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In order to detect special nuclear materials and other radioactive materials in Security and Defense scenarios, normally, a combination of neutron and gamma-ray detection systems is used. In particular, to avoid illicit traffic of special nuclear materials and radioactive sources/materials, radiation portal monitors are placed at seaports to inspect shipping-container cargo. Despite their large volume (high efficiency), these detection systems are expensive, and therefore only a fraction of these containers are inspected. In this work, a novel mobile radiation detection system is presented, based on an EJ-200 plastic scintillator for the detection of gamma rays and beta particles, and a neutron detector EJ-426HD plastic scintillator (with 6Li) embedded in a compact and modular moderator. The use of silicon photomultipliers in both detectors presented advantages such as lightweight, compactness, and low power consumption. The developed detection system was integrated in a highly maneuverable multirotor. Monte Carlo simulations were validated by laboratory measurements and field tests were performed using real gamma-ray and neutron sources. The detection and localization within one meter was achieved using a maximum likelihood estimation algorithm for 137Cs sources (4 MBq), as well as the detection of 241Am–beryllium (1.45 GBq) source placed inside the shipping container.

This paper describes the implementation of a multipurpose, autonomous, mobile manipulator for building outdoor structures and for firefighting. Such a system finds applications in different industrial automation, manufacturing, and civil-construction scenarios as well as in search-and-rescue operations. This system was developed for the Mohamed Bin Zayed International Robotics Challenge (MBZIRC) 2020, showcasing once again the role of major scientific competitions in advancing the state of the art and exploring solutions to open problems. The paper presents in detail the hardware and software architectures of the developed mobile manipulator, while proposing methods for: a) Building outdoor structures consisting of heterogeneous brick patterns, and b) Entering buildings to locate and extinguish fires. Solutions were successfully deployed in the near-realistic arenas of the MBZIRC 2020 competition and resulted in the first-place award for the firefighting scenario.

One of the main challenges in the development of a plasma diagnostic and control system for DEMO is the need to cope with unprecedented radiation levels in a tokamak during long operation periods. A list of diagnostics required for plasma control has been developed during the pre-conceptual design phase. Different approaches are proposed for the integration of these diagnostics in DEMO: in equatorial and upper ports, in the divertor cassette, on the inner and outer surfaces of the vacuum vessel and in diagnostic slim cassettes, a modular approach developed for diagnostics requiring access to the plasma from several poloidal positions. According to each integration approach, diagnostics will be exposed to different radiation levels, with a considerable impact on their design. This paper provides a broad overview of the radiation environment that diagnostics in DEMO are expected to face. Using the water-cooled lithium lead blanket configuration as a reference, neutronics simulations were performed for pre-conceptual designs of in-vessel, ex-vessel and equatorial port diagnostics representative of each integration approach. Flux and nuclear load calculations are provided for several sub-systems, along with estimations of radiation streaming to the ex-vessel for alternative design configurations. The results can be used as a reference by diagnostic designers.

Providing energy from fusion and finding ways to scale up the fusion process to commercial proportions in an efficient, economical, and environmentally benign way is one of the grand challenges for engineering. Controlling the burning plasma in real-time is one of the critical issues that need to be addressed. Plasma Position Reflectometry (PPR) is expected to have an important role in next-generation fusion machines, such as DEMO, as a diagnostic to monitor the position and shape of the plasma continuously, complementing magnetic diagnostics. The reflectometry diagnostic uses radar science methods in the microwave and millimetre wave frequency ranges and is envisaged to measure the radial edge density profile at several poloidal angles providing data for the feedback control of the plasma position and shape. While significant steps have already been given to accomplish that goal, with proof of concept tested first in ASDEX-Upgrade and afterward in COMPASS, important, ground-breaking work is still ongoing. The Divertor Test Tokamak (DTT) facility presents itself as the appropriate future fusion device to implement, develop, and test a PPR system, thus contributing to building a knowledge database in plasma position reflectometry required for its application in DEMO. At DEMO, the PPR diagnostic’s in-vessel antennas and waveguides, as well as the magnetic diagnostics, may be exposed to neutron irradiation fluences 5 to 50 times greater than those experienced by ITER. In the event of failure of either the magnetic or microwave diagnostics, the equilibrium control of the DEMO plasma may be jeopardized. It is, therefore, imperative to ensure that these systems are designed in such a way that they can be replaced if necessary. To perform reflectometry measurements at the 16 envisaged poloidal locations in DEMO, plasma-facing antennas and waveguides are needed to route the microwaves between the plasma through the DEMO upper ports (UPs) to the diagnostic hall. The main integration approach for this diagnostic is to incorporate these groups of antennas and waveguides into a diagnostics slim cassette (DSC), which is a dedicated complete poloidal segment specifically designed to be integrated with the water-cooled lithium lead (WCLL) breeding blanket system. This contribution presents the multiple engineering and physics challenges addressed while designing reflectometry diagnostics using radio science techniques. Namely, short-range dedicated radars for plasma position and shape control in future fusion experiments, the advances enabled by the designs for ITER and DEMO, and the future perspectives. One key development is in electronics, aiming at an advanced compact coherent fast frequency sweeping RF back-end [23–100 GHz in few μs] that is being developed at IPFN-IST using commercial Monolithic Microwave Integrated Circuits (MMIC). The compactness of this back-end design is crucial for the successful integration of many measurement channels in the reduced space available in future fusion machines. Prototype tests of these devices are foreseen to be performed in current nuclear fusion machines.

