Working Party on Scientific Issues and Uncertainty Analysis of Reactor Systems (WPRS)


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, fuel performance, and radiation transport and shielding 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. Its structure of expert groups, technical review groups, and benchmark groups are shown in the 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:

Reactor physics aspects considered include:

Radiation transport and shielding aspects, which are addressed in the Expert Group on Physics of Reactor Systems (EGPRS), include:

Reactor core thermal-hydraulics  aspects include:

  • methodologies for modelling on different scales
  • technics for high to low fidelity/resolution model data exchange (Hi2Lo)
  • fluid structural mechanical interactions for normal and deformed cores
  • preservation of experimental data

Fuel performance aspects include:

Multi-physics aspects include:

  • coupled neutronics/thermal hydraulics transient modelling
  • benchmark comparisons
  • sensitivity analysis.


WPRS Organisation

Chair Kostadin Ivanov (USA)
Vice-Chair Hakim Ferroukhi (SUI)

All NEA member countries  WPRS members' working area

Full participant European Commission (under the NEA Statute)

Observer (international organisation)

International Atomic Energy Agency (by agreement)



NEA Secretariat: Oliver Buss and Ian Hill


Meetings, Workshops and Conferences

WPRS and associated Expert Group meetings are held approximately every twelve months. 

Next meeting: 19th Meeting of WPRS, 21st - 25th of Febuary 2022.


Members' working area

WPRS members' working area (password protected | reminder)


Related Initiatives

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:

  • present generation light water reactors (LWRs) with advanced and innovative fuels, evolutionary and innovative LWRs and heavy water reactors (HWRs)
  • advanced reactor systems
  • accelerator-driven (sub-critical) and critical systems for waste transmutation.

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 Multi-scale Modelling of Fuels and Structural Materials for Nuclear Systems (WPMM) and other relevant NSC working parties.


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: