Propagation of Neutron Cross Section, Fission Yield, and Decay Data Uncertainties in Depletion Calculations

Propagation of nuclear data uncertainties in reactor calculations is interesting for design purposes and libraries evaluation. Previous versions of the GRS XSUSA library propagated only neutron cross section uncertainties. We have extended XSUSA uncertainty assessment capabilities by including propagation of fission yields and decay data uncertainties due to the their relevance in depletion simulations. We apply this extended methodology to the UAM6 PWR Pin-Cell Burnup Benchmark, which involves uncertainty propagation through burnup.

Analysis of calibration results from cup and propeller anemometers. Influence on wind turbine Annual Energy Production (AEP) calculations

The calibration coefficients of several models of cup and propeller anemometers were analysed. The analysis was based on a series of laboratory calibrations between January 2003 and August 2007. Mean and standard deviation values of calibration coefficients from the anemometers studied were included. Two calibration procedures were used and compared. In the first, recommended by the Measuring network of Wind Energy Institutes (MEASNET), 13 measurement points were taken over a wind speed range of 4 to 16  m  s−1. In the second procedure, 9 measurement points were taken over a wider speed range of 4 to 23  m  s−1. Results indicated no significant differences between the two calibration procedures applied to the same anemometer in terms of measured wind speed and wind turbines' Annual Energy Production (AEP). The influence of the cup anemometers' design on the calibration coefficients was also analysed. The results revealed that the slope of the calibration curve, if based on the rotation frequency and not the anemometer's output frequency, seemed to depend on the cup center rotation radius.

Development of a methodology for nuclear data uncertainty propagation on isotopic evolution calculations for advanced nuclear systems

