Main results of long-term high lithium burn-up irradiation test in LiTiO and LiTiO + 5mol% TiO ceramics for solid breeding blanket

固体増殖ブランケットのためのLiTiOと5mol% TiO添加LiTiOセラミックスの高Li燃焼照射試験に関する成果

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

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

本論文は、高Li燃焼(20-23%)時におけるLiを濃縮したLiTiOと5mol% TiO添加LiTiOセラミックスからのトリチウム放出に関するものである。中性子照射は、400-900C5350時間の条件でWWR-K炉にて行った。照射後試験として、これらのセラミックスの残留トリチウム量、リチウム燃焼による影響、機械的特性、密度、微細構造の変化、熱特性などを測定した。その結果、低い照射温度で照射したセラミックスはLi燃焼により機械的特性が小さくなること、原子炉運転中に放出されるトリチウム量は照射が進むにつれていくぶん増加するが、単位あたりのトリチウム量は照射期間に依存しないことなどを明らかにした。このように、リチウム燃焼に従って機械的特性は若干小さくなるが、LiTiOからのトリチウム放出は20%Li燃焼時までは変化がないことがわかった。

The paper contains the results of the integrated material study of lithium ceramics LiTiO and LiTiO + 5mol% TiO enriched by Li (up to 96%). The ceramics were irradiated in the WWR-K reactor during 5350 hours under the temperature range of 400-900С with study of tritium generated during irradiation. The post-radiation studies allowed to determine quantity of residual tritium, degree of lithium burn-up, strength characteristics of lithium ceramic with the lithium burn-up up to 20-23%, ceramic density, changes in the sample microstructure, heat characteristic of the ceramics and their changes due to neutron irradiation, changes of element and phase composition of the samples, and the parameters of tritium release from lithium ceramics. It was showed that the ceramic samples irradiated under lower temperature are characterized by sufficiently small degree of Li burn-up. It was established that irradiation resulted in softening of lithium ceramic; at that the effect is more prominent for lower irradiation temperatures. The quantity of tritium released during a reactor's campaign is somewhat increasing with increase of a campaign's number, but quantity of tritium released from lithium titanate per hour doesn't depend on duration of irradiation. Thus, despite of lithium burn-up, tritium flow from lithium titanate isn't changed during long-term irradiation since reduction of the strength of the tritium source (due to lithium burn-up) is compensated by increase in mobility of tritium in defect lattice. The obtained results showed that a breeder on the basis of Li-enriched lithium titanate can be a permanent source of tritium during one year of reactor operation at least.