Divertor Test Platform Research Articles

Development of the remote handling connector for ITER divertor diagnostic system

Diagnostics is a vital system for ITER to collect information during operation. Mineral insulated cables route the electrical and optical diagnostics sensor signals from the divertor area to the diagnostic hall. The diagnostic divertor cassettes are replaced during maintenance, which raises the requirement for a connector between divertor cassette and in-vessel wall. Since it needs to be handled remotely during the installation of the 16 diagnostic divertor cassettes, it is called Remote Handling Connector. Its operating space is limited and its environmental conditions are ultra-high vacuum, baking temperature 350 °C, irradiation and challenging electromagnetic forces. The preliminary design of the Remote Handling Connector is based on the conceptual design of Outboard and Inboard Configurations and is highly impacted by finding an appropriate balance between the external and internal space limitations and system requirements. The design of the system has been an iterative process including several conceptual and mechanical design phases, thermal, magnetic and structural load analysis, risk analysis, and remote handling assessment. Mock-ups were manufactured and tested at Divertor Test Platform 2 and Remote Handling Connector Platform at VTT Tampere Finland. The developed system was evaluated at a preliminary design review meeting organized at the end of 2019. The preliminary design phase provides a baseline for the final design of the Remote Handling Connector system.

Divertor remote handling for DEMO: Concept design and preliminary FMECA studies

The paper describes a concept design of a remote handling (RH) system for replacing divertor cassettes and cooling pipes in future DEMO fusion power plant. In DEMO reactor design important considerations are the reactor availability and reliable maintenance operations. The proposed divertor mover is a hydraulic telescopic boom driven from the transportation cask through the maintenance tunnel of the reactor. The boom is divided in three sections and it is driving an end-effector in order to perform the scheduled operations of maintenance inside the vacuum vessel. Two alternative designs of the end effector to grip and manipulate the divertor cassette are presented in this work. Both concepts are hydraulically actuated, based on ITER previous studies. The divertor cassette end-effector consists of a lifting arm linked to the divertor mover, a tilting plate, a cantilever arm and a hook-plate. Taking advantage of the ITER RH background and experience, the proposed hydraulic RH system is compared with the rack and pinion system currently designed for ITER and is an object of simulations at Divertor Test Platform (DTP2) in VTT's Labs of Tampere, Finland. Pros and cons will be put in evidence.

Improving the performance of DTP2 bilateral teleoperation control system with haptic augmentation

The remote maintenance of the ITER divertor is largely dependent on the usage of haptically teleoperated manipulators and man-in-the-loop operations. These maintenance operations are very demanding for the manipulator operators, yet vital for the success of the whole ITER experiment. Haptic shared control of the maintenance manipulators offers a promising solution for assisting the teleoperators in the maintenance tasks. A shared control system assists the operator by generating artificial guiding force effects and overlaying them on top of the haptic feedback from the teleoperation environment.An experimental haptic shared control system, called the Computer Assisted Teleoperation (CAT) has been developed at the Divertor Test Platform 2 (DTP2). In this paper, we investigate the design of the system and how the system integrates with the ITER compliant DTP2 prototype Remote Handling Control System (RHCS). We also experimentally assess the effect of the guidance to the operator performance in an ITER-relevant maintenance scenario using the Water Hydraulic MANipulator (WHMAN), which is specially designed for the divertor maintenance. The result of the experiment gives suggestive indication that the CAT system improves the performance of the operators of the system.

Using a data-centric event-driven architecture approach in the integration of real-time systems at DTP2

Integration of heterogeneous and distributed systems is a challenging task, because they might be running on different platforms and written with different implementation languages by multiple organizations. Data-centricity and event-driven architecture (EDA) are concepts that help to implement versatile and well-scaling distributed systems.This paper focuses on the implementation of inter-subsystem communication in a prototype distributed remote handling control system developed at Divertor Test Platform 2 (DTP2). The control system consists of a variety of heterogeneous subsystems, including a client–server web application and hard real-time controllers. A standardized middleware solution (Data Distribution Services (DDS)) that supports a data-centric EDA approach is used to integrate the system.One of the greatest challenges in integrating a system with a data-centric EDA approach is in defining the global data space model. The selected middleware is currently only used for non-deterministic communication. For future application, we evaluated the performance of point-to-point communication with and without the presence of additional network load to ensure applicability to real-time systems. We found that, under certain limitations, the middleware can be used for soft real-time communication. Hard real-time use will require more validation with a more suitable environment.

