Model research of processes in coolant pressurizer system of WWER-440 and WWER-1000 nuclear power plants

A mathematical model is described of the condition of a steam pressurizer for the solution of accident and operating situations. In order to assess the operating reliability of the pressurizer the model also incorporates the calculation of heat stress in the wall. In order to determine the time dependences of thermodynamic parameters of the coolant, the balance equations for volume, weight and energy are considered as having movable limits in dependence on the time change in the primary circuit coolant volume. Equations are given describing the nonsteady state mode and the steady state of the pressurizer. An example is given of modelling accident situations of pressurizers for WWER-440 and WWER-1000 reactors under conditions similar to those which characterized the Three Mile Island accident. The advantage of the model is simple numerical processing which allows a great range of calculation variants without being demanding on computer time. The model may be used independently or as part of modelling the dynamics of the primary circuit of WWER-440 and WWER-1000 reactors. (J.B.)