On the path to fuel advancement

Russian nuclear fuel has proven to be “of quality and reliability” says TVEL Fuel Company, a part of Russia’s Rosatom State Atomic Energy Corporation. Today, every sixth reactor in the world operates powered by TVEL fuel. With a solid portfolio of long-term orders, TVEL continues to offer its customers “improved nuclear fuel that strengthens effectiveness, as well as technical and performance indicators of nuclear power plants,” it says. In addition, Russian specialists are actively engaged in the development of new promising nuclear fuel types.

The growing level of competition in the nuclear energy sector has resulted in the need for new rules of the game. “TVEL Fuel Company makes every effort to offer its customers nuclear fuel with the highest technical and economic features,” it says. One of the most important principles followed by TVEL is its continuous push for improvement of its products and supply of new and more efficient technologies. To this end, the company annually invests in R&D and improves fuel for all types of reactors in operation. Today this principle is implemented within the framework of cooperation with all its foreign partners.

The most impressive example of this, the company says, is Paks nuclear power plant in Hungary. Four power units with VVER-440 Russian-designed reactors are in operation here. At present this is the only nuclear power facility in the world using this type of reactor, which operates in an extended 15-month fuel cycle. The project to increase the fuel cycle from 12 months to 15 months won the European Quality Innovation Award in the ‘Innovations of large-scale enterprises’ category. The increase in the Paks facility’s fuel cycle duration contributed to improved cost effectiveness and efficiency of the power plant’s operation, while meeting all safety requirements.

For the implementation of the project, TVEL carried out the design and licencing of improved nuclear fuel and improvement of fuel cycles when operating at 1485MW of the core thermal power. In turn, their Hungarian partners developed physical 15-month fuel cycle implementation project. An analysis and assessment was carried out to determine the safety of the Paks nuclear power plant operation. As a result of the extended assessment the Hungarian plant was deemed to be safe across the four units, it also meant there were fewer scheduled preventative repairs of equipment and reduced lead times. This increased the capacity factor of the plant too, said operators. 

However, TVEL’s input into the successful operation of Paks power facility won’t stop there. “The next step will be the development of a unique modification of nuclear fuel for Hungarian customers,” said TVEL. In November 2017 TVEL Fuel Company and the company operating the Paks facility, MVM Paks NPP, signed an engineering service contract for the introduction of modernised fuel assemblies. This was for the second generation at the station, during which TVEL will develop a new fuel assembly modification with increased uranium capacity. “This will help optimise water-uranium ratio compared with the assemblies currently being used. This will increase the economic efficiency of the power plant while maintaining current fuel cycle parameters.”

According to TVEL Fuel Company president, Natalia Nikipelova, the Hungarian partner is actively exploring the possibility of increasing the efficiency of nuclear fuel and is directly involved in the technical part of the implementation of this project. “TVEL Fuel Company of Rosatom gives priority to science and innovative development and offers its customers the advanced nuclear fuel modifications, constantly improving technical and economic features,” she said.

New fuel for Finland

Fortum Power and Heat Oy (Finland) is another partner that TVEL will provide modified nuclear fuel to. The Finnish company is operating the Loviisa nuclear power plant with VVER-440 Russian-designed reactors. Today, the modern second generation uranium-gadolinium fuel for VVER-440 reactors supplied to the plant is produced by PJSC MSZ (TVEL’s fuel manufacturing enterprise in Elektrostal, Moscow region). Recently, the parties have agreed on the introduction of modernised second generation fuel assemblies at the operating units. Similar to the Paks facility, Rosatom fuel company will develop a new type of the fuel assemblies with increased uranium capacity and optimised water-uranium ratio, again in comparison with the currently used assemblies. Once again the benefit, the company said, is “increased economic efficiency of the power units”.

The basis for the new modification of the second generation jacket FA for VVER-440, proposed for the Loviisa nuclear power plant and the Hungary’s Paks facility, is initially the same technical solution. However, the final fabrication products and fuel supply diagrams for power units will differ in a number of ways, based on the individual requirements of our customers, explained Alexander Ugryumov, vice president for R&D at TVEL Fuel Company.

