Preliminary study of sintering zero-rupture Fully Ceramic Microencapsulated (FCM) fuel

The demonstration of industrially feasible zero-rupture Fully Ceramic Microencapsulated (FCM) fuels has been achieved via layers of fuel particles vertically stacked and consolidated by Pulsed Electric Current Sintering. Uniaxial shrinkage, a key component of fuel arrangement, was analyzed via SEM, XRD and computational analyses, using cylindrical geometries from 0.25 to 1.5 “height-to-diameter” (h/d) aspect ratio. Bulk densities of ~3.1 g/cc were achieved on pellets at h/d ~0.25, using a ramp rate of 100°C per min to 1825°C and holding for 10 minutes with 10 MPa applied pressure. Using the same parameters, this value reduced to ~2.8 g/cc at h/d ~1.5. More extensive percolation of oxide sintering additives and earlier closure of interconnected pores in extreme ends of the pellet was attributed to higher temperatures in those regions. The top and bottom of the pellet densify before the center, also resulting reduced displacement between the fuel layers in these regions. Parametric studies of sintering with different temperature and time, with support of computational analyses, was used to map expected temperature distribution and sintering behavior. These tools will be used for further optimization of FCM fuel fabrication.