bluuebunny/crossref_metadata_2025 huggingface dataset:
Photodynamic and Nail Penetration Enhancing Effects of Novel Multifunctional Photosensitizers Designed for The Treatment of Onychomycosis
Authors: Smijs Threes , Dame Zoë , de Haas Ellen , Aans Jan‐Bonne , Pavel Stan , Sterenborg Henricus
Published: October 2013

Novel multifunctional photosensitizers (MFPSs), 5,10,15‐tris(4‐N‐methylpyridinium)‐20‐(4‐phenylthio)‐[21H,23H]‐porphine trichloride (PORTH) and 5,10,15‐tris(4‐N‐methylpyridinium)‐20‐(4‐(butyramido‐methylcysteinyl)‐hydroxyphenyl)‐[21H,23H]‐porphine trichloride (PORTHE), derived from 5,10,15‐Tris(4‐methylpyridinium)‐20‐phenyl‐[21H,23H]‐porphine trichloride (Sylsens B) and designed for treatment of onychomycosis were characterized and their functionality evaluated. MFPSs should function as nail penetration enhancer and as photosensitizer for photodynamic treatment (PDT) of onychomycosis. Spectrophotometry was used to characterize MFPSs with and without 532 nm continuous‐wave 5 mW cm−2 laser light (± argon/mannitol/NaN3). Nail penetration enhancement was screened (pH 5, pH 8) using water uptake in nails and fluorescence microscopy. PDT efficacy was tested (pH 5, ± argon/mannitol/NaN3) in vitro with Trichophyton mentagrophytus microconida (532 nm, 5 mW cm−2). A light‐dependent absorbance decrease and fluorescence increase were found, PORTH being less photostable. Argon and mannitol increased PORTH and PORTHE photostability; NaN3 had no effect. PDT (0.6 J cm−2, 2 μm) showed 4.6 log kill for PORTH, 4.4 for Sylsens B and 3.2 for PORTHE (4.1 for 10 μm). Argon increased PORTHE, but decreased PORTH PDT efficacy; NaN3 increased PDT effect of both MFPSs whereas mannitol increased PDT effect of PORTHE only. Similar penetration enhancement effects were observed for PORTH (pH 5 and 8) and PORTHE (pH 8). PORTHE is more photostable, effective under low oxygen conditions and thus realistic candidate for onychomycosis PDT.
Seed predators exert selection on the subindividual variation of seed size
Authors: Sobral M. , Guitián J. , Guitián P. , Larrinaga A. R.
Published: October 2013

Subindividual variation among repeated organs in plants constitutes an overlooked level of variation in phenotypic selection studies, despite being a major component of phenotypic variation. Animals that interact with plants could be selective agents on subindividual variation. This study examines selective pressures exerted during post‐dispersal seed predation and germination on the subindividual variation of seed size in hawthorn (Crataegus monogyna). With a seed offering experiment and a germination test, we estimated phenotypic selection differentials for average and subindividual variation of seed size due to seed predation and germination. Seed size affects germination, growth rate and the probability of an individual seed of escaping predation. Longer seeds showed higher germination rates, but this did not result in significant selection on phenotypes of the maternal trees. On the other hand, seed predators avoided wider seeds, and by doing so exerted phenotypic selection on adult average and subindividual variation of seed size. The detected selection on subindividual variation suggests that the levels of phenotypic variation within individual plants may be, at least partly, the adaptive consequence of animal‐mediated selection.
Anatomical alterations of Phaseolus vulgaris L. mature leaves irradiated with X‐rays
Authors: De Micco V. , Arena C. , Aronne G.
Published: October 2013

The cultivation of higher plants in Space involves not only the development of new agro‐technologies for the design of ecologically closed Space greenhouses, but also understanding of the effects of Space factors on biological systems. Among Space factors, ionising radiation is one of the main constraints to the growth of organisms. In this paper, we analyse the effect of low‐LET radiation on leaf histology and cytology in Phaseolus vulgaris L. plants subjected to increasing doses of X‐rays (0.3, 10, 50, 100 Gy). Leaves irradiated at tissue maturity were compared with not‐irradiated controls. Semi‐thin sections of leaves were analysed through light and epi‐fluorescence microscopy. Digital image analysis was applied to quantify anatomical parameters, with a specific focus on the occurrence of signs of structural damage as well as alterations at subcellular level, such as the accumulation of phenolic compounds and chloroplast size. Results showed that even at high levels of radiation, general anatomical structure was not severely perturbed. Slight changes in mesophyll density and cell enlargement were detected at the highest level of radiation. However, at 100 Gy, higher levels of phenolic compounds accumulated along chloroplast membranes: this accompanied an increase in number of chloroplasts. The reduced content of chlorophylls at high levels of radiation was associated with reduced size of the chloroplasts. All data are discussed in terms of the possible role of cellular modifications in the maintenance of high radioresistance and photosynthetic efficiency.
Seasonal changes in population structure of the tropical deep‐water kelp Laminaria abyssalis
Authors: Marins Bianca V. , Amado‐Filho Gilberto M. , Barbarino Elisabete , Pereira‐Filho Guilherme H. , Longo Leila L.
Published: October 2013

