Savannah River Plant Thorium Processing Experience

Some experience in ²³³U-Th processing is available from past operations at government sites and may be of interest to the current reevaluation of thorium fuel cycles. In five separate campaigns between 1964 and 1970, the Savannah River Plant processed ∼240 tons (MT) of thorium, irradiated as aluminum-clad metal and oxide and recovered ∼580 kg of total uranium. Satisfactory processing routes were devised for a solvent extraction plant that normally processes enriched uranium and previously was a Purex plant. In the initial campaigns, a dilute tributyl phosphate (TBP) flowsheet recovered only uranium, and thorium was sent to waste. In later campaigns, a modified Thorex solvent extraction flowsheet recovered both uranium and thorium. Satisfactory processing required specific attention to the slow dissolving rate of ThO₂, the presence of highly radioactive ²³³Pa, solvent extraction flowsheet constraints to avoid formation of two organic phases in the thorium-TBP systems, the ingrowth of gamma-emitting daughters of ²³²U, and ²³³U criticality.