For an adequate assessment of the spent nuclear fuel, it is necessary to consider all possible uncertainties that affect the design, performance and possible accidents in nuclear facilities environment. Nuclear data are a source of uncertainty that is involved in neutronics, fuel depletion and activation calculations. Methodologies for performing the uncertainty propagation calculations need to be implemented in order to analyze the impact of the nuclear data uncertainties on critical responses during operation and in the event of accident, such as decay heat or neutron multiplication factor. Nevertheless, it is necessary to understand the current status of nuclear data and their uncertainties, in order to be able to handle this type of data.