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**1. Homework Statement**

Given that the average fission produces 200 MeV in energy, and that nuclear plants have an efficiency of 33%, how many fissions take place each second in a plant producing 1000 MW of electricity? How much uranium-235 is being used per day?

**3. The Attempt at a Solution**

I've solved the first part: 200 MeV of energy = 3.2 x 10^-11 watt-seconds. From this, 3.1 x 10^10 fissions per second produce 1 W of thermal power. For 330 MW, that equals 1.029 x 10^19 fissions per second.

...But I don't know how to go about finding how much uranium-235 is used per day. I know that U-235 only makes up 4% of a typical LWR, but I'm in the dark as to how much U-235 each fission would consume... Maybe I'm just having an off-day, and the answer's extremely easy... :uhh: