96/00329 Burn-up measurement of a fuel rod of test bundle for Qinshan Nuclear Power Plant

Abstract

The initial motivation for the development of reprocessing technologies came from the need for obtaining pure fissile material for nuclear weapon production. The most prominent among these is the PUREX (plutonium and uranium extraction) process, still used worldwide to reprocess commercial light water reactor fuels at a few thousand tons per year scale. The fuels dissolved in nitric acid are treated with a tributyl phosphate based solvent, the extracted uranium and plutonium are further purified, and the raffinate is vitrified for a safe final disposal. Plutonium is partly recycled as mixed oxide fuel.Since the beginning of this century, a new generation of nuclear reactors is being developed in the framework of the so-called generation IV initiative.For compliance with the sustainability goals defined for the innovative reactor systems, mainly waste minimization through recycling of all actinides, and for the achievement of these goals, the corresponding fuel cycles will play a central role. The new concept of a grouped actinide separation can be derived from aqueous or pyrochemical partitioning processes. For the aqueous schemes, a direct link to PUREX is obvious, namely, with coextraction 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 developed pyrometallurgy, requires a good understanding of the extraction mechanisms.Pyro-reprocessing, where all actinides are recycled, is based on metallic fuels; they are dissolved in molten salts at around 500–900 °C and actinides are selectively recovered, either by electrorefining or by extraction into a liquid metal phase. The fuels of new generation reactors will, at least in the beginning, most likely be oxides. Thus, for pyroprocesses a head-end reduction step for oxide into metals fuels is needed.A very specific reprocessing technology, the so-called direct use of pressurized water reactor spent fuel in CANDU process, is being developed in Korea. Here, used pressurized water reactor fuel is recycled to CANDU (CANada Deuterium Uranium) reactors after a dry treatment where volatile fission products are removed.