To assess the long-term radiological consequences, international safety analyses use the so-called REQUIRED LIFE EXPECTANCY OF WASTE PACKAGES.

The TABLE shows the values used in different projects.

The favourite canister material for granite and clay is copper.
For apparent reasons copper can not be used in salt.
Otherwise, steel cannot be used in granite because of the most likely access of water and the unavoidable corrosion.

If salt as host rock is selected, creeping and compacting can be taken into account. This leads to the expectation, that the host rock alone provides a tight enclosure after some time. Under such assumptions, the canister has practically no importance for the long-term immobilization.

This explains the great differences in the required life expectancy:

  • more than 100.000 years for copper in granite,
  • 500 years for steel in salt.

In the last time, the assumed corrosion velocity of copper came under harsh criticism.

New data may jeopardize former calculations and together with them the choice of copper as canister material!