Effect of purge gas oxidizing potential on tritium release from Li-ceramics and on its permeation through 316L SS clads under irradiation (TRINE experiment)

Abstract The effect of red—ox potential of helium purge gas (variously doped with H 2 , H 2 O and O 2 ) was examined on tritium release from Li-ceramics (LiAlO 2 and Li 2 ZrO 3 pellets) and on its permeation rate through the 316L stainless steel clads (bare and coated) held at 500°C. Decreasing the H 2 content from 1000 vpm (reference ‘R’ gas mixture) to 100 vpm, and substituting H 2 O for H 2 , the tritium permeation rate (ca. 1.410 10 atoms cm −2 s −1 in R-gas) increases. Tritium inventories in the Li ceramics were increased too. When a strong oxidizing purge (1000 vpm O 2 added to He containing 100 vpm H 2 O) was used, a retention time (τ) of two days at 400°C was measured for Li 2 ZrO 3 . In this oxidizing environment the tritium permeation loss dropped by a factor five for the uncoated capsules while an aluminide coating became a very effective tritium barrier: tritium permeation flux at 550°C fell below the measurable limit.