1,721,029 research outputs found
Design of a Functionally Graded Composite for Service in High Temperature Lead and Lead-Bismuth Cooled Nuclear Reactors
No full textA material that resists lead-bismuth eutectic (LBE) attack and retains its strength at 700°C
would be an enabling technology for LBE-cooled reactors. No single alloy currently exists
that can economically meet the required performance criteria of high strength and corrosion
resistance. A Functionally Graded Composite (FGC) was created with layers engineered to
perform these functions. F91 was chosen as the structural layer of the composite for its
strength and radiation resistance. Fe-12Cr- 2Si, an alloy developed from previous work in
the Fe-Cr-Si system, was chosen as the corrosion-resistant cladding layer because of its
chemical similarity to F91 and its superior corrosion resistance in both oxidizing and
reducing environments.
Fe-12Cr-2Si experienced minimal corrosion due to its self-passivation in oxidizing and
reducing environments. Extrapolated corrosion rates are below one micron per year at
700°C. Corrosion of F91 was faster, but predictable and manageable. Diffusion studies
showed that 17 microns of the cladding layer will be diffusionally diluted during the three
year life of fuel cladding. 33 microns must be accounted for during the sixty year life of
coolant piping.
5 cm coolant piping and 6.35 mm fuel cladding were produced on a commercial scale by
weld-overlaying Fe-12Cr-2Si onto F91 billets and co-extruding them, followed by pilgering.
An ASME certified weld was performed followed by the prescribed quench-and-tempering
heat treatment for F91. A minimal heat affected zone was observed, demonstrating field
weldability. Finally, corrosion tests were performed on the fabricated FGC at 700°C after
completely breaching the cladding in a small area to induce galvanic corrosion at the
interface. None was observed.
This FGC has significant impacts on LBE reactor design. The increases in outlet
temperature and coolant velocity allow a large increase in power density, leading to either a
smaller core for the same power rating or more power output for the same size core. This
FGC represents an enabling technology for LBE cooled fast reactors
Conceptual Design of a Pick-and-Place 3D Nanoprinter for Materials Synthesis
No full textThe past decade has seen revolutionary advances in three-dimensional (3D) printing and additive manufacturing. However, a technique to create 3D material microstructures of arbitrary complexity has not yet been developed. We present the conceptual design of a 3D material microprinter as a concrete step toward an eventual 3D material nanoprinter. Such a device would enable the use of heterogeneous starting materials with printing resolution on the order of tens of nanometers. By combining a pick-and-place particle transfer method with a custom-built laser sintering optical microscope, the core components of the 3D printer are once again reimagined. This advance moves toward generalized material synthesis as an experimental technique to complement computational materials discovery of materials with unique structures and high interface density, such as 3D nanocomposites, metamaterials, and photonic structures.SUTD-MIT International Design Centre (IDC
Materials aging at the mesoscale: Kinetics of thermal, stress, radiation activations
No full textThe complexity of materials aging may be seen as a result of the interplay between several activation processes operating on multiple spatial and temporal scales. Though the disciplines involved may seem disparate at first, material aging fundamentally could be linked by the same set of underlying activations and responses of the system. We examine how recent studies of shear-induced deformation and rheological flow initiated in the soft-matter community can be leveraged to probe the mechanisms of radiation damage in nuclear materials. Bridging these two traditionally separate areas of research demonstrates the emerging notions of mesoscale science as a research frontier concerned with linking macroscale behavior to microscale processes in driven systems. We suggest the combining of microstructure-sensitive measurements with fundamental theories and mechanism-specific simulations is essential to addressing metastable materials responses of strongly activated states.United States. Department of Energy (Award DE-SC0002633
Physics-based multiscale coupling for full core nuclear reactor simulation
Full text linkNumerical simulation of nuclear reactors is a key technology in the quest for improvements in efficiency, safety, and reliability of both existing and future reactor designs. Historically, simulation of an entire reactor was accomplished by linking together multiple existing codes that each simulated a subset of the relevant multiphysics phenomena. Recent advances in the MOOSE (Multiphysics Object Oriented Simulation Environment) framework have enabled a new approach: multiple domain-specific applications, all built on the same software framework, are efficiently linked to create a cohesive application. This is accomplished with a flexible coupling capability that allows for a variety of different data exchanges to occur simultaneously on high performance parallel computational hardware. Examples based on the KAIST-3A benchmark core, as well as a simplified Westinghouse AP-1000 configuration, demonstrate the power of this new framework for tackling—in a coupled, multiscale manner—crucial reactor phenomena such as CRUD-induced power shift and fuel shuffle.Massachusetts Institute of Technology. Department of Nuclear Science and EngineeringIdaho National Laboratory (Contract DE-AC07-05ID14517
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
IM3D: A parallel Monte Carlo code for efficient simulations of primary radiation displacements and damage in 3D geometry
Full text linkSRIM-like codes have limitations in describing general 3D geometries, for modeling radiation displacements and damage in nanostructured materials. A universal, computationally efficient and massively parallel 3D Monte Carlo code, IM3D, has been developed with excellent parallel scaling performance. IM3D is based on fast indexing of scattering integrals and the SRIM stopping power database, and allows the user a choice of Constructive Solid Geometry (CSG) or Finite Element Triangle Mesh (FETM) method for constructing 3D shapes and microstructures. For 2D films and multilayers, IM3D perfectly reproduces SRIM results, and can be ∼10[superscript 2] times faster in serial execution and > 10[superscript 4] times faster using parallel computation. For 3D problems, it provides a fast approach for analyzing the spatial distributions of primary displacements and defect generation under ion irradiation. Herein we also provide a detailed discussion of our open-source collision cascade physics engine, revealing the true meaning and limitations of the “Quick Kinchin-Pease” and “Full Cascades” options. The issues of femtosecond to picosecond timescales in defining displacement versus damage, the limitation of the displacements per atom (DPA) unit in quantifying radiation damage (such as inadequacy in quantifying degree of chemical mixing), are discussed.National Natural Science Foundation (China) (Grant 11275229)National Natural Science Foundation (China) (Grant 11475215)National Natural Science Foundation (China) (Grant NSAF U1230202)National Natural Science Foundation (China) (Grant 11534012)National Basic Research Program of China (973 Program) (Grant 2012CB933702)Hefei Center for Physical Science and Technology (Grant 2012FXZY004)Chinese Academy of Sciences (Hefei Institutes of Physical Science (CASHIPS) Director Grant)National Science Foundation (U.S.) (DMR-1410636)National Science Foundation (U.S.) (DMR-1120901
Modeling injected interstitial effects on void swelling in self-ion irradiation experiments
No full textHeavy ion irradiations at high dose rates are often used to simulate slow and expensive neutron irradiation experiments. However, many differences in the resultant modes of damage arise due to unique aspects of heavy ion irradiation. One such difference was recently shown in pure iron to manifest itself as a double peak in void swelling, with both peaks located away from the region of highest displacement damage. In other cases involving a variety of ferritic alloys there is often only a single peak in swelling vs. depth that is located very near the ion-incident surface. We show that these behaviors arise due to a combination of two separate effects: 1) suppression of void swelling due to injected interstitials, and 2) preferential sinking of interstitials to the ion-incident surface, which are very sensitive to the irradiation temperature and displacement rate. Care should therefore be used in collection and interpretation of data from the depth range outside the Bragg peak of ion irradiation experiments, as it is shown to be more complex than previously envisioned
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
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