In nuclear power plants, fuel rods are used to supply energy. Atomic nuclei in the fuel elements split into fission products, a process that yields energy and highly active substances. After three to five years in a reactor, the fuel elements are spent and require to be replaced as their content of fissile U-235 has become too low. They can either be disposed of directly or reprocessed. In the latter case, the uranium and plutonium contained in the fuel elements is recovered for further energy production.
The Swiss reactor operators have contracts with foreign plants for reprocessing of around 1200 tonnes of spent fuel. This corresponds more or less to the volume produced in the five Swiss power plants in around 15 years. If spent fuel is not reprocessed in the future, it will require to be disposed of as high-level waste.
By 2005, around 1200 tonnes (approximately thirty percent of the total spent fuel expected from the existing power plants) had been transported abroad for reprocessing. The wastes that are separated during this process have to be accepted back by Switzerland. The Nuclear Energy Act that entered into force in February 2005 prohibits the further export of spent fuel for reprocessing until the year 2016.
Container for deep disposal of spent fuel from boiling water reactors (Leibstadt and Mühleberg NPPs). (Image: Nagra)
Comparison: Fresh and spent fuel element