Expected evolution of a spent nuclear fuel repository at Olkiluoto

15 RIVIAe LIIKAA Posiva aims to submit to the Finnish government a construction license application, supported by the PSAR and a Safety Case in 2012. The Evolution report will be one element of the Safety Case. This report is the first detailed description of the expected evolution of a KBS-3V repository located at a depth of -420 m in crystalline rock at the Olkiluoto site. The information in this report will be updated in 2009 and 2011. The repository is designed for the disposal of spent fuel from the two reactors at Loviisa and the three at the Olkiluoto power plant. The expected amount of spent fuel is approximately 5500 tU encapsulated in approximately 3000 copper canisters. The repository is assumed to function as designed and all canisters are intact at deposition time (main scenario). The evolution of initially defective canisters is also discussed (main variant). Two climate scenarios are considered: the Weichselian-R, based on the repetition of the last glaciation cycle and the Emissions-M, based on a moderate level of greenhouse gas emissions. The evolution is described in three phases: from the beginning of operations until closure (the operational phase, lasting approximately 100 years), from closure until the onset of the next glaciation (post-closure temperate phase, lasting until ∼13 000 years AP and 170 000 years AP) and from the onset of the next glaciation until the end of the next glaciation cycle (lasting until ∼125 000 years AP in the Weichselian-R and 450 000 years AP in the Emissions-M scenarios, respectively)