Vol 125, No 3 (2019)

The factors that can promote stable development of sodium-cooled fast reactors with mixed uranium and plutonium fuel under conditions of variable demand for atomic energy, types and magnitude of NFC services in the domestic and foreign markets are examined. The possibility of effective control of the balance of plutonium in a two-component nuclear power system with possible change in the demand for electricity and nuclear fuel of reactors built at home and abroad is shown for the example of an analysis of variants for managing fuel in an industrial power-fuel complex with BN-1200 (PEK-BN). It is noted that high-quality plutonium, which can be produced in PEK-BN, for repeated recycling in the VVER system with uranium and mixed uranium plutonium fuel, plays a fundamental role, and promising directions for expanding the fuel business of the State Corporation Rosatom by providing new types of services on the domestic and foreign markets are noted.

Devices for measuring (calculating) the reactivity of a nuclear reactor using information from ionization chambers must be checked periodically, just as any other measuring apparatus. This is associated with the fact that under the influence of external factors (temperature, humidity, pressure, vibrations, control regimes) the working characteristics of such apparatus, just as any technical object, change in the course of operation and in time the apparatus becomes unserviceable. In order to determine the serviceability of the checked working reactivity meters, it is necessary to have a standard signal and, correspondingly, a standard apparatus. The present article proposes an approach to solving this problem on the basis of the equivalent model method.

The basic results of computational and experimental studies of passive systems of emergency heat removal in application to ship and portable reactor facilities are presented. The methodological correlations for calculations of heat removal systems with condensation of steam in a bundle of inclined tubes under mixed convection conditions in the presence of non-condensing gases and the true volume steam content in a vertical large-diameter tube are developed. The optimization of the cooling loops of systems performing emergency heat removal at pressure close to atmospheric and suggestions for improving a passive system of emergency heat removal from a reactor are discussed.

Scenarios of the mass transfer of boric acid during an accident with rupture of the primary circulation pipeline and reactors equipped with passive safety systems are examined. The results of an approximate calculation of the change in the concentration of boric acid in the core during emergency regimes in VVERTOI are presented. A review of the data on the thermophysical properties of boric acid with different concentration is presented. It is shown that the data are inadequate for full-value calculation of the processes occurring in a VVER core during an accident. The need for experimental studies of the film of physical properties of boric acid in a wider concentration range is substantiated. The parameters for which these studies must be performed are determined, and methods of performing them are formulated.

The results of an investigation of the stored energy in GR-280 graphite irradiated at 560°C to neutron fluence ~3·10²⁶ m^–2 are presented. The measurements were performed by means of differential scanning calorimetry with constant heating rate 20°C/min. The release of the stored energy reaches a maximum at annealing temperature 1100°C. The maximum output is equal to 0.34–0.48 J/(g·°C). The total stored energy released in the annealing temperature range 560–1300°C does not exceed 183 J/g. A kinetic analysis of the spectrum of the stored energy was performed. This analysis established that increasing the radiation temperature from 450 to 560°C results in almost complete vanishing of individual vacancies, redistribution of the migration of di-vacancies, and evolution of a cluster structure upon post-radiation annealing in the range 560–1300°C in the direction of processes with lower activation energy.