Speaker
Description
In the decommissioning of the Fukushima Daiichi Nuclear Power Station (FDNPS), understanding the distribution of radiation sources and identifying radioactive hotspots—areas with localized high concentrations of radiation sources—is crucial for developing a detailed decontamination plan and minimizing worker exposure. To address this, we are developing a system and method for remotely locating radiation sources while reducing worker exposure by integrating a Compton camera, a type of gamma-ray imager, with a robot.
In environments with multiple corridors and rooms, such as the buildings of FDNPS, surveying the entire area with multiple robotic systems is more efficient than using a single robot. Based on this consideration, we are conducting demonstration tests using multiple robots equipped with Compton cameras to locate radiation sources in narrow corridors.
One challenge of using gamma-ray imagers, including Compton cameras, is that the visualized radiation source image lacks depth information. For example, if a radiation source appears projected on a wall, it is difficult to determine whether the source is in front of or behind the wall. A potential solution to this issue is to take measurements from multiple viewpoints, including different angles around walls, to determine the three-dimensional (3D) location of the radiation source. In fact, previous studies have reported methods for using Compton cameras from multiple viewpoints to achieve 3D localization of radiation sources [1].
However, in many cases, measuring the target area from multiple viewpoints is not feasible within the buildings of FDNPS due to the presence of narrow corridors and other obstacles. Consequently, it may be necessary to determine whether a radiation source is in front of or behind a wall using measurements taken from only one direction with a Compton camera. To address this issue, Sato, one of the authors, has previously succeeded in determining the position of a radiation source—specifically, the distance between the Compton camera and the source—using measurements from a single direction [2].
Building on this work, we conducted a demonstration test using two robots equipped with Compton cameras to visualize and locate radiation sources in narrow corridors. We intentionally created a scenario in which a single robotic system would incorrectly determine the exact location of the radiation source. To mitigate this, a second robotic system was deployed to accurately locate the source using measurements taken from only one direction.
At the international workshop IWORID 2025, we will present the results of several demonstration tests, including the one described above.
[1] Sato, Y., Terasaka, Y., Ozawa, S. et al. Development of compact Compton camera for 3D image reconstruction of radioactive contamination, JINST 12, C11007 (2017).
[2] Sato, Y., Identification of depth location of a radiation source by measurement from only one direction using a Compton camera, Appl. Radiat. Isot. 195, 110739 (2023).
| Workshop topics | Applications |
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