Fabricating tritium permeation barrier for PFC with a new non-coating strategy

Tritium (T) permeation through plasma-facing component (PFC) into the coolant is a major concern of fusion reactor operation. In this work, deuterium (D) permeation through CLAM steel, CLAM/CLAM and CLAM/Fe-Cr-Al samples prepared by hot isostatic pressing (HIP) are tested in a linear plasma device. Only the downstream surfaces of the samples are oxidized with controlled atmosphere to form permeation barrier. No significant effect on D diffusion and penetration can be observed for the joining interfaces, while the dense oxide layer at the downstream side plays an important role in suppressing D permeation. The downstream surface oxidization of CLAM/Fe-Cr-Al is found to effectively reduce D permeation flux by a factor up to 1000.

Substantiation of parameters for the inertial mixer in a biodiesel production reactor

This paper reports results of the theoretical and experimental studies into the processes of transesterification of oils with methyl alcohol, which determined the material balance and established the molecular weight of the components involved in the process of transesterification as input and output products. The theoretical and experimental studies were carried out to calculate the indicators of the process of transesterification of fat-containing wastes depending on a change in the reaction duration and diameter of the inertial mixer of the reactor to accelerate the process of transesterification of oils with methyl alcohol. The process of transesterification is one of the basic methods for modifying the molecular composition of fat raw materials. With transesterification, the composition of fat fatty acids does not change, their statistical redistribution occurs in a mixture of triacylglycerols, which leads to a change in the physicochemical properties of fat mixtures as a result of changes in molecular composition. Transesterification of high-melting animal and vegetable fats with methyl alcohol improves the conversion of oils for the production of biodiesel from fat-containing waste. The results of the theoretical and experimental studies have helped determine the value of the flow rate of the reaction mixture, as well as the values of the geometric dimensions of the reactor, were determined (the diameter of the mixer, d=100÷500 mm; the length of the reactor is 1.5÷2.0 m). Processing of the reaction mixture made it possible to obtain a high degree of homogeneity in the concentration of components with large diameters of the inertial mixer ‒ 300...500 mm at average rotational speeds. The oil conversion has been improved, as well as productivity, by using equipment to produce biodiesel from fat-containing waste. Optimal pump performance is also ensured with minimal power consumption and reactor operation

Characteristics of Biogas Production from Organic Wastes Mixed at Optimal Ratios in an Anaerobic Co-Digestion Reactor

This study determined the optimal mixing ratio of food waste and livestock manure for efficient co-digestion of sewage sludge by applying the biochemical methane potential (BMP) test, Design Expert software, and continuous reactor operation. The BMP test of sewage sludge revealed a maximum methane yield of 334 mL CH4/g volatile solids (VS) at an organic loading rate (OLR) of 4 kg VS/(m3·d). For food waste, the maximum methane yield was 573 mL CH4/g VS at an OLR of 6 kg VS/(m3·d). Livestock manure showed the lowest methane yield. The BMP tests with various mixing ratios confirmed that a higher mixing ratio of food waste resulted in a higher methane yield, which showed improved biodegradability and an improved VS removal rate. The optimal mixing ratio of 2:1:1 for sewage sludge, food waste, and livestock manure was determined using Design Expert 10. Using continuous co-digestion reactor operation under an optimal mixing ratio, greater organic matter removal and methane yield was possible. The process stability of co-digestion of optimally mixed substrate was improved compared with that of operations with each substrate alone. Therefore, co-digestion could properly maintain the balance of each stage of anaerobic digestion reactions by complementing the characteristics of each substrate under a higher OLR.

Cross Section and Fission Yields Induced Uncertainty in the Vver-440 Burnup Calculation

The properties of nuclear fuel depend on the actual isotopic composition which develops during a reactor operation. In practice, the prediction accuracy of burnup calculations serves as the basis for the future precise estimation of a core lifetime and other safety-based core characteristics. The present study quantifies nuclear data induced uncertainties of nuclide concentrations and multiplication factors in VVER-440 fuel depletion analysis. The well-known SCALE system and the TRITON sequence are used with the NEWT deterministic solver in the SAMPLER module that implements stochastic techniques to assess the uncertainty in computed results. The propagation of uncertainties in neutron cross section and fission yields is studied through the depletion calculation of 2D heterogeneous VVER-440 fuel assembly with an average enrichment of 4.87 wt % of 235U and six gadolinium rods with 3.35 % of Gd2O3. In the paper, fixed nominal depletion conditions are based on the real operational data of the Slovak NPP Bohunice unit 4 during cycle 30. In total 250 cases with uncertain parameters are computed and the results are evaluated by an auxiliary tool.

Effect of Marine Nuclear Reactor Environment to Ship’s Structural Responses

As the regulations on greenhouse gas emissions at sea become strict, technology development to minimize environmental pollutants emitted from the propulsion system of ships is actively underway. Research on the use of renewable energy as a power source of ships propulsion system pursuing eco-friendliness is continuously carried out. However, considering the recent development of ships’ large-scale, and at the same time minimizing greenhouse gas emissions at sea, the interest in nuclear energy as the means of a stable supply of environmentally friendly large-capacity energy has been increased. In this study, the effect of marine reactor operation on the material properties of a ship hull material is reviewed, and from this, hull structural behaviors are investigated. Attention is paid to the neutron irradiation on the material in the reactor operation environment, and then the strength assessment of a hull structural member assumed in the neutron irradiation situation is performed. Considering the neutron irradiation effects, the Young’s modulus, poisson’s ratio and allowable stress of DH36, typical high tensile strength steel used in ship hull, are varied based on the research findings related with the topic of neutron irradiated steels. Rectangular stiffened plated structures, basic common structural members for ship hull, are exemplified for the strength assessment to understand their structural behaviors such as strength and stiffness. Results from this study provide information on the effect of neutron irradiation on the hull structural behaviors of the ship using nuclear power and possibly can supplement the hull structure part from classification societies’ rules and regulations.

Short.Term Reactivity Change: Local.Parameter Reactivity Feedback

A change in power for an operating reactor generally alters local parameters in the reactor such as the temperatures of the fuel, moderator, and coolant. A change in any of these local parameters causes a change in reactivity that, in turn, affects reactor operation (a feedback effect). Local parameters help to understand the feedback reactivity components related to the core evolution. For the CANDU reactor, the most important local parameters are the following: