Simplified assessment method for defects of welding joint area at piping safety end of pressure vessel of AP1000 nuclear reactor

Abstract

The invention relates to a simplified assessment method for defects of a welding joint area at a piping safety end of a pressure vessel of an AP1000 nuclear reactor. The method comprises the following steps of: characterizing the detected dimension of a circumferential inner surface defect, and determining a defect depth a and a defect length l; calculating primary membrane stress sigma m which is vertical to a defect surface at the position of the circumferential inner surface defect in absence of the defect under an assessment working condition; calculating the relation of primary bending stress sigma b which is vertical to the defect surface at the position of the circumferential inner surface defect in absence of the defect and an extra bending moment M which is borne by the safety end through three-dimensional finite element analysis; determining the primary bending stress sigma b which corresponds to a resultant bending moment Mt according to the resultant bending moment Mt under the assessment working condition; calculating the rheological stress sigma f of a material in the welding joint area, and calculating a stress ratio SR which is equal to (sigma m+ sigma b)/ sigma f; calculating the relation of the stress ratio, a nominal defect length and a nominal permitted defect depth according to a three-dimensional finite element model; and judging whether the defect depth a is less than or equal to the permitted defect depth a or not.

Description

technical field [0001] The invention belongs to the technical field of structural integrity assessment, and in particular relates to a simplified assessment method for the circumferential inner surface defect of the dissimilar metal weld zone at the safety end of the AP1000 third-generation nuclear reactor pressure vessel. It is a simplified evaluation method for evaluating and judging the safety of pre-service and in-service circumferential over-standard defects in the safety end weld area under specified operating conditions, and is applicable to the safety management and control of nuclear power equipment. Background technique [0002] As a clean and efficient energy source, nuclear power is being vigorously developed in our country. Nuclear safety is the lifeline of nuclear power development. Due to its special reaction conditions and technological process in the nuclear power industry, once an accident occurs, it will cause catastrophic consequences. Ensuring the safe...

AI Technical Summary

Problems solved by technology

In the existing international simplified methods related to the defect assessment of nuclear power equipment, the safety end of the nuclear reactor pressure vessel with a complex geometric structure is generally simplified as a straight pipe. Allowable defect size guidelines, evaluating the safety of defects, these methods do not accurately account for the influence of complex structural geometry on the safe side

Butt welded joints are generally simplified to two materials: the base metal and the weld. According to the different positions of the cracks in the base metal and the weld, only the mechanical performance parameters of the corresponding materials are taken for analysis. For the four materials (two weld

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