bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Properties of (Zr, TM)B2 Solid Solutions with TM = Ta, Mo, Re, V, and Cr
Authors: McClane Devon L. , Fahrenholtz William G. , Hilmas Gregory E.
Published: November 2014

The thermal properties were investigated for hot‐pressed zirconium diboride containing solid solution additions of tantalum, molybdenum, rhenium, vanadium, and chromium. The nominal additions were equivalent to 3 at.% of each metal with respect to zirconium. Using 0.5 wt% carbon as a sintering aid, powders were hot‐pressed to near full density at 2150°C. Rietveld refinement of X‐ray diffraction data was used to measure lattice parameters and to ensure that the additives formed solid solutions. Thermal conductivities were calculated from measured thermal diffusivities and temperature‐dependent values for density and heat capacity. Thermal conductivities at 25°C ranged from 88 W·(m·K)−1 for nominally pure ZrB2 down to 28 W·(m·K)−1 for (Zr,Cr)B2. Electron contributions to thermal conductivity were calculated from electrical resistivity measurements using the Wiedemann–Franz law. Decreases in phonon and electron conduction correlated with the size of the metallic additive, indicating that changes in atom size in the Zr lattice positions reduced thermal transport.
Seasonal variation in groundwater depth does not explain structure and diversity of tropical savannas
Authors: Silva L.C.R.
Published: November 2014

It has recently been proposed that seasonal fluctuations in groundwater depth drive spatial patterns of tree density and diversity in Neotropical savannas. Here I consider three major problems in the analysis that led to this conclusion, providing examples that demonstrate that groundwater levels do not constrain the establishment of woody communities and, therefore, cannot be used to explain patterns of tree density and diversity in savannas.
Development of the Trevo ProVue Retriever for intracranial clot removal in acute ischemic stroke
Authors: Prince Heather C. , Saliba Amelia J. , Wheeler Jaime , Bruder Scott
Published: November 2014

It is estimated that 15 million people worldwide have a stroke each year. Of the estimated 795,000 strokes that occur in the United States annually, the majority are ischemic strokes resulting from an obstruction within a vessel supplying blood to the brain. The treatment goal for these patients is to restore blood flow as quickly as possible. Increasingly, endovascular treatments that interact directly with the clot are being pursued as options. Receiving U.S. Food and Drug Administration clearance in 2012, the Trevo® Retriever is a stent‐like structure to be deployed at the site of an occlusion to allow the occluding thrombus to integrate into the device for subsequent removal and restoration of blood flow. The subsequent generation of the device, the ProVue Retriever, is fully radiopaque and designed to provide physicians with maximal information about the interaction of the device with the clot, providing enhanced feedback during the procedure. In this brief historical review, the development pathway, clinical experience, and future directions of the Trevo devices are summarized.
RNA‐guided transcriptional regulation in planta via synthetic dCas9‐based transcription factors
Authors: Piatek Agnieszka , Ali Zahir , Baazim Hatoon , Li Lixin , Abulfaraj Aala , Al‐Shareef Sahar , Aouida Mustapha , Mahfouz Magdy M.
Published: November 2014

Targeted genomic regulation is a powerful approach to accelerate trait discovery and development in agricultural biotechnology. Bacteria and archaea use clustered regularly interspaced short palindromic repeats (CRISPRs) and CRISPR‐associated (Cas) regulatory systems for adaptive molecular immunity against foreign nucleic acids introduced by invading phages and conjugative plasmids. The type II CRISPR/Cas system has been adapted for genome editing in many cell types and organisms. A recent study used the catalytically inactive Cas9 (dCas9) protein combined with guide‐RNAs (gRNAs) as a DNA‐targeting platform to modulate gene expression in bacterial, yeast, and human cells. Here, we modified this DNA‐targeting platform for targeted transcriptional regulation in planta by developing chimeric dCas9‐based transcriptional activators and repressors. To generate transcriptional activators, we fused the dCas9 C‐terminus with the activation domains of EDLL and TAL effectors. To generate a transcriptional repressor, we fused the dCas9 C‐terminus with the SRDX repression domain. Our data demonstrate that dCas9 fusion with the EDLL activation domain (dCas9:EDLL) and the TAL activation domain (dCas9:TAD), guided by gRNAs complementary to selected promoter elements, induce strong transcriptional activation on Bs3::uidA targets in plant cells. Further, the dCas9:SRDX‐mediated transcriptional repression of an endogenous gene. Thus, our results suggest that the synthetic transcriptional repressor (dCas9:SRDX) and activators (dCas9:EDLL and dCas9:TAD) can be used as endogenous transcription factors to repress or activate transcription of an endogenous genomic target. Our data indicate that the CRISPR/dCas9 DNA‐targeting platform can be used in plants as a functional genomics tool and for biotechnological applications.
Transgenic soya bean seeds accumulating β‐carotene exhibit the collateral enhancements of oleate and protein content traits
Authors: Schmidt Monica A. , Parrott Wayne A. , Hildebrand David F. , Berg R. Howard , Cooksey Amanda , Pendarvis Ken , He Yonghua , McCarthy Fiona , Herman Eliot M.
Published: November 2014

