Publications

For applications requiring 5-20 mW electrical power for 10-20 years, tritium-based radioisotope thermoelectric generators may be an alternative to Pu-238 based devices. Tritium can be stored compactly on a titanium bed. However, one of the main challenges then becomes loading the heat source at temperatures compatible with existing bismuth telluride thermoelectric module technology (<300 °C). We find that a 180 nm palladium coating enables titanium to be loaded with hydrogen isotopes without the typical 400-500 °C vacuum activation step. Further, we observe that the hydriding kinetics of Pd coated and vacuum activated Ti are similar; both of which can be described by the Mintz-Bloch adherent film model, where the rate of hydrogen absorption is controlled by diffusion through an adherent metal-hydride layer. Finally, we design a prototype heat source vessel and demonstrate that it can be loaded completely, at temperatures below 300 °C, in less than 10 h. © 2012 Elsevier Ltd. All rights reserved.

Oxygen gas injection has been studied as one method for rapidly generating hydrogen gas from a uranium hydride storage system. Small scale reactors, 2.9 g UH{sub 3}, were used to study the process experimentally. Complimentary numerical simulations were used to better characterize and understand the strongly coupled chemical and thermal transport processes controlling hydrogen gas liberation. The results indicate that UH{sub 3} and O{sub 2} are sufficiently reactive to enable a well designed system to release gram quantities of hydrogen in {approx} 2 seconds over a broad temperature range. The major system-design challenge appears to be heat management. In addition to the oxidation tests, H/D isotope exchange experiments were performed. The rate limiting step in the overall gas-to-particle exchange process was found to be hydrogen diffusion in the {approx}0.5 {mu}m hydride particles. The experiments generated a set of high quality experimental data; from which effective intra-particle diffusion coefficients can be inferred.

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