NEA Mandates and Structures

Expert Group on Reactor Systems Multi-Physics (EGMUP)

Mandate (Document reference):

• The NSC Working Party on Scientific Issues and Uncertainty Analysis of Reactor Systems (WPRS): Proposal for Prioritisation and Restructuring [NEA/NSC/WPRS/DOC(2020)19]
• Summary record of the 31^st meeting of the Nuclear Science Committee in September 2020 [NEA/SEN/NSC(2020)20] 
• Mandate of the WPRS Expert Group on Reactor Systems Multi-Physics (EGMUP) [NEA/NSC/WPRS/DOC(2021)2]

Mandate (Document extract):

Extract from document [NEA/NSC/WPRS/DOC(2021)2]

Background

As a result of the prioritisation process, a reorganisation of NSC activities was performed under the guidance of the NSC Bureau. This has resulted in the disbandment of the NSC Expert Group on Multi-Physics Experimental Data, Benchmarks and Validation (EGMPEBV), the Expert Group on Radiation Transport and Shielding (WPRS-RTS), the Expert Group on Reactor Physics and Advanced Nuclear Systems (WPRS-RPANS) and the Expert Group on Uncertainty Analysis in Modelling (WPRS-UAM). Two new bodies have been created to replace them: the Expert Group on Physics of Reactor Systems (WPRS-EGPRS) and the Expert Group on Reactor Systems MUlti-Physics (WPRS-EGMUP).

Scope

Under the guidance of the Working Party on Scientific Issues and Uncertainty Analysis of Reactor Systems (WPRS), the Expert Group on Reactor Systems MUlti-Physics (EGMUP) will advance the state-of the-art in establishing processes and procedures for certifying experimental data and benchmarking multi-physics multi-scale modelling and simulation (M&S). Coupled behaviours of two or more of the following physics will include, but are not limited to the following:

• reactor physics;
• thermal-hydraulics;
• fuel performance;
• structural mechanics and;
• materials chemistry.

Multi-physics aspects of both steady-state and transients conditions of existing and advanced nuclear systems will be examined along with uncertainty quantification and propagation through different scale (multi-scale M&S) and different physics phenomena (multi-physics M&S).

Objectives

The Expert Group on Reactor Systems MUlti-Physics (EGMUP) will provide recommendations to the WPRS and the nuclear community on the scientific development needs (data and methods, validation experiments, scenario studies) for multi-physics and multi-scale M&S, including sensitivity and uncertainty methodology for analysis of different reactor systems and scenarios. Guidance and processes to certify experimental data for multi-physics multi-scale M&S and to apply this data to the benchmarking of models will be developed.

To fulfil the above the expert group will provide the following:

• standardised benchmark models with detailed uncertainty evaluations and uncertainty a methodology guidelines;
• guidance on best practices to combine high fidelity and low fidelity simulation tools;
• framework and consensus recommendations for validating multi-physics simulations;
• sensitivity and uncertainty methods to facilitate quantification and ranking of coupled physics;
• evaluation methods for uncertainty impacts of the following parameters on multi-physics simulations:

  • data (e.g. geometry, materials);

  • numerical methods;

  • physical models;

• training opportunities to demonstrate validation principles and practices; and
• demonstrations of the validation recommendations for specific applications.

To support its activities, the group will collect and evaluate multi-physics data from available integral facilities and Nuclear Power Plant (NPP) experimental data. Analytical and numerical benchmarking will also be used to fulfil the objectives.

Working Methods

The EGMUP will report to the Working Party on Scientific issues and Uncertainty Analysis of Reactor Systems (WPRS). The EGMUP will meet once per year, with additional meetings in support of particular activities such as task forces reporting to the EGMUP.

Links to other NEA bodies and international projects

The EGMUP will report to the Working Party on Scientific Issues and Uncertainty Analysis of Reactor Systems (WPRS) and will liaise closely with other relevant NEA bodies, in particular the WPRS Expert Group on Physics of Reactor Systems (EGPRS) and the Expert Group on Reactor Core Thermal-hydraulics and Mechanics (EGTHM) as well as those bodies operating under the guidance of the Nuclear Science Committee (NSC) and the Committee on the Safety of Nuclear Installations (CSNI). The objective will be to ensure that the respective programmes are complementary and to provide advice and support where required and undertake common work where appropriate. Links with the NSC Working Party on Multi-scale Modelling of Fuels and Structural Materials for Nuclear Systems (WPMM)¹ will assist with issues related to fuel performance and structural materials analysis. Close collaboration with the NSC Working Party on Scientific Issues of Advanced Fuel Cycles (WPFC) and its expert groups will be maintained.

Deliverables

The deliverables of the EGMUP are the following:

• summary reports on both novel and traditional multi-physics M&S tools and uncertainty treatment;
• summary reports on experimental data for validation of multi-physics M&S tools;
• summary report on multi-national efforts in the development of novel multi-physics M&S tools;
• report on processes for evaluating existing experimental data for multi-physics M&S tools;
• report on the metrics and processes for developing benchmark models from certified experimental data;
• report on the guidelines and applicability of certified data and benchmark models for validation of M&S tools and data with application specific examples;
• development of a database of evaluated experimental multi-physics data and benchmark models;
• complete the Multi-Physics Pellet Cladding Mechanical Interaction Validation (MPCMIV) benchmark;
• complete the Rostov-2 VVER-1000 Multi-Physics Transient benchmark;
• complete the TVA WB1 Multi-Cycle Depletion benchmark;
• complete Phase II exercises (transient exercises) of MHTGR Benchmark;
• complete Phase III of the LWR-Uncertainty Analysis in Modelling (UAM) benchmark;
• complete Phase III of the SFR-UAM benchmark;
• comparative analysis reports for Oskarshamn-2 benchmark;
• comparative analysis reports for Kalinin-3 benchmark;
• comparative analysis report for Phase II exercises (transient exercises) of MHTGR benchmark;
• organise yearly UAM and other multi-physics benchmark workshops;
• organise biannual education workshop on multi-physics model validation.

¹  Change of name forthcoming for the WPMM following the NSC prioritisation process: Working Party on Scientific Issues of Nuclear Fuels and Materials (WPFM).