Cuba [Country report]

Cuba has been committed to the peaceful use of ionising radiation for benefits of the society, this comprises the safety management of all radioactive waste generated from the nuclear applications. The Center for Radiation Protection and Hygiene (CPHR) is responsible for the radioactive wastes management in the country, including the safety assessment (SA) of disposal facilities. Into the SA methodologies, the associated impact to the environment and the human health from the radioactive waste disposal is measured through of safety indicators. The radiological dose and risk are the most common endpoints adopted, but when in the SA the long-term impact is evaluated, the former indicators can be affected by different assumptions about the critical group, assessment period and parameter uncertainties. With the inclusion of others safety indicators besides dose and risk a reasonable assurance can be achievable and may facilitate the defence of the safety assessment results, according to the radiation protection principles. The concentrations of naturally occurring radionuclides (NOR) and the natural fluxes of radionuclides were selected as safety indicators complementary to dose and risk for the carried out assessment. Both indicators can provide a measure of the potential effect on the human health and the environment, they are less affected for the time and also, it is easy to implement in the safety assessment methodology. The NOR concentrations for Cuba were obtained from a database based in the results of geological and geophysical surveys in the country, the natural concentrations of U, Ra, Th, K were associated with different lithologies for 3 geographical areas of the Country. The site selected for the disposal facility is located in a massif granodiorite in the central part of the country, all relevant information about the geosphere was obtained during the site selection process where geologic, hydrogeologic and geophysical investigation were carried out in order to obtain the most important parameters of the host medium. The repository concentrations were calculated from radionuclide inventory adopted for a high level disposal facility. In order to make a proper comparison between the NORM and repository concentrations was adopted the Reference Equivalent Rock Volume (RERV), a volume of rock with dimensions according to our repository conceptual design. For the natural activity fluxes two processes were evaluated, the erosion and the groundwater fluxes, and the values were obtained from the site investigations and international references. For calculation of the flux data from the Repository, have been carried out a safety assessment for the Cuban radioactive waste disposal system following the Improvement of Safety Assessment Methodologies for Near Surface Disposal Facilities (ISAM) methodology. According the assessment context, have been defined a normal scenario (release scenario), which takes into account only the natural occurrence process in the disposal system, corrosion, degradation, infiltration and so on. A compartments model was adopted in order to simulate the complete radioactive waste disposal system. The final objective was to obtain the specific activity flux from the repository for each radionuclide, allowing preliminary release comparisons against the natural-occurring species. The preliminary comparison showed that the calculated concentrations and fluxes in the conceptual repository are not higher than the natural values in the host rock. According the carried out assessment using the complementary safety indicators, the reference disposal facility does not increase the natural activity concentration and fluxes in the environment. In Cuba, it is the first application of other safety indicators for safety assessment of radioactive waste disposal facilities, evidencing that those endpoints could be a useful tool to support the safety assessment for the radioactive waste disposal system. In next studies, should be evaluated other relevant elements and radionuclides present in the specific Cuban inventories and carry out more specific site investigation in order to reduce the data uncertainty. (author)