Numerical Analysis Of Jet Flow Field In Steam Generator Tube Rupture

The steam generator is one of the main equipments of a nuclear power plant,located in the connection part between the first and second circuits,and is one of the main barriers to prevent the release of radioactive materials into the environment.The safe and reliable operation of the steam generator has a very important impact on the safe and economic operation of the entire nuclear power plant.The SGTR accident has received widespread attention because of its importance in nuclear power safety.At present,most of the international studies on SGTR accidents are based on air-water two-phase atmospheric pressure jet experiments,while domestic studies are more concerned with the system response,but not enough works on numerical simulation of jet flow changes near the heat transfer tube in the actual flow field.In this paper,we use CFD method to numerically study the heat transfer tube of the steam generator under a breach accident.Based on the CPR1000 steam generator,this paper refers to the numerical simulation results of related scholars,makes a reasonable simplification of the 9×9 heat transfer channel of the steam generator.A three-dimensional breakout pipe model of the steam generator is established.The two-fluid model is used to describe the jet flow state more accurately,and at the same time a boiling model is introduced to consider the bubble breaking process.On this basis,CFD simulations are carried out for two types of breaks in the steam generator,which are heat transfer tube double-end shear fracture accident and longitudinal fracture accident.By changing the operating boundary conditions and the geometric characteristics of the break,Several characteristics including the jet flow pattern near the break,the numerical changes of the jet core,the gas diffusion process,the influence range of the jet flow energy,the decay law and the force analysis of the adjacent tube bundle in the jet are studied.And on this basis,the empirical relationship equation of the jet velocity core is established.The calculation results show that the overall jet morphology normalized simulation results are in good agreement with the experiments of Herranz,and the empirical relationship equation is established for each breach accident after considering the numerical simulation results.The empirical relationship equation specify that,for the double-end shear fracture accident,the inlet Reynolds number is the main correlation factor of the jet core,while the breach height is a weak correlation factor.For the longitudinal breach accident,the impact of the breach shape on the jet is more dramatic at this time,and the correlation of each fitted equation is higher than 0.95,which has a high reliability and would provide some technical support for the actual steam generator nuclear safety in the engineering field.