Radiation effects on the properties of a polyurethane/epoxy graft interpenetrating polymer network. An investigation into the application of polymers in the fabrication of containers to store radioactive waste

The toughening effects of a castor oil based polyurethane on an epoxy matrix, by means of an interpenetrating network (IPN) was investigated. In addition, the radiation effects of two PU/EP graft-IPNs, 19/81 and 27/73 PU/EP graft-IPNs, were examined so that possible application of these materials in the fabrication of containers to store radioactive waste over long periods of time could be considered. The polyurethane/epoxy graft-IPN was made by a sequential method of synthesis, in which the polyurethane prepolymer was prepared before the addition of the epoxy resin and crosslinker. The PU/EP graft-IPN specimens were subjected to several doses of radiation that ranged from 0.11 MGy to 3.0 MGy, using the SLOWPOKE-2 nuclear reactor at Royal Military College of Canada (RMC). The irradiated and unirradiated IPN samples were then subjected to a battery of chemical and mechanical tests to determine the effects of radiation. Based on the observations from the chemical and mechanical tests, it has been established that the 19/81 PU/EP graft-IPN is suitable for applications in radiation environments below a dose of 1.5 MGy. The 27/73 PU/EP graft-IPN is unsuitable for radiation applications at low doses, however it shows a noticeable increase in chemical and mechanical properties with increasing accumulated dose. Past work at RMC has shown the beneficial properties of a ThO2 filler within the radioactive waste container. With regard to the design of the disposal containers, with the aid of aThO2 filler, it is the opinion from the present work that the graft-IPNs could potentially be used in the fabrication of containers to store low and intermediate level radioactive waste, as well as spent nuclear fuel and high level radioactive waste. (author)