Iron-chromium-aluminum (FeCrAl) alloys are candidates to be used as nuclear fuel cladding for increased accident tolerance. An analysis of the response of FeCrAl under normal operating and loss of ...coolant conditions has been performed using fuel performance modeling. In particular, recent information on FeCrAl material properties and phenomena from separate effects tests has been implemented in the BISON fuel performance code and analyses of integral fuel rod behavior with FeCrAl cladding have been performed. BISON simulations included both light water reactor normal operation and loss-of-coolant accidental transients. In order to model fuel rod behavior during accidents, a cladding failure criterion is desirable. For FeCrAl alloys, a failure criterion is developed using recent burst experiments under loss of coolant like conditions. The added material models are utilized to perform comparative studies with Zircaloy-4 under normal operating conditions and oxidizing and non-oxidizing out-of-pile loss of coolant conditions. The results indicate that for all conditions studied, FeCrAl behaves similarly to Zircaloy-4 with the exception of improved oxidation performance. Further experiments are required to confirm these observations.
•Material and behavior models for FeCrAl have been added to the BISON fuel performance code.•A failure criterion for FeCrAl alloys has been developed.•Under normal operation FeCrAl performs as well as Zircaloy-4 with improved oxidation kinetics.•First generation FeCrAl alloys have similar burst behavior as Zircaloy-4.
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► Antioxidant potential and antiproliferative effect of five monoterpenes was investigated. ► α-Terpineol presented good antioxidant activity in ORAC test. ► Limonene and α-terpineol presented ...equivalent antiproliferative profile in vitro. ► α-Terpineol had encouraging results against breast carcinoma and chronic myeloid leukemia. ► In vivo assays must be performed to confirm the anti-tumor potential of α-terpineol.
α-Terpineol is a relatively cheap and abundant aroma compound. It is widely used in food, cosmetics, and household products. Many of its monoterpene counterparts have been applied in antiproliferative assays, leading to promising results in the prevention or even treatment of cancers. However, despite its theoretic potential, no paper reports the evaluation of antiproliferative capacity of this alcohol. Thus, antioxidant potential of three monoterpenoids (carvone, perillyl alcohol, and α-terpineol) was measured using two methods: DPPH and ORAC. Also, the antiproliferative effect of these monoterpenoids against nine cancerous cell lines were performed and compared to limonene and doxorubicin. Results showed that all samples tested had very low antioxidant activity in the DPPH assay, but α-terpineol (2.72μmolTrolox equiv./μmol) could be compared to commercial antioxidants in the ORAC assay. The antiproliferative results obtained encourage future in vivo studies for α-terpineol, since this monoterpenoid presented cytostatic effect against six cell lines, especially for breast adenocarcinoma and chronic myeloid leukemia, in a range of 181–588μM.
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Wrinkles in supported graphenes can be formed either by uniaxial compression or uniaxial tension beyond a certain critical load depending on the mode of loading. In the first case, the wrinkling ...direction is normal to the compression axis whereas in tension, wrinkles of the same pattern are formed parallel to the loading direction due to Poisson's (lateral) contraction. Herein we show by direct AFM observations that in simply-supported graphenes such instabilities appear as periodic wrinkles over existing stochastic undulations caused by the underlying-substrate-roughness. The critical strain for the generation of these wrinkles in both tension and compression is less than 1% which particularly for the former is far lower than the predicted tensile strain to fracture of suspended graphene estimated at ∼30%. Based on these findings, a constitutive model that provides the critical tensile strain for induced buckling in the lateral direction is proposed that depends only on the graphene-support interaction and not on the nature of the substrate. Understanding the wrinkling failure of graphenes under strain is of paramount importance as it leads to new threshold limits beyond which the physical-mechanical properties of graphene are impaired.
The knowledge of the mechanism of stress transfer from a polymer matrix to a 2-dimensional nano-inclusion such as a graphene flake is of paramount importance for the design and the production of ...effective nanocomposites. For efficient reinforcement the shape of the inclusion must be accurately controlled since the axial stress transfer from matrix to the inclusion is affected by the axial-shear coupling observed upon loading of a flake of irregular geometry. Herein, we study true axial phenomena on regular- exfoliated-graphene micro-ribbons which are perfectly aligned to the loading direction. We exploit the strain sensitivity of vibrational wave numbers in order to map point-by-point the strain built up along the length of graphene. By considering the balance of shear-to-axial forces, we identify the shear stress at the interface and develop a universal inverse-length parameter that governs the stress transfer process at the nanoscale. An important parameter that has come out of this approach is the prediction and measurement of the transfer length that is required for efficient stress in these systems.
Experimental and theoretical investigation of true axial stress transfer on regular-exfoliated-graphene micro-ribbons which are aligned to the loading direction.
