Inspection technology of Korean standard Reactor vessel

This paper is for the inspection technology of Korean standard Reactor vessel. KPS performed Korean standard Reactor vessel inspection for a part of Yonggwang unit 5 and full inspection of Yonggwang unit 6 on November in 2001. Korean standard Reactor vessel is different from Westinghouse and Framatome plants in design and material. Understanding design, structure and material is very important to prepare and to perform Reactor vessel inspection. Korean standard Reactor vessel has 6 Stabilizer lugs, 6 Core stop lugs and one Flow Baffle around Lower head to Bottom head weld(G4). They make very difficult to perform scanning of G4 by transducers and to install Lower Platform of robot system. Korean standard Reactor vessel has 2 Outlet Nozzles, 4 Inlet Nozzles and small curvature of Inner Radius regions. That small curvature's Inner Radius region needs a special technology to perform the area more than 90% of whole examination volume. The most significant difference of Korean standard Reactor vessel is that it does not have Safe End region because both of Reactor vessel and main reactor coolant system piping are carbon steel. Therefore, the technology for this nozzle to piping weld is very unique to be compared with other Westinghouse or Framatome plants. Described above, the inspection technology of Korean standard Reactor Vessel is very different from other Reactor Vessel due to different internal structure and material. The company which performs this 10 years ISI in future will need much investigation of structure and material to succeed in Reactor vessel inspection of Korean standard plant