The Manhattan Project: Making the Atomic Bomb
Part IV: The Manhattan Engineer District in Operation
With the abandonment of the plutonium gun bomb in July 1944, planning at Hanford became more complicated. Pile 100-B was almost complete, as was the first chemical separation plant, while pile D was at the halfway point. Pile F was not yet under construction. If implosion devices using plutonium could be developed at Los Alamos, the three piles would probably produce enough plutonium for the weapons required, but as yet no one was sure of the amount needed.