Abstract
Adoption of SiC-matrix fuel elements in future pin-in-block type HTGR designs will enhance oxidation resistance of the fuel element in the event of the air ingress accident, one of the most worrisome accidents in HTGRs. This would eliminate the need for the graphite sleeves used in the current pin-in-block type HTGR designs and enable high power density core designs with sleeveless and directly coolable fuel structure. Such a concept itself has been suggested in the past. However, feasibility for a core design with the SiC-matrix fuel elements has not evaluated yet. The present work is intended to demonstrate the feasibility for a new core design upgraded from an existing conceptual core design, called HTR50S, with 50 MW thermal power and reactor outlet temperature of 750 °C. The new core design uses SiC-matrix fuel elements and increases the reactor power density to 1.2 times higher than the original HTR50S design. The calculation results showed that the new core design satisfied these target values on the reactor shutdown margin, the temperature coefficient of reactivity, and the maximum fuel temperature during normal operation.
