The article presents the results of pulse heating measurements for the thermal resistances of contacts of liquid lead with Al2O3 ceramics and steel in gaps, modeling a heat conducting liquid-metal sublayer in the developed fuel rods of fast reactors of a new generation. The method of obtaining and processing experimental data is described, the results of estimating the measurement error are presented, and the dependence of thermal resistances of liquid lead contacts in model gaps on temperature and number of melting and crystallization of lead is investigated. Based on the experimental results, the thermal resistance of a heat conducting liquid-metal sublayer in fuel rods is evaluated.

The article presents the results of measurements of thermal conductivity coefficients of Pb-Na with the content of the latter of 20 at.

The article presents the results of measuring the coefficient of thermal conductivity of lead in the temperature range of 350–1000 °C using the pulse heating method. The methodology of processing experimental data is described. The estimates of the experimental data error are given. The difference in the content of impurities in the lead samples is shown to have an in significant effect on the thermal conductivity coefficient of the lead melt. The deviation of the experimental data on the thermal conductivity of lead from the proposed approximating function does not exceed ±2

Oxide layers formed by plasma-electrolytic oxidation (PEO) are characterized by a sufficiently high porosity, which influences almost the whole complex of service characteristics. However, the known data on the integral porosity of PEO-produced layers are rather contradictory, and the nature of the pore size distribution in these layers remains understudied. As a result of processing the images of the layer cross-section produced in a wide magnification range (scanning electron microscopy – SEM, image-based analysis), the authors obtained the pore size distribution in the range of 10 nm to 10 µm, which is sufficiently well described by a lognormal distribution function (pore geometry was approximated by a spherical shape). Such distribution pattern indicates the nature of pore formation, which can be related to the thermally activated process of gas emission from a liquid melt, the volume and average temperature of which, in their turn, depend on the micro-arc discharge energy. The paper presents the results of identifying the oxide layer phase composition and crystallites sizes by the X-ray crystallography method. Comparing the results of X-ray spectral microanalysis and X-ray crystallography, the amorphous component phase composition was evaluated. Using the stationary method and the method of pulsed laser heating, the authors determined the thermal conductivity of the initial oxide layer and the layer after the removal of its highly-porous outer part. The porosity values obtained experimentally and calculated based on the analysis of SEM-images and the results of determining the phase composition, including amorphous phases, allowed evaluating the oxide layer thermal conductivity with the help of four known analytical models. The results of calculating the thermal conductivity using the Loeb model showed good convergence with the experimental results obtained in this work. The modeling demonstrated that the size of crystallites influence the oxide layer thermal conductivity much less than the porosity and amorphous phase.

The article presents the results of studying the density of steel 12Kh18N10T and the coefficient of thermal expansion TEC (α) in the temperature range from 100 to 850˚С. The measurements were carried out using a DIL-405 C dilatometer. Steel 12Kh18N10T will replace traditional TVEL cladding materials, which are made of zirconium material. The cladding made of steel 12X18H10T can be used as a Tolerant fuel. It is shown that the thermophysical properties and accurate dilatometric results of studies of steel 12Kh18N10T make it possible to use steel cladding in fuel assemblies of a VVER reactor. The article presents the results of comparison with similar data from the State Service of Standard Reference Data system.

Pressurized water reactors (PWR, VVER, EPR, CAP) are currently the backbone of the world's nuclear power industry. The fuel in this type of power plants is uranium dioxide pellets enclosed in a sealed zirconium shell. Loss Of Coolant Accident (LOCA) emergencies can cause partial or complete destruction of zirconium claddings and accumulation of hydrogen in the reactor pressure vessel and reactor building. This is due to the so-called steam-zirconium reaction: an exothermic process of zirconium oxidation in an atmosphere of saturated water vapor at temperatures above 900 °C. The products of this reaction are hydrogen and brittle zirconium oxide, which collapses under the action of its own weight and the weight of the fuel column. Fuel for pressurized water nuclear power reactors that is resistant to a loss of coolant accident is the subject of research around the world. One of the ways of implementation is the use of alloys of the Fe – Cr – Al system as a fuel element cladding material, since they have high corrosion resistance in water. The work is devoted to the determination of the coefficient of linear thermal expansion (CLTE), specific heat capacity, thermal conductivity and the influence of composition on them for Fe – Cr – Al – Si alloys in the temperature range of 200–1000 °C. New data on the dependence of the thermophysical characteristics of alloys of the Fe – Cr – Al – Si system on temperature and chromium concentration have been obtained. It is shown that the CLTE, specific heat capacity and thermal conductivity weakly depend on the chromium content in the studied concentration range, the main contribution of alloying elements is made by the position of the Curie.

