Zeng Linlin, Zhang Mingjun, Zhu Lixiao, Zeng Youshi, Wang Chenxu, Zhou He, Fan Dongliang, Liu Wenguan, Deng Ke, Liu Wei
Shanghai Institute of Applied Physics Chinese Academy of Sciences, Shanghai 201800, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
ACS Omega. 2025 Sep 14;10(37):42534-42547. doi: 10.1021/acsomega.5c04042. eCollection 2025 Sep 23.
Carrier gas plays a crucial role in the thermal treatment method for removing tritium from irradiated nuclear graphite. Experiments studies have demonstrated that the addition of steam can enhances tritium removal from graphite, while the mechanism of the promotion remained unclear. In this study, based on density functional theory (DFT), we investigated the mechanisms of tritium removal from graphite using HO as the carrier gas, focusing on two primary processes: direct isotope exchange and adsorption-desorption methods. The activation energy for tritium removal from graphite via direct isotope exchange ranges from 3.18 to 5.10 eV, which is associated with the strength of the C-T bond in graphite. The adsorption-desorption mechanism involves the adsorption of HO in the form of hydroxyl group and hydrogen, followed by desorption of hydroxyl group together with tritium preadsorbed in graphite matrix. The activation energy for this process is dependent on the adsorption activation energy of HO, ranging from 2.01 to 3.52 eV. Following the adsorption-desorption method, tritium in nuclear graphite is primarily desorbed as tritiated water (HTO), and the activation energy was found to be significantly lower than that of direct isotope exchange. Therefore, the tritium adsorbed in nuclear graphite would be desorbed as HTO after combining with the hydroxyl group in steam. These findings study provide valuable theoretical guidance for the removal of tritium from irradiated nuclear graphite through thermal treatment methods.
载气在从辐照核石墨中去除氚的热处理方法中起着至关重要的作用。实验研究表明，添加蒸汽可以增强从石墨中去除氚的效果，但其促进机制仍不清楚。在本研究中，基于密度泛函理论（DFT），我们研究了以HO作为载气从石墨中去除氚的机制，重点关注两个主要过程：直接同位素交换和吸附 - 解吸方法。通过直接同位素交换从石墨中去除氚的活化能范围为3.18至5.10 eV，这与石墨中C - T键的强度有关。吸附 - 解吸机制涉及HO以羟基和氢的形式吸附，随后羟基与预先吸附在石墨基质中的氚一起解吸。该过程的活化能取决于HO的吸附活化能，范围为2.01至3.52 eV。按照吸附 - 解吸方法，核石墨中的氚主要以氚化水（HTO）的形式解吸，并且发现活化能明显低于直接同位素交换的活化能。因此，吸附在核石墨中的氚在与蒸汽中的羟基结合后将以HTO的形式解吸。这些研究结果为通过热处理方法从辐照核石墨中去除氚提供了有价值的理论指导。
