The procedures for searching conservative initial core states for some reactivity initiated accidents (RIA) taking into account xenon transients
26th Symposium of AER on VVER Reactor Physics and Reactor Safety (2016, Helsinki, Finland)
Reactor dynamics and safety analysis
Abstract
THE PROCEDURES FOR SEARCHING CONSERVATIVE INITIAL CORE STATES FOR SOME REACTIVITY INITIATED ACCIDENTS (RIA) TAKING INTO ACCOUNT XENON TRANSIENTSA.A. Pinegin, S.V. SemenovNational Research Centre “Kurchatov institute” Moscow, RussiaABSTRACTTaking into account energy field redistribution upon xenon transients is important problem of fuel cycles design and their safety analysis. Under fuel cycle design it is provided considerable reserves from limit values of local energy field. These reserves are intended to provide safety passing of xenon transients.In practice there are problems with accuracy of xenon transients simulating, because xenon transients have extreme sensitivity to some physical characteristics. Particularly, temperature reactivity coefficients and absorption cross-section of xenon-135 belong to such characteristics. The changes in these characteristics can lead to significantly changes in the course of xenon transients simulating. In the report it is discussed problems of accounting observable errors in xenon transients simulating during searching conservative initial states for some reactivity accidents.Reactivity accident consequences can significantly differ depending on scenario of xenon transient, in the course of which it was taken place a violence of equipment operation. In the report it is discussed different possible statistics procedures of searching conservative scenarios of xenon transients. For simplicity of analysis it is supposed that scenarios of xenon transients are determined by several parameters (initial power level, unloading power depth, initial position of CR CPS and etc.)In the report it considers the procedure of searching of conservative scenarios of xenon transients using statistical simulation of set of parameters, which determine the course of xenon transients, and initiation of violence of equipment operation within different time moments. Such approach allows to obtain effective statistical estimation of conservative scenarios characteristics. To searching global conservative scenarios of xenon transients it is analyzed the possibility of using simulated annealing algorithm. 26th Symposium of AER on VVER Reactor Physics and Reactor Safety 39 10 – 14 October 2016, Helsinki, Finland