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During the EU DEMO Pre-Concept Design Phase, the remote maintenance team developed maintenance strategies and systems to meet the evolving plant maintenance requirements. These were constrained by the proposed tokamak architecture and the challenging environments but considered a range of port layouts and handling system designs. The design-driving requirements were to have short maintenance durations and to demonstrate power plant relevant technologies. Work concentrated on the in-vessel maintenance systems, where the design constraints are the most challenging and the potential impact on the plant design is highest. A robust blanket handling system design was not identified during the Pre-Concept Design Phase. Novel enabling technologies were identified and, where these were critical to the maintenance strategy and not being pursued elsewhere, proof-of-principle designs were developed and tested. Technology development focused on pipe joining systems such as laser bore cutting and welding, pipe alignment, and on the control systems for handling massive blankets. Maintenance studies were also conducted on the ex-vessel plant to identify the additional transport volumes required to support the plant layout. The strategic implications of using vessel casks, and of using containment cells with cell casks, was explored. This was motivated by the costs associated with the storage of casks, one of several ex-vessel systems that can drive the overall plant layout. This paper introduces the remote maintenance system designs, describes the main developments and achievements, and presents conclusions, lessons learned and recommendations for future work.

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.

In the last decade, the development of more compact and lightweight radiation detection systems led to their application in handheld and small unmanned systems, particularly air-based platforms. Examples of improvements are: the use of silicon photomultiplier-based scintillators, new scintillating crystals, compact dual-mode detectors (gamma/neutron), data fusion, mobile sensor networks, cooperative detection and search. Gamma cameras and dual-particle cameras are increasingly being used for source location. This study reviews and discusses the research advancements in the field of gamma-ray and neutron measurements using mobile radiation detection systems since the Fukushima nuclear accident. Four scenarios are considered: radiological and nuclear accidents and emergencies; illicit traffic of special nuclear materials and radioactive materials; nuclear, accelerator, targets, and irradiation facilities; and naturally occurring radioactive materials monitoring-related activities. The work presented in this paper aims to: compile and review information on the radiation detection systems, contextual sensors and platforms used for each scenario; assess their advantages and limitations, looking prospectively to new research and challenges in the field; and support the decision making of national radioprotection agencies and response teams in respect to adequate detection system for each scenario. For that, an extensive literature review was conducted.

Radiological monitoring is fundamental for compliance with radiological protection policies in the aftermath of radiological events, such as nuclear accidents, terrorism, and out-of-commission uranium mines. An effective strategy for radiation monitoring is to use radiation detectors coupled with Unmanned Aerial Vehicles (UAVs), enabling for quicker surveillance of large areas without involving the need of human presence in the target area. The main aim of this study was to formulate the parameters for a UAV flight strategy in preparation for future field measurements using Geiger&ndash, Muller Counters (GMC) and Cadmium Zinc Telluride (CZT) spectrometers. As a proof of concept, the prepared flight strategy will be used to survey out-of-commission uranium mines in northern Portugal. Procedures to assure the calibration of the CZT and verification of the GMCs were conducted, as well as a sensitivity analysis of the sensors considering different acquisition times, distance to source, and detector response time. This article reports specific parameters, such as UAV distance to ground, time of exposition, speed, and the methodology to perform the identification and calculate the activity of possible radioactive sources. An effective flight strategy is also presented, aiming to use radiation detectors coupled with UAVs to undertake extensive monitoring of areas with enhanced levels of environmental radiation, which is of prime importance due to the lasting hazardous effects of enhanced environmental radiation in the nearby ecosystem and population.

This work proposes a solution to identify the number of sources of radiation, as well as their respective intensities and locations based on data acquired by Global Positioning System (GPS) receivers and affordable radiological sensors, such as Geiger-M¨uller counters (GMC). An optimization algorithm is required to minimize the estimation error in terms of location, intensity and number of sources of radiation given all the intensity measurements acquired in different locations, taking into account the sensors’ models, background radiation intensity values and noise. Experimental results were achieved in a laboratory with controlled sources of radiation. The solution was also tested with real data gathered by a GMC connected to a mobile phone with a software application developed by the authors to synchronize the sensor readings with GPS data. The sensor and the mobile phone are attached to a quadcopter flying over the scenario with sources of radiation.

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.

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.

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).

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.

The Collective Thomson Scattering (CTS) diagnostic will be a primary diagnostic for measuring the dynamics of the confined fusion born alpha particles in ITER and will be the only diagnostic for alphas below 1.7 MeV [1]. The probe beam of the CTS diagnostic comes from a 60 GHz 1 MW gyrotron operated in a ~100 Hz modulation sequence. In the plasma, the probing beam will be scattered off fluctuations primarily due to the dynamics of the ions. Seven fixed receiver mirrors will pick up scattered radiation (the CTS signal) from seven measurement volumes along the probe beam covering the cross section of the plasma. The diagnostic is planned to provide a temporal resolution of ~100 ms and a spatial resolution of ~a/4 in the core and ~a/20 near the plasma edge where a = 2.0 m is the nominal minor radius of ITER. The front-end quasi-optics will be installed in an equatorial port plug (EPP#12). A particular challenge will be to pass the probing beam through the fundamental electron cyclotron resonance, which is located in the port plug (R=10.3 m) for the nominal magnetic field Bt = 5.3 T. Hence, particular mitigation actions against arcing have to be applied. The status of the design and specific challenges will be discussed.