Research Of Ultrasonic Immersion Testing System For Rod Travel Housing And Sealing Shell

Rod travel housing and latch housing belong to the primary circuit pressure boundary of nuclear reactor. Because of internal pressure, the internal surfaces sustain the largest stress, cracks on which are the most fatal flaws. Thus the circumferential detection is the keypoint when process ultrasonic testing on them. As to general cylinders, the circumferential detection usually uses pure shear wave.But due to the limitation of pure shear wave generating conditions, related criterions,like GB/T5777and NB/T20003.2, regulate that the method is only applicable to tubes,of which thickness to diameter ratio(t/D) are less than0.2.However, the t/Ds of the testing pieces are beyond value defined in the criterions above. After analysising related references and standards,it put forward that converted shear wave method can be used as the direction of the research, In order to verify the feasibility,ultrasonic water immersion test has been done on testing blocks. Through analysis on testing and simulation results, it concluded that pure shear wave could fully scan rod travel housing circumferentialy, though t/D is out of0.2.The optimum incident angle aL is9.6°.However for seal shell, pure shear wave method failed and converted shear wave with incident angle aL4.4°is perfect.Based on the study of workpiece supporting pattern and probe component follow method, Three general mechanical scan scheme has been proposed. After having weighted the effect of ultrasonic flaw detection and the feasibility of the mechanical structure, the plan1, of which probe components follow the pieces by buoyancy and driven by synchronous belt to walk straightly, has been adopted to build tank platform. As ultrasonic testing effect is sensitive to the oblique incidence angle, an ultrasonic probe angle adjusting device has been designed.The device has self-locking function, precise regulation and compact structure.The probe servo device could adjust water path, follow the pieces stablely, guarantee the stability of ultrasonic testing signal. For the purpouse of automation scan control,Siemens S7-200PLC has been used and corresponding PLC program has been compiled. The scan process can be hand and automatic control. After beening debugged in site, the system ran well.