The Dynamic Modeling Of The Pressurizer Surge Tank Transients In Light Water Reactor Nuclear Power Plants

in nuclear power plants using pressurized water as the main coolant maintaining system pressure within prescribed limits is necessary. The volume of the main coolant expands and contracts with average temperature variations causing insurges and outsurges in the surge tank volume which is called "pressurizer". The surge tank acts in a way in which coolant pressure is maintained within prescribed limits. The surge tank is equipped with a spray and relief system as well as electric heating elements. The pressure is controlled by the increase in bubble populations through heating and / or flashing or steam condensation through water sprays.This paper analyses the transient behavior of the surge tank in a WWER type pressurized water nuclear power plant. An analytical method is developed for predicting pressure and water level variations in the surge tank following in or out surge processes. The analysis also takes into consideration the variation of the thermodynamic mass qualities inside the surge tank. The results obtained are compared with RELAP5/Mod3 and RELAP5/Mod2 as valid codes. D'Auria's model (FFT method) is employed for this comparative analysis.