Effect of Chemical Composition on J-R Fracture Resistances of Type 347 Weld for Surge Line Piping

The leak-before-break (LBB) design concept has been applied to high energy piping of Korean Standard Nuclear Power Plant to enhance safety and to reduce cost. For LBB analysis, it should be verified that the crack in structure would grow stably through the elastic plastic fracture mechanics. The J-R fracture resistance supply key parameters to LBB analysis. The materials for primary piping have enough fracture properties for LBB analysis except the pressurizer surge line piping made of Type 347 austenitic stainless steel and their welds have the smallest safety margin due to metallurgical variations. It has been predicted that the variations of mechanical properties are mainly affected by the microstructural difference originated from the chemical variations of the weld materials, but little systematic researches were directed in this matter. The purpose of this study is to investigate the chemistry effects on the fracture resistance of Type 347 welds