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Lead-based reactor coolant has high thermal conductivity, good thermal expansion and strong natural circulation ability, which has outstanding advantages in safety, economy and miniaturization. At the same time, lead-bismuth reactors have potential applications in small nuclear power sources, marine reactors and so on. Difference from land-based nuclear power plants, marine nuclear power plants will produce swaying, heaving, tilting and other movements due to their long-term operation in the ocean environment. In order to study the thermal-hydraulic characteristics of the lead-bismuth reactor system under marine conditions, an experimental study was conducted by building a lead-bismuth experimental circuit based on a heaving motion platform. Under the influence of heaving motion, the flow rate of lead-bismuth circuit fluctuates and the flow resistance and heat transfer characteristics change. In this paper, the flow resistance and heat transfer characteristics of liquid lead-bismuth eutectic in a vertical circular tube under forced circulation under heaving conditions are investigated experimentally. The range of Reynolds number (Re) in the flow resistance experiment is 23 500-261 280, and the range of Peclet number (Pe) in the flow heat transfer experiment is 524.4 450. The results show that: The peak value of instantaneous additional pressure drop caused by heaving motion is lower than the theoretical value; The heaving motion causes periodic fluctuations in the flow rate of the circuit, and the maximum fluctuation is up to 16% in the low Re region; In the low Re region, the heaving condition makes the time-averaged frictional resistance coefficient of the pipe increase slightly; The relationship between the fluctuation of loop flow caused by undulating motion and the undulating acceleration and Re was obtained by fitting, which is in good agreement with the experimental results. This method can be used to predict the fluctuation of flow rate in the reactor at different coolant flow rates by heaving motion. In the scope of this experimental working condition, although the fluctuation causes the fluctuation of the flow rate, the instantaneous temperature difference between the inlet and outlet of the experimental section and the instantaneous heat transfer coefficient h of the experimental section do not fluctuate significantly, and the fluctuation has little impact on the instantaneous heat transfer characteristics. In the forced circulation, the heaving motion does not affect the heat transfer characteristics of the circuit. The results of this study can provide data reference for the engineering design of lead-bismuth reactor.

Lead-cooled fast reactor (LFR) is known as a typical reliable new type reactor by the US Department of Energy (DOE), and the potential accidents of LFR are necessary to assess. Steam generator tube rupture (SGTR) accident can cause high-pressure hyperbaric steam-water jetting into liquid lead bismuth eutectic (LBE) pool, and leads to a rapid pressure rising in the reactor primary system together with a potential pressure wave crashing the structures. This paper focuses on the computational fluid dynamics (CFD) analyses of SGTR experimental research on the LIFUS5/MOD2 experiment facility. A two-dimensional symmetrical slice with 1 million 570 thousand structured mesh was established for the experimental reaction vessel, and each side except the injection nozzle were set as adiabatic no slip boundary in order to achieve the non-decompression process. In the aspect of multiphase model settings, the Eulerian-Eulerian two-phase flow model was adopted to track the steam-LBE interface in the transient simulation, and the CSF surface tension polynomial together with Lee substituted evaporation model were considered. In addition, the injection of high-pressure water in each time step was separated to two parts: latent heat and injected steam, so as to calculate both endothermic and jet of flash evaporation simultaneously. Among them, the latent heat was realized by user-defined functions (UDF), and the injected steam was adopted as compressible real gas with R-K gas state equation. Based on the above settings, three established thermal-hydraulics phenomena including pressure rising of LBE environment together with pressure wave spreading, level fluctuation of liquid environment with argon entrainment and level rising of liquid environment and diffusion of injected steam were analyzed. From the results a conclusion can be reached that CFD numerical simulation has little error on calculating pressure rising with pressure wave spreading. In addition, the peak value of pressure wave rises with back pressure of water increasing, and the pressure of partial steam cavity is lower than that of LBE pool around it, in turn inhibits the occurrence of its explosion. Meanwhile, LBE in the middle firstly washes up and impacts the structures, and then entrains the argon when it falls back, in turn causes the combination of argon and steam cavity, or the secondary segmentation to small argon bubbles. Moreover, the diffusion of the steam cavity along the radial direction becomes more intense with the increase of the axial height, accompanies by the steam cavity divided from the center to the edge along the radius.

This study introduces the low‐volume core (LVC) fabrication method, which enables the monolithic molding of compact, complex, versatile, and intelligent soft robotic systems. This method uses thin and flexible thermoplastic sheets to mold internal chambers in soft fluidic actuators, valves, and circuits. The LVC fabrication method creates low‐volume networks in soft actuators (LV‐net actuators) that can be made with compact and complex geometries, enabling both low actuation volume input and multi‐degree‐of‐freedom actuators. LVC fabrication can also be used for compact, completely soft, and monolithic logic components (valves with low‐volume core, also called as LV valves) to provide directional resistance as well as a switching mechanism that enables fluidic logic in soft systems. The compatibility of the fabrication methods for both soft actuators and valves facilitates the creation of compact, integrated, and versatile soft robotic systems with embodied intelligence. This study introduces two examples of such intelligent soft robotic systems that integrate both LV‐net actuators and LV valves to demonstrate capability for complex system fabrication. [ABSTRACT FROM AUTHOR]

The regeneration mechanism of sulfated Cu/SAPO-34 catalysts in reducing atmospheres (5% H2/Ar and NH3/Ar at 600 °C) was investigated by using a series of characterization methods. Hydrogen regeneration improved the catalysts' NH3-SCR activity from 150 to 550 °C remarkably, while ammonia regeneration exhibited relatively less obvious promotion effect. The TPR of hydrogen and EPR spectra data show that the regeneration process affects the amount and the coordination of the active isolated Cu2+ species significantly. The desulfation increases the amount of isolated copper ions and improves the catalytic activity of SCR. [ABSTRACT FROM AUTHOR]