RELAP5 Capability to Predict Pressure Wave Propagation Phenomena in Single- and Two-Phase Flow Conditions

  • Lukasz Sokolowski Inspecta Nuclear AB
  • Zbigniew Koszela Ph.D.


Correct evaluation of the hydrodynamic loads induced by large and rapid pressure waves propagating with the speed of sound along the reactor piping systems and Reactor Pressure Vessel (RPV) is an important and difficult issue of nuclear power plant safety. The pressure shock transients and resulting hydrodynamic loads on the pipes and RPV structures are commonly calculated with one-dimensional thermo-hydraulic system codes such as RELAP5, TRACE, DRAKO and ROLAST. In Sweden, the most widely used computer code for this purpose is RELAP5. This code needs, therefore, to be assessed for its capability to predict pressure wave behavior. The conducted assessment involves simulations of single- and two-phase shock-tube problems and two-phase blowdown as well as water hammer experiments. The performed numerical experiments clearly show that RELAP5, with the proper time step and spatial mesh size, is capable of predicting the complex dynamics of single- and two-phase pressure wave phenomena with good to reasonable accuracy.

Author Biographies

Lukasz Sokolowski, Inspecta Nuclear AB
Lukasz Sokolowski works as a thermal-hydraulics specialist in Inspecta Nuclear AB, Stockholm, Sweden, the accredited company responsible for the inspection of nuclear facilities and equipment. He was awarded in B.Sc. in Power Engineering and M.Sc. in Nuclear Engineering from the Warsaw University of Technology in Warsaw, Poland, and the Royal University of Technology in Stockholm, Sweden. His area of professional interest is numerical methods in nuclear engineering, 1D thermal-hydraulics systems codes and CFD solutions for water hammer and multiphase flow regimes.
Zbigniew Koszela, Ph.D.
Zbigniew Koszela (M.Sc., mechanical engineering, 1978, and Ph.D., applied mathematics, 1984, Warsaw University of Technology, Poland) was a research and development engineer with ABB Atom AB. He was also a researcher in the Department of Nuclear Power Safety of Royal Institute of Technology, Stockholm, Sweden. Currently works at the position of design reviewer in Inspecta Nuclear AB, Stockholm, Sweden. His background includes boiling water reactor and pressurized water reactor fuel, core design, licensing, thermal-hydraulics and transient analysis.
How to Cite
SOKOLOWSKI, Lukasz; KOSZELA, Zbigniew. RELAP5 Capability to Predict Pressure Wave Propagation Phenomena in Single- and Two-Phase Flow Conditions. Journal of Power Technologies, [S.l.], v. 92, n. 3, p. 150--165, oct. 2012. ISSN 2083-4195. Available at: <>. Date accessed: 28 june 2022.
Nuclear Fuels and Reactor Safety


pressure waves, shock-tube, two-phase flow, water hammer, RELAP5

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