Remote Handling System Research Articles

Antifriction characteristics of the magnetron sputtered MoS2 coating of ITER blanket module bolted joints in high vacuum at elevated temperature [formula omitted] =250 °C

The high values of bolt preload force Fa = 90–1200 kN created by the ITER remote handling system can be achieved by using dry coating lubricants such as magnetron sputtering film MoS2 or WS2. An expression was determined to estimate the contact pressure based on the number thread turns and the width of the thread contact area in fastened assemblies that used the Spiralock technology. This study investigated the tribological aspects of the magnetron sputtering MoS2 coating at different thicknesses hc = 6.4–21 μm, contact pressures pa = 20–1200 MPa against the spherical pin (austenitic stainless steel 316L(N)-IG) at elevated temperatures of T = 250 °C in vacuum pv = 10−2–10−3 Pa. Friction data for “humid” and “dry” rectangular specimens with MoS2 coating were obtained and compared. With an increase in the thickness of the coating from 6.4 μm to 21 μm, we obtained a distinct stabilization the friction coefficient of the low friction coating for each given regime of wear that diminished from 0.09 ± 0.010 to 0.05 ± 0.005. The wear mechanism of the “layered MoS2 coating/metal substrate” tribosystem resulted in significant plastic deformation along the sliding direction of the MoS2 solid lubricant as well as microgrooving and microploughing of the coating by the asperities of the flat contact spot of the spherical pin. Regardless of the type of bolted pair alloys used, we concluded that it is necessary to deposit a low friction coating on both the internal and external threads of the ITER blanket module bolted joints that use the Spiralock technology.

Research on accurate morphology predictive control of CFETR multi-purpose overload robot

The CFETR multipurpose overload robot (CMOR) is a critical component of the fusion reactor remote handling system. To accurately calculate and visualize the structural deformation and stress characteristics of the CMOR motion process, this paper first establishes a CMOR kinematic model to analyze the unfolding and working process in the vacuum chamber. Then, the dynamic model of CMOR is established using the Lagrangian method, and the rigid-flexible coupling modeling of CMOR links and joints is achieved using the finite element method and the linear spring damping equivalent model. The co-simulation results of the CMOR rigid-flexible coupled model show that when the end load is 2000 kg, the extreme value of the end-effector position error is more than 0.12 m, and the maximum stress value is 1.85 × 108 Pa. To utilize the stress-strain data of CMOR, this paper designs a CMOR morphology prediction control system based on Unity software. Implanting CMOR finite element analysis data into the Unity environment, researchers can monitor the stress strain generated by different motion trajectories of the CMOR robotic arm in the control system. It provides a platform for subsequent research on CMOR error compensation and extreme operation warnings.

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

A methodology for the selection of low friction/anti-seize coating in applying bolted joints of ITER blanket modules

The application of bolted joints with the Spiralock®/Selflock® technology for remote handling system in fusion machines leads to develop a methodology for selection a low friction/anti-seize coating in applying sliding surfaces of high-loaded threaded fasteners. This study discusses the analytical engineering method for calculation the maximum/minimum allowable friction coefficients in the thread and on the bearing surface during the tightening/untightening procedure. Calculations were made to determine the maximum/minimum allowable coefficient of friction in threaded pairs used for the ITER Blanket Module Connections and enhanced flux First Wall Panel fasteners (bolts with a regular metric thread/nuts with a self-locking thread, Spiralock®/Selflock® technology) of the ITER fusion experimental reactor under maximum torque conditions of the robot manipulator (remote handling system) and tensile load (preload) generated in the bolt during the tightening/untightening procedure. Design features of the Spiralock® technology were derived for calculation the working ranges of thread friction coefficient in the threaded pairs of the Blanket Module Connection and enhanced Heat Flux First Wall Panels fasteners at different coefficient of thread proportionality values (ζ=0.45–1.00). The lowest thread friction coefficients were obtained by the coefficient of thread proportionality ζ=1.00: 0.022≤μth≤0.171 for the M24 × 3 SB Electrical strap central bolts, 0.013≤μth≤0.047 for the М52 × 4 Outboard Flexible Cartridge central bolts, 0.010≤μth≤0.055 for the M64 × 4 Inboard Flexible Cartridge central bolts. The new method of determining the total tightening torque of the M24 × 3, M52 × 4, M64 × 4 bolted joints fastened to the Spiralock® female thread under conditions of elastoplastic, plastic deformation was applied to assess the suitability the solid lubricating coating MoS2 (VNIINP-212) under preload force Fa=10–1200 kN. The performed design verification indicated the significant differences in the calculated tightening torque obtained according to the standard and proposed method for the Spiralock® female thread by the plastic deformation of the tip of bolt thread and change of sliding friction coefficient depending on the contact pressure.

