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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

The next Training and International RELAP5-3D Users Group seminar will be April 15 - 19, 2019. 

More information on registration for the seminar and training can be found on the IRUG Seminar page.

RELAP5-3D Version 4.4.2 released.

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

Fee Increase

IRUG membership fees increase on June 1, 2018 for all renewals and new license agreements.

The modified fees are listed below:


​Domestic Users
​International Users
​Full Membership Regular
​Full Membership Super User
​Multi User Participant
​Single User Participant

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

For information on how to obtain the code, please contact Mr. Arthur Baker at:

Mr. Arthur Baker
Sr. Commercialization Manager
Idaho National Laboratory
PO Box 1625
Idaho Falls, ID 83415
Phone: (208) 526-1872