Blanket Remote Handling System Research Articles

Irradiation Tests of the Sleeve for the Telescopic Arm of the ITER Blanket Remote Handling System

Irradiation Tests of the Sleeve for the Telescopic Arm of the ITER Blanket Remote Handling System

Design updates of ITER Blanket Remote Handling System to accommodate in-vessel environment

This paper presents the recent advancement of the ITER Blanket Remote handling system (BRHS), aimed at addressing the challenging in-vessel environment of ITER. Due to the combination of gamma radiation and recently identified in-vessel humidity, original design of the BRHS with plated carbon steels must be replaced with stainless steels design. The BRHS design was modified based on evaluation of the corrosion resistance of various metals in a humid environment under gamma ray irradiation, considering strength and manufacturability of stainless steels. Furthermore, authors have also found that maraging steel treated by a black chrome plating can withstand a cumulative dose of 1 MGy without corroding, enabling the use of maraging steel wrenches, which are essential for FW central bolt torquing. The feasibility of the remote maintenance equipment design, which partially utilizes ultra-high-strength steel while employing stainless steels for the entire system, was confirmed.

Analysis of implementing a rail-based maintenance system into a HELIAS 5-B device

This paper reports on the analysis of potential rail-based maintenance systems when implemented into a Helical Advanced Stellarator (HELIAS) 5-B device. The main purpose of such a system would be to handle and exchange the internal vessel components, namely the breeding blanket segments, which are expected to be the largest and heaviest components within the vessel. Other rail-based maintenance systems for tokamak devices, particularly the ITER Blanket Remote Handling System (BRHS), were studied, and their suitability when introduced to the differing constraints of a HELIAS device was determined. Rail-based systems envisaged for DEMO and CFETR devices were also studied. An ITER-like handling system was shown to be unsuitable for a HELIAS device of this scale. This is due to significantly higher blanket masses with an in-vessel operating space no larger than that of ITER, but with the additional complication of longer toroidal lengths and non-uniform vessel geometry. Movement of large components on rails like those found in DEMO and CFETR was shown to be more applicable to the HELIAS device. The main obstacle to the implementation of such rails would be the non-uniform geometry which complicates the selection of a rail path that avoids collisions with other in-vessel components, remote handling equipment, or the vessel structure itself.

The modeling and analysis for the natural frequency adjustments of Vehicle Manipulator for the ITER Blanket Remote Handling System

This paper describes a method to adjust the natural frequency of the Vehicle Manipulator of the ITER Blanket Remote Handling System (BRHS). The natural frequency was adjusted to avoid the seismic resonance by using the redundancy of degree of freedom of the Vehicle Manipulator. The Vehicle Manipulator was modeled and analyzed with lumped mass model with joint stiffness. The analysis has shown that the natural frequencies of the Vehicle Manipulator can be changed from 0.5 Hz to 12 Hz in the gripping posture of the First Wall in the vacuum vessel, suggesting that the dominant seismic frequency around 7Hz-9 Hz can be avoided.

Control System of Remote Maintenance Robots for the Fusion Device ITER

Remotely operated robotic systems are vital for maintaining the ITER plant—the world largest fusion device. To operate the ITER Blanket Remote Handling System (BRHS), its control system must have functionalities that are not familiar in conventional robot control systems; e.g., completely remote operation, multi-device control with reconfiguration during operations, and large-scale operation programming. We designed the control system to solve those problems: split the control system into the High-Level Control System, which has HMI functions, and Low-Level Control System, which has interfaces with robots, and enabled the remote operation from a different building; implemented abstract commands from the High-Level to the Low-Level Control system so that the robot devices can be reconfigured during an operation; developed hierarchical operation program that manages 2-year operations. We also designed specific functions of both levels of the control system and GUI of main components of the High-Level Control System.

Study of decontamination and maintenance for vehicle manipulator of ITER blanket remote handling system

Abstract The ITER blanket remote handling system (BRHS) will be operated in the ITER vacuum vessel (VV) after plasma operation to exchange the blanket first walls (FWs) and shield blocks (SBs), which can weigh up to 4.5 t and be larger than 1.5 m. The most important operation for the BRHS is the two-year maintenance campaign in which all 440 FWs must be replaced. The in-vessel components will have been activated by neutrons produced by the D-T reaction, with the total dose estimated to be 5 MGy. Moreover, activated dust will have accumulated in the VV and will contaminate the BRHS. The BRHS must first be transported to the red zone of the hot cell facility where it will be decontaminated remotely. The BRHS will then be transported to the hands-on area to be decontaminated manually and undergo maintenance. The ITER Organization has defined the dose rate criteria in the hands-on area as 100 μSv/h, thus, decontamination and maintenance activities must be performed in compliance with these criteria. In this paper, the parts that will require replacement in the two-year maintenance campaign are estimated based on the results of past irradiation experiments studies; areas of the BRHS that could not be decontaminated remotely are specified; and the dose rate to workers standing near the BRHS are calculated by using Monte Carlo N–Particle Transport Code analysis to establish the BRHS maintenance plan.

