Influence of the Photoneutrons on the Kinetics of the Beryllium Reflected Core of the Budapest Research Reactor

The disintegration of nuclei and the production of neutrons from photon-induced reactions may take different forms, for example the (γ,11), (γ,2n) and (γ,fission) reactions. The nuclides of the beryllium and deuterium have particularly low threshold energies of 1.667 MeV and 2.225 MeV for the (γ,n) reactions. These two materials are efficient moderator and reflector materials in fission reactors. Although their (γ,n) cross sections are quite low, this process may have an essential influence on the reactor dynamics because of the relatively long delay time of the photons emitted by the fission products. In this paper the neutrons emerging from the (γ,n) reactions will be referred as photoneutrons.