Safety is a prerequisite for final disposal. The key to the final disposal of spent fuel is the long-term safety of the solution, which is assessed and demonstrated with a safety case. Safety case refers to all technological and scientific materials, analyses, observations, trials, tests and other proof used to justify the reliability of the assessments made of the long-term safety of final disposal. At Posiva, this means demonstrating the functionality of the geological disposal solution studied and tested for more than four decades in the conditions of the Olkiluoto bedrock, as well as demonstrating the generation of radiation doses to the environment in the event of failure of one or more engineered release barriers and release of radioactive substances from the repository to the living environment.