Liquid “Syngas” Based on Supercritical Water and Graphite Oxide/TiO2 Composite as Catalyst for CO2 to Organic Conversion

The conversion of carbon monoxide into organic substances is one of the top topics of modern science due to the development of industry and the climate changes caused by it on the one hand, and the possibility of obtaining an economic effect on the other, as it could allow for partial recovery of fuels. A problem in this regard has always been the low solubility of CO2 in water, which eliminated the possibility of easy converting carbon dioxide into the liquid. The development of research on water critical states revealed the fact that water in a subcritical state has a much higher ability to dissolve gases. And this effect was used to obtain the "liquid synthesis gas" model presented in this paper. Equally important was the selection of an appropriate catalyst that would increase the efficiency of the conversion process by generating hydrogen in the system under the influence of cold plasma. In this work we present the studies of transformation of CO2 dissolved in supercritical water using partially reduced graphite oxide—nanometric titania composite (RGO-TiO2) as catalyst, due to the ability of RGO to generate hydrogen in the water environment (water splitting) under the influence of various physical factors, especially cold plasma. The RGO catalyst was stabilized with titanium oxide to obtain higher activity at lower RGO concentrations in the system. Therefore, research on conversions was preceded by a thorough analysis of CO2 solubility in supercritical water, as well as an analysis of the structural, morphological, and spectroscopic properties of the catalyst. Graphic Abstract General scheme of cold plasma reactor.

On the determination of neutron multiplication by the Rossi-alpha method

Introduction. This work contains the results of determining the prompt neutron multiplication factor in the subcritical state of a one-core BFS facility, obtained by the neutron coincidence method, for which the influence of the error in the βeff in determining the multiplication factor turned out to be insignificant. The core of the facility consisted of rods filled with pellets of metallic depleted uranium, 37% enriched uranium dioxide and 95% enriched plutonium, sodium, stainless steel and Al2O3. Stainless steel served as a reflector. Methods. In contrast to the inverse kinetics equation solving (IKES) method, which is convenient for determining reactor subcritical states, the neutron coincidence method practically does not depend on the error in the value of the effective fraction of delayed neutrons βeff. If in the IKES method the reactivity value is obtained in fractions of βeff, i.e., from the measurement of delayed neutrons, the neutron coincidence method is based on the direct measurement of the value (1 – kσp)2, where is the effective multiplication factor by prompt neutrons. The total multiplication factor is defined as keff = kσp + βeff. If, for example, keff ≈ 0.9 (which is typical for determining the fuel burnup campaign), then it is the error in determining kσp that is the main one in comparison with the error in βeff. Thus, a 10% error in βeff of 0.003–0.004 (typical for plutonium breeders) will make a contribution to the error 1 – keff equal to 1 – kσp + βeff ≈ 0.00035, i.e., approximately 0.35%, but not 10%, as in the IKES method. Rossi-alpha measurements were carried out using two 3He counters and a time analyzer. The measurement channel width Δt was 1.0 μs. From these measurements, the value of the prompt neutron multiplication factor was obtained. In this case, the space-isotope correlation factor for the medium with a source was calculated using the following values: Φ(x) – solutions of the inhomogeneous equation for the neutron flux and Φ+(x) – solutions of the ajoint inhomogeneous equation. Results. The authors also present a comparison of the results of the Rossi-alpha experiment and measurements of the BFS-73 subcritical facility by the standard IKES method in determining the multiplication factor value. The data of the IKES method differ insignificantly from the results of the Rossi-alpha method over the entire range of changes in the subcriticality with an increase in the subcriticality of the BFS-73 one-core facility. Conclusion. It was impossible to apply the neutron coincidence method to fast reactors; however, the method turned out to be quite workable on their models created at the BFS facility, which was successfully demonstrated in this study.

