Kazuyuki Noborio

One dimensional simulation of an inertial electrostatic confinement fusion device at low gas pressure operation

Abstract Using a 1-D particle code, we have analyzed characteristics of an Inertial Electrostatic Confinement Fusion device with external ion source which is added to enable low pressure operation. When the pressure becomes low, though neutron yield decreases, the decreasing amount is less than estimated from the decrease in background (target) gas density and it is confirmed that ions are accelerated efficiently with little energy loss through charge-exchange collision with background gas at low pressure. And when the pressure is lower than 0.05Pa, almost all injected ions reach to the cathode and it is expected that applying high geometrical transparency enhances accumulation of ion and enlarges neutron yield.

Compatibility of materials for advanced blanket with liquid LiPb

Parametric data of the corrosion (or erosion) behavior of blanket structural materials by LiPb liquid metals in flow conditions at high temperature with LiPb stream were measured to evaluate the compatibility. That is essential for the feasibility of high temperature blanket. An apparatus to rotate disk materials in liquid LiPb metal was used to measure the effect of flow speed as a function of the radial position on the disk. The materials used in this study were the Stainless steel (SUS316) for the reference and NITE SiCf/SiC composite (ϕ 35×2 mm), exposed to relative flow velocity of 10.47∼36.65 cm/s at 900 °C for 1000 h. The compatibility characteristics such as the mass transfer, change of microstructure and compositions, etc. of the specimens during the corrosion process were examined by optical microscope, fine scale weight measurement, SEM/EDX and AFM. The results showed that the NITE SiCf/SiC composites had poor wettability with the liquid LiPb and presented the good compatibility. However a part of the fiber coated with C was wet with the metal and a precipitation of metallic elements were observed.

Enhanced Mass Transfer of Deuterium Extracted from Falling Liquid Pb-17Li Droplets

Abstract Release of deuterium from falling droplets of Pb-17Li in vacuum is experimentally studied. By comparing different diameter nozzle data each other, the effect of ambiguous solution is eliminated, and reliable result is attained. The amount of deuterium that is dissolved into Pb-17Li, followed by the release from the liquid droplets in vacuum, is measured with four different diameter nozzles ranging from 0.4 mm-1.0 mm under an initial velocity of 3.0 m/s and four temperatures between 375 °C and 450 °C. The resultant mass transport, represented by quasi-dispersion-coefficient is 3.4 × 10-7 [m2/s], which is approximately two orders of magnitude faster than previous studies under static condition. It also revealed different temperature dependency. Cyclic deformation of the sphere shape is observed with a high speed movie camera. These results show the falling droplets of liquid Pb-17Li in vacuum follow the mass transfer mechanism under convection prior domain by self-excited oscillation. This result suggests that the tritium recovery method from a breeding liquid Pb-17Li blanket is viable when using multiple nozzles in vacuum for the extraction.

Neutron production rate of inertial electrostatic confinement fusion device with fusion reaction on surface of electrodes

Abstract The neutron production rate (NPR) through fusion reaction on the surface of electrode(s) of an IECF (Inertial Electrostatic Confinement Fusion) device, which is expected to increase at low pressure, has been evaluated with a one dimensional simulation code and an experimental device. In the simulation, the NPR on the cathode and the anode has been evaluated individually as a function of pressure. The simulation results reveal that the NPR on the cathode increases at low pressure and that on the anodes increases at high pressure. In the experiment, titanium coated electrodes have been used in order to rise the adsorbed amount, and the results show same tendency along with the pressure as calculation results. And the maximum value increases 3 times by coating titanium.

Preliminary design of high temperature lithium-lead blanket with SiC cooling panel

A high temperature lithium-lead blanket, which can be made within a limited extrapolations of present technology, has been proposed. The blanket structure is based on F82H as vessel material, and Pb-17Li as breeder. SiCf/SiC cooling panel is inserted between them to achieve high temperature extraction of Pb-17Li while maintaining F82H under allowable temperature limit. Neutronic analysis using ANISN code has been conducted to assess tritium breeding capability, shielding performance, and nuclear power generation. Heat transfer for the Pb-17Li streams has been calculated considering MHD pressure loss to be acceptable. Temperature distribution in the F82H vessel and SiCf/SiC cooling panel has been calculated using ANSYS Version 10.0. The results show that the maximum temperature of the F82H does not exceed 550 °C with He flow velocity of 60 m/s. The thermal-hydraulic evaluations of heat transfer media based on the experimental data shows that the overall heat transfer coefficient between SiC and Pb-17Li in the blanket is estimated to 650-800 W/m2K.