Concept of operation of the Agile Robot Transporter for ITER in-vessel maintenance

ITER machine availability is crucial for fusion reactors in order to be the main source of electricity, which is affected by many aspects. This paper focuses on maintenance aspects of the machine. As the plasma facing components inside the fusion reactors become highly activated caused by the neutrons generated by fusion reactions, maintenance of the fusion reactors needs to be done by remote means. In order to increase machine availability, it is required to have efficient maintenance scenario in terms of time and effort, which can be achieved through effective in-vessel remote handling (RH) operations, simplified maintenance of the RH system itself, well-coordinated logistics, and trained personnel, etc. All these aspects need to be investigated during the design phases, which requires a well-defined concept of operation of the RH systems. This paper describes the concept of operation of the Agile Robot Transporter (ART), an ITER in-vessel RH system, that is under development to carry out neutron and optical diagnostic calibrations, and removal/replacement of the blanket first wall samples. Based on the functional analysis of the required in-vessel tasks, system requirements are defined. Among them, key requirements to improve RH operation efficiency are identified and the ART is designed accordingly. Efficient deployment and removal operations of the ART are crucial so that it requires less vacuum vessel (VV) port opening and less cask transportation, which reduces needs for hands-on operations resulting in less human radiation exposure. Various and flexible tool exchange and storage concepts are proposed that allow parallel operations between the in-vessel and ex-vessel RH systems. Modular and re-configurable design is proposed for easy RH system maintenance, and effective rescue operations to rescue the RH system when it fails.

Dust contamination of Divertor Remote Handling System in ITER Hot Cell: A novel approach to model complex superficial radiation sources

Activated dust produced by the erosion of plasma-facing components entails a significant radiation source for ITER and, generally, for all tokamaks aiming for operation under high neutron exposure. In-Vessel remote-handling operations will mobilise the dust, which will be deposited on the remote-handling tools used, for which hands-on maintenance is expected. To ensure safe maintenance of the remote-handling equipment, a dedicated decontamination process in the Hot Cell is required. Evaluating the radiation fields produced by the contaminated equipment is central to minimising radiation exposure to personnel. In this study, we present a nuclear analysis of the Divertor Remote Handling System during its transfer and decontamination process. Past computational limitations regarding superficial sources definition and high uncertainties on the dust model have been overcome by implementing a novel methodology and following an alternative approach. Two surface-dependent dust distributions over the complex geometry surfaces were considered to evaluate the dose rates according to the different contamination levels during the process phases. A scoping analysis was performed to determine the amount of dust that would comply with project requirements in each phase of the process. Improvement margins were identified in the quantification of the amount of dust and Hot Cell layout.

Concept design of automatic connector for maintenance cask of EU-DEMO and CFETR

For both CFETR and EU-DEMO remote handling system, maintenance casks are critical systems to provide storage and sealing functions. The maintenance devices and tools inside a cask receive power and signals during operation from the cask automatic connectors which are located at both sides of the Hot Cell Docking ports and the Tokamak machine Docking ports, respectively. For perfect transmission of power and signals, the automatic connector should have self-alignment capability and reasonable cable routing. Structural flexibility should be designed for the connector to compensate for the engagement misalignment induced by the structure and the control of the cask transporter. Moreover, the automatic connector should be connecting electric wires for motors, sensors, fiber optics, etc. The automatic connector must have high reliability to ensure that there will be no damage during the life cycle of the fusion reactor. A conceptual design of the connector has been developed. This will be presented together with prototype and validation works that are currently being implemented in close collaboration between European laboratories and the Comprehensive Research facility for Fusion Technology (CRAFT) at ASIPP in Hefei.

Design and experimental verification of an electro-hydraulic dual system with reliable resistance to γ-irradiation

Remote handling constitutes a critical technological facet in the domain of fusion reactors. However, exposure to γ rays inflicts irreversible deleterious effects on both electronic assemblies and structural materials. In the present investigation, we meticulously engineered an electro-hydraulic dual system tailored for remote handling applications within fusion reactors. Subsequently, the system was subjected to γ irradiation employing 60Co as the radioactive source. After exposure to a dose of 4 MGy, the electro-hydraulic dual joint system demonstrates sustained functional integrity. In contrast, isolated electric and hydraulic joints manifests minor oil seepage after exposure to a radiation dose of 5 MGy. Additionally, the effectiveness of the selected O-ring sealing material, ethylene propylene diene monomer (EPDM), exhibits a significant decrement upon irradiation to a dose of 1–3 MGy. The observed γ-radiation resilience is attributed to strategic material selection, specifically in the choice of O-ring, as well as metal reinforcement. The findings furnish valuable insights for the development of remote handling systems capable of operating under γ irradiation and strenuous mechanical conditions.

