A breakthrough in making nuclear power plants greener: Paks II also benefits from the innovations of Roszatom

The five-year trial operation of Russian accident-tolerant nuclear fuel in Rostov has been successfully completed, according to a statement from Roszatom. The accident-resistant version of MOX fuel was developed for closed nuclear fuel cycle technology. The significance of the project lies in the fact that this is the first time in Russia that a high-power reactor producing electricity in a commercial plant has begun operating with this fuel.

According to the statement, three innovative accident-resistant fuel assemblies have been installed in the VVER-1000 reactor of Unit 1 at the Balakovo Nuclear Power Plant.

In the test operation that has just begun, the MOX fuel is being tested in its accident-resistant form. This step is crucial to achieving the strategic goal of integrating not only innovative fast neutron reactors but also the conventional light-water thermal reactors currently in operation into the closed fuel cycle in the future.

As the accident-resistant version of MOX fuel is also suitable for the Paks II nuclear power plant currently under construction,

This means that the Hungarian power station could also play a part in closing the fuel cycle in the future: in other words, it could use fuel produced by reprocessing spent nuclear fuel, such as that from the Paks Nuclear Power Plant.

It will be possible to switch to the production of fuel cartridges without human contact

The statement also explains the significance of MOX technology: it enables the use of by-products from the conventional fuel cycle – such as depleted uranium (the uranium-238 isotope), a by-product of uranium enrichment, and plutonium extracted from spent fuel – in the production of fresh fuel.

The accident-resistant fuel, made from a chromium-coated zirconium alloy, not only enhances the stability and safety of the reactor and the core in the event of severe accidents exceeding the design basis. Thanks to its surface properties, it enables the transition to fully automated, hands-free production of fuel assemblies, eliminating the manual labour currently still required for their manufacture. In order to minimise radiation exposure to production staff, the manufacture of mixed uranium-plutonium fuel must be fully automated.

The world's stockpiles of depleted uranium are being utilised

The first mixed uranium-plutonium fuel for the Roszatom was the REMIX fuel (from the English term „regenerated mixture”), developed for VVER reactors. Its trial operation at the Balakovo Nuclear Power Plant was successfully completed in March 2026. The use of MOX fuel in VVER reactors opens up entirely new possibilities. This is because the fuel’s plutonium content is several times higher than that of REMIX fuel, and it contains depleted uranium instead of enriched uranium. All this makes it possible to optimise fuel production costs, utilise regenerated fissile materials more flexibly, and make use of the depleted uranium stocks accumulated worldwide.

The demand for natural uranium is set to fall by more than 20%

According to calculations by experts at Roszatom, if a VVER fuel assembly contains MOX fuel in 25% and standard-enriched uranium fuel in the remaining 75% (U-235), including the regenerated fuel, then in terms of plutonium content it will be equivalent to a REMIX fuel assembly containing entirely uranium-plutonium fuel.

The hybrid fuel described above has been named ‘heterogeneous REMIX fuel’. According to experts from TVEL’s Roszatom nuclear fuel manufacturing division, calculations for new power stations equipped with VVER-1200 reactors show that the use of heterogeneous REMIX fuel reduces the requirement for natural uranium by more than 20%over the entire operating life of the nuclear power plant.

Spent fuel from one reactor is used to cool the fresh fuel in the other reactor

Alexander Ugryumov, TVEL’s Senior Vice-President for Scientific Research and Development, emphasised that the strategic objective of the Roszatom project and our vision is to create a two-component nuclear energy system. „In this system, fast and thermal neutron reactors operate in a closed fuel cycle, with the spent fuel from one type of reactor serving as the raw material for the fresh fuel of the other type.”

He pointed out that the company’s scientific and technological research and development projects relating to the Roszatom VVER fuel are designed to achieve this objective. „We are currently designing a fifth-generation fuel assembly for the VVER-1200 model, and testing of the aforementioned chromium-coated, accident-tolerant MOX fuel has begun,” he said.

Work is also underway to develop manufacturing technology for fuel pellets produced without human contact. „We plan to combine these new materials technology, design and manufacturing processes into a single product,” emphasised the vice-president.