Mr. Tromm, how large is the current amount of highly radioactive material in Germany? And how much low-level and intermediate-level radioactive waste is there?
Between 10,000 and 10,500 tons of highly radioactive waste are stored in Germany. These are the spent fuel elements. The total amount corresponds to a volume of about 27,000 cubic meters. The amount of low-level and medium-level radioactive waste is around 120,000 cubic meters. These are mainly activated steels from the dismantled nuclear power plants. The materials were exposed to strong neutron radiation. It is possible that around 180,000 cubic meters will be added in the coming years, so that the amount of low- and intermediate-level radioactive materials will total around 300,000 cubic meters.
Where is the radioactive waste currently stored?
This takes place primarily at the sites of the nuclear power plants themselves. A decision was made against castor transport, which brings the waste to a central interim storage facility. The Konrad shaft repository in Salzgitter is planned for the low-level and intermediate-level waste.
However, the Konrad repository is not scheduled to go into operation until 2028.
That is how long the materials are stored in halls on the premises of the nuclear power plants that are being dismantled. It is currently being discussed whether the capacity in Konrad is sufficient if the 126,000 drums of radioactive waste from the dilapidated ASSE II mine are added. According to the Site Selection Act, it would be entirely permissible to pack low-level and medium-level radioactive materials together with high-level radioactive waste in a repository.
What criteria does a repository for high-level radioactive waste have to meet in order to be approved?
The goal of a repository is, of course, to protect people and the environment from damage caused by ionizing radiation. And that’s why the barrier concept was developed. First, there is the technical barrier, designed to ensure security for a thousand years. These include stable containers that are stored in underground tunnels. They are designed to prevent radionuclides from escaping. To protect against corrosion, for example as a result of water seeping in, the tunnel is filled with bentonite, for example. The clay mixture swells as soon as it comes into contact with water and closes all cavities. It also binds leaking radionuclides.
And then there is the geological barrier, i.e. the rock itself into which the tunnel was inserted.
The isolating rock must be several hundred meters thick. In Germany, three rock formations come into question: salt, clay and granite.
There must be no cracks, no water penetration and it must be geologically stable.
The geological stability of the repository is the most important criterion. Avoiding cracks in granite rock is very difficult. Then you have to use particularly corrosion-resistant copper containers, as is done in the Finnish repository Olkiluoto. It depends on the rock, so the technical barriers are adjusted accordingly. You can’t just put a Castor container in an underground gallery.
Does the highly radioactive nuclear waste really have to be stored safely underground for a million years? Sweden and Finland have agreed on 100,000 years.