Contract

RELAP5-3D 4.x: Thermal-Hydraulic Nuclear Reactor Analysis, Licensing Opportunity

Agency: ENERGY, DEPARTMENT OF / ENERGY, DEPARTMENT OF
Location: Idaho Falls, ID
Amount: Amount not listed
Deadline: Closes in 106 days (Nov 1, 2026)
Posted: Apr 20, 2026
Set-aside: None (open competition)
NAICS code: 541690

What this contract is for

Technology Summary: RELAP5-3D is a fully integrated system-level modeling code for simulating the behavior of nuclear power plants and other complex thermal-fluid systems. Originally developed for light water reactor safety analysis, RELAP5-3D supports detailed modeling of multiphase flow, heat transfer, reactor kinetics, and fluid-structure interactions. It is capable of performing both steady-state and transient analyses in one-, two-, or three-dimensional geometries, making it one of the most versatile nuclear systems analysis tools in use today. Problem Addressed: Designers, operators, and regulators of nuclear systems need validated tools to simulate a wide range of operating and accident scenarios, from routine transients to complex multi-physics events. Many commercial codes lack the physics detail or numerical flexibility needed to capture the behavior of advanced reactor designs, high-fidelity safety cases, or coupled systems involving multiple working fluids or complex geometries. Proposed Solution: RELAP5-3D enables high-fidelity simulations of nuclear thermal-hydraulics and safety behavior. Key capabilities include: Modeling of single- and two-phase flow using a two-fluid model Support for multiple fluids, flow regimes, and non-condensable gases Built-in reactor kinetics and neutron transport models (point kinetics or 3D neutron kinetics) Fully coupled heat structures and control system modeling Parallel processing and restart capabilities for large, complex runs Optional coupling with external tools for fuel performance, CFD, or systems-level co-simulation RELAP5-3D is actively maintained and enhanced to support modern reactor designs, including small modular reactors, high-temperature gas-cooled reactors, and liquid metal-cooled reactors. Key Advantages: C...

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