RELEASE BEHAVIOR OF DECAY HELIUM FROM ZIRCONIUM-COBALT TRITIDE

In order to discuss the long-term reliability and safety of zirconium-cobalt (ZrCo) alloy for tritium (T) use, the release behavior of decay helium (He-3) from ZrCo tritide has been investigated for one and a half years with a radio-gaschromatograph. The results show that the release fractions of the total decay He-3 in ZrCo tritide are less than 3 % and has been almost constant for 18 months under the following conditions: the operating temperatures = 293 approximately 523 K, the atom ratios (T/ZrCo) = 0.3 approximately 1.4, and the number of hydrogenation-dehydrogenation cycles before tritiation = 1 approximately 10. Moreover, residual decay He-3 was not released even if ZrCo was heated to 873 K, though most of the tritium was released. It became clear that the decay He-3 was quite immovable in ZrCo tritide under these experimental conditions.