The decommissioning of nuclear facilities results in a considerable amount of radioactive material. Often the radioactivity is concentrated in small items that have been either activated or contaminated. Detection of these so called “hot spots” together with their separation from the remaining material stream enables separate disposal of the radioactive remnants in a volume-optimized manner. The separated parts with higher activity inventory are subsequently conditioned and packaged for final storage. The rest of the material is measured afterwards to decide whether it can be released from the regulatory control for radiation protection. Based on this measurement this material will either be released or, in case of activity levels exceeding the prescribed limits, conditioned and disposed as radioactive waste at reduced costs compared to the unseparated material.
One objective of VIRERO is to research and develop processes that allow for an automatic spatial and radiological characterization of radioactive remnants of all activity classes. A second objective is to couple this characterization to a robot-aided sorting of the radioactive material. In many cases, bulky parts need to be disassembled before sorting can take place. Disassembling and sorting in the VIRERO project will be undertaken remote controlled to allow handling of materials with high dose rates. The remote control is VR-supported and enables steering several industrial robotic arms at once. The combination of spatial and radiological characterization of the items being measured allows to determine the spatial activity distribution using a reconstruction algorithm. The reconstruction aids remote controlled and partially automated sorting using a digital twin of the robotic system. Thus the items can be dismantled, characterized and sorted according to their radiological characteristics.
The project is carried out by AiNT GmbH, Framatome GmbH and the FAPS (Institute for Factory Automation and Production Systems) of the Friedrich-Alexander University of Erlangen-Nuremberg. Framatome and FAPS will assemble a test stand at which the robot aided handling will be developed using a digital twin of the test stand and methods from Virtual Reality (VR) and Augmented Reality (AR). AiNT engages in the radiological characterization methods for automated assessment of activity of individual parts by developing advanced activity reconstruction algorithms. The VIRERO project is supported by the German Ministry of Education and Research (BMBF) under the research programme “FORKA – Research for the decommissioning of nuclear facilities”. It is associated with the research cluster “Waste Treatment, Declaration of Waste and Interim Storage”.
VIRERO covers the disassembly, characterisation and sorting of radioactive materials. Framatome and FAPS will assemble a test stand that allows for validating the robot aided disassembly and sorting. AiNT develops measuring methods for automated assessment of activity of individual parts considering advanced algorithms of activity reconstruction in the context of radiological characterization. To this end, radiation is measured using four different γ-sensitive detectors (HPGe detector, two scintillation spectrometers and one Geiger-Müller counting tube) depending on the degree of the items’ activity level. In addition, a laser scanner is used to obtain a precise 3D model of the material. The 3D model and the radiological measurement data are combined in a post-processing step to generate a map showing each items’ spatial distribution of activity. Through the innovative combination of automatic spatial geometry recognition and radiological methods of activity reconstruction radioactive wastes of all activity levels are sorted remote controlled with state-of-the-art industrial robots. The modular build of the VIRERO system allows for a flexible and mobile sorting system aimed at the operation or dismantling of nuclear facilities.
In order to reuse residual materials stemming from nuclear facilities, e.g. from the decommissioning of nuclear facilities, the accordance with clearance levels as stated in the German Radiation Protection Ordinance (StrlSchV) needs to be proven. In this use case, these materials reside in pallet cages or big bags which are characterized radiologically via one measurement. Radioactive hot spots that occur as contaminated or activated small remnants inside these large packages will hinder the release of the whole package. A subsequent conditioning of such radioactive wastes involves high expenses both, in terms of time and involved personnel. With the VIRERO system hot spots will be identified and localized reliably thanks to an automated activity reconstruction. Personnel expenses will be reduced due to user friendly, remote controlled handling using industrial robots. This also results in a reduction of radiation exposure of the personnel involved. At the same time, the total amount of material suitable for clearance is raised by separating the hot spots from the rest of the waste.
In order to condition radioactive wastes for final storage it has to be proven by measurement that the activity of the radioactive wastes is in conformity with prescribed nuclide specific activity limits. Single waste parts of a waste drum could lie above the limits specific to the waste product. This could negate the packaging of the waste product. To date, these drums are opened inside hot cells for post-conditioning and sorted using mechanical manipulators. Hot spots that have been localized beforehand are sorted out and the drum is moved to conditioning and later final storage. Following the separation of the hot spots the remaining material could for instance be packaged without additional shielding at lower costs resulting in waste package classification as a lower waste product group. VIRERO enables optimizing the volume of radioactive waste with significantly lower expenses regarding personnel and costs. Additionally, radiation exposure of the personnel involved is reduced. This is guaranteed by a nuclide specific automated reconstruction of activity of the waste drum’s content and a remote controlled, robot aided and partially automated sorting.
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