Alexander Gennadievich Korotkikh

An analytical method was developed to predict the thermal parameters of the VVER-1200 pressurized water reactor (PWR). The peak temperatures of the fuel, outer fuel surface temperature, inner cladding surface temperature, outer cladding surface temperature, and coolant temperature were evaluated along and across the fuel rod, assuming that the hottest fuel rod is located at the reactor core center. This method analyzed the steady-state temperature distributions and was validated against a corresponding steady-state and time-dependent COMSOL Multiphysics model. Additionally, validation was conducted using the VVER-1200 PCtran Simulator for peak fuel temperature and the departure from nucleate boiling ratio (DNBR). The analytical method was employed to increase the reactor’s rated power from 100% to approximately 106% to assess the peak fuel temperature and the minimum departure from nucleate boiling ratio (MDNBR), both of which are crucial safety parameters for the operation of the VVER-1200. Given that the VVER-1200 initiates a scram slightly above 106% rated power, we evaluated the peak fuel temperature and DNBR at 100%, 102%, 104%, and 106% rated powers to determine the safety limits for both peak fuel temperature and MDNBR. The results from both the analytical method and simulations were found to be comparable.

Metal and metalloid powders are widely used in high-energy compositions (HECs) and solid propellants (SPs), increasing their energetic characteristics in the combustion chamber. The particle size distribution, protective coatings of the particles and heat of combustion of the metal powders influence the ignition and combustion parameters of the HECs as well as the characteristics of the propulsion systems. Boron-based metallic fuels achieve high-energy potentials during their combustion. The effect of Al-B, Fe-B and Ti-B (Me-B) mixture ultrafine powders (UFPs) on the ignition and combustion characteristics of a model HEC based on a solid oxidizer and a polymer combustible binder was investigated. The Me-B mass ratios in the mixture UFPs corresponded to the phase composition of the borides AlB2, FeB and TiB2. It was found that replacing the aluminum UFP with Al-B, Fe-B and Ti-B UFPs in the HECs changed the exponent (n) in the correlations of the ignition delay time tign(q) and burning rate u(p). The maximum burning rate and n over the pressure range of 0.5–5.0 MPa were obtained for the HEC with Al-B UFPs due to the increase in the heat release rate near the sample surface during the joint combustion of the Al and B particles.

Prediction of critical heat flux using empirical correlations for circular tubes modified for rod bundles with correction factors, is one of established method of critical heat flux evaluation. In this work, an analysis of the thermal-hydraulics of VVER heated core was carried out. A geometrical and thermal analysis of the heated core, including the analysis of the flow rate and mass flux for the assemblies with hot water, analysis of heat transfer densities of the hottest part of the core and proper thermo-fluid analysis of the coolant parameters such as enthalpy, temperature and steam equilibrium quality were carried out. The thermal hydraulic analyses were carried out at the pressures, inlet temperatures and thermal powers of 16.2 MPa, 298.2?C, and 3200 MWth, 15.7 MPa, 298.2?C, and 3000 MWth and 12.5 MPa, 262?C, and 1375 MWth to ascertain the axial changes in thermal parameters of the fuel rod. The critical heat flux was predicted using the OKB Gidropress and Levitan-Lantsman critical heat flux correlations for rod bundles under the ranges of parameters suitable for VVER reactor.

This paper describes a study of the ignition and combustion characteristics of a high-energy material containing ammonium perchlorate, butadiene rubber, and an ultrafine powder mixture of aluminum, titanium, or iron with amorphous boron. An experimental stand based on a CO₂ laser and a constant-pressure bomb is used to measure the ignition delay time and burning rate of the high-energy material while varying the heat flux density and the chamber pressure. It is shown that replacing amorphous boron with ultrafine Al/B, Ti/B, or Fe/B in a high-energy material reduces the heating time and the moment at which a flame appears on the propellant surface due to an increase in the reaction rate and a decrease in the oxidation temperature of these mixtures on the surface of the reaction layer. In this case, the burning rate of the high-energy materials with Me/B at excess pressures increases significantly (up to 240% for Al/B-HEM and up to 120% for Ti/B-HEM at a pressure of 5.0 MPa).