Transgenic soya bean (Glycine max) plants overexpressing a seed‐specific bacterial phytoene synthase gene from Pantoea ananatis modified to target to plastids accumulated 845 μg β carotene g−1 dry seed weight with a desirable 12:1 ratio of β to α. The β carotene accumulating seeds exhibited a shift in oil composition increasing oleic acid with a concomitant decrease in linoleic acid and an increase in seed protein content by at least 4% (w/w). Elevated β‐carotene accumulating soya bean cotyledons contain 40% the amount of abscisic acid compared to nontransgenic cotyledons. Proteomic and nontargeted metabolomic analysis of the mid‐maturation β‐carotene cotyledons compared to the nontransgenic did not reveal any significant differences that would account for the altered phenotypes of both elevated oleate and protein content. Transcriptomic analysis, confirmed by RT‐PCR, revealed a number of significant differences in ABA‐responsive transcripton factor gene expression in the crtB transgenics compared to nontransgenic cotyledons of the same maturation stage. The altered seed composition traits seem to be attributed to altered ABA hormone levels varying transcription factor expression. The elevated β‐carotene, oleic acid and protein traits in the β‐carotene soya beans confer a substantial additive nutritional quality to soya beans.
Identification and overexpression of gibberellin 2‐oxidase (GA2ox) in switchgrass (Panicum virgatum L.) for improved plant architecture and reduced biomass recalcitrance
Authors: Wuddineh Wegi A. , Mazarei Mitra , Zhang Jiyi , Poovaiah Charleson R. , Mann David G. J. , Ziebell Angela , Sykes Robert W. , Davis Mark F. , Udvardi Michael K. , Stewart Charles Neal
Published: November 2014

Gibberellin 2‐oxidases (GA2oxs) are a group of 2‐oxoglutarate‐dependent dioxygenases that catalyse the deactivation of bioactive GA or its precursors through 2β‐hydroxylation reaction. In this study, putatively novel switchgrass C20 GA2ox genes were identified with the aim of genetically engineering switchgrass for improved architecture and reduced biomass recalcitrance for biofuel. Three C20 GA2ox genes showed differential regulation patterns among tissues including roots, seedlings and reproductive parts. Using a transgenic approach, we showed that overexpression of two C20 GA2ox genes, that is PvGA2ox5 and PvGA2ox9, resulted in characteristic GA‐deficient phenotypes with dark‐green leaves and modified plant architecture. The changes in plant morphology appeared to be associated with GA2ox transcript abundance. Exogenous application of GA rescued the GA‐deficient phenotypes in transgenic lines. Transgenic semi‐dwarf lines displayed increased tillering and reduced lignin content, and the syringyl/guaiacyl lignin monomer ratio accompanied by the reduced expression of lignin biosynthetic genes compared to nontransgenic plants. A moderate increase in the level of glucose release in these transgenic lines might be attributed to reduced biomass recalcitrance as a result of reduced lignin content and lignin composition. Our results suggest that overexpression of GA2ox genes in switchgrass is a feasible strategy to improve plant architecture and reduce biomass recalcitrance for biofuel.
The Perception of Activity
Authors: Crowther Thomas
Published: November 2014

There is a much‐discussed form of argument the conclusion of which is that we do not directly perceive space‐filling material objects themselves, only parts of their surfaces. Donald Davidson's view that events are temporal particulars invites a structurally similar argument about the direct perception of events. In this paper, I spell out such an argument and consider a number of possible solutions to it. I explore the idea that a satisfactory response to this problem in the philosophy of perception can be grounded in a temporal ontology that includes temporal stuff as well as temporal particulars. I discuss different ways of developing this idea, and I go on to identify what I take to be the most promising version of an approach of this kind.
Perceptual Guidance
Authors: Watzl Sebastian
Published: November 2014

Proponents of an intentionalist theory of perceptual experience have taken for granted that perceptual experience is an informing form of intentionality. Hence they often speak of the way an experience represents the environment to be, or what there is. In this respect perceptual experience is thus assumed to resemble a speech act like assertion or a mental state like belief. There is another important form of intentionality though that concerns not what there is, but what to do. I call this a guiding form of intentionality. In speech, there are – for example – imperatives and among intentional mental states there are desires and intentions. In this paper I argue that perceptual experience is at least sometimes characterized by such a guiding form of intentionality. Perception does not just inform, it is sometimes intrinsically action‐guiding. I call this the perceptual guidance claim. I distinguish the perceptual guidance claim from related, but importantly distinct claims (such as claims concerning the perception of affordances or concerning whether perception is normative), and argue that perceptual action guidance occurs not just in an unconscious vision‐for‐action system, but also within conscious perceptual experience.
Distinct relict fringing reefs in the northern shelf of the Gulf of Elat/Aqaba: Markers of Quaternary eustatic and climatic episodes
Authors: Hartman Gal , Niemi Tina M. , Ben‐Avraham Zvi , Tibor Gideon , Al‐Zoubi Abdallah , Sade Ronnie A. , Hall John K. , Akawi Emad , Abueladas Abd , Al‐Ruzouq Rami , Makovsky Yizhaq
Published: November 2014

