Repository Siting

The siting of a repository is one of the basic objectives of the deep repository development programme. The site must satisfy not only requirements concerning rock properties, primarily isolating capacity and the ability to capture radioactive substances which might leak from the repository but also a number of “non-geological” requirements, such as conflicts of interest, repository acceptability by the general public, the technical feasibility of the construction of surface facilities and site accessibility. As regards the rock environment, a rock formation must be selected at the beginning of the site selection process which is typical for the country as a whole and both the geological development and the position of which lead to the conclusion that it will possess the required properties which, moreover, will remain stable during the whole of the required time period.

The first stage of the Czech deep repository development programme (the research stage) was completed at the beginning of the 2000s and consisted of two phases: regional mapping and suitable candidate site selection. The work, however, was interrupted for 5 years following a Government Decision on geological investigation and will resume this year. During the recess, geological investigation was carried out at the Melechov test site to verify certain techniques and methods which might be subsequently employed for geological investigation at the various candidate sites. Furthermore, two new localities have been added to the original list of candidate sites: the Boletice and Hradiště former military areas.

According to the Czech concept of the management of radioactive waste and spent nuclear fuel, one condition must be met in order to resume repository development with the aim of selecting two sites to be subjected to detailed geological investigation, namely the consent of the communities affected.

Geological investigation of the sites is planned as follows: After selecting a suitable site, an area of 3-5km² will be identified for use as a future deep repository at a depth of approximately 500 metres beneath the surface. Work will be carried out using a grid technique in squares of 100x100 metres over 3 months; samples will be taken at depths of 1-2 metres and/or 3-5 metres and geophysical measurements will be taken from the surface. As a result, a number of places will be identified at which several boreholes of approximately 500 metres and one borehole of 1000 metres will be drilled. The drilling work will be carried out over several months following the consent of the landowners concerned.

The final aim of the repository reference project will be the construction of an underground facility in rock-cut caverns which will be connected by a vertical shaft for the transport of workers and materials. A suitable terrain and geological conditions proven by means of preliminary safety analysis form essential preconditions for the success of the project.

The repository siting process consists of two stages: research (the search for potentially suitable localities and rock environment properties) and investigation (the collection and verification of data on geological structures and the underground environment prior to the commencement of construction work as well as during the construction phase).

The geological investigation stage consists of three phases: search, investigation and detailed investigation. The search for a suitable location for a deep repository commenced soon after the commissioning of the first nuclear power units in the then Czechoslovakia, i.e. in the 1980s. The first studies concerning the assessment of rock environment potential in the Czech Republic were performed in the 1990s.