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[en] Our OFES-sponsored research on IFE technology originally focused on studies of grazing-incidence metal mirrors (GIMM's). After the addition of GIMM research to the High Average Power Laser (HAPL) program, our OFES-sponsored research evolved to include laser propagation studies, surface material evolution in IFE wetted-wall chambers, and magnetic intervention. In 2003, the OFES IFE Technology program was terminated. We continued to expend resources on a no-cost extension in order to complete student research projects in an orderly way and to help us explore new research directions. Those explorations led to funding in the field of extreme ultraviolet lithography, which shares many issues in common with inertial fusion chambers, and the field of radiative properties of laser-produced plasma.
[en] A new profile analysis package for use with the Thomson scattering data on ISX-B has recently been implemented. The primary feature of this package is a weighted least squares fitting of temperature and density data to generate a representative curve, as opposed to the previous hand-fitting technique. The changes will automate the manner in which data are transmitted and manipulated, without affecting the calculational techniques previously used. The computer programs have also been used to estimate the sensitivity of various plasma quantities to the accuracy of the Thomson scattering data
[en] Target survival in the hostile, high temperature xenon environment of the proposed Laser Inertial Fusion Energy (LIFE) engine is critical. This work focuses on the flow properties and convective heat load imposed upon the surface of the indirect drive target while traveling through the xenon gas. While this rarefied flow is traditionally characterized as being within the continuum regime, it is approaching transition where conventional CFD codes reach their bounds of operation. Thus ANSYS, specifically the Navier-Stokes module CFX, will be used in parallel with direct simulation Monte Carlo code DS2V and analytically and empirically derived expressions for heat transfer to the hohlraum for validation. Comparison of the viscous and thermal boundary layers of ANSYS and DS2V were shown to be nearly identical, with the surface heat flux varying less than 8% on average. From the results herein, external baffles have been shown to reduce this heat transfer to the sensitive laser entrance hole (LEH) windows and optimize target survival independent of other reactor parameters.
[en] This document is a progress report on two technical studies carried out during 1986, both of which relate to the implementation phase of FNT. The first, which is a follow-up to FINESSE, focuses on specific key questions for: (1) very near-term (0 to 3 years) non-fusion experiments and facilities, and (2) FNT testing in a fusion facility. The second is the initial stage of a detailed effort to develop theory, models and computer codes for predicting the performance of nuclear components. Chapters are presented on (1) introduction and chapter summaries, (2) non-fusion experiments and facilities, (3) fusion testing issues, and (4) theory and modeling. Chapter 2 is an assessment of the relative advantages of many solid breeders, neutron multipliers and configurations. Various issues affecting design and cost of the blanket are examined in Chapter 3. Chapter 4 reports on the progress of the initial stage of an effort to develop theory and analytical and numerical models for nuclear components. A major part of the effort has focused on modeling of MHD effects for liquid metal blankets. Progress has also been made on modeling tritium transport and inventory in solid breeder blankets and the thermomechanical behavior of liquid-metal-cooled limiters
[en] This paper presents a numerical analysis of the flow of an electrically conducting fluid in a pipe in the presence of a magnetic field aligned with the direction of the mean flow. The present numerical solution is based on the SIMPLE method developed by Patankar and Spalding where the continuity, momentum, and energy equations are solved simultaneously in terms of velocity, pressure, and temperature. The flow is assumed to be laminar and incompressible. The velocity profile was calculated in the presence of an axial magnetic field and was compared with the analytical solution obtained by D'Arcy and Schmidt. The temperature profile and the Nusselt number were also calculated. For an order of magnitude estimate of the entry region effects in fusion reactor design, consider lithium coolant flowing in a pipe of 10 cm in diameter with a mean velocity of ∼ 0.5 m/s in the presence of a toroidal field of ∼ 10T. For these conditions, we obtain Re = 5 x 104 and N/Re = 1. x/a Re = 0.3 and the entry length is ∼ 750 m. This is certainly longer than coolant pipes in practical blanket designs, which means that the flow in a parallel channel of a reactor blanket will never reach full development. The implication on the heat transfer is that the local Nusselt number is about two to three times higher than the fully developed one
[en] MHD flow in liquid metal blankets with helical vanes is discussed. The velocity profile and the MHD pressure drop in a pipe with a diametric turning vane under an axial magnetic field are derived with the assumption of fully developed conditions. The fluid flows helically along the vane with the velocity almost inversely proportional to the radius. Eddy currents flow radially in the fluid and then back through the outer wall and the vane. The radial current and the axial field cause a force in the circumferential direction, which resists the circumferential flow. Since the current intensity can be reduced by thinning the vane, the MHD pressure drop is low in a pipe with a thin vane. A reference design of a liquid metal blanket with a helical vane is made, and the required thickness of the vane is discussed from the viewpoint of structural strength. The temperature distribution is calculated and is compared with those of pipes without vanes. The vane is shown to keep the first wall temperature low with a small additional pressure drop. (author)
[en] The induced pressures, stresses and strains in unrestrained axisymmetric toroidal shells are studied to scope the behavior of tokamak first walls during plasma disruptions. The modeling includes a circuit analog representation of the shell to solve for induced currents and pressures, and a separate quasi-static 1-D finite element solution for the mechanical response. This work demonstrates that the stresses in tokamkak first walls due to plasma disruption may be large, but to first order will not cause failure in the bulk structure. However, stress concentrations at structural supports and discontinuities together with resonant effects can result in large enhancements of the stresses, which could contribute to plastic deformation or failure when added to the already large steady state thermal and pressure loading of the first wall
[en] Nonuniform flow distribution between parallel channels is one of the most serious concerns for self-cooled liquid metal blankets with electrically-insulated walls. The authors show that uncertainties in flow distribution can be dramatically reduced by relatively simple design modifications. Several design features which impose uniform flow distribution by electrically coupling parallel channels are surveyed. Basic mechanisms for open-quotes flow balancingclose quotes are described, and a particular concept using localized passive electrodes is proposed for the U.S. ITER advanced blanket concept. Manifolding is required to distribute coolant throughout any reactor. In some designs, individual blanket modules include internal manifolding to distribute flow in parallel channels. In the current U.S. ITER design, individual modules consist of a single channel, but numerous modules are assembled in parallel. Regardless of the design details, the total pressure drop between manifolds has a single value, which the fluid experiences independent of its flow path. If different channels provide different flow resistances, then the bulk velocity will be different. Flow resistances can be affected by geometric effects, such as bends and changes in duct cross section, or by electrical effects, such as changes in the wall electrical resistance or magnetic field strength and orientation. In this paper, the authors examine several different techniques for flow balancing in liquid metal blankets. These include distributed coupling, localized coupling, and open-quotes natural couplingclose quotes. The attractiveness, or even feasibility, will depend on the reactor parameters, blanket design, and other factors
[en] An assessment of the thermal control mechanisms applicable to solid breeder blanket designs under ITER-like operating conditions is presented in this paper. Four cases are considered: a helium gap; a sintered block Be region; a sintered block helium region with a metallic felt at the Be/clad interface; and a Be packed bed region. For these cases, typical operating are explored to determine the ranges of wall load which can be accommodated while maintaining the breeder within its allowable operating temperature window. The corresponding region thicknesses are calculated to help identify practicality and design tolerances
[en] Use of the circuit network method is described for the solution of induced eddy currents in connected shell geometries. Accuracy is enhanced without a large number of elements by using improved discretization and reconstruction techniques in cases for which the structure geometry is relatively simple