Hisashi Hozumi

Development of Remotely Operated Inspection Devices for BWR Internals

Two ultrasonic testing (UT) devices to inspect the internals of nuclear reactor have been developed. The one is a jet pump UT device to inspect the inner weld line of the jet pump, and the other is a shroud UT device to inspect the outer weld line of the shroud. The jet pump UT device is mainly composed of an inspection probe scanner and a wheeled platform with a telescopic guide. Since the inspection probe scanner has been designed slim enough to pass through the narrow opening of the jet pump nozzle, it can be remotely positioned inside the jet pump transported by the wheeled platform. The shroud UT device is mainly composed of a flat-type remotely operated vehicle (ROV) and a positioning mast of ROV. The ROV is installed remotely on the outer surface of the shroud using the positioning mast. And the ROV has been designed thin enough to pass through the narrow gap between the jet pump and the shroud, so that it can move horizontally on the surface of the shroud with automatic cable feeding. Consequently, the proposed remote and automatic inspection devices can perform the inspection work in short time without using fuel handling machine (FHM). Therefore, the inspections can be performed simultaneously with the refueling work, which contributes to the shortening of regular inspection periods of nuclear power plants.Copyright

Hierarchical autonomous mobile control system of a patrol robot for nuclear power plants

The integrity of components of an operating nuclear power plant (NPP) is usually monitored on a daily basis by operator patrols. Currently, there is a great need to replace such human patrol activities by systems of automated remote monitoring in order to reduce radiation exposure and the severe workload imposed on operators. From this perspective, and under the sponsorship of Ministry of International Trade and Industry (MITI), the authors embarked upon a R&D project in 1991 with the objective of developing an autonomous mobile patrol system for NPPs. The project is scheduled to be completed in 1996. This paper describes the concept of the autonomous mobile robot system, which comprises a hierarchical autonomous mobile control system, a localization system based on pattern matching between the data profile from a laser rangefinder and an environment map, a method of constructing environment maps from 3D-CAD of a NPP, and a cableless robot system.