1,721,046 research outputs found
Two-phase modelling for fission gas sweeping in restructuring nuclear oxide fuel
Full text linkIn this work, we propose a modelling approach for the intra-granular fission gas behaviour in UO2 under restructuring process. Leveraging the definition of restructured volume fraction, we consider the fuel matrix transition from the non-restructured to the restructured phase, together with the evolution of the corresponding fission gas concentrations retained in the fuel matrix. Firstly, we derive a sweeping term that exchanges fission gas atoms from the non-restructured to the restructured fuel region. The sweeping term is then included in the conventional intra-granular fission gas diffusion problem. Secondly, the spectral diffusion algorithm is employed to solve two spatially-dimensionless problems, properly representing the non-restructured region with micrometric grains and the restructured region with sub-micrometric grains. The model developed is implemented in SCIANTIX, a 0D meso-scale code for physics-based modelling of fission gas behaviour in nuclear oxide fuel and compared with experimental data and semi-empirical models.LR
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
The AGR-like FHR reactor: Assessing the technical limits of the fuel
No full textThis work presents the detailed fuel rod simulation with the new TRANSURANUS code in combination with a high fidelity neutronic analysis of an innovative British advanced gas cooled type reactor with new materials by means of Serpent. The Hastelloy cladding material and molten salt properties have been assessed and implemented in our previous work. In this paper, we evaluate the effect of uncertainties on Hastelloy cladding properties in the hottest assembly of a sample AGR. For this purpose, a new cladding limiting criterion based on the Larson Miller Parameter are also introduced to determine safety margins to cladding rupture. The fuel performance of the reference AGR-like FHR is studied in terms of gain in safety margins when using the new materials considering their uncertainties. Further needs for the design optimisation are also outlined on the basis of the sensitivity study
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
A new burn-up module for application in fuel performance calculations targeting the helium production rate in (U,Pu)O2 for fast reactors
Full text linkIn light of the importance of helium production in influencing the behaviour of fast reactor fuels, in this work we present a burn-up module with the objective to calculate the production of helium in both in-pile and out-of-pile conditions tracking the evolution of 23 alpha-decaying actinides. This burn-up module relies on average microscopic cross-section look-up tables generated via SERPENT high-fidelity calculations and involves the solution of the system of Bateman equations for the selected set of actinide nuclides. The results of the burn-up module are verified in terms of evolution of actinide and helium concentrations by comparing them with the high-fidelity ones from SERPENT, considering two representative test cases of (U,Pu)O2 fuel in fast reactor conditions. In addition, a code-to-code comparison is made with the independent state-of-the-art module TUBRNP (implemented in the TRANSURANUS fuel performance code) for the same test cases. The herein presented burn-up module is available in the SCIANTIX code, designed for coupling with fuel performance codes
Consideration of Cr-doped UO2 fuel performance for a Fluoride-Cooled High Temperature Reactor concept
Full text linkThis work follows the AGR-like FHR ongoing research that proposes to adopt the British Advanced Gas cooled Reactor (AGR) geometry combined with the molten salt Fluoride-Cooled High Temperature Reactor (FHR) concept. This work presents the new models and material properties implemented in the TRANSURANUS code for Cr-doped UO2 fuel, which is one of the advanced technology fuels considered for light water reactors. For this purpose, we update the mechanistic model for fission gas behaviour in the code by means of a dedicated fission gas diffusion coefficient recently proposed by Cooper et al. on the basis of atomistic scale simulations to take into consideration the impact of the dopant on the point defects that control the fission gas diffusivity in various temperature regions of interest. In a consistent manner, we propose also a modified creep correlation based on the mechanistic model for standard oxide fuels. Furthermore, we analyse the effect of cracking observed in doped fuels subjected to power ramps and take into consideration the limited densification of the high-density fuel reported in the open literature. A subsequent parametric study pointed out the main factors affecting the integral fission gas release rate, which was shown to be a limiting factor in the AGR-like FHR under consideration. Finally, the improved performance of the advanced technology fuel is shown by means of the reduced inner gas pressure at end of life, as well as the reduced pellet cladding mechanical interaction during the postulated operational transient from the open literature for AGRs. As a result, the doped fuel is shown to be able to sustain higher power levels in the AGR-like FHR
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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