Abstract
Nuclear power plant safety is one of the most important part issues of international energy usage nowadays. Generation IV nuclear reactors have been investigated and developed for a period of time, and will be one of the the major electricity supplies for the future global energy requirements efficiently and safely. High Temperature Gas Cooled Reactor (HTGR) is one type of generation IV reactors, which is developed successfully and waited for being used to solve future the energy shortage problem worldwide. Although, there is already highly safe design for HTGR, but deeper understanding and manipulating the hypothetical severe accident is still necessary. Air-ingress accident analysis of GEN IV HTGR is the main purpose of this study. In this study, CFD (Computational Fluid Dynamics) is used for investigating the thermal-hydraulic phenomena in HTGR while air-ingress is happening there after. At the beginning, normal operating conditions is obtained by steady-state simulation. Transient simulation is used for understanding the thermal-hydraulic phenomena of the HTGR core since the severe accident incipience. The pipe between reactor vessel and steam generator, which is called hot gas duct, broke during the accident started. This pipe broken will cause the outside air diffused into the reactor vessel. Fuel assembly will be corroded by oxygen, due to a series of chemical interaction between oxygen and high temperature graphite. As a result, radioactive fission products may be released into outside environment space. Obviously, the corrosion problem on fuel assembly is the key issue of HTGR safety. After a long period of interaction between oxygen and fuel assembly, the fuels in the lower region of the core damaged the most. As a consequence, some safety devices are needed to be design and equipped for making air diffuses uniformly in vessel to avoid the non uniformed corrosion situation.