A study of the influence of temperature dependent thermal conductivity on static power coefficient of PFBR oxide core using a variational one dimensional finite element methodology

A study has been carried out to examine the influence of temperature dependent thermal conductivity on the static power coefficient of reactivity for Prototype Fast Breeder Reactor (PFBR) oxide core. Change in core material density, core boundary movement, core 1 to core 2 fuel movement, Doppler coefficient and spacer pad expansion effects due to power rise, have been considered for calculating the power coefficient. For temperature rise calculations for the case of temperature dependent thermal conductivity of fuel, one dimensional finite element method based on variational approach has been applied. It is observed that for the case of temperature dependent thermal conductivity, average temperature of the fuel pin in the middle portion is higher but it is lower in the bottom and upper part of the pin than the case of temperature independent thermal conductivity. Because of this opposing effect, over all static power coefficient is influenced, marginally though it is higher for the case when thermal conductivity is temperature dependent. The paper provides the details of the results. (author). 2 refs., 2 tabs., 1 fig