1. The problem statement, all variables and given/known data If 57.5% of the fission neutrons escape from a bare sphere of 235 Uranium, what is the multiplication factor of the sphere?. In this system, the average value of nu being 2.31. 2. Relevant equations nu= number of neutrons emitted per absorption in the fuel 3. The attempt at a solution Very basic problem, yet wanted to check my answer and understanding of it. Since 57.5% of the fission neutrons escape, that means 42.5% of the fission neutrons are being used. So for every 1 fission neutron used 2.31 fission neutrons are being emitted. So the multiplication factor for the system would be .425(2.31)= 0.982, thus stating the reactor is subcritical, since the multiplication factor is less than 1.