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.