Working Group on Analysis and Management of Accidents (WGAMA)

The Working Group on the Analysis and Management of Accidents (WGAMA) is responsible for activities related to potential accidental situations in nuclear power plants, including the following technical areas: reactor coolant system thermal-hydraulics; design-basis accidents; pre-core melt conditions and progression of accidents and in-vessel phenomena; coolability of over-heated cores; ex-vessel corium interaction with coolant and structures; in-containment combustible gas generation, distribution and potential combustion; physical-chemical behaviour of radioactive species in the primary circuit and the containment; and source term. The activities mainly focus on existing reactors, but also have application for some advanced reactor designs. Priority setting is based on established CSNI criteria and in particular on safety significance and risk and uncertainty considerations.

The WGAMA objective is to assess and, where necessary, strengthen the technical basis needed for the prevention, mitigation and management of potential accidents in nuclear power plants, and to facilitate international convergence on safety issues and accident management analyses and strategies.

In order to fulfil this objective, the Working Group:

  • Exchanges technical experience and information relevant for resolving current or emerging safety issues.
  • Promotes the development of phenomena-based models and codes used for the safety analysis, inclu­ding the performance of benchmarking exercises.
  • Assesses the state of knowledge in areas relevant for the accident analysis.
  • Where needed, promotes research activities aimed to improve such understanding, while supporting the maintenance of expertise and infrastructure in nuclear safety research.

The Working Group report to the Committee on the Safety of Nuclear Installations (CSNI) and assists that Committee with its work. The programme is carried out by small task groups, each set up for performing a specific programme activity under the WGAMA supervision. The output of the Working Group consists of state-of-the-art reports and other technical reports, workshops and conferences and related proceedings, benchmarking exercises and joint research proposals.

The Working Group aims to provide answers as requested by the Committee on Nuclear Regulatory Activities (CNRA), the CSNI and member countries and co-ordinates its work with other NEA bodies, notably with the Working Group on Risk Assessment (WGRISK) for priority setting and potential accident sequences, the Working Group on Operating Experience (WGOE) for emerging issues, the Working Group on Integrity and Ageing of Components and Structures (WGIAGE) for ageing and structure integrity evaluation, the Working Group on Fuel Safety (WGFS) for issues related to fuel safety, and the Working Group on Human and Organisational Factors (WGHOF) for human and organisational aspects of accident management. The WGAMA also works in co-ordination with the Nuclear Science Committee (NSC) on scientific items such as advanced neutronic and thermal-hydraulic methods. 


Hideo Nakamura (JAEA, Japan)

Ahmed Bentaib (IRSN, France)


Martina Adorni, NEA

Publications and reports

WGAMA Members' area (requires password | reminder)

Thermal mixing and fatigue in a T-junction with a dead leg – benchmarking and experimental validation of CFD, Task Leaders: Kristian Angele (Vattenfall), Annalisa Manera (ETZH), Victor Petrov (PSI)

Specialists Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal Hydraulics and Severe Accidents (SWINTH-2024), Task Leader: Sanjeev Gupta (Becker Technologies, Germany)

Harmonisation of Methodologies for System Thermal-Hydraulics Experimental Meta-Data Preservation, Collection and Qualification (THEMPo), Task leader: Alessandro Petruzzi (NINE, Italy)

CFD for Nuclear Reactor Safety Phase 6 – Supporting an enlarged use, Task leaders: Phlippe Freydier (EDF, France), Pierre Ruyer (IRSN, France), Stephan Kelm (FZJ, Germany), Mingjun Wang (XJTU, China)

Application Tests for Realisation of Inverse Uncertainty quantification and validation Methodologies in thermal-hydraulics (ATRIUM), Task Leaders: Lucia Sargentini, Alberto Ghione (CEA, France)

Status Report on Good Practices for Analyses of Design Extension Condition without Significant Fuel Degradation (DEC-A) for Operating Nuclear Power Plants, with WGFS, Task Leaders: Jinzhao Zhang, Maxime Havet (Tractebel, Belgium)

Collaboration with ERMSAR2022 (European Review Meeting on Severe Accident Research), Task Leaders: Fabrizio Gabrielli (KIT, Germany), Luis E. Herranz (CIEMAT, Spain)

Workshop on experimental validation and application of CFD and CMFD codes to Nuclear Reactor Safety Issues (CFD4NRS-9), Task Leader: Yassin Hassan (Texas A&M, USA)

Boundary conditions of scrubbing and remobilisation of fission products in aqueous pools during severe accidents (BCAPFIS), Task Leaders: Luis E. Herranz (CIEMAT, Spain); Sanjeev Gupta (Becker Technologies, Germany)

Status Report on the Reactor Pressure Vessel Integrity Assessment for in-vessel retention, with WGIAGE, Task Leaders: Jiri Zdarek (UJV, Czech Republic), Florian Fichot (IRSN, France)

ISP-51 on advanced core cooling mechanism experiments (ACME), Task Leaders: Yang Jun (HUST, China), Byung-Hyun You (KAERI, Korea)

State-of-Art-Report on Behaviour of Combustible Gases in Severe Accidents, Task Leaders: Sam Gyepi-Garbrah (CNSC, Canada), Ahmed Bentaib (IRSN, France), Seong-Wan Hong (KAERI, Korea), Sanjeev Gupta (Becker Technologies, Germany)