ABSTRAKT

Xenon Oscillations are one of the main sources of instabilities in nuclear reactors operating in the thermal spectrum. Due to economics of power generation, the power rating and the size of the reactors are increased making them unstable towards xenon oscillations. Conventionally, the study of xenon oscillations is performed by solution of neutron diffusion equation coupled with iodine concentration, xenon concentration and thermal hydraulics equations for different perturbations and core conditions, which is a very tedious process. In this paper, an approach for carrying out linear stability analysis of out of phase xenon oscillations using multipoint kinetics coupled with thermal hydraulic and xenon feedbacks is given. A large Pressurized Heavy Water reactor in is considered for the analysis. The reactor core is divided into two regions for the analysis to present a "proof of principle" for this approach. However, extension of this model for more regions, for better accuracy, though not trivial is quite straight forward. The nature of these oscillations depends on the operating power level and the magnitudes of the different reactivity coefficients. Hence, the operating power fraction (f), fuel temperature coefficient of reactivity (α_f) and coolant temperature coefficient of reactivity (α_c) are considered as the parameters for the analysis. Eigenvalue approach has been adopted to evaluate the linear stability boundary. Numerical simulations are carried out in order to verify the stability boundary.