The detection of radioactive hot-spots and the identification of the radionuclides present have been a challenge for the security sector, especially in situations involving chemical, biological, radiological, nuclear and explosive threats, as well as naturally occurring radioactive materials. This work proposes a solution based on Machine Learning techniques, with a focus on artificial neural networks (NNs), in order to localise, quantify and identify radioactive sources. Firstly, the created RHLnet model uses observations of radiological intensity counts and corresponding localisations to estimate the number, location and activity of unknown radioactive sources present in a given scenario. Then, another model (RHIdnet) gets the gamma spectrum of the sources to perform the identification of the corresponding radionuclides. For this, a training data set composed of simulated data is used during the training process, and so, using algorithms with the models already trained, fast and accurate predictions are achieved, ensuring the reliability of such a NN-based approach. The proposed solution is tested in simulated and real scenarios, with multiple sources, providing a low number of limitations, related to possible false negatives and false positives. Besides, the results have shown that the algorithm is scalable for very large regions, as well as for very small scenarios. Single and multiple isotope identification on each sample is explored, highlighting the benefits as well as possible improvements. Thus, NNs have demonstrated the capability of being an emerging tool with the potential to make a difference in the nuclear field, by helping in the development of novel techniques and new solutions in order to safeguard human lives.

The quality control of structures and fuselages in both the wind-turbine and solar sectors is a fundamental part that allows a lifetime assessment of their elements, from its initial assembly to the recurring inspection cycles. Automating the active thermography on this scale, cannot be achieved with conventional industrial robots. Unmanned vehicles, such UAVs and UGVs, present distinctive advantages that should certainly be exploited, but, its inherent static motion is one of the main stumbling blocks towards its use in an active thermography inspection. In this paper, a two-step digital stabilization scheme has demonstrated its efficacy in real defects located in both a wind blade and solar panel. The combination of a featurebased registration algorithm and a dense parametric optical flow direct alignment has enabled the pseudo-static reconstruction of the thermograms. The adopted experimental methodology, employing a robot with both halogens and IR camera, subjected to random motions with varying speed and amplitudes, has allowed a direct repeatable comparison of static and stabilized phase images. The phase image contrast comparison of both static and dynamic tests, have been carried out on a flat bottom hole (FBH) wind blade GFRP sample, showing nearly identical phase contrast with marginal differences. Likewise, a real GFRP wind-blade impact delamination defect has also reached a close phase contrast regarding its counterpart, albeit with a decreased contrast. Additionally, the registration algorithm has been used to stitch the individual frames, derived from a dynamic recording of an electroluminescent solar panel, to allow for a unified detection and mapping of defects.

Human populations and natural ecosystems are bound to be exposed to ionizing radiation from the deposition of artificial radionuclides resulting from nuclear accidents, nuclear devices or radiological dispersive devices (“dirty bombs”). On the other hand, Naturally Occurring Radioactive Material industries such as phosphate production or uranium mining, contribute to the on site storage of residuals with enhanced concentrations of natural radionuclides. Therefore, in the context of the European agreements concerning nuclear energy, namely the European Atomic Energy Community Treaty, monitoring is an essential feature of the environmental radiological surveillance. In this work, we obtain 3D maps from outdoor scenarios, and complete such maps with measured radiation levels and with its radionuclide signature. In such scenarios, we face challenges such as unknown and rough terrain, limited number of sampled locations and the need for different sensors and therefore different tasks. We propose a radiological solution for scouting, monitoring and inspecting an area of interest, using a fleet of drones and a controlling ground station. First, we scout an area with a Light Detection and Ranging sensor onboard a drone to accurately 3D-map the area. Then, we monitor that area with a Geiger–Müller Counter at a low-vertical distance from the ground to produce a radiological (heat)map that is overlaid on the 3D map of the scenario. Next, we identify the hotspots of radiation, and inspect them in detail using a drone by landing on them, to reveal its radionuclide signature using a Cadmium–Zinc–Telluride detector. We present the algorithms used to implement such tasks both at the ground station and on the drones. The three mission phases were validated using actual experiments in three different outdoor scenarios. We conclude that drones can not only perform the mission efficiently, but in general they are faster and as reliable as personnel on the ground.

