During the last few years the safety of the Hungarian Paks Nuclear Power Plant was reassessed in the framework of the AGNES project. Results of the program revealed that the safety of VVER-440/213 type reactors could be enhanced by modernizing a number of event oriented emergency operating procedures (EOPs) and the implementation of accident management (AM). Before the accomplishment of systematic AM all the possible thermal-hydraulic effects and consequences should be considered and experimentally verified.
This paper summarizes the most important findings of the relevant tests performed in the PMK-2 facility, which is a full-pressure, integral-type model of the Paks NPP. The present analysis concentrates on a particular method, the bleed-and-feed, applied in the primary or secondary circuit and conclusions are drawn for the effectiveness of this AM measure. Modelling of the thermal-hydraulic processes is extended with computer simulations using the RELAP5/MOD3.2 system code. Finally, a short assessment is given for the code capabilities to represent some significant phenomena of the transients.