WASTE PACKAGES IN REPOSITORIES: FEATURES, EVENTS, PROCESSES

Climate changes, ice ages, human intrusions, changing of host rock properties, crack-formation, water ingress and others may have effects on the integrity of the waste package.

The design of the repository has to fulfil fundamental SAFETY CRITERIA:

• REDUNDANCY which is provided by a MULTIPLE BARRIER system
• DIVERSITY by a COMBINATION of natural and technical barriers
• The FAIL SAFE criterion for passive systems like barriers must be fulfilled by ROBUSTNESS
• To mitigate the consequences of damages from COMMON MODE FAILURE two measures can be foreseen:
  • a limitation of activity inventory per each waste package and
  • spatially separated disposal

Safety requirements include

• continuous optimization of the waste disposal concept from planning to final closure of  the repository (in the extreme case of total reversibility: take-out the canisters)
• retrieve ability of waste packages during operation time of repository as well as
• control and safety system for the time post closure: identification of a waste package
• recovery by miners for long years after final closure (German Safety Requirements: 500 years)

Nevertheless, for a given site, many “what if’s” and uncertainties exist, considering a timeframe of 1 Mio years.

In the case of water access corrosion takes place with loss of integrity, chemical reactions with canister surface, hydrogen generation, crack formation …