The models, codes, and databases that support the present and previous safety assessments are the result of considerable research and development work.

The models and codes used are discussed and their reliability described in corresponding specific reports e.g., (Nagra 2024o, Nagra 2024k, Nagra 2024n, Nagra 2024p). This implies, in accordance with the safety assessment principles (Section 4.1):

• Accuracy and verification:

  In general, verification of the codes, which provides confidence in the accuracy of the results, is documented in the respective reports. Modifications made to the codes over the course of Nagra’s programme have also been tested and documented.

• Applicability and validation:

  Validation of codes and databases involves testing their consistency, as far as possible, with available information, including laboratory and field experiments, general scientific understanding, experience from other safety assessments, and observations from nature. Natural analogues and palaeohydrogeological models have been used to evaluate and, where possible, reduce uncertainties arising from the temporal scales of concern. Finally, use has been made of expert judgement and critical internal and external review. Where available, alternative conceptual models have been considered.

• Correct application:

  Care has been taken that the codes and models used in support of the post-closure safety case have been applied correctly and in line with their intended use.