The United States uses 1.12×1019J of electrical energy per year. Assume, that all this energy came from the fission of 235U, which releases 200MeV per fission event.
How many kilograms of 235U would be used per year?
How many kilograms of uranium would have to be mined per year to provide that much 235U? (Recall that only 0.700% of naturally occurring uranium is 235U.)