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Miniature disk-shaped specimens have been used to evaluate the tensile properties of boiler steels 20, 12Ch1MF, 12Ch11V2MF and 16GNM at room temperature by using the small punch test. Conventional uniaxial tensile tests of standard cylindrical specimens from the same materials have been also performed for comparison. On the basis of comparative analysis a correlation between the maximum punch force and tensile strength has been obtained that allows accurate measurement of the tensile strength with the small punch test. It has been found that the yield strength of the materials could not be determined with sufficient accuracy by means of this test.

The present paper provides experimental data from short-term, full-scale experiments of a high-pressure pulverized firing (PF) boiler, TP-67, firing oil shale after a retrofit to use vortex combustion (VC) technology. The essence of VC technology consists of the generation, at a lower part of the furnace, of a circulatory motion of gas relative to the horizontal axis (horizontal vortex) by rearranging the geometry of the combustion air injection and the fuel feeding into the combustion chamber. The tests were conducted at three boiler loads: 50% (160 t/h), 75% (240 t/h) and 100% (320 t/h). During the experiments, fuel samples of air-solids in the conduit and samples of bottom ash and fly ash from inertia dust collectors after the super heater (SH) and economizer (ECO), as well as fly ash from the electrostatic precipitator (ESP) of the first and second fields, were taken from both the left and the right sides of the boiler. The gas analysis was performed at the ESP exit. It was attempted to measure temperature distribution in the combustion chamber. Temperature measurements in the furnace using an infrared thermometer showed that the maximum temperature did not exceed 1150 °C, and there was slight temperature nonuniformity across the combustion chamber. During the tests, the ash distribution at different boiler ash discharge ports was obtained. Analysis of the bottom ash chemical composition showed a considerable increase in the amount of unburned carbon and marcasite S p. The retrofit of the boiler to use VC technology did not result in a reduction in the amount of SO 2 emissions, indicating an even weaker process of binding sulphur oxides in the furnace as compared to PF.

The results of computational and experimental studies of the thermohydraulic characteristics of lead coolant-working body contact heat exchange are presented. Water, a steam-water mixture, and 100-350°C, 1-25 MPa steam were bubbled through 0.6-2 mm in diameter openings, under a layer of lead ranging in thickness from 100 to 3000 mm, at temperatures 350-600°C into a free space in a steam generator and into space of a steam generator crowded with piping-system simulaters in the case of bubble and plume efflux and with fragmentation of the working body stream against a tubular barrier. The following were determined in the experiments: the bubble size distribution, the rise velocity of the bubbles, the structure of the two-component flow (bubble distribution inside the lead), the change of the temperature of the bubbles as they rise, the characteristics of the vaporization of a water drop in a bubble, and the temperature pulsations in the two-component lead-working body flow.Studies of the contact heat exchange during bubbling of water, a steam-water mixture, and 100-350°C, 1-25 MPa steam through 0.6-10 mm in diameter openings in a layer of lead ranging in thickness from 100 to 3000 mm at temperatures 350-600°C into a free space in a steam generator and into a space in a steam generator crowded with piping-system simulators were performed at the Nizhegorod University for bubble and plume efflux of a stream of the working body and for a working-body stream fragmented against a tubular barrier. The following were determined in the experiments: the bubble size distribution, the rise velocity of the bubbles, the change in temperature as the bubbles rise, the structure of the two-component flow (distribution of the bubbles inside the lead), and the characteristics of the vaporization of a water drop inside a bubble and the temperature pulsations.The experimental data and computational analysis are used as a basis to propose a model of contact heat exchange in the presence of an interloop leak in the steam generators of BREST type reactors. According to the "leak before rupture" concept, the initial efflux of water will occur through a small opening (crack, ruptured thin section of an abraded wall, and so on). The working body (355°C, 30 MPa) passing through such an opening will partially vaporize and partially condense as a result of a decrease of the pressure to the static level inside the lead-coolant loop (0.8 MPa); this is illustrated in Fig. 1 [1, 2]. It was confirmed experimentally and theoretically that the working-body stream formed breaks up as a result of volume boil-

The results of experimental investigations of the heat transfer by lead coolant in the ring-shaped gaps of a circulation loop during monitored and controlled mass transfer and mass exchange of oxygen and impurity are presented. The investigations were performed in a loop with circulation of lead coolant at temperature of 450-550°C, average velocity 0.1-1.5 m/sec, Peclet number 500-6000, and heat flux 50-160 kW/m 2 . The oxygen content in the loop was varied from the value for thermodynamic activity 10 −5 -10 0 to saturation and above with formation of lead oxide deposits on the heat transfer surface. The processes in a non-isothermal liquid metal loop with heating (core) and cooling (steam generator) experimental sections simulate the dependence of the heat transfer characteristics in the loop on the impurity mass transfer.Liquid metals are attractive high temperature coolants for nuclear power because of their physical characteristics: low pressure, high heat transfer coefficient, and therefore low temperature difference between the surface of fuel elements and coolant with high heat flux density. The experimental and computational techniques, the new approaches to solving heat transfer problems, and operating experience make it possible to study the simultaneous effect of the impurity content, the technological processes of cleaning in the loop, and accident processes where impurities enter the loop on the characteristics of heat transfer in hot and cold zones of the loop. The results of the investigations make it possible to formulate more accurate recommendations about the norm for the impurity content and more accurate computational formulas for determining heat transfer surfaces.In Nizhnii Novgorod Technical University, an experimental stand has been developed and investigations in which the local characteristics of heat transfer from a tube wall to the lead coolant and from the lead coolant to the tube wall were determined simultaneously while monitoring and regulating the oxygen content in the coolant have been performed. Previously, the characteristics of heat transfer in lead and lead-bismuth coolants were performed separately under conditions of heating and cooling of the coolant [1, 2]. The present experiments [3] differ from previous experiments in that while monitoring and controlling the variation of the state and composition of impurities in the coolant and envelope the characteristics of heat transfer on heating and cooling sections are measured simultaneously.The experimental stand possesses two loops: one with lead and the other with lead-bismuth alloy with centrifugal pumps. The flow rate of the liquid metals is monitored with magnetic flowmeters and by a volume method -a calibration flow-measuring volume -and the oxygen content and lead was measured with thermodynamic activity sensors based on a solid galvanic concentration element. The equipment and pipelines in contact with lead were made of 08Kh18N10T steel and are electrically heated and thermally insulated.