Straight wave UT technical for dissimilar metal weld of nozzle to safe-end in Reactor Pressure Vessel

Nozzle to safe-end joint in Reactor Pressure Vessel (RPV) belongs to Ferrite -Austenite type dissimilar metal weld. It is difficult to perform UT examination because of its coarse grains. Consider of deficient detectability of sub-surface planar defects by angle longitudinal wave technique, a straight longitudinal wave technique which takes safe-end as scanning surface is put forward based on joint structure. Experiment and research indicate it has very good detectability of planar defects which are vertical to the weld surface. This technique may be applied in RPV manufacture stage combining with angle longitudinal wave technique.