Non-Hydrostatic Transitional Open-Channel Flows from a Supercritical to a Subcritical State

In this study, a depth-averaged numerical model was employed to investigate the two-dimensional flow features of transitional open-channel flows from a supercritical to a subcritical state. Compared to a shallow-water model, the proposed model incorporates supplementary terms to account for the effects of non-uniform velocity and non-hydrostatic pressure distributions. The model equation was solved numerically by means of the Adams–Bashforth–Moulton scheme. A wide variety of transitional open-channel flow problems such as hydraulic jumps was considered for assessing the suitability of the numerical model. The results of the model for the free-surface profile, pressure distribution, and characteristics of the first wave of an undular jump were compared with the experimental data, and the agreement was found to be satisfactory. Despite the effects of the three-dimensional characteristics of the flow and the bulking of the flow caused by air entrainment, the model performed reasonably well with respect to the simulations of the mean flow characteristics of the curvilinear turbulent flow problems. Furthermore, the results of this investigation confirmed that the model is more suitable for analyzing near-critical turbulent flow problems without cross-channel shock waves.

The influence of dielectric permittivity of water on the shape of PtNPs synthesized in high-pressure high-temperature microwave reactor

In this paper, a novel method for the synthesis of Pt nanoparticles (PtNPs) using a microwave autoclave reactor is proposed. For benchmarking, the obtained results are compared with the traditional, batch method. A novel process window is proposed, which is the application of high-temperature and high-pressure. The main finding is that this only brings advantage, when the ionic strength of the system is enough low. It is explained, that at high pressure and high temperature, water behaves like only a slightly polar solvent, approaching a subcritical state. This reduces the electrostatic stabilization of the particles. Moreover, a change in the Pt particle shape is observed under high pressure and temperature conditions, suggesting that additional physical–chemical processes are involved.

Subcriticality

For a subcritical reactor system driven by a periodically pulsed spallation neutron source in KUCA, the Feynman-α and the Rossi-α neutron correlation analyses are conducted to determine the prompt neutron decay constant and quantitatively to confirm a non-Poisson character of the neutron source. The decay constant determined from the present Feynman-α analysis well agrees with that from a previous analysis for the same subcritical system driven by an inherent source. Considering the effect of a higher mode excited, the disagreement can be successfully resolved. The power spectral analysis on frequency domain is also carried out. Not only the cross-power but also the auto-power spectral density have a considerable correlated component even at a deeply subcritical state, where no correlated component could be previously observed under a 14 MeV neutron source. The indicator of the non-Poisson character of the present spallation source can be obtained from the spectral analysis and is consistent with that from the Rossi-α analysis. An experimental technique based on an accelerator-beam trip or restart operation is proposed to determine the subcritical reactivity of ADS. Applying the least-squares inverse kinetics method to the data analysis, the subcriticality can be inferred from time-sequence neutron count data after these operations.

Nuclear Transmutation of Minor Actinide

Integral experiments on critical irradiation of neuptium-237 (237Np) and americium-241 (241Am) foils are carried out in a hard spectrum core at KUCA with the use of the back-to-back fission chamber, and Monte Carlo calculations together with a reference nuclear data library are conducted for confirming the precision of numerical simulations. Subcritical irradiation of minor actinide (MA) by ADS is a very important step, before operating actual ADS facilities, in a critical assembly at zero power, such as KUCA, which is an exclusive facility for ADS that comprises a uranium-235 (235U) fueled core and a 100 MeV proton accelerator. The first significant attempt is made to demonstrate the principle of nuclear transmutation of MA by ADS through the injection of high-energy neutrons into the KUCA core at a subcritical state. Here, the main targets of nuclear transmutation of MA by the ADS experiments are fission reactions of 237Np and 241Am, and capture reactions of 237Np.

Experimental Investigation of the Anomalously Low Friction Phenomena in Blocky Rock Systems

Rock masses can be regarded as a blocky rock system. After a disturbance load is applied, the anomalously low friction phenomenon may take place and cause geological disasters. A series of impact experiments on granite blocks were conducted to investigate the anomalously low friction phenomena. Vertical vibration, Fourier frequency spectrum, and horizontal motions were investigated. It can be found that the tensile phases of vertical vibration can reduce the maximum static friction force, namely, the shear strength. The quasi-resonance operating mode of the rock blocks was observed. During the stress wave propagation, the vibration in the loading direction tends to transfer from high frequency to low frequency and the modes of stress wave propagation do not depend on disturbance energies. The observed translational and rotational motions were due to the initial shear force, which is less than the friction force with no disturbance load. Stability of the blocky rock system is very sensitive to the initial stress state. In the subcritical state, friction force reduction can easily break the equilibrium of forces along the contact surface and even a slight disturbance may make the horizontal motions happen, which may lead to geological disasters with great energy release.

