Feasibility Research On RT Test Method Replace Of TOFD Test Method In AP1000 Steel Containment

Unit1 and Unit2 Nuclear Island(referred as NI)of Haiyang nuclear power plant(referred as NPP)adopts the most advanced third generation AP1000 pressurized reactor nuclear power technology.The function of steel containment vessel(referred as CV)of AP1000 NPP is to remove sufficient energy from CV to guarantee that CV will not overpressure under designed basicaccident.CV is composed of CV top head(referred as CVTH),CV bottom head(referred as CVBH)and CV rings.After the CV ring plates are welded,100% radiographic test(referred as RT)shall be conducted to the weld seams.This article mainly focuses on the analysis of RT that performed after the welding of CV ring plates,analyzes the advantages and disadvantages during actual construction process.Meanwhile,with consideration to the deficiencies of in-service RT during construction,the possibility of replacing the in-service RT by Time Of flight diffraction(referred as TOFD)method was discussed.Firstly,summary to site RT work and investigation to TOFD at earlier stage were conducted.In the following experiment,simulated weldments were made,with various artificial defects embedded in the simulation sample.Test is made to the simulation sample using TOFD and RT methods,and then the test results of these two methods are compared with the test ability to the defects.At last,the previous test results according to the dissection of the artificial defects were verified,and then the advantages and disadvantages of the two test methods were analyzed.TOFD technology has the distinct advantages than the RT technology in the various fields such as the relevance ration of the defects,the measure to the length,depth and height of the defects,and the test efficiency,as shown in the test results.The TOFD method should be considered in the construction progress of CV in future.At present,the second stage of Haiyang NPP project and Sanmen NPP and the following inland power plants will be AP1000 units,and the research in this article will provide some lessons and instruction to the management of Non-destructive testing quality of Haiyang extension project and other newly built nuclear power project site.