This paper presents the initial conceptual study of integration of reflectometry antennas and waveguides (WGs) in DEMO. The antennas are located at several poloidal angular positions covering a full poloidal section of the helium-cooled lithium lead breading blanket. The concept of slim cassette (SC) is presented which allows for possible side attachment to the blanket sector and offers compatibility with remote handling (RH) operations. The proposed concepts for WGs sectors relative motion decoupling, vacuum boundary breaking, and RH are presented. Monte Carlo neutronic simulations have been done in order to evaluate the heat loads and shielding capabilities of the system. The first results indicate that the cooling for the EUROFER diagnostic components (antennas and WGs) can in principle be provided by the blanket cooling services (He is considered) via connection to the main back supporting structure and routed via the main diagnostic structure body. The first results on the SC thermal analysis indicate that for the first wall (FW), an increase of He speed is required (or a higher cooling volume) as temperatures are above blanket FW temperature. As for the inner components (shielding and wave guides), the cooling requires localized optimization (hot spots in module corners and front antennas) but respects average temperature limit requirements.

Sensor technologies will play a key role in the success of Remote Maintenance (RM) systems for future fusion reactors. In this paper, three key types of sensor technologies of particular interest in the robotics field at the moment are evaluated, namely: Colour-Depth cameras, LIDAR (Light Detection And Ranging), and Millimetre-Wave (mmWave) RADAR. The evaluation of the sensors is performed based on the following criteria: the types of data they provide, the accuracy at different distances, and the potential environmental resistance of the sensor (namely gamma radiation). The authors review the progress in making these three types of sensor capable of operating in Fusion facilities and discuss possible mitigations. Experiments are performed to demonstrate the pros and cons of each type of sensor by collecting data from radar, colour-depth camera and LIDAR, simultaneously. The paper concludes with a performance comparison between sensors, as well as discussing the possibility of combining them, fostering redundancy in case of failure of any individual sensor device.

The Diagnostics Slim Cassette (DSC) is a concept currently proposed for DEMO to host the microwave reflectometry diagnostic in a dedicated poloidal section, for the feedback control of plasma position and shape, providing also the radial edge density profile at several poloidal angles. This DSC, which is expected to house up to ∼100 antennas and waveguides, is to be integrated with the Breeding Blanket (BB) segments. Moreover, it is being designed with Remote Handling compatibility in mind to facilitate a "fast" exchange by Remote Maintenance (RM) when needed, fulfilling one of the aims of the Work Package Diagnostic and Control. In this approach the pre-assembled (banana-shaped) DSC modules are inserted/removed from the Upper Port (UP) of the Vacuum Vessel (VV) at least when the BB segments are replaced. Here the main constraints related to the integration of the DSC with the BB, the UP and the Equatorial Port are identified and discussed in detail, with a strong focus on the required RM operations inside the VV (in-vessel), providing solutions that can be adapted to present and future blanket and UP designs.

ITER is an experimental tokamak nuclear fusion reactor with the goal of achieving afusion energy gain factor of 10. Nuclear fusion presents an extreme environment for materials during operations while requiring continuous uninterrupted operation. The Reliability Block Diagram (RBD) is a graphic methodology for system reliability modelling which is constructed from the reliability-wise relations between different subsystems/components and their respective reliability and maintenance data. In this paper, we construct andanalyse the RBD for the Collective Thomson Scattering (CTS) front-end both in terms of fulfilling its functions and its effects in the ITER tokamak operations. Our RDB analysis results were then used to propose mitigation actions which include design changes and operational procedures to deal with the identified failure modes. Our initial results indicate that the system's mean availability at the end of its lifecycle of 20 years is no greater than 82.55% which was due to low Mean Time Between Failures (MTBF) of a critical system component – theSplit Biased Waveguide (SBWG) – aswell as several thermally loaded components. After mitigation actions, which aimed at controlling the system's exposure to heat loads, the MTBFs increased and the resulting mean availability achieved values over 97%, in conformity with design specifications. Furthermore, considering the CTS failure modes with impact on ITER operations, the expected value for the mean availability is of 99.995%. Therefore, we concluded that these failure modes did not require mitigation actions. In this article, we cover the second half of the RAMI analysis of the CTS diagnostic, the RBD analysis.