Una apropiada evaluación de los márgenes de seguridad de una instalación nuclear, por ejemplo, una central nuclear, tiene en cuenta todas las incertidumbres que afectan a los cálculos de diseño, funcionanmiento y respuesta ante accidentes de dicha instalación. Una fuente de incertidumbre son los datos nucleares, que afectan a los cálculos neutrónicos, de quemado de combustible o activación de materiales. Estos cálculos permiten la evaluación de las funciones respuesta esenciales para el funcionamiento correcto durante operación, y también durante accidente. Ejemplos de esas respuestas son el factor de multiplicación neutrónica o el calor residual después del disparo del reactor. Por tanto, es necesario evaluar el impacto de dichas incertidumbres en estos cálculos. Para poder realizar los cálculos de propagación de incertidumbres, es necesario implementar metodologías que sean capaces de evaluar el impacto de las incertidumbres de estos datos nucleares. Pero también es necesario conocer los datos de incertidumbres disponibles para ser capaces de manejarlos. Actualmente, se están invirtiendo grandes esfuerzos en mejorar la capacidad de analizar, manejar y producir datos de incertidumbres, en especial para isótopos importantes en reactores avanzados. A su vez, nuevos programas/códigos están siendo desarrollados e implementados para poder usar dichos datos y analizar su impacto. Todos estos puntos son parte de los objetivos del proyecto europeo ANDES, el cual ha dado el marco de trabajo para el desarrollo de esta tesis doctoral. Por tanto, primero se ha llevado a cabo una revisión del estado del arte de los datos nucleares y sus incertidumbres, centrándose en los tres tipos de datos: de decaimiento, de rendimientos de fisión y de secciones eficaces. A su vez, se ha realizado una revisión del estado del arte de las metodologías para la propagación de incertidumbre de estos datos nucleares. Dentro del Departamento de Ingeniería Nuclear (DIN) se propuso una metodología para la propagación de incertidumbres en cálculos de evolución isotópica, el Método Híbrido. Esta metodología se ha tomado como punto de partida para esta tesis, implementando y desarrollando dicha metodología, así como extendiendo sus capacidades. Se han analizado sus ventajas, inconvenientes y limitaciones. El Método Híbrido se utiliza en conjunto con el código de evolución isotópica ACAB, y se basa en el muestreo por Monte Carlo de los datos nucleares con incertidumbre. En esta metodología, se presentan diferentes aproximaciones según la estructura de grupos de energía de las secciones eficaces: en un grupo, en un grupo con muestreo correlacionado y en multigrupos. Se han desarrollado diferentes secuencias para usar distintas librerías de datos nucleares almacenadas en diferentes formatos: ENDF-6 (para las librerías evaluadas), COVERX (para las librerías en multigrupos de SCALE) y EAF (para las librerías de activación). Gracias a la revisión del estado del arte de los datos nucleares de los rendimientos de fisión se ha identificado la falta de una información sobre sus incertidumbres, en concreto, de matrices de covarianza completas. Además, visto el renovado interés por parte de la comunidad internacional, a través del grupo de trabajo internacional de cooperación para evaluación de datos nucleares (WPEC) dedicado a la evaluación de las necesidades de mejora de datos nucleares mediante el subgrupo 37 (SG37), se ha llevado a cabo una revisión de las metodologías para generar datos de covarianza. Se ha seleccionando la actualización Bayesiana/GLS para su implementación, y de esta forma, dar una respuesta a dicha falta de matrices completas para rendimientos de fisión. Una vez que el Método Híbrido ha sido implementado, desarrollado y extendido, junto con la capacidad de generar matrices de covarianza completas para los rendimientos de fisión, se han estudiado diferentes aplicaciones nucleares. Primero, se estudia el calor residual tras un pulso de fisión, debido a su importancia para cualquier evento después de la parada/disparo del reactor. Además, se trata de un ejercicio claro para ver la importancia de las incertidumbres de datos de decaimiento y de rendimientos de fisión junto con las nuevas matrices completas de covarianza. Se han estudiado dos ciclos de combustible de reactores avanzados: el de la instalación europea para transmutación industrial (EFIT) y el del reactor rápido de sodio europeo (ESFR), en los cuales se han analizado el impacto de las incertidumbres de los datos nucleares en la composición isotópica, calor residual y radiotoxicidad. Se han utilizado diferentes librerías de datos nucleares en los estudios antreriores, comparando de esta forma el impacto de sus incertidumbres. A su vez, mediante dichos estudios, se han comparando las distintas aproximaciones del Método Híbrido y otras metodologías para la porpagación de incertidumbres de datos nucleares: Total Monte Carlo (TMC), desarrollada en NRG por A.J. Koning y D. Rochman, y NUDUNA, desarrollada en AREVA GmbH por O. Buss y A. Hoefer. Estas comparaciones demostrarán las ventajas del Método Híbrido, además de revelar sus limitaciones y su rango de aplicación. ABSTRACT For an adequate assessment of safety margins of nuclear facilities, e.g. nuclear power plants, it is necessary to consider all possible uncertainties that affect their design, performance and possible accidents. Nuclear data are a source of uncertainty that are involved in neutronics, fuel depletion and activation calculations. These calculations can predict critical response functions during operation and in the event of accident, such as decay heat and neutron multiplication factor. Thus, the impact of nuclear data uncertainties on these response functions needs to be addressed for a proper evaluation of the safety margins. Methodologies for performing uncertainty propagation calculations need to be implemented in order to analyse the impact of nuclear data uncertainties. Nevertheless, it is necessary to understand the current status of nuclear data and their uncertainties, in order to be able to handle this type of data. Great eórts are underway to enhance the European capability to analyse/process/produce covariance data, especially for isotopes which are of importance for advanced reactors. At the same time, new methodologies/codes are being developed and implemented for using and evaluating the impact of uncertainty data. These were the objectives of the European ANDES (Accurate Nuclear Data for nuclear Energy Sustainability) project, which provided a framework for the development of this PhD Thesis. Accordingly, first a review of the state-of-the-art of nuclear data and their uncertainties is conducted, focusing on the three kinds of data: decay, fission yields and cross sections. A review of the current methodologies for propagating nuclear data uncertainties is also performed. The Nuclear Engineering Department of UPM has proposed a methodology for propagating uncertainties in depletion calculations, the Hybrid Method, which has been taken as the starting point of this thesis. This methodology has been implemented, developed and extended, and its advantages, drawbacks and limitations have been analysed. It is used in conjunction with the ACAB depletion code, and is based on Monte Carlo sampling of variables with uncertainties. Different approaches are presented depending on cross section energy-structure: one-group, one-group with correlated sampling and multi-group. Differences and applicability criteria are presented. Sequences have been developed for using different nuclear data libraries in different storing-formats: ENDF-6 (for evaluated libraries) and COVERX (for multi-group libraries of SCALE), as well as EAF format (for activation libraries). A revision of the state-of-the-art of fission yield data shows inconsistencies in uncertainty data, specifically with regard to complete covariance matrices. Furthermore, the international community has expressed a renewed interest in the issue through the Working Party on International Nuclear Data Evaluation Co-operation (WPEC) with the Subgroup (SG37), which is dedicated to assessing the need to have complete nuclear data. This gives rise to this review of the state-of-the-art of methodologies for generating covariance data for fission yields. Bayesian/generalised least square (GLS) updating sequence has been selected and implemented to answer to this need. Once the Hybrid Method has been implemented, developed and extended, along with fission yield covariance generation capability, different applications are studied. The Fission Pulse Decay Heat problem is tackled first because of its importance during events after shutdown and because it is a clean exercise for showing the impact and importance of decay and fission yield data uncertainties in conjunction with the new covariance data. Two fuel cycles of advanced reactors are studied: the European Facility for Industrial Transmutation (EFIT) and the European Sodium Fast Reactor (ESFR), and response function uncertainties such as isotopic composition, decay heat and radiotoxicity are addressed. Different nuclear data libraries are used and compared. These applications serve as frameworks for comparing the different approaches of the Hybrid Method, and also for comparing with other methodologies: Total Monte Carlo (TMC), developed at NRG by A.J. Koning and D. Rochman, and NUDUNA, developed at AREVA GmbH by O. Buss and A. Hoefer. These comparisons reveal the advantages, limitations and the range of application of the Hybrid Method.

