Complex sentence: Calutrons were used in the industrial scale uranium enrichment at the Y-12 plant at the Clinton Engineer Works in Oak Ridge, Tennessee that produced the uranium-235 used in the Little Boy atomic bomb that was detonated over Hiroshima on 6 August 1945.
Split into simpler sentences: Calutrons were used in the industrial-scale Y-12 uranium enrichment plant at the Clinton Engineer Works in Oak Ridge, Tennessee. The uranium-235 produced there was used in the Little Boy atomic bomb that was detonated over Hiroshima on 6 August 1945.