In the European Union, about 200 nuclear power plants (NPPs) are currently feeding electricity into the grids with more than half of them exceeding a lifetime of 40 years by 2020. In order to ensure the needed electricity supply for the next decades, the EU is targeting lifetime extensions of existing plants to up to 80 years. A safe long-term operation of NPPs, however, requires effective safety reviews and reliable tools for estimating the remaining lifetime. Launched in June 2017, the new research project NOMAD will make a significant contribution to ensuring long-term safety for the environment and European citizens by developing a novel and reliable evaluation tool giving insight into the actual state of material degradation in the individual power plant. One of the irreplaceable parts protecting the environment from radioactive radiation and therefore limiting the lifetime of NPPs, is the reactor pressure vessel (RPV). “The fuel elements inside the reactor can cause embrittlement of the pressure vessel walls in the long term,” said Dr Madalina Rabung from Fraunhofer IZFP who coordinates the NOMAD consortium. “The aim of the nondestructive evaluation system to be developed in NOMAD is to determine the location and characterise the nature of material damage.” So far, safety routines have been based on monitoring concepts in which small samples are taken already during the manufacturing process of the vessel. These small samples are then intentionally exposed to increased radioactive radiation in order to detect – in anticipation of reality – potential deterioration of the material properties. "However, the material used is not always homogeneous which makes it difficult to use such samples as a solid reference for the entire pressure vessel," Dr Rabung added. In order to achieve the target of complementing and exceeding the information obtained by destructive tests, the NOMAD partners will apply a total of six nondestructive evaluation methods including electrical, ultrasonic, acoustic and micro-magnetic techniques. The results of these examinations will be compared, correlated and validated in a novel software tool which will be of great use for energy companies in the long run. Putting great emphasis on knowledge transfer and the formation of research alliances and networks throughout Europe, the majority of the ten NOMAD consortium partners are members of NUGENIA, which is one of the key interest groups of NPP operators serving as a central platform to connect and share experiences in the field.
power plant, nondestructive, EURATOM, nuclear, safety