Remote maintenance scenario of the caesium ovens and beam source of the ITER heating neutral beam

Maintenance of the Heating Neutral Beam (HNB) injectors that are located in the ITER Neutral Beam (NB) cell needs Remote Handling (RH) operations because the NB cell is a radiation controlled area. This paper describes the remote maintenance sequences of the caesium ovens and the Beam Source (BS) of the ITER HNB by using the Neutral Beam Remote Handling System (NBRHS). Caesium oven maintenance is a regular maintenance that needs to be performed every Long-Term Maintenance (LTM) period as caesium is a consumable to produce caesium vapor to enhance negative ion production. The BS maintenance is a corrective maintenance to do if it fails during the lifetime of ITER. Maintenance of the caesium ovens and the BS involves many RH operations that require collaboration of the NBRHS subsystems and RH tools. Moreover, the maintenance operation needs to be done without spreading contamination from the HNB vessel to the NB cell. The developed maintenance scenario relies on the current NB cell environment and the existing interfaces in the plant system.

Design and implementation of distributed middleware for CRAFT remote handling system

The software system of remote handling control system (RHCS) for the comprehensive research facility for fusion technology (CRAFT) consists of multiple subsystems and various device controllers running on different hosts or servers. A high-performance CRAFT remote handling (RH) middleware (CRMW) is designed to address the high real-time requirements for task response and data transmission in this distributed scenario, as well as the scalability of the RHCS. CRMW adopts a low-coupling, high-cohesion, and component-based architectural design, comprising a component-based software development framework and a real-time communication port. The robot framework allows encapsulating devices or functional modules in the RHCS as reusable components, while the communication port provides low-latency and stable communication quality. It supports various communication modes such as publish/subscribe, server/client, and multiple transmission protocols, while also offering distributed components like remote procedure call (RPC). Corresponding experimental results demonstrate that CRMW can deliver low-latency and stable task response and data transmission, fully meeting the requirements for task execution and system management in the RHCS.

Research on the Dynamic Control Method of CFETR Multi-Purpose Overload Robot

The CFETR multi-purpose overload robot (CMOR) is a key subsystem of the remote handling system of the China fusion engineering test reactor (CFETR). This paper first establishes the kinematic and dynamic models of CMOR and analyzes the working process in the vacuum chamber. Based on the uncertainty of rigid-flexible coupling, a CMOR adaptive robust sliding mode controller (ARSMC) is designed based on the Hamilton-Jacobi equation to enhance the robustness of the control system. In addition, to compensate the influence of non-geometric factors on position accuracy, an error compensation method is designed. Based on the matrix differentiation method, the CMOR coupling parameter errors are decoupled, and then the gridded workspace principle is used to identify the parameter errors and improve the motion control accuracy. Finally, the CMOR rigid-flexible coupling simulation system is established by ADAMS-MATLAB/Simulink to analyze the dynamic control effect of ARSMC. The simulation results show that the CMOR end position error exceeds 0.1 m for single joint motion. The average value of CMOR end position error is less than 0.025 m after compensation, and the absolute error value is reduced by 4 times, improves the dynamic control accuracy of CMOR.

Preliminary architecture of the DTT remote handling test and training facility

The realization of a specific REMote HAndling Test and Training Facility (REMHAT) is necessary for the development and optimization of the Remote Handling (RH) system, to demonstrate the fulfilment of all its design requirements, for testing and validation of the RH maintenance procedures, for the qualification and acceptance testing of RH equipment and tooling. Furthermore, it provides training and certification to the RH maintenance operators, by making available to operators the knowledge, instructions and experiencing of the Virtual Simulator platform, the control room devices, the robots and tooling to be used for RH tasks. In this work, the preliminary architecture of the DTT REMHAT facility is described, with a focus on the added value of the adoption of Virtual Reality (VR) technologies enabling real-time alignment of virtual robots’ configuration with the real ones (Digital Twin). A first approach to the facility design is proposed, starting from the technical requirements: Environmental, Design, Physical, Functional, Operational, Human Factors and Product assurance and safety. The proposed logical architecture consists of four Sub-Systems (S/S): building and auxiliaries, mock-ups, robots and Control Room. In the present work, a particular attention is paid on the last one. The idea is to create a digital twin of the RH equipment mock-ups to be coupled with software of real-time structural simulation, in order to have at disposition and show in VR environment real-time additional information about the real environment, like robots’ deflections and/or vibrations, clearances and possible collisions detection. These data could be crucial for the operator’s decision-making process about a sudden intervention on the RH system, further to their employment for future studies and optimization. Therefore, for each subsystem of the facility, the components identification and a description of the software and hardware aspects are provided. In conclusion, an overview of the critical issues of such complex system is presented, in order to prepare the ground for future research works.

