The purpose of creating an underground laboratory is, on one hand, to verify the characteristics of the Callovo-Oxfordian formation, at the scale of the proposed installation, and, on the other hand, to subject it to a number of solicitations to verify its robustness.

Current programmes are aimed at completing the geologic and hydro­dynamic characterization of the site. As a first step, the homogeneity and continuity of the formation will be verified, and it will be checked for the absence of faults likely to create hydraulic shorts within the Callovo — Oxfordian formation. Subsequently, the local hydrogeologic regimes will be analysed, along with their possible evolution, using network drillings that register ground water behaviour during the operations, in particular during the drilling of the underground laboratory access shafts.

Migration data have also been used in the safety computations; they influence diffusion and the delay coefficients. In both cases, measurements were done on samples at the centimetre scale. Determinations done in situ, or from larger sized samples, are necessary to verify the validity of the values obtained. Another important issue is access to water. The chemical form of different species depends on water chemistry, of the processes regulating it in a natural environment. One of the difficulties is the reliable determination of the characteristics of a given water as it is very difficult to extract the water from small samples. The underground laboratory provides direct access; sampling and measurement devices can help in a better determination of this chemistry. Another aspect that can be studied in an underground laboratory is geomechanics, first to ascertain that construction can be undertaken safely, but also to study damaged zones on the walls of the construction susceptible to form hydraulic shorts.

Exogenous materials would also be placed in the disposal, among which is the waste itself. Various interactions that they might cause must also be studied in situ, in particular the effects due to thermal release as well as materials ageing. The experimental programme being prepared is geared to the study of the various mechanisms that come into play and of the behaviour of the various materials components.

The modelling and simulation approach, and the 3D representations, must be studied; this holds also for any possible evolution in the conception of the constructions.

A set of means are thus available to demonstrate the safety of disposal installations; a large research effort is required, implying numerous teams.