The physical and mechanical properties of GCRE-type fuel elements were determined from room temperature to 1650 deg F. The fuel elements were prepared by cladding Type 318 stainless steel sheet to a core containing 15 to 35 wt.% UO/ sub 2/ in either prealloyed Type 318 stainless steel or elemental iron-18 wt.% chromium-14 wt. % nickel-2.5 wt. % molybdenum. The tensile strength in the direction perpendicular to the rolling plane decreased from 24,600 psi at room temperature to 9,200 psi at 1650 deg F for the reference fuel plate, whose core contained 25 wt.% UO2 in the elemental alloy. The tensile strength in the longitudinal direction for this fuel element ranged from 54,800 psi at room temperature to 14,200 psi at 1650 deg F, with elongation in 2 in. ranging from 8 to 13 per cent. The extrapolated stress for 1000hr rupture life at 1650 deg F was 1800 psi, and a 1.4T bend was withstood without cracking. The mean linear thermal coefficient of expansion was 11.0 x 10−6 per deg F for the range 68 to 1700 deg F. (auth).

The superheat section of the Fifth Boiling Reactor Experiment (BORAX-V) is fueled with enriched uranium (93 wt.% U-235) in the form of uranium dioxide in a matrix of stainless steel. Stainless steel-clad plates containing the fuel were fabricated by the Atomics International Division of North American Aviation.