Effect of sodium carbonate on the oxidation of sublimates during niobium electron-beam remelting

The effect of sodium carbonate additions on phase formation during the air oxidation of the sublimates of niobium electron-beam remelting is studied by derivatography, X-ray diffraction analysis, and electron-probe microanalysis. The composition of the oxidation products changes with the heating temperature. The formation of sodium niobates and aluminates is detected by X-ray diffraction analysis at temperatures higher than 600°C. The oxidation of the sublimates is completed by the formation of sodium metaniobate and aluminate. Sodium carbonate additions are shown to accelerate the oxidation of the sublimates.     

Electrochemical properties of composite materials based on graphite and vanadium disilicide

Electrodes with different composition were prepared by the method of pressing followed by sintering of the graphite and vanadium disilicide powders, and their electrochemical and corrosion properties in water solutions of electrolytes were studied.Translated from Inzhenerno-Fizicheskii Zhuraal, Vol. 52, No. 5, pp. 802–707, May, 1987.     

Analysis of the turbine deblading in an HTGR with the CATHARE code

The direct coupling of a Gas Cooled Reactor (GCR) with a closed gas-turbine cycle leads to a specific dynamic plant behaviour. This behaviour is described and illustrated through computer analyses performed at CEA with the computer code CATHARE. This analysis requires a 1D code able to simulate the whole reactor, including the core, the vessel, the piping and the components (turbine, compressors, heat exchangers).This paper is devoted to deblading accidents. The problems and solutions encountered in various types of gas-turbines are presented: aero engines, steam turbines (EDF-Porcheville steam turbine accident feedback) and finally the feedback from previous High Temperature Gas Reactor experiments (EVO helium loop, HHT project and other HTR projects) are displayed. From this literature survey, some recommendations are drawn for a future High Temperature Reactor. It is shown that for safety reasons in case of deblading, a horizontal shaft aligned with the reactor vessel is recommended for the turbomachinery.This paper presents simulations of different scenarii performed with CATHARE code:

(a) Turbine deblading with and without reactor trip. In these calculations, a pessimistic assumption has been made: all turbine blades break off.

(b) Total flow blockage. The flow area is entirely blocked by the turbine blades.

(c) Partial flow blockage. Previous conclusions consider the worst cases of deblading and total flow blockage. An intermediate case based on a partial deblading has also been performed.

CATHARE results illustrate that the loss of turbine blades is accompanied by abrupt changes in the Power Conversion System and reactor flow conditions: large axial pressure drop, reverse flow through the core and high rate de-pressurization.     

Phase equilibria in the system Al-Rh

Methods of differential thermal analysis, x-ray diffraction, microstructural analysis and electron probe microanalysis are used to study alloys of the Al-Rh system over the whole concentration range. It is established that the phase of equiatomic composition AlRh melts congruently at 2060°C and it has an extended range of homogeneity (45.1–54.2 at.% Rh). The solubility of aluminum in rhodium reaches 9 at.%, decreasing to 6 at.% at 850°C. Coordinates are determined for the eutectic point l ⇆ AlRh + 〈Rh〉 as 70 at.% Rh and 1715°C. The existence of intermediate phases, their crystal structure, and also the method of forming phases in the field of composition rich in aluminum given in publications are confirmed. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 48–56, May–June, 2006.     

Internal-corrosion inhibitors for pipelines carrying deaerated heating water

The effect of internal-corrosion inhibitors on heating-system pipelines is investigated. Tests were conducted on a testing device for polarization measurements under conditions corresponding to the Rostov Heat-Supply System. The concentration of OEDP-zinc, which provides a high degree of protection from general corrosion, is determined. The reagent has been successfully incorporated into the Rostov No. 2 TPP. __________ Translated from élektricheskie Stantsii, No. 7, July 2007, pp. 37–43.     

Stable Oxygen and Carbon Isotopic Compositions of Lates stappersii Otoliths from Lake Tanganyika,East Africa

In this study, we measured growth trends in oxygen and carbon isotopic ratios in whole sagittal otoliths from three adult centropomid fish (Lates stappersii) from each of three sub-basins of Lake Tanganyika, East Africa. Sampling density was 20 to 50 samples per otolith. Both δ¹⁸O and δ¹³C values increase with age. The δ¹⁸O data suggest that otoliths were precipitated near the expected equilibrium with the ambient environment (ca. +3.5‰) and support a migration pattern from surface waters during larval stages to deeper waters (40 to 80 m) for mature fish. Relatively high δ¹⁸O values in the southern sub-basin are consistent with cooler temperatures in the region during seasonal upwelling. The δ13C increase from otolith core to edge is large (up to 4‰) and is interpreted as due to ontogenetic changes in diet and contributions from a decrease in the proportion of respired CO₂ incorporated into otolith carbonate as metabolic rates of the fish dropped with maturity. The data seem to successfully reveal life strategy and migration patterns of L. stappersii, document regional differences in lake conditions, and provide a record of temperature within the water column during which the fish lived. Higher resolution studies and analyses of historical samples could be used to constrain modern and past growth patterns, and to reconstruct past temperature gradients and productivity patterns in the lake.     

Internal-corrosion inhibitors for pipelines in heat-supply systems carrying water with a high oxygen content

The reliability of heat-supply systems is determined primarily by internal corrosion of the pipelines. The concentration of oxygen in the water exerts a major influence on the corrosion. In systems with a standard oxygen content, OéDF-Zn is a highly effective corrosion inhibitor. However, there are systems in which the quality of deaeration of the make-up water of the heat-supply system is low (or deaeration is nonexistent), and the concentration of oxygen is considerably above the standard value. Classed among these systems, for example, are the HWS systems, which are incorporated into closed heat-supply systems. The oxygen concentration in these systems is analyzed to assess the situation. __________ Translated from élektricheskie Stantsii, No. 6, June 2007, pp. 35–39.