Phase 1 was completed in 2019 and identified areas of Thermal Hydraulics research and development in the UK through the following programme.
All published deliverables from this work are available to download using the document picture links below or visit the publications site for all exportable documents
1. State of the Art Review
2. User Requirements
3. Model and Facility Specification
4. Innovative Research and Development
Thermal Hydraulics Modelling Review
This review highlights a selection of thermal hydraulics phenomena, including: turbulence, heat transfer, bubble and droplet thermodynamics and transport, flow induced vibration, surface effects and ageing of structures, together with the multiscale aspects linking them.
There remain a large number of challenges in modelling nuclear thermal hydraulic phenomena, but there is a growing potential and interest in using high fidelity tools for nuclear reactor design.
This work identified and reviewed the user requirements that should drive development of the UK thermal hydraulics capability.
A wide range of reactor developers, academic institutions, service providers and the UK regulatory body covering a diversity of reactor types and development aspirations were approached to provide feedback and input.
These user requirements were used to develop the specification documents for the test facility and model development.
Thermal Hydraulic Facility Specification
A high level test facility specification was developed that bounds a wide range of technologies and research areas to meet the near and long term needs in the UK.
The UK Atomic Energy Authority (UKAEA) has been appointed by the UK and Welsh governments to develop the outline design of the proposed £40 million national thermal hydraulic research and testing facility, to be built in north Wales as announced in the Nuclear Sector Deal.
Modelling Capability Specification
Using a systematic approach, we developed the user requirements into a set of 34 research and development proposals. This included a workshop that enabled UK experts to propose solutions to the modelling challenges.
The total volume of research and development included in this specification far exceeds the budget available, and so the outputs are intended to be used to ‘build’ a programme of work to meet a particular aim or focus.
SCWR Benchmark Study
The University of Sheffield participated in the IAEA Coordinated Research Project (CRP) in Supercritical Water-cooled Reactor (SCWR) thermal hydraulics benchmarking exercise.
This evaluated the performance of modelling SCWR conditions including strongly buoyancy-influenced flows, and expanded UK engagement in international initiatives.
Aerosol Dynamics in Cover Gas Region
Liquid Metal Fast Reactors (LMFRs) include an inert gas cover layer above the liquid metal pool. Understanding the aerosol dynamics and heat transfer in the cover gas is important to understanding the behaviour of the core.
The University of Sheffield used existing UK sodium aerosol test data to develop and improve the predictive capability of the cover gas region behaviour in sodium reactors.
University of Manchester Sodium Research
Research was carried out at the University of Manchester from 1980 to 1993 on sodium surface emissivity and the heat transfer across a sodium aerosol-laden cover gas.
Professor Jackson, who led the original experimental measurements, has summarised the results of this research. This provides valuable insight and data for current research and studies of heat transfer across the cover gas region of liquid metal reactors.
Novel Coarse-Grid Subchannel CFD (SubChCFD)
The vision of this research is to develop a modern, computational fluid dynamics (CFD) based, subchannel framework for nuclear power plants. Our solution is based on a standard CFD solver whilst embracing existing subchannel code correlations.
SubChCFD, developed by the University of Sheffield, is a smart mix of CFD and subchannel methodologies. This has the potential to bridge the gap between advanced CFD methods and traditional one-dimensional (1D) approaches.
Meshless Methods for Nuclear Thermal Hydraulics
Detailed CFD modelling of Nuclear Power Plants requires large meshes to model the complex geometry. Smoothed Particle Hydrodynamics (SPH) is a novel meshless method of modelling highly non-linear deformations and multiphase flows with complex geometries.
Recent SPH developments by the University of Manchester mean that this meshless method could be applied to nuclear thermal hydraulics in realistic geometries.
Rod Bundle Boil-off
Two-phase flows feature extensively in the context of nuclear thermal hydraulics and present a significant increase in complexity over single-phase flows.
The University of Manchester undertook an initial assessment of the current CFD capability to model rod bundle boil-off, and designed and built a novel experimental rig to take high-fidelity measurements.
Fuel Channel Flow modelling
Fuel assemblies facilitate the transport of thermal energy away from the fuel rods and into the primary coolant loop. Accurate simulation of the flow and turbulence within the fuel channels is essential to provide confidence in the heat transfer predictions.
The University of Manchester assessed current Reynolds-averaged Navier-Stokes (RANS) turbulence models in the simulation of flows through pressurized water reactor (PWR) fuel cooling passages. This was based on a single-phase turbulent flow test case of a square pitched array of cylindrical rods.
Single-Phase Natural Convection
Passive cooling systems are a key component of many advanced reactor designs, and so modelling natural circulation loops with confidence is an important requirement.
The University of Manchester conducted an initial investigation and study using detailed CFD modelling into the stable and unstable transient behaviour within natural circulation loops.
Phase 1 identified what thermal hydraulic facilities and modelling capability is required by the end users/developers to improve the efficiency and reliability of nuclear power plants now and in the future.