소듐냉각 고속로 열교환기의 고온 설계

The main heat exchangers in the Korean Generation Ⅳ demonstration sodium-cooled fast reactor are IHX(Intermediate heat exchanger), DHX(Decay heat exchanger), SG(Steam Generator) and AHX(Auxiliary heat exchanger). The tube shapes in current design of the IHX and DHX are straight while those of SG and AHX are helical. In KAERI, a large scale sodium test facility of the ‘STELLA’(Sodium Integral Effect Test Loop for Safety Simulation and Assessment) is under construction for the performance validation tests of heat exchangers as well as mechanical pump. In this study, high temperature design aspects of IHX, DHX and AHX are described, and preliminary stress analyses on the IHX and DHX operating at creep regime have been carried out. The materials of the shell and tube in IHX and DHX are Mod.9Cr-1Mo (ASME Grade 91) steel while the materials for tube and shell of AHX are 316SS and 304SS, respectively. Technical issues of creep-fatigue damage evaluation and actual welding for Gr.91 steel are highlighted.