// Long-term Safety Studies

CHRISTA

Feasibility study for the development of a safety and verification methodology for a repository for heat-generating waste in a crystalline rock formation in Germany

In the CHRISTA project, an investigation was conducted to determine whether the concept of deep geological disposal with high containment capacity, as required in current safety regulations and focused on salt and clay formations, could also be applied to crystalline rock. Additionally, the project explored the extent to which the concept of disposal in Scandinavian crystalline rocks, which has already been developed for specific sites in Sweden and Finland and is known as the KBS-3 concept, could be transferred to the German context. The KBS-3 concept primarily relies on the containment effectiveness of copper-clad containers.

As a result, it was found that if crystalline rocks were to be considered as an option for selecting a repository site while adhering to the basic principles of the German safety requirements, two viable options emerge: one involves finding a crystalline formation covered by layers with high containment capacity (referred to as the "overlying ewG" type), and the other involves identifying multiple smaller areas within a crystalline formation with high containment capacity (referred to as the "multiple ewG" type). The integrity criteria mentioned in the safety requirements can be applied to both of these ewG types.

However, some necessary geological information for evaluating which of these options are feasible in Germany is lacking. Therefore, in the CHRISTA project, existing exploration data and applicable exploration methods were compiled. Regarding the transferability of the Swedish/Finnish KBS-3 concept, it was found that direct transfer to German conditions without further adjustments is not possible.