Abstract Further understanding of tritium transport mechanisms in the combined molten fluoride salt and graphite environment is necessary for the design and licensing of a Fluoride-Salt-Cooled High-Temperature Reactor (FHR). The three in-core fluoride salt irradiations completed at the Massachusetts Institute of Technology Reactor (MITR) are a useful parallel for studying transport phenomena expected in a FHR environment. During the irradiations, evolution of tritium from the flibe salt was monitored and compared to the calculated total generation rate. A difference of 22 ± 10% between the integrated calculated tritium generation rate and the total release was measured for the third MITR irradiation (FS-3). The fraction of tritium which was not released from the salt could be explained by tritium retention in graphite. For post irradiation examination, a thermal desorption furnace was used to heat nuclear graphite samples in order to release and measure retained tritium. The desorption analysis in this work utilized seven subsections of graphite from the second salt irradiation (FS-2); three from a disc of IG-110U and four from ARB matrix graphite. Observed desorption versus temperature as well as total tritium content in the samples after irradiation indicate that the graphites were not volumetrically saturated with tritium, but rather tritium retention was likely limited to the near-surface region. Measurements of the samples resulted in 2.90 ± 0.29 μCi/mm2 of tritium retained by IG-110U and 1.83 ± 0.31 μCi/mm2 for ARB during the 300 h FS-2 in-core irradiation. Based on the desorption measurements, the estimated total tritium retention in graphite from the FS-2 samples is consistent with the tritium release measurements from the FS-3 experiment.

中文翻译：

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核内氟化盐辐照产生、释放和保留氚

摘要 进一步了解熔融氟化盐和石墨环境中的氚传输机制对于氟化盐冷却高温反应堆 (FHR) 的设计和许可是必要的。在麻省理工学院反应堆 (MITR) 完成的三个堆芯氟化盐辐照是研究 FHR 环境中预期传输现象的有用平行。在辐照过程中，监测从氟利贝盐中析出的氚，并与计算出的总生成率进行比较。对于第三次 MITR 辐照 (FS-3)，测量到的积分计算氚生成率和总释放之间的差异为 22 ± 10%。未从盐中释放的氚的比例可以用氚保留在石墨中来解释。对于辐照后检查，使用热解吸炉加热核石墨样品，以释放和测量残留的氚。这项工作中的解吸分析利用了来自第二次盐辐射 (FS-2) 的七个石墨分段；三个来自 IG-110U 圆盘，四个来自 ARB 基体石墨。观察到的解吸与温度以及辐照后样品中的总氚含量表明，石墨并未被氚体积饱和，而是氚保留可能仅限于近表面区域。在 300 小时 FS-2 芯内照射期间，样品的测量结果表明 IG-110U 保留了 2.90 ± 0.29 μCi/mm2 的氚和 ARB 保留的 1.83 ± 0.31 μCi/mm2。根据解吸测量，