An interactive design approach for nuclear fusion purposes: remote handling system for FAST divertor

The paper deals with the design issues concerning the remote maintenance of divertors in fusion advanced studies torus (FAST), a satellite tokamak acting as a test bed for the study and the develop of innovative technologies oriented to ITER and DEMO programs, pilot examples of the feasibility of energy production from nuclear fusion on the Earth. FAST remote handling (RH) solutions are provided according to an “interactive design review” philosophy based on virtual prototyping techniques. Assuming an ITER configuration as start point, it foresees an iterative process of design review, carried out in virtual reality (VR) environment and oriented to obtain a sort of best solution from the RH point of view. Any iteration includes the analysis of the current solution and the proposal of new and alternative ones, based on the requirements fulfillment and the improvement of critical points highlighted. In such a way, and this is the main novelty introduced by the paper, the interactive design review in a VR collaborative environment becomes the tool able to put in cooperation and in positive competition various and different competences, required by a multidisciplinary problem as the realization of nuclear fusion machine, in order to reach a shared solution. A first preliminary FAST RH solution is hereinafter presented, accompanied by the design of a compatible support system, due to the strict relationship between the divertor maintenance and the support configuration. The work was carried out via the collaboration of the “Divertor Test Platform 2” (DTP2) team, in charge of ITER divertor RH tests and located in VTT’s Labs of Tampere (Finland), and the IDEAinVR team of CREATE Consortium, with competence in interactive design and VR simulations and located in the Virtual Reality Lab of University of Naples Federico II (Italy).

Simulating and visualizing deflections of a remote handling mechanism

Continuing ITER divertor second cassette (SC) remote handling (RH) test campaign has been carried out at divertor test platform (DTP2) in Finland. One of the goals has been to develop and implement efficient algorithms and software tools for simulating and visualizing for the operator the non-instrumented deflections of the RH mechanisms under loading conditions.Based on assumptions of the classical beam theory, the presented solution suggests utilization of an infinitesimal transformation to represent elastic deflections in a mechanical structure. Both structural analysis and measurements of the real structure are utilised during the process. The solution suggests one possible implementation strategy of a software component called structural simulator (SS), which is a software component of the remote handling control system (RHCS) architectural model specified by ITER organisation.Utilisation of the proposed SS necessitates modification of the initial virtual reality (VR) model of RH equipment to a format, which can visually represent the structural deflections. In practise this means adding virtual joints into the model. This will improve the accuracy of the VR visualization and will ensure that the virtual representation of the RH equipment closely aligns with the actual RH equipment.Cassette multifunctional mover (CMM) and second cassette end effector (SCEE) carrying SC were selected to be the initial target system for developing the approach.Demonstrations proved that the approach used can give high levels of accuracy even in complex structures such as the CMM/SCEE: initial VR model accuracy of the CMM/SCEE carrying 9ton cassette improved from 80 to 5mm. Also, the deflection model is capable of adapting to changes in load at the end-effector: during the release/lift of the divertor 2nd cassette to/from the divertor rails the accuracy remains within 5mm.The algorithms and approach described are generic and can be adopted for other mechanisms.

Divertor cassette locking system remote handling trials with WHMAN at DTP2

A key ITER maintenance activity is the exchange of the divertor cassettes. The current major step in this programme involves the full scale physical test facility, namely divertor test platform 2 (DTP2), in Tampere, Finland. The objective of the DTP2 is the design and proof of concept studies of various remote handling (RH) device prototypes and their RH control systems, but is also important to define principles for standardizing control systems and methods around the ITER maintenance equipment.The development process of divertor cassette locking system (CLS) RH Tool prototypes is presented in this paper. The validation of the developed CLS Tool prototypes is accomplished in RH trials at DTP2. For this RH Trial, a CLS task description (TD) and tool prototypes were developed, manufactured and, finally, tested under remote operations. These tools, designed to be operated by water hydraulic manipulator (WHMAN), are water hydraulic jack (WHJ), pin tool (PT) and wrench tool (WT).

Interoperability of remote handling control system software modules at Divertor Test Platform 2 using middleware

This paper focuses on the inter-subsystem communication channels in a prototype distributed remote handling control system at Divertor Test Platform 2 (DTP2). The subsystems are responsible for specific tasks and, over the years, their development has been carried out using various platforms and programming languages. The communication channels between subsystems have different priorities, e.g. very high messaging rate and deterministic timing or high reliability in terms of individual messages.Generally, a control system's communication infrastructure should provide interoperability, scalability, performance and maintainability. An attractive approach to accomplish this is to use a standardized and proven middleware implementation. The selection of a middleware can have a major cost impact in future integration efforts.In this paper we present development done at DTP2 using the Object Management Group's (OMG) standard specification for Data Distribution Service (DDS) for ensuring communications interoperability. DDS has gained a stable foothold especially in the military field. It lacks a centralized broker, thereby avoiding a single-point-of-failure. It also includes an extensive set of Quality of Service (QoS) policies. The standard defines a platform- and programming language independent model and an interoperability wire protocol that enables DDS vendor interoperability, allowing software developers to avoid vendor lock-in situations.

