Development of Molten Core Relocation Analysis Module MCRA in the Severe Accident Analysis Code SAMPSON

Abstract

IMPACT is a complex software system under development at the Nuclear Power Engineering Corporation, that includes the severe accident analysis code (SAMPSON). SAMPSON is an integration of twelve modules and will be capable of simulating hypothesized severe accidents in a nuclear power plant in the final phase of the IMPACT project. As one of these modules, the Molten Core Relocation Analysis (MCRA) module simulates the relocation behavior of a molten core during a severe accident. MCRA adopts a multi-phase, multi- component, multi-velocity field model to simulate severe accident phenomena mechanistically. Herein, we describe flow regimes, interfacial area modeling and physics models such as the momentum exchange and phase change models. Two separate effect analyses are presented as verification of MCRA's models following the model descriptions. First, the fluid dynamics of the multi-velocity field model was verified in the calculation of nitrogen gas bubbling through water in Leung's experiment. Second, data of the JRC-Ispra KROTOS-37 experiment were adopted for verification of the multi-velocity field model and vaporization/condensation model. Calculation results of both analyses compared well with the experimental data. Finally, MCRA's integrated function involving the melting/freezing model was demonstrated by calculating two-phase flow with a fuel rod and molten fuel.

KEYWORDS:

• nuclear reactor safety
• severe accident
• simulation codes
• mechanistic model
• flow regime
• melting
• freezing
• vaporization
• condensation
• crust formation
• KROTOS
• experiment