We propose a model describing the HBS formation and the progressive intra-granular xenon depletion in UO2. The HBS formation is modeled employing the Kolmogorov-Johnson-Mehl-Avrami (KJMA) formalism ...for phase transformations, which has been fitted to experimental data on the restructured volumetric fraction as a function of the local effective burnup. To this end, we employed available experimental data and novel data extracted in this work. The HBS formation model is coupled to a description of the intra-granular fission gas behavior, allowing to estimate the evolution of the retained xenon in order to consistently compute fission gas retention and its effect on the fuel matrix swelling. The satisfactory agreement of the model predictions to experimental data and state-of-the-art models’ results, in terms of both xenon depletion and fuel matrix swelling as a function of the local burnup, paves the way to the inclusion of the model in fuel performance codes.
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Long-lived excitons formed upon visible light absorption play an essential role in photovoltaics, photocatalysis, and even in high-density information storage. Here, we describe a self-assembled ...two-dimensional metal-organic crystal, composed of graphene-supported macrocycles, each hosting a single FeN
center, where a single carbon monoxide molecule can adsorb. In this heme-like biomimetic model system, excitons are generated by visible laser light upon a spin transition associated with the layer 2D crystallinity, and are simultaneously detected via the carbon monoxide ligand stretching mode at room temperature and near-ambient pressure. The proposed mechanism is supported by the results of infrared and time-resolved pump-probe spectroscopies, and by ab initio theoretical methods, opening a path towards the handling of exciton dynamics on 2D biomimetic crystals.
The description of intra-granular fission gas behavior during irradiation is a fundamental part of models used for the calculation of fission gas release and gaseous swelling in nuclear fuel ...performance codes. The relevant phenomena include diffusion of gas atoms towards the grain boundaries coupled to the evolution of intra-granular bubbles. While intra-granular bubbles during normal operating conditions are limited to sizes of a few nanometers, experimental evidence exists for the appearance of a second population of bubbles during transients, characterized by coarsening to sizes of tens to hundreds of nanometers and that can significantly contribute to gaseous fuel swelling. In this work, we present a model of intra-granular fission gas behavior in uranium dioxide fuel that includes both nanometric fission gas bubble evolution and bubble coarsening during transients. While retaining a physical basis, the developed model is relatively simple and is intended for application in engineering fuel performance codes. We assess the model through comparisons to a substantial number of experimental data from SEM observations of intra-granular bubbles in power ramp tested uranium dioxide samples. The results demonstrate that the model reproduces the coarsening of a fraction of the intra-granular bubbles and correspondingly, predicts gaseous swelling during power ramps with a significantly higher accuracy than is allowed by traditional models limited to the evolution of nanometric intra-granular bubbles.
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Modeling chronic oil pollution from ships Liubartseva, S.; Coppini, G.; Verdiani, G. ...
Marine pollution bulletin,
October 2023, 2023-10-00, 20231001, Volume:
195
Journal Article
Peer reviewed
Open access
Stochastic simulations of virtual oil spills from ships were performed for the Adriatic Sea over 2017–2020, applying the European Marine Observation and Data Network vessel densities as a proxy for ...starting locations of operational spillage. The MEDSLIK-II oil spill model was run using high-resolution currents provided by the Copernicus Marine Service and the European Centre for Medium-Range Weather Forecasts winds. Chronic exposure to operational oil spills was reported in terms of hazard indices for five vessel groups: pleasure and passenger ships, cargo and service vessels, the fishing fleet, tankers, and other ships. The northernmost Adriatic expectedly showed the highest hazard values, including the areas of Trieste and Venice, where cargo and service ships were the dominant polluters. The Croatian coastal waters were more chronically polluted than the Italian coastal waters; the predominant contribution was from coastwise pleasure and passenger ships.
•Operational oil spills from ships were modeled in the Adriatic.•EMODnet vessel densities were used to initiate virtual spills.•Stochastic MEDSLIK-II runs predicted the most/least affected areas.•Chronic oil pollution from coastwise shipping in Croatia should be studied.•Both model accuracy and quality of oil spill monitoring should be improved.
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In this work, we present a model of fission gas behavior in U3Si2 under light water reactor (LWR) conditions for application in engineering fuel performance codes. The model includes components for ...intra-granular and inter-granular behavior of fission gases. The intra-granular component is based on cluster dynamics and computes the evolution of intra-granular fission gas bubbles and swelling coupled to gas diffusion to grain boundaries. The inter-granular component describes the evolution of grain-boundary fission gas bubbles coupled to fission gas release. Given the lack of experimental data for U3Si2 under LWR conditions, the model is informed with parameters calculated via atomistic simulations. In particular, we derive fission gas diffusivities through density functional theory calculations, and the re-solution rate of fission gas atoms from intra-granular bubbles through binary collision approximation calculations. The developed model is applied to the simulation of an experiment for U3Si2 irradiated under LWR conditions available from the literature. Results point out a credible representation of fission gas swelling and release in U3Si2. Finally, we perform a sensitivity analysis for the various model parameters. Based on the sensitivity analysis, indications are derived that can help in addressing future research on the characterization of the physical parameters relative to fission gas behavior in U3Si2. The developed model is intended to provide a suitable infrastructure for the engineering scale calculation of fission gas behavior in U3Si2 that exploits a multiscale approach to fill the experimental data gap and can be progressively improved as new lower-length scale calculations and validation data become available.
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