Tritium accumulation and release from LiTiO during long-term irradiation in the WWR-K reactor

WWR-Kでの長期照射試験中のLiTiOからのトリチウム蓄積と放出特性

Tazhibayeva, I.*; Beckman, I.*; Shestakov, V.*; Kulsartov, T.*; Chikhray, E.*; Kenzhin, E.*; Kuykabaeva, A.*; 河村 弘; 土谷 邦彦 

Tazhibayeva, I.*; Beckman, I.*; Shestakov, V.*; Kulsartov, T.*; Chikhray, E.*; Kenzhin, E.*; Kuykabaeva, A.*; Kawamura, Hiroshi; Tsuchiya, Kunihiko

高リチウム燃焼(最高23%)時におけるLi濃縮LiTiOからのトリチウム放出に関するデータが世界で初めて得られた。本研究では、トリチウム放出試験より、提案した計算手法に基づいて、トリチウム放出過程を調べた。照射試験の間、トリチウムはLiと中性子の核反応により生成し、LiTiOからのトリチウム放出量が加熱・冷却を通じて連続的に測定された。LiTiOからのガス放出パラメータは、トリチウム放出率,材料中のトリチウム保持,保持時間,HTの活性化エネルギー,体積拡散としてのTの活性化エネルギーとした。この結果、トリチウム放出過程がトリチウム体積拡散律束であること,Liの燃焼によりトリチウム放出の活性化エネルギーが減少することなどがわかった。

For the first time the data was obtained on tritium release from Li-enriched (96%) lithium metatitanate under high lithium burn-up (up to 23%). Proposed mathematics and software of the reactor experiments allowed to interpret the experimental results of tritium release study. Tritium was continuously generated as a result of the nuclear reaction of lithium-6 and thermal neutrons under variable thermal impacts (graduated heating and cooling) on lithium metatitanate LiTiO. Main gas release parameters were calculated in order to assess acceptability of the use of lithium metatitanate granules in tritium breeders; the parameters are as follows: gas release rate, tritium retention in the materials, retention time, activation energy of thermal desorption HT, activation energy of volume diffusion T, as well as corresponding pre-exponential (frequency) indexes. It was discovered that the tritium release process is mainly controlled by tritium volume diffusion, however, capture of tritium by the point defects and tritium molization at the material's surface played the certain role in the process as well. It was discovered that as lithium is burnt-up, the activation energy of tritium release decreases and tends to a constant value under high lithium-6 burn-up.