Source terms for calculations of vaporizing and burning fuel sprays with non-unity Lewis numbers in gases with temperature-dependent thermal conductivities

Liquid-fueled burners are used in a number of propulsion devices ranging from internal combustion engines to gas turbines. The structure of spray flames is quite complex and involves a wide range of time and spatial scales in both premixed and non-premixed modes (Williams 1965; Luo et al. 2011). A number of spray-combustion regimes can be observed experimentally in canonical scenarios of practical relevance such as counterflow diffusion flames (Li 1997), as sketched in figure 1, and for which different microscalemodelling strategies are needed. In this study, source terms for the conservation equations are calculated for heating, vaporizing and burning sprays in the single-droplet combustion regime. The present analysis provides extended formulation for source terms, which include non-unity Lewis numbers and variable thermal conductivities.

Optimization of multidimensional cross-section tables for few-group core calculations

Multigroup diffusion codes for three dimensional LWR core analysis use as input data pre-generated homogenized few group cross sections and discontinuity factors for certain combinations of state variables, such as temperatures or densities. The simplest way of compiling those data are tabulated libraries, where a grid covering the domain of state variables is defined and the homogenized cross sections are computed at the grid points. Then, during the core calculation, an interpolation algorithm is used to compute the cross sections from the table values. Since interpolation errors depend on the distance between the grid points, a determined refinement of the mesh is required to reach a target accuracy, which could lead to large data storage volume and a large number of lattice transport calculations. In this paper, a simple and effective procedure to optimize the distribution of grid points for tabulated libraries is presented. Optimality is considered in the sense of building a non-uniform point distribution with the minimum number of grid points for each state variable satisfying a given target accuracy in k-effective. The procedure consists of determining the sensitivity coefficients of k-effective to cross sections using perturbation theory; and estimating the interpolation errors committed with different mesh steps for each state variable. These results allow evaluating the influence of interpolation errors of each cross section on k-effective for any combination of state variables, and estimating the optimal distance between grid points.

