Stratification of entrapped sodium as insulation in an LMFBR pool-type reactor vessel

The use of thermal stratification of a trapped layer of sodium is demonstrated as an effective method of insulating the thermal-hydraulic separator between the hot and cold pools in a pool-type reactor vessel for a liquid metal fast breeder reactor (LMFBR). Using the VARR-II computer program, a 2-D thermal-hydraulic analysis of the critical cross section of the fluid layer predicts a smoothly changing thermal stratification resulting in the separator exeriencing 11% of the temperature difference between the pools. Vertical nonadiabatic penetrations of the soidum layer create localized natural convection currents which are not found to significantly disrupt the thermal stratification. Several geometric and thermal boundary condition variations are also inspected