Direct Removal of Tritium from Mixture Gas by Alloy Getter with Functional Surfaces

聚变反应堆堆芯废气中的氚、氢与氦等杂质共存。从安全评价和氚经济性的角度来看，从氦等气体中分离氚是一项重要的任务。用低平衡氚压力的合金吸气剂直接除氚是一种安全有效的氚分离方法。然而，氧和碳等杂质的中毒会降低氚的去除效率。本项目的目标是探索表面改性技术，以显著提高吸气剂的抗中毒耐久性。以锆镍为模型材料，于2001年采用化学镀技术进行了Pd涂层。将样品暴露在含有H2O、CO2和O2的Ar气体中，在373~573K的温度范围内，研究了样品吸氢速率的退化。在473K以上，Pd涂层显著提高了抗中毒的耐久性。需要强调的是，在573K时，Pd涂层的样品没有明显的退化，而没有Pd涂层的样品在暴露2 h后完全失活。选择溅射沉积作为Pd涂层的新工艺。为了研究表面杂质对氢同位素吸收的影响，考察了空气中的活化行为。Pd涂层的样品在423K真空加热活化，而没有Pd涂层的样品需要在873K下活化。这一观察表明，在室温下暴露在空气中，Pd涂层样品的表面没有形成稳定的氧化物。因此，要求在低温下有很高的耐用性。购买的质量分析仪被用于分析Ar、Dh和氢气中的杂质。

Tritium and deuterium coexist with helium and other impurities in exhaust gas from fusion reactor core. The separation of tritium from He and other gases is important task from the viewpoints of safety assessment and tritium economy. Direct removal of tritium by alloy getters with low equilibrium tritium pressure is safe and efficient method for tritium separation. The efficiency for tritium removal, however, can be degraded by poisoning by impurities such oxygen and carbon. The objective of the present project is to explore the surface modification technique to drastically improve the durability of getters against poisoning. ZrNi was selected as model material.Pd coating was carried out in 2001 with electroless plating technique. Specimen was exposed to argon gas containing H_2O, CO_2 and O_2, and degradation in deuterium absorption rate was examined at temperatures from 373 to 573 K. The durability against poisoning was significantly improved by Pd coating above 473 K. It should be emphasized that no significant degradation was observed for Pd coated specimen at 573 K, whereas the specimen without Pd coating was completely deactivated by 2 h exposure.In 2001, attention was focused on improvement of durability at lower temperatures. Sputter deposition was selected as new Pd coating technique. The activation behavior after exposure to air was examined to investigate the influence of surface impurities on absorption of hydrogen isotopes. The Pd coated specimen was activated by heating in vacuum at 423 K, whereas activation at 873 K was necessary for the specimen without Pd coating. This observation indicated that no stable oxide was formed at the surface of Pd coated specimen by exposure to air at room temperature. So, high durability at low temperature is expected.The mass analyzer purchased was used to analyze impurities in argon, deuterium and hydrogen gases.