Assessment of the VVER-1200 reactivity coefficients on the basis of the data measured at the energy power levels

Abstract

Abstract Reactivity coefficients in respect to the fuel temperature and coolant density are the important integral parameters, which determine behavior of nuclear reactors in case of accidents. Experimental justification of these coefficients in the operating reactor is a quite complicated task. Changes of the coolant density and fuel temperature are the interdependent processes, which are difficult to separate. Experiments with excitation of axial and diametrical xenon oscillations, which were initiated by moving of the CPS CR (control rods of the control and protection system) group or an individual CPS CR, were carried in the framework the commissioning tests in the VVER-1200 reactor. Using the methods of mathematical statistics, we carried out multiple modelling of experiments with excitation of axial and diametrical xenon oscillations. Actual values of the reactivity coefficients, as well as some other parameters ensuring the best agreement of the calculated and experimental data were evaluated with the help of Bayes theorem.