1,721,005 research outputs found
Sensitivity of the neutron multiplication factor to gadolinium isotopes' nuclear data for light water reactor fuel assemblies in the peak reactivity burnup range
Get PDFThe reactivity of a fuel assembly including burnable absorbers can become the largest at low fuel burnup, so the accuracy of reactivity calculations for such systems is important. To investigate this issue, the impact of gadolinium isotopes' nuclear data on neutron multiplication factor k is quantified. Sensitivities of k to nuclear data are calculated from 0 to 20 GWD/t for a BWR 3 x 3 multicell model. Sensitivity to gadolinium-157 (n, gamma) cross section becomes the largest at the zero burnup. Sensitivity to gadolinium-155 (n, gamma) cross sections takes the two largest values and the second one is observed around fuel burnup where the reactivity reaches its peak. Sensitivities are also calculated for BWR and PWR assemblies, and similar trends are observed. Finally, nuclear data-induced uncertainties of k are quantified. Gadolinium-157 contribution is the largest at zero burnup, and gadolinium-155 contribution is relatively important around fuel burnup corresponding to the reactivity peak
Consistent adjustment of radioactive decay and fission yields data with measurement data of decay heat and beta-delayed neutron activities
Get PDFDecay heat and delayed neutron yields, which are important physical quantities in the field of the nuclear engineering, are dependent on common nuclear data such as radioactive decay data and fission yields data of fission product nuclides. In the present study, correlations between uncertainties of these two quantities are investigated. Nuclear data relevant to uranium-235 and plutonium-239 fissions with thermal neutron are adjusted consistently with a procedure based on Bayes' theorem using the measurement data of decay heat and delayed neutron activities. Numerical results suggest that the correlation between decay heat and delayed neutron activities uncertainties is not significant, and that independent treatments of decay heat or delayed neutron activities are possible. The effect of the consistent treatment of decay heat and delayed neutron activities is, however, observed in the adjustment results in some nuclear data such as uranium-235 thermal fission yields of yttrium-100m and zirconium-100
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
Combination of sensitivity-based and random sampling-based methodologies for efficient uncertainty quantification calculations with control variates method
Get PDFA combined method of the sensitivity-based and random sampling-based methodologies is proposed for efficient uncertainty quantification calculations. The proposed method is based on the control variates (CV) method, in which a mean value of a target parameter can be estimated efficiently with a help of a mockup parameter whose mean value is well known. Standard deviations can be also efficiently estimated from two mean values of stochastic parameters; a target parameter itself and its square. In the present work, the CV method is applied to a toy problem, in which a linear approximation to a target parameter is regarded as a mockup parameter. This case corresponds to our proposed method to combine the sensitivity-based and random sampling-based methodologies. Numerical results reveal that the proposed method efficiently works. As a preliminary test of application of our proposed method to realistic problems, nuclear fuel burnup calculations are considered, and uncertainties of nuclides number densities after burnup are calculated. Uncertainties of number densities of cesium-134 and europium-151 are calculated by the proposed method, and it is demonstrated that we can carry out uncertainty quantification calculations more efficiently with our proposed method than with the normal random sampling method
Quantification of integral data effectiveness using the concept of active subspace in evaluated nuclear data validation
Get PDFIn order to know the performance of evaluated nuclear data in reactor physics or radiation shielding calculations, its benchmark testing with integral data is mandatory. Nowadays we have a huge amount of integral data, but some of them are quite similar to each other. We need to know the independency of available integral data, and also to choose a proper set of a limited number of integral data for benchmark calculations. Furthermore, it is beneficial to know how effective a set of integral data is for independent validation of each nuclear data in performing the validation test of nuclear data. In order to quantify the effectiveness of integral data in nuclear data validation, we propose several methods based on a concept of the active subspace. With the proposed methods, we can quantify the independency of a set of integral data, choose a minimum set of proper integral data, and quantify the possibility of independent validation of nuclear data from a set of integral data. These methods are adopted to a set of fictitious integral data and a set of actual integral data including experimental data aboutand reaction rate ratio. Through these applications, effectiveness of these integral data has been successfully quantified. Furthermore, the proposed concept is utilized to interpret the nuclear data compensation effect, which has been recently discussed in the community of nuclear data
Feasibility study of decay heat uncertainty reduction using nuclear data adjustment method with experimental data
Get PDFThe accurate prediction of the decay heat is essential, especially for nuclear power plant safety purposes. However, it is known that the decay heat predicted by nuclear fuel burn-up calculations is uncertain because of uncertainty of nuclear data employed in the calculations. If the decay heat uncertainty can be reduced, the safety margin of the predicted decay heat can also be reduced, and feasible design ranges of various types of equipments related to the decay heat can be extended. In the present study, we use the nuclear data adjustment method for the decay heat uncertainty reduction with several types of the experimental data. As a result, we clarify that the decay heat uncertainty with short- and long-term cooling periods can be reduced by this method with appropriate experimental data
Enhancement of applicability of high-efficiency random sampling method using control variates method and sensitivity coefficients
Get PDFThe CV-S method is a high-efficiency random sampling method to estimate statistical moments of random variables, and it uses an approximated target parameter which are linearly dependent on input as a mockup parameter. In order to enhance the applicability of the CV-S method, we propose to use a mockup parameter which is different from but similar to a target parameter and whose sensitivity coefficients are available. In the present work, nuclear fuel burnup problems are concerned, and standard deviation of k infinity and nuclide number densities at certain fuel burnup are estimated by the CV-S method. Through numerical tests, it is clearly demonstrated that even if sensitivity coefficients of non burnup-related parameters in a simple system like a fuel pin-cell are used as the mockup, the CV-S method has a potential to efficiently estimate statistical moments of burnup-related parameters in a complicated system like a fuel assembly
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