Journal of Fusion Energy最新文献

Considering the high energy neutron environment in a nuclear fusion reactor, Reduced Activation type Ferritic/Martensitic Steels (RAFMS) containing tungsten, have been carefully curated from their surrogate Cr–Mo type Ferritic/Martensitic Steels (FMS). The substitution of molybdenum by tungsten improved the radiation stability and mechanical characteristics RAFMS. However, the effect of tungsten on the liquid metal corrosion resistance of FMS has not been well investigated. The current work attempts to estimate liquid metal compatibility by examining the surface oxides of Indian RAFMS (IN RAFMS) and its surrogate steel, P91 (9Cr-1Mo), using X-ray Photoelectron Spectroscopy. Subsequently, thermodynamic calculations have been used to establish the stability of such oxides in both ambient circumstances and liquid lead–lithium eutectic alloy (Pb–Li). The results showed that tungsten can provide a higher resistance to liquid metal attack than molybdenum because its oxides are more stable. Actual corrosion experiments with IN RAFMS and P91 were performed in liquid Pb–Li for a durations upto 2000 h, successfully validating the above stated prediction.

The understanding and control of complex systems in general, and thermonuclear plasmas in particular, require analysis tools, which can detect not the simple correlations but can also provide information about the actual mutual influence between quantities. Indeed, time series, the typical signals collected in many systems, carry more information than can be extracted with simple correlation analysis. The objective of the present work consists of showing how the technology of Time Delay Neural Networks (TDNNs) can extract robust indications about the actual mutual influence between time indexed signals. A series of numerical tests with synthetic data prove the potential of TDNN ensembles to analyse complex nonlinear interactions, including feedback loops. The developed techniques can not only determine the direction of causality between time series but can also quantify the strength of their mutual influences. An important application to thermonuclear fusion, the determination of the additional heating deposition profile, illustrates the capability of the approach to address also spatially distributed problems.

High energy gain is essential for the energy production via laser fusion. In this paper, an efficient method combining the hydrodynamic simulations and the machine learning algorithms is proposed to optimize the laser pulse for fast ignition simulations. An analytical model between the energy gain and compressed plasma parameters is derived as the evaluate function for the optimizations. An implosion with a fusion gain more than 100 is achieved with a total laser energy about 730 kJ in the spherical fast ignition scheme or 300 kJ in the double-cone ignition (DCI) scheme in one-dimensional simulations. The implosion data generated during the course of optimization is found to be suitable for the training of a deep neural network (DNN) surrogate model. In the future, this DNN surrogate model could be transfer learned with experimental feedback and optimize the laser pulse with a higher accuracy.

The microwave window unit is the core component of the electron cyclotron heating and current drive (EC H&CD) system used in fusion reactors. In this work, a diamond disk for the microwave window was designed according to the electromagnetic propagation theory. Then, the finite element method was employed to build a microwave window model based on our tailored dimension. The effect of brazing and subsequent service processes on the stress/strain distributions and electrical parameters were explored. Overall, the microwave window exhibited excellent performance, with the maximum principal stress of the brazed disk under service being 51 MPa, which was much lower than the allowable stress of diamond. It was also indicated that the electrical properties barely changed, which could satisfy functional requirements. This work provided theoretical guidance for the design and manufacture of diamond microwave windows used in fusion reactors.

China fusion engineering test reactor (CFETR) is a magnetic confinement device which will fill the gap between the fusion experimental reactor and the demonstration reactor. To efficiently conduct neutronics modeling for the multiple identical and similar structures present in CFETR’s modular design, an improved one-to-many method is developed and implemented in this study. This method involves using a basic model in conjunction with a 3D transformed coordinate system. However, the absence of a clear solution method for the transformed coordinate system in MCNP presents a challenge. To address this issue, a solution method based on the axis attributes of the surfaces in MCNP and the composite nature of the 3D transformed coordinate system is developed. The improved one-to-many method has been applied to the neutron modeling of CFETR, and its reliability has been verified. In the neutron calculation model corresponding to the one-to-many and one-to-one methods, relative differences of the total TBR and nuclear heating are 0.25%, 0.07% respectively. The contribution of blanket modules to tritium breeding ratio (TBR) and nuclear heating has a relative difference within the range of − 0.25–0.55%. The relative differences of neutron flux and nuclear heating distribution for individual blanket modules #3–1 and #6–1 are within the range of − 0.60–0.40%. The results indicate that the improved one-to-many method can be employed for neutronics modeling in the preliminary design of CFETR.