Design of Tritium Collecting System from LiPb and LiPb Dropping Experiment

Abstract In the design of the fusion blanket, it is important to gather generated tritium as quick as possible and supply them to a fuel supply system for keeping fuel cycle and reducing tritium inventories in the fusion reactor at the same time. In the advanced blanket concept which uses Lithium-Lead (LiPb) as the working fluid for heat removal, neutron shielding and tritium breeding, collection of generated tritium is thought not to be difficult as the solubility of hydrogen into the LiPb is small enough. But examination and design of these collecting systems was not fully studied. In this paper, we made the conceptual design of the tritium collecting device using vacuum sieve tray, and studied formation process of LiPb droplets by making a simple experimental device. It was found that droplets of about 0.9-mm radius were formed at 8~12-cm distance from nozzle when LiPb discharges from the nozzle with 1-mm diameter hole at pressure of 2.5×104 Pa. Using this value, it is estimated that the tritium collecting efficiency of 45% can be achieved with 1-m height single stage sieve tray at temperature of 500 °C.

High Temperature Operation of LiPb Loop

Abstract By introducing an induction heater and combination of a compact heat exchanger and a helium loop as a cooler, high temperature operation of lithium-lead loop at Kyoto University was performed successfully. After modification of thermal insulation, reasonable temperature distribution was obtained and sufficient effective heating power of 2.7kW and heating efficiency of 40% was demonstrated without concern about overheating of downstream of the high temperature section. As a result, observed highest temperature is 926°C and 4 hours continuous operation above 900°C was achieved.

Development of high temperature SiC/SiC composite intermediate heat exchanger for He and LiPb

In order to develop a compact intermediate heat exchanger which is applicable for high temperatures above 900°C, assuming HTGR (high temperature gas cooled reactor), a heat exchanger module made of SiCf/SiC composite has been designed, fabricated and tested with LiPb-He double loop. The heat transfer from liquid metal to gas has been measured, and heat transfer of ≫1.3kW and reasonable heat exchange performance are obtained with 10cm × 10cm × 3cm test module. The results also show that the heat transfer from the IHX module to fluid is predominant in overall heat transfer coefficient.

Error evaluation in hydrogen isotope permeability measurement and the required degree of vacuum

In the measurement of the hydrogen isotope permeability of Silicon-Carbide, control and the evaluation of the wraparound through the sample holder is important problem. For this purpose, the heated holder part is enclosed by a glass tube and kept at vacuum during experiments, but detail examination about required degree of the vacuum has not be made. In this paper, the amount of the wraparound flow was evacuated by experiments and model calculations. It is found in the experiments, the flow rate from glass tube to the low pressure line is linear dependence on the tube pressure at 0.1~100 Pa, although that from high pressure line into the glass tube is proportional to square-root of pressure of the high pressure line as expected. The ratio of the wraparound flow to the mail flow during permeation measurement condition was estimated to be 6~10 % from the extrapolation of experiments results. On the other hand, the model calculation results were still one order higher than observed even when first-order dependency was assumed. The impurities on outer surface of the holder or gas are considered to limit the permeation in the experiments.

Deuterium Transport Prediction in Oscillating Liquid Pb-17Li Droplet

Abstract The feasibility of deuterium mass transport prediction from falling droplets of Pb-17Li was verified. This prediction is one of key techniques of the engineering design of tritium extraction device for the fusion reactor. The mass-transfer-coefficient, deduced on the surface-stretch-model was applied. As the experimental results, deuterium mass transport in the falling droplets from four different size nozzles, at four temperature conditions between 375 °C and 450 °C, performed by the authors, were compared. Resultant Sherwood number was between 494 and 598, and explained the experimental result of the two orders of magnitudes differences with the reported diffusion in static condition. Though, the ratio of theory and experiment still remained between 1.8 and 2.3. Simple boundary condition, not considering the number of oscillation, wide range of reported diffusivity value are considered to be main reasons of the deviation. The analysis model including these factors is to improve prediction accuracy. This result is expected to contribute to a preliminary design of a tritium extraction device.