Study of the DVI-LOCA in the AP1000-like reactor with MELCOR code.

• AP1000-like reactor studied with MELCOR2.1. • Steady-state and Design Basis Accident studied. • Nominal and 10% blocked steam generator tubes steady-states predicted accurately. • Double ended DVI-LOCA accident predicted comparable to the US DCD and UK PCSR. • Twelve cases studied with various models for ADS-4, steam generator and hot-leg. The paper presents the outcomes of the deterministic safety studies for a Pressurized Water Reactor based on the AP1000 design. The model was developed with MELCOR computer code using public references and qualified using data for nominal steady-state and double-ended Direct Vessel Injection line break accident. Emphasis was placed on thermal–hydraulic phenomena and modeling of the passive safety features. Different plant model variants were studied, including two models for the Automatic Depressurization System, two models for steam generators, and three models for hot-legs. Safety injections were investigated with a focus on the passive core cooling system, which is crucial during a Loss of Coolant Accident. Simulation results agree very well with available steady-state data. The model predicts expected plant behavior during a design basis accident, and results are not substantially different from predictions with system codes presented in the public reports. It shows that the developed model can be used in severe accident studies. [ABSTRACT FROM AUTHOR]