Helium release from 19-year-old palladium tritide

Abstract Eleven nineteen-year-old samples of palladium deuteride-tritide originally placed under 100 kPa of tritium have been monitored for pressure during their lifetimes. A model has been constructed, which relates the pressure to the tritium and 3 He concentrations inside the solid samples. Two tritide samples replenished with 2100 kPa of tritium throughout their lifetime started to copiously outgas 3 He at a helium/palladium atom ratio of 0.50 to 0.55. Four other samples were originally reacted with pure tritium and never replenished. These started to outgas mainly 3 He at a helium/palladium ratio of 0.36 to 0.37 at about one-eighth the rate of the replenished samples. All six samples started their outgassing at 6000 days. Two samples were made with D-T and replenished with tritium. Neither outgassed although the helium/palladium ratio is presently about 0.4. Three samples were also made with D-T and never replenished, and no outgassing was seen up to a helium/palladium ratio of 0.24. From the change in the volumes of two samples, we have calculated a helium bubble gas density of 1.8 × 10 5 mol / m 3 , in agreement with nuclear magnetic resonance data.