K. Litfin

Sub-Channel Analysis Code: MATRA

The sub-channel analysis code MATRA is descended from COBRA, and was originally developed by Korean Atomic Energy Research Institute (KAERI) for PWRs. In the frame of a bilateral collaboration between the Forschungszentrum Karlsruhe and KAERI, the MATRA code is being further modified for both heavy liquid metal and supercritical water cooled reactors.

Main features

  • Lumped parameter approach
  • Steady-state & transient analysis
  • Capability for single and two-phase flows
  • Applicability to various fluids

Main applications

  • Design of fuel assemblies of LM cooled reactors and water-cooled reactors
  • Safety analysis of nuclear reactor cores
  • Development of advanced nuclear reactor cores


  • Under preparation

Main references

(1) Yoo, Y. J., Hwang, D. H. and Sohn, D. S., “Development of a Subchannal Analysis Code MATRA Applicable to PWRs and ALMRs,” J. of Korean Nuclear Society , Vol. 31, p. 314, 1999.
(2) Wheeler, C. L., et al., “COBRA-IV-i : An Interim Version of COBRA for Thermal-Hydraulic Analysis of Rod Bundle Nuclear Fuel Elements and Cores,” BNWL-1662, 1976.


System Analysis Code: ATHLET-MF

The system analysis code ATHLET-MF, which is developed by the Forschungszentrum Karlsruhe based on the ATHLET code of the Gesellschaft für Reaktorsicherheit (GRS), is applicable to multi-fluids nuclear systems.

Main features:

  • 1-dimensional, incompressible fluids with volumetric heat source
  • Multi-fluid systems with thermal coupling
  • General control simulation modules
  • Option of user specified thermal-physical properties and physical models
  • Separation of physical models from numerical methods

Main applications:

  • Cooling system of spallation targets, e.g. XADS
  • Analysis of MEGAPIE out-of-pile integral tests MITS
  • Design analysis of ADS cooling systems


The ATHLET-MF has been applied to the cooling systems of various spallation targets, such as the target of the European experimental ADS (XADS). Figure 1 shows the transient behavior of LBE mass flow rate and temperature under start-up conditions.

                      Figure 1: Results of a start-up transient

Main references

(1) ATHLET User’s Manual, GRS, September 2001
(2) H.Y. Chen, X. Cheng, H.J. Neitzel, Application of ATHLET Code to Heavy liquid Metal Cooled Systems, Annual Meeting on Nucl. Tech. 2004, Dusseldorf, Germany, May 25-27, 2004