Tropical kelp populations are rare and anomalous relicts of shallow‐water populations that existed during glacial periods of cooler oceanographic climate. The endemic Brazilian tropical kelp, Laminaria abyssalis Joly and Oliveira Filho, occurred at depths below 40 m. The seasonal variations in biological aspects of L. abyssalis sporophyte populations and local variations in seawater nutrients and temperature were evaluated. A population was sampled four times between the austral spring of 2005 to winter 2006. Seasonal variations in the population structure and in the tissue content of nitrogen (N), carbohydrate and pigments were observed. Higher density (6.3 individuals m−2), biomass (7.3 kg m−2) and blade area (13 221 cm2) were observed in summer, while the highest percentage of tissue total N (1.6%), carbohydrates (32.9%) and photosynthetic pigments (chlorophyll a = 1.9% and chlorophyll c = 0.4%) were observed in spring. The highest surface area of fertile tissue in L. abyssalis sporophytes (2.36%) was recorded in winter, indicating winter as the season when more investments are made in reproduction. The highest concentrations of total N (6.3 μM) and phosphate (0.6 μM) in seawater were observed in spring and summer, respectively. Seawater temperatures lower than 20°C, which are characteristic of upwelling waters, occurred every month and were most frequent in spring and summer. We show that L. abyssalis invests more in growth in spring and summer and reaches the greatest thallus size and population density in summer. The lower abundance during winter may be related to the lower frequency of temperatures below 20°C and the local seasonal storms that cause turnover of rhodoliths, the main substrate for L. abyssalis.
A Predictive Study of Dirichlet Process Mixture Models for Curve Fitting
Authors: Wade Sara , Walker Stephen G. , Petrone Sonia
Published: October 2013

This paper examines the use of Dirichlet process mixtures for curve fitting. An important modelling aspect in this setting is the choice between constant and covariate‐dependent weights. By examining the problem of curve fitting from a predictive perspective, we show the advantages of using covariate‐dependent weights. These advantages are a result of the incorporation of covariate proximity in the latent partition. However, closer examination of the partition yields further complications, which arise from the vast number of total partitions. To overcome this, we propose to modify the probability law of the random partition to strictly enforce the notion of covariate proximity, while still maintaining certain properties of the Dirichlet process. This allows the distribution of the partition to depend on the covariate in a simple manner and greatly reduces the total number of possible partitions, resulting in improved curve fitting and faster computations. Numerical illustrations are presented.
Ophthalmic diagnostic tests, orbital anatomy, and adnexal histology of the broad‐snouted caiman (Caiman latirostris)
Authors: Oriá Arianne P. , Oliveira Alberto Vinícius D. , Pinna Melissa H. , Martins Filho Emanoel F. , Estrela‐Lima Alessandra , Peixoto Tiago C. , da Silva Renata Maria M. , Santana Fernanda O. , Meneses Íris Daniela S. , Requião Kátia G. , Ofri Ron
Published: October 2013

Purpose

The aim of this study was to establish normal ophthalmic parameters for selected diagnostic tests, and to describe the orbital anatomy and adnexal histology of the broad‐snouted caiman.

Method

A total of 35Caiman latirostristhat were free of obvious ocular diseases were used to measure the parameters in this investigation. Ages ranged from 5 to 15 years. Ophthalmic diagnostic tests were conducted, including evaluation of tear production with Schirmer Tear test‐1 (STT1), culture of the conjunctival bacterial flora, applanation tonometry, conjunctival cytology, nictiating membrane incursion frequency test (NMIFT), endodontic absorbent paper point tear test (EAPPTT), palpebral fissure length measurement (PFL) and B‐mode ultrasonography. Adnexal histology and skull samples were studied.

Results

Mean (±SD)STT1 was 3.4 ± 3.6 mm/min (95% confidence interval of 2.01–4.78 mm/min), intraocular pressure (IOP) was 12.9 ± 6.2 mmHg,NMIFTwas 6.0 ± 3.5,EAPPTTwas 17.1 ± 2.5 mm/min,PFLwas 28.9 ± 3.0 mm, anterior chamber depth was 3.1 ± 0.3 mm, lens axial length was 8.4 ± 0.6 mm, vitreous chamber depth was 7.9 ± 0.7 mm and axial globe length was 19.9 ± 1.3 mm. For all animals evaluated,Bacillussp., Diphteroids andStaphylococcussp. were predominant.
Histopathological features of equine superficial, nonhealing, corneal ulcers
Authors: Hempstead Julie E. , Clode Alison B. , Borst Luke B. , Gilger Brian C.
Published: October 2013

Objective

To evaluate corneal changes associated with chronic, nonhealing, superficial, corneal ulcers in horses via common histopathological stains.

Design

Retrospective study.

Animals

Twenty‐four horses diagnosed with chronic, nonhealing, superficial, corneal ulceration.

