Photo courtesy of JAEA
From December 10 to 12, 2025, the vibrant city of Mito, Japan, served as a hub for cutting-edge discussions on nuclear safety at the 10th Workshop on Computational Fluid Dynamics for Nuclear Reactor Safety Issues (CFD4NRS-10). Organized by the Thermohydraulic Safety Research Group of the Japan Atomic Energy Agency (JAEA), this significant event welcomed over 100 participants, bringing together experts from research institutions, technical support organizations, industry, and academic circles from across the globe. The diverse representation reinforced the collaborative spirit that defines the international nuclear safety community.
This year marked a historic milestone as it was the first time the workshop was held in Japan. It was organized under the auspices of the Nuclear Energy Agency’s Working Group on Analysis and Management of Accidents (WGAMA). The opening session featured remarks from General Chairs Hisashi Ninokata of the Polytechnic of Milan and Tokyo Tech, alongside Yasuteru Sibamoto of JAEA. Their insights, along with contributions from Martina Adorni of NEA and Satoshi Abe of JAEA, set a dynamic tone for the workshop, highlighting the shared commitment to advancing nuclear safety.
The significance of this workshop was amplified by its coincidence with the 25th anniversary of WGAMA. Over the past quarter-century, WGAMA has been pivotal in enhancing methodologies for nuclear accident prevention, mitigation, and management. This long-standing group has fostered the development of high-fidelity computational codes and innovative experimental programs, nurturing a vibrant international community dedicated to nuclear safety.
During the three-day event, participants engaged in nearly 70 technical presentations spread across 13 sessions, interspersed with three thought-provoking keynote lectures and a special session. The range of topics was impressively broad, covering uncertainty quantification, validation techniques, multiphase and multiphysics simulations, innovative experimental methodologies, and practical applications in regulatory frameworks.
The keynote lectures featured notable experts who shared invaluable insights. Dr. Pierre Ruyer from the Autorité de Sûreté Nucléaire et de Radioprotection (ASNR) addressed the pressing challenges surrounding uncertainty quantification in computational fluid dynamics (CFD). Dr. Martina Adorni from NEA underscored the critical role of collaborative experimental programs and joint code validation initiatives, while Dr. Jan-Patrice Simoneau of Électricité de France (EDF) examined the rising significance of CFD in both existing and next-generation reactor designs. Furthermore, Dr. Victor Petrov from the Paul Scherrer Institut (PSI) led a special session focused on the NEA WGAMA T-Junction CFD Benchmark, emphasizing the importance of benchmarking efforts for the global community.
Amidst the technical discussions, a heartfelt acknowledgment was made for Dr. Jan-Patrice Simoneau, celebrating his decades of remarkable contributions to both the field of nuclear safety and the CFD4NRS workshops. His influence and expertise have significantly shaped the discourse in this critical sector.
As the workshop concluded, it became clear that the work of the international nuclear safety community is far from over. The challenges lying ahead beckon ongoing collaboration and innovative thinking. All participants were encouraged to maintain their engagement with WGAMA and the CFD Task Group. They were invited to partake in future benchmarks, support experimental projects, and invest in nurturing the next generation of researchers and engineers dedicated to ensuring nuclear safety.