An analytically solvable, axially non-homogeneous reactor model II. Reactor kinetic approximations

In a previous publication, a 2-D reactor model was introduced which contained a partially inserted thin absorber. Both the static flux, as well as the noise induced by the vertical oscillations of the rod were calculated by analytical methods. In this paper the validity of certain reactor kinetic approximations of the dynamical problem are investigated in the same reactor model. The induced noise is calculated in the adiabatic and in the plateau frequency approximation and compared with the exact solution. The significance of these two approximations is that they can be applied with existing core calculation codes either directly, or with minor modifications.