Comparative Studies Of Key Models In Reactor In Severe Accident Codes

Accident phenomena in the reactor play an important role in the progress of severe accidents.Similarly,the accurate simulation of the accident process in the reactor is beneficial to determine the initial conditions and boundary conditions of the progress in the containment in the later stage of severe accidents.And the model selection is an important factor affecting the results of severe accident analysis,while the related research is still insufficient.Therefore,this paper firstly simulates the severe accident caused by the double ended cold leg break of AP1000 by MELCOR1.8.5 program and MAAP4.0.2.program.It is found that the generation of decay heat,hydrogen generation,the oxidation heat liberation,the eutectic reaction between core materials and the heat transfer of molten pool all have a great impact on the simulation results of severe accidents.Then,the CORA-13 benchmark,the QUENCH-16 benchmark and the LIVE-L4benchmark are simulated by MELCOR1.8.5 program to analyze the zirconium-water oxidation model,the zirconium-air oxidation model and the molten pool convection heat transfer model.The results of these three benchmarks show that these models in the MELCOR1.8.5 program can simulate the trend of the accident and some key phenomena.But the simulation of some key parameters such as hydrogen production,oxidation heat release,ZrO₂ layer growth rate,cladding failure time and temperature of molten pool is insufficient.Finally,through the program written in FORTRAN,the zirconium-water oxidation model,the zirconium-air oxidation model and the molten pool convection heat transfer model of MELCOR1.8.5 program are compared with other models using in other severe accident analysis programs.The calculation results show that the zirconium-water oxidation model which combines Urbanic-Heidrirck model with Bibilashvili-Sokolov model has achieved good simulation result;current zirconium-air oxidation models all overestimate the rate of zirconium-air oxidation reaction,but the simulation result of the NUREG-2 model using in the MAAP4.0.2 program is better than the result of the Benjamin model using in the MELCOR1.8.5 program;mini-ACOPO model can greatly simulate the convection heat transfer in the molten pool of LIVE-L4 benchmark.