1,720,978 research outputs found
Numerical investigation of ALFRED under seismic scenario
No full textThe European project ANSELMUS focuses on the safety of advanced Heavy Liquid Metal (HLM) cooled reactors, including ALFRED, developed by the FALCON consortium, The reactor's operation progresses through three power levels (100, 200, and 300 MWth), requiring significant preliminary R&D efforts. The first ANSELMUS WP includes a Phenomena Identification Ranking Table (PIRT) analysis on ALFRED to prioritize R&D activities starting with ALFRED's reference design, selecting accidental transients to enhance the understanding of critical quantities known as FoMs (Figure of Merits). Supporting numerical analyses are
executed within the same project. This paper examines core compaction following a seismic scenario using a detailed nodalization developed with the RELAP5 system code
Post-Test Analysis of SIRIO Facility Data by System Thermal-Hydraulic Codes for LFR Application
Get PDFAs part of the R&D activities supporting Generation IV innovative nuclear technologies, an experimental facility named SIRIO has been designed and constructed to test and validate a new concept of Decay Heat Removal system at a relevant scale for Gen-IV Lead-cooled Fast Reactor (LFR), in particular for the DEMO LFR ALFRED. This innovative system provides a safe long-term cooling condition of the reactor coolant system with no need of external action or energy supply, and claims capability to passively control the heat removed by the ultimate heat sink thanks to non-condensable gases.
This new concept is attractive for LFRs because it can prevent the early freezing of lead, which is a concern after the proper intervention of the DHRs. In addition, for water cooled reactors, passive control of heat transfer capability reduces the thermal stresses on the materials, smoothing the fluid internal thermal gradients and the depressurization rate.
In this work, SIRIO facility is described, along with the numerical model developed using the RELAP5/Mod3.3 thermal-hydraulic system code. Part of the efforts in the experimental campaign within the EU project PIACE aims at reproducing the conditions of ALFRED in Stage 2 configuration (i.e., loop and gas pressure set at 180 and 110 bar, respectively). The experimental outcomes are compared
with those obtained with RELAP5 code to validate the numerical tool for LFRs applications and to assess the code capability in reproducing two-phase natural circulation conditions with noncondensable gases and the system response during accidental scenarios
Pre-test analysis and thermal-hydraulic characterization of the versatile loop facility
Get PDFLead-cooled fast reactors (LFRs) are a concept of advanced nuclear reactor using liquid lead or lead–bismuth eutectic (LBE) as coolant. These reactors operate with a fast neutron spectrum, enabling efficient use of nuclear fuel and the capability to burn long-lived radioactive isotopes, thereby reducing nuclear waste. LFRs offer significant safety benefits due to the properties of lead, such as high boiling point, excellent heat transfer, absence of exothermic reactions with water and air, enabling passive safety features and efficient heat removal in case of accidents. Among the various LFR concepts, a significant effort has been carried out by Westinghouse Electric Company (WEC) to design a pool-type LFR with a core power of 950 MWth. As R&D efforts continue to advance LFR technology, the focus is on optimizing reactor design, developing robust experimental facilities, and validating numerical tools to ensure the reliable and safe operation of these next-generation systems. To address knowledge gaps in liquid lead technology, dedicated experimental campaigns are necessary. In particular, for the WEC-LFR reactor, the key components of the Reactor Coolant System (RCS) of the WEC-LFR will be tested and characterized in the Versatile Loop Facility (VLF). The facility features a lead loop operating up to 650 °C, equipped with a 500-kW electric Fuel Pin Bundle Simulator (FPBS) representing the Westinghouse LFR bundle design. It also includes a hybrid microchannel-type diffusion-bonded heat exchanger, which represents the primary heat exchanger used in the Westinghouse LFR. Heat removal is managed by a supercritical water-cooling loop, designed to operate at a pressure of 330 bar and temperatures up to 620 °C. This paper details the design of the VLF, then its numerical model is presented, along with the thermal–hydraulic characterization of the facility using the system code RELAP5/Mod3.3, properly modified to include the thermo-physical properties of liquid lead. Additionally, a detailed characterization of the FPBS has been performed using the subchannel code DASSH developed by Argonne National Laboratory. Finally, starting from a steady state condition representative of the WEC-LFR, two accidental transients have been simulated: the loss of heat sink and the loss of the FPBS power. Both analyses provide important indications for the safe operation of the experimental plant
Re-scaling and Pre-test Analysis of SIRIO facility
No full textIn R&D for Generation IV reactors, SIRIO tests an innovative decay heat removal system for ALFRED, a Lead-Cooled Fast Reactor. Given the high freezing point of ALFRED coolant (327°C), its DHR must balance passive decay heat removal with maintaining the lead above its freezing temperature. The self-regulating DHR operation is based on the degradation of condensation efficiency with non-condensable gases. This paper details a new re-scaling using the "power-to-volume" approach on ALFRED's revised design. It also describes SIRIO's numerical model developed with RELAP5/Mod3.3 and presents simulation results, comparing them with full-scale system to verify the predicted consistency and the fidelity of the scaling
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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