Designing for Remote Handling: the case-study of the ITER Plasma Position Reflectometry in-vessel antennas

The Plasma Position Reflectometry (PPR) system for the International Thermonuclear Experimental Reactor (ITER) consists of four reflectometers designed to measure the edge density profile at four locations, two of them with antennas installed inside the vacuum vessel in small apertures between blankets. To prevent damage, the antennas need to be removed/(re)installed by remote handling (RH) means before/after the removal/reinstallation of the blanket shield modules just above and below them. The RH operations shall be performed by the Blanket Remote Handling System (BRHS), [1], and require a tool not yet available in the ITER Remote Maintenance System. Herein, we describe a conceptual design of this tool that considers guidance and security to overcome some of the identified RH issues. The RH tool is designed to remove and (re)install the antenna in a single step using the translation and rotation capabilities of the BRHS (or a dual-arm manipulator attached to the BRHS) to bolt/unbolt the antenna to/from the support without extra operations. The RH tool is also designed to minimize the space required to operate between the blanket shield modules. However, the guidance pins of the tool are dimensioned according to the maximum positioning error allowed for the BRHS with a diagonal shape to guide the tool along the antenna. The design is implemented using pop-up fasteners and standard sizes authorised by the ITER Organization. A set of mechanical benchmarks are presented based on the CAD model of the tool.

Decontamination tests of dust under load for the ITER Blanket Remote Handling System

Radioactive dust will accumulate in the vacuum vessel (VV) of ITER after plasma operations. Consequently, the ITER Blanket Remote Handling System (BRHS) will be deployed into the VV to stably handle the blanket modules 1.5 m long, weighing up to 4.5 ton with high positioning accuracy. The BRHS itself must also undergo regular hands-on decontamination and maintenance in the Hot Cell Facility (HCF). However, the workers will be exposed to any activated dust that remains on BRHS component surfaces after remote decontamination. Past studies estimated the contaminated surface area of the BRHS, however, in this study, decontamination tests were performed and the dose rate to maintenance workers was calculated using the Monte Carlo N–Particle Transport Code (MCNP5). Decontamination tests were performed by using multiple test pieces of varying surface roughness made from SUS329J4L and two different types of brushes (nylon and SUS304) to simulate decontamination of the BRHS surface. Tungsten dust was pressed on the test pieces to simulate the loading by the rollers. After the test pieces were brushed the surface of each test piece was observed by using both optical and scanning electron microscopes. Dust was reduced by approximately 99% in all cases where the SUS304 brush was used regardless of surface roughness. The decontamination rate was used to estimate how much dust will be able to be cleaned from the BRHS surface. This paper describes the optimal decontamination tools with respect to the BRHS surface conditions to calculate and hopefully reduce the dose rate to maintenance workers so as to optimize the BRHS maintenance plan in the HCF.

Rescue tool for ITER blanket remote handling system

If a remote handling system were to become unrecoverable from the vacuum vessel of a fusion reactor, the reactor would be forced to cease all operations. Consequently, the means of recovery of remote handling systems in fusion reactors must be well-established. The ITER Blanket Remote Handling System will use an auxiliary rescue tool, which is introduced into the vacuum vessel and then remotely positioned to drive any failed joint. This paper presents the design and test results of a prototype rescue tool for the ITER Blanket Remote Handling System.We designed a rescue tool having compliant mechanisms to provide six degrees of freedom. The compliant mechanisms are completely passive to keep the tool simple and reliable. Testing of a prototype rescue tool by using a manipulator to simulate the remote environment, we found that our rescue tool is capable of being positioned remotely using a robot vision system owing to the compliant mechanism, which can absorb positioning error up to up to 4 mm in translation, 4° in pitch and yaw, and 2.5° in roll. Therefore, we conclude our rescue tool can be applied as the means of recovery for the ITER Blanket Remote Handling System.

