THORS Benchmark

The Thermal-Hydraulic Out-of-Reactor Safety (THORS) is a large high-temperature sodium facility operated at Oak Ridge National Laboratory (ORNL) in the United States. A number of bundles simulating sodium-cooled fast reactor (SFR) cores were tested there. The measurements consist mostly of transient temperature fields in the wires and on the pin surfaces. Measurements of different pin/wires temperatures at several axial locations allow for reconstruction of the 3D temperature flow field. Pressure drop measurements over the entire test section, flow rates, and acoustic signals for boiling detection were also conducted.The benchmark was also part of the Expert Group on Reactor Core Thermal-Hydraulics and Mechanics (EGTHM) activities. 

  1. provide a sodium turbulent flow and heat transfer database for high-resolution [computational fluid dynamics (CFD) and subchannel] model validation
  2. emphasise the importance of uncertainty analysis for thermal-hydraulic simulations for a variety of reasons
  3. establish best practices for quantification of geometry modelling, input data, fluid properties, and other uncertainties associated with the complex flows in wire-wrapped pin arrays of SFR
  4. develop guidance for CFD model/code validation for SFR fuel bundles that can be used to improve the existing standards
  5. update the current generation thermal-hydraulic (TH) models for pressure drop and inter-channel mixing and develop the hybrid experiment/simulation database necessary to establish and calibrate the low order models with high resolution (both experimental/numerical) data, e.g. Hi2Lo problem

THORS loop

  • a variable speed pump plus control valves allow adjustments to the flow through the test section in the range of 1-227 gpm (1 m3/min)
  • maximum design temperature of sodium is 1200F (650C)
  • the max design pin power is 24.5 kW
  • the facility is designed and equipped with components to handle and operate liquid sodium. Some of them are:
    • a mixing tee to prevent thermal fatigue of the system
    • a sodium excess and storage tank
    • an oxide control
    • all components can be pre-heated during start-up


Ian Hill