Safety related states identification in nuclear power plant with VVER reactors based on the objective probabilistic assessment

A probabilistic assessment method for identification of safety related states during normal operation of a reactor unit is described. The applicability of this method is illustrated on the case of an abrupt loss of load (detachment from external grid) of the two Dukovany turbogenerators at the rated power level. Application of this universal method during the operation of nuclear power plants will enable such events or states to be identified as are not covered by intervention of the protective systems (steam generator tube rupture, partial break of the main steam or feedwater line, uncontrolled opening of safety valves). Early identification of safety related states at the reactor unit will facilitate control room personnel's decision-making and (after manual reactor tripping), intervention into the emergency rules