Four different aspects contribute to the overall risk caused by the direct disposal of spent fuel elements:

  1. Release of radioactive material into the biosphere.
  2. Release of toxic material into the biosphere.
  3. Agglomeration of fissile material with potential to criticality.
  4. Diversion of spent fuel elements and manufacturing of explosives with reactor plutonium.

Since toxicity does not decay, a HLW repository remains a giant, permanently dangerous toxic waste repository, also when the radiological impact due to radioactive decay became negligible.

Do not reduce risk considerations to radiological consequences only! Plutonium is equally dangerous as toxic and as fissile material as well!

International consensus was gained on the fundamental design features of a HLW repository:
- deep geological disposal
- multibarrier system.

Long-term safety requires at least 2 long-term stable retention barriers!
For instance, the combination of a geological and a technical barrier.

But there is no ideal host rock!
The logic conclusion:
The waste package should be leak-proof for the whole disposal time!

The SIAMANT@ BASIS CONCEPT is the best concept known today to meet the safety requirements.