Categorization of ITER remote handling operations

Remote handling operations are carried out by human operators working in the control room. In ITER, there are several different kinds of operations expected from fully automated operations to manually operated works. The amount of people performing the operations also varies from one operator and one supervisor to cooperation between different teams and several operators. For guiding the design and management of the operations, categories for similar operations can be defined. This paper describes a method of creating a categorization system for ITER remote handling operations. Six different categories are defined based on interaction complexity during the operations. Divertor Test Platform (DTP2) is presented as a case environment for validating this kind of categorization.

Concept design of the cassette toroidal mover

A full scale physical development and test facility, Divertor Test Platform 2 (DTP2), has been established in Finland for the purpose of demonstrating and developing the remote handling (RH) equipment designs for ITER using prototypes and virtual models. The major objective of the DTP2 environment is to verify and develop ITER divertor RH devices and operations. In practice this means various test trials and measurements of performance characteristics. This paper describes the design process of the Cassette Toroidal Mover (CTM). The main purpose of this design task was the development of the CTM concept. The goal of the design process was to achieve compatibility between CTM and the latest ITER divertor design. The design process was based on using a variety of tools, i.e. Catia V5, Delmia, Ansys, Mathcad and project management tools. Applicable European Standards were applied to the concept design. CTM is the cassette transporter, which carries divertor cassettes on the toroidal rails inside the ITER Vacuum Vessel (VV) during the divertor maintenance. The operation environment differs from a common industrial environment. Radiation level is 100 Gy/h. The temperature during RH operations can be 50 °C. Clearances are less than 20 mm and the loads carried weigh 9000 kg. These conditions require special solutions during the product development process. The design process consisted of defining and developing of the CTM operational sequence. This sequence includes the procedure of how the CTM – with it is onboard manipulator – prepares for and handles the divertor cassettes during RH operations. RH operations are essential part when defining CTM functions. High reliability is required in order to carry out RH tasks successfully. The recoverability of CTM is also an important design criteria. This paper describes the design process and the structure of the CTM concept.

Analysis of the new architecture proposal for the CMM control system

While developing divertor remote handling maintenance systems at the Divertor Test Platform 2 facility, some risks and sensitivity points related to the Cassette Multifunctional Mover control system software were discovered and evaluated. The control system architecture has to simultaneously fulfill the demanding ITER remote handling requirements and to face new requirements being uncovered during the trials. Especially evolving non-functional requirements such as reliability and safety have an effect on the control system architecture as it is getting more mature. An evaluation of the implications from architectural decisions is necessary before implementation efforts, as an architecture left to develop without evaluation may lead to a dead end and therefore soaring development costs. After studying existing architecture analysis methods an analysis method was developed to gain confidence to carry out the proposed changes.

DTP2 control room operator and remote handing operation designer responsibilities and information available to them

The purpose of the Divertor Test Platform 2 (DTP2) is to demonstrate the proof-of-concept level operations of ITER divertor maintenance devices, by remotely handling them from a dedicated control room. In order to verify safe and reliable remote handling (RH) maintenance operations, it is vital to repeat them equally every time. The operations shall be validated and restored beforehand by RH operation designers. During the actual operation the control room operators are following predefined operation sequences. After time passes, even the validated operation details will change and the sequences improve, but these changes should not be done during the actual operation. It is fundamental from safety perspective that the control room operator will not be able to make unintentional actions. Hence, during the operation the irrelevant information shall not be available to him. Also the software functionality available for other purposes than executing the operation shall be made invisible. Therefore, making careful user interface design is certainly relevant when designing control room sub-systems. In this paper, we introduce the current control room sub-systems used at the DTP2.We suggest utilizing user groups and user-centered design in the software development and implementation done in user group fashion is described.

