Tritium behavior at formation of re-deposition layer from plasma facing material

为了了解聚变反应堆中面向等离子体材料再沉积层形成时的氚行为，本研究利用射频氢等离子体反应堆进行了实验研究，得到了新的观察结果：(1)石墨或钨的再沉积层具有多孔结构，并且含有较多的氢。本研究中观测到的H/C比为0.1-0.3，H/W比约为0.1。众所周知，氢在钨中的溶解度可以忽略不计。因此，本研究的观察结果表明，聚变反应堆中形成的粉尘中的氚含量可能比目前预期的要高得多。(2)观察了石墨和钨的共沉积层中捕获的氢气量。共沉积层的释放行为与单组分再沉积层的释放行为不同。(3)氢等离子体的重定位层比氢等离子体大好几倍。这表明DT等离子体可能比氢等离子体产生更厚的再沉积层。(4)建立了再沉积层形成速度的经验公式。

In order to understand the tritium behavior at formation of re-deposition layer of plasma facing materials in a fusion reactor, experimental research has been performed using RF hydrogen plasma reactors in this study and new observations are obtained.(1)The re-deposition layer of graphite or tungsten has the porous construction and it contains rather large amount of hydrogen. The H/C ratio observed in this study is 0.1-0.3, and that of H/W is about 0.1. It is known that solubility of hydrogen in tungsten is negligibly small. Accordingly, observation in this study suggests that dusts formed in fusion reactor may contain much more tritium than expected at present.(2)The amount of hydrogen trapped in the co-deposition layer of graphite and tungsten is observed. The release behavior from co-deposition layer is different from the behavior of the re-deposition layer of single component.(3)The deuterium plasma gives several times larger re-position layer than the hydrogen plasma. This suggests that the DT plasma may give thicker re-deposition layer than the hydrogen plasma.(4).The empirical equation for the forming rate of re-deposition layer is made.