A. Iwamoto

K. Takahata

S. Nishijima

Y. Izumi

Y. Tatsumi

National Institute for Fusion Science (NIFS-Repository)

§ 21. Analysis of Cryogenic Stability inSuperconducting Magnet for NuclearFusion Reactor by Lattice BoltzmannMethodTatsumi, Y., Izumi, Y., Nishijima, S. (Dept. Nucl.Eng., Osaka Univ.)Iwamoto, A., Takahata, K.analysis method of this combined model. The temperatureof liquid helium rose by the effect of the convection withincrease of time steps. Since the temperature of liquidhelium rose, the bubbles were generated and growing upwith time steps. Because of the effect of gravity, thedistribution of high-temperature region and bubble came upto the upper area step by step.,°0 5 101520 M JO)5 40 ts! °0 5 10 15 2!0 25 30 1540.f5 50 o-J-,-,, <051015202530 3IS 40 -45 50(c)(c)"....lll-(b)(b),o 5 10 15 20 25 30 3S 40 50(a)(a)'. <0510151025 30)$ Ml45 51References1) "Introduction of Fluid Analysis by Lattice Gas Methodand Lattice Boltzmann Method", Atomic Energy Society ofJapan (2001).2) Shen X. and Chen H., Phys. Rev. E, 47 (1993) 1815.Fig. 2. Temperature distribution of liquid helium usingcombining model, (a): 3000, (b): 3500, and (c): 4500 timesteps.In conclusion, we could quantitatively analyze a series ofinstable states that occur within the superconducting magnet,such as heat conduction of wire, generation of theconvection and voids after the heat generation at the wire.The stability of a superconducting wire was affected notonly by the transport current but also by the flow of liquidhelium.Fig. 1. Density distribution of liquid helium using combiningmodel, (a): 3000, (b): 3500, and (c): 4500 time steps.The nuclear fusion energy is expected as a future energyresource. In order to maintain nuclear fusion reaction, it isnecessary to shut up plasma. Magnetic confmementsystem is the system of shutting up into the plasma containermade in the strong magnetic field in order to hold the plasmaof super-high temperature in a certain space and time. Theimportant characteristics of the superconducting magnet areas followings;The electric resistance in conductor is zero.The power loss is small even under the large transportcurrent.The high density current can be transported.It is possible to produce high magnetic field with smallpower.The heating generated by the disturbances sometimes causesthe normal state locally. The current at this area inducesthe further heating. The transition from superconducting tonormal state is called "quench". It is thought that thequench is the most important problem for thesuperconducting magnets. Therefore, the coolingcapability and the stability of the superconducting magnethave been studied by analyzing the flow of liquid helium inthe superconducting magnet.In the calculation, we applied the lattice Boltzmannmethod l ) which is suitable for the analysis of the complexflows and the heat transfer. And it was combined withShen-Chen modee) which can treat void formation. Weanalyzed the propagation of the normal zone in the wiretogether with the temperature distribution in the liquidhelium, and heat transfer of the liquid helium in generationofvoid.Figure 1 shows the density distribution of liquid heliumusing lattice Boltzmann and Shen-Chen combining model.A unity time step corresponds to 8.32xIO-7 sec. In thisfigure, the heater which generates heat was set at x = 10 - 40and y = O. A heat disturbance at the center of the wire wasapplied at a time step of t = O. Figure 2 shows thetemperature distribution of liquid helium using combiningmodel. From these figures, it could be concluded that theheat conduction of wire, the convection of liquid helium andthe generation of the voids were able to analyze by the113

Analysis of Cryogenic Stability in Superconducting Magnet for Nuclear Fusion Reactor by Lattice Boltzmann Method

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