CASS FRACTURE TESTS USING FLAT PLATE SPECIMENS WITH A SURFACE FLAW

ABSTRACT JSME rules for fitness for service have flaw acceptance rules for cast austenitic stainless steel (CASS) pipes. They allow applying two-parameter and elastic-plastic fracture mechanics methods using Z-factor. However they do not clearly describe whether limit load method is applicable for the case of no or low thermal aging condition. The authors performed tensile fracture tests using flat plate specimens with a surface flaw and confirmed that limit load method is applicable in the conditions of no thermal aging and even fully saturated thermal aging with high ferrite number. Also the plate with a shallow flaw ruptured at the critical stress defined by nominal stress at rupture-flaw depth curve in the code case which was determined by the similar flat plate tests of stainless steel or nickel alloy specimens. These results will be reflected to the revision of the code

PVP2008-61829 RESIDUAL STRESS EVALUATION OF DISSIMILAR WELD JOINT USING REACTOR VESSEL OUTLET NOZZLE MOCK-UP MODEL (REPORT-1)

ABSTRACT In recent years, the occurrence of primary water stress corrosion cracking (PWSCC) in Alloy 600 weld regions of PWR plants has increased. In order to evaluate the crack propagation of PWSCC, it is required to estimate stress distribution including residual stress and operational stress through the wall thickness of the Alloy 600 weld region. In a national project in Japan for the purpose of establishing residual stress evaluation method, two test models were produced based on a reactor vessel outlet nozzle of Japanese PWR plants. One (Test model A) was produced using the same welding process applied in Japanese PWR plants in order to measure residual stress distribution of the Alloy 132 weld region. The other (Test model B) was produced using the same fabrication process in Japanese PWR plants in order to measure stress distribution change of the Alloy 132 weld region during fabrication process such as a hydrostatic test, welding a main coolant pipe to the stainless steel safe end. For Test model A, residual stress distribution was obtained using FE analysis, and was compared with the measured stress distribution. By comparing results, it was confirmed that the FE analysis result was in good agreement with the measurement result. For mock up test model B, the stress distribution of selected fabrication processes were measured using the Deep Hole Drilling (DHD) method. From these measurement results, it was found that the stress distribution in thickness direction at the center of the Alloy 132 weld line was changed largely during welding process of the safe end to the main coolant pipe

PVP2009-78001 SIMPLIFIED STRESS INTENSITY FACTOR EQUATION FOR SCC PROPAGATION IN THE PIPE WELDS (STEP 2)

ABSTRACT Considering characteristics of PWSCC's propagation behavior of the dissimilar welding joint of the safe end nozzles, an axial crack was modeled in a FE (Finite Element) model as a rectangular shape with larger aspect ratio. The stress intensity factors at the deepest point of the crack were calculated with change of crack depth. Using the influence coefficients, the simplified equation of stress intensity factor with parameters of radius/thickness and thickness/weld width was proposed. The contents of this paper is revised from the paper already presented [1] by further investigation for the shallow cracks with less than 20% thickness