考虑应力松弛和辐照影响的堆内构件压紧弹簧疲劳可靠性评估方法

For the fatigue failure modes of the holddown spring of reactor internals, the reliability evaluation was carried out based on the simulation method under the condition of considering the stress relaxation and the influence of radiation. Firstly, combining the fatigue model and the stress relaxation Landgraf model, considering the influence of irradiation on the fatigue parameters, the fatigue life model of the holddown spring was established. Based on the holddown spring fatigue life model, the reliability of holddown spring was defined according to the generalized stress-strength interference model and the sensitivity analysis was carried out. Taking the holddown spring of AP1000 passive pressurized water reactor as an example, the fatigue life with a reliability of 95% and 50% at 95% confidence level were calculated. The results show that the total fatigue life of the holddown spring decreases by 88.3% without considering the stress relaxation, and the prediction results are conservative from the perspective of economy. The results of sensitivity analysis show that the elastic modulus and fatigue strength coefficient have great influence on reliability. The holddown spring can be optimized by adjusting the design variables under certain reliability requirements.