Four-Band Hamiltonian for fast calculations in intermediate-band solar cells

The 8-dimensional Luttinger–Kohn–Pikus–Bir Hamiltonian matrix may be made up of four 4-dimensional blocks. A 4-band Hamiltonian is presented, obtained from making the non-diagonal blocks zero. The parameters of the new Hamiltonian are adjusted to fit the calculated effective masses and strained QD bandgap with the measured ones. The 4-dimensional Hamiltonian thus obtained agrees well with measured quantum efficiency of a quantum dot intermediate band solar cell and the full absorption spectrum can be calculated in about two hours using Mathematica© and a notebook. This is a hundred times faster than with the commonly-used 8-band Hamiltonian and is considered suitable for helping design engineers in the development of nanostructured solar cells.

Analysis by finite element calculations of light scattering in laser-textured AZO films for PV thin-film solar cells

In the thin-film photovoltaic industry, to achieve a high light scattering in one or more of the cell interfaces is one of the strategies that allow an enhancement of light absorption inside the cell and, therefore, a better device behavior and efficiency. Although chemical etching is the standard method to texture surfaces for that scattering improvement, laser light has shown as a new way for texturizing different materials, maintaining a good control of the final topography with a unique, clean, and quite precise process. In this work AZO films with different texture parameters are fabricated. The typical parameters used to characterize them, as the root mean square roughness or the haze factor, are discussed and, for deeper understanding of the scattering mechanisms, the light behavior in the films is simulated using a finite element method code. This method gives information about the light intensity in each point of the system, allowing the precise characterization of the scattering behavior near the film surface, and it can be used as well to calculate a simulated haze factor that can be compared with experimental measurements. A discussion of the validation of the numerical code, based in a comprehensive comparison with experimental data is included.

Molecular dynamics and free-energy calculations applied to affinity maturation in antibody 48G7

We investigated the relative free energies of hapten binding to the germ line and mature forms of the 48G7 antibody Fab fragments by applying a continuum model to structures sampled from molecular dynamics simulations in explicit solvent. Reasonable absolute and very good relative free energies were obtained. As a result of nine somatic mutations that do not contact the hapten, the affinity-matured antibody binds the hapten >104 tighter than the germ line antibody. Energetic analysis reveals that van der Waals interactions and nonpolar contributions to solvation are similar and drive the formations of both the germ line and mature antibody–hapten complexes. Affinity maturation of the 48G7 antibody therefore appears to occur through reorganization of the combining site geometry in a manner that optimizes the balance of gaining favorable electrostatic interactions with the hapten and losing those with solvent during the binding process. As reflected by lower rms fluctuations in the antibody–hapten complex, the mature complex undergoes more restricted fluctuations than the germ line complex. The dramatically increased affinity of the 48G7 antibody over its germ line precursor is thus made possible by electrostatic optimization.

Extraterrestrial amino acids in Orgueil and Ivuna: Tracing the parent body of CI type carbonaceous chondrites

Amino acid analyses using HPLC of pristine interior pieces of the CI carbonaceous chondrites Orgueil and Ivuna have found that β-alanine, glycine, and γ-amino-n-butyric acid (ABA) are the most abundant amino acids in these two meteorites, with concentrations ranging from ≈600 to 2,000 parts per billion (ppb). Other α-amino acids such as alanine, α-ABA, α-aminoisobutyric acid (AIB), and isovaline are present only in trace amounts (<200 ppb). Carbon isotopic measurements of β-alanine and glycine and the presence of racemic (D/L ≈ 1) alanine and β-ABA in Orgueil suggest that these amino acids are extraterrestrial in origin. In comparison to the CM carbonaceous chondrites Murchison and Murray, the amino acid composition of the CIs is strikingly distinct, suggesting that these meteorites came from a different type of parent body, possibly an extinct comet, than did the CM carbonaceous chondrites.

Molecular mechanics calculations of the riboacetal internucleotide linkage in double and triple helices.

