Abstract Recent advances in nuclear fuel materials research, particularly on the topic of accident-tolerant fuels, have brought up potential opportunities for expanding the operating envelope of existing light water reactors. As many of the performance improvements offered by these technologies may be most fully realized by increasing fuel enrichment beyond the standard 5% limit, this paper examines the potential reactor performance and fuel cycle performance of low-enriched uranium oxide fueled light water reactors by generically considering pressurized water reactors with 235U enrichment from 5 to 7%. Advanced cladding, including accident-tolerant cladding, has the potential to increase fuel burnup limits related to hydrogen in the cladding that coincide with those limits associated with end-of-life reactivity. Therefore, higher enrichment will be necessary in order to realize the higher fuel burnups. This work includes evaluation of the fuel cycle length, discharge burnup, reactivity coefficients, and fuel cycle performance, including radioactive waste and environmental impact metrics per unit energy generated. The analysis was performed using the evaluation metrics from the US Department of Energy Office of Nuclear Energy Fuel Cycle Evaluation and Screening Study. The reactor performance and safety analysis show that enrichments between 5 and 7% would have similar fuel temperature and moderator temperature coefficients. However, the soluble boron coefficient would decrease in magnitude, requiring more corrosive boric acid in the coolant or other methods of reactivity control during the fuel cycle. At these higher enrichments the maximum burnup at the rim of the fuel pellet would increase by almost a factor of two, which is expected to impact the formation of high-burnup structure in the fuel and the corresponding thermo-mechanical fuel properties. The fuel cycle performance assessment shows that increasing enrichment reduces the quantity of high-level waste disposed per unit energy generated, but it increases the natural resource requirements normalized to a gigawatt-electricity-per-year basis. Another impact is the slightly higher discharge burnup, resulting in somewhat different activity levels of the spent nuclear fuel and high-level waste radioactivity at 100 and 100,000 years after fuel discharge. The environmental impacts—including land use, water use, carbon emission, and radiological exposure—are of the same magnitude per unit energy generated. However, the impacts are distributed differently. Less than 5% enrichment has marginally more impact on the back-end of the fuel cycle, and greater than 5% enrichment has marginally more impact on the front-end of the fuel cycle. Ultimately, no neutronic or reactor safety hindrances to employing light water reactor fuel with enrichments greater than 5% are identified; given the achievable reactor performance benefits with advanced fuels, further practical exploration of increased enrichment fuel is recommended.

中文翻译：

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235U浓缩度5%以上轻水反应堆燃料的反应堆和燃料循环性能

摘要 核燃料材料研究的最新进展，特别是在容灾燃料方面的进展，为扩大现有轻水反应堆的运行范围带来了潜在的机会。由于这些技术提供的许多性能改进可以通过将燃料浓缩度提高到超过标准的 5% 限制来最充分地实现，因此本文通过一般性考虑来检验低浓缩铀氧化物燃料轻水反应堆的潜在反应堆性能和燃料循环性能235U 浓缩度从 5% 到 7% 的压水反应堆。先进的包壳，包括容灾包壳，有可能增加与包壳中氢相关的燃料燃烧限制，这与与寿命终止反应相关的限制一致。所以，为了实现更高的燃料燃烧率，需要更高的浓缩度。这项工作包括评估燃料循环长度、排放燃耗、反应系数和燃料循环性能，包括放射性废物和产生的每单位能量的环境影响指标。该分析是使用美国能源部核能燃料循环评估和筛选研究办公室的评估指标进行的。反应堆性能和安全分析表明，5% 和 7% 之间的浓缩将具有相似的燃料温度和慢化剂温度系数。然而，可溶性硼系数会降低幅度，在燃料循环期间需要在冷却剂或其他反应性控制方法中使用更具腐蚀性的硼酸。在这些较高的浓缩度下，燃料芯块边缘的最大燃耗将增加近两倍，预计这将影响燃料中高燃耗结构的形成和相应的热机械燃料特性。燃料循环性能评估表明，增加浓缩减少了每产生的单位能量处理的高放废物量，但它增加了自然资源需求，标准化为每年千兆瓦电力。另一个影响是排放燃耗略高，导致在燃料排放后 100 年和 100,000 年，乏核燃料的活动水平和高放射性废物的放射性水平略有不同。环境影响——包括土地利用、水资源利用、碳排放、和放射暴露——产生的每单位能量具有相同的量级。但是，影响的分布不同。低于 5% 的浓缩对燃料循环后端的影响稍大，高于 5% 的浓缩对燃料循环前端的影响稍大。最终，没有发现使用浓缩度大于 5% 的轻水反应堆燃料的中子或反应堆安全障碍；鉴于使用先进燃料可实现反应堆性能优势，建议进一步实际探索增加浓缩燃料。未发现使用浓缩度大于 5% 的轻水反应堆燃料存在中子或反应堆安全障碍；鉴于使用先进燃料可实现反应堆性能优势，建议进一步实际探索增加浓缩燃料。未发现使用浓缩度大于 5% 的轻水反应堆燃料存在中子或反应堆安全障碍；鉴于使用先进燃料可实现反应堆性能优势，建议进一步实际探索增加浓缩燃料。