Release Behavior of Decay Helium from Zirconium-Cobalt Tritide

In order to discuss the long-term reliability and safety of zirconium-cobalt alloy for tritium use, the release behavior of decay helium from ZrCo tritide has been investigated for one and a half years with a radio-gaschromatograph. In this paper, the results show that the release fractions of the total decay {sup 3}He 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 {sup 3}He was not released even if ZrCo was heated to 873 K, though most of the tritium was released. It became clear that the decay {sup 3}He was quite immovable in ZrCo tritide under these experimental conditions.