Quaternary reef development and demise have been shown to correspond to worldwide sea‐level fluctuations and related environmental changes, yet the mechanisms and rates affecting this relationship are not well resolved. A set of high‐resolution seismic reflection and multibeam bathymetric data were interpreted. Six distinct systems of relict fringing reefs embedded within the sedimentary cover of the northern shelf of the Gulf of Elat/Aqaba were identified. The two uppermost relict fringing reefs are also exposed on the sea floor in water depths of ca 20 m and ca 60 m, along the north‐western corner of the northern Gulf of Elat/Aqaba and sub‐parallel to the current northern coast, respectively. Two other relict fringing reefs are laterally correlated to each of the last two transgressive cycles, and are inferred to have formed during decelerations in sea‐level rise during the last two deglaciations. These reefs and the units to which they are laterally correlated portray a repeating stratigraphic pattern of reef development during deposition of seismically homogeneous sediment and an ensuing demise during deposition of heterogeneous sediment. Correlation of the reef stratigraphy with rates of Late Quaternary sea‐level rise and a sediment accumulation rate from one shelf core provide age estimations for the seismic stratigraphy. Two phases of fringing reef generation occurred during the last deglaciation (since ca 18 ka); the older reef probably developed between 12·8 ka and 11·5 ka at ca 60 m below present sea‐level and the younger reef after 8·4 to 8·0 ka at ca 20 m below present sea‐level. These last two phases of reef generation are separated by a lobate seismic unit that is interpreted as fluvial‐deltaic deposits that backstepped across the shelf during the Early Holocene transgression. Results suggest that fringing reefs evolved along the northern shelf of the Gulf of Elat/Aqaba only during relative decelerations in sea‐level rise, contemporaneous with low input of terrigenous sediment and probably during a period of aridity. At present, no fringing reef grows along the northern coast of the Gulf of Elat/Aqaba, suggesting that these relatively arid periods may have been drier than Recent. The pattern of slowdown in sea‐level rise contemporaneous with conditions of increased aridity seems to have repeated during the last two sea‐level rises, approximately at the same sea‐levels, suggesting a common mechanism of short (millennium‐scale) phases of eustatic and climatic alteration during deglaciations.
The receptor kinase CERK1 has dual functions in symbiosis and immunity signalling
Authors: Zhang Xiaowei , Dong Wentao , Sun Jongho , Feng Feng , Deng Yiwen , He Zuhua , Oldroyd Giles E.D. , Wang Ertao
Published: November 2014

The establishment of symbiotic interactions between mycorrhizal fungi, rhizobial bacteria and their legume hosts involves a common symbiosis signalling pathway. This signalling pathway is activated by Nod factors produced by rhizobia and these are recognised by the Nod factor receptors NFR1/LYK3 and NFR5/NFP. Mycorrhizal fungi produce lipochitooligosaccharides (LCOs) similar to Nod factors, as well as short‐chain chitin oligomers (CO4/5), implying commonalities in signalling during mycorrhizal and rhizobial associations. Here we show that NFR1/LYK3, but not NFR5/NFP, is required for the establishment of the mycorrhizal interaction in legumes. NFR1/LYK3 is necessary for the recognition of mycorrhizal fungi and the activation of the symbiosis signalling pathway leading to induction of calcium oscillations and gene expression. Chitin oligosaccharides also act as microbe associated molecular patterns that promote plant immunity via similar LysM receptor‐like kinases. CERK1 in rice has the highest homology to NFR1 and we show that this gene is also necessary for the establishment of the mycorrhizal interaction as well as for resistance to the rice blast fungus. Our results demonstrate that NFR1/LYK3/OsCERK1 represents a common receptor for chitooligosaccharide‐based signals produced by mycorrhizal fungi, rhizobial bacteria (in legumes) and fungal pathogens. It would appear that mycorrhizal recognition has been conserved in multiple receptors across plant species, but additional diversification in certain plant species has defined other signals that this class of receptors can perceive.
In Arabidopsis thaliana two co‐adapted cyto‐nuclear systems correlate with distinct ccmC transcript sizes
Authors: Stoll Katrin , Jonietz Christian , Binder Stefan
Published: November 2014

Plant mitochondrial transcripts undergo maturation processes at both termini. Although frequently observed, the post‐transcriptional formation of mature 5′ ends is still poorly understood. We now analyzed the processing of transcripts derived from the mitochondrial ccmC gene, coding for a component of the cytochrome c maturation system. In Arabidopsis thaliana (Arabidopsis) there are two mitochondrial ccmC configurations, discriminated by a 66‐bp sequence segment located approximately 500 bp upstream of the ccmC gene. In Arabidopsis accessions these divergent mitochondrial genotypes correlate with the generation of two different 5′ termini that map to positions around −484 in accession Columbia (Col ccmC genotype) or −390 in accession C24 relative to the translation start codon (C24 ccmC genotype). Previously we identified RNA PROCESSING FACTOR 3 (RPF3), a pentatricopeptide repeat (PPR) protein required for the maturation of ccmCmRNAs with −484 5′ ends transcribed from the Col ccmC genotype. Now we identified several accessions defective in maturation of ccmC transcripts. Taking advantage of this natural genetic variation we identified RNA PROCESSING FACTOR 6 (RPF6), a PPR protein necessary for the generation of ccmCmRNAs with −390 5′ ends transcribed from the C24 ccmC genotype. Both Col‐type and C24‐type accessions encode RPF3 and RPF6 so that they can process ccmC transcripts derived from the two different mitochondrial genotypes. These factors and their cognate RNA recognition sites in the different ccmC genotypes are an intriguing example for the evolution of two co‐adapted cyto‐nuclear systems required for the same process i.e. 5′ maturation of ccmC transcripts.
Effect of uraemia on endothelial cell damage is mediated by the integrin linked kinase pathway
Authors: García‐Jérez Andrea , Luengo Alicia , Carracedo Julia , Ramírez‐Chamond Rafael , Rodriguez‐Puyol Diego , Rodriguez‐Puyol Manuel , Calleros Laura
Published: November 2014

