The Swiss site selection process for geological repositories is a stepwise approach defined by the ‘Sectoral Plan for Deep Geological Repositories’. The narrowing down process begins with the selection of broad geological siting regions (Stage 1). The evaluation of the various potential regions is performed on the basis of safety and engineering feasibility criteria explicitly defined in the Sectoral Plan. Stage 1 was completed in 2011 with the approval by the Federal Government of the three (for the HLW repository) and six (for the L/ILW repository) potential siting regions proposed by Nagra.

The narrowing-down process continued with Stage 2, the focus of which is the selection of at least two potential siting regions for each type of repository. Criteria addressing spatial planning and environmental aspects were also considered in this Stage for the siting of the surface facilities. Nagra's proposals were published in early 2015 and they are currently under review. It is expected that the authorities will conclude their review early 2017 and the Federal Government will issue its decision after broad consultation in 2018.

Stage 3 has as a goal the selection of one site for each type of repository. For each repository a general licence application will be submitted which must be approved by the government, ratified by parliament, and is subject to a facultative national referendum.

An overview of the methodology developed for Stage 2, its implementation and the selection of the proposed sites is presented in this paper.