Supervisory system for DTP2 remote handling operations

The purpose of the Divertor Test Platform 2 (DTP2) is to demonstrate the proof-of-concept level remote handling operations with ITER maintenance devices, from a dedicated control room. In order to remotely operate these devices safely, a supervisory system composed of several software sub-systems is needed. For each of the devices, a control system is embodied. In the control room, there is no direct visual contact to the operation area and therefore, a remote viewing system having radiation tolerant cameras is required. Should the camera feeds be unavailable or with limited visibility, a 3D visualization system is utilized for showing a virtual model of the scene. As the maintenance sequences are often complicated and subject to formal approval, having them well designed beforehand is mandatory. In this paper, we present the complete software and hardware solution designed and implemented for the DTP2 remote handling operations, already being used with the Water Hydraulic Manipulator (WHMAN) and Cassette Multifunctional Mover (CMM). We present the modular division of systems, each of them in smaller detail, and go through some of the design choices made during the platform evolution.

Results of CMM standalone tests at DTP2

A full scale physical test facility, DTP2 (Divertor Test Platform 2) has been established in Finland for demonstrating and refining the Remote Handling (RH) equipment designs for ITER. The first prototype RH equipment at DTP2 is the Cassette Multifunctional Mover (CMM) equipped with the Second Cassette End Effector (SCEE) delivered to DTP2 in October 2008. The purpose is to prove that CMM/SCEE prototype can be used successfully for the 2nd cassette RH operations. At the end of F4E grant “DTP2 test facility operation and upgrade preparation”, the RH operations of the 2nd cassette were successfully demonstrated to the representatives of Fusion for Energy (F4E). During the grant the High Level Control (HLC) software developed at DTP2 was integrated with the CMM/SCEE hardware. The performance criteria of the CMM/SCEE equipment were defined based on the ‘EN ISO 9283 Manipulating industrial robots – Performance criteria and related test methods’ standard. Considerable improvement to the performance was achieved with the aid of compensation functions, which took into account the deflections and the compliance effects caused by the Divertor Cassette weighting 9000 kg. According to measurements the positioning error at the furthest point of the cassette was reduced from 80 mm to 5 mm. So far the 2nd cassette mock-up has been installed and removed already some tens of times. The reliability of the HLC software is sufficient to operate the CMM/SCEE all day without interruptions. Also the execution of the automatic RH processes with the overall RH system is reliable and repeatable in terms of accuracy and cycle time. These experiments provide a solid basis for investigating the RH system ability to perform fail-safe operations in various failure scenarios and to recover from them. The target of the continuing R&D is to find out a more complete set of functional and non-functional requirements for the RH system for Divertor Cassette maintenance to ensure an adequate level of requirements and procedures for ITER.

Command and Control application framework for interoperable heterogeneous ITER Remote Handling devices

The ITER divertor Remote Handling maintenance concepts are under investigation at a full scale mockup facility, the Divertor Test Platform, located in Tampere, Finland. The key devices to carry out these operations are the (CMM), Cassette Toroidal Mover, Multi Axis Manipulators (MAM) and related tooling. Despite their differences, in essence all of these devices are manipulators with varying specifications. Hence, from the operator's point of view, they perform similar operations, such as following predefined position trajectories and lifting and carrying tools and equipment. This paper explores how to implement a software framework for a Command and Control application, otherwise known as Human Machine Interface (HMI), in such a way that it could be used to control different manipulators. A framework is presented that supports the combining of small, independent modules into a single cohesive HMI. It is then shown that a HMI can be built by combining modules that are common to these manipulators and modules that are specific to a single manipulator. This will not only minimize the programming effort but also reduce the training required of operators. To elaborate on the concept, an example HMI is implemented to control virtual models of CMM and MAM.

A method for enabling real-time structural deformation in remote handling control system by utilizing offline simulation results and 3D model morphing

A full scale physical test facility, DTP2 (Divertor Test Platform 2) has been established in Finland for demonstrating and refining the Remote Handling (RH) equipment designs for ITER. The first prototype RH equipment at DTP2 is the Cassette Multifunctional Mover (CMM) equipped with Second Cassette End Effector (SCEE) delivered to DTP2 in October 2008. The purpose is to prove that CMM/SCEE prototype can be used successfully for the 2nd cassette RH operations. At the end of F4E grant “DTP2 test facility operation and upgrade preparation”, the RH operations of the 2nd cassette were successfully demonstrated to the representatives of Fusion For Energy (F4E). Due to its design, the CMM/SCEE robot has relatively large mechanical flexibilities when the robot carries the nine-ton-weighting 2nd Cassette on the 3.6-m long lever. This leads into a poor absolute accuracy and into the situation where the 3D model, which is used in the control system, does not reflect the actual deformed state of the CMM/SCEE robot. To improve the accuracy, the new method has been developed in order to handle the flexibilities within the control system's virtual environment. The effect of the load on the CMM/SCEE has been measured and minimized in the load compensation model, which is implemented in the control system software. The proposed method accounts for the structural deformations of the robot in the control system through the 3D model morphing by utilizing the finite element method (FEM) analysis for morph targets. This resulted in a considerable improvement of the CMM/SCEE absolute accuracy and the adequacy of the 3D model, which is crucially important in the RH applications, where the visual information of the controlled device in the surrounding environment is limited.

