Simulation of RMI(Reflective Metal Insulation) design for air gap effect between multi-layer plate and side-wall

Nuclear power plants are sensitive to cope with various accident condition such as LOCA(loss of coolant accident) scenario. Debris with NUKON and calcium-silicate, used as insulation and flowed out at accident, is obstacle to ensure the RCS(Reactor cooling system) long-term-cooling during several months. Many considerations are carried out to solve the serious safety issues. For example, upgraded ECCS strainers have been installed at the bottom of containment building to filter debris mixture with pure cooling water. US NRC have recognized above phenomenon and suggested other alternative about replacing existing insulation(NUKON) with RMI(reflective metal insulation). It is well known for need to apply RMI insulation instead of existing NUKON insulation for solving the Nuclear Power plant's safety issue such as debris clogging and reactor stability. This paper especially covers RMI insulation performance reviews among the several design requirements and targets. The most important design factor except for design of multi-layer is air-gap effect between plates and side-wall. It is simply classified with three kinds : all contact type, single(center) contact type, 5mm gap type. Heat transfer coefficient variation according to design factors by CFD calculation is meaningful as with test data. All contact type has 17% effect compared to 5mm gap type.