# Calculating the mass of consumed Uranium 235

1. Apr 24, 2010

### speedrsr

1. The problem statement, all variables and given/known data

A typical nuclear fission power plant produces
about 3.36 GW of electrical power. Assume
that the plant has an overall efficiency of
44.6% and that each fission event produces
250 MeV of thermal energy.
Calculate the mass of 235U consumed each
day.

2. Relevant equations

3. The attempt at a solution

Okay, so first I converted the 3.36 GW in 3.36E^9 W and divded that by .446 To get the Etotal.
Multiply that times 1.6E^-13 to get MeV of 1.205E^-3.
Divide the MeV/# of reactions by 250 MeV to get 4.821E^-6 reactions per second.
Multiplied 4.821E^-6 * the mass of U235 which is 235.043925 and 1.66E^-27 to get 1.881228E^-30 kg consumed every second.

1.881228E^-30 (60)(60)(24) should give kg/ d, but for some reason It's not coming out as a correct answer. I get 1.62538E^-25 kg/day

Can anyone find a mistake in my work?

2. Apr 24, 2010

### nickjer

Well I made it as far as your conversion from Watts=J/s to MeV/s. Why did you multiply it by 1.6E-13?

1 Joule = 6.24E12 MeV

So you should multiply it by 6.24E12.