Methods

The medical records of horses evaluated at North Carolina State University's Veterinary Teaching Hospital (NCSU‐VTH) from 2005 to 2011, diagnosed with a chronic, nonhealing, superficial, corneal ulcer and treated with superficial keratectomy (SK) were reviewed. Inclusion criteria were superficial corneal ulceration, no cellular infiltration via slit‐lamp biomicroscopy, no microorganisms evident on corneal cytology, and acquisition of samples for aerobic bacterial and common fungal cultures. Corneal tissue samples were evaluated histopathologically for the presence or absence of a nonadherent epithelial ‘lip’, epithelial dysmaturity, intraepithelial inflammatory cells, an acellular hyaline zone in the anterior stroma, and stromal inflammatory cells, fibrosis and vascularization.

Results

In the majority of analyzed samples, epithelial cells adjacent to the ulcerated site showed nonadherence to the basement membrane and dysmaturity. Intraepithelial inflammatory cell infiltration was uncommon. Histopathological features of an anterior stromal hyaline zone, intrastromal inflammation, fibrosis and vascularization were variably present.

Conclusions

The most consistent histopathological characteristics of equine chronic, nonhealing, superficial, corneal ulcers include epithelial nonadherence, epithelial dysmaturity and mild to moderate stromal inflammation; however, one set of histopathological characteristics does not definitively define this syndrome in horses. Additionally, the anterior stromal acellular hyaline zone commonly cited in canine spontaneous chronic corneal epithelial defects (SCCED) is not a consistent finding in equine corneas.
A Basis for Selecting the Most Appropriate Small Specimen Creep Test Type
Authors: Hyde T. H. , Hyde C. J. , Sun W.
Published: October 2013

Many components in conventional and nuclear power plant, aero-engines, chemical plant etc., operate at temperatures which are high enough for creep to occur. These include plain pipes, pipe bends, branched pipes etc., the manufacture of such components may also require welds to be inserted in them. In most cases, only nominal operating conditions (i.e., pressure, temperatures, system load, etc.) are known and hence precise life predictions are not possible. Also, the proportion of life consumed will vary from position to position within a component and the plant. Hence, nondestructive techniques are adopted to assist in making decisions on whether to repair, continue operating or scrap certain components. One such approach is to use scoop samples removed from the components to make small creep test specimens, i.e., sub-size uniaxial creep test specimens, impression creep test specimens, small punch creep test specimens, and small ring (circular or elliptical) creep test specimens. Each specimen type has its own unique advantages and disadvantages and it may not be obvious which one is the most appropriate test method to use. This paper gives a brief description of each specimen and associated test type and describes their practical limitations. The suitability of each of the methods for determining “bulk” material properties is described and it is shown that an appropriate test type can be chosen.
Time Domain Wave Packet Method and Suppression of Instability Waves in Aeroacoustic Computations
Authors: Hu Fang Q. , Li X. D. , Li X. Y. , Jiang M.
Published: October 2013

A new time domain methodology for Computational Aeroacoustics (CAA) is proposed. The time domain wave packet (TDWP) method employs a temporally compact broadband pulse for acoustic sources. As the radiation and transmission of acoustic waves of all frequencies within the numerical resolution are embedded in the propagation of the wave packet, acoustic solution of the full spectrum become available at once. In addition, it becomes possible to separate the acoustic and instability waves in shear flows in the time domain wave packet method due to the compactness of the wave packet. The instability waves can further be suppressed by a source filtering technique, applied after the acoustic wave packet has propagated through the shear layers. Details on the source filtering technique used in the paper are presented. The TDWP method has been validated using a CAA Benchmark problem. The TDWP method is also applied to the NASA/GE Fan Noise Source Diagnostic Test (SDT) exhaust radiation problem.
Dynamic Analysis of a Floating Offshore Wind Turbine Under Extreme Environmental Conditions
Authors: Utsunomiya Tomoaki , Yoshida Shigeo , Ookubo Hiroshi , Sato Iku , Ishida Shigesuke
Published: October 2013

This paper is concerned with the development of a floating offshore wind turbine (FOWT) utilizing spar-type floating foundation. In order to design such a structure, it is essential to evaluate the dynamic response under extreme environmental conditions. In this study; therefore, a dynamic analysis tool has been developed. The dynamic analysis tool consists of a multibody dynamics solver (MSC.Adams), aerodynamic force evaluation library (NREL/AeroDyn), hydrodynamic force evaluation library (in-house program named SparDyn), and mooring force evaluation library (in-house program named Moorsys). In this paper, some details of the developed dynamic analysis tool are given. In order to validate the program, comparison with the experimental results, where the wind, current, and wave are applied simultaneously, has been made. In this paper, only parked conditions are considered. The comparison shows that the principal behavior of the floating offshore wind turbine with spar platform has been captured by the developed program. However, when vortex-induced motion (VIM) occurs, the current loads and cross-flow responses (sway and roll) are underestimated by the simulation since the simulation code does not account for the effect of VIM.
Constrained Design Optimization of Vibration Energy Harvesting Devices
Authors: Hendijanizadeh Mehdi , Moshrefi-Torbati Mohamed , Sharkh Suleiman M.
Published: October 2013