Key points

Patients with chronic kidney disease have a higher risk of developing cardiovascular diseases than the general population. Their vascular endothelium is dysfunctional, among other things, because it is permanently exposed to uraemic toxins, several of which have poor clearance by conventional dialysis.

Recent studies have demonstrated the important role of integrin‐linked kinase (ILK) in the maintenance of endothelial integrity and in this study we investigate the involvement of ILK in the mechanism underlying vascular endothelial damage that occurs in uraemia.

For the first time, we demonstrate the implication of ILK in the protection against endothelial cell damage (inhibition of proliferation, toxicity, oxidative stress and programed cell death) induced by uraemic serum from chronic kidney disease patients and uraemic toxins.

This molecular mechanism may have clinical relevance because it highlights the importance of maintaining high levels of ILK activity to help preserve endothelial integrity, at least in early stages of chronic kidney disease.

Patients with chronic kidney disease (CKD) have a higher risk of developing cardiovascular diseases. Their vascular endothelium is dysfunctional, among other things, because it is permanently exposed to uraemic toxins, several of which, mostly protein‐bound compounds such as indoxyl sulfate (IS) and p‐cresyl sulphate, having poor clearance by conventional dialysis, induce endothelial toxicity. However, the molecular mechanism by which uraemic toxins regulate early stages of endothelial dysfunction remains unclear. Recent studies have demonstrated the important role of integrin‐linked kinase (ILK) in the maintenance of endothelial integrity. In this study, we investigate the involvement of ILK in the mechanism underlying vascular endothelial damage that occurs in uraemia. First, we show that incubation of EA.hy926 cells with human uraemic serum from CKD patients upregulates ILK activity. This ILK activation also occurs when the cells are exposed to IS (25–100 μg ml−1), p‐cresol (10–100 μg ml−1) or both combined, compared to human serum control. Next, we observed that high doses of both toxins together induce a slight decrease in cell proliferation and increase apoptosis and reactive oxygen species production. Interestingly, these toxic effects displayed a strong increase when the ILK protein is knocked down by small interfering RNA, even at low doses of uraemic toxins. Abrogation of AKT has demonstrated the ILK/AKT signalling pathway involved in these processes. This study has demonstrated the implication of ILK in the protection against endothelial cell damage induced by uraemic toxins, a molecular mechanism that could play a protective role in the early stages of endothelial dysfunction observed in uraemic patients.
Experimental Study on Lithium Leakage Behavior
Authors: Furukawa Tomohiro , Ohtaka Masahiko , Hirakawa Yasushi
Published: November 2014

In the Japanese engineering validation activities on the target facility of the International Fusion Materials Irradiation Facility, two studies on the advanced lithium leak detection system and the fire-extinguishing behavior of lithium were performed.

In the former study, the fluorescence was distinguishable from the background using the difference of decay curves from the results of the lithium fluorescence measurement under two lithium concentration (256 ng/L and 4.58 ng/L) in argon. This result shows the basic applicability of the laser based lithium measuring technique as the lithium detector could be confirmed.

In the latter study, fire-extinguishing behavior of two kinds of carbon base fire extionguishishants — MITEX and GRAPHEX — to lithium was examined. The both extinguishants showed excellent fire-extinguishing performance, and there were equivalent to that of Natlex-L obtained in the previous study. Since the bulk densities of the both carbon based extinguishants were about equal to the density of lithium, the subsidence of the fire-extinguishings which was observed in the Natlex-L was not observed. In fact, it was considered that no dependency of lithium pool depth on the required thickness of the fire extinguishants was observed for the carbon based extinguishants.
Development of Numerical Simulation for Jet Breakup Behavior in Complicated Structure of BWR Lower Plenum: (3) Influence by Complicated Structure on Jet Breakup and Fragmentation Behavior
Authors: Saito Ryusuke , Abe Yutaka , Kaneko Akiko , Suzuki Takayuki , Yoshida Hiroyuki , Nagase Fumihisa
Published: November 2014

