TRACE: Modifications in Support of Supercritical CO2 Transient Modeling

by Brett Siebert, Michael Hexemer, Jared Dolatowski, & Greg Wahl
Knolls Atomic Power Laboratory

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TRACE is a transient analysis code developed by the U.S. Nuclear Regulatory Commission. TRACE builds on previous generation codes (TRAC-P, TRAC-B, and RELAP5) to enable the analyses of fluid systems. The presentation focuses on changes that have been made to TRACE to enable the code to simulate the behavior of a closed loop S-CO2 Brayton system. The most basic modification is the addition of CO2 as a working fluid. However, the majority of the modifications focus on modeling the behavior of the supercritical turbine and compressor (at design and offdesign conditions). Turbomachinery vendor performance maps have been incorporated into the code. Heat transfer model modifications provide the user the flexibility of dealing with the various heat exchanger types that may appear in an S-CO2 system. Finally, utilizing additions that have been made to TRACE’s “control system”, the user is given the ability to monitor a wide range of turbomachinery input and output parameters – providing insight into how these key components contribute to the overall behavior and transient response of the closed loop.