Existing design criteria for vibration energy harvesting systems provide guidance on the appropriate selection of the seismic mass and load resistance. To harvest maximum power in resonant devices, the mass needs to be as large as possible and the load resistance needs to be equal to the sum of the internal resistance of the generator and the mechanical damping equivalent resistance. However, it is shown in this paper that these rules produce suboptimum results for applications where there is a constraint on the relative displacement of the seismic mass, which is often the case. When the displacement is constrained, increasing the mass beyond a certain limit reduces the amount of harvested power. The optimum load resistance in this case is shown to be equal to the generator's internal resistance. These criteria are extended to those devices that harvest energy from a low-frequency vibration by utilizing an interface that transforms the input motion to higher frequencies. For such cases, the optimum load resistance and the corresponding transmission ratio are derived.
Metaheuristic Design and Optimization of Fuzzy-Based Gas Turbine Engine Fuel Controller Using Hybrid Invasive Weed Optimization/Particle Swarm Optimization Algorithm
Authors: Mohammadi E. , Montazeri-Gh M. , Khalaf P.
Published: October 2013

This paper presents the metaheuristic design and optimization of fuzzy-based gas turbine engine (GTE) fuel flow controller by means of a hybrid invasive weed optimization/particle swarm optimization (IWO/PSO) algorithm as an innovative guided search technique. In this regard, first, a Wiener model for the GTE as a block-structured model is developed and validated against experimental data. Subsequently, because of the nonlinear nature of GTE, a fuzzy logic controller (FLC) strategy is considered for the engine fuel system. For this purpose, an initial FLC is designed and the parameters are then tuned using a hybrid IWO/PSO algorithm where the tuning process is formulated as an engineering optimization problem. The fuel consumption, engine safety, and time response are the performance indices of the defined objective function. In addition, two sets of weighting factors for objective function are considered, whereas in one of them savings in fuel consumption and in another achieving a short response time for the engine is a priority. Moreover, the optimization process is performed in two stages during which the database and the rule base of the initial FLC are tuned sequentially. The simulation results confirm that the IWO/PSO-FLC approach is effective for GTE fuel controller design, resulting in improved engine performance as well as ensuring engine protection against physical limitations.
Exergetic Assessment of a Syngas-Redox-Based IGCC Plant for Generating Electricity
Authors: Sorgenfrei M. , Tsatsaronis G.
Published: October 2013

Carbon capture from advanced integrated gasification combined-cycle (IGCC) processes should outperform conventional coal combustion with subsequent CO2 separation in terms of efficiency and CO2 capture rates. This paper provides a thermodynamic assessment, using an exergy analysis of a syngas redox (SGR) process for generating electricity. The power island of the proposed process uses syngas produced by coal gasification and is then cleaned through a high-temperature gas desulfurization (HGD) process. Hematite (Fe2O3) is used as an oxygen carrier to oxidize the syngas. To achieve a closed-cycle operation, the reduced iron particles are first partially re-oxidized with steam and then fully re-oxidized with pressurized air. One advantage of this design is that the resulting hydrogen (using steam in the re-oxidation section) can be utilized within the same plant or be sold as a secondary product. In the proposed process, diluted hydrogen is combusted in a gas turbine. Heat integration is central to the design. Thus far, the SGR process and the HGD unit are not commercially availiable. To establish a benchmark, the rate of exergy destruction within the SGR process was compared to a coal-fed Shell gasification IGCC design with Selexol-based precombustion carbon capture. Some thermodynamic inefficiencies were found to shift from the gas turbine to the steam cycle and redox system, while the net efficiency remained almost the same. A process simulation was undertaken, using Aspen Plus and the engineering equation solver (EES).
The Impact of Hole Depth on the Rotordynamic and Leakage Characteristics of Hole-Pattern-Stator Gas Annular Seals
Authors: Childs Dara W. , Arthur Stephen , Mehta Naitik J.
Published: October 2013

Test results are presented for rotordynamic characteristics of hole-pattern-stator annular gas seals at a 70 bar supply pressures with a running speed of 20,200 rpm. Leakage results are presented for these conditions and the additional speeds: 10,200 and 15,300 rpm. Hole-depth is the principal test variable of interest. Most published annular test data for these seals have a hole diameter of 3.175 mm and a hole depth of 3.302 mm. For this work, with the 3.175 mm hole diameter, additional results are presented for shallow (1.905 mm) and deep (6.604 mm) hole depths. Test results show a pronounced dependence of leakage and rotordynamic behavior on hole depth. Test results show much better leakage performance for the shallow-hole-depth seal in both leakage and rotordynamic performance. Compressor manufacturers and users will need to decide whether this observed performance improvement is worth trying in real machines.
An Improved Catcher Bearing Model and an Explanation of the Forward Whirl/Whip Phenomenon Observed in Active Magnetic Bearing Transient Drop Experiments
Authors: Wilkes Jason , Moore Jeff , Ransom David , Vannini Giuseppe
Published: October 2013

