Session: CS-07-04 Recent Developments in ASME Codes and Standards - 4 (with CS-08)

Paper Number: 177128

177128 - Fundamental Approach for Evaluating Allowable Flaw Sizes and Leak-Before-Break Condition Based on the Asme Code Section Xi Procedure Using Flat Plates Subjected to Tensile Loading 

Abstract: 

In order to flawed components of power plants be allowed for re-operation, estimated future flaw sizes of the flawed components are required to satisfy three safety conditions. Those are as follows: the allowable stress criterion, the final flaw depth criterion and the final flaw length criterion. The allowable stress criterion compares the applied stress in the pipe at the flaw location to the allowable stress that is determined by the combination of the failure stress and structural factors. The final flaw depth criterion represents the limitation of the flaw depth which must be less than 75 % of the pipe wall thickness, even if the flaw depth satisfies the allowable stress criterion. The final flaw length criterion represents the maximum flaw length which is determined by the failure stress for a through-wall flaw. These flaw sizes are determined by employing Limit Load Criteria. On the other hand, leak and break stresses for pipes can be estimated by Local Approach of Limit Load Criteria. Then, flaw depths and lengths corresponding to the Leak-Before-Break (LBB) area are simply expressed. This paper examines the relationship between the allowable flaw sizes and the LBB area using a flat plate model, and proposes a new allowable flaw length.

Presenting Author: Martin Negyesi Technical University of Ostrava

Presenting Author Biography: Studied material sciences at Czech Technical University in Prague. Has more than 10 years’ experience in the nuclear fuel safety related research. Worked for UJP Prague, Institute of Energy and Transportation (JRC, Petten, Netherlands) and Japan Atomic Energy Agency (Tokai-mura, Japan). Nowadays, a researcher at Technical University of Ostrava (Czechia), in the Centre for Advanced Innovation Technologies, Laboratory of Structural Integrity and Material Design.

Authors:

Martin Negyesi Technical University of Ostrava
Kunio Hasegawa Japan Atomic Energy Agency