The performance of polymer containers used for the storage of radioactive waste

An evaluation of the performance of polymeric materials after exposure to radiation and acidic aqueous solutions provides a basis for the evaluation of failure mechanisms affecting these materials. The work evaluated the importance of the combined effects of aqueous solution diffusion, radiation exposure, and temperature on the mechanical performance, diffusion profile and molecular structure of polymeric materials. This work demonstrated that the dose rate is an extremely important factor since low dose rates have been shown to result in an increase in stress at yield (15 - 20%) over the times studied, whereas higher dose rates reduced stress at yield as discussed above. Irradiation of both Nylon 6,6 and Semi-Aromatic Nylon 6,6 at dose rates of 37 and 56 kGy/hr resulted in an initial decrease in the stress at yield and subsequent recovery. Irradiation at 20 kGy/hr resulted in an initial increase in stress at yield and a continued increase throughout the aging time. It is suggested that polyamide 6,6 may be considered an acceptable material for the fabrication of storage containers for Low Level Radioactive Waste. Similarly, semiaromatic polyamide 6,6, with its greater resistance to the combined effects of solution diffusion and radiation exposure, may be considered an acceptable material for the fabrication of containers for the storage of Intermediate Level Radioactive Waste. Finally, these results provide further explanation of the results obtained for materials such as polycarbonate, which has been previously determined to be viable candidates for the storage of High Level Radioactive Waste.