The DELISA-LTO project is a game-changer for the nuclear energy sector, particularly for VVER reactors, as it dives deep into the implications of long-term operation (LTO) on safety and material integrity. Funded by the Horizon Europe programme, this initiative unites nine institutions across five countries—Czech Republic, Slovakia, Hungary, Ukraine, and Finland—aiming to extend the operational life of Water-Water Energetic Reactors by an additional 40 years. This collaboration isn’t just about keeping the lights on; it’s about doing so without compromising safety, a critical factor in gaining public trust in nuclear energy.
One of the standout features of the DELISA-LTO project is its focus on thermal ageing, a phenomenon that can severely affect the structural integrity of reactor components. The project zeroes in on the Reactor Pressure Vessel, the heart of the VVER, which is irreplaceable and highly susceptible to thermal and irradiation embrittlement. Maintaining its integrity is non-negotiable. The project also highlights the vulnerabilities of Reactor Internals and Heat Exchange Tubes, which face issues like thermal ageing and stress corrosion cracking. With the costs and complexities associated with replacing these components, the emphasis on proper maintenance becomes crystal clear.
The insights gained from the project are particularly relevant when we consider the differences in swelling behavior between VVER-440 and VVER-1000 reactors. While VVER-440 reactors show minimal swelling, the VVER-1000, especially in the Core Baffle, experiences significant swelling due to higher neutron fluxes. This swelling can potentially compromise cooling efficiency and safety, which is a cause for concern as these reactors age. The advanced simulation tools that DELISA-LTO employs will offer predictive insights into swelling strains, allowing operators to develop effective maintenance strategies that are grounded in real operational data.
The project’s experimental focus on thermal ageing of steel used in VVERs is another crucial aspect. By conducting tensile tests, impact testing, and even the innovative Small Punch Test, researchers can evaluate how materials evolve over extended periods. This rigorous assessment of mechanical properties is vital in ensuring that the materials used in these reactors can withstand the rigors of long-term operation.
Moreover, the development of Non-Destructive Testing (NDT) techniques within DELISA-LTO is a significant leap forward. These methods are essential for routine maintenance and monitoring the health of reactor components without causing any damage. Techniques like Eddy Current Testing and Ultrasonic Testing are being refined to detect early signs of degradation, ensuring that operators have the information they need to make informed decisions about maintenance and repairs.
As VVER reactors continue to push the boundaries of their design lifetimes, the DELISA-LTO project stands as a beacon of hope for the nuclear energy sector. The insights gained from this project will not only enhance the safety and reliability of existing reactors but also provide a roadmap for future developments. By addressing critical challenges such as thermal ageing and material degradation, DELISA-LTO is paving the way for a more sustainable and trusted nuclear energy landscape in Europe. The stakes are high, and the project’s outcomes could very well shape the future of energy production in the region, making nuclear a viable part of the transition to a low-carbon economy.
