4. Multi-group theory

4.1 Principle of multigroup theory

To deal with neutron spectrum problems induced by slowing-down and thermalization processes, we are led, in practice, to discretize the variable E (neutron energy) or the equivalent variables v or u. This discretization is the multigroup method: the range covered by the spectrum from E ₀ (maximum neutron energy, around 10 MeV) to E _N (minimum energy, practically zero) is divided into N intervals by intermediate bounds E _...