T.Q. Hua

Overview of the ARIES-RS reversed-shear tokamak power plant study

The ARIES-RS tokamak is a conceptual, D‐T-burning 1000 MWe power plant. As with earlier ARIES design studies, the final design of ARIES-RS was obtained in a self-consistent manner using the best available physics and engineering models. Detailed analyses of individual systems together with system interfaces and interactions were incorporated into the ARIES systems code in order to assure self-consistency and to optimize towards the lowest cost system. The ARIES-RS design operates with a reversed-shear plasma and employs a moderate aspect ratio (A4.0). The plasma current is relatively low (Ip11.32 MA) and bootstrap current fraction is high ( fBC 0.88). Consequently, the auxiliary power required for RF current drive is relatively low ( 80 MW). At the same time, the average

MHD pressure drops and thermal hydraulic analysis for the ITER breeding blanket design

The breeding blanket design of the International Thermonuclear Experimental Reactor (ITER) is a self-cooled liquid lithium system with a vanadium structure. Electrical insulation of the coolant channel surfaces from the liquid metal is required to reduce the magnetohydrodynamic (MHD) pressure to less than 1 MPa. Insulation is provided by AIN coating at the channel surfaces in contact with lithium. MHD pressure drop and thermal hydraulic analysis of the blanket design is carried out subject to pressure, temperature, and stress considerations. Design windows relating the lithium flow velocity, MHD pressure, and structural temperature are formulated. The requirements of the insulator coating and characterization of the coating effectiveness are presented. Effects on the MHD pressure drop due to uniform cracks through the coating layer is also analyzed.

Removal of Zirconium in Electrometallurgical Treatment of Experimental Breeder Reactor II Spent Fuel

During electrorefining of irradiated, binary U-Zr Experimental Breeder Reactor II fuel, a portion of zirconium is found to dissolve along with uranium. It accumulates in the cadmium pool both as dissolved zirconium and as a zirconium-cadmium intermetallic precipitate. Two electrochemical methods of removing zirconium from the electrorefiner have been evaluated. The first is a three-step method consisting of chemical oxidation of zirconium by CdCl2 addition, depletion of zirconium from the cadmium pool by electrotransport, and drawdown of zirconium from the LiCl-KCl eutectic salt by using a different electrorefiner configuration. A transport model is employed to determine the cell operating conditions for growing pure zirconium deposits and the throughput rate. The second method eliminates the chemical oxidation step and permits codeposition of uranium and zirconium onto the solid cathode. The transport model is used to assess the level of uranium impurity in the cathode product; an additional step is proposed to reoxidize uranium in the deposit. The two methods are compared from the standpoints of throughput, deposit composition, deposit adherence to a solid cathode mandrel, and the underlying uncertainties. A brief review is given of the related past laboratory work on removal of zirconium from the electrorefiner.

Liquid lithium self-cooled breeding blanket design for ITER

Abstract To meet the technical objectives of the ITER extended performance phase (EPP) an advanced tritium breeding lithium/vanadium (Li/V) blanket was developed by two home teams (US and RF). The design is based on the use of liquid Li as coolant and breeder and vanadium alloy (V-Cr-Ti) as structural material. The first wall is coated with a beryllium protection layer. Beryllium is also integrated in the blanket for neutron multiplication and improved shielding. The use of tungsten carbide in the primary shield and in vacuum vessel provides adequate protection for toroidal field coils. A self-healing electrical insulator in the form of CaO or AlN coating layer is utilized to reduce MHD pressure drop in the system. To have a self-consistent ITER design, liquid metal cooling of the divertor and vacuum vessel is considered as well.

Electrotransport of Uranium from a Liquid Cadmium Anode to a Solid Cathode

Abstract During anodic dissolution of irradiated binary Experimental Breeder Reactor-II fuel, a portion of the electrorefined uranium collects in the underlying cadmium pool. It is periodically recovered by setting up a cell configuration in which the pool is made the anode and uranium is electrodeposited on a solid cathode mandrel. A theoretical model is used to determine the current structure of the liquid cadmium anode. The model is validated by comparing against the measured composition of the cathode deposits. Multinodal simulations are conducted to explain the bell shape of deposits observed with this mode of electrotransport. The simulations also determine the dependence of collection efficiency on the electrical charge passed that is functionally consistent with the experimental data. Finally, a simplified operating map of the electrorefiner is presented that can be used to determine the conditions for growing cathode deposits of target composition.

Behavior of uranium and zirconium in direct transport tests with irradiated EBR-II fuel

A theoretical model is used to analyze the transport of U and Zr in electrorefining of irradiated binary Experimental Breeder Reactor-II fuel. A limiting-current hypothesis is advanced to explain the observed dissolution of Zr in the presence of U at high, intermediate, and low cell voltages. The internal diffusion model predicts the existence of a critical current and a critical voltage for Zr oxidation. Experimental results are presented for a test designed and run based on optimum conditions determined from the model to dissolve U expediently while retaining Zr in the anode baskets. A simple model of kinetic exchange reactions between salt-phase U and Cd-phase Zr is formulated to explain the measured electrodeposition of Zr on the solid cathode. It is shown that the Zr content of the deposit is overpredicted if the pool is considered isolated and grossly underpredicted if the salt phase is equilibrated instantaneously with the Cd pool. Finally, the aspects of anodic current efficiency and cathodic collection efficiency are discussed taking into account shorting between the dissolution baskets and the Cd pool, multiple oxidation states of Zr, and the exchange reactions between the fuel and UCl{sub 3} prior to electrotransport.

