What is transmutation
Transmutation is a complex process in which a material is irradiated and converted into a substance with a shorter half-life.
When uranium atoms capture neutrons, either nuclear fission or the formation of heavier elements occurs. The heavier elements are generally highly radioactive and emit dangerous radiation for a relatively long time. Exposing these heavier elements to radiation can accelerate their decay and thus shorten the storage time in a deep repository. This process is called transmutation.
The technology of transmutation is not entirely straightforward and there is not yet a really good solution. The principle is that you have a particle accelerator and accelerate protons that hit lead. The lead in turn emits neutrons which then irradiate the heavy radioactive substances. The process leads to the material being transformed into substances with a shorter half-life - a transmutation has taken place.