Recent studies addressing the change of mechanical properties after high temperature irradiation of tungsten have reported substantial increase of the ductile to brittle transition temperature as ...well as increase of the hardness. In this work, we performed microstructural analysis by means of transmission electron microscopy (TEM) on various tungsten grades earlier exposed to high temperature neutron irradiation at 1200 °C up to 1 dpa. The latter corresponds to the expected irradiation temperature on the surface of a tungsten monoblock during the steady state operation in ITER. TEM was applied to five tungsten (W) materials including ITER specification pure W and precipitate strengthened W alloys. The analysis of TEM data coupled with its discussion led to a number of important conclusions regarding the damage induced at 1200 °C neutron irradiation such as: (i) weak effect of recrystallization on the accumulation of the lattice damage; (ii) promising results on the tolerance of damage accumulation in W-Y2O3 grade and (iii) internal oxidation of TiC particles which may contribute to the huge increase of the irradiation induced hardening.
•Neutron irradiated advanced tungsten grades were analyzed with transmission electron microscopy.•The dispersed barrier model based on loops and voids alone is insufficient to explain the hardness increase.•Y2O3 doping of tungsten is beneficial for hardening.•Oxidation of TIC may be responsible for increased hardening in W-1%TiC.
In-vessel maintenance of the ITER tokamak machine needs to be carried out remotely as the radiation level inside the vacuum vessel (VV) is high for human workers because of the activation caused by ...the neutrons generated from fusion reactions. There are neutron diagnostics measuring the neutrons within the VV that need to be calibrated during initial assembly and operation phases that require remote handling of a neutron generator. This paper describes the design and analysis of the transporter of an in-vessel RH system called “Agile Robot Transporter (ART)” that is devised to handle a neutron calibration source and a dual arm manipulator. Its design is focused on agility to have better operational efficiency by reducing the number of port opening, less deployment/removal/operational time, efficient tool change, modular design for easy maintenance and decontamination. The design methodology is described starting from initial design, selection of commercial-off-the-shelf (COTS) components, identification of bespoke components, and iterative processes including mechanical design and analysis. Mechanical design is conducted based on the selected components while respecting the space constraints of the system itself and interfacing systems. The mechanical design includes cabling for the actuators and sensors, means for contamination protection, and modular design for maintenance. Iterative multi-body dynamic analyses by using the MATLAB/Simscape/Multibody and finite element analyses (FEA) by using ANSYS are carried out to find a feasible design solution. Maintainability assessment is conducted by showing the disassembly process.
•An in-vessel remote handling system for ITER called Agile Robot Transporter.•Design methodology for COTS item selection and bespoke item design.•Mechanical design of each body and joint actuator and cabling design.•Dynamic analysis by MATLAB/Simscape/Multibody.•Structural analysis by ANSYS.