To estimate the state of Reactor Pressure Vessel (RPV) of Fukushima Daiichi nuclear power plant, it is important to clarify the breakup and the fragmentation behavior of molten material jet in BWR lower plenum by a numerical simulation. To clarify the effects of complicated structures on jet breakup and fragmentation behavior experimentally and construct the benchmarks of the simulation code, we conduct the visualized experiments simulating the severe accident in the BWR. In this study, the jet breakup behavior, the fragmentation behavior and internal/external velocity profiles of the jet were observed by the backlight method and the particle image velocimetry (PIV). From experimental results, it is clarified that the complicated structures prolong the jet breakup length or make the fragments fallen together to the lower plenum similar to the bulk state. In addition, it is clarified that strong shearing stress occurs at the crest of interfacial waves at side of the jet when fragments are generated. Finally, the fragment diameters measured in the present study well agree with the theory suggested by Kataoka et al. (1983) by changing the coefficient term at each experimental condition. Thus, it is suggested that the fragmentation mechanism is mainly controlled by shearing stress and the fragment diameter can be estimated by adjusting the constant term.
The Study of the Multi-Sensors’ Reliability on the AMB System of HTR-10GT
Authors: Zhou Yan , Mo Ni , Shi ZhenGang , Yang GuoJun
Published: November 2014

This article uses the Markov process to analyze the displacement redundant unit on the active magnetic bearings (AMB) system in HTR-10GT, especially on the aspects of the reliability, redundancy and maintenance issues. The reliability mathematical model is established, and the state transition diagram and the state transition matrix are deduced under the different conditions, furthermore the expression on reliability of the displacement redundant sensors is given. According to the different failure rate of single degree speed sensor, the curve about the measurement unit reliability versus time is calculated. The method mentioned above provides a new and practical approach to improve the reliability of the system and to optimize the displacement measurement redundant unit, which also can to be as a guiding role for the fault diagnosis of system.
On the Wall Drag and the Form Loss for Dispersed Flow
Authors: Kim Byoung Jae , Lee Seong Wook , Kim Jungwoo , Kim Kyung Doo
Published: November 2014

This paper demonstrates the validity of newly-developed the wall drag and form loss partitioning methods for dispersed flow. The wall drag partitioning method is proposed based on the equation of a solid/fluid particle motion. The bubble is faster than the water in a contraction while the former is slower than the latter in an expansion. The droplet is slower than the gas in a contraction while the former is faster than the latter in an expansion. In addition, this study shows that the existing form loss model predicts incorrectly the dispersed phase velocity. A new form loss computation method is proposed.
Application of Some Turbulence Models to Simulate Buoyancy-Driven Flow
Authors: Abdalla Aniseh A. A. , Yu Jiyang , Alrwashdeh Mohammad
Published: November 2014

During a severe nuclear power plant (NPP) accident, large amounts of hydrogen and steam can be produced in nuclear reactor containment. In the case of hydrogen combustion, there is a possibility of producing short term pressure or detonation force. Therefore, these gas species’ production could threaten containment integrity. For instance, in the past, two gas explosion accidents occurred: In 1979 Three Mile Island and in 2011 Fukushima. After these accidents, modeling the gas behavior became an important topic in nuclear safety analyses. In order to predict hydrogen behavior and other gas species transport, mixing and combustion, reliable turbulence models need to be applied. In this work, standard k–ε, k–ω, RNG k–ε, Realizable k–ε and SST k–ω turbulence models are addressed. The computations are performed with HYDRAGON code. HYDRAGON code is a three-dimensional thermal-hydraulic code, developed to solve low-speed gas flow of compressible Navier-Stokes equations in cartesian or cylindrical coordinates or a mixture of the two coordinates. The goal of this work is to test the performance of these models by comparing the results to the benchmark. The code aims to predict containment thermal-hydraulic conditions during NPP accident.
An Experimental Study on Insulating Property of Helium in High Temperature Gas Cooled Reactor
Authors: Yue Shan , Liu Xingnan , Shi Zhengang
Published: November 2014

HTGR, short for high temperature gas cooled reactor, has gained a lot of attention in nuclear industry. Gas helium, 7MPa in pressure, is used as primary coolant of HTR-PM in where there are a lot of electrical equipment. Insulating property of helium is worse than that of air according to Paschen curves and there are very few articles or related standards about insulating property of high pressure gas helium, which makes the electrical equipment structure design lack of basis. In this study, an experimental platform for testing insulating performance is designed, based on which the experiments of testing the withstanding voltages of penetration assemblies and the breakdown voltages of parallel plane electrodes at different pressures are carried out. The results show that for both the penetration assemblies and the parallel plane, their breakdown voltages in helium are far lower than in air under the same condition of 15°C /0.1MPa. For the penetration assemblies, their insulating properties in helium at 150°C/7MPa are better than those in air at 15°C/0.1MPa.
A Design of Magnetic Load Simulator for the Rotor Dropping Protection Experiment System of Helium Circulator in HTR
Authors: Liang Zhu , Hong Wang
Published: November 2014

