Joint Institute for Power and Nuclear Research

For quantitative analysis of X-ray absorption in the range of wavelengths from few to quarter part of angstrom (which approximately correspond to energies from 5 to 50 keV) and X-ray detectors calibration the source of monochromatic radiation is necessary. We present the studies of the monochromator setup constructed for the wide range of energies. The principle of the developed device is based on the X-ray diffraction effect. Pyrolytic graphite single crystal is applied as a diffracting element in the setup. When it is rotated to the assigned angle the monochromatic part is selected from the bremsstrahlung spectrum of the X-ray tube. During the testing procedures it was revealed that the presented system provides a monochromaticity of X-ray beam in the range of energies 15 – 100 keV at level of 1.5 – 9% (suitable for calibration and testing of detectors). It is also shown that available laboratory components applicable for generating tunable monochromatic radiation. The obtained results can be used in defectoscopy, tomography and other tasks which require spectral-selective X-ray analysis.

Results of a kinetic study of the pyrolysis of woody biomass (Quercus robur) under conditions of continuous heating to a temperature of 873 K at a constant rate of 1.25, 2.5, 5, and 10 K/min have been discussed. An integral method has been used to describe the reaction mechanism and determine the macrokinetic parameters. It has been found that, from a phenomenological point of view, the averaged woody biomass pyrolysis reaction under test conditions corresponds to a three-dimensional diffusion model (1.25 K/min), a model described by the third-order reaction equation (2.5, 5 K/min), and a one-dimensional diffusion model (10 K/min). In this case, the relative standard deviation of the conversion values calculated using this equation from the test data is <11.2%. The division of the averaged reaction into three stages (first stage is completed at a temperature of 390 K; the second, at 579 K; the third, at the completion of the conversion process) leads to agreement between the calculated degree of degradation of the studied biomass samples and the test values in a range of the degree of degradation of 0–1. Although the relative standard deviation does not exceed 3.5%, the division of the averaged reaction into stages does not exclude discrepancies in the values of the determined macrokinetic parameters. It has been shown that the choice of the model that provides the best description of the wood conversion process depends on heating rate during the tests. Owing to this dependence, the macrokinetic parameter values significantly differ from each other. Taking this fact into account, it can be concluded that the selected models and calculated macrokinetic parameters are of a formal nature and cannot be thought of as physicochemical characteristics that are universal with respect to the subject of research. Discrepancies in calculations of macrokinetic parameters that are caused by the effect of heating rate can be eliminated by studying the kinetics of conversion under isothermal conditions (at a constant temperature).

To study the wear and friction force of a solid surface during friction with the ground, a carousel-type laboratory stand was created. The main task was to measure friction forces under various parameters of model soil and speeds of relative movement close to real ones during field agricultural work. Traditional electronic dynamometers are designed for static or slowly varying loads. Laboratory stands with such sensors have a linear design, a limited friction path (up to 2 m), and very low relative movement speeds (up to 0.15 m/s). The short friction path complicates the running-in process at the beginning of the experiment. Integral friction forces depend on speed. The adhesion component depends entirely on the presence of soil water at the interface and, thus, on the time required for water to move to the friction surface. With a carousel design of the stand, the friction path is infinite, and the speed can be increased by an order of magnitude (up to 1.5 m/s). Since studies usually compare the influence of different materials or soil compositions on the results of experiments, the systematic error due to the difference in the friction path from a straight line is insignificant. To measure rapidly changing loads, a force measuring station was developed based on a flat spring and a small displacement mechatronic sensor. The advantage of mechatronic linear displacement sensors is high sensitivity, ease of switching on, and high reliability. Disadvantages include dependence on temperature conditions and consequently the need for calibration in each experiment.

Using a methodical approach to the potential biological hazard (radiotoxicity) assessment of radionuclides, computational studies and a comparative analysis of the contributions to the total radiotoxicity of long-lived fission products and actinides accumulated in the nuclear fuel cycle of the Belarusian NPP were carried out. In order to estimate correctly the 237Np isotope mass at the long-term stage of SNF management, the mathematical model of the nuclear fuel cycle of the Belarusian NPP of the code CUB was modified to take into account the transmutation chain of 241Pu, 241Am and 237Np isotopes. The initial concentrations for the main radiation-hazardous radionuclides at the time of fuel unloading from the VVER1200 reactor core are presented in the database “Radiation Characteristics of Spent Nuclear Fuel of the Belarusian NPP” developed by the authors. The database development is carried out in accordance with the recommendations of the RB-093-20 “Radiation and thermophysical characteristics of spent nuclear fuel of pressurized water power reactors and high-power channel reactors”. The main characteristics used in the nuclear fuel cycle simulation in the CUB code, such as the total mass of spent nuclear fuel (2492 tons), the number of spent fuel assemblies (5294) and the average burnup, are taken in accordance with the Spent Fuel Management Strategy of the Belarusian NPP data. It is shown that at the stage up to 100 years, the main contributors to the total radiotoxicity are the isotopes of 238Pu, 239Pu, 240Pu, 243Am, 241Pu, 241Am, 237Np, where contributions of three last of them are 0.07, 49.0 and 0.007%, respectively. But 5000 years later, the contribution of 241Am will be 0.24%, and the isotope 237Np – up to 0.1% of the total actinides radiotoxicity. The results obtained can be used to substantiate for the recovery degree requirements of 237Np, 241Pu, 241Am during the SNF of the Belarusian NPP reprocessing.