Effects of humidity on radiation resistance of electroless Ni plating

Electroless Ni plating is commonly used as a coating of machined parts because of its superior corrosion resistance. The ITER Blanket Remote Handling System will use electroless Ni plating but will be operated in a γ-ray radiation environment, for which corrosion resistance—essential for the remote maintenance of ITER in-vessel components—has never before been demonstrated. This paper presents irradiation tests of electroless Ni plating carried out under dry or humid conditions. Corrosion resistance of electroless Ni plating was markedly affected in humid environments, however, in dry environments radiation resistance was verified. From surface analyses we can infer that radiolysis-enhanced corrosion was most likely caused by hydroxyl radicals produced from the interaction of water vapor and γ-rays in humid environments.

Design progress of ITER blanket remote handling system towards manufacturing

This paper presents an overview of the design of the ITER blanket remote handling system (BRHS), an indispensable component for ITER operation because the high irradiation environment will not allow humans to perform in-vessel maintenance activities. Instead, a large power manipulator will be deployed in the equatorial plane of the vacuum vessel and travel in the toroidal direction along an articulated rail, which will enable the heavy components to be handled with high positioning accuracy. The BRHS also includes a rail deployment system and various tooling and control systems in addition to its main components. This paper summarizes the design status of the in-vessel manipulator and its support system in the run-up to manufacture.

Availability improvement of ITER blanket remote handling system

Availability is of the utmost importance in remote-handling systems for fusion reactors. A number of factors are specific to this application in terms of availability. After investigating those factors, we have concluded that preventive maintenance is the best method to universally increase remote handling system availability. As such, we created a procedure through reliability block diagram analysis that takes availability, completion probability, and number of failures into account to determine the parameters for preventive maintenance and determine the quantity of spare parts required. By applying our procedure preventive maintenance increased the availability of the ITER blanket remote handling system from 46% to 88%, while the expected number of total failures was reduced from 5.5 to 1.6. Completion probability remained at virtually 100%, thus demonstrating that our procedure can improve system availability.

Irradiation tests of radiation hard materials for ITER blanket remote handling system

The ITER Blanket Remote Handling System (BRHS) will handle the blanket first walls (FWs) and shield blocks (SBs), which can weigh up to 4.5ton and be larger than 1.5m, stably and with a high degree of positioning accuracy. When the ITER has stopped plasma operations for maintenance, the BRHS will be installed in the vacuum vessel, whose components are radioactive, to remove and install the FWs and SBs. Therefore, the BRHS will be operated in a high radiation environment (up to 250Gy/h) having an estimated total dose of 5MGy during maintenance (maximum of two years). The radiation hardness requirement for ITER BRHS components is 1MGy total dose. As components may degrade by gamma irradiation, some equipment is expected to malfunction which causes delays in the in-vessel maintenance schedule. Therefore, failure mode and effects analyses (FMEA) were performed on the BRHS components and FMEA results suggest trouble with the power supply and signals due to degradation of the insulation of electrical components, and malfunctioning motors due to degradation of the lubricants of mechanical components. In this study, material property tests for O-rings and coating materials were performed to verify radiation hardness after the irradiation with gamma rays up to 5MGy.

Recovery from failures of ITER blanket remote handling system

Recovery operations for the ITER remote handling systems must be performed remotely because humans cannot access the radiation environment. Based on availability analysis, failure modes for the ITER Blanket Remote Handling System (BRHS) were analysed, which concluded that a loss of electricity is likely to occur and will require a recovery operation. To recover the ITER BRHS from this kind of failures, we focused on that the failed actuators can be driven if the motor shaft is driven from the outside, and developed rescue operation and a rescue tool. This method uses rescue manipulators, which handle the rescue tool we designed to drive failed actuators externally.

Impact hammer test of ITER blanket remote handling system

An impact hammer test of the full-scale mock-up of the ITER blanket remote handling system (BRHS) was carried out to validate the results of the seismic analysis of the BRHS which were performed using a finite element (FE) model. As the FE analysis of the BRHS predicted a vertical mode ∼8Hz, which coincides with a major natural frequency of the vacuum vessel of ITER, evaluating the dynamic response of the BRHS experimentally and measuring the system's damping is indispensable in verifying the structural design of the system. Recent preliminary impact testing on the full-scale mock-up of the BRHS showed that the mock-up has a vertical major natural mode having a natural frequency of ∼7.5Hz and a damping ratio of 0.5%. Several other major natural modes having frequencies less than 10Hz were found to have damping ratios ranging from 0.2% to 2%. It was confirmed that the natural major frequencies obtained in the experiments are in agreement with the major frequencies obtained via analysis.

