Recovery Process of Actinides from Genuine Spent Nuclear Fuel using TODGA and BTBP Extractants - JRC-ITU-TN-2008/70

Abstract

During the last decades a growing concern about greenhouse gas emissions from fossil fuels has arisen. Nuclear power is an energy source with a low contribution to the greenhouse effect and is in this sense therefore a better alternative for electricity production. The waste from nuclear power is however highly radiotoxic and has to be stored for more than 100000 years until the radiotoxicity has decreased to an acceptable level. With partitioning and transmutation the purpose is to separate the nuclides that contribute most to the long-term radiotoxicity and to transform them into short lived or stable nuclides. If partitioning and transmutation are successfully applied the storage time for nuclear waste can be reduced to less than 1000 years. Essential for the partitioning and transmutation is an efficient separation of the minor actinides. In this work, group separation of the trivalent lanthanides and actinides from a PUREX raffinate has been demonstrated by means of solvent extraction, using the TODGA extracting agent. Excellent separation was obtained and the recoveries of the actinides exceeded 99.9%. Separation of the actinides from the lanthanides was also carried out, using the CyMe4-BTBP extracting agent. Results achieving high actinide recovery of more than 99.9%, were acquired as well as efficient separation from the lanthanides. A comparison between alpha and gamma radiolysis was performed with the CyMe4- BTBP organic phase. The study showed that the solution was more sensitive to the gamma radiation. The effect of varying alpha dose rates was also investigated but no significant difference was observed in the interval tested (50-1000 Gy/h). Burnup calculations, done to estimate the metal concentration in a process, together with loading experiments show however that the loading capacity of the CyMe4-BTBP organic phase is very limited and needs to be improved if fuels with higher minor actinide content are to be treated. Two computer programs for process calculations were developed. The programs were successfully used to calculate the extraction profiles for the CyMe4-BTBP test.