Review of results of experimental studies of neutronic properties of fast-neutron thermionic converter-reactors

The paper provides an analytical review of published works on experimental, and, in part, analytical and theoretical studies of neutronic properties of critical assemblies, simulating geometry and materials composition of fast-neutron Thermionic Converter-Reactors (TCR). It provides results of studies of radial distribution of energy release with absorbing and fissile shields placed at the boundary of the active zone with side reflector, results of equalization of radial energy release and suppression of the local surge of energy release in fuel kernels of peripheral Electric generating Assemblies-Channels (EAC). It provides results of experimental measurements of the microstructure of energy release in the fuel kernels cross-section. It provides an analysis of the results of experiments and efficiency calculations for the side reflector with actuating elements of the Control and Safety System (CSS). It is demonstrated that insertion of twelve actuating elements of CSS into the reactor places it into a deeply subcritical state. An order of magnitude reduction of the modular TCR assembly, as compared with the conventional configuration assembled from individual EACs, was experimentally demonstrated. The paper provides results of experiments on a critical assembly simulating TCR with homogenous (non-modular) structure of the active zone. It provides results of experimental neutronic studies of operating conditions for combined-excitation lasers within fast-neutron TCR with moderating reflector. Key words: thermionic reactor, neutronic characteristics, energy release distribution, absorption and fissile shields, actuating elements of CSS, modular assembly, combined excitation lasers.

IMPROVING THE TECHNOLOGY OF SOFT DRINKS BASED ON CO2-MEAL OF FRUIT AND BERRYCROPS AND THICK EXTRACTS OF MEDICINAL PLANTS FOR THE POPULATION OF THE NORTHERN REGIONS OF RUSSIA

Усовершенствована технология безалкогольных напитков на основе СО2-шротов плодово-ягодных культур и густых экстрактов лекарственных растений для целевого потребления их в северных районах России. Для производства напитков выбраны СО2-шроты, полученные из плодово-ягодного сырья, выращенного на территории Краснодарского края: СО2-шроты шиповника, смородины черной, облепихи, малины обыкновенной. Плодово-ягодное сырье было однократно обработано жидким диоксидом углерода в докритическом состоянии (параметры экстракции: давление 6,0 МПа, температура 22°С). Для приготовления густых экстрактов использовали лекарственное растительное сырье: эхинацею пурпурную, душицу обыкновенную и ромашку аптечную. Полученные очищенные вытяжки растений подвергали сгущению до получения вязкой массы с содержанием влаги 20–25%. Разработанные безалкогольные напитки являются источником широкого спектра биологически активных веществ, в том числе витамина С. Основные нормируемые физико-химические показатели разработанных безалкогольных напитков соответствуют требованиям нормативной документации: содержание сухих веществ составляет 9–10%, массовая доля витамина С – 12,9–17,6 мг/100 мл, энергетическая ценность – 246–253 ккал, кислотность – 6,3 –11,2 см3. Биотест на определение жизнеспособности культуры Paramecia caudatum подтвердил безвредность разработанных напитков. Микробиологические и токсикологические показатели напитков не превышают допустимых уровней. The technology of soft drinks based on CO2-meal of fruit and berry crops and thick extracts of medicinal plants for their intended consumption in the Northern regions of Russia has been improved. CO2-meal obtained from fruit and berry raw materials grown on the territory of the Krasnodar region – such as rosehip, black currant, sea buckthorn, and raspberry, are selected for the production of beverages. Fruit and berry raw materials were once treated with liquid carbon dioxide in a subcritical state (extraction parameters: pressure 6,0 MPa, temperature 22°C). Echinacea purpurea, oregano, and chamomile are used for the preparation of thick extracts. The resulting purified extracts of plants were subjected to thickening to obtain a viscous mass with a moisture content of 20–25%. Developed soft drinks are a source of a wide range of biologically active substances, including vitamin C. The main normalized physical and chemical parameters of the developed soft drinks meet the requirements of regulatory documentation: the dry matter content is 9–10%, the mass fraction of vitamin C is 12,9–17,6 mg/100 ml, the energy value is 246–253 kcal, the acidity is 6,3–11,2 cm3. A biotest to determine the viability of Paramecium caudatum culture confirmed the harmlessness of the developed beverages. Microbiological and toxicological indicators of beverages do not exceed acceptable levels.