AbstractExponential experiments with light-water moderator were conducted to determine criticality standards for the handling of uranium metal enriched to 3 wt % U235. These measurements, made with massive rods 2 and 3 in. in diameter, were combined with Hanford measurements with smaller rods to provide critical bucklings and masses for H20-moderated lattices over a range of rod diameters from less than 0.15 in. to more than 3 in. Subcritical buckling measurements are compared with the more conventional approach-to-critical method.