Neutron spectrum kinetics in the infinite homogeneous reactor

An analysis of the behaviour of the neutron spectrum in transient condition, based on an extension of the inhour equation to the energy dimension, is presented. This approach enables to describe the spectrum evolution in time as a combination of eigenstates associated to the roots of the inhour equation. The fine description of the neutron distribution in energy during the transient is exploited to evaluate homogenization errors committed by few-energy-group models.