[en] In the five separate thorium processing campaigns conducted at SRP, thorium was processed in equipment and facilities which had been converted in 1959 to recover highly enriched uranium. Two different flowsheets were used and a total of approximately 240 tons of thorium and 580 kg of uranium was processed. In the first two campaigns (initial campaigns), uranium was recovered with a dilute 3.5% TBP flowsheet and the thorium was sent to waste. In these two initial campaigns, the irradiation conditions for the thorium metal resulted in concentrations of 40 to 50 ppM and 200 ppM ²³²U in different batches of the product uranium. In the first of the last three campaigns (Thorex campaigns), thorium metal and thorium oxide were processed. Thorium oxide was processed in the remaining two Thorex campaigns. The three Thorex campaigns used 30% TBP to recover both uranium and thorium. Irradiation conditions were set to produce a concentration of 4 to 7 ppM ²³²U. Dissolving rates for thorium metal exceeded 4 tons/day and with thorium sent to waste, solvent extraction rates increased and posed no limits. Dissolving and Thorex solvent extraction rates were approximately 1 ton/day when thorium oxide feed was used. Studies to increase the dissolving rates indicated that a small amount of MgO (1%) in the thorium oxide would be beneficial. Seven tons of thorium oxide with 1% MgO did give some promise of increased dissolving rates. Satisfactory flowsheets were developed, losses were satisfactory, and decontamination from fission products and protactinium were adequate. About the only unexpected event during the campaigns was the appearance of thorium dibutyl phosphate precipitates that appeared in the second thorium cycle during the first thorex campaigns and interfered with operation. The system slowly returned to normal when the temperature was reduced