Helium release from 19-year-old palladium tritide

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 3He concentrations inside the solid samples. Two tritide samples replenished with 2100 kPa of tritium throughout their lifetime started to copiously outgas 3He 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 3He at a helium/palladium ratio of 0.36 to 0.37 at about one-eight 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 1.8x105 mol/m3, in agreement with nuclear magnetic resonance data. (orig.)