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Tritium breeding and direct energy conversion are key technological problems in the development of practical fusion reactors. Lithium in some form is needed for tritium generation, but certain chemical problems must be overcome. Alternatives to lithium metal should be considered. Better methods must be developed for efficiently recovering the tritium and safely disposing of the unwanted byproducts. Separation of the fusion fuel and waste products will be especially challenging for mirror machines with direct energy conversion. Hopefully, in the long run, these machines will employ the DHe3 fuel cycle, but this will impose additional demands for efficient helium isotope separation and, possibly, tritium storage in some manner that allows for recovery of the He3 decay product.

The DOE Fuel Cell technical team recommended ASTs were performed on 2 different MEAs (designated P5 and HD6) from Ballard Power Systems. These MEAs were also incorporated into stacks and operated in fuel cell bus modules that were either operated in the field (three P5 buses) in Hamburg, or on an Orange county transit authority drive cycle in the laboratory (HD6 bus module). Qualitative agreement was found in the degradation mechanisms and rates observed in the AST and in the field. The HD6 based MEAs exhibited lower voltage degradation rates (due to catalyst corrosion) and slower membrane degradation rates in the field as reflected by their superior performance in the high potential hold and open-circuit potential AST tests. The quantitative correlation of the degradation rates will have to take into account the various stressors in the field including temperature, relative humidity, start/stops and voltage cycles.

The structure and conductivity of cerium and lanthanum phosphate glasses and glass-ceramics were investigated. The effects of varying the metal to phosphate ratio in the glasses, doping LaP3O9 glasses with Ce, and recrystallization of CeP3O9 glasses, on the glasses' microstructure and total conductivity were investigated using XRD, SEM, and AC impedance techniques. Strong increases in conductivity occurred when the glasses were recrystallized: the conductivity of a cerium metaphosphate glass increased conductivity after recrystallization from 10-7.5 S/cm to 10-6 S/cm at 400oC.

This paper reports on direct thermal to electrical energy conversion by performing the Olsen (or Ericsson) cycle on [001]-poled 0.945PbZn1/3Nb2/3O3-0.055PbTiO3 (PZN-5.5PT) single crystals. The cycle consists of two isothermal and two constant electric field processes. The energy density was found to decrease with increasing cycle frequency while the power density increased. The maximum energy density obtained was 150 J/L/cycle for temperatures between 100 and 190oC and electric field between 0 and 1.2 MV/m at frequency 0.034 Hz. The maximum power density reached 11.7 W/L at 0.1 Hz for temperatures between 100 and 190oC and electric fields between 0.2 and 1.5 MV/m. Moreover, the dielectric constant and saturation polarization of PZN-5.5PT are reported for the first time at 0.1 Hz for temperatures between 100 and 190oC. Finally, the experimental results agree relatively well with predictions by a recently developed temperature-dependent property model already validated with PMN-32PT. Inter-sample variability and sample durability are also discussed.

Single Chamber Fuel Cells: Flow Geometry, Rate and Composition Considerations Ionel C. Stefan, ∗ Craig P. Jacobson, Steven J. Visco, Lutgard C. De Jonghe Lawrence Berkeley National Laboratory 1 Cyclotron Rd, Berkeley, CA 94720 ABSTRACT Four different single chamber fuel cell designs were compared using propane-air gas mixtures. Gas flow around the electrodes has a significant influence on the open circuit voltage and the power density of the cell. The strong influence of flow geometry is likely due to its effect on gas composition, particularly on the oxygen chemical potential at the two electrodes as a result of gas mixing. The chamber design which exposes the cathode first to the inlet gas was found to yield the best performance at lower flow rates, while the open tube design with the electrodes equally exposed to the inlet gas worked best at higher flow rates. INTRODUCTION Single chamber fuel cells (SCFCs) have no seal separating the anode and cathode, and consequently both electrodes are simultaneously exposed to the fuel/air mixture. Although SCFCs were proposed more than four decades ago, 1,2 only recently have these devices surpassed the level of laboratory curiosity by achieving electrode power densities comparable to those of the much more studied dual chamber, sealed cells. 3,4 While the SCFC research is still at an early stage, new applications are emerging, such as simple low-power sources 5 and hydrocarbon sensors. 6 The principle of operation for a single chamber fuel cell is based on the different electrocatalytic properties of fuel cell electrodes toward anodic oxidation of fuel and cathodic reduction of oxygen, respectively, thus resulting in an EMF even in a uniform atmosphere containing E-mail: CIStefan@lbl.gov