The rotor of helium circulator in High Temperature Reactor (HTR) is supported by magnetic bearings, but the auxiliary bearings of the magnetic bearings are easy to be broken if the rotor touched down the bearings at the full speed. If the rotor touched down more than a few times, the auxiliary bearings must be changed, which will bring huge economic losses to the HTR. Therefore, we designed a rotor dropping protection system which can reduce the impact when the touching down happened and protect the auxiliary bearings from more damages. We designed an experiment system to validate the reliability of the protection system. For simulating the impact of the auxiliary bearings when the rotor dropped, a magnetic load simulator was designed, which can exert axial load to the motor directly by electromagnetic force though a similar technology to the magnetic bearings. The design axial load of the magnetic load simulator is 110kN with a clearance of 1mm. By analyzing and calculating the parameter of the magnetic load simulator, we thought it can meet the loading requirements of this test. And the design of the magnetic load simulator will open up a new way of application for the magnetic bearings.
A Study on High Heat Flux Heat Removal With Boiling Using Porous Microchannel
Authors: Hanzawa Daiki , Katsumata Kyosuke , Okawa Tomio
Published: November 2014

This paper reports the critical heat flux (CHF) enhancement that was observed experimentally when a porous metal was placed in a small flow channel (hereafter, this channel is called a “porous microchannel”). In the porous microchannel, the CHF value increased almost linearly with increased values of the mass flux and the inlet subcooling. In consequence, higher cooling performance was achieved under high mass flux and high inlet subcooling conditions. It was also found that considerable fluctuation of the pressure loss frequently encountered in a small heated channel disappears in the porous microchannel. It was considered that the stabilization of the pressure loss can mainly be attributed to inhibition of the formation of large bubbles. The effects of the material and the pore size of the porous metal were also investigated. Silver and nickel were selected as the porous metal material and the pore size tested was 0.2 and 0.6 mm. In the present experiments, the CHF value was not influenced significantly by the material in spite of the distinct difference of the thermal conductivity between silver and nickel, whilst it was dependent noticeably on the pore size. It was hence suggested that the CHF enhancement observed in this work was mainly caused by the complex thermal-hydraulic field formed in the porous microchannel. Preliminary results of the flow visualization performed to reveal the mechanisms of the CHF enhancement in the porous microchannel was also reported.
Development of Prediction Technology of Two-Phase Flow Dynamics Under Earthquake Acceleration: (14) Numerical Simulation of Two-Phase Flow in Subchannels Under Accelerating Condition
Authors: Yoshida Hiroyuki , Nagatake Taku , Takase Kazuyuki , Kaneko Akiko , Monji Hideaki , Abe Yutaka
Published: November 2014

An earthquake is one of the most serious phenomena to consider for the safety of a nuclear reactor in Japan. Therefore, structural safety of nuclear reactors has been studied and nuclear reactors were contracting with structural safety for a big earthquake. However, it is not enough for safety operation of nuclear reactors because thermal-fluid safety is not confirmed under the earthquake. For instance, behavior of gas-liquid two-phase flow is unknown in seismic conditions. Especially, fluctuation of void fraction is an important factor for the safety operation of the nuclear reactor. In previous work, fluctuation of void faction in bubbly flow was studied experimentally and theoretically to investigate the stability of the bubbly flow. In such studies, flow rate or void fraction fluctuations were given to the steady bubbly flow. In case of the earthquake, the fluctuation is not only the flow rate, but also a body force on the two-phase flow and shear force through the pipe wall. Interactions of gas and liquid through their interface also act on the behavior of the two-phase flow. The fluctuation of the void fraction is not clear for such complicated situation during the earthquake.

Therefore, the behavior of gas-liquid two-phase flow is investigated experimentally and numerically in a series of studies. In this study, to develop the predictive technology of two-phase flow dynamics under earthquake acceleration, a detailed two-phase flow simulation code with an advanced interface tracking method TPFIT (Two-Phase Flow simulation code with Interface Tracking) was expanded to two-phase flow simulation in seismic conditions. In a previous study, we performed a numerical simulation of a two-phase bubbly flow in a horizontal pipe and a vertical bubble motion in a water tank in seismic conditions. And it was confirmed that the modified TPFIT can be applicable to the bubbly flow in seismic conditions.

In this paper, the two-phase bubbly flow in a simulated single-subchannel excited by oscillation acceleration was simulated by using the expanded TPFIT. A calculation domain used in this simulation was a simplified subchannel in a BWR core. And time-series of void fraction distributions were evaluated based on predicted bubble distributions. When no oscillation acceleration was added, void fraction concentrated in a region near the wall. When oscillation acceleration was added, void fraction distribution was changed by time. And coalesces of bubbles occurred in the numerical simulation, and bubbles with relatively large diameter were observed. In the results, complicated void fraction distribution was observed, because the response of void fraction distribution on the oscillation acceleration was dependent on not only imposed acceleration, but also the bubble diameter.
Development of Numerical Simulation for Jet Breakup Behavior in Complicated Structure of BWR Lower Plenum: (4) Multi-Channel Experimental Analysis by Detailed Two-Phase Analysis Code TPFIT
Authors: Suzuki Takayuki , Yoshida Hiroyuki , Nagase Fumihisa , Abe Yutaka , Kaneko Akiko
Published: November 2014