ITER is a tokamak nuclear fusion reactor intended to demonstrate the feasibility of nuclear fusion as a carbon-free energy source. In order to control potential technical risks, ITER subsystems are assessed through Reliability, Availability, Maintainability and Inspectability (RAMI) analysis, which includes Failure Modes Effects and Criticality Analysis (FMECA). This paper deals with the FMECA of the front-end components of the Collective Thomson Scattering (CTS) diagnostic, which involves a top-down functional breakdown of the system, identification of critical components and potential failure modes, their effects and consequences for the system. Furthermore, the FMECA methodology allows for the analysis of possible mitigation actions, which may reduce failure mode risk levels. The FMECA was performed in two stages, one concerning the failure modes of the CTS itself, and one concerning the failure modes, which may interrupt ITER operations. Results indicate that there are no failure modes that pose a significant risk to ITER operations. However, mitigation actions were required in order to reduce the risk levels of failure modes, which may compromise CTS diagnostics availability. This article covers the first half of the RAMI analysis of the CTS diagnostic, the FMECA.

Remote Handling Systems (RHS) are specially designed for regular operations inside and outside of the nuclear reactors for inspection and maintenance. The reactor is shutdown during the installation and operation of the RHS, which is time-consuming and expensive. Unmanned Aerial Vehicles (UAVs) are a possible solution to perform inspection missions inside the reactor before the RHS operations. This work presents possible applications of UAVs to perform inspection missions inside the reactor during its shutdown. Such UAVs are able to transport different on-board sensors to get an insight view of the blankets and other elements inside the reactor, while providing the maneuverability and endurance to perform the inspection missions. The same approach can also be used for inspection of contaminated areas, such as the fission reactors for leakage detection, storage areas of nuclear sources, or even in hazardous scenarios of nuclear disasters. The costs of producing, maintaining and operating UAVs are expected to be low when compared to the time and costs that can be saved with the valuable information acquired during the flight.

In DEMO, the ex-vessel Remote Maintenance Systems (RMS) are responsible for the replacement and transportation of the plasma facing components. The ex-vessel operations of transportation (e.g. blankets or divertors) are performed by cranes or by means of trolleys. The blankets are extracted and transported vertically by cranes along galleries from the reactor to the storage or maintenance areas. An alternative is the transportation in horizontal configuration by means of trolleys along the galleries. A failure may occur in any situation, interrupting the current nominal operation. The work identifies a functional breakdown structure for the ex-vessel RMS operations and develops a Functional Failure Modes, Effects and Criticality Analysis (FFMECA). The results of the different FFMECA studies lead to the conclusions in terms of the most critical failure scenarios and the pros and cons of the horizontal versus the vertical transportation of blankets. In case of failure, a recovery procedure shall be triggered. The results will help the design process to improve and thus reduce the criticality index of the identified failures.

Nuclear fusion power plants require periodical maintenance, including the remote handling operations of transportation performed by automated guided vehicles (AGV). The navigation system becomes a key issue given the safety constrains of the heavy load to be transported in the complex scenarios, such as the reactor building. This work presents well-known and mature navigation technologies used by AGV in industry: with a physical path (e.g., wire/inductive guidance, optical line guidance and magnetic tape guidance) and with a virtual path (e.g., laser based, motion capture, inertial, magnetic-gyro) to be followed by the AGV during the operations of transportation. A critical assessment is also presented regarding the performance of these technologies against the operational requirements and safety demonstration in the framework of fusion facilities like ITER (International Thermonuclear Experimental Reactor) or DEMO (DEMOnstration Power Station).

The paper presents a study to design and implement a multi-copter with ducted propellers to perform radiological inspections, i.e., near to the radioactive sources and with the best flight time. It must operate in confined spaces or outdoor scenarios and be resilient to collisions. The design is optimized according to the number of rotors and components available in the market. A best combination is implemented and tested in laboratory and in a real outdoor scenarios. The improvements related to ducted propellers are evaluated and reported.

The risk toward human lives in situations involving chemical, biological, radiological, and nuclear (CBRN) threats can be mitigated or even neutralized by deploying carrying a suite of suitable sensors. Furthermore, mobile robots open up the possibility for automated radiological field surveys and monitoring operations, which have important applications in scenarios with CBRN threats. A path planner is one of the essential tools required for these robots to perform their tasks autonomously. Moreover, sophisticated path planners can greatly increase the efficiency of monitoring tasks by maximizing the information gathered in the minimum amount of time. This work proposes an informative path planner as an instrument to efficiently estimate maps of scalar quantities (e.g., radiation intensity, chemical concentration), motivated by applications in radiological inspection. The proposed path planner models the path with B-splines, enabling planning in continuous space. A Gaussian Process with a squared exponential kernel is used to model the underlying field. A modified form of mutual information, estimated from the Gaussian Process, is maximized to determine the most informative path, additionally rewarding observations made in regions where the field magnitude is large (e.g., near a radioactive source). A maximum likelihood estimator for source parameters is used to demonstrate that the proposed solution increases the accuracy of the estimated source positions. Simulation results show that the informative path planner adapts to non-convex environments and increases the number of observations made close to radioactive sources while avoiding obstacles.

