1,721,193 research outputs found
Design Progress of the DEMO Divertor Locking System According to IPADeP Methodology
No full textThe 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
Further improvements in the structural analysis of DEMO Divertor Cassette body and design assessment according to RCC-MRx
No full textThis 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. © 201
Study of dynamic amplification factor of DEMO blanket caused by a gap at the supporting key
No full textAmong the design activities of the in vessel components for DEMO promoted by European Fusion Development Agreement (EFDA) organization, this work deals with the gap required at the supporting keys of the blanket. Due to its higher operating temperatures compared to the vacuum vessel (VV) ones, this gap will increase during operation. The electro magnetic (EM) loads due to fast disruptions occur on a short time and might accelerate the blanket significantly before it touches the supporting keys, causing an impact of the blanket itself onto the keys. Depending on their stiffness, the EM loads with their short time scale could excite the structure's natural frequencies, causing dynamic amplification. Both phenomena (impact and dynamic amplification) can cause stresses in the structure significantly higher than the static ones. This work develops a finite element model of DEMO blanket to study its non-linear transient dynamic behavior under impact loadings. A VV sector, the ribs between the inner and outer VV, the backward manifolds and the supporting keys of the blanket have been modeled. The analyses have been performed with Abaqus [1] and Ansys [2] FEM codes focused on the displacements of the keys in their housing on the blanket. The dynamic amplification factor has been evaluated as the ratio of dynamic to static displacements in meaningful points of the structure for a growing gap till 5 mm. © 2015 Elsevier B.V. All rights reserved
Application of Eurofer97 steels for demo divertor cassette irradiated at temperature below 350 °C
Full text linkL'acciaio inossidabile austenitico AISI 316 L(N) IG è utilizzato come materiale strutturale per i principali componenti in-vessel di ITER. Quando le fluenze neutroniche aumentano come nei componenti in-vessel di DEMO, non è possibile utilizzare l’AISI 316 in quanto è soggetto a forte attivazione a causa dell'elevata presenza di Nichel. Devono essere previsti acciai ferritici/martensitici ad attivazione ridotta come l’Eurofer97 che mantengono buone proprietà thermo-meccaniche e stabilità dimensionale sotto irraggiamento (i.e. resitenza al rigonfiamento). L'obiettivo principale del presente lavoro è quello di evidenziare lo stato dell’arte circa le proprietà meccaniche dell’Eurofer97 irraggiato a temperature al di sotto di 350 °C. In base ai dati raccolti, è discussa la fattibilità per applicazioni strutturali dell’Eurofer97 e degli acciai ferritici/martensitici nel caso di impiego dell’acqua come fluido refrigerante per la cassetta del divertore. Questo rapporto a questo stadio non tiene conto degli impatti della corrosione sugli acciai RAFMs che sono probabilmente meno critici degli effetti dell’infragilimento da irraggiamento.The austenitic stainless steel AISI 316 L(N) IG is used as structural material for the main ITER in-vessel components. When neutron fluences increase, as in DEMO in-vessel components, it is not possible to use AISI 316, which is subject to strong activation due to its high nickel content. Ferritic/martensitic steels with reduced activation properties as Eurofer97 which keep good thermo-mechanical properties and good dimensional stability under irradiation (i.e. resistance to swelling), must be envisaged. The principal objective of the present paper is to address the current status about the mechanical properties of Eurofer97 irradiated at temperature below 350 °C. Based on the collected data, the feasibility of Eurofer97 and Reduced Activation Ferritic/Martensitic (RAFM) steels for structural applications is discussed in case of using water as coolant for divertor cassette. This report at this stage does not account for corrosion-related impacts on RAFMs behavior, which are likely less critical than irradiation embrittlement effects
Riluzole: What It Does to Spinal and Brainstem Neurons and How It Does It
No full textAmyotrophic lateral sclerosis (Lou Gehrig's disease) is a devastating neurodegenerative disorder for which the only licensed treatment is riluzole. Although riluzole clinical efficacy is rather limited, its use has important implications for identifying those parameters that might improve its clinical benefits (dose, timing, disease stage) and for its offlabel administration in other neurodegenerative diseases, such as spinal cord injury. Studies of riluzole also have an intrinsically heuristic value to unveil mechanisms regulating the excitability of brain and spinal neurons because this drug is a pharmacological tool to probe the function of certain ion channels, or to study neurotransmitter release processes, and intracellular neuroprotective pathways. The present review focuses on how riluzole acts on brain and spinal neurons within motor networks, what mechanisms can be deduced from its effects, and what conditions may favor its use to contrast neurodegeneration or to ameliorate late symptoms like spasticity. Taking as an example the experimental neurodegeneration caused by overactivation of glutamatergic synapses (excitotoxicity), it seems likely that protection of motor networks by riluzole involves selected administration timing and dosing to target processes for releasing glutamate from very active synapses or for dampening repetitive firing by hyperfunctional motor cells. © The Author(s) 2012
S100β as an early biomarker of excitotoxic damage in spinal cord organotypic cultures
No full textS100β is a cytoplasmic calcium-binding protein mainly expressed by glia and considered to be a useful biomarker for brain or spinal cord injury. Indeed, clinical studies suggest that the S100β concentration in serum or cerebrospinal fluid may predict lesion outcome and prognosis. The relation of S100β levels to damage severity and its timecourse remains, however, unclear. This study used a validated in vitro model of spinal cord injury induced by kainate-mediated excitotoxicity to investigate these issues. After 22 days in vitro, rat organotypic spinal cord slices were subjected to one transient application (1 h) of 1 or 100 μM kainate followed by washout. While the lower kainate concentration did not evoke neuronal loss or S100β increase, the larger concentration elicited 40% neuronal death, no change in glial number and a delayed, significant rise in extracellular S100β that peaked at 24 h. This increase was associated with a stronger expression of the S100β protein as indicated by western blotting and immunohistochemistry. Application of the microtubule disrupting agent colchicine did not change the rise in S100β induced by kainate, an effect blocked by the glutamate receptor antagonists CNQX and APV. Our data suggest that excitotoxicity was followed by release of S100β perhaps from a readily releasable pool through a mechanism independent of microtubule assembly. The raised extracellular level of S100β appeared to reflect glial reactivity to the kainate-evoked lesion in accordance with the view that this protein may be involved in tissue protection and repair after acute injury. Excitotoxicity is a major mechanism responsible for neuronal death following acute spinal cord injury. The calcium-binding protein S100β is released by astrocytes into the extracellular compartment during the first 24 h after the initial insult and represents a useful biomarker of lesion progression as its level is related to the occurrence and severity of neuronal loss. Excitotoxicity is a major mechanism responsible for neuronal death following acute spinal cord injury. The calcium-binding protein S100β is released by astrocytes into the extracellular compartment during the first 24 h after the initial insult and represents a useful biomarker of lesion progression as its level is related to the occurrence and severity of neuronal loss. © 2014 International Society for Neurochemistry
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