NUCLEAR FUEL PELLET

摘要

A uranium oxide fuel pellet (10) comprises an inner region (14) and an outer region (12) about the inner region, the uranium oxide of at least a portion of said outer region being rich in niobia relative to the inner region. It has been found that the large grain size of the outer region promoted by the niobia addition actually has a greater creep rate than a small grain size material, therby reducing strain (pellet cladding interaction), and that a larger grain size for the inner region is preferably produced by means other than a niobia addition, which latter may increase the rate of gas diffusion within the grain structure and so provide lower fission gas retention. A process for making the pellet is described.