In order to improve the safety of Boiling Water Reactor (BWR), it is required to know the behavior of the plant when an accident occurred as can be seen at Fukushima Daiichi nuclear power plant accident. Especially, it is important to estimate the behavior of molten core jet in the lower part of the reactor pressure vessel at a severe accident. In the BWR lower plenum, the flow characteristics of molten core jet are affected by many complicated structures, such as control rod guide tubes, instrument guide tubes and core support plate. However, it is difficult to evaluate these effects on molten core jet experimentally. Therefore, we considered that multi-phase computational fluid dynamics approach is the best way to estimate the effects on molten core jet by complicated structure. The objective of this study is to develop the evaluation method for the flow characteristic of molten core jet including the effects of the complicated structures in the lower plenum. So we are developing a simulation method to estimate the behavior of molten core jet falling down through the core support plate to the lower plenum of the BWR. The simulation method is based on interface tracking method code TPFIT (Two Phase Flow simulation code with Interface Tracking). To verify and validate the applicability of the developed method in detail, it is necessary to obtain the experimental data that can be compared with detailed numerical results by the TPFIT. Thus, the authors are carrying out experimental works by use of multi-phase flow visualization technique. In the experiments, time series of interface shapes are observed by high speed camera and velocity profiles in/out of the jet are measured by the PIV method. In this paper, we carried out analysis of the multi-channel experiment using the analytical method based on the TPFIT. Specifically, predicted results including interface shape and velocity profile in and out simulated molten material were compared with measured results. In the results, predicted results agreed with measured results qualitatively.
Development of Hydrogen Loading System and Characterization of Tritiated Metallic Films for Betavoltaic Batteries
Authors: Adams Thomas E. , Revankar Shripad T.
Published: November 2014

Betavoltaic cells can provide extended power up to 10 or more years in extreme temperature environments, −55°C to 150°C. However there is limited study on the loading of tritium which is beta source for these cells. The present study examines the loading of the tritium using surrogate hydrogen gas in various films through experiments and simulations. A detailed review of the betavoltaic cell characteristics is first discussed and key challenges in this technology are identified. For the experimental work, a testing facility is designed for loading hydrogen in metallic films such as titanium, palladium and scandium which are good for storage of hydrogen or tritium. The facility is unique as it enables precise measurement of hydrogen loading in the films using pressure difference. Preliminary tests of loading on scandium films were carried out and some results are presented. In order to optimize the film thickness simulations were carried out using MC-SET code for beta flux emission. The results of the simulations for titanium and palladium film are presented.
Water/Pb-Bi Interaction Experiments in LIFUS5/Mod2 Facility Modelled by SIMMER Code
Authors: Pesetti Alessio , Forgione Nicola , Del Nevo Alessandro
Published: November 2014

The new generation Heavy Liquid Metal Reactors (HLMRs) are characterized by a pool type configuration having high pressure steam generators set inside the reactor vessel. The primary (hot low pressure LBE melt) and secondary (high pressure sub-cooled water) coolant could come into contact as consequence of Steam Generator Tube Rupture (SGTR) phenomenon, that cannot be considered negligible. The structural integrity of the reactor internals, steam generators in particular, could be affected by the SGTR scenario consequences. The pressure wave propagation, cover gas pressurization, domino effect on the surrounding tubes, reactivity feedback due to steam dragged into the core, primary system pollution and slug formation constitute the most hazardous effects of the SGTR accident. Therefore, this accidental scenario constitutes a safety issue in the design and in the preliminary safety analysis. A key issue in the SGTR analysis for HLMRs is constituted by the availability of qualified experimental data, suitable to be extrapolated to full scale plant and to support the computer code development and demonstrating the code reliability in the phenomena prediction (qualified code).

In this paper, part of the experimental campaign performed in the LIFUS5/Mod2 facility at ENEA CR Brasimone (in the frame of the THINS project), investigating the water-LBE interaction, is reported. The experimental activity aimed to provide high-quality measurement data for supporting the development and validation phase of computer codes for SGTR numerical simulation. The reported experimental test has been numerically simulated by SIMMER III code. The pressure, temperature and injected water mass flow rate time trends have been computed during the water-LBE interaction in the reaction vessel. The work aims to evaluate the prediction capability of the two-dimensional SIMMER III code and to determine the suitability of the SIMMER code physical models.
Application of Film Dryout Model in Liquid Metal CHF Prediction
Authors: Ma Zaiyong , Nina Yue , Qiu Suizheng , Tian Wenxi , Su Guanghui
Published: November 2014

Liquid metals have been used as coolants of several kinds of nuclear reactors, and the prediction of critical heat flux (CHF) is rather important for the design, safety and economy of these reactors. A film dryout model considering the deposition and entrainment of droplets was established to obtain the CHF of liquid metal in annular flow flowing in tubes. The correlations of deposition rate, entrainment rate and so on for conventional fluids were used, and the initial entrainment fraction was determined according to experimental data. Results showed that the correlations for conventional fluids could be used for liquid metals approximately, but relatively large error might occur for large heat flux. The accuracy of this model for sodium and potassium was similar for small heat flux, but had some differences for large heat flux. Special correlations of deposition rate, entrainment rate and so on should be developed to predict the CHF of liquid metals more accurately.
Framework for Assessing Transition Scenarios to Sustainable Nuclear Energy Systems
Authors: Fesenko Galina , Kuznetsov Vladimir , Usanov Vladimir
Published: November 2014

