Development of uniform surface sources by functionalization for decommissioning

The thesis aims to develop radioactive surface sources to improve the traceability of surface contamination measurements carried out during dismantling operations. In particular, the ultimate aim is to provide radioactive sources that can be traceable and used in the field to characterize the performance of surface contamination monitors. The sources that meet the requirements of international standards have very different characteristics from the surfaces to be monitored during decontamination and dismantling (D&D) activities. They consist of a rigid aluminum substrate on which surface the activity is deposited and then covered with a protective layer.

The study involved developing methods for modifying two types of substrates, polymeric and aluminum, to attach radioactive elements (trivalent lanthanide and actinide). For aluminum substrates, coating with manganese or chromium oxides was tested, along with silanol functionalization and phosphonic acid grafting. The surface modification of polymeric substrates was based on oxidation, followed by sulfonic acid grafting. Whatever the substrate, the study was divided into several stages: preparing the surface, functionalizing/modifying it, attaching the radioactivity and quantifying the uniformity of the radioactive distribution.

Each stage was optimized and characterized using SEM, ATR-FTIR, liquid scintillation and autoradiography. The aluminum substrate, while flexible, allows to be compared with current standard sources. Additionally, the polymeric substrates can be adapted to mimic the real constraints of the D&D sites (sand load, roughness, molding of complex shapes). Finally, an assessment of the compliance of the sources with existing standards was carried out, even though these standards do not meet the complex needs of measurements on D&D sites. The polymeric substrates coated with manganese oxide could uptake close to 100% of ¹⁵²Eu and ²⁴¹Am when immersed in acidic radioactive solutions for a few hours. For these sources, the uniformity of the radionuclide distribution reached 90%.

radioactive source, decomissioning, surface modification, traceability, ¹⁵²Eu, ²⁴¹Am

Full document (EN): HAL-04521519