Nuclear Waste Management
1Adopted for Geological Disposal Facility Monitoring in Europe and Japan
In the field of nuclear waste management, where long-distance and long-term monitoring is essential, Neubrex's measurement interrogators, optical fiber cables, and monitoring systems have been adopted for research and demonstration projects in Europe and Japan in preparation for the future operation of geological disposal facilities.
Neubrex has accumulated more than 10 years of experience in continuous monitoring at underground research laboratories, demonstrating the effectiveness of distributed fiber optic sensing.
2Detection of Groundwater Inflow Zones Using Fiber Optic Temperature Logging
- ✔︎ Continuous DFOS measurement of temperature distributions in a borehole approximately 200 m deep, enabling localized temperature changes along the depth to be detected at high spatial resolution
- ✔︎ Identification of groundwater inflow zones through analysis of temperature recovery rates, with results showing consistency with existing FEC logging results
This study demonstrates temperature logging using distributed fiber optic sensing (DFOS) to identify groundwater inflow zones in a borehole. A fiber optic sensor cable was installed in a borehole approximately 200 m deep. After replacing the borehole water with water at approximately 25–30°C, changes in the temperature distribution throughout the borehole were continuously measured from before pumping began until after pumping stopped. This approach enabled localized temperature changes occurring over narrow depth intervals, which are difficult to capture with conventional probe-based temperature logging, to be detected at high spatial resolution.
Analysis of the temperature recovery rate at each depth revealed characteristic temperature changes around GL-60 m and GL-80 m. Comparison with FEC logging results used to identify groundwater inflow zones showed generally consistent trends, demonstrating the potential of fiber optic temperature logging to identify groundwater inflow locations in greater detail. Continuous, high-density temperature measurements using DFOS are expected to contribute to a more detailed understanding of groundwater flow in deep subsurface environments.
Source: The 81st Annual Meeting of the Japan Society of Civil Engineers (September 2026), © Japan Society of Civil Engineers
