Development of modified piping evaluation diagram for leak-before-break application to Korean next generation reactor

Recently, the piping evaluation diagram (FED) is accepted in nuclear industry lor an efficient application of leak-before-break fLBB) concept to piping system at an initial piping design stage. The objective of this paper is to develop the modified FED, which can account for the variation of the material properties of the FED development stage and those of the assembly stage, hor this purpose, a parametric study was performed to investigate the effect of stress-strain curve on the detectable leakage crack length and the effect of fracture resistance curve on the LBB allowable load. Finite element analyses were also performed to investigate the effect of stress-strain curve on the LBB allowable load. Finally, a modified FED was proposed as a function of crack length and the allowable safe shutdown earthquake load. The LBB analyses based on the modified FED are in good agreement with those based on the traditional FED. By adopting the modified FED, the variation of material properties can be considered in the LBB analysis and the computing times required for the application of LBB during the design process can be considerably reduced. © 1999 Elsevier Science S.A. All rights reserved.