CEA-List was one of the headliners at the April 2024 CLEANDEM* project final demo day at the Eurex plant in Saluggia, Italy. The event, organized by Societa Gestione Impianti Nucleari (SOGIN), was attended by 70 representatives of national and international nuclear decommissioning and cleanup organizations. CEA-List presented the technologies it developed as part of this European project. Whether it is in terms of technical performance or cost, the personal protection technologies showcased highlight not only how inventive CEA-List is, but also how active a role the institute is playing in the nuclear decommissioning and cleanup space.
When a nuclear facility reaches the end of its service life, it must be decommissioned and any residual radioactivity cleaned up. This kind of project is long and complex. All structures must be inspected so that any contaminated areas—and the sources of contamination—can be identified and placed under monitoring, even if difficult to access. In Europe, the number of decommissioning and cleanup projects is expected to rise1 due to an aging installed base and to the phasing out of nuclear in some countries.
The CLEANDEM (Cyber physicaL Equipment for unmanned Nuclear DEcommissioning Measurements) project, coordinated by CEA, was launched in 2021 to respond to this pressing and very topical issue by improving worker protection, lowering costs, and shortening project turnaround times. The specific focus was to develop new ionizing radiation detection and measurement technologies suitable for use in severe environments, integrate them into a remotely controlled ground robot, and carry out a demonstration in real-world conditions.
CEA-List offered up a demonstration of its Nanopix3 coded-mask spectro-imager—the most compact and lightweight system in the world capable of both locating and discretely identifying different radioactive sources. “Conventional detection devices measure ambient radioactivity, much like a thermometer measures ambient temperature. Our spectro-imager is different. It can generate an accurate image of the source’s location from a distance,” said Maugan Michel, a research engineer at CEA-List’s Laboratory for Measurement Instrumentation and Sensors. Nanopix3, mounted on the arm of a ground robot, was able to locate and measure a source of gamma radiation in a metal drum located several meters from the robot. The entire operation, completed from a mobile platform, took just ten seconds. Hot spots are traditionally found using a “blind search” technique. Readings are taken at different points and the intensity of the signal determines how close the source is. The longer it takes, the more radiation workers are exposed to. The Nanopix3 demo garnered a very enthusiastic response from the event attendees.
CEA-List’s demonstration continued with a presentation of its pixelated contaminameter, used to measure radioactive contamination in large areas and complex environments. The instrument can measure beta (short-range) and gamma (long-range and more penetrating) radiation discretely, which means it can differentiate radiation from the environment from radiation on contaminated surfaces that needs to be measured. The contaminameter’s modular design, based on independently-operating 5 × 5 cm2 detector blocks, is one of its main advantages. These Tetris-style “pixels” can be assembled into rows or squares to adapt to the geometry of the area being inspected. This saves precious time when inspecting large areas and also facilitates access to tight spaces like recesses and metal beams.
CEA-List has also developed a fiber-optic-based optically stimulated luminescence (OSL) technology coupled with a shape detection algorithm. The optical fiber, much like an endoscope, can be inserted into narrow, hard-to-access areas like the countless pipes that crisscross nuclear facilities. The deformation data collected is used to reconstruct the shape of the optical fiber in 3D up to a length of six meters. The fiber is then geolocated in relation to an external reference. The OSL probe measures dose rate profiles. Together, these two technologies produce geolocalized radiological data, which, thanks to reverse computation, can be used to generate 3D activity reconstructions inside inaccessible structures.
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The research we did for CLEANDEM resulted in new detection and measurement instruments, some of which were mounted on a ground robot. Our new research program is focusing on the integration of even lighter sensors into drones so that walls and height will no longer be insurmountable obstacles.