New fuel is a competitive advantage

Today TVEL offers its customers nuclear fuel for more than just VVER reactors. The Russian company is actively developing the fuel market for Western-designed reactors too. “As a result,” it said, “the product is, on the one hand, compatible with those types of reactors, and on the other its fuel technology and assembly design is genetically different from foreign equivalents, given that it’s based on the best achievements in the fuel field for VVER reactors. The TVS-K (fuel rods assembled in the shape of a square) is not only on par with traditional types of fuel for PWR, but also has a number of competitive advantages,” the company continued.

According to its technical specialist working at the company, the original solutions for the spacer grid and the frame structure give the fuel sufficient rigidity and allow it to be used for up to five years, maintaining its original geometry, and achieving a greater burn-up depth (around 70MW*day/kgU) based upon unconditional safety and reliability of operation.

Russian TVS-K has already been acclaimed by Swedish nuclear power operators from Vattenfall. The Ringhals nuclear power plant became a pilot facility, where a test batch of Russian fuel was supplied. “In 2016, the Swedish partners from Vattenfall signed a fuel supply contract with TVEL,” said the company, to begin in 2021. “Moreover, the current model of TVS-K assemblies operated at Ringhals NPP was developed with a conservative approach and has a potential for further optimisation,” said TVEL.

Increased enrichment

Another type of fuel with great potential is that with increased enrichment (more than 5%). TVEL is close to coming up with a practical solution related to using it within VVER-1000 and VVER-1200 reactors, it says. With increasing reactor lifespans when operating in an open cycle and with a 5% limit on enrichment, the average burn-up decreases and the relative specific consumption of natural uranium increases. “Russian-designed fuel assemblies are substantiated for operation up to 60-65MW*day/kgU, but the resource cannot be fully capitalised upon due to fuel cycle limitations. The transition to using fuel with enrichment of more than 5% remedies the situation. Technical and economic studies have already been conducted, and according to the results it is clear that when switching to an average feed enrichment of 5.45% and 5.8-6.3% in 18- and 24-month cycles, accordingly, it will be possible to significantly increase the average burn-up and reduce the number of fuel assemblies used,” TVEL says.

The fuel cycle with highly enriched fuel does not require a change in the amount of natural uranium consumed, leading to a reduction in the duration of new nuclear fuel loading and spent nuclear fuel assembly unloading operations at the power unit. In addition, during nuclear fuel use there is no need for significant modernisation of equipment for the production of fuel assemblies with TPO and equipment intended for the transportation and storage of fuel at VVER-1000/1200.

Tolerant fuel

Accidents at the Chernobyl and Fukushima power facilities have shown a particular danger of the steam-zirconium reaction that occurs when the temperature of the fuel element cladding rises after the loss of coolant and outsurge of reactivity. Almost immediately, developments for protection against steam-zirconium reaction have been noted in all countries with advanced nuclear power engineering. The term Accident Tolerant Fuel (ATF) appeared after the accident at Fukushima. The International Atomic Energy Agency says this fuel must be able to operate both under normal operating conditions and importantly if the loss of coolant occurs. “TVEL Fuel Company sees the ways of solving this global problem in modifying zirconium fuel element cladding surface, using steel fuel element cladding and creating new fuel compositions with high thermal conductivity,” the company concluded.  

About TVEL
Rosatom Fuel Company TVEL is one of the leaders in the production of nuclear fuel and uranium enrichment services. It develops, manufactures and supplies nuclear fuel that meets international reliability indicators for Russian and foreign nuclear power plants with VVER-440, VVER-1000/1200, BN-600, BN-800, RBMK-1000 reactors, Western-design PWR reactors, research reactors, ship nuclear steam generating plants. TVEL Fuel Company’s share in the fabrication market currently stands at 16%.