Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

La maintenance robotisée : un challenge pour l’énergie de fusion

La maintenance robotisée est un défi essentiel et continu pour le développement du réacteur de fusion. Débutées à JET afin de répondre aux exigences de manipulation des éléments de première paroi contaminés en béryllium, les opérations de maintenance robotisées et les équipements associés sont à développer afin de permettre la maintenance de composants hautement activés et contaminés à l’intérieur de l’enceinte à vide comme le divertor et les éléments de couverture. Les équipements de robotique d’ITER comprennent des dispositifs séparés pour l’inspection, la maintenance et la réparation de composants comme les cassettes de divertor, les couvertures de protection, les injecteurs de neutres, les “port-plugs”, etc. Un système dédié est aussi nécessaire pour transférer ces éléments depuis l’enceinte à vide jusqu’aux cellules chaudes. A cause des exigences élevées qui sont demandées, il est hautement recommandé de réaliser l’assemblage initial d’ITER en utilisant les moyens de télémaintenance quand l’accès humain est encore possible à des fins d’entraînement et de supervision des opérations de maintenance. Le démarrage d’ITER pleinement opérationnel d’un point de vue maintenance des composants, inspection et moyen transfert vers les cellules chaudes est aussi à considérer. L’étape après ITER en vue du réacteur électrogène est un démonstrateur avec ses défis encore plus complexes pour développer et tester une maintenance robotisée compatible avec des exigences de disponibilité élevée. Celle-ci est en effet une condition impérative pour garantir la compétitivité économique des futurs réacteurs de fusion. Comparée à la fission avec des opérations de maintenance plus simples comme le remplacement de combustible ou des opérations d’inspections de cuves ou de composants primaires où l’intervention humaine reste possible même pendant des courtes périodes, la maintenance d’un réacteur de fusion exige des séquences d’opérations complexes où l’accès humain et la vision ne sont pas possibles

IMechE Seminar- Mechatronics in Medicine, Healthcare and Rehabilitation- Nov 2003 Force Feedback Mechatronics in Medecine, Healthcare and

Robotics force feedback technologies provide the feeling of directly holding remote instruments. This is true in nuclear applications where remote operations are required due to the hazardous environment. This is also true in surgery applications, in particular in Minimally Invasive Surgery (MIS), when organs cannot be accessed directly. During surgery procedures, the surgeon should have the feeling in his hands of holding directly the surgical instruments interacting with the patient. Both applications emphasize therefore same type of needs for high performance force feedback Mechatronic components. We aim therefore benefits from research and development results from the field of Mechatronics for Telerobotics to provide good basis for improvement in medical technology. Many similarities could also be pointed out with various other applications requiring force feedback features for gesture guidance or training: medical learning course with help of haptic and virtual reality technologies, kinaesthetic and physical assist device for rehabilitation, aged people or disable people. 1

Development of a long reach articulated manipulator for ITER in vessel inspection under vacuum and temperature

This project takes place in the EFDA Remote Handling (RH) activities for the fusion reactor International Thermonuclear Experimental Reactor (ITER). The aim of the R&D program is to demonstrate the feasibility of in-vessel RH intervention by a l

ITER Upper Port Plug handling cask system assessment and design proposals

The current design of the ITER cask for Upper Port Plugs has been evaluated. Careful reduction of the number of mechanical degrees of freedom is an opportunity to relax the tolerances in the design, resulting in cost reduction and reliability increase. A new kinematical design for the tractor module has a higher stiffness to weight ratio, reduces actuator forces by a factor four and minimizes cross-talk between lift and rotation motion. Non-cantilevered handling is recommended to reduce wheel loads on the tractor by a factor six and to simplify guidance. At the system level the tubular guide (TG) is proposed, a semi-permanent 3.5 m long tube which is an extension of the Upper Port. Cask docking is simplified and the risk of the cask tilting is prevented. Redesigning the system concept is recommended and the TG looks promising. Since a system level redesign impacts the external interfaces, overall feasibility has to be investigated

ITER transfer cask: Preliminary assessment of dose rate due to dust remained in the cask

International audienceThe Remote Handling tasks scheduled during the ITER maintenance shutdown require transportation of in-vessel components and remote-handling tools from the Vacuum Vessel (VV) ports to the Hot Cell Building (HCB). These components and tools will be moved using the Cask and Plug Remote Handling System (CPRHS). During plasma operations, plasma facing components will be highly activated by neutrons and/or contaminated with tritium. After plasma operations, activated dust will be removed from the VV but some amounts will remain. Therefore, the CPRHS may be contaminated by residual activated dust due to the transportation of these components between the VV and the HCB. As the CPRHS is not shielded, residual activated dust may lead to a residual dose rate around the CPRHS. To assess the risk of external exposition in case of human intervention for maintenance purpose inside or close to the CPRHS, dose rate estimations were performed around and inside the CPRHS for several initial dust configurations with the normalized value of 1 g of residual activated dust. The results of this study constitute a dosimetric data base and may support ITER Organization in the definition of a decontamination level and maintenance plan

ITER Upper Port Plug handling cask system assessment and design proposals

The current design of the ITER cask for Upper Port Plugs has been evaluated. Careful reduction of the number of mechanical degrees of freedom is an opportunity to relax the tolerances in the design, resulting in cost reduction and reliability increase. A new kinematical design for the tractor module has a higher stiffness to weight ratio, reduces actuator forces by a factor four and minimizes cross-talk between lift and rotation motion. Non-cantilevered handling is recommended to reduce wheel loads on the tractor by a factor six and to simplify guidance. At the system level the tubular guide (TG) is proposed, a semipermanent 3.5 m long tube which is an extension of the Upper Port. Cask docking is simplified and the risk of the cask tilting is prevented. Redesigning the system concept is recommended and the TG looks promising. Since a system level redesign impacts the external interfaces, overall feasibility has to be investigated. (C) 2011 Elsevier B.V. All rights reserved