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Content The High Resolution Neutron Spectrometer (HRNS) system for ITER is an array of neutron spectrometers with the primary function to provide measurements of the fuel ion ratio, nT/nD, in the plasma core. Supplementary functions are to assist or provide information on fuel ion temperature and energy distributions of fuel ions and confined alpha-particles. The ITER requirement for the HRNS primary function is to obtain nT/nD with 20% uncertainty and a time resolution of 100 ms. In this contribution, a conceptual HRNS system design and its measurement performance for nT/nD will be presented. The HRNS system studied, is based on established instrumental techniques and its performance is assessed using realistic response functions for the individual spectrometers in the system. The main interfacing requirements for the HRNS is a 10 cm diameter aperture in the ITER first wall, tapered collimation resulting in a neutron flux in the order of 1099 n/cm22/s on an area of 12 cm22 at a distance of 16 m from the first wall. For optimum use of the available neutron flux, the system is divided into two sections; "low efficiency" neutron spectrometers in the front and "high efficiency" in the rear. Also investigated is to use an adjustable collimator between the front and rear spectrometers in order to enhance the dynamic range and overlap of the two sections. For the combination of neutron spectrometers presented here, it is shown that the system fulfills the ITER requirement, on nT/nD, over an order of magnitude in fusion power, 50 < Pfus < 500 MW. In the performance study, contributions due to neutron scattering in the vessel walls, collimator and beam dump are included together with a neutron induced gamma background.

This paper presents the enhancements related to the structural analyses of DEMO Divertor in the framework of the EUROfusion Power Plant Physics & Technology (PPPT) program. This activity started two years ago and its preliminary results were published in previous papers. It has been divided in some areas defined by the similarity of the matters they contain: the structural analysis, of utmost importance, has been preceded by a preliminary phase, like the geometry definition or the thermal and the electric-magnetic analysis for loads evaluation; then the structural analysis has been finally confirmed with further evaluations related to excessive deformation or plastic instability. This paper discusses the improvements adopted either in the preliminary analysis or in the main structural analysis. Specifically it highlights the introduction of the thermal and electro-magnetic loads application in terms of a detailed spatial distribution that is now available. More the supports have been introduced in the model and their structural behavior has been investigated considering their interaction with the cassette. The structural assessment, according to the Design and Construction Rules for Mechanical Components of Nuclear Installation (RCC-MRx), has been performed either for the cassette or for the attachments: for the former it is positive while for the latter case serious limitations have been found.

The Iterative and Participative Axiomatic Design Process (IPADeP) deals with the early conceptual design stage of complex mechanical assemblies. It provides a systematic approach based on the theory of Axiomatic Product Development Lifecycle and aims to minimize the risks related to the uncertainty and incompleteness of the requirements, considering that the requirements will be refined and completed during the process. IPADeP has an iterative nature and is focused on the experience of the people involved in the design process. The functional requirements and the design parameters are conceived through brainstorming sessions and the concept selection is performed involving several experts through a Multi Criteria Decision Making technique. IPADeP has been adopted as methodology to address the early conceptual design stage of a subsystem of the DEMOnstration fusion power plant: the divertor cassette-to-vacuum vessel locking system. A first iteration was performed, resulting in the selection of a "high level" rough solution. According with IPADeP this paper presents an improvement of this solution, performing a new iteration of the process, since the system is ripe to proceed with the decomposition and zigzagging to the second level and new requirements are coming in from the development of the interfaced systems. © 2015 The Authors. Published by Elsevier B.V.

This paper refers to the activity of structural design of DEMO Divertor in the framework of the EUROfusion Consortium. The structural analysis and its preparatory assessments were carried on since a year and the first results were published in a previous paper. The Cassette Body has been examined considering the most conservatives loads (e.g. coolant pressure, volumetric nuclear heating and electro-magnetic loads) according to their latest estimates. This work is based on the design-by-analysis approach adopted in the conceptual design phase of the DEMO Divertor. This design activity has been focused on some key parameters e.g. loads, main geometric dimensions, positions of the Cassette attachments on the vacuum vessel, way of loads application to characterize the structural behavior of the Divertor Cassette. In addition to the existing 3D solid element model, a shell element model has also been developed: with this new model a parametric analysis can be done for a fast optimization. The structural assessment was done according to the Design and Construction Rules for Mechanical Components of Nuclear Installation (RCC-MRx).

One of the fundamental input parameters required for the thermo hydraulic and structural design of a divertor cassette is the operation temperature range. In the current design activities to develop European DEMO divertor in the frame of EUROfusion, reduced activation steel EUROFER97 was chosen as structural material for the divertor cassette body considering its low long-term activation and superior creep and swelling resistance under neutron irradiation (You et al., 2016) [1] . For specifying an operation temperature range (i.e. cooling condition) various, often conflicting requirements have to be considered. In this article the lower limit of allowed operation temperature window is defined for EUROFER97 for structural design of DEMO divertor cassette body. The underlying rationale and supporting experimental data from a number of previous irradiation tests are also presented. The motivation of this survey study is to explore the possibility to use EUROFER97 for water-cooled divertor cassette at temperatures below 350 °C which has been regarded as limit temperature to preserve ductility under irradiation. Based on the literature data of FTTT (Fracture Toughness Transition Temperature) calibrated by Master Curve method, it is concluded that EUROFER97 at the envisaged maximum dose of 6 dpa will have to be operated above 180 °C taking the embrittlement due to helium production into account.

This paper presents the recent progress in the pre-conceptual design activities for the EU-DEMO divertor Cassette Body, performed in the framework of the work package “Divertor” of the EUROfusion Power Plant Physics & Technology (PPPT) program. According to Systems Engineering Principles, the divertor CAD model is reviewed, considering the updates in the DEMO configuration model presented by the Programme Management Unit (PMU) in 2017. The design parameters affected by these changes and their impact on the divertor design and on the interfaced systems are analysed. Then, the paper focuses on the integration on the new cassette geometry of the divertor sub-systems. This includes the design of a “shielding liner” for cassette body and Vacuum Vessel protection, as well as the development of the cassette body-to-Vacuum Vessel fixation system. The design activities related to these main sub-systems are discussed in detail, in terms of CAD model and thermo-mechanical calculations.

This paper focuses on a preliminary structural analysis of the current concept design of DEMO vacuum vessel (VV). The VV structure is checked against a vertical load due to a Vertical Displacement Event in combination with the weight force of all components that the main vessel shall bear. Different configurations for the supports are considered. Results show that the greatest safety margins are reached when the tokamak is supported through the lower ports rather than the equatorial ports, though all analyzed configurations are compliant with RCC-MRx design rules.