Specialists at Russia’s AA Bochvar Research Institute of Inorganic Materials (VNIINM) and the Siberian Chemical Combine (SCC) – both part of state nuclear corporation Rosatom’s fuel company Tvel – have confirmed that it is possible to obtain powders of uranium dioxide using direct microwave denitration. This method makes it possible to avoid the formation of liquid radioactive waste (LRW) with a high content of actinides. Earlier the technology was successfully tested on a laboratory scale jointly by the Vernadsky Institute of Geochemistry and Analytical Chemistry of the Royal Academy of Sciences (Geokhi RAS) and the Research Institute of Atomic Reactors (Niiar) to obtain mixed oxides of uranium, plutonium and neptunium.

Microwave denitration is the process of obtaining oxides from salts, which is not accompanied by the formation of secondary liquid radioactive waste, Tvel said. “The technology is effective, and in laboratory installations, we have proved that it is suitable for the production of powders of mixed uranium-plutonium oxides. At SCC, we installed a full-scale installation, tested and produced powders of the required composition,” said  VNIINM expert Andrei Shadrin.

The installation for microwave denitration was established as part of research and development to justify the technology for the used fuel reprocessing module, which is the third stage of the creation of pilot energy complex (ODEK) as SCC, part of the Proryv (Breakthrough) project intended to demonstrate the closed nuclear fuel cycle.

VNIINM and SCC also confirmed the separation of uranium and plutonium nitrate crystals from a nitrate solution on a pilot scale free from fission products. The experiments were carried out at SCC, using a refinery extraction and crystallisation stand also built as part of the Breakthrough project. The stand is used to support the development of closed-cycle fuel technology for fast reactors and for testing various options for extraction and crystallisation. VNIINM scientists conducted an experimental test to achieve the joint crystallisation of refined uranium and plutonium during the reprocessing of used nuclear fuel, which makes it possible to avoid separating plutonium.