A description is given of the coextrusion of aluminum-canned U3O8- aluminum powder mixtures to produce dispersion type fuel elements. The effects of powder preparation, extrusion billet can composition, extrusion ratio, extrusion temperatures, and tri-uranium octi-oxide (U3O8) content of the powder mixture are illustrated. Use of density measurements of individual elements to determine their uranium-235 content is described.
The process entails the hot extrusion of a powder mixture of U3O8 and aluminum, contained in an aluminum can, into a long aluminum-clad shape from which individual fuel elements are sheared. The fuel elements are of near theoretical density, integrally clad, and exhibit a uniform dispersion of fissionable material in the matrix. Core compositions from less than 10 to as high as 51 per cent by weight of U3O8 have been shown to be feasible. A high conversion yield from billet to elements is regularly achieved. Reproducibility of the process is excellent; variation in the uranium-235 content of fuel elements from identically charged billets is almost negligible. The process has been used to produce the fuel loadings for the Argonaut Mark I Training Reactor (May 1956) and for the Argonaut G Reactor displayed at the 1958 Geneva Conference.