RELAP5-3D Robustness Improvements and Supporting Software for Real-Time and SAE Models Creation Under 3KEYMASTER TM Platform

This paper summarizes achievements in the development of advanced technology utilizing RELAP5-3D for both real-time training simulators and highly detailed simulation-assisted engineering models for different reactor types, including small modular and liquid metal–cooled reactors. Code improvements were made to address major challenges in real-time nuclear power plant simulators to enable high performance, stability, and accuracy concurrently. The code changes, which were accumulated over 3 decades of code applications, include implementation of a smooth transition between different heat transfer and flow regime conditions, Dalton-Gibbs mixture equation solver corrections, and numerical scheme improvements to avoid code aborts and unphysical spikes when transitioning from one-phase to two-phase flow conditions and vice versa.To support training simulator functions, dynamic change of fouling factors, form loss coefficients, and material heat capacity values were implemented. The model development studio is supported by the functionality of interactive changes to Time-Dependent component parameters and constant-type control variable values. The graphical editor has been added to the framework with rich visualization capabilities, multidimensional components, a XML-based user input deck editor with thermodynamic value validation, and version control functionality.The performance improvements were achieved by means of parallelization techniques when a neutronics code (typically NESTLE) and separate hydraulic systems are running on different computer processors, with the results exchanging functionality support every time advancement step. Engineering simulators are supported by the addition of turbulent mixing code capability in the lateral direction between adjacent reactor core channels. The limitation of a three-digit component number gas been relaxed to enable greater flexibility in deck composition.Supporting software functionality has been added to the 3KEYMASTERTM platform for multidimensional flow simulations and user input deck generation, which uses the outstanding utility of cross-sectional area calculations between the reactor plenum’s cylindrical planar noding and the reactor core cartesian structure utilizing the Greiner-Hormann algorithm. Proposed further code enhancements for multidimensional simulations include the addition of an uneven mesh feature for the cylindrical coordinate system in the planar direction and enabling seamless integration of multidimensional heat structures with hydrodynamic components.