DECRET

The objective of the DECRET research program is twofold and aims to: • provide a novel solution, specific to and with improved sensitivity for the detection of radioactive elements: cesium and uranium, • ensure effective decontamination of all surfaces contaminated with these radioactive metals, in particular by applying to contaminated surfaces a foam composition containing magnetic nanoparticles functionalized with highly specific chelating agents and harvesting these nanoparticles by means of an industrial electromagnet. The aim of this research program is: 1) to build two quick detection systems for cesium and uranium. These systems will be based on microfluidic devices equipped with a specific detector for each of the two metals. These devices will be based on fluorescent calixarenes. 2) to develop new molecules capable of complexing these metals by exploring two possible technologies: • (a) sequestering agents with a pulvinic acid backbone (norbadione subunits, natural cesium sequestering agent found in certain mushrooms) and • (b) calixarenes (cyclic complexing agents). 3) to select the most effective cesium and uranium complexing molecules. 4) to graft them on support materials such as magnetic nanoparticles (doubly functionalized materials) or mesoporous materials (sponge and/or lightweight felt). 5) to incorporate these magnetic nanoparticles in the formulation of a foaming surface decontamination base, with high wetting power enhancing contact between nanoparticles and cesium or uranium contaminated sediments; compatibility of the various components with this aqueous foam will be controlled, thereby ensuring the grafted nanoparticles remain well dispersed and kept in suspension. The foam form will be easy to use in the field in case of accidental contamination. 6) to collect the radioactive elements by passing an electromagnet over the foam loaded with magnetic nanoparticles, 7) in parallel to being grafted on magnetic nanoparticles, the molecules developed under (2) will be grafted onto the surface of previously modified substrates, using a methacrylate monomer functionalized with a calixarene group or a pulvinic acid derivative. These structures would in particular allow to make filters or sponges capable of removing efficiently and selectively the cesium and uranium radioelements potentially present in an aqueous medium. At this stage, the tests will be performed on « cold » metals. Foam generation tests will be conducted on a pilot unit designed by CEA-DEN (Marcoule). Decontamination trials will be carried out on the one hand using the new chelating molecules and on the other hand using the complete and operational formulations derived from these molecules. The formulations will integrate suitable solvents, additives and supports to facilitate the extraction of metal from the contaminated substrate. In field applications, the two following systems will be combined: • a system comprising a metal-containing mesoporous material obtained by grafting polymer brushes functionalized with these new chelating agents. • and a foam generation system loaded with magnetic nanoparticles allowing quick decontamination by "magnetic harvesting". The former system is more suitable for the decontamination of effluents (by filtering) or of low porosity hard surfaces (by sponging) and the latter one for the operational decontamination of large surfaces (buildings, land).