Reflector effective cross sections calculations for GENIII PWR systems

La corretta modellizzazione della zona del riflettore dei sistemi GEN III+ è un passaggio fondamentale per un’accurata predizione dei parametri di cella il cui valore influenza direttamente la distribuzione di potenza su tutto il nocciolo. Tale esigenza si è resa ancora più stringente dopo la constatazione che il fenomeno del “tilt power” risulta essere più amplificato nei noccioli nucleari equipaggiati con un riflettore pesante. Per tali ragioni, nel presente lavoro di tesi si è dedicata particolare attenzione alle metodiche di modellizzazione ed alla generazione delle sezioni d’urto efficaci omogenee ed agli assembly discontinuity factors (ADF) nella zona di riflessione. Il codice deterministico utilizzato per il calcolo è SCALE 6.1.3. La notevole differenza nelle proprietà neutroniche associata ad un’elevata eterogeneità geometrica tra un nocciolo ed un riflettore hanno suggerito di effettuare un’analisi preliminare sul sistema riflettente GEN II proposto nel benchmark NEA-NSC-DOC (2013) per testare la capacità di SCALE 6.1.3 di effettuare un corretto calcolo di cella adottando una modellizzazione monodimensionale assembly/riflettore. I risultati ottenuti sono confrontati con quelli presentati nel benchmark e e con quelli valutati attraverso il codice Monte Carlo SERPENT 2.0 confermando la capacità di calcolo di SCALE 6.1.3. L’analisi sulla modellizzazione dei sistemi riflettenti GEN III+ è stata effettuata ricavando il valore dei parametri di cella per configurazioni omogenee ed una serie di configurazioni geometriche esatte che comprendono tutte le modellizzazioni del sistema riflettente lungo la direzione angolare del riflettore. Si è inoltre effettuata un’analisi di sensitività su parametri operativi e sui parametri di codice. Si è infine effettuato un calcolo in color-set per indagare l’influenza degli effetti 2-D sui parametri di cella. I risultati prodotti rappresentano un contributo migliorativo nella conoscenza dei parametri di cella di riflettore e potranno essere utilizzati per una più precisa valutazione del fenomeno del tilt nei sistemi GEN III+.In GEN III+ systems the correct modelization of the reflector zone is a key step for an exact prediction of the cell parameters whose values directly affect the radial power distribution of the core system. This need has become even more necessary after the discovery of the amplification of the “tilt power” phenomenon in the GEN III+ nuclear core. For this reason, special care is taken in the modelization methodology and in the generation of reflector homogenized cross-section and discontinuity factor (DFs) on the reflector zone. The deterministic package code used for the cell data calculation is SCALE 6.1.3 suite. The strong difference in the neutronic properties at core/reflector interface combined with a high geometric heterogeneity between a core and a reflector system have suggested to perform a preliminary analysis on the GEN II reflector system as presented by NEA-NSC-DOC (2013) benchmark with the aim of testing the capability of the deterministic code to perform a correct calculation on a 1-D assembly/reflector modelization. The results, which are in good agreement with those evaluated with SERPENT 2.0 Monte Carlo code, confirmed the capability of SCALE code to perform cell data reflector calculations. The modelization analysis on the GEN III+ reflector system has been performed for two homogeneous configurations and for a series of exact heterogeneous zones along the angular direction of the reflector. It has been also realized a sensitivity analysis on operational and code parameters. Finally, it was performed a 2x2 color-set calculation to investigate the 2-D geometry effects on the numerical values of cell reflector parameters. The final results are an improvement in the scientific knowledge of the reflector cell data values. These values can be used in a EPR nodal code calculation for a more accurate assessment of the core power distribution and of the “power tilt” values

Reassessment of gadolinium odd isotopes neutron cross sections: scientific motivations and sensitivity-uncertainty analysis on LWR fuel assembly criticality calculations

Gadolinium odd isotopes cross sections are crucial in assessing the neutronic performance and safety features of a light water reactor (LWR) core. Accurate evaluations of the neutron capture behavior of gadolinium burnable poisons are necessary for a precise estimation of the economic gain due to the extension of fuel life, the residual reactivity penalty at the end of life, and the reactivity peak for partially spent fuel for the criticality safety analysis of Spent Fuel Pools. Nevertheless, present gadolinium odd isotopes neutron cross sections are somehow dated and poorly investigated in the high sensitivity thermal energy region and are available with an uncertainty which is too high in comparison to the present day typical industrial standards and needs. This article shows how the most recent gadolinium cross sections evaluations appear inadequate to provide accurate criticality calculations for a system with gadolinium fuel pins. In this article, a sensitivity and uncertainty analysis (S/U) has been performed to investigate the effect of gadolinium odd isotopes nuclear cross sections data on the multiplication factor of some LWR fuel assemblies. The results have shown the importance of gadolinium odd isotopes in the criticality evaluation, and they confirmed the need of a re-evaluation of the neutron capture cross sections by means of new experimental measurements to be carried out at the n_TOF facility at CERN