The transition from conventional uranium to regenerated fuel, which uses reprocessed spent fuel and enriched natural uranium, improves fuel efficiency and reduces the amount of spent nuclear fuel (SNF). Based on the analysis of published materials concerning mainly the fuel cycles of the VVER-1000 reactor, it was concluded that the most suitable in the conditions of the Republic of Belarus is the use of REMIX fuel. To confirm this conclusion in relation to the VVER-1200 reactors of the Belarusian NPP, computational studies were carried out within the framework of the State program “Scienceintensive technologies and equipment” for 2021–2025, subprogram 3 “Scientific support for the effective and safe operation of the Belarusian nuclear power plant and promising directions for the development of nuclear energy”. The characteristics of a 12-month fuel cycle with multiple recycling (reuse of fuel) according to the REMIX technology with 19.75 % enrichment of added uranium and maintaining the design capacity and duration of the campaign have been obtained. The share of SNF that is not returned to the reactor is 12.8 % (for a cycle with uranium fuel – 100 %); the fraction of waste intended for disposal or long-term storage, respectively, decreases by 8 times, and the specific consumption of natural uranium is reduced from 202 g/(MW·day) for uranium fuel to 159 g/(MW·day) for REMIX fuel. The results obtained can be taken into account when developing a fuel use strategy at the Belarusian NPP.

The goal of this work is to simulate the processes of transport and deposition of aerosol particles in a turbulent flow, taking into account the infrastructure of the industrial site of the NPP. The developed model for calculating the dynamics of the spread of the pollutant emissions in emergency situations is presented, the limits of applicability of turbulence models are determined and the main mechanical and thermal sources of turbulence in the NPP infrastructure are analyzed. The mechanisms of radioactive substances deposition for emergency situations have been assessed taking into account turbulent effects. According to the results of the numerical modeling, the zones of predominant deposition of radioactive aerosols on the characteristic surfaces of the NPP infrastructure have been determined, which is the basis for emergency actions planning and assessment of the personnel doses.

The article presents the analysis of the specific features of modeling the operation of energy systems with a large share of nuclear power plants (NPP). The study of operating conditions and characteristics of different power units showed that a power engineering system with a large share of NPP and CHPP requires more detailed modeling of operating modes of generating equipment. Besides, with an increase in the share of installations using renewable energy sources, these requirements are becoming tougher. A review of the literature revealed that most often the curve of the load duration and its distribution between blocks are used for modeling energy systems. However, since this method does not reflect a chronological sequence, it can only be used if there are no difficulties with ensuring power balance. Along with this, when the share of CHP and nuclear power plants is high, to maintain a balance of power one must know the parameters and a set of powered equipment not only currently but, also, in the previous period. But this is impossible if a curve of load duration is used. For modeling, it is necessary to use an hourly load curve and to calculate the state of the energy system for each subsequent hour in chronological order. In the course of a comparative analysis of available computer programs, it was not possible to identify a suitable model among the existing ones. The article presents a mathematical model developed by the authors, which makes us possible to simulate the operation of a power engineering system with a large share of NPP and CHPP while maintaining the power balance for each hour of the forecast period. Verification of the proposed model showed good accuracy of the methods used.

Mineral composition, physicochemical properties and sorption characteristics of clay-salt slimes (CSS), wastes formed in processing of the sylvinite ore at JSC “Belaruskali” (Soligorsk, Belarus) and aluminosilicate and illite sorbents produced on their basis were studied. It was shown that dressing of CSS samples results in that their chemical and mineralogical compositions change. It was found that the washing of CSS with water, followed by treatment with hydrochloric acid and Trilon B, leads to a 1.2–1.3 times increase in the content of the main component of CSS, illite, due to the dissolution of carbonates (dolomite and calcite) and gypsum. It was found that presence of illite plays a key role in the sorption activity of the sorbents toward the radionuclides 137Cs and 90Sr. With enriched samples of illite sorbents (IS-3o and IS-3m),the distribution coefficients of 137Cs become twice larger, and those of 90Sr, 20 times larger in comparison with the undressed samples of aluminosilicate sorbents (AS-3o and AS-3m). It is shown that the production of aluminosilicate and illite sorbents from CSS and the use of these sorbents for purification of liquid radioactive wastes to remove the radionuclides 137Cs and 90Sr and for creating barriers providing the safe storage and burial of low- and medium-activity of radioactive wastes are promising.

Clay-salt slimes, production wastes from “Belaruskali” (A Belarusian factory, producing potash fertilizers), have been tested as a low-cost, eco-friendly potential sorbent for the removal of radionuclides from aqueous solutions, and may be a component of the cement filling of drums used in the storage of radioactive wastes. The efficiency of sorptive removal of caesium(I)-137, strontium(II)-90, europium(III)-152, and americium(III)-241 was examined with respect to the time of phase equilibration, pH, sorbent dosage, and the presence of salts and complexing agents. Irradiation stability of the material was also studied. It was found that uptake of the radionuclides is almost complete. A procedure for the removal of technetium-99 has been also proposed. Experimental results obtained within the presented work confirm our expectations.

Due to the effective development of ion-track technology, it became possible to produce porous templates with large areas, which are of interest for mass production of nanostructures. Given that the template parameters often define properties of the resulting nanostructures and nanosystems, a reliable method for non-destructive testing is needed for a rapid control of template parameters. Such method could be ellipsometry, allowing for a single measurement to collect statistical information from a large area and to save time for certification. In order to adapt the ellipsometry method for controlling the parameters of ion-track patterns, the first studies of SiO2/Si templates with low porosity were carried out. Using the standard model of the interaction of a polarized light beam with a layered structure of silicon oxide on silicon, the basic parameters of the pores were determined by means of mathematical transformations and subsequently compared with the results of scanning electron microscopy.