Experiments in support of accident management for the PAKS NPP of VVER-440 / 213-type

Abstract

ABSTRACT One of the key means of increasing the safety of nuclear power plants is to ensure the prevention of accidents which could lead to core damage or even to core melt. If we look at the severity range, there is a group of accident sequences with a relatively large probability, when the core melt can be prevented by appropriate operator actions, namely by secondary and/or primary side bleed and feed. This is a completely new scientific-technical question in the case of VVER-440/213 reactor systems because, up till now accident management measures and procedures have not been applied to these plants. To support the development of accident management measures and procedures, an experimental programme has been initiated in Hungary so that the key phenomena – the two-phase natural circulation processes, and the effectiveness of bleed and feed – can be understood. The experimental basis of the programme is the PMK-2 facility. The test results are being used for validating the RELAP5/MOD2 code. In this report the experimental results of two beyond design basis accident sequences are presented, viz.: total loss of feedwater and LOCA with unavailability of high pressure injection systems.