We describe the seismoacoustic wavefield recorded outdoors but inside the facility fence of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (Tennessee). HFIR is a research nuclear reactor that generates neutrons for scattering, irradiation research, and isotope production. This reactor operates at a nominal power of 85 MW, with a full‐power period between 24 and 26 days. This study uses data from a single seismoacoustic station that operated for 60 days and sampled a full operating reactor cycle, that is, full‐power operation and end‐of‐cycle outage. The analysis presented here is based on identifying signals that characterize the steady, that is, full‐power operation and end‐of‐cycle outage, and transitional, that is, start‐up and shutdown, states of the reactor. We found that the overall seismoacoustic energy closely follows the main power cycle of the reactor and identified spectral regions excited by specific reactor operational conditions. In particular, we identified a tonal noise sequence with a fundamental frequency around 21.4 Hz and multiple harmonics that emerge as the reactor reaches 90% of nominal power in both seismic and acoustic channels. We also utilized temperature measurements from the monitoring system of the reactor to suggest links between the operation of reactor’s subsystems and seismoacoustic signals. We demonstrate that seismoacoustic monitoring of an industrial facility can identify and track some industrial processes and detect events related to operations that involve energy transport.

中文翻译：

---

研究型核反应堆的局部地震声波场及其对反应堆功率水平的响应

我们描述了在户外但在橡树岭国家实验室（田纳西州）的高通量同位素反应堆（HFIR）的设施围栏内记录的地震声波场。HFIR是一个研究型核反应堆，可产生用于散射，辐射研究和同位素生产的中子。该反应堆的额定功率为85 MW，全功率周期为24到26天。这项研究使用了一个运行60天的地震台站的数据，并采样了一个完整的反应堆周期，即全功率运行和周期末中断。此处提供的分析基于识别表征反应堆稳态（即全功率运行和周期结束中断，过渡（即启动和停机）状态）的信号。我们发现，总地震声能紧随反应堆的主要功率循环，并确定了由特定反应堆运行条件激发的光谱区域。尤其是，我们确定了一个基音频率约为21.4 Hz的音调噪声序列，并且随着反应堆在地震和声学通道中达到标称功率的90％，出现了多个谐波。我们还利用反应堆监控系统的温度测量结果来建议反应堆子系统的运行与地震声信号之间的联系。我们证明，对工业设施进行地震声监测可以识别和跟踪某些工业过程，并检测与涉及能源运输的运营相关的事件。