Calculation of the vibration noise by strong absorbers in a slab reactor

摘要

Neutron noise induced by small vibrations of a strong absorber has earlier been treated using two different models; the Feinberg-Galanin-Williams model uses a delta-function approximation of both the static and the vibrating rod. This model corresponds to preserving the static boundary condition (logarithmic derivative) at the surface of the moving rod; the perturbative approach called the epsilon/d model, starts with a finite absorber and represents the vibration by two stationary absorbing layers with strengths fluctuating in opposite phase. It was found that these two models lead to differing results, indicating a contradiction. In this paper we show that the reason for this contradiction is that the results based on the epsilon/d model are in error. The error is due to the fact that the effect of the static rod was neglected in the Green's function. The correct epsilon/d result is calculated and is shown to be equivalent to the FGW result. 12 refs. (Atomindex citation 28:021616)