Preliminary study of parameter uncertainty influence on thermal design and analysis for sodium heated once-through steam generator

In order to support the design work of steam generator for China Demonstration Sodium-cooled Fast Reactor, the parameters uncertainty analyses for tube length and evaporator outlet steam temperature have been performed by using Response Surface Method (RSM) and Wilks’ method. The functions of RSM have been validated with design data and experimental data. The influences of input parameters on tube length of evaporator and evaporator outlet steam temperature were analyzed. The values of maximum tube length and minimum evaporator outlet steam temperature were obtained with 95% probability with 95% confidence. Based on the results, the conclusions can be drawn: Wilks’ method can reduce the calculation runs while it would also provide larger safety margin than RSM method. In the thermal design of sodium heated OTSG, the tube length should account the margin of 12.9% or a conservative margin of 18.1%. 30 °C of superheat degree of evaporator outlet steam is enough to ensure that the fluid of evaporator outlet is high superheated steam.