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.

ISOL module system for RAON ISOL facility

RAON (Rare Isotope Accelerator complex for ON-line experiments) heavy ion accelerator facility in Korea is preparing for producing rare isotopes using Isotope Separation On-line (ISOL) facility. Rare isotopes will be produced by a 70 MeV proton beam incident on the target system. Expecting the harsh radiation environment of the target area, the module system has been adopted. The module system in the ISOL facility consists of target ion source (TIS), rare isotope (RI) transport, and proton beam diagnostic modules. In order to handle and maintain the module system, the remote handling (RH) systems are developed and tested.

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.

The IFMIF-DONES remote handling control system: Experimental setup for OPC UA integration

The devices used to carry out Remote Handling (RH) manipulation tasks in radiation environments address requirements that are significantly different from common robotic and industrial systems due to the lack of repetitive operations and incompletely specified control actions. This imposes the need of control with human-in-the-loop operations. These RH systems are used on facilities such PRIDE, CERN, ESS, ITER or IFMIF-DONES, the reference used for this work.For the RH system is crucial to provide high availability, robustness against radiation, haptic devices for teleoperation and dexterous operation, and smooth coordination and integration with the centralized control room. To achieve this purpose is necessary to find the best approach towards a standard control framework capable of providing a standard set of functionalities, tools, interfaces, communications, and data formats to the different types of mechatronic devices that are usually considered for Remote Handling tasks. This previous phase of homogenization is not considered in most facilities, which leads towards a costly integration process during the commissioning phase of the facility.In this paper, an approach to the IFMIF-DONES RH Control framework with strong standard support based on protocols such as OPC UA has been described and validated through an experimental setup. This test bench includes a set of physical devices (PLC, conveyor belt and computers) and a set of OPC UA compatible software tools, configured and operable from any node of the University of Granada network. This proof-of-concept mockup provides flexibility to modify the dimension and complexity of the setup by using new virtual or physical devices connected to a unique backbone. Besides, it will be used to test different aspects such as control schemes, failure injection, network modeling, predictive maintenance studies, operator training on simulated/real scenarios, usability or ergonomics of the user interfaces before the deployment. In this contribution, the results are described and illustrated using a conveyor belt set-up, a small but representative reference used to validate the RH control concepts here proposed.

Design and research of CFETR peg hole assembly virtual platform

To fulfil in-vessel maintenance in the China Fusion Engineering Test Reactor (CFETR), a Master-Slave remote handling system with high reliability, stability, and flexibility is required. Due to the complexity of CFETR's internal environment and the robot system, operators need to be well trained before any physical maintenance is conducted. It is of high risk, high cost, and low efficiency that operators are trained in physical environment. The above problems can be avoided when operators are trained in a virtual environment. However, it is difficult to achieve the realization in the master side and contact force in the slave side. In this paper, we develop a new Virtual Assembly Simulation Platform with high quality realization of the contact force and the operator's telepresence. The platform consists of a master-slave robot system and a simulation environment build upon CoppeliaSim. To remove the influence of the tool's gravity on the feedback force obtained by the force sensor installed at the end of robot. We propose a least square method-based gravity compensation algorithm. The replaceability of the virtual platform to the physical platform and the effectiveness of the algorithm are demonstrated by the peg-in-hole assembly experiment.

Digital assistances in remote operations for ITER test blanket system replacement: An experimental validation

Removal/reinstallation of all Test Blanket System (TBS) equipment present in the Port Cell is required during the ITER Long Term Shutdown. TBS shall be designed so that occupational radiation exposure can be As Low As Reasonably Achievable (ALARA) over the life of the plant to follow the ITER Policy. The expected level of radiation in this area still allows performing maintenance tasks hands-on. However, the cumulated dose could be significant for operators. Classical Dose Reduction Measure (DRM) is to deploy Remote Handling systems. Consequently, use of robotized equipment, remotely operated means or collaborative robotics, have been investigated. Taking advantage of new digital technologies such as digital assistances, is expected to help operators during complex remote operations under limited vision conditions. Experiments were performed on a set of three TBS maintenance representative tasks: remote visual inspection of DN80 pipe, dye penetrant testing operation on pipe and dexterity test. A panel of remote handling equipment operators of different skill level was selected and involved onto these tasks. The results prove without ambiguity that for all operators the quality of the task execution is significantly improved when using digital assistances

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.