# Resurgence of a Nation's Radiation Science Driven by Its Nuclear Industry Needs
## 3 Exemplar Results
### Commercial Polymeric Materials of Interest to the Nuclear Industry  
Two polymeric materials are being considered for different applications in the nuclear industry: the decontamination of surfaces by strippable coatings and the 3D printing of components or hand tools. In decontamination, the removal of radioactive particles from the surfaces of large items such as concrete walls has the potential to reduce waste volumes. Commercial strippable coatings may be used for surface decontamination and three samples have been selected for comparative gamma and 5.25 MeV He ion irradiation, based on an initial sift of twelve different coatings that were subjected to gamma irradiation only. [48]. All samples were irradiated to a total dose of 500 kGy. Samples for gamma irradiation were loaded into 20 mL crimp-capped glass vials filled with laboratory air and received a dose rate of \(\sim\)80-90 Gy/min. Samples for He ion irradiation were loaded into a bespoke sample cartridge and irradiated in vacuum using a rastered ion beam until an accumulated charge of 285 \(\upmu\)C was reached. Analysis using FT-IR and Raman spectroscopy, shown in Figure 9, revealed that coating 1 exhibited a loss of absorption across many wavelengths indicative of depolymerization and, in the case of gamma irradiation, reacted with air to develop nitrogen-containing functional groups (Raman peak shifts at 450 cm\({}^{-1}\) and 625 cm\({}^{-1}\)). Coating 3 showed less change in absorption while coating 8 showed very little change in absorption; hence, it is the most promising strippable decontamination coating for applications to the nuclear industry. A similar study has been conducted on fused filament fabricated (i.e., 3D printed plastic) materials and the chemical changes as a result of radiation have been compared to changes in mechanical properties. [28] Although a variety of filament compositions are available commercially, two types deserve attention here: PLA (polylactic acid) is a very common choice of filament that has been found to perform poorly under irradiation while a filament based on nylon was seen to perform best, under the conditions studied: gamma radiation was applied at a dose rate of 13 kGyh\({}^{-1}\) for Nylon and 6 kGyh\({}^{-1}\) for PLA to achieve a variety of total absorbed doses. FT-IR and Raman analysis, along with Gel permeation chromatography to determine molecular weight, found that PLA predominantly undergoes chain scission, for doses of up to 0.3 MGy, with a decrease in both Young's Modulus and ultimate tensile strength (UTS). Nylon demonstrated only very small changes in Raman spectra, for much larger total doses (up to 5.3 MGy) which correlate with results of mechanical testing where no statistical change in UTS was found. However, the FT-IR spectra revealed a reaction with water vapor and further chemical changes indicative of chain scission suggesting that there were some chemical changes that did not affect mechanical properties. Such changes may have occurred in components that are added to the filament to modify other properties, with the unfortunate side effect of producing a sticky texture to the irradiated material. Both of these examples from commercial materials, made using a proprietary mix of chemicals, demonstrate that radiation testing is a pre-requisite for understanding their limitations in a nuclear environment. They also indicate that a complex interplay between additives that may be incorporated into such materials and the radiation chemistry may lead to some undesirable performance. In the case of 3D printing, the chemical changes  
Figure 9: FT-IR and Raman spectra from a selection of commercial strippable decontamination coatings that received an absorbed dose of 500 KGy from either gamma radiation or He ions. (**a**) FT-IR spectra from coating 1. (**b**) Raman spectra from coating 1. (**c**) FT-IR spectra from coating 3. (**d**) Raman spectra from coating 3.