The plant used PUREX chemistry (based on tributyl phosphate (TBP)) to extract plutonium and uranium from used nuclear fuel originating primarily from Magnox reactors.

[1] The plant was originally constructed and operated by the United Kingdom Atomic Energy Authority (UKAEA), but in 1971 control was transferred to British Nuclear Fuels Limited (BNFL).

B205 ceased operations on 17 July 2022, when it was announced that it had worked through the remaining spent Magnox fuel stockpiles.

The aqueous stream was conditioned to the correct temperature and acidity and then passed to the first mixer settler system where fission products were separated from the uranium (U) and plutonium (Pu) by extraction of the U/Pu into the solvent phase comprising tri-butyl-phosphate in odourless kerosene.

[8] In 2020 due to coronavirus, Sellafield Ltd announced that the Magnox reprocessing plant will undergo a controlled shutdown to ensure less maintenance when it is eventually restarted.

Whereas turning the facility off quickly in a response to reduced staff members on-site has a possibility to result in unnecessary maintenance or repair work.