In nuclear facilities, such as the experimental fusion reactor ITER, the cargo transfer operations can be performed by autonomous guided vehicles under remote supervision. In ITER, these vehicles can reach up to 100 tons and, with a rhombic-like configuration, have to move in cluttered scenarios. In case of failure, the vehicles have to be manually guided. This paper presents three solutions for the teleoperation of rhombic-like vehicles. Two set of devices were used to test each solution: one is based on a gamepad and the other is based on a joystick with a rotational disc specially designed for this purpose. The solutions were experimented by the developer and by 12 users without prior experience on rhombic-like vehicles. The experiments were performed in a software simulator that provides 2D maps of the test facility and simulates the kinematics of the vehicles in real time. The main conclusions are reported.

The remote handling (RH) plays an important role in nuclear test facilities, such as in ITER, for in-vessel and ex-vessel maintenance operations. Unexpected situations may occur when RH devices fail. Since no human being is allowed during the RH operations, a Multi-purpose Rescue Vehicle (MPRV) must be required for providing support in site. This paper proposes a design of a MPRV, i.e., a mobile platform equipped with different sensors and two manipulators with different sets of end-effectors. A human–machine interface is also proposed to remotely operate the MPRV and to carry out rescue and recovery operations.

DEMO is a proposed nuclear fusion power plant intended to demonstrate the generation of electrical power and to build upon the expected success of the ITER experimental nuclear fusion reactor. The remote maintenance system is provided to perform the remote maintenance of DEMO components. The ex-vessel transportation is one of the top level maintenance functions. This paper describes a proposal for the ex-vessel transfer cask in DEMO, taking into account the best outcomes achieved with the design used in ITER, but with upgrades in some features. In particular with the inclusion of a trolley, which provides the motion capabilities. The design of the trolley is also presented in the paper. The main conclusions are reported including the open issues.

Operations of transportation in cluttered environments require robust motion planning algorithms. Specially with large and heavy vehicles under hazardous operations of maintenance, such as in the ITER, an international nuclear fusion research project. The load transportation inside the ITER facilities require smooth and optimized paths with safety margin of 30 cm. The transportation is accomplished by large rhombic-like vehicles to exploit its kinematic capabilities. This paper presents the performance analysis of a motion planning algorithm to optimize trajectories in terms of clearance, smoothness and execution time in cluttered scenarios. The algorithm is an upgraded version of a previous one used in ITER, replacing the initialization implemented using Constrained Delaunay Triangulation by the Fast Marching Square. Exhaustive simulated experiments have been carried out in different levels of ITER buildings, comparing the performance of the algorithm using different metrics. Path planning in International Thermonuclear Experimental Reactor (ITER) is studied.Fast marching-based path initialization provides high smoothness and clearance paths.Path length and obstacle clearance are improved with an optimization procedure.Path smoothness is decreased only the necessary to satisfy the requirements.Final paths are optimal, smooth and collision-free, demanded ITER scenarios.

The Cask and Plug Remote Handling System (CPRHS) is one of the remote handling systems that will operate in the International Thermonuclear Experimental Reactor (ITER), transporting heavy and highly activated in-vessel components between the Tokamak Building and the Hot Cell Building, the two main buildings of the nuclear facility. The CPRHS has similar dimensions as an autobus, maximum weight of 100 tons, with kinematics of a rhombic-like vehicle (two drivable and steerable wheels) and has to move in cluttered environments. Two main approaches for trajectory optimization were developed and implemented aiming at providing smooth paths that maximize the clearance to obstacles taking into account the flexibility of rhombic-like vehicles: line guidance (same path for both wheels) and free roaming (different paths for each wheel). The line guidance approach includes maneuvers when necessary and the ability of maximizing the common parts of different paths used in the most of the nominal operations. Free roaming is mainly used when line guidance is not possible, namely in rescue operations. Both approaches were implemented in a standalone application that receives 2D CAD models of the buildings and returns the best trajectories, including a report of the most risky points of collision and the swept volume of the vehicle along the missions. This paper also presents the main results of these approaches applied in the models of the real scenarios, crucial to proceed with the construction of the Tokamak Building. Conclusions and future work are presented and discussed. Path planning for mobile robots in cluttered environments with high safety constrains as in nuclear facilities like ITER.Line guidance and free roaming path planning methodologies for vehicles with rhombic-like kinematics.Integration of multiple maneuvers in path planning.Methodology that maximizes the common parts of different trajectories.

