CONVERGENCE LIMITS IN PERTURBATION THEORY

Perturbation theory is a powerful technique which is often used in reactor physics as a first-order fast tool suitable to estimate the system response to small perturbations. Thanks to recent advancements in the field of numerical evaluation of higher flux harmonics, it is possible, in principle, to increase the perturbation analysis order, allowing to improve the estimation of system parameters and to reconstruct the flux distribution, also in the presence of non-linear perturbations. In this respect, it is important to assess the conver- gence properties of such methodology. The aim of the present work is to investigate the convergence behaviour of the method for perturbations of different parameters and for different systems, in order to draw some conclusions on its limits of validity.