6, 1954. President Eisenhower remotely initiated the first scoop of dirt at the ceremony. The reactor achieved first criticality at 4:30 AM on December 2, 1957. Sixteen days later, on December 18, the first electrical power was generated and full power was achieved on December 23, 1957, although the station remained in test mode. Eisenhower opened the Shippingport Atomic Power Station on May 26, 1958. The plant was built in 32 months at a cost of $72.5 million. The type of reactor used at Shippingport was a matter of expediency. The Atomic Energy Commission urged the construction of a reactor integrated into the utility grid. The only suitable reactor available at the time was the one that was intended for the nuclear-powered aircraft carrier desired by the Navy, but which Eisenhower had just vetoed. Kenneth Nichols of the AEC said it "became obvious" that the Rickover-Westinghouse pressurised-water reactor intended for an aircraft carrier was "the best choice for a reactor to demonstrate the production of electricity" with Rickover "having a going organization and a reactor project under way that now had no specific use to justify it". This was accepted by Lewis Strauss and the Commission in January 1954. The acceptance of Duquesne Light as the utility partner was announced on 11 March. The ground-breaking ceremony was initiated by Eisenhower from Denver where he was giving a talk on atomic energy on Labor Day; Rickover ensured that the unmanned bulldozer pushing dirt did not dig in and stall by having the dozer blade riding along two railroad rails buried under six inches of dirt. The origin of the project explains why the Shippingport reactor used 93%-enriched uranium, unlike later commercial power reactors that do not exceed 5% enrichment. Other significant differences from commercial reactors include the use of hafnium for its control rods, although these were necessary and used only in the reactor's seed. Shippingport was created and operated under the auspices of Admiral Hyman G. Rickover, whose authority included a substantial role within the United States Atomic Energy Commission (AEC). Cores The Shippingport reactor was designed to accommodate different cores during its lifetime; three were used. The first, installed in 1957, held 14.2 tons of natural uranium (the "blanket") and of high-enriched (93% U-235) uranium (the "seed"); despite this disparity in mass, about half the power was generated in the seed. The seed was depleted quicker than the blanket,