The NEA Committee on the Safety of Nuclear Installations (CSNI) has for over 50 years worked to advance the understanding of accident phenomena, safety analysis and risk-informed decision making. To disseminate knowledge in these fields, it holds regular seminars in a series called, Transfer of Thermal-Hydraulic and Severe Accident Knowledge Gained Through CSNI Activities. The fifth such seminar (THICKET-5) was held in Lucca, Italy, from 19 to 23 May 2025.
The event gathered 35 participants from 12 countries, which included NEA member countries as well as Singapore and Saudi Arabia, and 26 lecturers from 11 countries.
The work carried out under the aegis of the CSNI includes benchmarks, International Standard Problems (ISPs), experimental counterpart tests, methodology development, analysis of the state of the art and perspectives, best practice guidelines, technical opinion papers and more. Participants at THICKET-5 addressed in particular the topics of design basis and severe accidents, fuel behaviour and multi-physics modelling, passive safety systems and emerging reactor designs, probabilistic safety assessments, research related to the Fukushima Daiichi accident and future perspectives.
The first day included an introduction to the seminar and an overview of past contributions. The second focused on deterministic safety analysis, scaling, uncertainty methods and multiphysics codes, while the third explored reactor accident phenomena such as boiling heat transfer, boron issues, and 3D modelling, followed by sessions on risk-informed safety decisions. During the last two days, participants discussed emerging reactor designs, passive systems, progress in joint NEA safety research projects, insights from post-Fukushima research, source term studies, and the future of nuclear safety.
The seminar was designed to foster dialogue, deepen understanding, and trigger discussion and networking among lecturers and participants.
It was organised by the NEA’s Working Group on the Analysis and Management of Accidents (WGAMA) in collaboration with the Working Group on Fuel Safety (WGFS) and the Working Group on Risk Assessment (WGRISK), as well as many dedicated individuals around the world.