Multilevel control of an anthropomorphic prosthetic hand for grasp and slip prevention

The success of grasping and manipulation tasks of commercial prosthetic hands is mainly related to amputee visual feedback since they are not provided either with tactile sensors or with sophisticated control. As a consequence, slippage and object falls often occur. This article wants to address the specific issue of enhancing grasping and manipulation capabilities of existing prosthetic hands, by changing the control strategy. For this purpose, it proposes a multilevel control based on two distinct levels consisting of (1) a policy search learning algorithm combined with central pattern generators in the higher level and (2) a parallel force/position control managing slippage events in the lower level. The control has been tested on an anthropomorphic robotic hand with prosthetic features (the IH2 hand) equipped with force sensors. Bi-digital and tri-digital grasping tasks with and without slip information have been carried out. The KUKA-LWR has been employed to perturb the grasp stability inducing controlled slip events. The acquired data demonstrate that the proposed control has the potential to adapt to changes in the environment and guarantees grasp stability, by avoiding object fall thanks to prompt slippage event detection

All-Optical tunability of metalenses infiltrated with liquid crystals

Metasurfaces have been extensively engineered to produce a wide range of optical phenomena, allowing unprecedented control over the propagation of light. However, they are generally designed as single-purpose devices without a modifiable post-fabrication optical response, which can be a limitation to real-world applications. In this work, we report a nanostructured planar fused silica metalens permeated with a nematic liquid crystal (NLC) and gold nanoparticle solution. The physical properties of embedded NLCs can be manipulated with the application of external stimuli, enabling reconfigurable optical metasurfaces. We report all-optical, dynamic control of the metalens optical response resulting from thermo-plasmonic induced changes of the NLC solution associated with the nematic-isotropic phase transition. A continuous and reversible tuning of the metalens focal length is experimentally demonstrated, with a variation of 80 um (0.16% of the 5 cm nominal focal length) along the optical axis. This is achieved without direct mechanical or electrical manipulation of the device. The reconfigurable properties are compared with corroborating numerical simulations of the focal length shift and exhibit close correspondence.Comment: Main tex

Efficacy and safety of once-weekly bortezomib in multiple myeloma patients

AbstractIn a recent phase 3 trial, bortezomib-melphalan-prednisone-thalidomide followed by maintenance treatment with bortezomib-thalidomide demonstrated superior efficacy compared with bortezomib-melphalan-prednisone. To decrease neurologic toxicities, the protocol was amended and patients in both arms received once-weekly instead of the initial twice-weekly bortezomib infusions: 372 patients received once-weekly and 139 twice-weekly bortezomib. In this post-hoc analysis we assessed the impact of the schedule change on clinical outcomes and safety. Long-term outcomes appeared similar: 3-year progression-free survival rate was 50% in the once-weekly and 47% in the twice-weekly group (P > .999), and 3-year overall survival rate was 88% and 89%, respectively (P = .54). The complete response rate was 30% in the once-weekly and 35% in the twice-weekly group (P = .27). Nonhematologic grade 3/4 adverse events were reported in 35% of once-weekly patients and 51% of twice-weekly patients (P = .003). The incidence of grade 3/4 peripheral neuropathy was 8% in the once-weekly and 28% in the twice-weekly group (P < .001); 5% of patients in the once-weekly and 15% in the twice-weekly group discontinued therapy because of peripheral neuropathy (P < .001). This improvement in safety did not appear to affect efficacy. This study is registered at http://www.clinicaltrials.gov as NCT01063179

Prognostic or predictive value of circulating cytokines and angiogenic factors for initial treatment of multiple myeloma in the GIMEMA MM0305 randomized controlled trial

Abstract Background Several new drugs are approved for treatment of patients with multiple myeloma (MM), but no validated biomarkers are available for the prediction of a clinical outcome. We aimed to establish whether pretreatment blood and bone marrow plasma concentrations of major cytokines and angiogenic factors (CAFs) of patients from a phase 3 trial of a MM treatment could have a prognostic and predictive value in terms of response to therapy and progression-free and overall survival and whether these patients could be stratified for their prognosis. Methods Blood and bone marrow plasma levels of Ang-2, FGF-2, HGF, VEGF, PDGF-β, IL-8, TNF-α, TIMP-1, and TIMP-2 were determined at diagnosis in MM patients enrolled in the GIMEMA MM0305 randomized controlled trial by an enzyme-linked immunosorbent assay (ELISA). These levels were correlated both reciprocally and with the type of therapy and patients’ characteristics and with a group of non-MM patients as controls. Results No significant differences were detected between the blood and bone marrow plasma levels of angiogenic cytokines. A cutoff for each CAF was established. The therapeutic response of patients with blood plasma levels of CAFs lower than the cutoff was better than the response of those with higher levels in terms of percentage of responding patients and quality of response. Conclusion FGF-2, HGF, VEGF, and PDGF-β plasma levels at diagnosis have predictive significance for response to treatment. The stratification of patients based on the levels of CAFs at diagnosis and their variations after therapy is useful to characterize different risk groups concerning outcome and response to therapy. Trial registration Clinical trial information can be found at the following link: NCT0106317