Though many approaches have been proposed in the literature to model the reaction forces in a catcher bearing (CB), there are still phenomena observed in experimental tests that cannot be explained by existing models. The following paper presents a novel approach to model a CB system. Some of the elements in the model have been previously introduced in the literature; however, there are other elements in the proposed model that are new, providing an explanation for the forward whirling phenomena that has been observed repeatedly in the literature. The proposed CB model is implemented in a finite-element rotordynamic package, and nonlinear time-transient simulations are performed to predict published experimental results of a high-speed vertical subscale compressor; with no other forces present in the model, the agreement between simulations and experimental data is favorable. The results presented herein show that friction between the journal and axial face of the catcher bearing results in a forward cross-coupled force that pushes the rotor in the direction of rotation. This force is proportional to the coefficient of friction between the axial face of the rotor and catcher bearing and the axial thrust on the rotor. This force results in synchronous whirl when the running speed is below a combined natural frequency of the rotor-stator system and constant frequency whip when the speed is above a whip frequency.
Experimental Identification of Force Coefficients of Large Hybrid Air Foil Bearings
Authors: Wang Yu Ping , Kim Daejong
Published: October 2013

Foil bearing technology using air or gas as a lubricant has been around since the mid-1960s, and it made significant progress in its reliability, performance, and applications. Even if significant progress has been made to the technology, the commercial applications to relatively large machines with journal shaft diameter bigger than 100 mm was not reported. This paper presents dynamic characteristics of a hybrid (hydrodynamic + hydrostatic) air foil bearing (HAFB) with a diameter of 101.6 mm and a length of 82.6 mm. The test rig configuration in this work is a floating HAFB on a rotating shaft driven by electric motor, and the HAFB is under external load. HAFB stiffness coefficients were measured using both (1) time-domain quasi-static load-deflection curves and (2) frequency-domain impulse responses, and HAFB damping coefficients were measured using only impulse responses. The HAFB direct stiffness coefficients measured from both methods are close to each other in the range of 4∼7 MN/m depending on speed, load, and supply pressure, but frequency domain method shows larger scatter in the identified coefficients. HAFB coefficients simulated with the linear perturbation method using a bump stiffness matched to the load-deflection characteristics at 18,000 rpm show reasonably good agreements with experimentally measured values.
Experimental Investigations and Analytical Improvements for HTR Pebble Bed Cores
Authors: Allelein H.-J. , Schloegl B. , Baggemann J. , Juehe S. , Kasselmann S.
Published: October 2013

One of the main research topics of the Chair for Reactor Safety and Technology at RWTH Aachen University and the Institute for Nuclear Waste Management and Reactor Safety (IEK-6) deals with accident scenarios of gas-cooled High-Temperature Reactors, especially the air ingress scenario. Two experimental facilities have just started operation providing experimental data for the validation and improvement of fluid mechanics codes being developed and applied at IEK-6. The INDEX (INDuction EXperiment) facility is able to heat up single spheres inductively up to 1200°C while exposed to defined gas atmospheres and gas flow conditions. This experimental setup is well suited to study pebble / gas flow interactions as well as graphite corrosion phenomena in detail. The NACOK II (NAturzug im COre mit Korrosion) facility is an integral experiment for fluid mechanics and graphite corrosion processes under natural convection effects. It will examine spherical fuel element samples as well as prismatic blocks. In addition the instrumentation is suitable for CFD validation calculations, for example because PIV (particle image velocity) is applied. The data obtained are used to validate and improve computational fluid dynamics (CFD) models for pebble bed reactors or reactor dynamics code like MGT-3D, which are able to simulate air ingress scenarios. The CFD model shall be able to simulate the fluid mechanics as well as the corrosion processes of after a total pressure release. In this paper we report on the status of the experimental facilities as well as on advances in modelling the fluid mechanics of HTR pebble cores.
Flow Instability Inside Heat Transfer Tubes of MSR
Authors: Manabe Jun
Published: October 2013

Moisture separator reheater for nuclear steam turbine system of light water reactor, a combined equipment of mist separator and in-tube side condensing multi-tube type heat exchanger, has an inherent issue of flow instability inside the tubes. The issue causes the temperature oscillation and possible thermal fatigue at tube to tube-sheet welding of the tube outlet end. Construction of its heat transfer is that heating main steam supplied by NSSS inside the tubes transfers its latent heat by condensing to the colder high pressure turbine exhaust steam cooling outside of the tubes. The condensed water is exhausted by friction of venting excess steam through the tubes which makes the flow in tubes gas-liquid two phase regime and results the steady drainage without sub-cooling and associated temperature oscillation at tube end. A measuring was conducted on MSR of an existing 600 MW class unit to clarify the unstable behaviors without excess steam, which showed the temperature oscillation at tube end with synchronizing to oscillation of both pressure difference between tube inlet and outlet chambers and tube surface temperature along the tube. The cycle and the amplitude of the temperature oscillation were 55 second and 40K. Only the effects of venting steam for the actual unit and presumption of the mechanism of subcool were reported in the original paper, Journal of Engineering for Gas Turbines and Power 2010 Vol. 132/ 102905, here is added qualitative and quantitative study for both dynamics of the condensed water and behavior at tube outlet end to assess adequacy of the mechanism.
Comparative Study in the Stability Analysis Code of LAPUR5.2 and LAPUR6.0 for the Kuosheng NPP
Authors: Hsieh Chang-Lung , Chen Guan-Yu , Shih Chunkuan , Wang Jong-Rong , Lin Hao-Tzu
Published: October 2013