The R&D of Central Solenoid Model Coil is a preparatory stage towards the final fabrication of China Fusion Engineering Test Reactor Central Solenoid. In view of the risk of being tear down or destroyed of the CSMC insulation components and current lead caused by the electromagnetic force, the preload system is designed and mounted around the circumferential direction of the cylindrical coil modules. In order to check the joint resistance, peak magnetic field, AC loss, mechanical performance of preload components under eddy current, CSMC will be tested under several typical current waves. For the sake of safety, a comprehensive mechanical analyses on the preload components need to be carried out before the final commissioning of CSMC. In this paper the magnetic density and eddy current on the preload components are calculated first. Then the electromagnetic force on the preload components under the testing current is analyzed. Finally, the mechanical analysis and stress evaluation are performed. The study presented in the paper will provide reference for the operation of CSMC under the testing current.

The effects of divertor pumping on divertor detachment and core performance are investigated using SOLPS-ITER simulations for the H-mode discharges with argon (Ar) seeding on EAST. The simulation results show that a relatively low pumping speed (S) is advantageous for achieving divertor detachment due to an increased Ar density and enhanced radiative dissipation. On the other hand, a relatively low S results in a high Ar density in the core region, which is detrimental to the core performance. Increasing S improves the particle removal capacity, which is not conducive to obtaining detachment but is conducive to reducing the Ar accumulation in the core region. In order to evaluate the compatibility of detachment and high core plasma performance, the impact of S on the divertor Ar retention (measured by impurity compression C_Ar and enrichment E_Ar) and the corresponding physical mechanisms were analyzed. In cases with relatively low and medium upstream density (({n}_{mathrm{e},mathrm{sep}}^{mathrm{OMP}})), a higher S is beneficial to increase C_Ar and E_Ar, i.e. better core-divertor compatibility, mainly due to the diminished neutral diffusion towards the upstream and the enhanced net force on the Ar towards the target. At relatively high ({n}_{mathrm{e},mathrm{sep}}^{mathrm{OMP}}), both C_Ar and E_A show no clear change with increasing S. This is because the negative contribution of the reduced relative distance between the Ar ionization front and the velocity stagnation point of the Ar ions to the Ar retention becomes significant with increasing S, which can even offset the positive contribution of the neutral diffusion and the net force.

The aim of this study is to investigate the behaviour of liquid metal flow in Capillary Porous System (CPS) under strong external magnetic field. Overlapping simple cubic (SC) periodic array of electrically non-conducting spheres with diameter 6 mm and distance between spheres centres 5.6 mm is 3D printed from PLA electrically non-conducting filament. At room temperature, flow of up to 50 mL/s of In–Ga–Sn in pore space in magnetic field of superconducting magnet up to 5T is investigated. Three orientations of magnetic field in relation to the main flow in SC cell are considered—colinear with main flow and perpendicular to it. The values of Reynolds, Hartmann and Stuart numbers in experiment are up to 1160, 90 and 350, respectively. The results indicate that parallel to the main flow orientation of magnetic field has little influence on the flowrate, while perpendicular orientation strongly reduces flowrate with dependence close to 1/Ha, which agrees well with ANSYS Fluent simulations in a unit SC cell, resembling results for channel flow in magnetic field.

The liquid metal magnetohydrodynamic (MHD) flow through coupled ducts with conducting walls under inclined transversal gradient magnetic field is an important physical flow phenomenon, which has the unknown physical mechanism about the interaction between the electromagnetic coupling effect and the three-dimensional (3D) MHD effect. To reveal this physical mechanism, 3D numerical simulations based on a customized solver in the OpenFoam environment are conducted to systematically study the effect of inclined gradient magnetic field on the MHD flow states through coupled conducting ducts. Then the mechanism behind the generation of the 3D MHD effect in the gradient magnetic field zones has been discussed in detail. It is found that the electromagnetic coupling effect can enhance this 3D MHD effect in the co-flow case, but suppress it in the counter-flow case. Moreover, the strong electromagnetic coupling effect in the counter-flow case will induce a “self-circulation” flow region in the duct when the external magnetic field is inclined, and the inclined angle also has a great influence on the area of this flow region, which reduces with the increase of the inclined angle. These results are important for the in-depth fundamental understanding of the 3D MHD effect of liquid metal flowing through coupled conducting ducts under inclined gradient magnetic field, and also helpful for the future design of the liquid metal blanket of fusion reactor.