MELCOR Model Development for BlueCRAB and FATE Microreactor Code Comparisons

A MELCOR (Methods of Estimation of Leakages and Consequences of Releases) model for a realistic heat pipe microreactor (rHPMR) was developed as part of an effort to perform code-to-code comparison with BlueCRAB (the federal version of Comprehensive Reactor Analysis Bundle [CRAB]) and FATE (Facility Flow, Aerosol, Thermal, and Explosion). Advanced reactor licensees and the US Nuclear Regulatory Commission are expected to employ these codes for performing safety assessments and quantifying postulated releases, including for microreactors as a part of the license application and review activities. This effort is supported by the US Department of Energy's Microreactor Program with the intent to address knowledge gaps. It also includes developing potential demonstrations or example cases to improve understanding and provide insights for safety assessments. This paper discusses the efforts to assess an rHPMR using MELCOR, where the rHPMR represents Westinghouse's eVinci design. eVinci is a horizontal, prismatic block, heat pipe-cooled, tristructural-isotropic (TRISO)-fueled reactor. Specifically, model development and steady-state results using MELCOR are presented. Limitations with MELCOR's ability to model an rHPMR restricted full assessment of this example case. Limitations included an inability to model both TRISO fuel and heat pipes in combination and to model heat pipes in a horizontal orientation. An alternative approach was explored as a possible effective solution for modeling an rHPMR without explicitly using the heat pipe model. Future efforts will revisit this example with revised models that include realistic fuel, core, and heat pipe components.