Pellet Fabrication Development of Annular Pellets for Internally Cooled Annular Fuel

Abstract

Internally cooled annular fuel (ICAF) uses annular pellets clad both externally and internally so that coolant can flow through the annulus as well as around the outside of the element. In order to maximize the heat transfer to the coolant flowing through the annulus, the gap between the inside diameter of the pellet and the inner cladding must be minimized. Annular pellets are a variant of the standard solid cylindrical pellet, the difference being the presence of a void along the cylindrical axis. Fabricating pellets with this geometry is not uncommon and methods are well established. However, challenges arise when fabricating pellets with high tolerances on the internal diameter. This paper describes fabrication development efforts towards producing annular pellets with highly precise and accurate inside diameters in order to minimize the pellet-inner cladding gap for internally cooled annular fuel.