(10)Nuclear energy is part of the future energy sources in a number of Member States, as part of their decarbonisation efforts. The scenarios assessed by the Commission lead to a decarbonised energy system based on renewables to a very large extent and on nuclear energy with a stable installed capacity compared to current levels. As the nuclear installations being currently exploited age, they need safety upgrades to extend operational life as well as newly built nuclear installations to replace obsolete installations. This is a continuous process that should ensure the availability of the necessary capacity for the decarbonisation of the energy system by 2050 and beyond this date as needed. Accordingly, significant investments in nuclear energy will be needed throughout the period until 2050 and beyond. It is necessary to ensure that new nuclear power plants use the most advanced solutions resulting from technological progress. The technical screening criteria for such new nuclear power plants should therefore provide for regular reviews of each investment project, and for technical parameters that correspond to the best-available technology in view of the outcomes of sustained research and development efforts and the continuous improvements of technologies. Specific dates should be defined to ensure phasing in of new technologies compatible with sustainable decarbonisation as soon as they become available.