In this paper we present the results of the R&D work that has been performed on avoiding electron cyclotron (EC) gas breakdown inside the launcher transmission line (TL) of the ITER collective Thomson scattering (CTS) diagnostic, due to encountering the fundamental EC resonance, which is located inside the port plug vacuum for the baseline ITER magnetic field scenario. If an EC breakdown occurs, this can lead to strong local absorption of the CTS gyrotron beam, as well as arcing inside the ITER vacuum vessel, which must be avoided. Due to the hostile, restrictive, and nuclear environment in ITER, it is not possible to implement the standard method for avoiding EC breakdown - a controlled atmosphere at the EC resonance. Instead, the CTS diagnostic will include a longitudinally-split electrically-biased corrugated waveguide (SBWG) in the launcher transmission line. The SBWG works by applying a transverse DC bias voltage across the two electrically-isolated waveguide halves, causing free electrons to diffuse out of the EC resonant region before they can cause an electron-impact ionisation-avalanche, and thus an EC breakdown. Due to insufficient experimental facilities, the functionality of the SBWG is validated through Monte Carlo electron modelling.

The cask and plug remote handling system (CPRHS) provides the means for the remote transfer of in-vessel components and remote handling equipment between the Hot Cell building and the Tokamak building in ITER. Different CPRHS typologies will be autonomously guided following predefined trajectories. Therefore, the localization of any CPRHS in operation must be continuously known in real time to provide the feedback for the control system and also for the human supervision. This paper proposes a localization system that uses the video streaming captured by the multiple cameras already installed in the ITER scenario to estimate with precision the position and the orientation of any CPRHS. In addition, an augmented reality system can be implemented using the same video streaming and the libraries for the localization system. The proposed localization system was tested in a mock-up scenario with a scale 1:25 of the divertor level of Tokamak building.

The Cask and Plug Remote Handling System (CPRHS) provides the means for the remote transfer of in-vessel components and remote handling equipment between the Hot Cell Building and the Tokamak Building in ITER along pre-defined optimized trajectories. A first approach for CPRHS path optimization was previously proposed using line guidance as the navigation methodology to be adopted. This approach might not lead to feasible paths in new situations not considered during the previous work, as rescue operations. This paper addresses this problem by presenting a complementary approach for path optimization inspired in rigid body dynamics that takes full advantage of the rhombic like kinematics of the CPRHS. It also presents a methodology that maximizes the common parts of different trajectories in the same level of ITER buildings. The results gathered from 500 optimized trajectories are summarized. Conclusions and open issues are presented and discussed.

During operation, maintenance inside the reactor building at ITER (International Thermonuclear Experimental Reactor) has to be performed by remote handling, due to the presence of activated materials. Maintenance operations involve the transportation and storage of large, heavyweight casks from and to the tokamak building. The transportation is carried out by autonomous vehicles that lift and move beneath these casks. The storage of these casks face several challenges, since (1) the cask storage area is limited in space, and (2) all casks have to be accessible for transportation by the vehicles. In particular, casks in the storage area may block other casks, so that the former has to be moved to a temporary position to give way to the latter. This paper addresses the challenge of managing the logistics of cask storage, where casks may have different typologies. In particular, we propose an approach to (1) determine the best position of the casks inside the storage area, and to (2) obtain the sequence of operations required to retrieve and store an arbitrary cask from/to a given storage place. A combinatorial optimization approach is used to obtain solutions to both these problems. Simulation results illustrate the application of the proposed method to a simple scenario.

Most mobile vehicle localization approaches rely on onboard sensors. However, whenever the installation of sensors onboard the vehicle is unfeasible, an alternative solution is to install them in the environment. One such environment is the ITER nuclear fusion reactor, where all maintenance operations have to be performed by remote handling, due to the radiation levels. This paper addresses the problem of vehicle localization in a structured environment, using a network of laser range nder sensors. The approach taken is based on: (1) the optimization of the sensor placement in the environment, aiming at the maximization of the area covered by the sensors and the redundancy of the sensor network, and (2) a probabilistic approach for vehicle localization. Two localization methods were evaluated: Extended Kalman Filter and Particle Filter. These two methods are compared, with respect to localization performance and robustness, both in simulation and using a real vehicle in a mock-up scenario.

