AN EXPERIMENTAL STUDY OF ASSESSMENT OF WELD QUALITY ON FATIGUE RELIABILITY ANALYSIS OF A NUCLEAR PRESSURE VESSEL

The steam generator in PWR primary coolant system is one of the equipment made by our own country in Qinshan Nuclear Power Plant of China. It is a crucial unit belonging to the category of nuclear pressure vessel. The purpose of this research work is to make an examination of the weld quality of the steam generator under fatigue loading and to assess its reliability by using the experimental results of fatigue test of material of nuclear pressure vessel steel S-271 (Chinese Standard) and of qualified tests of welded seams of a simulated prototype of bottom closure head of the steam generator. A guarantee of weld quality is proposed as a subsequent verification for China National Nuclear Safety Supervision Bureau. The results of reliability analysis reported in this work can be taken as a supplementary material of Probabilistic Safety Assessment (PSA) of Quinshan Nuclear Power Plant. According to the requirement of Provision Ⅱ-1500 cyclic testing, ASME Boiler and Pressure Vessel Code, Section Ⅲ, Rules for Construction of Nuclear Power Plant Components, a simulated prototype of the bottom closure head of the steam generator was made in this work for qualified tests. To find the quantified results of reliaability assessment by using the testing data, two proposals are presented in this paper.