RELAP5-3D is the latest in the RELAP5 code series developed at Idaho National Laboratory (INL) for the analysis of transients and accidents in water–cooled nuclear power plants and related systems as well as the analysis of advanced reactor designs.

The RELAP5–3D code is an outgrowth of the one-dimensional RELAP5/MOD3 code developed at INL.  The most prominent attribute that distinguishes RELAP5–3D from its predecessors is the fully integrated, multi-dimensional thermal-hydraulic and kinetic modeling capability.

RELAP5–3D is available from INL through membership in the International RELAP5 Users Group (IRUG).

The code is currently configured to run on both Linux and Windows. Operating systems and compilers supported are:

  • O/S

    • Linux: OpenSUSE: 42.2 (x86_64)

    • Windows: Windows 7, SP1

  • Intel compiler designation

    • On Linux: Version 16.0.4

    • On Windows: Composer XE 2013, SP1, Update 2

RELAP5–3D News

RELAP5-3D Training and IRUG Seminar

The RELAP5-3D training and International RELAP5-3D Users Group (IRUG) seminar will be held September 13-17, 2021. For more information about these events please see:

If you have questions or concerns please contact:

Theron Marshall



Brenda Monson


RELAP5-3D Version 4.4.2 is now available for Windows 10

A RELAP5-3D version 4.4.2 executable has been built on the Windows 10 platform and is available upon request.

RELAP5-3D Windows 7 development has concluded

Future versions of RELAP5-3D will be developed on the Windows 10 platform and further development on the Windows 7 platform will no longer be pursued.

RELAP5-3D Version 4.4.2 released.

The latest version has been developed and released, it is available upon request.

Code Version 
The most recent RELAP5-3D release is Version 4.4.2.

For information on how to obtain the code, please contact Morgan Goody at:

Morgan Goody
Technology Transfer and Licensing Specialist
Idaho National Laboratory
PO Box 1625
Idaho Falls, ID 83415
Phone: (208) 526-