Dynamic methodologies for probabilistic safety assessment (PSA) and risk assessment continue to advance steadily. A number of (primarily research-oriented) case studies have been published, demonstrating the additional capabilities and insights that dynamic PSA approaches can deliver, while advances in computational power and methods allow problems of increasing scale to be tackled. Recognising that both technical and organisational obstacles to the practical deployment of dynamic PSA remain, the Working Group on Risk Assessment (WGRISK) of the NEA Committee on the Safety of Nuclear Installations (CSNI) is carrying out a task to assess the potential role of currently available and emerging dynamic PSA tools and methodologies in risk-informed decision making, to identify the practical challenges for their application to support such decisions, and to evaluate the outlook for overcoming these challenges.

With these goals, the WGRISK organised an international workshop Dynamic Probabilistic Safety Assessment and its Role in Risk-Informed Decision Making hosted by the US Nuclear Regulatory Commission (US NRC) in Rockville, MD, United States, on 16-17 November 2023.

The objective of the workshop was to provide a forum to discuss topics such as:

• experiences with the application of dynamic PSA and the use of these results by decision makers;
• the integration of dynamic PSA results in risk-informed decision making;
• current risk management decisions and safety issues where traditional (non-dynamic) PSA approaches have potential shortcomings;
• the technical and organisational challenges to the practical deployment of dynamic PSA and the outlook for addressing these.

The scope of the risk and safety issues includes all scopes of nuclear power plant PSA, nuclear installations safety, the associated safety issues, and the diverse decisions made by stakeholders including licensees and regulatory bodies.

The workshop consisted of a combination of presentation sessions and panel/discussion sessions.

• Technical challenges for practical dynamic PSA, e.g. coverage of rare events, human factor-related models, computational issues, methods to identify important insights from the vast amounts of data produced by dynamic PSA simulations.
• Dynamic PSA decision-making cases, relating to Level 1/2/3 PSA, any plant operational modes, internal events and external hazards, as well as diverse specific concerns such as spent fuel pools, equipment recovery, portable equipment deployment, accident management, and site-level risk.
• Experience with the use of dynamic PSA for nuclear or any other application.

Workshop Organising Committee

Michelle Gonzalez, US NRC, USA (Chair)

Tanja Eraerds, GRS, Germany (Co-Chair)

Vinh Dang, PSI, Switzerland (WGRISK Chair)

The organisers kindly invite specialists from operating organisations, regulatory authorities, vendors, design organisations, technical support organisations (TSOs), research institutes, practitioners and consultants. The workshop is open to participants from the OECD member countries and NEA member countries, strategic partners, invitees, and partner international organisations. The workshop will be enriched through the participation of:

• PSA experts well-versed in the challenges and issues involving currently established PSA methods and tools;
• PSA experts familiar with approaches for treating dynamic issues in the classic PSA framework;
• PSA research and development community;
• decision makers and stakeholders;
• academia (universities and research centres).