The Goertzel theorem states that this quantity is minimized for a flat assembly thermal flux, and it is invariant under conjugation, so the adjoint transport equations must yield the same value as the forward ones. It is calculable to 0th order by setting the engineering factor kEFF ["k-effective"] in the single group steady-state neutron diffusion equation to unity, and a general integral equation for it can be found by volume integrating the fuel macroscopic absorption cross-section over the core. It is sensitively dependent on the prompt neutron spectrum, which is why those data are highly 
The Goertzel theorem states that this quantity is minimized for a flat assembly thermal flux, and it is invariant under conjugation, so the adjoint transport equations must yield the same value as the forward ones. It is calculable to 0th order by setting the engineering factor kEFF ["k-effective"] in the single group steady-state neutron diffusion equation to unity, and a general integral equation for it can be found by volume integrating the fuel macroscopic absorption cross-section over the core. It is sensitively dependent on the prompt neutron spectrum, which is why those data are highly classified. For ten points, name this important quantity for a fission system, equal to about 50 kg for a bare sphere of U235; the amount of fuel needed to achieve a self-sustaining chain reaction.
The Goertzel theorem states that this quantity is minimized for a flat assembly thermal flux, and it is invariant under conjugation, so the adjoint transport equations must yield the same value as the forward ones.
{critical mass}