Under certain conditions, boiling water reactors (BWRs) would be susceptible to couple neutron-thermalhydraulic instability. It is important to predict such potential problems as early as possible and prevent the core instability from happening. In each BWR reload core design, fuel vendors are required to provide instability boundaries on power/flow map to assure safety operation of the nuclear reactor. In Taiwan, a LAPUR5.2 methodology had been adapted to build up the remarkable analysis mode for different types BWRs to verify vendor’s results. However, with upgrading nuclear safety technology, most of boiling water reactors has been adopting partial length fuel assemblies to reduce two-phase pressure drop and void fraction, to improve reactor stability. The question is that LAPUR5.2 methodology cannot precisely analysis stability characteristics from the variation of flow area in fuel assemblies. From the reasons of upgrading stability analysis, a LAPUR6.0 methodology had built to do the related researches. This research was based on a comparison study between LAPUR5.2 and LAPUR6.0 to realize the major differences and their effects on stability characteristics. According to the comparison results for Kuosheng Nuclear Power Plant Unit 2 Cycle 21 reload design, it shows that LAPUR6.0 can completely present pressure drop, void fraction and density reactivity coefficient from the changing of flow area and fuel spacers.
Structure Design of Pressure Equipment for Experimental Test on Steam Condensation on the Cold Surface
Authors: Yang Lin , Li Lingyun , Han Liyong
Published: October 2013

The advanced pressurized water reactor (APWR) designed by Westinghouse uses a passive safety system which relies on heat removal by condensation to maintain the containment within the design limits of pressure and temperature. Steam condensation inside surface of the containment is one of the most important phenomena during heat removing process in the passive containment cooling system (PCCS). It is very significant for engineering design and code development to study the mechanism of steam condensation on cold surface. There was an experiment done by University of Wisconsin on this subject. However, the pressure equipment cannot support high pressure. In this paper, new pressure equipment was designed. It can support higher pressure and also meet other thermal measurement requirements.
Calculations of the Dual Functional Lithium Lead-Test Blanket Module for ITER With Three-Dimensional Deterministic Method
Authors: Zhang GuangChun , Wu Hongchun , Cao Liangzhi , Zheng Youqi
Published: October 2013

Neutronics calculations and analysis of ITER test blanket module lay the foundation for the design, construct and experiment of ITER. In this paper, the realistic 3D neutronics calculations of the dual functional lithium lead-test blanket module (DFII-TBM) have been carried out by means of the 3D MOC code and the SPN code, which are both deterministic methods and developed by NECP lab, adopting the multi-group nuclear data library FENDI/MG-2.1. The main features of the TBM nuclear response are assessed, paying a particular attention to the neutron flux and tritium production rate.

The 3DMOC code is a coupling a 3D method of characteristics (MOC) to the common geometry module. It could calculate the flux throughout three-dimensional systems by the MOC, which has been proved a very flexible and effective method for the neutron transport calculation in a complex geometry. In this code, a modular ray tracing technique is adopted to reduce the amount of the ray tracing data and the Coarse Mesh Finite Difference (CMFD) acceleration method is employed to save computing time, which could well solve the difficulties when applying MOC in three-dimensional geometries.

The SPN code is another three-dimensional Boltzmann transport equation calculation code. The simplified PN method is used to treat the directional variable, and the Nodal method treats the spatial variable. Consequently, this code has an advantage in shorting computing time when applied to big geometry problems.

Considering the big geometry of DFII-TBM and the large number of the cross sections of nuclear data library FENDI/MG-2.1, a two-step approach is adopted. Firstly, the DFII-TBM is dissected into some typical independent parts. 3D calculations are performed on these parts respectively with 3D MOC code and FENDL/MG-2.1 library to obtain the detailed heterogeneous flux distribution. Then the homogenization is carried out to calculate the average homogeneous cross sections, followed by the use of homogeneous cross sections to calculate the flux distribution throughout the DFII-TBM with SPN code.

The results obtained are herewith presented and critically discussed.
Surface Tension of Liquid Sodium With Suspended Nanoparticles
Authors: Ogawa Takuro , Sugiyama Ken-ichiro
Published: October 2013

Liquid sodium to be described by sodium here after with suspended nanoparticles is expected to mitigate sodium-water reaction, because sodium with suspended nanoparticles will suppress the degree of chemical activity by the atomic interaction between nanoparticles and sodium. In order to investigate this interaction from the view point of physical property, we tried to measure the surface tension of sodium with suspended nanoparticles in a static and dynamic state.

