Solvent treatment

Used solvent contains degradation products and residual radioactive impurities. The main degradation product from TBP is di-butyl phosphoric acid, whose sodium salt is soluble in the aqueous phase. So, the solvent is re-generated using alkaline solutions: before recycling, the solvent is washed with sodium carbonate and sodium hydroxide (Fig. 16.17).

To reduce the losses of TBP in the aqueous phases but also to prevent potential reactions of the degradation products with nitrates during the concentration

16.16 Overview of the whole PUREX process including the routes for wastes (Source: AREVA).

16.17 Solvent management (La Hague reprocessing plant UP3) (Source: AREVA, International Seminar on Nuclear Fuel Cycle, 19 October 2010, INSTN).

through evaporation of the refined products, the aqueous phases coming the extraction are stripped by a thinner (hydrocarbide C12H26), which removes residual TBP and TBP degradation products.