The ARIES-RS power core—recent development in Li/V designs

The ARIES-RS fusion power plant design study is based on reversed-shear (RS) physics with a Li/V (lithium breeder and vanadium structure) blanket. The reversed-shear discharge has been documented in many large tokamak experiments. The plasma in the RS mode has a high beta, low current, and low current drive requirement. Therefore, it is an attractive physics regime for a fusion power plant. The blanket system based on Li/V has high temperature operating capability, good tritium breeding, excellent high heat flux removal capability, long structural life time, low activation, low after heat and good safety characteristics. For these reasons, the ARIES-RS reactor study selected Li/V as the reference blanket. The combination of attractive physics and attractive blanket engineering is expected to result in a superior power plant design. This paper summarizes the power core design of the ARIES-RS power plant study.

Uranium Transport in a High-Throughput Electrorefiner for EBR-II Blanket Fuel

Abstract A unique high-throughput Mk-V electrorefiner is being used in the electrometallurgical treatment of the metallic sodium-bonded blanket fuel from the Experimental Breeder Reactor II. Over many cycles, it transports uranium back and forth between the anodic fuel dissolution baskets and the cathode tubes until, because of imperfect adherence of the dendrites, it all ends up in the product collector at the bottom. The transport behavior of uranium in the high-throughput electrorefiner can be understood in terms of the sticking coefficients for uranium adherence to the cathode tubes in the forward direction and to the dissolution baskets in the reverse direction. The sticking coefficients are inferred from the experimental voltage and current traces and are correlated in terms of a single parameter representing the ratio of the cell current to the limiting current at the surface acting as the cathode. The correlations are incorporated into an engineering model that calculates the transport of uranium in the different modes of operation. The model also uses the experimentally derived electrorefiner operating maps that describe the relationship between the cell voltage and the cell current for the three principal transport modes. It is shown that the model correctly simulates the cycle-to-cycle variation of the voltage and current profiles. The model is used to conduct a parametric study of electrorefiner throughput rate as a function of the principal operating parameters. The throughput rate is found to improve with lowering of the basket rotation speed, reduction of UCl3 concentration in salt, and increasing the maximum cell current or cut-off voltage. Operating conditions are identified that can improve the throughput rate by 60 to 70% over that achieved at present.

Magnetohydrodynamic Flow in a Manifold and Multiple Rectangular Coolant Ducts of Self-Cooled Blankets

AbstractThe magnetohydrodynamic flow of a liquid metal through a manifold that feeds an array of electrically coupled rectangular ducts with thin conducting walls is investigated. This geometry is typical of an inlet/outlet manifold servicing arrays of poloidal coolant channels in tokamak self-cooled blankets. The interaction parameter and Hartmann number are assumed to be large, whereas the magnetic Reynolds number is assumed to be small. Under these assumptions, which are relevant to liquid-metal flows in self-cooled tokamak blankets, viscous and inertial effects are confined to very thin boundary layers adjacent to the walls. The analysis for obtaining three-dimensional solutions outside these layers is described, and numerical solutions are presented. Electrical coupling between the common manifold and the coolant ducts, as well as coupling among the coolant ducts themselves, necessitates simultaneous solutions for the multiple channels, and uniquely determines the partition of the total flow rate amo...

Heat transfer in laminar and turbulent liquid-metal MHD flows in square ducts with thin conducting or insulating walls

Abstract The heat transfer in fully-developed liquid-metal flows in a square duct with a uniform, transverse magnetic field is analyzed. Velocity profiles obtained for laminar and turbulent regimes [Cuevas, S., Picologlou, B. F., Walker, J. S. and Talmage, G., Int. J. Engng Sci. , 1997, 35 , 485] are employed to solve the heat transfer equation through finite differences, in a duct with one side wall (parallel to the magnetic field) uniformly heated and three adiabatic walls. Turbulent effects are introduced through eddy viscous and thermal diffusivity models from the renormalization group theory of turbulence [Yakhot, V. and Orszag, S. A., J. Sci. Comput. , 1986, 1 (1), 3]. Analysis focuses in determining how the structure of the side-layer flow, influenced by the wall conductance ratio and Hartmann and Peclet numbers in the ranges of interest of fusion blanket applications, affects the heat transfer processes. Numerical calculations for liquid lithium show that for thin conducting wall duct cases, the laminar MHD heat transfer mechanism, characterized by high-velocity side-wall jets, appears to be more efficient than turbulent mixing in the boundary layer for a given Peclet number.