LUT University in Lappeenranta, Finland, hosted the second meetings of the Programme Review Group (PRG) and Management Board (MB) of the SYSTHER Joint Project from 16 to 18 June 2026.
SYSTHER addresses key thermal‑hydraulic safety phenomena and accident behaviours – especially for passive systems and small modular reactors (SMRs) – through integrated experiments and code validation.
The meetings brought together project partners to review progress across the experimental programmes, assess ongoing analytical activities, and define the next steps of the project. Detailed updates were provided on the different test programmes, including PKL, PWR-PACTEL, PASI, MOTEL and MISTRA facilities, along with their respective specifications and recent results.
A key focus of the discussions was the continued development of the project’s programme of work and benchmarking activities. Partners reviewed recent test results and addressed analytical activities and international benchmark exercises, including ongoing work related to International Standard Problems (ISPs) and joint analytical workshops. Participants exchanged views on methodologies for scaling, data interpretation and reactor-scale transposition, highlighting the importance of maintaining a strong link between experimental observations and safety analysis at plant level.
These activities aim to strengthen the validation basis for system codes and enhance the understanding of thermal-hydraulic phenomena relevant to nuclear reactor safety, with focus on nuclear power plants applications.
An important highlight of the meeting was the visit to the LUT experimental facilities used within the SYSTHER project. Participants had the opportunity to observe first-hand the PWR PACTEL, PASI and MOTEL installations supporting the programme. These facilities play a central role in investigating thermal-hydraulic behaviour, natural circulation and passive safety system performance under representative conditions.
The visit further reinforced the importance of preserving experimental research infrastructures in supporting international collaboration and advancing nuclear safety knowledge.
The SYSTHER Joint Project continues to provide a unique platform for international collaboration, combining high-quality experimental data and advanced analytical work to improve the understanding of complex thermal-hydraulic phenomena and support the safety of nuclear installations.