TRAM (Transcriptome Mapper): database-driven creation and analysis of transcriptome maps from multiple sources

<p>Abstract</p> <p>Background</p> <p>Several tools have been developed to perform global gene expression profile data analysis, to search for specific chromosomal regions whose features meet defined criteria as well as to study neighbouring gene expression. However, most of these tools are tailored for a specific use in a particular context (e.g. they are species-specific, or limited to a particular data format) and they typically accept only gene lists as input.</p> <p>Results</p> <p>TRAM (Transcriptome Mapper) is a new general tool that allows the simple generation and analysis of quantitative transcriptome maps, starting from any source listing gene expression values for a given gene set (e.g. expression microarrays), implemented as a relational database. It includes a parser able to assign univocal and updated gene symbols to gene identifiers from different data sources. Moreover, TRAM is able to perform intra-sample and inter-sample data normalization, including an original variant of quantile normalization (scaled quantile), useful to normalize data from platforms with highly different numbers of investigated genes. When in 'Map' mode, the software generates a quantitative representation of the transcriptome of a sample (or of a pool of samples) and identifies if segments of defined lengths are over/under-expressed compared to the desired threshold. When in 'Cluster' mode, the software searches for a set of over/under-expressed consecutive genes. Statistical significance for all results is calculated with respect to genes localized on the same chromosome or to all genome genes. Transcriptome maps, showing differential expression between two sample groups, relative to two different biological conditions, may be easily generated. We present the results of a biological model test, based on a meta-analysis comparison between a sample pool of human CD34+ hematopoietic progenitor cells and a sample pool of megakaryocytic cells. Biologically relevant chromosomal segments and gene clusters with differential expression during the differentiation toward megakaryocyte were identified.</p> <p>Conclusions</p> <p>TRAM is designed to create, and statistically analyze, quantitative transcriptome maps, based on gene expression data from multiple sources. The release includes FileMaker Pro database management runtime application and it is freely available at <url>http://apollo11.isto.unibo.it/software/</url>, along with preconfigured implementations for mapping of human, mouse and zebrafish transcriptomes.</p

Cross section measurements of 155,157Gd(n, γ) induced by thermal and epithermal neutrons

Neutron capture cross section measurements on Gd and Gd were performed using the time-of-flight technique at the n_TOF facility at CERN on isotopically enriched samples. The measurements were carried out in the n_TOF experimental area EAR1, at 185 m from the neutron source, with an array of 4 CD liquid scintillation detectors. At a neutron kinetic energy of 0.0253 eV, capture cross sections of 62.2(2.2) and 239.8(8.4) kilobarn have been derived for Gd and Gd, respectively, with up to 6% deviation relative to values presently reported in nuclear data libraries, but consistent with those values within 1.6 standard deviations. A resonance shape analysis has been performed in the resolved resonance region up to 181 eV and 307 eV, respectively for Gd and Gd, where on average, resonance parameters have been found in good agreement with evaluations. Above these energies and up to 1 keV, the observed resonance-like structure of the cross section has been analysed and characterised. From a statistical analysis of the observed neutron resonances we deduced: neutron strength function of 2. 01 (28) × 10 and 2. 17 (41) × 10 ; average total radiative width of 106.8(14) meV and 101.1(20) meV and s-wave resonance spacing 1.6(2) eV and 4.8(5) eV for n + Gd and n + Gd systems, respectively

SCALE 6.1.3 Effective Heavy Reflector Cross Sections Sensitivity Analysis for a PWR GENIII Assembly/Reflector System

This paper presents the results of a sensitivity analysis on code and operational parameters for the evaluation of the effective cross sections of a central assembly/heavy reflector GENIII PWR system. The methodology used for the calculation is based on the T- NEWT control module of SCALE 6.1.3 package. In detail, the sensitivity analysis on the heavy reflector cross sections has been performed on the following set of code parameters: reflector zone computational meshes, Sn and Pm transport parameter, cross sections libraries and convergence parameters (eigenvalue and eigenfunction). It also has been carried out a series of calculations on a set of operational parameters such as: boron concentration (0 and 1300 ppm), operational condition (HZP and HFP) and reflector temperature (Tmax and Tmod)