Structures of Watson-Crick base paired 15-nucleobase oligomer strands in A-type or B-type conformation in which one strand [a strand of alternating nucleotide and riboacetal thymidine nucleoside (RT) units, RP] is DNA and the other is composed of alternating nucleotides and riboacetal nucleosides have been studied by molecular mechanics. Analogously, oligomer strands of RNA in place of DNA have been modeled. The calculations indicate that the RP strand is more stable when complexed in an A-type duplex relative to a B-type form and that this conformational preference is presumably due to the more uniform nature of the former. Nearly planar ribose rings were more commonly observed in the minimized structures of the B-type DNA.RP duplexes as compared with A-type duplexes, despite the fact that planar ribofuranose rings are known to be energetically unfavorable in oligonucleotides. Computed relative stabilities of all duplexes containing the RP strand suggest that such heteroduplexes are less stable than the corresponding double-stranded DNA and double-stranded RNA species. These findings are in agreement with experimental results which show, when equivalent sequences were compared, that a DNA.RNA control forms a more stable duplex than RP hound to a complementary single-stranded RNA strand. In contrast, molecular mechanics studies of complementary triple-helical (DNA)2.RP, (DNA)2.DNA, and (DNA)2.RNA structures indicate that the binding of RP as a Hoogsteen strand stabilizes the underlying duplex to a greater extent compared with native oligonucleotides. These calculations suggest that puckering of the ribose ring in the riboacetal linkage leads to a more favorable interaction with a complementary nucleic acid target than the proposed planar geometry and that this puckering may account for the enhanced binding of RP to a double-stranded target.

Expression cloning of dSR-CI, a class C macrophage-specific scavenger receptor from Drosophila melanogaster.

Mammalian class A macrophage-specific scavenger receptors (SR-A) exhibit unusually broad binding specificity for a wide variety of polyanionic ligands. The properties of these receptors suggest that they may be involved in atherosclerosis and host defense. We have previously observed a similar receptor activity in Drosophila melanogaster embryonic macrophages and in the Drosophila macrophage-like Schneider L2 cell line. Expression cloning was used to isolate from L2 cells a cDNA that encodes a third class (class C) of scavenger receptor, Drosophila SR-CI (dSR-CI). dSR-CI expression was restricted to macrophages/hemocytes during embryonic development. When expressed in mammalian cells, dSR-CI exhibited high affinity and saturable binding of 125I-labeled acetylated low density lipoprotein and mediated its chloroquine-dependent, presumably lysosomal, degradation. Although the broad polyanionic ligand-binding specificity of dSR-CI was similar to that of SR-A, their predicted protein sequences are not similar. dSR-CI is a 609-residue type I integral membrane protein containing several well-known sequence motifs, including two complement control protein (CCP) domains and somatomedin B, MAM, and mucin-like domains. Macrophage scavenger receptors apparently mediate important, well-conserved functions and may be pattern-recognition receptors that arose early in the evolution of host-defense mechanisms. Genetic and physiologic analysis of dSR-CI function in Drosophila should provide further insights into the roles played by scavenger receptors in host defense and development.

Prevalência e incidência de obesidade sarcopênica em coorte de idosos domiciliados no município de São Paulo

