Subchannel Analysis of Sodium-Cooled Reactor Fuel Assemblies with Annular Fuel Pins

摘要

Using a RELAP5-3D subchannel analysis model, the thermal-hydraulic behavior of sodium-cooled fuel assemblies with internally and externally cooled annular fuel rods was investigated, in an effort to enhance the economic performance of sodium-fast reactors by increasing the core power density, decreasing the core pressure drop, and extending the fuel discharge burnup. Both metal and oxide fuels at high and low conversion ratios (CR(velence)0.25 and CR(velence)1.00) were investigated. The externally and internally cooled annular fuel design is most beneficial when applied to the low CR core, as clad temperatures are reduced by up to 62.3 deg C for the oxide fuel, and up to 18.5 deg C for the metal fuel. This could result in a power uprates of up to approx44percent for the oxide fuel, and up to approx43percent for the metal fuel. The use of duct ribs was explored to flatten the temperature distribution at the core outlet. Subchannel analyses revealed that no fuel melting would occur in the case of complete blockage of the hot interior-annular channel for both metal and oxide fuels. Also, clad damage would not occur for the metal fuel if the power uprate is 38percent or less, but would indeed occur for the oxide fuel.