Research initiated some 15 years ago at the Royal Military College of Canada (RMC) on the effects of mixed fields of radiation on high polymer adhesives and composite materials has revealed that some polymer-based composite materials were indeed resistant to radiation-induced damaging and could be considered as good candidate materials for the fabrication of leak-tight containers intended at isolating the low-level radioactive waste (LLW) as well as the high-level waste (HLW) from the biosphere, and this for time periods up to several centuries. The aim of the present research project was then to identify several of these polymer-based composite materials as possible candidates for this application and then to determine experimentally whether these materials actually could meet this demanding challenge. The experimental procedure consisted in irradiating in the pool of the SLOWPOKE-2 nuclear research reactor at RMC several sets of material samples close to the reactor core for time periods sufficient to accumulate selected doses within the samples. The nuclear reactor provided a mixed radiation field (thermal and fast neutrons, electrons, recoil protons, gamma and X-ray photons) that was comparable to and more intense than the radiation field affecting the container walls in an actual disposal site. The irradiated samples were then removed from the reactor pool and subjected to a large battery of analytical tests, including tensile and flexural testing, FTIR, DSC, MALDI, WAXS and neutron scattering, among many others. Among the materials investigated are PolyEtherEtherKetone (PEEK), PolyEtherImide (PEI), several thermoplastics such as polycarbonate, polypropylene, polyurethane, and Nylon 66. Other phases of this extensive research included an investigation of Inter Penetrating Network (IPN) polymers and polymer-based coatings intended at protecting the walls of containers made of copper. An aliphatic castor-oil polyurethane (COPU) and an aromatic COPU were the coatings investigated. The research evolved to include in the study the effects of factors such as the temperature and the pH of surrounding water on the materials in addition to and concurrent with the action of the radiation. As a result, several polymer-based composite materials were found to be suitable for the fabrication of containers intended for LL W, and a few (such as PEEK and PEI) are indeed suitable for containers intended for the disposal of HLW and spent nuclear reactor fuel. In particular, cumulative radiation doses as high as 1 MGy on PEEK samples caused very minimal changes in the physical, mechanical and chemical properties of this material. The research has also shown that, if sintered thorium dioxide were used as the filler material within the container instead of the glass beads suggested in the Canadian spent fuel disposal proposal, the radiation dose on the container walls would be significantly reduced and would allow the use of several more polymer composites for this demanding application.