Estimation of the Time Decay Constant

The functional analysis technique is applied for estimating upper bounds of changes in eigenvalues of integral equations. In particular, the method is used to determine the value of the time decay constant resulting from perturbations in a steady-state system. The method has no restrictive limitations as to the type of operator. The applications of this method are illustrated by examples from reactor theory. The effect of changes in cross sections of a fast system on the decay constant is studied.