Development and design optimization of water hydraulic manipulator for ITER

This paper describes one of the research projects carried out in The Preparation of Remote Handling Engineers for ITER (PREFIT) program within the European Fusion Training Scheme (EFTS). This research project is focusing on the design and optimization of water hydraulic manipulators used to test several remote handling tasks of ITER at Divertor Test Platform 2 (DTP2), Tampere, Finland, and later in ITER. In this project, a water hydraulic manipulator designed and build by Department of Intelligent Hydraulics and Automation in Tampere University of Technology, Finland (TUT/IHA) is further optimized as a case study for a given manipulator requirement specification in order to illustrate and verify developed comprehensive design guidelines and performance metrics. Without meaningful manipulator performance parameters, the evaluation of alternative robot manipulators designs remains ad hoc at best. Therefore, more comprehensive design guidelines and performance metrics are needed for comparing and improving different existing manipulators versus task requirements or for comparing different digital prototypes at early design phase of manipulators. In this paper the description of the project, its background and developments are presented and discussed.

Validation of Divertor Cassette locking system with a hydraulic jack tool

The divertor area of ITER vacuum vessel consists of 54 modular cassettes which must be exchanged after every 3–4 years of plasma operations. Divertor Cassettes are locked in the vacuum vessel by means of compressing them against the rails mounted in the inner and outer walls of the vacuum vessel. According to ITER reference cassette locking system, a Divertor Cassette has to be preloaded with a compression force of 360 kN against the vacuum vessel rails. The preloading of the cassettes is carried out with a hydraulic jack tool which is fitted into the cassette body. The Jack will transmit a hydraulic force by pushing the cassette latches against the outer rails, transmitting therefore the required preloading compression force to the cassette. This paper deals with the validation of Divertor Cassette locking system and it also describes the design and testing of a radiation-hard, water hydraulic jack. The validation of Divertor Cassette locking system has been the first Divertor Maintenance operation tested at Divertor Test Platform 2.

Optimized hardware design for the divertor remote handling control system

A key ITER maintenance activity is the exchange of the divertor cassettes. One of the major focuses of the EU Remote Handling (RH) programme has been the study and development of the remote handling equipment necessary for divertor exchange. The current major step in this programme involves the construction of a full scale physical test facility, namely DTP2 (Divertor Test Platform 2), in which to demonstrate and refine the RH equipment designs for ITER using prototypes. The major objective of the DTP2 project is the proof of concept studies of various RH devices, but is also important to define principles for standardizing control hardware and methods around the ITER maintenance equipment. This paper focuses on describing the control system hardware design optimization that is taking place at DTP2. Here there will be two RH movers, namely the Cassette Multifuctional Mover (CMM), Cassette Toroidal Mover (CTM) and assisting water hydraulic force feedback manipulators (WHMAN) located aboard each Mover. The idea here is to use common Real Time Operating Systems (RTOS), measurement and control IO-cards etc. for all maintenance devices and to standardize sensors and control components as much as possible. In this paper, new optimized DTP2 control system hardware design and some initial experimentation with the new DTP2 RH control system platform are presented. The proposed new approach is able to fulfil the functional requirements for both Mover and Manipulator control systems. Since the new control system hardware design has reduced architecture there are a number of benefits compared to the old approach. The simplified hardware solution enables the use of a single software development environment and a single communication protocol. This will result in easier maintainability of the software and hardware, less dependence on trained personnel, easier training of operators and hence reduced the development costs of ITER RH.

Water hydraulic manipulator for fail safe and fault tolerant remote handling operations at ITER

Department of Intelligent Hydraulics and Automation (IHA) of Tampere University of Technology has been involved in the European Fusion program since 1994 within the ITER reactor maintenance activities. In this paper we discuss the design and development of a six degrees of freedom water hydraulic manipulator with a force feedback for teleoperation tasks. The manipulator is planned to be delivered to Divertor Test Platform 2 (DTP2) during year 2008. The paper also discusses the possibility to improve the fail safe and redundant operation of the manipulator. During the design of the water hydraulic manipulator, special provisions have been made in order to meet the safety requirements such as servo valve block for redundant operation and safety vane brakes for fail safe operation.