All actual concepts worldwide intend to enclose heat generating waste in a land-based, deep geological disposal.
The underlying safety philosophy is DEFENSE IN DEPTH – a multi-barrier system consisting of:

  • the geological (natural) barrier, the so-called host-rock: granite, clay, salt, tuff
  • the geotechnical barrier (backfilling and closing of drift tunnels and shafts)
  • the technical barrier (disposal canister, optionally with a bentonite overpack) which includes the initial barrier.

Geotechnical and technical barrier together form the engineered barriers.

Key questions in setting the regulatory standards for a deep geological repository include:

  • What should be the desired level of protection for individuals, population and biosphere?
  • For how long must compliance be demonstrated?

Goals widely accepted today are: minimal radiological consequences for 1 Mio. years!

This can be achieved

  • by total retention of radio-nuclides within the technical barrier (ideal case: source term Q = 0)
  • by mitigation of the transport through geotechnical and natural barriers (ideal case: permeability P = 0)