Vol 126, No 4 (2019)

The conceptual precepts of a modular fast sodium reactor with mixed uranium-plutonium zirconium-alloy metal fuel (U–Pu–Zr) related to Gen-IV are presented. The range of its parameters is determined, and the parameters are optimized in order to meet the characteristic requirements of the development of a nuclear power system in terms of safety, competitiveness, and resource availability. It was shown with the aid of computational studies that in a modular reactor, in spite of its small size, the systems requirements in terms of specific load and excess production are met and the minimum reactivity excess on burnup is realized. Loading metallic fuel into the core and thorium into the breeding zone and using fuel cycles compatible with thermal reactors it becomes much easier to solve the problems of supplying fuel for nuclear power and managing actinides and plutonium in the nuclear fuel cycle.

The possibility of purifying the metalized products of pyrochemical operations by removing the electrolyte by distilling off lithium chloride is checked experimentally. This study is performed in connection with the development of promising variants of an industrial method of metalizing uranium dioxide, which is the main component of the spent nuclear fuel after its voloxidation. The electrolyte was distilled from metalized pellets and powders based on uranium dioxide with their continuous evacuation at 700–900°C. It was found that the main component of the sublimates is lithium chloride; the content of rare-earth elements and uranium is very low. The distillation regimes where 98.8–99.9% of the LiCl can be removed from the metalized products were determined.

The results of studies of agitation leaching in combination with sorption leaching of uranium for different types of ores are reported. Sorption leaching reduces the consumption of sulfuric acid by 7–8% and reduces the processing time and makes it possible to obtain dump cakes with uranium content 0.005–0.007% and uranium concentration ≤5 mg/dm³ in the liquid phase of the discharge pulp, which corresponds to technological extraction of the uranium into anionite of at least 97%. The combined variant will make the fullest use of the capacity and potential of ion-exchange materials and permit unification of the enterprise’s process scheme.

The concept of a solution target for obtaining the radioisotope ⁸²Sr via the reaction Rb(p, xn)⁸²Sr is propounded. A computational estimate of the main technological parameters of a solution target is made. The ⁸²Sr yield in a solution target is calculated for solutions of certain compounds of rubidium and initial proton energy 70 MeV. It is shown that the highest ⁸²Sr yield 7.44 MBq/(μA·h) in a solution target can be obtained by using a saturated solution of RbF. The solution fl ow rate in the circulation loop of the target allowing the operation of a target without boiling-up in a 100 μA proton beam is obtained for a target solution with RbF. The mass/size parameters of the heat-exchanger allowing the solution to be cooled tothe initial temperature in a single pass are calculated. The infl uence of radiolysis of the proton-irradiatedsolution on the operation of the target is determined. It is shown that on the whole radiolysis of the solution target is not large but does require defi nite efforts to utilize the hydrogen.

The existence of a system of short-lived, discrete, volume-localized, electronic, quantum levels in positively charged fullerenes is shown theoretically and numerically for the example of the fullerenes C₆₀. The results of three-dimensional calculations performed using the QuantumEspresso package are presented. The structures of the quantum levels in charged fullerenes were calculated numerically in a wide range of transitions from 4 eV for the fullerene \( {C}_{60}^{+ 1} \) to 40 eV for the fullerene \( {C}_{60}^{+ 1} \). The results confirm previous theoretical work on the possible existence of single-particle excited electronic states localized in the volume of positively charged fullerene C₆₀. Thus, the electrons captured in these discrete levels of fullerene form a kind of short-lived superheavy pseudoatom in which the electrons are localized inside a positively charged spherical nucleus with atomic mass 240 a.u. for C₂₀ and 720 a.u. for C₆₀. In conclusion, the possibility of generating coherent radiation on these transitions is discussed.