The International Atomic Energy Agency’s (IAEA’s) International Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO) was established in 2000 with the goal to ensure a sustainable nuclear energy supply to meet the global energy needs in the 21st century. The INPRO activities on global and regional nuclear energy scenarios provide newcomers and mature nuclear countries alike with better understanding of options for making a collaborative transition to future sustainable nuclear energy systems. Collaborative project GAINS (Global Architecture of Innovative Nuclear Energy Systems Based on Thermal and Fast Reactors Including a Closed Fuel Cycle) developed an internationally verified analytical framework for assessing such transition scenarios. The framework (hereafter, GAINS framework) is a part of the integrated services provided by IAEA to Member States considering initial development or expansion of their nuclear energy programmes. The paper presents major elements of the analytical framework and selected results of its application, including:

• Long-term nuclear energy demand scenarios based on the IAEA Member States’ high and low estimations of nuclear power deployment until 2030 and expected trends until 2050 and on forecasts of competent international energy organizations;

• Heterogeneous world model comprised of groups of non-personified non-geographical countries (NGs) with different policy regarding nuclear fuel cycle back end;

• Architectures of nuclear energy systems;

• Metrics and tools for the assessment of dynamic nuclear energy system evolution scenarios regarding sustainability, including a set of key indicators and evaluation parameters;

• An internationally verified database with best estimate material flow and economic characteristics of existing and advanced nuclear reactors and associated nuclear fuel cycles needed for material flow analysis and comparative economic analysis, extending the previously developed IAEA databases and taking into account preferences of different countries;

• Selected results of sample analysis for scenarios involving transition from the present fleets of nuclear reactors and fuel cycles to future sustainable nuclear energy system architectures involving innovative technological solutions.
Improvement of the System for Passive Heat Removal Through Steam Generators (SG PHRS) on NPP With VVER-1200 in the Light of “Fukushima” Accident
Authors: Bezlepkin Vladimir , Semashko Sergey , Alekseev Sergey , Ivanova Marina , Vardanidze Teimuraz , Petrov Yuriy
Published: November 2014

As a result of catastrophic events on the nuclear power plant “Fukushima” the European organizations on regulation of nuclear power (ENSREG) initiated wide-scale measures for complex designs revision of already operating and under construction European and Russian NPPs. Inspection was made about resistance of power units to external influences of the natural character, being accompanied by multiple failures of safety systems.

Within these works stress tests for constructed power units of LAES-2 and the Baltic NPP were executed. The structure of these checks included the settlement analysis of a condition of NPP at accident with loss of all AC power supply sources which results are presented in report materials.

Accident calculations with a full blackout were executed on the best-estimated heat-hydraulics code KORSAR/GP for justification of power unit preservations in the intact condition within 72 hours from the accident beginning by means of SG PHRS.

The system is developed for feed of the SG PHRS tanks and the fuel pool for working capacity extension the SG PHRS and power unit preservation in a stable condition more than 72 hours from the accident beginning.

Use of system for feed of tanks the SG PHRS and the fuel pool allows to increase significantly resistance of the NPP to external influences of the natural character and to increase time of preservation of the blackout power unit in a stable condition more than 5 days.
Research on Flow Characteristics of Once-Through Steam Generator in Rolling Motion
Authors: Li Ren , Peng Min-jun , Xia Geng-lei , Sun Yuan-li , Zhao Ya-nan
Published: November 2014

Owing to its compact structure, the once-through steam generator (OTSG) is used widely in integrated Pressurized Water Reactor (PWR) The casing OTSG in concentric annuli tube is a new type of steam generator which applies double sides to transfer heat. The water of the secondary side goes through complicated phase change processes, and the flow pattern and heat transfer cases are much more complex than those of the natural circulation steam generator used in PWR. It is necessary to study their steady-state and dynamic characteristics. By means of THEATRe code which was based on the two-phase drift flux model and was modified by adding module calculating the effect of rolling motion, the casing OTSG simulation model in rolling motion was built. It can describe the parameters change in every section of OTSG accurately in rolling motion, and can embody dynamics characteristics from different aspects. By comparing the operational data in different rolling amplitude and rolling period, flow operational characteristics and principles were analyzed. The results can be used to analyze the thermal-hydraulics characteristics of the integrated PWR in rolling motion.
Numerical Simulation of Thermal Behavior of a Molten Droplet Covered With Vapor Film
Authors: Zhong Mingjun , Lin Meng , Xiong Jinbiao , Li Yankai , Yang Yanhua
Published: November 2014

When the molten fuel with high temperature falls into the cavity water, it will be dispersed to droplets which are covered with vapor films due to the rapid heat transfer with phase transition. This situation cannot be simply described by liquid-liquid nor gas-liquid systems. And there are not sufficient experimental studies on the behavior of droplet covered with vapor film because of the rapid reaction and the difficulty in capture of the film configuration. In this paper, A multi-phase code with the Volume of Fluid Method (VOF) is developed to simulate the behavior of droplet covered with vapor film. Thermal effect is considered. The simulation results indicate that the film thickness and material density have significant effect on the behavior of droplet. The situation assumed in Ciccarelli and Frost’s model is observed in current simulation of thermal droplet behavior.