Expert Group on Physics of Reactor Systems (EGPRS)
View of an element being loaded into a ZEBRA (zero energy breeder reactor assembly).


Under the guidance of the Working Party on Scientific Issues of Reactor Systems (WPRS), the Physics of Reactor Systems (EGPRS) will perform specific tasks associated with reactor physics aspects of present and future nuclear power systems. Reactor types considered include, but are not limited to the following:

  • Present generation light-water reactors (LWRs) and heavy-water reactors (HWRs) with advanced and innovative fuels;
  • Evolutionary and innovative LWRs and HWRs, including small modular reactors (SMRs);
  • High-temperature gas-cooled reactors (HTGRs);
  • Fast-spectrum systems and advanced reactor systems, including fluoride salt-cooled high-temperature reactor (FHRs) and molten salt reactors (MSRs); and
  • Accelerator-driven (sub-critical) and critical systems for waste transmutation.


The objective of the EGPRS is to provide expert advice to the WPRS and the nuclear community on the development needs (data and methods, validation experiments, scenario studies) for different reactor systems.

The fulfilment of this objective notably entails providing specific technical information on:

  • Core reactivity characteristics, including fuel depletion effects;
  • Core power/flux distributions; and
  • Core dynamics and reactivity control.

This technical information will generally be derived from a combination of direct experimental evidence and/or the results of theoretical benchmark analyses using accurate, validated modelling methods. In either case the availability of suitable experimental data is a fundamental requirement. A key objective of the EGPRS will therefore be to help identify, evaluate and preserve this type of experimental data. In this context, the EGPRS will monitor, steer and support the continued development of the International Reactor Physics Experiments Evaluation database (IRPhE).

Where required, the EGPRS will provide safety scenario studies for advanced systems and fuels. In this context, it will liaise closely with the Working Party on Scientific Issues of the Fuel Cycle (WPFC).

Working documents

EGRPANS working area  (password protected | reminder)

Recent/current activities

Previously completed or related activities

  • VHBuFC: Expert Group on very high burn-ups in LWRs (completed)

Meetings, workshops and conferences

Information related to past and upcoming meetings is available in the EGRFP working area  (password protected | reminder)