[en] Following the Fukushima Daiichi Nuclear Power Station accident associated with the Great East Japan Earthquake, Hitachi Group has been developing the necessary equipment for decontamination work and environmental maintenance on the premises of the power plant, as well as for various investigations toward fuel debris retrieval. This paper introduces the following devices together with their application experiments: (1) 'ASTACO-SoRa'; dual-arm heavy machine robot for conducting heavy work as a work robot, (2) 'muscle robot'; flexible structure arm with resistance to high radiation environment, (3) 'PMORPH'; shape-changing robot as a research robot for investigating inside the reactor containment vessel, (4) 'Gengo ROV' and 'Tri-Diver'; robot for monitoring a torus room as underwater environment, and (5) boat with a diving function for surveying the underwater portion inside the reactor containment vessel. This paper also introduces next-generation robot technology that Hitachi plan to use in the future, with a focus on the operation support technology for robots with high radiation environment compatibility as well as the drones for surveying and monitoring. (A.O.)

[en] In this paper, a hovering control system for an underwater vehicle is proposed to support core internal inspections. The system adopted a localization part and a thruster control part. The former utilizes a map-matching method, referring cross-sectional shape data cut from a three-dimensional computer aided design (CAD) and structural shapes measured by a laser range system for horizontal positioning. A pressure sensor provides vertical positioning. The latter utilizes the thrust vector control, or reference thrust vectors are converted to each propeller thrust based on the vehicle's geometric structure. Experiments to evaluate performance of the proposed system were implemented at a mock-up of the reactor bottom part. As a result, it was confirmed that the position was detected with an accuracy of 48 mm, and for a flow velocity of 200 mm/s, it was verified that the vehicle hovered within 77 mm of a target point. Therefore, core internal inspections can be stably carried out even where there is external force caused by water convection flow. (author)

[en] In nuclear power plants, a system to localize remotely operated robots conducting investigations is required. In this work, a method using a stereo camera is presented for a high accuracy robot localization system. The proposed method extracts the virtual characteristic points on the outer side of the camera images and reduces the number of calculations, which is proportional to localization accuracy. In a fundamental experiment, the proposed method detects the robot position with a 13.6 mm error range for a 240-mm movement, satisfying the target accuracy: less than the measurement error range of the conventional method (25.6 mm). (author)

[en] This paper describes a localization system for a swimming robot to survey underwater narrow environments. In that environment, external sensors cannot be set up to localize the robot position, as there are many structures and the robot moves three-dimensionally. Therefore, the position needs to be calculated only by internal sensors. In this work, a new localization method based on map-matching is proposed, referring to cross-sectional shape data cut from a three-dimensional computer-aided design (CAD) data as an environmental map and structural shapes measured by a range sensor. As a range sensor, an ultrasonic sensor which is two-dimensional scanning-type was developed. The reflected signals of the ultrasonic sensor have some noise. Only structural shape data are extracted from the reflected signals. The image correlation is used as the matching method. Experiments to evaluate the performance of the proposed system were implemented at a mock-up environment. As a result, it was confirmed that the position was detected with an accuracy of 100 mm. The error is mainly caused by measurement error of the ultrasonic sensor that is used to calculate structural shapes. We concluded to improve the measurement accuracy of the ultrasonic sensor to reduce localization error. (author)

[en] For the decommissioning of the Fukushima Daiichi Nuclear Power Station, the primary containment vessel (PCV) internal survey for fuel debris spreading has been needed. The survey has been implemented using remotely operated robots. Localization of the robots during their operation is necessary to adjust sensor positions. In this research, we propose a localization method which combines a stereo camera-based method for absolute localization and a periodic structure tracking method for relative localization. The position accuracy for proposed method was verified in a mock-up test field, and it was confirmed that the position accuracy satisfied the required accuracy of 30[mm]. (author)

[en] For decommissioning of the Fukushima Daiichi Nuclear Power Station (FDNPS), the primary containment vessel (PCV) internal survey for fuel debris spreading has been needed. Remotely operated robots have been used for the survey. Localization of the robots during their operation is necessary to adjust sensor positions. However, it is difficult to calculate the robot position because the survey target areas have an unknown environment. In this research, we proposed a localization method which combines a stereo camera-based method for absolute localization and a periodic structure tracking method for relative localization for application to the unknown environment. The position accuracy for the proposed method was verified in a mock-up test, and we confirmed that the position accuracy satisfied the required accuracy of 30 mm. (authors)

[en] In Fukushima Daiichi Nuclear Power Station, before retrieval of molten fuel debris inside PCV, the operation such as decontamination, survey, repair and taking sample of fuel debris are implemented step by step. In case of investigation inside primary containment vessel (PCV), some remotely operated robots have been used for because human can't access to high radiation environment. Because a radiation dose is very high in PCV, therefore it is necessary to prevent the leak of radiation from PCV when a robot is inserted in PCV. Then a pipe of 100 mm inside diameter was let go through by the PCV wall, and the seal box which was completely sealed up attached to the end of pipe. The robot is put in the seal box beforehand and is inserted inside PCV through the pipe. So it is necessary for the robot to be small. In addition, it is necessary to be stable movement on rough plane inside PCV. Therefore shape change type robot 'PMORPH' was developed. This robot consists of three parts of the slim main body and two crawlers attached to the both ends of main body. When this robot is passed in the pipe, three parts lie in a straight line like 'I' shape. And when the robot moves on a rough plane, three parts are formed like 'U' shape. We minimized the use of electric parts in the main body against high radiation environment. And this robot carries a winch to let a sensor unit descend to basement floor. And we carried out the basement floor investigation (B2 investigation) using the robot to obtain information of fuel debris condition in March, 2017. As a result, some information of basement floor condition was acquired. In this paper, it is described the outline of the shape change robot and summary of the B2 investigation. (authors)

[en] The underwater vehicle system to inspect a nuclear power plant has been developed. In this work, the function of position detection to show the moving vehicle's position to operators is proposed. This paper describes the new method using map matching that consists of the cross-section shape data cutted by 3-D CAD data and the inner surface geometry measured by laser range finder. Finally, by the fundamental examination using the sensor unit, it was confirmed that the position was detected within 48mm. (author)

[en] A remote control system using external sensors is proposed for a sensor-less manipulator. The manipulator poses are estimated from camera images obtained by a stereo vision system. Based on the estimated poses, the sensor-less manipulator is controlled in real-time. This paper describes details of the proposed manipulator pose estimation system, the remote control system and results of a fundamental experiment using the sensor-less manipulator. (authors)

[en] The Fukushima Daiichi Nuclear Power Station (NPS) of Tokyo Electric Power Company (TEPCO) was the site of a severe nuclear accident after the 2011 Off the Pacific coast of Tohoku Earthquake and subsequent tsunami. Extensive structural damage occurred in the NPS facilities, including such environments as the reactor buildings and the primary containment vessels (PCVs). These are high radiation areas, having underwater areas, narrow spaces and so on. It is necessary to determine the extent of contamination and the location of debris to plan decommissioning operations. Survey targets in the past few years have been focused on inspections of the basement of the reactor buildings and the inside of the PCVs. Human operators cannot access these environments and work in them directly. Therefore, remotely operated robots and measurement technologies are needed to carry out various operations. For underwater surveys, we have developed a submersible crawling swimming robot that can avoid obstacles and inspect wide areas as it moves around. A shape-changing robot has been developed for passing through narrow spaces and crawling on rough floors. An ultrasonic imaging method combined with convex scanning and a divergent beam has been proposed to visualize environments in turbid water. In this paper, we describe details of the two survey robots and the underwater imaging method. (authors)