A logical approach for zero-rupture Fully Ceramic Microencapsulated (FCM) fuels via pressure-assisted sintering route

Abstract A pathway to Fully Ceramic Microencapsulated (FCM™) fuel pellets showing absence of sintering-derived fuel “rupture” has been demonstrated. In the typical FCM manufacturing process, TRistructral ISOtropic (TRISO) particles display statistically significant rupture events. Rupture is caused by contact of particles during the axial shrinkage of fuel pellet that accompanies the pressure-assisted sintering process. To solve this, template SiC powder discs were fabricated to host planes of TRISO particles, and the disks are stacked to form a cylindrical “green” pellet. After sintering, it showed that up to ∼34% packing fraction of particles (Vp) is feasible without contact between planes. Sintering was shown to reduce the axial displacement between planes of TRISO, and XCT showed planes separated by a displacement of ∼100 μm. XCT, optical microscopy and SEM showed the very limited radial displacement of particles. However, the relative density of the FCM pellet was limited to ∼95%. The current results support this zero-rupture concept as viable, but perturbations to TRISO arrangements and limited matrix density require further effort, in order to improve FCM fuel performance.