Abstract

The SCALE code system was used to model, deplete, and compare several different tri-structural isotropic (TRISO)–fueled reactor designs: a helium-cooled prismatic reactor, a helium-cooled pebble-bed reactor (PBR), and a fluoride-lithium-beryllium (FLIBE) molten-salt-cooled PBR. The purpose of this comparison was to understand how differences in the reactor designs affect the radioactivity of the fuel after discharge and whether those differences are significant. First, the various reactor designs were built and depleted in the TRITON module for each design and fuel enrichment. Then, the TRITON outputs were used to create burnup-dependent reactor libraries. These libraries were then used by ORIGEN to determine the activities of discharged fuel for each reactor, which were compared to generic Westinghouse 17 × 17 fuel.

Overall, the results showed that short-term activities are dominated by reactors with higher operating powers, and the reactor type, initial fuel enrichment, and maximum burnup are of only secondary importance. Although this analysis only focuses on activities in Becquerels, these dependencies are consistent with the expected behavior of decay heat. However, analysis of long-term time periods post irradiation shows that the reactor type and maximum burnup have strong impacts on the activities; initial fuel enrichment has a secondary impact while operating power is inconsequential.

These results would be useful for analyses, such as dose assessment and modeling in postrelease scenarios, normal fuel handling operations, and spent fuel transport, storage, and disposal. Of particular interest, the results in this technical note show that analyses that focus on spent nuclear fuel of advanced reactors need to consider each parameter carefully. Unsurprisingly, if the correct operating power is not used in short-term analyses, the results will not be correct. Perhaps unexpectedly, however, if the correct reactor type is not used, then the long-term results will also be incorrect, especially for areas such as permanent disposal. Even though this technical note focuses on the total activity of nuclear fuel, it provides initial results on the effects of various input parameters and also provides a framework to extend the work into other analyses of spent fuel from advanced reactors, especially those employing TRISO fuel.

摘要

SCALE 代码系统用于建模、耗尽和比较几种不同的三结构各向同性 (TRISO) 燃料反应堆设计：氦冷却棱柱反应堆、氦冷却球床反应堆 (PBR) 和氟化物反应堆。铍锂 (FLIBE) 熔盐冷却 PBR。这种比较的目的是了解反应堆设计的差异如何影响排放后燃料的放射性，以及这些差异是否显着。首先，针对每种设计和燃料浓缩，在 TRITON 模块中建造和耗尽了各种反应堆设计。然后，TRITON 输出用于创建与燃耗相关的反应堆库。然后 ORIGEN 使用这些库来确定每个反应堆排放燃料的活动，并将其与通用西屋公司 17 × 17 燃料进行比较。

总体而言，结果表明，短期活动以运行功率较高的反应堆为主，反应堆类型、初始燃料浓缩和最大燃耗只是次要的。尽管此分析仅关注贝克勒尔的活动，但这些相关性与衰变热的预期行为一致。然而，对辐照后长期时间段的分析表明，反应堆类型和最大燃耗对活动有很大影响；初始燃料浓缩具有次要影响，而运行功率无关紧要。

这些结果将有助于分析，例如释放后情景中的剂量评估和建模、正常燃料处理操作以及乏燃料运输、储存和处置。特别令人感兴趣的是，本技术说明中的结果表明，针对先进反应堆乏核燃料的分析需要仔细考虑每个参数。不出所料，如果在短期分析中没有使用正确的运行功率，结果将不正确。然而，也许出乎意料的是，如果没有使用正确的反应堆类型，那么长期结果也将是不正确的，特别是对于永久性处置等领域。尽管本技术说明侧重于核燃料的总活性，