Heat transfer performance of multi-layer insulation system under the roof slab of pool-type LMFBR

The objective of this study is to evaluate analytically the heat transfer performance of multi-layer insulation system under the roof-slab of pool-type LMFBR. Therefore, we investigate combined natural convective, conductive and radiative heat transfer, and consideration is given to a one-dimensional system composed of cover gas space and multi-layer insulation structure. These area is enclosed between hot liquid sodium surface (about 773K) and lower part of roof-slab (about 373K). In this analysis, we take into account of the temperature dependence of the thermal conductivity, kinematic viscosity and thermal diffusivity of cover gas, and also the temperature dependence of extinction coefficient of sodium mist and emissivity of sodium attached surface. The number of radiation shield plates and the distance between adjacent radiation shield plates are varied as a parameter. (author)