Silicon Carbide-Based Power Electronics for Small Fission Reactors

Fission power systems (FPS) are a candidate power source for long duration NASA surface missions to the Moon and Mars, and offer significant advantages over competing options, including longer life, operational robustness, and mission flexibility. Electronics associated with the power conversion and power management and distribution (PMAD) systems in FPS have to operate reliably under high temperature (100s of deg C), high power (1-10 kWe), and severe radiation. Silicon carbide (SiC) is a promising solution with superior electronic properties for power applications. SiC devices offer higher temperature operation, higher breakdown voltages, and higher power conversion efficiency than silicon devices. However, vulnerability to heavy-ion induced failure and uncertainty in response to nuclear radiation are challenges facing FPS applications of SiC technology. CFDRC, Vanderbilt University, and Wolfspeed propose a modeling and experiment-based approach using commercial SiC technology to address this challenge. In Phase I, we applied the MRED radiation transport code to determine neutron-induced secondary ion spectra, developed a physics-based model of the selected SiC MOSFET using CFDRCrsquo;s NanoTCAD software, and performed simulations to investigate sensitivity to design parameters, ion characteristics, and applied bias. In Phase II, we will transition to a higher-voltage SiC MOSFET technology for greater relevance to FPS applications, and characterize electrical and radiation performance via experiments. We will use the MRED toolkit for higher fidelity calculations of secondary particles and compare the impact of heavy ions (background environment) and fission neutrons. We will adapt the existing TCAD model, perform detailed simulations to understand key underlying mechanisms, and parametrically analyze design features to identify guidelines for higher radiation tolerance. Promising solutions will be prototyped, tested, and delivered to NASA.