Development of shroud remotely operated vehicle for ultrasonic testing (Formulation of design requirements and development of a vehicle for internal surface operations of shrouds)

This paper presents the development and application of phased array ultrasonic testing (PAUT) and a remotely operated vehicle (ROV) for the in-vessel inspection of boiling water reactor (BWR) internals. Since the 1990s, stress corrosion cracking in reactor internals has emerged as a critical issue, leading to an increasing demand for thorough inspections. This paper highlights the advantages of the water immersion method and the outcomes of ROV development. Notably, the authors developed a flat-type ROV for shroud inspection named the Shroud Vehicle for Shroud I.D., which can adhere to the shroud surface using thrusting propellers and mechanically scan through a circle opening as small as approximately 270 mm. The positioning accuracy of the ROV and its applications for shroud UT are also tested.