An assessment of the issues on using flibe for fusion applications has been made. It is concluded that sufficient tritium breeding can be achieved for a flibe blanket, especially if a few cm of Be is include in the blanket design. A key issue is the control of the transmutation products such as TF and F2. A REDOX (Reducing-Oxidation) reaction has to be demonstrated which is compatible to the blanket design. Also, MHD may have strong impact on heat transfer if the flow is perpendicular to the magnetic field. The issues associated with the REDOX reaction and the MHD issues have to be resolved by both experimental program and numerical solutions.

This paper reports the results of the second phase evaluation of the EVOLVE W-alloy first wall and blanket design cooled by vaporizing lithium. For the transpirationcooled first wall and blanket concept, we identify the need to further quantify the data of lithium superheat from Walloy heated surface and bulk lithium slabs. For the boiling lithium blanket, we identify the need to elucidate the impacts of magnetic field on various stable-boiling regimes. We also find that this FW/blanket concept should have no problem in achieving adequate nuclear performance. With the addition of passive cooling loops, the concept has a strong possibility of achieving the safety requirement of not needing a public evacuation plan under the loss of power accident conditions. Even though the irradiated W-alloy may be subject to embrittlement, due to the relatively low system pressure of the design, it is shown to be able to withstand a large number of cracks. The fundamental issues of W-alloy properties under high neutron fluence irradiation and the components fabrication technique remain. Preliminary investigations of W-alloy fabrication and heat flux removal through SBIR programs have begun and the initial results are encouraging. We recommend that the investigation of critical issues of the EVOLVE concept continue since this innovative design has a good possibility of showing a way to achieve high performance and passively safe designs that are necessary for the utilization of fusion power.

This study, called APEX. is exploring novel concepts for fusion chamber technology that can substantially improve the attractiveness of fusion energy systems. The emphasis of the study is on fundamental understanding and advancing the underlying engineering sciences, integration of the physics and engineering requirements, and enhancing innovation for the chamber technology components surrounding the plasma. The chamber technology goals in APEX include: (1) high power density capability with neutron wall load > 10 MW/m(2) and surface heat flux > 2 MW/m(2), (2) high power conversion efficiency (> 40%), (3) high availability, and (4) simple technological and material constraints. Two classes of innovative concepts have emerged that offer great promise and deserve further research and development. The first class seeks to eliminate the solid "bare" first wall by Bowing liquids facing the plasma. This liquid wall idea evolved during the APEX study into a number of concepts based on: (a) using liquid metals (Li or Sn-Li) or a molten salt (Flibe) as the working liquid, (b) utilizing electromagnetic, inertial and/or other types of forces to restrain the liquid against a backing wall and control the hydrodynamic flow configurations, and (c) employing a thin (similar to 2 cm) or thick (similar to 40 cm) liquid layer to remove the surface heat Bur and attenuate the neutrons. These liquid wall concepts have some common features but also have widely different issues and merits. Some of the attractive features of liquid walls include the potential for: (1) high power density capability; (2) higher plasma beta and stable physics regimes if liquid metals are used; (3) increased disruption survivability; (4) reduced volume of radioactive waste; (5) reduced radiation damage in structural materials; and (6) higher availability. Analyses show that not all of these potential advantages may be realized simultaneously in a single concept. However, the realization of only a subset of these advantages will result in remarkable progress toward attractive fusion energy systems. Of the many scientific and engineering issues for liquid walls, the most important are: (I) plasma-liquid interactions including both plasma-liquid surface and liquid wall-bulk plasma interactions; (2) hydrodynamic flow configuration control in complex geometries including penetrations; and (3) heat transfer at free surface and temperature control. The second class of concepts focuses on ideas for extending the capabilities, particularly the power density and operating temperature limits, of solid first walls. The most promising idea, called EVOLVE, is based on the use of a high-temperature refractory alloy (e.g. W-5% Re) with an innovative cooling scheme based on the use of the heat of vaporization of lithium. Calculations show that an evaporative system with Li at similar to 1 200 degreesC can remove the goal heat loads and result in a high power conversion efficiency. The vapor operating pressure is low, resulting in a very low operating stress in the structure. In addition, the lithium flow rate is about a factor of ten lower than that required for traditional self-cooled first wall/blanket concepts. Therefore, insulator coatings are not required. Key issues for EVOLVE include: (1) two-phase heat transfer and transport including MHD effects; (2) feasibility of fabricating entire blanket segments of W alloys; and (3) the effect of neutron irradiation on W. (C) 2001 Elsevier Science B.V. All rights reserved.

Under the APEX program the He-cooled system design task is to evaluate and recommend high power density refractory alloy first wall and blanket designs and to recommend and initiate tests to address critical issues. We completed the preliminary design of a helium-cooled, W–5Re alloy, lithium breeder design and the results are reported in this paper. Many areas of the design were assessed, including material selection, helium impurity control, and mechanical, nuclear and thermal hydraulics design, and waste disposal, tritium and safety design. Systems study results show that at a closed cycle gas turbine (CCGT) gross thermal efficiency of 57.5%, a superconducting coil tokamak reactor, with an aspect ratio of 4, and an output power of 2 GWe, can be projected to have a cost of electricity at 54.6 mill/kW h. Critical issues were identified and we plan to continue the design on some of the critical issues during the next phase of the APEX design study.

The purpose of the ALPS program is to identify and evaluate advanced limiter/divertor systems that will enhance the attractiveness of fusion power. The highest priority goals at present are achieving high power density, up to 50 MW/m2, and showing compatibility of plasma-facing surfaces with plasma operation. Personnel representing a wide range of disciplines from a number of institutions are engaged in the program, where an evaluation phase of the program is planned for three years. Successful identification of promising concepts in the evaluation phase should lead to an R&D phase that includes proof-of-principle experiments.

The combined use of beryllium as plasma facing material and water as coolant in ITER (International Thermonuclear Experimental Reactor) poses the potential risk of significant hydrogen production under accident conditions. In this paper we describe on-going R&D at several different institutions worldwide to understand the beryllium/steam and beryllium/air interactions for the ITER design. Our understanding of beryllium chemical reactivity has progressed significantly during the ITER EDA (Engineering Design Activity), allowing us to more accurately assess ITER postulated accidents. We include a brief description of how these data were used in our modeling activities for the safety analysis of ITER.