CHRISTA II (safety and safety demonstration concept)
Country / Region: Germany
Begin of project: September 1, 2017
End of project: November 30, 2021
Status of project: June 1, 2021
Generic 3D model of a crystalline host rock overlain by a flat-lying barrier formation with rock salt
Source: BGR
According to the Repository Site Selection Act (StandAG), investigations for the final disposal of radioactive waste in a geologic repository in Germany need to consider three potentially suitable host rocks – rock salt, claystone and crystalline rocks (e.g. granite). A geologic repository for high-level radioactive waste (HLW) must satisfy numerous safety requirements. Concepts that allow to verify the safety of HLW repositories have already been developed for rock salt and claystone. However, no such concept exists yet in Germany for a repository in crystalline rocks. BGE TECHNOLOGY GmbH (BGE TEC), the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS), and the Federal Institute for Geosciences and Natural Resources (BGR), have cooperatively investigated a potential safety concept for crystalline rock in the framework of the CHRISTA project.
In the follow-up project CHRISTA II of the CHRISTA feasibility study a safety and safety demonstration concept for a HWL repository in crystalline rocks in Germany is to be developed in collaboration between the project partners BGE TEC, BGR and GRS. This involves the verification of the integrity of geological and geotechnical barriers, and to investigate whether the existing safety demonstration concepts for rock salt (Projekt KOSINA) and claystone (Projekt ANSICHT) can be adapted to crystalline rocks.
Individual work packages focus on the following tasks:
- WP 1: derivation of a safety strategy from the safety requirements for the disposal of HLW as defined in 2010 and 2020 (EndlSiAnfV) by the Federal Ministry for the Environment, Nature Conversation and Nuclear Safety (BMU), with general aims, planning specifications and technological measures.
- WP 2: development of generic 3D models and parameterisation of the model units for the configuration types “multiple containment providing rock zones (CRZ)” and “overlying CRZ”, as well as a concept derived from the Swedish KBS-3, where the main barrier for the radioactive waste is provided by canisters and a bentonite buffer.
- WP 3: development of generic FEP (Features, Events and Processes) catalogues for the various configuration types. The dependencies between individual FEP will be derived for the FEP catalogue of the modified KBS-3 concept in preparation for future scenario analyses.
- WP 4: derivation of integrity criteria and implementation of integrity analyses for geological and geotechnical barriers
- WP 5: exemplary computation of the radiological safety indicators
WP2 is managed by BGR and addresses amongst others the following questions:
- Which requirements (e.g., extent, hydraulic properties) must the CRZ types “multiple CRZ” and “overlying CRZ” meet?
- Do individual CRZs (type “multiple CRZ”) affect each other in terms of integrity verification?
- Is it possible to state a minimum distance between individual CRZ (type “multiple CRZ”) above which a significant mutual interference can be excluded?
- How far away must individual CRZ components (type “multiple CRZ”) be from hydraulically effective fracture/fault zones?
The current report (DE) describes the generic geological models for the repository concepts "multiple ewG" and "mKBS-3".
