Waste migration, natural barrier

Deep geological disposal is the most favored solution for the permanent disposal of nuclear wastes with long half-lives. Although the locations of the burial places are selected with outmost care to avoid migration of the wastes in nature over a very long period of time, no barrier can be safe forever, so, numerous studies are in progress to determine the main factors that could cause leaks of radioactive nuclides. Soluble compounds in ground water are likely to play a major role in the release of actinides. 

Besides, radioactive cobalt is a common radionuclide in liquid wastes from nuclear facilities, and natural erionite is a good exchanger for 60Co2+. Studies carried out with this material reveal its possibilities in the elimination of radioactive cobalt from solutions [73], The exchange of 232Th4+ in natural clinoptilolite and mordenite from liquid solutions has also been studied [74], All these peculiarities of natural zeolites make it suitable to be exploited as natural barriers for the migration of radionuclides and, consequently, natural zeolite deposits can be potential sites for a radioactive waste repository [19]. These materials have also been employed for the removal of radionuclides from polluted areas in places where nuclear power station accidents have occurred or where... 

A feature which delays or prevents radionuclide migration from the waste and/or repository into its surroundings. Natural barriers are, in the case of deep geological repositories, represented by the host rock and the surrounding geological formation. An engineered barrier is a feature made by or altered by humans it may be a part of the waste package and/or part of the repository. 

This computational model calculates the annual radiological dose to humans over geological time scales due to the underground migration of radionuclides from a hypothetical nuclear waste disposal site through a system of idealised natural and engineered barriers. 

---