Calculating amount of fissionable material needed for reactor

[leviathanX777]

Homework Statement

A fission reactor produces 300 MW of electrical power with an efficiency of 30%. Calculate the mass of 235U consumed by the reactor in one day.

Homework Equations

Power = Energy/Time

E=mc^2

The Attempt at a Solution

Using the above equations I got an energy of 1.62 x 10^23 MeV. The corresponding mass found using the fact that 1 amu = 1.66 X 10^-27 Kg was 0.250 Kg. Is this right? I don't see how to bring the efficiency of 30% into this. Is it basically 30% of the energy that I calculated?

 

[leviathanX777]

Ah wait, I realized that I needed to add another 70% onto the 300 MW which gave me 1,000 MW. However the answer I got was 834.98 Kg, seems pretty high to be correct. Am I doing something wrong?