Radioactive decontamination in low-temperature environments by using a novel high-strength strippable coating

Rheological and radioactive decontamination properties of ethyl cellulose sols in green solvents at a temperature below 0 °C

Strippable film decontamination has been considered one of the best prospects for radioactive surface decontamination due to its high decontamination effect and less secondary pollution. However, research into strippable films has until now focused on radioactive decontamination at room temperature. Therefore, it is vital to seek a suitable degradable material for preparing strippable films in removing contaminants in an extremely cold region, as it will face the problem of the freezing of the detergent. Ethyl cellulose (EC) is a kind of degradable biopolymer which is easily dissolved in volatile green organic solvents to form a sol below 0 °C which is advantageous for forming a film. Therefore, it would be the best choice for preparing a strippable film detergent. In this study, EC sols were obtained by placing EC powder into the green solvents anhydrous ethanol and ethyl acetate. The steady and dynamic rheological behavior of EC sols was investigated with a rotary rheometer with the temperature ranging from -10 °C to 0 °C to disclose their spraying performance. Moreover, the radioactive decontamination effect of EC sols and the mechanism were also investigated. The results showed that the EC sols were pseudoplastic fluids which obeyed the Ostwald-de Waele power law below 0 °C. Furthermore, the viscosity of EC sols could be reduced by stirring, which is convenient for large-area spraying during decontamination below 0 °C. At -10 °C, the comprehensive decontamination rates of all plates were over 85%. Therefore, EC sols could be used as a basic material for strippable film decontamination below 0 °C.

Molten salts for efficient removal of radioactive contaminants from stainless steel surface: Mechanisms and applications

Here, we have demonstrated an innovative decontamination strategy using molten salts as a solvent to clean stubborn uranium contaminants on stainless steel surfaces. The aim of this work was to investigate the evolutionary path of contaminants in molten salts to reveal the decontamination mechanism, thus providing a basis for the practical application of the method. Thermodynamic analysis revealed that alkali metal hydroxides, carbonates, chlorides and nitrates can react with uranium oxides (UO3 and U3O8) to form various uranates. Notably, the decontamination mechanism was elucidated by analyzing the chemical composition of the contaminants in the molten salts and the surface morphology of the specimens considering NaOH-Na2CO3-NaCl melt as the decontaminant. The decontamination process involved two stages: a rapid decontamination stage dominated by the thermal effect of molten salt, and a stable decontamination stage governed by the chemical reactions and diffusion of molten salt. Subsequently, a multiple decontamination strategy was implemented to achieve high decontamination rates and low residual radioactivity. Within the actual cleaning time of 30 min, the decontamination efficiency (DE) of UO3-contaminated specimens reached 97.8% and 93.0% for U3O8-contaminated specimens. Simultaneously, the radioactivity levels of all specimens were reduced to below the control level for reuse in the nuclear domain. Particularly, the actual radioactive waste from the nuclear industry reached a reusable level of radioactivity after decontamination. The NaOH-Na2CO3-NaCl melt outperforms conventional chemical solvents and may be one of the most rapid and efficient decontaminants for stubborn uranium contamination of metal surfaces, which provides insights in regard to handling nuclear waste.

Peelable Alginate Films Reinforced by Carbon Nanofibers Decorated with Antimicrobial Nanoparticles for Immediate Biological Decontamination of Surfaces

This study presents the synthesis and characterization of alginate-based nanocomposite peelable films, reinforced by carbon nanofibers (CNFs) decorated with nanoparticles that possess remarkable antimicrobial properties. These materials are suitable for immediate decontamination applications, being designed as fluid formulations that can be applied on contaminated surfaces, and subsequently, they can rapidly form a peelable film via divalent ion crosslinking and can be easily peeled and disposed of. Silver, copper, and zinc oxide nanoparticles (NPs) were synthesized using superficial oxidized carbon nanofibers (CNF-ox) as support. To obtain the decontaminating formulations, sodium alginate (ALG) was further incorporated into the colloidal solutions containing the antimicrobial nanoparticles. The properties of the initial CNF-ox-NP-ALG solutions and the resulting peelable nanocomposite hydrogels (obtained by crosslinking with zinc acetate) were assessed by rheological measurements, and mechanical investigations, respectively. The evaluation of Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) for the synthesized nanoparticles (silver, copper, and zinc oxide) was performed. The best values for MIC and MBC were obtained for CNF-ox decorated with AgNPs for both types of bacterial strains: Gram-negative (MIC and MBC values (mg/L): E. coli-3 and 108; P. aeruginosa-3 and 54) and Gram-positive (MIC and MBC values (mg/L): S. aureus-13 and 27). The film-forming decontaminating formulations were also subjected to a microbiology assay consisting of the time-kill test, MIC and MBC estimations, and evaluation of the efficacity of peelable coatings in removing the biological agents from the contaminated surfaces. The best decontamination efficiencies against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa varied between 97.40% and 99.95% when employing silver-decorated CNF-ox in the decontaminating formulations. These results reveal an enhanced antimicrobial activity brought about by the synergistic effect of silver and CNF-ox, coupled with an efficient incorporation of the contaminants inside the peelable films.

Polymeric gel for surface decontamination of long-lived gamma and beta-emitting radionuclides

Synthesis and characterization of strippable polymeric-gel solution based on a water-soluble polymer (PVA), plasticizing agent (glycerol), and chelating agent (8-Hydroxyquinoline) for the surface decontamination from ¹³⁷Cs and ⁶⁰Co was carried out. Decontamination of glass and PVC surfaces was investigated in the present study, as a function of various chelating agents, gel-layer thickness, and radioactivity level. The decontamination efficiency was up to 95% for both radionuclides after 24 h of contact time with the contaminated surface. The obtained results suggest that the decontamination process of ¹³⁷Cs and ⁶⁰Co by polymer gel is possible combined by two mechanisms: chemically and physically.

Peelable Nanocomposite Coatings: "Eco-Friendly" Tools for the Safe Removal of Radiopharmaceutical Spills or Accidental Contamination of Surfaces in General-Purpose Radioisotope Laboratories

Radioactive materials are potentially harmful due to the radiation emitted by radionuclides and the risk of radioactive contamination. Despite strict compliance with safety protocols, contamination with radioactive materials is still possible. This paper describes innovative and inexpensive formulations that can be employed as 'eco-friendly' tools for the safe decontamination of radiopharmaceuticals spills or other accidental radioactive contamination of the surfaces arising from general-purpose radioisotope handling facilities (radiopharmaceutical laboratories, hospitals, research laboratories, etc.). These new peelable nanocomposite coatings are obtained from water-based, non-toxic, polymeric blends containing readily biodegradable components, which do not damage the substrate on which they are applied while also displaying efficient binding and removal of the contaminants from the targeted surfaces. The properties of the film-forming decontamination solutions were assessed using rheological measurements and evaporation rate tests, while the resulting strippable coatings were subjected to Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and tensile tests. Radionuclide decontamination tests were performed on various types of surfaces encountered in radioisotope workspaces (concrete, painted metal, ceramic tiles, linoleum, epoxy resin cover). Thus, it was shown that they possess remarkable properties (thermal and mechanical resistance which permits facile removal through peeling) and that their capacity to entrap and remove beta and alpha particle emitters depends on the constituents of the decontaminating formulation, but more importantly, on the type of surface tested. Except for the cement surface (which was particularly porous), at which the decontamination level ranged between approximately 44% and 89%, for all the other investigated surfaces, a decontamination efficiency ranging from 80.6% to 96.5% was achieved.