Under the guidance of the Nuclear Science Committee (NSC), the Working Party on Scientific Issues and Uncertainty Analysis of Reactor Systems (WPRS) studies the reactor physics, thermal hydraulics, radiation transport and shielding, and multiphysics aspects including coupling to fuel performance models in present and future nuclear power systems. The working party also studies the uncertainties associated with the modelling of these phenomena, particularly the modelling of reactor transient events.
The WPRS structure of expert groups, technical review groups, and benchmark groups is shown in the structure graph below.
The WPRS's objective is to provide member countries with up-to-date information to preserve knowledge on and develop consensus in the following areas:
The WPRS and its expert groups coordinate several benchmark activities on reactor single- and multi-physics. The annual WPRS Benchmarks Workshops (typically one week with two parallel tracks of technical sessions) serve to exchange on the status of the benchmarks activities and discuss benchmark specification updates.
Click on elements in graph above to jump directly to a specific WPRS activity.
| Chair | Kostadin Ivanov (USA) |
| Vice-Chair | Hakim Ferroukhi (CHE) |
| Members | All NEA member countries |
| Full participant | European Commission (under the NEA Statute) |
| Observer (international organisation) |
International Atomic Energy Agency (by agreement) |
WPRS and associated Expert Group meetings are held approximately every twelve months.
Next meeting: 23rd Annual Meeting of the WPRS, 16-20 February 2026.
The participants' working area is now hosted on MyNEA SharePoint
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The MyNEA End User Guide is available online here: User's guide: myNEA
Prior to the creation of the WPRS, a number of reactor physics benchmarks were undertaken. Reactor types considered include, but are not limited to the following:
The WPRS liaises closely with other NEA working groups, especially those operating under the guidance of the Committee for Technical and Economic Studies on Nuclear Energy Development and the Fuel Cycle (NDC) and the Committee on the Safety of Nuclear Installations (CSNI) in order to ensure the respective work programmes are complementary and to provide advice and support where required and undertake common work where appropriate. Particularly close working relationships are maintained with the Working Party on Scientific Issues of Advanced Fuel Cycles (WPFC), the Working Party on Materials Science Issues in Nuclear Fuels and Structural Materials (WPFM), Working Party on Nuclear Criticality Safety (WPNCS), and the Working Party on International Nuclear Data Evaluation Co-operation (WPEC).
The current structure of the working party and its expert groups results from a major restructuring in 2020 in which the following expert groups were integrated in WPRS:
Until 2024, the WPRS mandated the Expert Group on Reactor Fuel Performance (EGRFP) to perform specific tasks associated with fuel performance aspects of present and future nuclear power systems. This group was reorganized aiming at creating a more impactful and relevant organization of experts working in fuel performance by merging the EGRFP with the Expert Group on Fuel Materials (EGFM).
Joint Project on Waste Integration for Small and Advanced Reactor Designs (WISARD)