For the measurement of the surface tension in a static state, we employed the pendant drop method. The measurements were done in the globe box keeping inert gas atmosphere, which was required for the experiment using sodium to get rid of an easy chemical reaction of sodium with oxygen and moisture. We succeeded to make pendant drops of sodium and sodium with suspended nanoparticles between 200°C and 500°C.

On the other hand, to evaluate the surface tension in a dynamic state, we employed the method applying the principle of the Kelvin-Helmholtz instability. The measurements were done in the globe box used in the static experiment. Sodium or sodium with suspended nanoparticles throwing a nozzle was ejected into a paraffin pool. Its fragments were made due to the Kelvin-Helmholtz instability. The fragments were retrieved from a paraffin pool and we measured fragment size distribution. We carried out the experiments at temperature of 150°C and 200°C, and the ejection volume rate of 3.0L/min and 6.0L/min.

It was found that droplet sizes of sodium with suspended nanoparticles were increased as compared with those of sodium without nanoparticles. This result physically must have mean that sodium with suspended nanoparticles has larger surface tension than that of sodium without nanoparticles in the present condition. Therefore, we could consider the effect of the atomic interaction might mitigate sodium-water reaction.
IVR Model Study for Passive PWR
Authors: Xu Hong , Zhang Peng , Zhou Zhiwei
Published: October 2013

1000-MWe scale Pressurized Water Reactor (PWR) is taking service or under construction all over the world, and larger scale plant is studied and developed for its more competitive economics. Not only design basic accidents are analyzed for nuclear safety, the severe accident must also be considered to meet with the increasing requirement of safety. In the “nuclear power plant design safety regulation” (HAF102) issued by Nation Nuclear Safety Administration (NNSA), aim at the preventing and mitigating of severe accident, the regulation bring forward new requirement, which required that during design phase, NPP should consider setting the preventing and mitigation measurement of severe accident as actually as possible. As an approach to prevent the curium from melting down the vessel and entering the containment when a postulated severe accident occurs, In-vessel retention (IVR) of molten core debris via water cooling of the external surface of the reactor vessel has been introduced into AP1000.

External reactor vessel cooling (ERVC) is assumed to be achieved keeping exterior surface of vessel at 400K. It is known to all that different scenario and process results in different IVR molten model. As the core melt, different IVR model is formed at different time, such as two-layer model, three-layer model and four layer model. It is necessary to study the IVR model when severe accident process moves on. This paper studies two-layer and three-layer IVR models and find the features of the models. Based on this, sensitivity study of important parameters has also been analyzed. It is useful for us to understand the mechanism of the molten pool. This paper has some directive significance on future IVR strategy research and also provides theoretical support to safety evaluation of PWR plants.
Investigation of Liquid Dispersion in the Packed-Bed by Electrical Resistance Tomography
Authors: Eda Takeshi , Sapkota Achyut , Takei Masahiro
Published: October 2013

Revealing gas-liquid permeable flow phenomena in the porous media is helpful for the environmental impact assessment of geological disposal of radioactive waste and purification of radioactive contamination water. This paper aims to investigate the liquid phase dispersion inside co-current downward gas-liquid flow in the bed packed with spherical particle as basic model. Water and air are injected from the top center of column, and water is spreading to the entire cross-section flowing down along the column. Radial dispersion of water is captured by electrical resistance tomography on several axial positions. The results indicated that liquid flow rate have impact on radial dispersion of water.
Role of Complicated Flow Fields in Lower Plenum on Coolant Flow Distribution to Core of ABWR
Authors: Watanabe Shun , Abe Yutaka , Kaneko Akiko , Watanabe Fumitoshi , Hirao Kazuki
Published: October 2013

In order to achieve increase of power outputs of an ABWR, it is extremely important to evaluate coolant flow in a lower plenum. Numerical simulation is helpful to predict the coolant flow, and thus verification experiments are needed. Hence, the present study is focusing on the construction of benchmark of CFD code. The objective of the study is to clarify relation between flow distribution to the core and the complicated flow structures in the lower plenum.

We constructed a 1/10 model of a lower plenum to conduct flow experiment for validation of CFD analysis. In the experiment, it turned out that coolant flow distribution becomes to be uniform at core support beam, and there are complicated flows like vortices around side entry orifices. Regarding differential pressure distribution, it was revealed that profile of the region including side entry orifices is very dominant. This pressure loss might be caused by contraction flow at the orifices. Such flow structures were also described by CFD analysis. As good performance of analysis, we investigated flow distribution to the core particularly by using CFD results. And relation between the flow distribution and the complicated flow structures were also discussed.
Effects of Various Fuel Parameters on the HTTR Criticality Calculations
Authors: Li Chun-Yen , Sheu Rong-Jiun , Peir Jinn-Jer , Chao Der-Sheng , Liang Jenq-Horng
Published: October 2013

