Summary of improvements in modeling for fidelity and performance in MAMBA during FY18
This milestone report summarizes the FMC work on improvements to the MAMBA modeling methodology. The work was performed in close collaboration with the PHI as well as THM focus area and it was undertaken to improve both the physical fidelity and computational performance of MAMBA. We first describe the path towards identifying and then resolving issues in the MAMBA code and the underlying physics models that were still remaining at the beginning of FY18, after the code re-write in the previous year. These were primarily related to boiling and species transport, especially boron, within the CRUD. The code problems originated in the MAMBA3D code, from which the development of the new re-written code started, but they were only identified during testing of the new MAMBA code. We purposefully discuss a number of alternative explanations and solutions to the main issue identified, since the two-phase character of fluid transport in the CRUD and the related mass transport are still sources of model uncertainty that we continue to investigate. The hands-on code development referenced in this report was done under PHI and this milestone mainly provided support in the form of analysis, literature review, code review and feedback to the code developers.