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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.

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.

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 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.

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.

Activated material can be found in different scenarios, such as in nuclear reactor facilities or medical facilities (e.g. in positron emission tomography commonly known as PET scanning). In addition, there are unexpected scenarios resulting from possible accidents, or where dangerous material is hidden for terrorism attacks using nuclear weapons. Thus, a technological solution is important to cope with fast and reliable remote inspection. The multi-copter is a common type of Unmanned Aerial Vehicle (UAV) that provides the ability to perform a first radiological inspection in the described scenarios. The paper proposes a solution with a multi-copter equipped with on-board sensors to perform a 3D reconstruction and a radiological mapping of the scenario. A depth camera and a Geiger-Müler counter are the used sensors. The inspection is performed in two steps: i) a 3D reconstruction of the environment and ii) radiation activity inference to localise and quantify sources of radiation. Experimental results were achieved with real 3D data and simulated radiation activity. Experimental tests with real sources of radiation are planned in the next iteration of the work.

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 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.

The ex-vessel Remote Maintenance Systems are responsible for the replacement and transportation of the plasma facing components. The space required to perform the ex-vessel operations of transportation, as well as the respective time duration, has a great impact in the economics of a fusion power plant. This paper provides a preliminary assessment of the volume required to perform the operations of transportation along optimized trajectories in all levels of DEMO's reactor building. The overhead systems and ground systems are considered as the possible transportation technologies. In particular to the upper level, a cask concept is compared with a hot cell concept. Computed results of occupied volumes and time duration are presented taking into account the nominal, i.e., the expected and planned operations, and the possible rescue operations.

The reflectometry diagnostic for demonstration fusion reactor (DEMO) is envisaged to provide the electron density profile and to be used as a control diagnostic for the real-time vertical position controller. An initial conceptual study has been performed defining the position of the antennas and the routing of the waveguides. In the present design, the integration has been driven by the remote handling and blanket interfaces. To progress with the system integration, neutronics simulations were performed to assess the cooling requirements. This paper presents a nuclear and thermal analysis for the initial design of the reflectometry diagnostic for DEMO. The neutronics simulations were performed using the Monte Carlo simulation program MCNP6 and FENDL 2.1 cross sections, while ANSYS mechanical v18 was used to perform the thermal analysis. Simulation results show that the nuclear heat loads reach 8 W/cm3 at the surface of the diagnostics section. Without an active cooling system, the operating temperatures of the components under such heat loads would be well above the acceptable from the thermomechanical point of view. The thermal analysis here presented provides the temperature distribution in the components when subjected to neutron/gamma irradiation and thermal radiation from the plasma, after the implementation of a preliminary design of the active cooling system. The operation temperatures of the plasma-facing antennas, as well as the performance of the diagnostics system from the neutron shielding point of view, are analyzed and discussed in this paper.