 For a while, the calutrons suffered from a series of debilitating breakdowns and equipment failures, exacerbated by a shortage of spare parts. Hopes that the Alpha II racetracks would be more reliable soon faded, as they were plagued by insulator failures. These problems were gradually overcome. The first shipments of enriched uranium to the Manhattan Project's Los Alamos Laboratory were made in March 1944, consisting of Alpha product enriched to 13 to 15 percent uranium-235. While of no use in a bomb, it was urgently required for experiments with enriched uranium. The last shipment of Alpha product was on made 11 May 1944. On 7 June 1944, Y-12 made its first delivery of weapons-grade Beta product, enriched to as high as 89 % uranium-235.
