Final answer:
During World War II, 10% of the US's power was used to enrich uranium isotopes to manufacture the atomic bomb as part of the Manhattan Project.
Step-by-step explanation:
The United States diverted 10% of its power during World War II to purify uranium isotopes because most of this power was used for the separation of U-235 from U-238, a key process in the manufacturing of nuclear weapons. This effort was part of the Manhattan Project, which succeeded in producing the world's first atomic bombs. The enrichment process at Oak Ridge, Tennessee, was critical to creating enough fissionable material for the bomb that was eventually dropped on Hiroshima, codenamed 'Little Boy'.