Characterisation Niches

Separate characterisation niches, i.e. short tunnel drifts proceeding from the access tunnel, are also constructed in ONKALO. The first characterisation niche was constructed at 1,475 metres down the tunnel. According to plans, the eventual total number of characterisation niches will be five.

The purpose of the characterisation niches is to house long-term research so that the research work will not disturb the construction. Studies conducted in these characterisation niches are mostly associated with the investigation of the characteristics of the surrounding rock properties and with the monitoring of hydrological and geochemical conditions.

From the characterisation niches, it is possible to drill characterisation holes, i.e. long drillholes into the final disposal depth, which can then be used to examine the rock surrounding ONKALO. These drillholes help in collecting more specific information for planning, for instance, the positioning of the repository.