Reproducible tritium generation in electrochemical cells employing palladium cathodes with high deuterium loading

Abstract

Reproducible tritium generation well above background has been observed in tightly closed D 2SO 4-containing cells in four out of four Pd wire cathodes of one type. Tritium analysis was performed before and after each experiment on the Pd, the electrolyte and the gas in the head space. No tritium generation was observed in four identical Pd cathodes in H 2SO 4 cells operated at the same time under the same conditions. A cyclic loading-unloading regime with low current densities, rather than the usual continuous constant current regime, was employed to attain D/Pd and H/Pd loadings of 1±0.05 reproducibly. D/Pd loadings greater than 0.8±0.05 appear to be necessary to generate tritium. The largest amount of tritium, generated in 7 days of continuous electrolysis, was 2.1 × 10 11 tritium atoms, compared with a background of 4 × 10 9 tritium atoms. The concentration of tritium and its axial distribution in the Pd were determined and concentrations of up to 9 × 10 10 atoms/g Pd were found compared with a maximum background of 5 × 10 8 atoms g −1. The T/D ratio in the Pd is about 100 times larger than in the electrolyte or gas and indicates that tritium generation occurs in the Pd interior rather than at its surface. No tritium generation was observed in two other types of Pd electrodes in D 2SO 4, despite the attainment of D/Pd ratios near 1:1. Thus high D/Pd ratios appear to be a necessary but not sufficient condition for tritium generation in D 2SO 4 electrolysis.