核燃料包壳外涂层直流电位法缺陷检测电路设计

Design of Defect Detection Circuit for Nuclear Fuel Cladding Outer Coating by Direct Current Potential Method

锆合金包壳管是核燃料棒最基本的组成部分,其外壳涂有一层陶瓷氧化膜涂层用于提升耐磨和力学强度。为了能有效检测外层陶瓷氧化膜缺陷情况,本论文提出一种在直流激励下对膜层不同两点间的电位差来表征缺陷情况,采用Buck电路和线性稳压电路相结合的拓扑结构,实现0~100 V,精度为0.5%可程控调节的直流激励源,再通过ADA4625芯片对被测试件表面的纳安级电流进行检测;并对测童的数据进行多项式拟合,以此来进一步表征缺陷情况。并通过大阻值样品进行了验证,结果证明该方法和检测电路符合锆合金表面陶瓷表面膜层检测的要求。

The zirconium alloy cladding is the most basic component of the nuclear fuel rod,and its shell is covered with a ceramic oxide film coating to improve wear resistance and mechanical strength.In order to effectively detect the defects of the outer ceramic oxide film,this paper proposes a potential difference between two different points of the film under DC excitation to characterize the defect,using a topology structure that combines a Buck circuit and a linear voltage regulator circuit.Achieve 0〜100 V,a programmable DC excitation source with an accuracy of 0.5%,and then use the ADA4625 to detect the nanoampere current passing through the surface of the test piece;perform polynomial fitting on the multiple measured data to detect Defect situation.It was verified by a large resistance sample,which proved that the method and the detection circuit meet the requirements for the detection of the ceramic surface film on the zirconium alloy surface.