Magnetoconvection in a horizontal duct flow at very high Hartmann and Grashof numbers

Direct numerical simulations and linear stability analysis are carried out to study mixed convection in a horizontal duct with constant-rate heating applied at the bottom and an imposed transverse horizontal magnetic field. A two-dimensional approximation corresponding to the asymptotic limit of a very strong magnetic field effect is validated and applied, together with full three-dimensional analysis, to investigate the flow's behaviour in the previously unexplored range of control parameters corresponding to typical conditions of a liquid metal blanket of a nuclear fusion reactor (Hartmann numbers up to $10^4$ and Grashof numbers up to $10^{10}$ ). It is found that the instability to quasi-two-dimensional rolls parallel to the magnetic field discovered at smaller Hartmann and Grashof numbers in earlier studies also occurs in this parameter range. Transport of the rolls by the mean flow leads to magnetoconvective temperature fluctuations of exceptionally high amplitudes. It is also demonstrated that quasi-two-dimensional structure of flows at very high Hartmann numbers does not guarantee accuracy of the classical two-dimensional approximation. The accuracy deteriorates at the highest Grashof numbers considered in the study.

Analyzing Fast-ions Trajectories in a Nuclear Fusion Reactor through Its Poincaré-Island Size and Ripple Resonance

Fast-ions confinement is a prominent subject in developing nuclear fusion reactors due to its importance in sustaining the burning plasma and keeping energy production. However, confining them has proven to be difficult until now, and one of the reasons is that the inherent discrete magnetic field produces a magnetic ripple. A better understanding of fast-ions transport using appropriate numerical calculation tools needs to be developed to overcome such a challenge in the engineering aspect. This study revisited data collection of fast ion transport simulated under the ripple presence in a nuclear fusion device. The ion trajectories were followed using two orbit-following equation schemes, and the ripple-resonance island size in the Poincaré section was compared. The result showed that the island size obtained by each scheme was different when the particle resonates with a stronger ripple field and, proportionally, the diffusion coefficients are different. The physical meaning and consequence behind this discovery were discussed in this paper.

TRACING THE EMERGENCE OF DESIGN PROBLEMS AND THEIR IMPACTS ON THE COMPLEXITY OF ENGINEERING SOLUTIONS

The design of ITER, a large-scale nuclear fusion reactor, is intertwined with profound research and development efforts. Tough problems call for novel solutions, but the low maturity of those solutions can lead to unexpected problems. If designers keep solving such emergent problems in iterative design cycles, the complexity of the resulting design is bound to increase. Instead, we want to show designers the sources of emergent design problems, so they may be dealt with more effectively. We propose to model the interplay between multiple problems and solutions in a problem network. Each problem and solution is then connected to a dynamically changing engineering model, a graph of physical components. By analysing the problem network and the engineering model, we can (1) derive which problem has emerged from which solution and (2) compute the contribution of each design effort to the complexity of the evolving engineering model. The method is demonstrated for a sequence of problems and solutions that characterized the early design stage of an optical subsystem of ITER.

Influence of High Energy Particles on Copper and Stainless Steel in Fusion Reactor Materials

Many studies were focused on the effect of fusion plasma particles onto the structural materials of future nuclear fusion reactor. In this paper, the effect of the products of the first generation fuel reaction on structural fusion materials as copper and 316-stainless steel target materials was studied. Firstly, the effect of 14.1 MeV neutrons produced from D-T neutron generator for different irradiation time equal to 10, 20, 30, 50 and 60 minutes was investigated. Hence, this effect was analyzed and characterized by X-ray diffration analysis, surface roughness tester, scanning electron microscope and Vickers hardness. Secondly, the effect of 3.5 MeV α-particles on these target materials by different incident angles equal to 0°, 30°, 45°, 60° and 85° using SRIM code was studied. Also, SRIM code was used for calculation α-particles trajectories, projected and straggle ranges, skewness, kurtosis, target ionization / phonons and total displacements for copper and 316- stainless steel target materials.

T3073 & T3074 Test report: electric energy recovered and large magnetic field due nuclear fusions measured

The measured results of two tests T3073 and T3074 performed in 28 August, 2020 are presented in this paper. Tests are conducted in the z-pinch type nuclear fusion reactor Pulsotron-3 with the target loaded with Hydrogen-Boron (H+B11) thermonuclear fuel. A group of Energy Recovery Coils (ERCs) were mounted to recover the electric energy directly from the plasma for the first time in the world and ERCs stored the energy in several large capacitors. During the test T3073 and T3074 the energy recovery capacitors recovered 22.59% and 17.74% of the injected energy at the target. A magnetic sensor MAG-4 consisting of inductor coils and dipoles were installed in Pulsotron-3 to measure the Time Of Flight (TOF) of the plasma and the magnetic field generated due to nuclear fusion. Magnetic fields more than 4 megateslas are obtained during the two tests. It is also observed that Pulsotron-3 with the target loaded with thermonuclear fuel generated 20-34 times larger peak magnetic fields and 12-18 times larger stabilized magnetic fields compare to the tests done using unloaded target (dummy loads). In this proposed technology Pulsotron-3 utilizes thermonuclear fuel to generate clean electric power without CO2 footprint and reduce the operational cost. This industrial approach is a promising solution that can reduce world emissions to zero in less than 8 years.