S. Kakudate

Rail deployment and storage procedure and test for ITER blanket remote maintenance

Abstract A concept of rail-mounted vehicle manipulator system has been developed to apply to the maintenance of the ITER blanket composed of ≈400 modules in the vacuum vessel. The most critical issue of the vehicle manipulator system is the feasibility of the deployment and storage of the articulated rail, composed of eight rail links without any driving mechanism in the joints. To solve this issue, a new driving mechanism and procedure for the rail deployment and storage has been proposed, taking account of the repeated operation of the multi-rail links deployed and stored in the same kinematical manner. The new driving mechanism, which is different from those of a usual articulated manipulator or ‘articulated boom’ equipped with actuators in every joint for movement, is composed of three external mechanisms installed outside the articulated rail, i.e. a vehicle traveling mechanism as main driver and two auxiliary driving mechanisms. A simplified synchronized control of three driving mechanisms has also been proposed, including ‘torque-limit control’ for suppression of the overload of the mechanisms. These proposals have been tested using a full-scale vehicle manipulator system, in order to demonstrate the proof of principle for rail deployment and storage. As a result, the articulated rail has been successfully deployed and stored within 6 h each, less than the target of 8 h, by means of the three external driving mechanisms and the proposed synchronized control. In addition, the overload caused by an unexpected mismatch of the synchronized control of three driving mechanisms has also been successfully suppressed less than the rated torque by the proposed ‘torque-limit control’. It is therefore concluded that the feasibility of the rail deployment and storage of the vehicle manipulator system has been demonstrated.

Development of optical components for in-vessel viewing systems used for fusion experimental reactor

Optical components including imagefiber, periscope, glass, reflecting mirror and adhesive for lens are essential elements of in-vessel viewing system use for fusion experimental reactor and extensive of gamma irradiation tests have been conducted. These components were irradiated in the range of 1 MGy - 100 MGy under the average exposure dose rate of 1 X 106 R/h. As a result, the observation limit of the imagefiber specially fabricated for radiation hard is obtained to be 12 MGy at a illuminance of 8500 lx. Deterioration of transmissivity of three kinds of glass (alkaline barium glass, lead glass and synthetic quartz glass) is small compared with standard glass for commercial periscope. A periscope which was made of these glasses is visible even after 20 MGy at 8500 lx and in case of the standard periscope, the observation limit is 1 kGy at 8500 lx. Decrease in the reflectance on chromium nitride coated reflecting mirror is extremely small than aluminum coated and platinum coated mirrors at accumulated dose of 100 MGy. Two types of adhesive made of polyester resin and epoxy resin became discolored and exfoliated after 50 MGy.

Sensor based control test for remote installation of ITER blanket module

Abstract ITER blanket is composed of about 400 modules in the vacuum vessel (VV) for remote individual replacement. The most critical issue in the remote replacement of the blanket module is to install the module of 4 t with high positioning accuracy under the clearance of 0.25 mm between the module and two key supports on the VV. A new control scheme of ‘sensor based control’ has been developed using a combination of distance sensor for rough positioning and contact sensor for fine positioning so as to solve the issue. The performance test of the 4 t module installation under the clearance of 0.25 mm between the module and the key has been successfully carried out using a full-scale remote handling equipment, so that the feasibility of the newly developed control scheme has been demonstrated.

Mechanical characteristics and position control of vehicle/manipulator for ITER blanket remote maintenance

Abstract In International Thermonuclear Experimental Reactor (ITER), blanket maintenance requires the 4-tonne module handling with high positioning accuracy of ±2 mm. In order to meet this requirement, it is essential to suppress the dynamic deflection and vibration of the remote handling equipment due to sudden transfer of the module weight from/to the back-plate supports to/from the equipment itself during installation and removal. A new control scheme was proposed and tested so as to suppress the dynamic behaviors. As a result, the dynamic deflection of the rail and the acceleration of the manipulator were sucesessfully decreased to nearly zero. Based on the test results, the proposed control scheme was concluded to be effective so as to suppress this kind of dynamic effect during heavy component handling.

