Idaho National Laboratory’s RELAP5-3D is a robust modeling and simulation software designed to predict the intricate behavior of nuclear reactor systems. Originally developed in 1979, it has evolved beyond studying Light Water Reactors to successfully model the thermal and fluid performance of high-temperature gas-cooled reactors, super-critical CO2 reactors, sodium fast reactors, and molten salt reactors.

Accredited by international benchmarks and design bases analyses accepted by the Nuclear Regulatory Commission for reactor licensing, RELAP5-3D is recognized as the premier system analysis code. It is often the standard by which other system codes are measured.  RELAP5-3D has an extensive experiment database that validates the software’s modeling, offering confidence in predicting thermal and fluid performance.

With the ability to integrate into an analyst’s toolset, these codes provide a quick analysis of a system. When coupled with computational fluid dynamics (CFD) codes, such as openFOAM and STARCCM+, RELAP5-3D allows for comprehensive modeling.

RELAP5-3D is widely used for reactor safety analysis, design, operator training, and non-nuclear modeling and simulation.  The software is a Department of Energy 10 CFR 810 code, which means that RELAP5-3D is solely distributed through the INL Technology Deployment Office, which requires a license agreement, export control review, and approved use by the INL Code Oversight Group.