The reprocessing involves extracting reusable uranium and plutonium from the spent nuclear fuel so that it can be used again
- By Linton Levy -
Commerical radioactive waste from the UK is now being shipped back to Japan. The waste, from the Sellafield nuclear complex, is a by-product of nuclear fuel which was sent to the UK from Japan for reprocessing during the 1980s and 1990s.
The reprocessing involves extracting reusable uranium and plutonium from the spent nuclear fuel so that it can be used again. Over the next decade, the UK intends sending other high-level waste back to European countries.
The Sellafield site is home to two nuclear fuel reprocessing plants. The first deals with Magnox fuel from Britain's early nuclear reactors (such as the Calder Hall power station at Sellafield). The second is the Thermal Oxide Reprocessing Plant or Thorp, as it is known. Thorp deals with fuel from British Advanced Gas Cooled Reactors (AGR) and Light Water Reactor fuel from around the world.
Having spent approximately five years in a reactor, the 'spent' (used) fuel is removed and placed in fuel storage ponds at the power station to allow it to cool and for the radiation levels to decrease. After this cooling period, the fuel is loaded into specially constructed secure containers called 'flasks'. These flasks are then transported to Sellafield either by road, rail or from overseas customers by sea in purpose built ships for reprocessing at Sellafield.
Upon arrival at Sellafield, the fuel is received into a storage area, where it is again stored in ponds to further allow radiation levels to decrease. Having undergone its additional storage period (depending on its type) the fuel is then sheared (chopped up) and dissolved in nitric acid. The 'dissolver liquor' which is produced is then chemically separated to produce three separate elements – uranium, plutonium and fission products.
The uranium and plutonium can then be reused to make new fuel while the fission products are transferred to the downstream Vitrification plant where it is mixed with glass and stored as high level waste.