Abstract Due to the presence of beryllium-bearing salts, fluoride-salt cooled high-temperature reactors (FHRs) are expected to have higher production of delayed photoneutrons than other common power reactor systems which may impact transient behavior. New methods for computationally quantifying the characteristics of delayed photoneutrons using Monte Carlo particle transport, including absolute fraction, effective fraction, and group decay constants, are outlined. These methods are validated where possible against existing data from CANDU reactors, and then used to make a best-estimate characterization of the delayed photoneutron effect in a prototypical FHR design. It is found that delayed photoneutrons have a worth of approximately 9 pcm in the reference FHR system, and that their importance is slightly higher than that of fission neutrons due mostly to their softer spectrum. Existing emission group structures from literature have been compared to computational data and found to be lacking, particularly in their representation of groups with short half-lives. Therefore, a new 13-group structure is proposed for use in FHR dynamic calculations.

中文翻译：

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氟化盐冷却高温反应堆中的光中子产生和表征

摘要 由于含铍盐的存在，氟化盐冷却高温反应堆 (FHR) 预计比其他可能影响瞬态行为的常见动力反应堆系统具有更高的延迟光中子产量。概述了使用蒙特卡罗粒子传输计算量化延迟光中子特性的新方法，包括绝对分数、有效分数和群衰减常数。这些方法在可能的情况下根据来自 CANDU 反应堆的现有数据进行验证，然后用于对原型 FHR 设计中的延迟光中子效应进行最佳估计表征。发现延迟光中子在参考 FHR 系统中的价值约为 9 pcm，并且它们的重要性略高于裂变中子，主要是因为它们的光谱较软。文献中现有的发射基团结构与计算数据进行了比较，发现缺乏，特别是在它们对短半衰期基团的表示方面。因此，提出了一种新的 13 组结构用于 FHR 动态计算。