Posiva Oy is studying the Finnish bedrock for the geological disposal of spent nuclear fuel. The study is based on the site selection research programme started originally in 1983. The programme is in accordance with the decision in principle by the Council of State in 1983 and aims at the selection of one site in 2000. Four sites, Hastholmen in Loviisa, Kivetty in Aanekoski, Olkiluoto in Eurajoki and Romuvaara in Kuhmo, have been studied in detail. This report summarises the results of the site investigations carried out at Olkiluoto.

The report outlines the current design and safety concept for the planned repository. It summarises the approach used to formulate scenarios for the evolution of the disposal system over time, describes these scenarios and presents the main models and computer codes used to analyse them. It also discusses compliance with Finnish regulatory requirements for long-term safety of a geological repository and gives the main evidence, arguments and analyses that lead to confidence, on the part of Posiva, in the long-term safety of the planned repository

This second version of the Olkiluoto Site Report, produced by the OMTF (Olkiluoto Modelling Task Force), updates the Olkiluoto Site Report 2004 (Posiva 2005) with the data and knowledge obtained up to December 2005.<br/>The main product of the modelling has been to develop a descriptive model of the site (the Site Descriptive Model), i.e. a model describing the geometry, properties of the bedrock and the water and the associated interacting processes and mechanisms.