Spent Fuel Dissolution and Reprocessing Processes

The initial motivation for the development of reprocessing technologies was to obtain pure fissile material for nuclear weapon production. Most prominent is the PUREX (Plutonium and Uranium Extraction) process, still used today world-wide to reprocess commercial LWR (Light Water Reactor) fuels at a few thousand tons per year scale. The fuels dissolved in nitric acid are contacted with a TBP (Tributyl Phosphate) based solvent, the extracted uranium and plutonium are further purified and the raffinate vitrified for a safe final disposal. Plutonium is partly recycled as MOX fuel. Since the beginning of this century a new generation of nuclear reactors is being developed in the frame of the so-called generation IV initiative. To comply with the sustainability goals defined for the innovative reactor systems mainly the waste minimization through recycling of all actinides, the corresponding fuel cycles will play a central role in trying to achieve these goals. The new concept of a grouped actinide separation can be derived from aqueous or pyro-chemical partitioning processes. For the aqueous schemes a direct link to PUREX is obvious, namely with co-extraction of Np. The extraction of the remaining actinides can be achieved by using specially designed solvents based on phosphine oxide or diamide molecules. A major focus is on the very challenging separation of lanthanides from the trivalent actinides. The process implementation, especially for the less pyro-metallurgy, require a good basic understanding on the extraction mechanisms. Pyro-reprocessing where all actinides are recycled is based on metallic fuels, those are dissolved in molten salts at around 500-900°C and actinides are selectively recovered, either by electrorefining or extraction into a liquid metal phase. The fuels of new generation reactors will, at least in the beginning, most likely be oxides. Thus, for pyro-processes a head-end reduction step for oxide- into metals fuels is needed. A very specific reprocessing technology, the so-called DUPIC (Direct Use of Pressurized Water Reactor Spent Fuel in CANDU) process, is being developed in Korea. Here used PWR (Pressurized Water Reactor) fuel is recycled to CANDU (CANada Deuterium Uranium) reactors after a dry treatment where volatile fission products are being removed.JRC.E.5-Nuclear chemistr