Abstract Subcritical noise experiments at frequencies up to 100 kHz employing two distinct boron dilution in the reactor tank water (286.8 and 578.6 ppm of natural boron) were performed in the IPEN/MB-01 reactor. The Auto Power Spectral Densities (APSD) were inferred employing the IPEN/MB-01 Correlator and were best described by a four-mode decay model up to about 70 kHz. The analyses reveal that the first two modes were related to thermal neutron and the other two to the fast ones. The coupling between thermal and fast neutrons was weak, and they could be considered uncoupled. A two-region two-group kinetic model was built and for the first time important parameters, such as the subcritical reactivities, generation times, and the prompt neutron decay constants all in the core and reflector in the 286.8 ppm case were inferred. The experiments can be considered unique of its kind and the theory/experiment comparisons reached good agreements.

中文翻译：

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IPEN/MB-01 研究堆设施中高达 100 kHz 的零功率噪声

摘要 在 IPEN/MB-01 反应堆中进行了频率高达 100 kHz 的亚临界噪声实验，在反应堆水箱水中采用了两种不同的硼稀释液（天然硼的 286.8 ppm 和 578.6 ppm）。自动功率谱密度 (APSD) 是使用 IPEN/MB-01 相关器推断出来的，最好用高达约 70 kHz 的四模衰减模型来描述。分析表明，前两种模式与热中子有关，另两种与快中子有关。热中子和快中子之间的耦合很弱，可以认为它们是非耦合的。建立了两区两组动力学模型，首次推断了286.8 ppm情况下堆芯和反射层中的亚临界反应活性、产生时间和瞬发中子衰变常数等重要参数。