Mitsuaki Shimamura

Underwater Remote Handling Equipment for Reactor Internals Maintenance

More than fifty nuclear reactors generate about thirty-five percent of electricity in Japan. The need to operate these reactors safely and in a stable manner constitutes a very important issue. On the other hand, aged reactors are increasing and they are not necessarily designed and constructed using the latest technology. Stress Corrosion Cracking (SCC) on reactor internal components has become a major concern regarding aged reactors in recent years. Usually maintenance work such as inspection, repair, and preventive maintenance for core components is done by using underwater remote handling and robotic technology. It becomes very important to develop not only new efficient technology for inspection, repair, and preventive maintenance for all suspect components and but also the associated application technology for execution in a reactor. We have been developing several kind of remote handling equipment for underwater maintenance work. This paper describes some results obtained in the area of underwater remote handling that can contribute to the progress of plant reliability.© 2002 ASME

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

Remotely Operated Equipments for In-Vessel Inspection in BWRs

This paper describes development and application of remotely operated equipments for reactor internals ultrasonic testing (UT) and visual testing (VT) in boiling water reactors (BWRs) to enhance the availability of operating nuclear power plants. Stress Corrosion Cracking (SCC) in reactor internal components causes relatively low operating rate of BWR as one of the most important issues since the 1990s, and demand to inspect the reactor internals become greater. The remotely operated equipments have been developed for in-vessel inspection of core shrouds, shroud supports, jet pumps and so on. The equipments are evaluated in the point of the positioning precision as an application of a phased array UT technique and visual length measurement system. And as results of application to the actual plants and improvement, a Shroud vehicle, a Crawler vehicle and a Visual position measurement system are enhanced in an aspect of the accessible range and/or positioning precision. Their configurations and functional testing results are shown in this paper. As the other application, micro replication devices are developed for CRD Stub tube and shroud in BWR. This paper indicates the functional testing result using the prototype for the CRD stub tube with observing material microstructure.Copyright