高温下GH3535合金中的氢同位素扩散渗透效应分析

Flibe具有熔点低、中子性能好、沸点高等特点,是未来大型氟盐冷却高温堆的主要候选氟盐冷却剂之一,在堆芯中与中子相互作用后会导致一定量的副产物氚产生。根据哈氏N合金的成分,钍基熔盐堆核能系统(TMSR)发展了GH3535合金,作为未来大型熔盐堆的主要候选结构材料。本实验中采用GH3535合金为试样,通过使用压力差驱动原理搭建的氢同位素扩散渗透装置,试验测得了400~800℃的温度下氢气、氘气在该合金中的渗透系数、扩散系数、Sieverts常数等主要参数。实验结果表明,氢气与氘气在GH3535合金中的扩散渗透机理均属于基体扩散控制过程,扩散渗透过程中氢气、氘气的主要参数与相应温度关系均符合阿累尼乌斯公式。对于不同质量数的氢同位素原子,拟合后渗透系数和扩散系数的指前因子之比分别为1.4:1和1.2:1,扩散和渗透过程中的激活能也非常接近,符合经典扩散理论的同位素效应,可以估算得到氚在GH3535合金中扩散渗透时的主要参数大约为氢的1/3(1/2),并可能用于氚在熔盐堆中的分布计算。

Analysis of hydrogen isotope effect during the permeation through GH3535 alloy at high temperature

FLibe is one of the main candidate coolants which would be used in the large output Fluoride salt cooled High-temperature Reactors (FHRs)because it has good neutron properties,low melting point,high boiling point,and so on. According to the main compositions of Hastelloy N alloy,the thorium based molten salt reactors (TMSRs ) have developed the GH3535 alloy, which would be used as the main structural materials of large output molten salt reactors in the future. In this study,the permeation facility of hydrogen isotopes,which was set up by the methods of gas drivenpermeation,was used to examine the main transport parameters of hydrogen or deuteriumin GH3 5 3 5 alloy at the temperature of 400 ~ 800 ℃. From the power lawrelationship between the steady-state hydrogen flux and the loading pressure, thediffusive process of hydrogen and deuterium in the specimen belongs to the surfacelimitedregime. For the permeation process of different hydrogen isotopes throughGH3 5 3 5 alloy,the main parameters of permeability,diffusivity and Sieverts’constantall showed an Arrhenius type dependency with temperature,as foreseen in theory. Theratios of permeation and diffusivity for hydrogen and deuterium were about 1.4∶1 and1.2 ∶1,r espectively. It was shown the consistence with the prediction of the classicaldiffusion theory known as the “i sotope effect ”. The main diffusive parameters(permeability or diffusivity)of tritium in GH3 5 3 5 alloy should beevaluated by a factorof 1/3 compared with hydrogen and would be used to calculate the distribution oftritium in TMSRs.