Thermal Hydraulics Open-access Research (THOR) Facility

The assembled THOR facility prior to the construction of the upper access gantry.

THOR Facility Overview

The Reactor Design and Thermal Hydraulics (RDTH) research group of Bangor University’s Nuclear Futures Institute (NFI) has designed and built the Thermal Hydraulics Open-access Research (THOR) Facility. Located on Anglesey’s Menai Science Park (M-Sparc), this facility is a highly modular, light water, thermal hydraulic loop designed to be configurable to support a wide range of industrial and academic projects. While applicable to many sectors, the design intention of the THOR facility is to investigate nuclear thermal hydraulics research relating to the design and operation of pressurised water reactors (PWRs). This will be achieved by exploring pressurised subcooled boiling phenomena under a range of conditions and flow geometries, including; flow obstruction, cross-flow and T-junction flow studies. Moreover, the THOR facility shall be used as an  instrumentation testbed to demonstrate and characterise new multiphase flow imaging techniques – such as novel fibre Bragg grating (FBG) grid sensors. 

In its initial configuration the facility consists of a pressuriser-steam generator, two independently isolatable 4m long (2″ diameter) modular test sections (one vertical and one horizontal), a secondary oil-filled cooling loop and a suite of temperature, pressure and flow characterisation instruments.

Following the commissioning and preliminary experimentation by the RDTH research group, the THOR facility will become accessible to academic or industrial organisations interested in using or adapting the facility for their thermal hydraulics research. If you or your organisation is interested in utilising the THOR facility, or would like to know more, please do not hesitate to contact us. 

Introduction to Nuclear Thermal Hydraulics 

Nuclear thermal hydraulics (NTH) is the study of the fluid dynamics and energy transfer (separate and with coupled neutronic phenomena) within a nuclear system. Put more plainly, it is the study of the behaviour of fluids in nuclear reactors. Whilst NTH encompasses the study of all coolants used in reactors, the most common types of reactors currently operated across the globe today are both cooled and moderated by light water. Therefore, understanding the behaviour of light water, specifically its boiling and flow regimes, as well as how these regimes affect a reactor’s power profile, fuel utilisation and safety margins, is essential to the design of safe and more efficient nuclear power stations. Thus, NTH research endeavours to conduct experiments and simulations to better understand these fluid phenomena, with the THOR facility being well situated to support these academically and industrially relevant research efforts.

Facility Schematics

THOR Main Loop Schematics

Facility Specifications, Equipment & Instrumentation

As the THOR project progresses and is adapted to meet the requirements of future research campaigns, the available equipment and conditions investigable using the facility will continue to expand. However, listed below is a summary of the key properties and equipment of the THOR facility in its current configuration. 

  • Maximum Operating Temperature 200°C
  • Maximum Operating Pressure 40 bar
  • Natural and forced circulation supported
  • 20kW electric immersion heater in each test section
  • 8kW electric immersion heater in main vessel
  • 20% maximum void fraction in test sections  
  • Modular 4m vertical test section
  • Modular 4m horizontal test section
  • Oil cooled secondary heat removal loop.
  • Transparent test sections available 
  • 24 Thermocouples
  • 2 In-vessel Thermistor Thermowells 
  • Phantom VEO 640L high speed camera 
  • Coriolis Mass Flowmeter 
  • 4 Wire Mesh Sensors (32×32 grids)
  • 3 Absolute Pressure Sensors
  • 2 Differential Pressure Sensors 
  • Labview Control Software 
  • Experimental FBG Grid sensors
  • Main pump maximum mass flow rates of 4 kg·s-1

Open Access Research

At the heart of the THOR project is the principle of open-access research, as manifested by the high modularity and reconfigurability of the facility’s design. If you or your organisation is interested in utilising the THOR facility, or would like to know more, please email the RDTH group’s academic leaders:

  • Dr Walter Villanueva:


The THOR project has been supported by 21 industrial, academic and governmental collaborators. With £400k of funding secured for the facility’s development, £350k of which being supplied by a Welsh Government Research Grant.  Listed below are the project’s primary collaborators during the design stage of the THOR facility. 

  • Welsh Government and its Sêr Cymru Programme. 
  • KTH Stockholm, ETH Zürich, Imperial College, University of Liverpool.
  • Vessco Engineering, Westinghouse, Jacobs, Rolls-Royce Submarines,  Rolls-Royce SMR, UKAEA, NNL.
  • UKRI Science and Technology Facilities Council.
  • In discussions: MIT, University of New Brunswick, EDF Energy, STFC Daresbury.

THOR Construction Time Lapse

THOR Construction Gallery


The Reactor Design and Thermal Hydraulics research group would like to  acknowledge the contributions of collaborators to the THOR project. We would, in particular, like to recognise the pivotal contributions of NFI visiting researchers Prof Horst-Michael Prasser of ETH Zurich, Mr Julian Vance-Daniel and Ms. Lucy Morgan of Vessco Engineering and Dr Jean-Marie Le Corre of Westinghouse Electric Sweden. We would like to thank Richard Carroll of DOCAN Corporation as UK Flownex® representatives as well as the central Flownex® team for provision and support of the code. In addition, key technical input was and is received from  KTH Stockholm, MIT and Imperial College, as well as from specialists in Vessco, Rolls-Royce, Jacobs, Westinghouse, the UKAEA, STFC Daresbury, the UK Nuclear Thermal Hydraulics and Paul Scherrer Institute. We are thankful for the continuing support from the Welsh Government, generally and through its Sêr Cymru  programme, the collegial context provided by the UK Nuclear Thermal Hydraulics Special Interest Group, our collaborations via NAMRC, and last but not least, the support from the MSparc organisation and site.