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

The steam generator in a PWR primary coolant system is one of the piec es of equipment made in China for the Qinshan nuclear power plant, Zhe jiang. It is a crucial unit belonging to the category of nuclear press ure vessel. The purpose of this research work is to carry out an exami nation of the weld quality of the steam generator under fatigue loadin g and to assess its reliability by using experimental results of a fat igue test of the nuclear pressure vessel steel S-271 (Chinese Standard ) and of qualified tests of welded seams of a simulated prototype of t he bottom closure head of the steam generator. A guarantee of weld qua lity is proposed as the quality assurance of safety for the China Nati onal Nuclear Safety Supervision Bureau. The results of the reliability analysis reported in this work can be taken as supplementary material for a Probabilistic Risk Assessment (PP-4) of the Qinshan nuclear pow er plant [1, 2]. According to the requirement of Provision 11-1500 CYC LIC TESTING, ASME Boiler and Pressure Vessel Code, Section III, Rules for Construction of Nuclear Power Plant Components [13], a simulated p rototype of the bottom closure head of the steam generator was made in this work for the qualified tests. Qualified tests with small sample size present a problem which is difficult to solve in reliability anal ysis, and are therefore of interest. Here, we offer proposals attempti ng to solve this problem.