Introdução: Evidências epidemiológicas mostram que a obesidade sarcopênica (OS) em idosos está associada a um acelerado declínio funcional e alto risco de morbimortalidade, sendo que seu impacto tem se tornado grande preocupação dos profissionais de saúde. Objetivo: Estimar a prevalência e a incidência de obesidade sarcopênica, em coorte de idosos domiciliados no município de São Paulo/Brasil 2000 e 2010. Casuística e Métodos: Foram utilizados dados do Estudo SABE (Saúde, Bem-estar e Envelhecimento), realizado no município de São Paulo em 2000 (2.143 idosos), e em 2010 (795 idosos). A população deste estudo foi constituída por idosos ( 70 anos), de ambos os sexos, que apresentaram todos os dados necessários para este estudo e que concordaram em participar, totalizando 871 idosos analisados em 2000 e 656 idosos em 2010. As variáveis de estudo foram: 1. Dependente - obesidade sarcopênica, identificada segundo: obesidade, diagnosticada pelo valor da circunferência da cintura (CC 94 cm e CC 80 cm para homens e mulheres, respectivamente); sarcopenia, identificada por: 1- força muscular, pelo teste de preensão manual (FPM - kg) (baixa P25; normal > P25, da mesma população), 2- massa muscular (MM), obtida pelo índice de massa muscular (IMM=MM/altura²) (baixa P20; normal > P20, da mesma população) e 3- desempenho físico, identificado pelo teste (tempo dependente segundos) de sentar e levantar 5 vezes de uma cadeira (SeL) , com os braços cruzados sobre o peito (baixo P75; normal < P75); 2. Explanatórias - sexo e grupos etários (70 79 e 80). Foram classificados com OS idosos que apresentaram, simultaneamente, valores de CC adotados e baixo desempenho e baixa MM, ou então, desempenho normal, mas baixas FPM e MM. A prevalência de obesidade sarcopênica em 2000 e em 2010 foi estimada pelo número de casos de OS identificados nos dois momentos, onde foram realizadas comparações entre os intervalos de confiança, para verificar diferença estatística em idosos ( por cento ) com OS, segundo variáveis explanatórias, com nível de significância de 5 por cento . Para o cálculo do coeficiente de incidência de OS, em 2010, foi considerado o tempo de observação de cada indivíduo, determinado de maneira específica para cada caso. Para os cálculos foi utilizado o programa: Stata/SE ® 10.0 for Windows. Resultados: Dos 871 idosos analisados em 2000, 85 (7,4 por cento ) foram identificados com OS [6,5 por cento mulheres (IC 5,08,4) e 4,8 por cento 80 anos (IC 3,6-6,4)] (p 5 por cento ), e, em 2010, (n=656), 73 (9,2 por cento ) foram identificados com OS [7,2 por cento mulheres (IC 5,5-9,4) e 5,3 por cento 80 anos (IC 4,0-7,0)] (p 5 por cento ). Em 10 anos, foram identificados 43 novos casos de OS. O coeficiente de incidência foi 15,29/1000 pessoas/ano entre 2000 e 2010. Conclusões: A prevalência de OS em 2000 e 2010 foi maior nas mulheres e nos idosos mais longevos, sendo que, em ambos os casos, foi maior em 2010, quando comparada a 2000. Não houve diferença significativa entre os coeficientes de incidência, segundo as variáveis explanatórias.

Some examples of modeling in chemical engineering: thermal treatment of polymers, phase equilibrium calculations and process design

Presentation submitted to PSE Seminar, Chemical Engineering Department, Center for Advanced Process Design-making (CAPD), Carnegie Mellon University, Pittsburgh (USA), October 2012.

Emergence of half-metallicity in suspended NiO chains: Ab initio electronic structure and quantum transport calculations

Contrary to the antiferromagnetic and insulating character of bulk NiO, one-dimensional chains of this material can become half metallic due to the lower coordination of their atoms. Here we present ab initio electronic structure and quantum transport calculations of ideal infinitely long NiO chains and of more realistic short ones suspended between Ni electrodes. While infinite chains are insulating, short suspended chains are half-metallic minority-spin conductors that displays very large magnetoresistance and a spin-valve behavior controlled by a single atom.

Improvements in DFT Calculations of Spin–Spin Coupling Constants

Different types of spin–spin coupling constants (SSCCs) for several representative small molecules are evaluated and analyzed using a combination of 10 exchange functionals with 12 correlation functionals. For comparison, calculations performed using MCSCF, SOPPA, other common DFT methods, and also experimental data are considered. A detailed study of the percentage of Hartree–Fock exchange energy in SSCCs and in its four contributions is carried out. From the above analysis, a combined functional formed with local Slater (34%), Hartree–Fock exchange (66%), and P86 correlation functional (S66P86) is proposed in this paper. The accuracy of the values obtained with this hybrid functional (mean absolute deviation of 4.5 Hz) is similar to that of the SOPPA method (mean absolute deviation of 4.6 Hz).