Kubiński Wojciech R, Ostrowski Jan K, Fornalski Krzysztof W
Faculty of Physics, Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warszawa, Poland.
National Centre for Nuclear Research (NCBJ), ul. Andrzeja Sołtana 7/3, 05-400 Otwock-Świerk, Poland.
Entropy (Basel). 2024 Dec 22;26(12):1124. doi: 10.3390/e26121124.
This paper analyzes the behavior of the entropy of a nuclear fuel rod under deep burnup conditions, beyond standard operational ranges, reaching up to 60 years. The evolution of the neutron source distribution in a pressurized water reactor (PWR) fuel pin was analyzed using the Monte Carlo method and Shannon information entropy. To maintain proper statistics, a novel scaling method was developed, adjusting the neutron population based on the fission rate. By integrating reactor physics with information theory, this work aimed at the deeper understanding of nuclear fuel behavior under extreme burnup conditions. The results show a "U-shaped" entropy evolution: an initial decrease due to self-organization, followed by stabilization and eventual increase due to degradation. A minimum entropy state is reached after approximately 45 years of pin operation, showing a steady-state condition with no entropy change. This point may indicate a physical limit for fuel utilization. Beyond this point, entropy rises, reflecting system degradation and lower energy efficiency. The results show that entropy analysis can provide valuable insights into fuel behavior and operational limits. The proposed scaling method may also serve to control a Monte Carlo simulation, especially for the analysis of long-life reactors.
本文分析了核燃料棒在深燃耗条件下（超出标准运行范围，长达60年）的熵行为。利用蒙特卡罗方法和香农信息熵分析了压水堆（PWR）燃料棒中中子源分布的演变。为了保持适当的统计量，开发了一种新颖的缩放方法，根据裂变率调整中子数量。通过将反应堆物理与信息论相结合，这项工作旨在更深入地了解极端燃耗条件下的核燃料行为。结果显示出“U形”熵演变：由于自组织导致初始下降，随后稳定，最终由于退化而增加。燃料棒运行约45年后达到最小熵状态，显示出无熵变化的稳态条件。这一点可能表明燃料利用的物理极限。超过这一点，熵上升，反映系统退化和能量效率降低。结果表明，熵分析可为燃料行为和运行极限提供有价值的见解。所提出的缩放方法还可用于控制蒙特卡罗模拟，特别是对于长寿命反应堆的分析。
