elements of the VVÉR-1000 reactor

Conclusions In an MR reactor performance tests of 16 fuel assemblies, with elements having essentially the same structure as standard VVÉR-100 fuel elements, were carried out. Tests of five more fuel assemblies are continuing. Of the 16 assemblies, 13 were studied in a hot laboratory.The tests in the MR, carried out at high loads and with a large number of transition processes, as well as the postreactor studies, indicated that fuel elements of the specified design (with initial helium pressures of 1.96–2.45 MPa) have a high reliability. None of the elements of the fuel assemblies studied malfunctioned due to design defects or faults in their fabrication. During the tests the jackets were subject to a little oxidation and hydrogenation (zirconium-oxide film<3 m thick, hydrogen content less than 0.008% by mass), and their plasticity remained high (the relative elongation at the working temperature remained at the 20% level).Translated from Atomnaya Énergiya, Vol. 62, No. 5, pp. 312–317, May, 1987.     

Evaluation of the parameters of an experimental tokamak fusion-reactor and the influence of the indeterminacy of the plasmaphysical data

Conclusion Analysis using a simplified technicoeconomic model of a tokamak reactor and the procedures of graphic processing of the results allow the regions of the optimum parameters of an experimental minimum-cost reactor with various limitations to be determined. When refined and ignition scalings are taken into account simultaneously and an appropriate optimization is made we get the parameters of the experimental reactor, which differ slightly from the basic variant (in particular, a lower neutron load on the first wall). The reactor cost in this case should increase by 15–25% in comparison with the basic variant and remains virtually constant when the most favorable ignition scaling (ASDEX) is realized.Translated from Atomnaya Énergiya, Vol. 62, No. 1, pp. 22–28, January, 1987.     

A theoretical and experimental investigation of the plastic deformation process of sintered composite materials. III. An investigation of the spatial redistribution of the phases of a composite material in plastic deformation of it

Conclusions As in porous bodies, in dense composite materials plastic deformations may cause an increase in the local concentration (density) of elements of the hard phase in zones of active flow of the material. The intensity of structural rearrangement (regrouping) of the phases in a composite material is determined by the character of the relationship of the function of plasticity of the medium to the amount of the average (hydrostatic) stresses in the body being deformed and is related to the degree of deformation obtained by this body through the derivative (_ij)/_ii. The mutual disposition of the elements of the hard phase in a material may be fixed in any stage of the process of working by pressure if the conditions are created for combined flow of the different phases in the body being deformed.Translated from Poroshkovaya Metallurgiya, No. 10(298), pp. 53–57, October, 1987.     

Possibility of Using Material Activated with Alkali as a Binder for Refractory Concretes

Refractories and Industrial Ceramics - This study aims to investigate the feasibility of alkali activated slag as a sole binder for refractory concretes. The concrete samples prepared are subjected...     

Fluctuating NMDA Receptor Subunit Levels in Perirhinal Cortex Relate to Their Dynamic Roles in Object Memory Destabilization and Reconsolidation

Reminder cues can destabilize consolidated memories, rendering them modifiable before they return to a stable state through the process of reconsolidation. Older and stronger memories resist this process and require the presentation of reminders along with salient novel information in order to destabilize. Previously, we demonstrated in rats that novelty-induced object memory destabilization requires acetylcholine (ACh) activity at M₁ muscarinic receptors. Other research predominantly has focused on glutamate, which modulates fear memory destabilization and reconsolidation through GluN2B- and GluN2A-containing NMDARs, respectively. In the current study, we demonstrate the same dissociable roles of GluN2B- and N2A-containing NMDARs in perirhinal cortex (PRh) for object memory destabilization and reconsolidation when boundary conditions are absent. However, neither GluN2 receptor subtype was required for novelty-induced destabilization of remote, resistant memories. Furthermore, GluN2B and GluN2A subunit proteins were upregulated selectively in PRh 24 h after learning, but returned to baseline by 48 h, suggesting that NMDARs, unlike muscarinic receptors, have only a temporary role in object memory destabilization. Indeed, activation of M₁ receptors in PRh at the time of reactivation effectively destabilized remote memories despite inhibition of GluN2B-containing NMDARs. These findings suggest that cholinergic activity at M₁ receptors overrides boundary conditions to destabilize resistant memories when other established mechanisms are insufficient.     

