The Gas-cooled Fast Reactor is an advanced concept selected to be part of the fourth generation of nuclear reactors. Before its development, the construction of the experimental demonstration reactor ALLEGRO is planned. Given the current interest in this innovative system, a neutronic study of the ALLEGRO reactor core is performed using the Monte Carlo Serpent calculation code and the deterministic ERANOS code. A detailed description of the core design and ceramic fuel composition is provided. To reduce the computational cost of the simulations for future applications, different cases are analyzed using different computational options in the TGV/VARIANT module and a 7-group energy structure. To validate the ERANOS models, the results are compared with the three-dimensional heterogeneous reference model developed in Serpent. The main parameters of the core, at the beginning of life, are calculated, such as the k-eff value, flux and power distributions, Doppler constant, effect of helium density on reactivity and the β-eff value. The main discrepancies in the results correspond to the diffusion and simplified transport calculations, due to the low density of helium. By using the 7-group structure, it was possible to reduce the calculation time with a reduced penalty in the precision of the results. Furthermore, the best agreement was obtained, with respect to the Serpent model, for the transport calculation (P₃) with the 7-energy group structure. The k-eff and fuel isotope mass evolution during burnup is analyzed assuming an operating time of 365 days. The relative fuel fraction at the beginning and end of cycle, the breeding ratio and the average burnup are also given.

气冷快堆是一种先进的概念，被选为第四代核反应堆的一部分。在开发之前，计划建造实验示范反应堆 ALLEGRO。鉴于目前对这个创新系统的兴趣，使用 Monte Carlo Serpent 计算代码和确定性 ERANOS 代码对 ALLEGRO 反应堆堆芯进行中子研究。提供了堆芯设计和陶瓷燃料成分的详细说明。为了降低未来应用模拟的计算成本，使用 TGV/VARIANT 模块中的不同计算选项和 7 组能量结构分析不同情况。为了验证 ERANOS 模型，将结果与 Serpent 开发的三维异构参考模型进行了比较。在生命开始时，计算核心的主要参数，例如 k-eff 值、通量和功率分布、多普勒常数、氦密度对反应性的影响和 β-eff 值。由于氦的密度低，结果中的主要差异对应于扩散和简化的输运计算。通过使用 7 组结构，可以减少计算时间，同时减少对结果精度的影响。此外，对于传输计算（P 由于氦的密度低，结果中的主要差异对应于扩散和简化的输运计算。通过使用 7 组结构，可以减少计算时间，同时减少对结果精度的影响。此外，对于传输计算（P 由于氦的密度低，结果中的主要差异对应于扩散和简化的输运计算。通过使用 7 组结构，可以减少计算时间，同时减少对结果精度的影响。此外，对于传输计算（P₃ ) 具有7-能群结构。假设运行时间为 365 天，分析了燃耗过程中的 k-eff 和燃料同位素质量演变。还给出了循环开始和结束时的相对燃料分数、繁殖率和平均燃耗。