The thermal conductivities for the traditional fuel UO 2 and for the Accident Tolerant Fuel (uranium Molybdenum alloy, U-10Mo and uranium silicide, U 3 Si 2 ) are calculated and compared. Then the temperature distributions on these core reactor, namely on the surface of the rod and in the center line of the rod were determined. The calculation is carried out using MATHCAD program. The calculations showed enhancement of thermal conductivity of the Accident Tolerant Fuel as they increased linearly with increasing temperature, and reduction of their center line temperatures of the rods. Beside, their steep thermal gradient, which may reduce the induced heat stresses in the core of the reactor.

The work presents the results of investigation of the thermal conductivity of the coating formed by the method of microarc oxidation (MAO) on a deformable aluminum alloy AK4-1. The article describes the methodology of the research including the formation of the MAO layer, the study of the structure and composition of the coating and the determination of its coefficient of thermal conductivity. The methodological approach to determining the thermal conductivity is based on measuring the thermal diffusivity of the oxide layer by pulsed laser heating, as well as calculating the heat capacity and density of the coating based on the data of layer-by-layer X-ray phase analysis is proposed. During the calculations, the porosity of the coating was taken into account. In accordance with the proposed procedure, it is established that the MAO layer has a thermal conductivity coefficient of ~ 5 W/(mK). The value obtained is comparable with the known results, but is significantly lower than the values of the thermal conductivity of the single phases constituting the coating. It is assumed that this effect is related to the feature of the structure of the MAO layer.

The paper presents numerical investigation of the thermal resistance of the contact surface of heat exchange and melt of lead. Using a geometric model of the contact area, developed on the basis of image analysis of the contact surfaces of steel and lead, the calculation of the contact resistance between molten lead and the surface of steel EP-823. The results of the calculations are compared with experimental data on thermal resistance of contact of the lead with steels EP-823 and 312 steel.

Information about the change of thermal properties of the fuel elements needed for a successful and safe operation of the nuclear power plant. At present, the existing amount of information on the fuel thermal conductivity change and "fuel-shell" thermal resistance is insufficient. Also, there is no technique that would allow for the measurement of these properties on the non-destructive way of irradiated fuel elements. We propose a method of measuring the thermal conductivity of the fuel in the fuel element and the contact thermal resistance between the fuel and the shell without damaging the integrity of the fuel element, which is based on laser flash method. The description of the experimental setup, implementing methodology, experiments scheme. The results of test experiments on mock-ups of the fuel elements and their comparison with reference data, as well as the results of numerical modeling of thermal processes that occur during the measurement. Displaying harmonization of numerical calculation with the experimental thermograms layout shell portions of the fuel cell, confirming the correctness of the calculation model.

A design of the speckle-interferometric dilatometer intended for studying thermal expansion of solid bodies at temperatures of 20–100°C is described. The calibration results for the thermal coefficient of linear expansion of copper, Armco iron, and 12Kh18N10T steel samples are given.

A technique for measuring the thermal resistance of the liquid metal–structural steel interface is proposed. The results ofmeasurements of the thermal resistance of the interface between Pb-Mg-Zr alloys and EP-823 steel and the thermal conductivity of Pb-Mg-Zr alloys in the temperature range of 350–900 °C are presented.

The structure and thermophysical properties of materials formed in the system Dy2O3–HfO2 (molar ratio 1 : 3 to 3 : 1) as a result of isothermal firing of x-ray amorphous mixed hydroxides at temperature to 1600°C are investigated. It is shown that for ratios 1 : 3 to 1 : 1 the crystallization process results in the formation of single-phase solid solutions with the structure of defective fluorite and marked nonequivalence of the parameters of the local environment of the Dy and Hf atoms. It is determined that the ceramic based on dysprosium hafnate (Dy2O3: HfO2 = 1 : 1) possesses low, practically temperature independent (to 800°C), thermal conductivity about 1.4 W/(m · K).

In this paper, we present the results of the study of thermophysical properties of EP-823 steel (thermal diffusivity, thermal coefficient of linear expansion (TCLE), specific heat, thermal conductivity) in the temperature range of 200–900 ◦C. The presence of phase transitions affecting steel thermophysical properties is indicated.

В работе предложена методика определения теплопроводности жидкого свинца импульсным методом, в которой расчеты теплопроводности проводятся по начальному участку термограммы. Приведены результаты измерений теплопроводности жидкого свинца С1 в диапазоне температур 350–1000°С.

We propose a technique for the determination of the thermal conductivity of liquid lead by the flash method where the thermal conductivity is calculated on the basis of the initial section of the temperature-vs.-time profile. We present the results of measurements of thermal conductivity of the liquid C1 lead within the temperature range of 350–1000°C.

The results of the development of the techniques for determining the thermal resistance between a fuel and a fuel-element cladding and the fuel thermal conductivity, oriented to applications under conditions of a shielding box, are described. The schematic of the laboratory setup is presented, using which the operability of the techniques is shown on a fuel element prototype with dense fuel simulators.