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

Training and IRUG Seminar Postponed

Because of the rapid worldwide spread of the COVID-19 virus we are indefinitely postponing the 2020 International RELAP5 Users Group Meeting and Training Seminar. These activities were scheduled to start on April 27, 2020. We will make information available about new dates as it becomes available.

If you have already paid your registration fee, your fee will be refunded.

The postponement was done out of an abundance of caution and we apologize for any inconvenience this has caused.

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-