Thermal hydraulic analysis of the regimes with unmanageable control rods movement and ejection for the reactor strength estimation

Abstract

The article presents results of research (thermal-hydraulic analysis) of initiating events (regulatory regimes), associated with the uncontrolled movement and ejection of control rods that had previously not been considered quantitatively in the evaluation of thermal shock and cyclic strength of the reactor vessel and internals. The purpose of the research is preliminary evaluation of the influence selected regimes to the reactor components, preparation of boundary conditions for further strength analysis, based on which will make the final conclusion about the impact of these regimes. Research has a scientific and practical significance, because neglect of these conditions can lead to a distortion of the calculations results on the basis of which a decision on the possibility of extending the service life of VVER-1000 was made. The research was conducted by performing a computational analysis using code RELAP5/Mod3.2. In accordance to IAEA recommendations in this case conservative approach is applied to the selection of initial and boundary conditions. Calculation analysis showed that the considered initial events are representative and should be considered in VVER-1000 life extension, but strength analysis is required for confirmation