In general, a nuclear core design process is divided into two subsequent phases, namely the fuel lattice design phase, and followed by the full core design phase such as for the light water reactor (LWR). The optimal design parameters obtained from the fuel design phase can be used in a straightforward manner in the full core design phase since the neutron mean free path is much smaller than the fuel assembly dimensions. Unfortunately, the above-mentioned favorable situation may not be applicable for a high-temperature gas-cooled reactor (HTGR) design process. In this paper, for the HTGR design process, we propose a new technique based on the neutron importance concept to make a projection of the optimal design parameters obtained from the fuel design phase to the full core design phase so that the optimization works required in the full core design phase can be significantly reduced. The proposed technique is implemented in the Japanese High-Temperature Engineering Test Reactor to find the optimal fuel composition that can achieve an average core discharge burnup of 80 GWd/tU using single-batch and multi-batch refueling schemes. Important core neutronics parameters, such as reactivity coefficient and power profiles, are also discussed. Moreover, the impact of the axial shuffling scheme on the fuel compact fuel temperature is also analyzed.

通常，核芯设计过程分为两个后续阶段，即燃料晶格设计阶段，然后是完整的堆芯设计阶段，例如轻水反应堆 (LWR)。由于中子平均自由程远小于燃料组件尺寸，因此从燃料设计阶段获得的最佳设计参数可以直接用于整个堆芯设计阶段。不幸的是，上述有利情况可能不适用于高温气冷堆 (HTGR) 设计过程。在本文中，对于 HTGR 设计过程，我们提出了一种基于中子重要性概念的新技术，将燃料设计阶段获得的最佳设计参数投影到全堆芯设计阶段，从而可以显着减少全堆芯设计阶段所需的优化工作。所提出的技术在日本高温工程试验堆中实施，以寻找最佳燃料成分，使用单批和多批换料方案可实现平均 80 GWd/tU 的堆芯放电燃耗。还讨论了重要的核心中子学参数，例如反应系数和功率分布。此外，还分析了轴向改组方案对燃料紧凑型燃料温度的影响。所提出的技术在日本高温工程试验堆中实施，以寻找最佳燃料成分，使用单批和多批换料方案可实现平均 80 GWd/tU 的堆芯放电燃耗。还讨论了重要的核心中子学参数，例如反应系数和功率分布。此外，还分析了轴向改组方案对燃料紧凑型燃料温度的影响。所提出的技术在日本高温工程试验堆中实施，以寻找最佳燃料成分，使用单批和多批换料方案可实现平均 80 GWd/tU 的堆芯放电燃耗。还讨论了重要的核心中子学参数，例如反应系数和功率分布。此外，还分析了轴向改组方案对燃料紧凑型燃料温度的影响。