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physics problem

chickcharnley · 2013-03-27 18:31:22

Q. In a fission reactor the fission of one atom U-235 results in the release of 200MeV of energy, 40% of which ultimately appears as energy as electrical energy. (a) calculate the number of uranium atoms undergoing fission per second for each kilowatt of electrical power output and (b) the total mass of U-235 used in one…

27-03-2013 7:31pm

#1

chickcharnley

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Q. In a fission reactor the fission of one atom U-235 results in the release of 200MeV of energy, 40% of which ultimately appears as energy as electrical energy.
(a) calculate the number of uranium atoms undergoing fission per second for each kilowatt of electrical power output and
(b) the total mass of U-235 used in one hour if the total power output of the reactor is 100MW
Ive solved a which i got 7.81 x 1013 fissions per second but im stuck on b?

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#2 27-03-2013 10:01pm

Chikablam

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100MW=100x106 Watts= 100x106 J/s
One U-235 atom yields 40% of 200MeV, which is simply 80MeV, or 80(106)(1.6x10-19) Joules per atom.
So that works out at 1.28x10-12 J per atom.
Therefore, (100x106) / (1.28x10-12 atoms are used per second.
So multiply that out to get how many are used in one hour, and then simply multiply by the mass of a single atom

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