Conference Agenda

In the event of a severe nuclear power plant accident, radioactive materials may be released into the environment as aerosols and transported over long distances by atmospheric motion, posing significant risks to human health and the environment. In order to accurately characterize the temporal and spatial dynamics of radioactive aerosol dispersion after a nuclear power plant accident, a dispersion numerical simulation method based on the Euler-Euler model was proposed. An aerosol concentration distribution solver was independently developed based on the open-source computational fluid dynamics (CFD) platform to realize the numerical simulation calculation of aerosol concentration distribution in a large space. The stable release and dispersion process of cesium iodide (CsI) aerosol in different environmental wind fields was studied. The results showed that the aerosol spreads in the wind field near the ground, and the concentration was always high in the area within 400 meters from the source (the concentration was higher than 1.47 × 10¹⁶ m^-3). With 1.47 × 10¹⁶ m^-3 as the detection standard, in a 5m/s ambient wind field, aerosol spreads to 3660 meters downstream of the source at 800s. Assuming that the evacuation time is 10 minutes, the danger degree is highest within 1.77km of the source as the center, and residential areas are not suitable within 4km.

The SCENES program is an integrated software package for nuclear power plant design and safety analysis independently developed by Shanghai Jiao Tong University. In order to verify the accident analysis ability of its system analysis code SCENES-netFlow, this paper selects ACME bench for modeling analysis. The ACME test facility is based on CAP1400 and is mainly used to verify the safety of the passive system in the event of small break LOCA and non-LOCA in the prototype power plant. This paper mainly analyzes the working conditions of CAP03 small break LOCA. The results show that the predicted accident sequence and test phenomena are consistent with the experience. The main results of numerical analysis can well reflect the experimental phenomena and agree well with the experimental results, indicating that SCENES-netFlow has the ability to simulate the accident conditions.

In the event of a severe accident at a nuclear facility, molten core components, known as corium, can form and pose a risk if not properly cooled. Corium can breach the reactor pressure vessel and cause the ablation of containment concrete in a process called Molten Corium Concrete Interaction (MCCI). Understanding MCCI is essential for evaluating containment safety, with previous studies using experimental and numerical approaches. Traditionally, system codes and lumped parameter methods have been employed, while CFD simulations have largely focused on corium spreading. This study introduces a novel approach using a multiphase flow technique to predict natural convection and phase change processes in MCCI. The model integrates multiphase heat transfer, phase change, mass mixing, and decay heat generation, implemented in the OpenFOAM CFD code. It is validated against a PCM melting experiment, showing excellent agreement with experimental data. The validated model is then applied to simulate the COMET-L2 experiment, incorporating decay heat sources and phase changes. A mesh sensitivity study and time-step variations are conducted for model convergence, with results closely matching experimental data. Detailed analysis of concrete ablation, crust formation, oxide relocation, and metal penetration into the basemat is provided, offering insights into the thermal behavior of corium and concrete during MCCI. This approach enhances the understanding of MCCI phenomena and supports improved safety assessments for nuclear containment.