1,720,967 research outputs found
Tritium release scenarios in the IRPR system of DEMO: Safety assessment and mitigation strategies
Full text linkThis study investigates potential tritium release scenarios in the Isotope Rebalancing and Protium Removal (IRPR) system of DEMO fuel cycle, focusing on failures in the Temperature Swing Absorption (TSA) unit, including its feed tank. Two accident cases are considered, based on the postulated initiating events identified by the FFMEA: (1) a guillotine break in the pipeline supplying the IRPR system and (2) a pipe rupture in the TSA unit. MELCOR 1.8.6 for fusion is used to simulate the dynamics of the gases (hydrogen, air, inert gases), the resulting pressurization of the enclosure volumes, and the accumulation of hydrogen isotopes. A parametric study evaluates the impact of design choices like feed tank configuration and glovebox volume, informing the design of the system to enhance safety. The analysis includes cases where safety systems such as detritiation or isolation fail to operate correctly. The findings support ongoing safety assessments for DEMO and inform strategies to improve safety in fusion power plants
ARC-class tokamaks: Preliminary design, system modeling and safety assessment
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Assessment of structural materials in compact fusion reactor design
Full text linkThe development of fusion energy systems demands structural components capable of withstanding extreme operational conditions, including intense neutron fluxes, high thermal and mechanical loads, and stringent requirements on neutron activation. Several structural materials have been proposed, such as nickel-based superalloys, reduced activation ferritic/martensitic steels, oxide-dispersion-strengthened alloys, SiC/SiC ceramic matrix composites, and vanadium-based alloys. While those materials have been extensively analysed for large tokamaks, no comparative studies exist on compact tokamaks. This work addresses this gap by considering an ARC-class tokamak as representative of compact design. The materials are evaluated based on the following criteria: power density deposition, absorption rate, TBR, energy multiplication factor within the breeding blanket, and displacement per atom. Numerical simulations were performed using the OpenMC Monte Carlo particle transport code to evaluate the neutronic behavior and activation characteristics of the selected structural materials. A simplified compact reactor model was developed using Constructive Solid Geometry (CSG) to enable consistent and reproducible comparisons. ODS steels and vanadium-based alloys emerged as the most promising candidates for application in compact, high-temperature fusion devices. ODS steels combine low activation with favorable performance across all evaluated metrics, offering a balanced tritium breeding capability alongside good resistance to radiation damage. Vanadium-based alloys, in turn, exhibit very low hydrogen and helium production, minimal power density deposition, facilitating heat removal from the structural material, and activation levels significantly lower than those of conventional austenitic steels. Across all materials, the simulations predict TBR values in the range of 0.90–1.25, energy multiplication factors of between 1.12 and 1.18, and first structural layer power densities of over 7 MW/m3. In the most favourable cases, the shutdown dose rates fall below natural background levels in less than 50 years
Analysis of road accidents fatalities: the impact of socio-economic factors and innovative solution strategies
Full text linkIn this work we present an experiment of guided innovation in the frame of the Innovation for Change program, where a group of students is called to solve a given challenge with innovative solutions, by applying methodological approaches throughout the all process. The problem under analysis is ‘road crash fatalities’, with a focus on the consequences of a poor post-crash care management. The solution is developed through a series of steps, such as problem definition, brainstorming sessions and interviews with stakeholders. Finally, the outputs of this process are presented as well as the designed solution, called EyeWay, which exploits already available technologies to perform automatic accident detection and shorten the crash notification time
A preliminary CFD and Tritium transport analysis for ARC blanket
Full text linkThe Affordable, Robust, Compact (ARC) fusion reactor is a preconceptual design proposed by the Plasma Science and Fusion Center at the Massachusetts Institute of Technology that will be developed by Commonwealth Fusion Systems. ARC features a Li2BeF4 (FLiBe) molten salt liquid blanket that provides reactor cooling, neutron shielding, and tritium breeding. This work aims to develop a preliminary coupled computational fluid dynamics (CFD) and tritium transport model to describe FLiBe flow inside the tank and to assess ARC tritium inventory in the vacuum vessel and blanket. Both models are built by taking advantage of COMSOL® Multiphysics. FLiBe velocity and temperature fields are evaluated by the CFD models, and they are passed as input to the tritium transport model. The tritium transport model computes tritium concentration inside solid materials and FLiBe. An auxiliary FLiBe inlet has been moved from the original position in the ARC preconceptual design to improve blanket cooling and to reduce the size of flow eddies. Results show that many recirculation zones generate inside the tank for the chosen tank geometry, size, and inlet-outlet conditions. Larger FLiBe temperature and tritium concentration are found in these zones. The high FLiBe temperature in recirculation areas may not allow for effective cooling, and Inconel 718 reaches critical temperatures. The largest tritium concentration for a steady-state model with continuity of tritium partial pressure at the interfaces is found in Inconel 718 while the second-highest concentration is reached in FLiBe. The total tritium inventory in the ARC blanket with the assumed model is quantified as 3.16 g
Impact of trapping on tritium self-sufficiency and tritium inventories in fusion power plant fuel cycles
Full text linkThe dynamic analysis of fusion power plant (FPP) fuel cycles highlights the challenge of achieving tritium self-sufficiency in future FPPs. While state-of-the-art fuel cycle models offer valuable insights into the necessary design parameters for attaining tritium self-sufficiency, none of these models currently consider the impact of tritium trapping within fuel cycle components. However, detailed analysis of individual components reveals that substantial amounts of tritium can be trapped within the first wall, divertors, and breeding blanket systems, suggesting that tritium trapping may significantly influence the FPP ability to achieve self-sufficiency. The compounded effects of additional tritium traps generated by irradiation effects and component replacements further exacerbate this challenge. The novelty of this work is the integration of an explicit, physics-based model for tritium trapping, evolution of damage-induced traps, and component replacements into a dynamic, system-level model of a fuel cycle. The results show an increase of a factor of tritium inventory in the first wall and vacuum vessel of an ARC-class FPP when accounting for the aforementioned phenomena. This, coupled with the replacement of components subject to significant tritium trapping, slows down fuel cycle dynamics, resulting in an extended tritium doubling time (50% increase), higher start-up inventory (30% increase), and higher required tritium breeding ratio (2%–5%) compared to a scenario without tritium trapping
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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