Nuclear Reactor as Stiff System

The quasisimptotic method of numerical integration of the equations of slow evolution neutron fields is described. It is based on the use of main group of eigenfunctions, which is produced by splitting of the spectrum when delayed neutrons are taken into account. The numerical results are described and analysed. The test problem by V.I.Lebedev is used. The numerical method of solving of generalized main eigenvalue problem is described.