Development of divertor cassette transporters for ITER

A remote maintenance system for a divertor, an in-vessel component in a fusion reactor, is discussed. Results of design and fabrication of divertor cassette transporters and their performance are presented.

DIVERTOR PLATE SUPPORTING SYSTEM FOR FUSION EXPERIMENTAL REACTOR

The divertor plates of the fusion experimental reactor (ITER/FER) are operated under severe heat/particle fluxes and are categorized as the scheduled maintenance components. Thus, reliable supporting system to be compatible with remote maintenance is inevitably required for locking/lifting the divertor plate. For this purpose, the hydraulic supporting system composed of movable cotter by hydraulic driving mechanism is being developed. The basic feasibility of the hydraulic driving system has been successfully demonstrated and full scale mockup test is under way. This paper gives the design concepts and latest R&D achievements of the hydraulic supporting system for divertor plate.

Recent developments in remote maintenance for Fusion Experimental Reactor in JAERI

Two types of 1/5 scale models have been fabricated and tested to confirm the feasibility of the concepts of the rail-mounted vehicle in-vessel maintenance system and the blanket handling system for ITER/FER (International Thermonuclear Experimental Reactor/Fusion Experimental Reactor). As for the rail-mounted vehicle system, the deployment and storage of the rail, the replacement of the divertor plate and the accessibility to the first wall by the armor tile handling manipulator were demonstrated. As for the blanket handling system, the replacement of the blanket modules was also demonstrated. As the result of the demonstrations, the concepts of maintenance systems for the in-vessel components of divertor plates, armor tiles, and blanket modules were confirmed to be feasible. Therefore, the designs of these maintenance systems can be developed in detail on the basis of the database of the scale models in the engineering design phase of ITER/FER.<<ETX>>

Remote handling test and full-scale equipment development for ITER blanket maintenance

The technology of handling a 1-ton payload has been demonstrated using prototype transporter and manipulator/end-effector. Efforts have been made to develop an automatic procedure for module gripping and installation using sensor based feedback control. In this test, the end-effector is automatically aligned both in position and orientation relative to the module gripping points. This paper describes the prototype test results on sensor based control and the status of the test platform fabrication for ITER blanket remote maintenance.

Development of bore tools for blanket cooling pipe connection in ITER

According to the ITER R&D program, the bore tools for welding, cutting and weld inspection of blanket cooling pipes by the in-pipe access have been developed. In order to meet the ITER requirements, the YAG laser transmitted through a flexible optical fiber and the electro-magnetic acoustic transducer (EMAT) were adopted for welding/cutting and weld inspection, respectively. Their performance have been verified, including the movement and positioning in the cooling pipes. In addition, the radiation hard ultrasonic transducer (UT) and the leak detectors have been also tested. This paper describes the design outline and test results of bore tools developed for welding, cutting and weld inspection of the ITER blanket cooling pipes.

FEASIBILITY STUDY OF BLANKET HANDLING SYSTEM FOR FUSION EXPERIMENTAL REACTOR

Remote maintenance technology is essential for the realization of fusion experimental reactors, such as International Thermonuclear Experimental Reactor(ITER) and Fusion Experimental Reactor(FER), because the reactor components are activated by 14-MeV neutrons. Japan Atomic Energy Research Institute(JAERI) has been conducting the research and development to demonstrate the feasibility of remote maintenance equipments mainly for key components, such as divertor plates and blanket modules. Especially, the blanket modules are asymmetric structure, and are the heaviest(80 tons max. in weight) and the slenderest(20 m max. in length) of the in-vessel components to be handled remotely. The blanket modules are not frequently maintained but require high-grade maintenance technology, because the replacement of such structures must be carried out through the limited space of the upper port within the positioning accuracy of a few mm. In FER, JAERI has developed a new maintenance concept for the blanket modules. Key features of this concept are (1) the reliable toroidal movement of the blanket side modules inside the vacuum vessel in the cooperation of main and sub manipulators, (2) adjustment of the eccentric posture of the asymmetric blanket modules by a counter weight and (3) accurate installation of the blanket modules along the guide structures on the vacuum vessel. The feasibility study of the concept of the blanket handling system has been demonstrated by a 1/5 scale model in computer control.