核电厂主给水流量精准测量的超声技术研究

Research on Ultrasonic Technology of Accurate Measurement of Main Feedwater Flow in Nuclear Power Plant

为实现压水堆核电机组的小幅功率提升,研制了一种用于二回路主给水流量测量的高精度超声波流量计,其设计测量不确定度达到0.3%。通过不确定度分解的方法,逐项分析流量测量在高温高压下受到的影响。高温带来的流态变化对测量的影响可以通过常温常压下和中温下对校准系数的实流标定进行部分验证;管体结构尺寸的变化可以通过有限元仿真与高温高压静态实验装置的测量得到;流量积分算法引入的误差通过计算流体动力学(CFD)技术仿真获得,并进行实流验证。结果表明,通过利用国内现有条件下的流量标准装置,采用不确定度分解的方法进行试验验证后,每一分量都可被量化溯源,进而可保证主给水流量测量不确定度指标,实现最终的设计目标。

A high-precision ultrasonic flow meter with a design measurement uncertainty of 0.3%has been investigated and developed for the measurement of the main feedwater flow in the secondary loop.This flowmeter could be used to realize the small power enhancement of PWR nuclear power units.The influences of flow measurement under high temperature and high pressure were sequentially analyzed through the method of uncertainty decomposition.The influence of the flow condition variation caused by high temperature on the measurement can be partially verified by the real flow calibration of the calibration coefficient under normal temperature and pressure and medium temperature.The change of the tube structure size could be obtained by finite element simulation and measurement on a static experimental equipment which could create a high temperature and high pressure environment.The error introduced by the flow integral algorithm could be obtained by CFD simulation and verified by real flow calibration.The results show that each component can be quantified and traced back by using the flow standard device under the existing domestic conditions.Therefore,the measurement uncertainty of the main feedwater flowmeter developed in this thesis can finally achieve the design target.