Development of radiation hard components for ITER blanket remote handling system

The ITER blanket remote handling system (BRHS) will be operated in a high radiation environment (250Gy/h max.) and must stably handle the blanket modules, which weigh 4.5t and are more than 1.5m in length, with a high degree of position and posture accuracy. The reliability of the system can be improved by reviewing the failure events of the system caused by high radiation. A failure mode and effects analysis (FMEA) identified failure modes and determined that lubricants, O-rings, and electric insulation cables were the dominant components affecting radiation hardness. Accordingly, we tried to optimize the lubricants and cables of the AC servo motors by using polyphenyl ether (PPE)-based grease and polyether ether ketone (PEEK), respectively. Materials containing radiation protective agents were also selected for the cable sheaths and O-rings to improve radiation hardness. Gamma ray irradiation tests were performed on these components and as a result, a radiation hardness of 8MGy was achieved for the AC servo motors. On the other hand, to develop the radiation hardness and BRHS compatibility furthermore, the improvement of materials of cable and O ring were performed.

Conceptual design of Blanket Remote Handling System for CFETR

The China Fusion Engineering Testing Reactor (CFETR), which is a new superconducting tokamak device being designed by China, has a mission to achieve a high duty time (0.3–0.5). To accomplish this great mission, the big modular blanket option has been adopted to achieve the high efficiency of the blanket maintenance. Considering this mission and the large and heavy blanket module, a novel conceptual blanket maintenance system for CFETR has been carried out by us over the past year. This paper presents the conceptual design of the Blanket Remote Handling System (BRHS), which mainly comprises the In-Vessel-Maintenance-System (IVMS), Lifting System and Blanket-Tool-Manipulator System (BTMS). The BRHS implements the extraction and replacement between in-vessel (the blanket module operation configuration location) and ex-vessel (inside of the vertical maintenance cask) by the collaboration of these three sub systems. What is more, this paper represents the blanket maintenance procedure between the docking station (between hot cell building and tokamak building) and inside the vacuum vessel, in tokamak building. Virtual reality technology is also used to verify and optimize our concept design.

Concept design on RH maintenance of CFETR Tokamak reactor

CFETR which stands for Chinese Fusion Engineering Testing Reactor is a superconducting Tokamak device. The concept design on RH maintenance of CFETR has been done in the past year. It is known that, the RH maintenance is one of the most important parts for Tokamak reactor. The fusion power was designed as 50–200MW and its duty cycle time (or burning time) was estimated as 30–50%. The center magnetic field strength on the TF magnet is 5.0T, the maximum capacity of the volt seconds provided by center solenoid winding will be about 160VS. The plasma current will be 10MA and its major radius and minor radius is 5.7m and 1.6m respectively. All the components of CFETR which provide their basic functions must be maintained and inspected during the reactor lifetime. Thus, the remote handling (RH) maintenance system should be a key component, which must be detailedly designed during the concept design processing of CFETR, for the operation of reactor. The main design work for RH maintenance in this paper was carried out including the divertor RH system, the blanket RH system and the transfer cask system. What is more, the technical problems encountered in the design process will also be discussed.

Dust Removal Experiments for ITER Blanket Remote Handling System

(Received 25 September 2013 /Accepted 21 November 2013)To reduce maintenance workers’ dose rate caused by activated dust adhering to the ITER blanket remotehandling system (BRHS), dust must be removed from BRHS surfaces. Dust that adheres to the top surface of theBRHS rail from cyclic loading of the vehicle manipulator is considered to be the most difficult dust to remove.Dust removal experiments were conducted to simulate the materials, conditions, and cyclic loading of actualBRHS operations. The tungsten powder used to simulate the dust was squashed, and the area of contact bycyclic load was increased, but the powder was not embedded into the matrix. The increase in the area of contactincreased the total intermolecular force between a tungsten particle and the surface, which was considered themain force adhering dust to the test piece surface. A combination of dust removal methods, including vacuumcleaning and brushing, was applied to the simulated dust that adhered to the test pieces. The results showed thatvacuum cleaning is effective in removing dust from the non-cyclic loaded surface. The combined methods werehighly efficient in removing the dust that strongly adhered to the rail surface.

Rail deployment operation test for ITER blanket handling system with positioning misalignment

R&D for rail deployment equipment was performed for the ITER blanket remote handling system. The target torque for the automatic operation was investigated. The result shows that the 20% of the rated torque is adequate as the torque limitation for the automatic operation. A schedule for the procurement of the blanket remote handling system, which will be delivered to the ITER in 2020, was also shown.