Keeping the melt inside of the reactor vessel is the key strategy of the management of severe accidents for the exploited, as well as for the newly designed reactors with pressurized water. The concept has been substantiated for emergency cooling of VVER-440 reactor at Loviisa NPP in Finland [1]. However, for more powerful reactor, such as VVER-1000, up to now it was considered that this concept did not work.

This work analyzes the problem of the interaction of molten corium with the reactor vessel. The work is representing the results of studies that were carried out as part of research with a goal to validate design functions of the system of containment the melt inside the VVER vessel.

The VVER or WWER is a series of PWR designs originally developed in the Soviet Union, and nowadays in Russia. The reactor plant of VVER-1000 type of V-320 series is a reactor plant with a water-cooled and water-moderated power reactor for NPP. It has an electric power of 1000 MW and a thermal power of 3000 MW. The plant consists of four loops, each one with a horizontal SG and a MCP. In the work the design analysis of the accident with melting of the core of the reactor plant V-320 was conducted on codes RELAP/SCDAPSIM/MOD3.4 and MELCOR. The main processes that determine the state of the core melting in the reactor vessel were analyzed. The main results of the calculation of the molten corium interaction with the wall of the reactor vessel were represented. The results of the preliminary calculated estimation of the melt behavior and the technical ability to hold the core melt in the vessels of PWR reactors were represented.

Based on the carried out analysis and implementation of technological and design study, the recommendations were made with a purpose to improve the safety of NPP with a reactor plant V-320 using the systems of melt restraining and cooling of the reactor vessel.

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