Simulation of thermal mixing in main steam generator feedlines

Thermal mixing in a representative model of a main feedwater line that carries feedwater to the steam generator and auxiliary feedwater injector is investigated using the TEM-PEST Version L Mod 4 computer code; a single-phase, three-dimensional, time-dependent, hydrothermal analysis code. Transient simulation was performed and the resultant temperature histories were examined in order to assess the degree of thermal mixing and its possible implications concerning pressurized thermal shock and thermal fatigue cracking phenomena. Under certain auxiliary feedwater injector flow rates, thermal stratification was predicted