The transfer cask system (TCS) is one of the remote handling systems that will operate in ITER, transporting heavy and highly activated in-vessel components between the tokamak building and the hot cell building. A motion planning methodology for the TCS was developed, providing smooth paths that maximize the clearance to obstacles and that incorporate manoeuvres whenever necessary. This paper presents the results of the TCS planning algorithm with trajectories computed for nominal operations. The length of the journey, the velocity, the time duration, and the risk of collision were evaluated individually for each trajectory. A summary of all results, conclusions and future work are presented and discussed.

The Remote Handling tasks scheduled during the ITER maintenance shutdown require transportation of in-vessel components from the Vacuum Vessel ports, at all levels of the Tokamak building, to the docking stations in the Hot Cell building. This transfer of radioactive, contaminated components represents a task of unprecedented complexity for a nuclear device like ITER. A Transfer Cask System (TCS) has been adopted as a reference solution. The TCS is a mobile, leak-tight unit, which can be divided into: (1) the cask itself, i.e., the container for the components to be transferred, able to avoid spread of contamination outside its envelope, equipped with in-cask handling devices; (2) the interface pallet that assists the docking operations of the cask and, underneath; (3) an Air Transfer System (ATS), i.e., a mobile platform floating on air-cushions with drive and steering wheels powered by electric motors and batteries on-board. The system will be remotely controlled, moving along previously defined paths. This paper focuses on the present status of the ATS design, the issues to be faced and the future developments foreseen.

This document states a method to optimize the coverage of a range finder multisensor network on an indoor environment. The problem arose from the need of a localization system for autonomous mobile robots, integrated with the building. The common approach for a localization system consists on sensors in the vehicle itself. In this case the vehicle is only an actuator and the sensory part is installed on the building. The localization system performance depends on the sensor placement, to enhance it, the sensor network must maximize the covered area. To solve the problem, an algorithm that maximizes the coverage areas is proposed. Given a scenario map, obtains the optimal coverage area multisensor placement. This paper presents also some results and proposals to future approaches to the problem.

In the thermonuclear experimental reactor ITER, a vehicle named CTS is designed to transport a container with activated components inside the buildings. In nominal operations, the CTS is autonomously guided under supervision. However, in some unexpected situations, such as in rescue and recovery operations, the autonomous mode must be overridden and the CTS must be remotely guided by an operator. The CTS is a rhombic-like vehicle, with two drivable and steerable wheels along its longitudinal axis, providing omni-directional capabilities. The rhombic kinematics correspond to four control variables, which are difficult to manage in manual mode operation. This paper proposes a Human Machine Interface (HMI) to remotely guide the vehicle in manual mode. The proposed solution is implemented using a HMI with an encoder connected to a micro-controller and an analog 2-axis joystick. Experimental results were obtained comparing the proposed solution with other controller devices in different scenarios and using a software plataform that simulates the kinematics and dynamics of the vehicle.

Remote maintenance operations in the experimental fusion reactor ITER may require vehicle localization, for which one of the proposed methods is based on a network of Laser Range Finder sensor measurements. This localization method requires an accurate knowledge of each sensor pose (position and orientation). A deviation in sensor pose can compromise localization accuracy thereby recalibration procedure for the sensor poses is often necessary. This paper studies several calibration algorithms based on ICP. Simulation and experimental tests were carried out for different maps and situations regarding sensor pose uncertainty. The conclusion proposes the best suited algorithms for each scenario.

The International Thermonuclear Experimental Reactor (ITER) project is a worldwide research experiment that aims to explore nuclear fusion as a viable source of energy for the coming years. Mobile robotics plays an important role in the remote handling systems that perform the maintenance operations in ITER. The Cask and Plug Remote Handling System (CPRHS) is one of the remote handling systems that transports heavy and highly activated in-vessel components between the Tokamak Building and the Hot Cell Building, the two main buildings of the ITER facility. The CPRHS has dimensions similar to an autobus, maximum weight of 100 tons, kinematics of a rhombic like vehicle (two drivable and steerable wheels) and has to move in cluttered environments. The main challenges described in this chapter are the definition of motion planning strategies that cope with the building maps and the cluttered environments. The algorithms were developed and implemented in a standalone application that receives CAD models of the buildings and returns the best trajectories, including reports of the most risky points of collision, and the swept volume of the vehicle along the missions. More than 700 trajectories were computed for different CPRHS types applied in the models of the real scenarios, crucial to proceed with the construction of the Tokamak Building.

