Steady State Supercritical Carbon Dioxide Recompression Closed Brayton Cycle Operating Point Comparison With Predictions

The U.S. Department of Energy Office of Nuclear Energy (DOE-NE) supercritical carbon dioxide recompression closed Brayton cycle (RCBC) test assembly (TA) construction has been completed to its original design and resides at Sandia National Laboratories, New Mexico. Commissioning tests were completed in July 2012, followed by a number of tests in both the recompression CBC configuration, and in a bottoming cycle configuration that is proprietary to a current customer. While the test assembly has been developed and installed to support testing, a computer model of the loop, written in Fortran programming language, has also been developed. The purpose of this iterative model is to facilitate data interpretation, guide test assembly design modifications, develop control schemes, and serve as a foundation from which to develop a transient model. Of central utility is its modular nature, which has already been leveraged to develop a customer’s bottoming cycle configuration. Verification that the model uses appropriate physical representations of components and processes, is performing as intended, and validation that the model accurately reproduces test data, are necessary activities. Completion of the model’s verification and validation (V&V) supports the long-term goal of commercializing the RCBC for a sodium fast reactor. This paper presents verification results of certain subprocesses of the iterative computer model. Verification of these subprocesses was completed with positive results. While an adequate range of data for complete and thorough validation do not yet exist, comparison of subprocess predictions with data from a single, representative operating point are presented as are explanations for differences. Recommendations for activities necessary to complete subprocess and model validation are given. The RCBC iterative computer model V&V process should be revisited following completion of these recommended actions and the generation of steady state data while operating near the test assembly design point.