A nuclear reactor uses 1 kg of uranium enriched to $$1\%$$ in one hour. Assuming $$60\%$$ efficiency find the electrical power generated. Assume each fission of uranium nucleus produces 200 MeV of energy and 238 g of Uranium contains $$6.0 \times 10^{23}$$ atoms. What fraction of mass has disappeared in the process?

PLACEHOLDER ANSWER - the question has two answers. The fissile part is 10 g, i.e. $$\frac{10}{238} \times 6 \times 10^{23} \approx 2.52 \times 10^{22}$$ nuclei, releasing $$2.52 \times 10^{22} \times 3.2 \times 10^{-11} \approx 8.07 \times 10^{11}\text{ J}$$ in an hour. That is $$2.24 \times 10^8\text{ W}$$, and at $$60\%$$ efficiency the electrical power is about $$1.34 \times 10^8\text{ W}$$, i.e. 134 MW. The mass lost is $$\frac{8.07 \times 10^{11}}{9 \times 10^{16}} \approx 9 \times 10^{-6}\text{ kg}$$, about $$9 \times 10^{-6}$$ of the 1 kg of uranium (or $$9 \times 10^{-4}$$ of the 10 g that undergoes fission).