The EU-DEMO remote maintenance strategy must be relevant for a range of in-vessel component design options. The remote maintenance project must provide an understanding of the limits of the strategy and technologies so as to inform the developing plant design of the maintenance constraints. A comprehensive set of maintenance requirements has been produced, in conjunction with the plant designers, against which design options can be assessed. The proposed maintenance solutions are based around a strategy that deploys casks above each of the vertical ports to exchange the blanket segments and at each of the divertor ports to exchange the divertor cassettes. The casks deploy remote handling equipment to open and close the vacuum vessel, remove and re-install pipework, and replace the in-vessel components. A technical design risk assessment has shown that the largest risks are common to all of the proposed solutions and that they are associated with two key issues, first; the ability to handle the large blanket and divertor components to the required positional accuracy with limited viewing and position feedback, and second; to perform rapid and reliable pipe connections, close to the blankets, with demonstrated quality that meets the safety requirements.

Feature extraction and selection are important steps in the construction of a map to support the navigation of mobile robots in outdoor environments. The large amount of data acquired by the on-board sensors has to be reduced to retain only the crucial information for the navigation purpose. This procedure should be robust given the rough, dynamic and unpredictable conditions provided by outdoor scenarios. The paper discusses the use of different types of features and proposes a feature selection criteria aiming at building a topological map of the environment. The approach was tested with real data acquired in different types of outdoor scenarios.

This paper addresses the path following problem of a wheeled mobile robot with rhombic like kinematics (two drivable and steerable wheels) operating in cluttered environments. Four path following controllers are developed to steer the kinematic model of a rhombic like vehicle (RLV) along a desired path: three are based on feedback laws derived at a kinematic level with geometrical inspiration; the fourth is a nonlinear controller built upon a kinematic model of the vehicle using Lyapunov functions. By fully exploiting the kinematic capabilities of this type of vehicles, all the developed controllers are capable of performing under two situations: when both wheels follow the same path, or when each wheel follows a different path. Simulated and experimental results are presented in the paper to illustrate the performance of the controllers. The main conclusions of these controllers are summarized, leading to a possible application in the vehicles that will operate in the remote handling missions of the International Thermonuclear Experimental Reactor (ITER).

Rhombic like vehicles are characterized for high maneuverability in cluttered environments. This type of vehicles will be used on remote handling operations of maintenance in the International Thermonuclear Experimental Reactor (ITER). Previous work was done in motion planning using Constrained Delaunay Triangulation for rhombic like vehicles operating in ITER. This paper shows that the integration of Fast Marching Square improves the motion planning methodology, decreasing also the computational effort, which can be applied not only in ITER but also in other complex and cluttered environments. Simulated results are presented comparing the initial and the improved motion planning.

This paper describes a study of different remotely operated driving modes applied to rhombic like vehicles using the digital buttons and the analog sticks of a generic game controller device (e.g., joysticks and gamepads). The performance of the different modes was evaluated using a software simulator and a 2D model of the Tokamak building of ITER. Several experiments were performed taking into account relevant parameters, such as the distance to the obstacles and accelerations. An optimal approach for a real implementation with a rhombic like vehicle prototype is proposed and discussed.

This paper proposes a new path optimization method to improve feasibility and optimality of rough collision-free paths provided by global planners. Inspired on the dynamics of rigid bodies, this method redefines the elastic bands framework to explicitly handle vehicle geometric constraints and explore the high maneuvering ability of rhombic vehicles. The proposed method was tested as a post optimization technique on global path solutions planned for a large transporter that will operate in the International Thermonuclear Experimental Reactor (ITER). Presented results show the proficiency of this method on handling feasible and reliable paths in cluttered scenarios such as those in ITER.

This paper presents a Particle Filter approach to solve the metric localization of a team of three robots. The method considers the existence of a fixed active beacon which has sensorial capabilities. The localization strategy is based on the distance and orientation measurements among the robots and the robots and the fixed active beacon. By means of this technique the team of robots are capable of navigating in isolated and unstructured scenarios. In spite of common differential vehicles, this approach is intended to be applied in car-like vehicles, still a large scope of mobile robots in real environments.

Within the probabilistic methods for the state estimation of a dynamic system, the particle filter approach is an innovative technique which is focusing the attention of current researches. Particle filtering succeeds in applying to different type of systems (linear and non-linear) and noise models. This paper presents a comparison between the results obtained using the particle Filter and the Kalman Filter for estimating the orientation and velocity of a DC motor. Real experiments are also presented.

The Transfer Cask System (TCS) is one of the adopted Remote Handling (RH) components to operate on the International Thermonuclear Experimental Reactor (ITER). During maintenance operations, the TCS is expected to move between specified locations in different levels of the Tokamak Building (TB), transporting heavy and highly activated components while meeting competing safety requirements. This paper proposes a complete motion planning methodology, covering path optimization and trajectory evaluation for static but tightly constrained scenarios. The optimization scheme is inspired on the elastic bands method, and takes into account geometric and kinematic robot considerations.