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Calculating the mass of consumed Uranium 235

  1. Apr 24, 2010 #1
    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
    Answer in units of kg/d.

    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. jcsd
  3. Apr 24, 2010 #2
    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.
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