Long-term measurement of helium-3 release behavior from zirconium-cobalt tritide

Abstract

Release behavior of helium-3 ( 3He: tritium β-decay product) from zirconium-cobalt (ZrCo) tritide has been investigated for three and a half years as a part of the long-term reliability and safety evaluations of ZrCo for tritium (T) use. The release fractions of 3He from ZrCo tritide were constantly less than 3% for the initial 2 yr under the following conditions: holding temperatures 293–523 K, initial atom ratios ( T ZrCo ) 0.3–1.5, and numbers of hydrogenation-dehydrogenation cycles before tritiation 1–10. After 2 yr, however a 3He release fraction (293 K, ZrCoT 1.3, 1 cycle) has been increasing more than 25% and the ratio of residual 3He accumulated in tritide and ZrCo ( 3He ZrCo ) is about 0.2. From the above point of view, two years would be a safe storage period of ZrCo tritide without any care under these conditions.