A study on Integrity assessment methodology for graphite structure of the very high temperature reactor

The VHTR is a nuclear reactor that uses helium as a coolant and graphite as a reflector, moderator, and fuel compact. Helium has no phase change, because of chemically inert; there is no corrosion problem of the structure and activation of corrosion product. Graphite has an excellent ability to moderate the neutrons, small neutron absorption cross section, and mechanical and physical performance is great at high temperature. In addition, it has an excellent heat resistant that can maintain integrity as core structural materials at high temperature. Therefore, when accidents happen, there is no melting down of the core structure. There are various kinds of Graphite, and the physical and chemical properties are different and more research is needed