The high temperature engineering test reactor (HTTR) in Japan is a 30 MWth helium-cooled and graphite-moderated reactor that was built to demonstrate the technological feasibility and advantages for the next-generation high-temperature gas-cooled reactors. The multi-level heterogeneous configuration of the HTTR core represents challenges to reactor physics calculations. A suitable core model is of vital significance for reliable neutronic analyses of the HTTR. In this study, a detailed HTTR core model is constructed based on the MCNP5 Monte Carlo code and the ENDF/B-VII neutron cross-section library. For code and model validation, several HTTR benchmark calculations were performed first and compared with the experimental results. After that, a variety of fuel design was explored to investigate their effects on the HTTR criticality calculations. The fuel design or parameters under consideration include the moderator-to-fuel ratio in the core, fuel rod dimension, and different fissile materials. The resultant trend of change in system multiplication factor and neutron spectrum was presented and discussed in this paper.
Integration of Direct/Indirect Influences of Severe Accidents for Improvements of Nuclear Safety
Authors: Silva Kampanart , Ishiwatari Yuki , Takahara Shogo
Published: October 2013

Risk evaluation is an important assessment tool of nuclear safety, and a common index of direct/indirect influences of severe accidents as a compound of risk is necessary then. In this research, various influences of severe accidents are converted to monetary value and integrated. The integrated influence is calculated in a unit of “cost per severe accident” and “cost per kWh”. The authors must emphasize that the aim is not to estimate the accident cost itself but to extend the scope of “risk-informed decision making” for continuous safety improvements of nuclear energy.

To calculate the “cost per severe accident” and the “cost per kWh”, typical sequences of severe accidents are picked-up first. Containment failure frequency (CFF) and source terms of each sequence are taken from the results of level 2 probabilistic risk assessment (PRA). The source terms of each sequence is input into the level 3 PRA code OSCAAR which was developed by Japan Atomic Energy Agency (JAEA). The calculations have been made for 248 meteorological sequences, and the results presented in this study are given as expectation values for various meteorological conditions. Using these outputs, the cost per severe accident is calculated. It consists of various costs and other influences converted into monetary values.

This methodology is applied to a virtual 1,100 MWe BWR-5 plant. Seismic events are considered as the initiating events. The data obtained from the open documents on the Fukushima Accident are utilized as much as possible. Sensitivity analyses are carried out to identify the dominant influences, sensitive assumptions/parameters to the cost per accident or per kWh. Based on these findings, optimization of radiation protection countermeasures is recommended. Also, the effects of sever accident management are investigated.
Mechanical Aspects of the Canadian Generation IV Supercritical Water-Cooled Pressure Tube Reactor
Authors: Yetisir M. , Gaudet M. , Martin D.
Published: October 2013

Canada is developing a next generation (Gen IV) reactor, the Canadian Super-Critical Water-cooled Reactor (SCWR), which has the potential of meeting all design goals of the Gen IV International Forum (GIF). These design goals include enhanced safety features (inherent safe operation and deploying passive safety features), improved economic and resource utilization (∼40% more efficient than current nuclear power generating stations, sustainable fuel cycle (will burn thorium, which is three times more abundant than uranium), enhanced sustainability, and greater proliferation resistance compared to the current fleets (i.e., Gen III and Gen III+) of reactors. The Canadian SCWR concept is a pressure-tube type reactor that uses supercritical water as a coolant, a separate low-pressure heavy water moderator, a high efficiency fuel channel that includes a zirconium alloy pressure and a ceramic zirconia insulator, and a direct steam power cycle.

This paper presents the evolution of the Canadian SCWR core design, simplifications introduced in the design to deal with design challenges, and ongoing design activities.
Estimation of Thyroid Doses From Land Contamination Maps for the Fukushima Disaster
Authors: Saji Genn
Published: October 2013

Starting with sketchy information acquired during the still on-going Fukushima Daiichi disaster, the thyroid doses were estimated, based on the detailed and precise Cs-137 land contamination density maps constructed through a joint effort of MEXT and US DOE/NNEA. The basic methodology has already been benchmarked in the assessment of the radiological consequences of the Chernobyl accident [1].

From the release fraction assessment based on the contamination maps as well as on-site meteorological data obtained and reported by TEPCO’s temporary monitoring cars, the heavy land contamination zone stretching to a NW direction was found induced with the hydrogen explosion which occurred in 1F1 at 15:36 of March 12, only one day after the tsunami. Due to this early iodine release, the shorter half-lived I-133 induced an additional 20% more thyroid doses from I-131 through inhalation.

The results, as presented in Table 7 and Figure 3, predicted rather large thyroid doses, comparable but less than the author’ previous estimation of thyroid doses through inhalation pathway among the public living near the Chernobyl NPP during the disaster. However, age specific doses are more widely spreading among children aged less than 15 years old and not distinctively large among babies, thanks to early restriction of fresh milk.

It should be noted that, above Zone V (300K-1000K/m2 in Cs-137), the estimated thyroid doses with a range of several tens of mGy are already of concern in a possible future outbreak of hypothyroidism. However, if the exposed individuals happened to be staying indoors at the time of plume passage, an order of magnitude of reduction is expected, although the alleviating effects depends on the airtightness of buildings.

Even with these uncertainties, the estimated thyroid dose calls for continued health monitoring of those young residents who happened to be staying in these highly contaminated zones at the time of the plume passage.