The aim of the study was to select a set of geological environments to represent the range of plausible repository host environments in England and Wales that might be identified through the Government's MRWS process, and to identify the main technical issues that would need to be considered when evaluating the safety of a repository in each of the environments.

The following broad technical issues were identified:

• influence of different wasteform types on the design of the engineered barrier system (EBS)
• interactions between engineered components
• interactions between the EBS and the host rock
• impact of groundwater/porewater on EBS materials (including the impact of saline water)
• duration for which EBS materials maintain their function (durability)
• interactions between gas and groundwater (or porewater)
• characterising the site adequately
• demonstrating long-term stability
• impact of repository resaturation

It was concluded that the design of a repository should be matched to the characteristics of its host geological environment. When designing a repository, it is necessary to take into account the highly coupled nature of many processes. Most issues associated with the performance of EBS materials under repository conditions are reasonably well understood.

A summary of the project (354 KB) and the full report (2.77 MB) are available here.