Axial xenon oscillations in the cores of WWER-440 and WWER-1000 type reactors

Using modal expansions, analytical information has been obtained on the stability with regard to possible xenon oscillations during transients. The WWER-440 and WWER-1000 type reactors are shown to be stable. This is confirmed by calculating xenon-induced axial oscillations using the first core as an example and a three-dimensional code. The calculated power density and derived quantities oscillate with an amplitude decreasing in time. The oscillation parameters obtained depend on the time interval chosen. They can be extrapolated to a zero time interval. (author)