The process of decommissioning a nuclear power station involves several intricate steps, including defueling and dismantling, to ensure the safe removal and storage of radioactive materials.
After a nuclear power station ceases operation, the first step in the decommissioning process is defueling. This involves removing the fuel assemblies from deep within the reactor cores. Due to their high radioactivity, the fuel assemblies need to be handled with extreme care. A heavily-shielded crane, known as the charging machine, is used to lift the assemblies out of the reactor. Once removed, the fuel assemblies are placed in a steel-lined cell for dismantling, where the used fuel is removed from its casings.
The work of defueling and dismantling is carried out remotely by operators stationed in a control room. They peer through a thick window filled with a radiation absorbing fluid to perform their tasks. After dismantling, the fuel elements are left in deep, clear ponds to cool before being placed in rugged containers for transportation to interim storage at facilities like Sellafield.
The process of defueling and dismantling can take several years and is a costly endeavor. For example, removing all the fuel assemblies from the two reactors at Hinkley Point B is expected to cost around £1bn. However, it is a necessary step to ensure the safe handling and storage of radioactive materials.
Once defueling is complete, the site is handed over to the Nuclear Decommissioning Authority (NDA). The NDA is responsible for managing the decommissioning process, which includes the safe removal of remaining structures and the remediation of the site. At Hinkley Point A, one of the UK’s first-generation nuclear sites, the reactor buildings still stand tall after being shut down in 2000. However, other buildings, including the turbine hall, have been removed, leaving behind a vacant space. The fuel storage ponds have been drained, cleaned, and painted to reduce radiation risks.
In conclusion, the decommissioning of a nuclear power station involves a meticulous process of defueling and dismantling to ensure the safe removal and storage of radioactive materials. This process is carried out with extreme care and involves the use of specialized equipment and remote operations. Once the defueling is complete, the site is handed over to the relevant authorities for further decommissioning and site remediation.