The REMIX (which stands for “regenerated mixture”) fuel is meant to reduce the consumption of natural uranium. It is a non-separated uranium and plutonium mixture obtained by recycling spent fuel, with a small addition of enriched uranium. The new technology allows for reprocessing both plutonium and residual Uranium-235.
The pilot REMIX fuel elements were loaded into standard TVS-2M fuel assemblies. “Alongside standard fuel, there are three fuel assemblies loaded in the reactor core. Each one contains six REMIX fuel elements in addition to over 300 conventional uranium fuel rods per assembly,” said Alexander Ermolaev, Head of Nuclear Safety Department at Balakovo NPP. “This amount of fuel elements is sufficient to confirm the properties of the new type fuel elements in pilot operation mode.”
“This testing procedure is intended to provide experimental data on behavior of REMIX fuel in operation. Besides, we are starting in-pile tests in late summer or early autumn, involving the MBIR reactor at the Research Institute of Atomic Reactors (RIAR) in Dimitrovgrad. Afterwards, the pilot fuel elements will go to the material testing center for post-irradiation studies,” said Andrei Sinyukhin, Deputy General Director of V. Khlopin Radium Institute.
The first fuel element will be extracted from MBIR next March or April. However, the in-pile studies at VVER-1000 reactors will continue for two fuel cycles, so the post-irradiation tests at RIAR are expected to start in 2020–2021. The developers plan to reach a daily burnup of 55 MW per kilogram of uranium. “If REMIX fuel proves efficient and safe, we can start its introduction in VVER reactors in 2030s,” added Andrei Sinyukhin.
The interdivisional strategic project entitled Theoretical and Experimental Justification of REMIX Fuel was started in 2014. The project led by V. Khlopin Radium Institute involved 15 organizations, including Gidropress, Siberian Chemical Plant (SCP), Novosibirsk Chemical Concentrate Plant (NCCP), TVEL Fuel Company, Kurchatov Institute, Mayak, RosEnergoAtom, etc. VNIINM, a major contributor to the project, designed the fuel rods and manufactured REMIX fuel pellets based on the master mixture provided by V. Khlopin Radium Institute. The fuel elements were manufactured at SCP in line with the engineering documents prepared by NCCP.
“A significant advantage of REMIX fuel is that it manifests physical properties identical to those of conventional uranium fuel, when loaded in a VVER 1000 reactor core. Since these properties are essential for safe operation of the reactor, we can easily assume the possibility of loading VVER 1000 reactors solely with REMIX fuel,” said Igor Ryzhov, General Director of V. Khlopin Radium Institute. “Besides, REMIX fuel helps achieve better economies in natural uranium. I think, a 20-25% economy is quite possible. Moreover, the separative work process required to enrich uranium makeup remains almost unchanged. Finally, REMIX fuel is most notable for enabling to recycle plutonium without any material depletion. In other words, REMIX fuel can be repeatedly recycled and reprocessed and therefore reused multiple times, which slows down accumulation of used nuclear fuel.”
