On the behaviour of coolant temperature fluctuations in the coolant channels of pressurized water reactors for one-phase flow

Three one-dimensional models for calculating the interaction of coolant temperature fluctuations in a coolant channel with the adjacent fuel elements are described and discussed. A comparison of these models shows that fuel element structure and, in the case of more precise calculations, heat conduction in the materials have to be taken into account in noise analysis investigations. The fuel element structure and non-steady-state heat conduction processes also are of importance with regard to the transfer properties of power fluctuations to coolant temperature. Formation, transport and damping of coolant temperature fluctuations within the core as well as their time delay relative to the coolant flow rate are calculated and discussed. (author)