Water-Acetonitrile Ratio in Perchlorate Cadmium Bath and the Effectiveness of the Addition of Crown-Ester

It is shown that the strongest deceleration of the electrodeposition of cadmium in inhibited media is observed in the domain of loosening the structure of a mixed solvent (0.45 x ₂ 0.25) when the molecular adsorption of organic solvent on Cd is maximum. The process is maximally facilitated in the domain of ordering the acetonitrile's (AN) structure (0.9 x ₂ 0.75), where perchlorate anions dominate at the cathode surface. Crown-ester exhibits maximum inhibition effect under the conditions of preferential adsorption of its molecules, i.e., in the domain of the prevalence of the nonaqueous component in the mixture (x ₂ 0.95).     

Change in structure of an iron-chromium alloy during service

Conclusions As the result of long high-temperature heating the structure of the iron-chromium alloy changes. After service at 1280–1300°C for 500 h light precipitates at the boundaries and in the body of the grain enriched with chromium and molybdenum are observed, which may be considered as the result of separation of the ferrite and as a preparatory stage before precipitation of -phase. In the surface zones of the feeder, nitride and oxide inclusions and products of gas corrosion are observed.Institute of Problems of Casting, Academy of Sciences of the Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 29–30,January, 1985.     

Converting jarosite residues into compact hematite products

Sodium jarosite is readily converted into hematite by hydrothermal reaction at temperatures greater than 220°C. Although the initial acid and ferric ion concentrations must be kept low to avoid the unwanted formation of Fe(SO₄)(OH), the conversion reaction is unaffected by modest concentrations of ZnSO₄, FeSO₄ or Na₂SO₄. Hematite seeding is desirable to promote the reaction and to stabilize the reaction system. The hematite conversion product will likely contain ～0.5% Zn and ～2% SO₄; most of the arsenic in the jarosite will remain with the hematite.     

Effect of deposition conditions on the properties and annealing behavior of cold-sprayed copper

The deposition of copper by cold gas dynamic spraying has attracted much interest in recent years due to the capability to deposit low-porosity oxide-free coatings. However, it is generally found that as-deposited copper has a signicantly greater hardness, and potentially lower ductility, than bulk material. In this article, copper was deposited by cold spraying using helium as the driving gas at both 298 and 523 K. Evidence is presented indicating that the material sprayed at the lower temperature exhibits a lower dislocation density throughout the grain structure than the material sprayed at the higher temperature. The low stacking fault energy of copper restricts recovery during annealing, and thus microstructural changes during annealing only proceed once recrystallization begins. The material sprayed at low temperature (with the low dislocation density) exhibited recrystallization at annealing temperatures as low as 373 K with a corresponding reduction in hardness. However, the copper sprayed with helium at 523 K was resistant to annealing at temperatures up to 473 K where the dislocations in the structure prevented recrystallization. However, at higher temperatures, recrystallization did proceed (with corresponding reductions in hardness). The fracture behavior of the copper that was cold sprayed with helium at 523 K, both in the as-sprayed condition and following annealing, was measured and explained in terms of the annealing mechanisms proposed. The original version of this paper was published in the CD ROM Thermal Spray Connects: Explore Its Surfacing Potential, International Thermal Spray Conference, sponsored by DVS, ASM International, and HW International Institute of Welding, Basel, Switzerland, May 2–4, 2005, DVS-Verlag GmbH, Düsseldorf, Germany.     

Phase diagram and electrical behavior of silicon-rich iridium silicide compounds

The iridium-silicon phase diagram on the silicon-rich side was investigated by means of X-ray powder diffraction, density, differential thermal analysis (DTA), metallography, microprobe analysis, and electrical resistivity. Attempts were made to prepare eight previously reported silicon-rich iridium silicide compounds by arc melting and Bridgman-like growth. However, microprobe analysis identified only five distinct compositions: IrSi, Ir₄Si₅, Ir₃Si₄, Ir₃Si₅ and IrSi_≈3. The existence of Ir₂Si₃, Ir₄Si₇, and IrSi₂ could not be confirmed in this study. DTA in conjunction with X-ray powder diffraction confirm polymorphism in IrSi_≈3, determined to have orthorhombic and monoclinic unit cells in the high and low temperature forms. A eutectic composition alloy of 80.5 ± 1 at.% Si was observed between IrSi_≈3 and silicon. Both Ir₄Si₅ and Ir₃Si₄ exhibit distinct metallic behavior while Ir₃Si₅ is semiconducting. IrSi and IrSi_≈3 exhibit nearly temperature-independent electrical resistivities on the order of (5–10) × 10⁻⁶ ω m.