bluuebunny/crossref_metadata_2025 huggingface dataset:
Animal Scavenging and Scattering and the Implications for Documenting the Deaths of Undocumented Border Crossers in the Sonoran Desert,
Authors: Beck Jess , Ostericher Ian , Sollish Gregory , De León Jason
Published: November 2014

Since 1998, over 5500 people have died while attempting to cross the U.S.–Mexico border without authorization. These deaths have primarily occured in the Arizona desert. Despite the high volume of deaths, little experimental work has been conducted on Sonoran Desert taphonomy. In this study, pig carcasses were used as proxies for human remains and placed in different depositional contexts (i.e., direct sunlight and shade) that replicate typical sites of migrant death. Decomposition was documented through daily site visits, motion‐sensitive cameras and GIS mapping, while skeletal preservation was investigated through the collection of the remains and subsequent faunal analysis. Our results suggest that vultures and domestic dogs are underappreciated members of the Sonoran scavenging guild and may disperse skeletal remains and migrant possessions over 25 m from the site of death. The impact of scavengers and the desert environment on the decomposition process has significant implications for estimating death rates and identifying human remains along the Arizona/Mexico border.
The Importance of Microscopic Examination of the Lungs in Decedents with Sustained Central Intravascular Catheters: A Nine‐Case Series
Authors: Hamilton Heidi H. , Batalis Nicholas I. , Presnell Susan E. , Schandl Cynthia A. , Tormos Lee Marie
Published: November 2014

Indwelling intravascular catheters provide convenient access to healthcare personnel and also recreational intravenous drug users who inject suspensions of oral medications. A nine‐case series of autopsies of clinically stable decedents with indwelling catheters and sudden death is herein presented. Pulmonary histologic findings were consistent with intravenous administration of oral medications in all cases. In eight, the mechanism of death was directly attributed to occlusive vascular embolization of foreign material, with or without contribution of acute drug toxicity. In one, the mechanism of death was solely attributed to acute drug toxicity. Acute, massive embolization of foreign material may explain sudden death by vascular obstruction, whereas chronic repeated injections lead to obliteration of the pulmonary vasculature, increased pulmonary vascular resistance, and cardiac failure. Therefore, a complete autopsy with histologic examination of the lungs and toxicology testing is recommended in patients with indwelling catheters to determine the cause and mechanism of death.
Periodontal and peri‐implant microbiota in patients with healthy and inflamed periodontal and peri‐implant tissues
Authors: Zhuang Long‐Fei , Watt Rory M. , Mattheos Nikos , Si Mi‐Si , Lai Hong‐Chang , Lang Niklaus P.
Published: November 2014

Objective

To compare the prevalence and levels of six bacterial pathogens within the subgingival/submucosal microbiota at teeth versus implants with various clinical conditions.

Material and methods

Twenty‐two Chinese were included. Four subgingival/submucosal sites were selected for microbiological sampling within each subject, that is, (1) healthy peri‐implant tissues; (2) peri‐implantitis [PPD ≥ 5 mm, presence of bleeding on probing (BOP) and confirmed radiographic bone loss]; (3) healthy gingiva; and (4) periodontitis (PPD ≥4 mm). Subgingival/submucosal plaque was sampled using paper points. Quantitative real‐time polymerase chain reaction (q‐PCR) was used to quantify six pathogens, including Porphyromonas gingivalis (P.g.), Treponema denticola (T.d.), Aggregatibacter actinomycetemcomitans (A.a.), Fusobacterium nucleatum (F.n.), Prevotella intermedia (P.i.), and Staphylococcus aureus (S.a.). Counts were log10‐transformed.

Results

The most commonly detected species were S. a. and F. n., while A. a. and. P. i. had the lowest detection frequency. The detection frequencies of diseased tooth or implant sites for each of the six target species were either equal to or higher than the respective frequencies at the corresponding healthy sites. There were no statistically significant differences for any of the species or clinical sites (P > 0.05, Cochran's Q test). No statistically significant differences in the bacterial loads were found among the four clinical sites; with the exception of F. nucleatum. This was more abundant in periodontitis sites (P = 0.023, Friedman's 2‐way anova). Both periodontal and peri‐implant sites, irrespective of their health status, were revealed to harbor S. aureus cells. The log10‐transformed loads of S. aureus were approximately 3.5 within each of the clinical sites (P = 0.232). This was the highest of the six species analyzed.

Conclusions

Within the same subjects, putative periodontal pathogens were common to both periodontal and peri‐implant sites irrespective of health status. The prevalence and levels of P. gingivalis and F. nucleatum were significantly associated with periodontitis, but not with peri‐implantitis. A. actinomycetemcomitans was associated with both disease conditions, periodontitis and peri‐implantitis, but not with either gingival or mucosal health.
Ground‐ and satellite‐based evidence of the biophysical mechanisms behind the greening Sahel
Authors: Brandt Martin , Mbow Cheikh , Diouf Abdoul A. , Verger Aleixandre , Samimi Cyrus , Fensholt Rasmus
Published: November 2014

After a dry period with prolonged droughts in the 1970s and 1980s, recent scientific outcome suggests that the decades of abnormally dry conditions in the Sahel have been reversed by positive anomalies in rainfall. Various remote sensing studies observed a positive trend in vegetation greenness over the last decades which is known as the re‐greening of the Sahel. However, little investment has been made in including long‐term ground‐based data collections to evaluate and better understand the biophysical mechanisms behind these findings. Thus, deductions on a possible increment in biomass remain speculative. Our aim is to bridge these gaps and give specifics on the biophysical background factors of the re‐greening Sahel. Therefore, a trend analysis was applied on long time series (1987–2013) of satellite‐based vegetation and rainfall data, as well as on ground‐observations of leaf biomass of woody species, herb biomass, and woody species abundance in different ecosystems located in the Sahel zone of Senegal. We found that the positive trend observed in satellite vegetation time series (+36%) is caused by an increment of in situ measured biomass (+34%), which is highly controlled by precipitation (+40%). Whereas herb biomass shows large inter‐annual fluctuations rather than a clear trend, leaf biomass of woody species has doubled within 27 years (+103%). This increase in woody biomass did not reflect on biodiversity with 11 of 16 woody species declining in abundance over the period. We conclude that the observed greening in the Senegalese Sahel is primarily related to an increasing tree cover that caused satellite‐driven vegetation indices to increase with rainfall reversal.
Effects of larval density and food stress on life‐history traits of Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)
Authors: Yang F. , Hu G. , Shi J. J. , Zhai B. P.
Published: November 2014

High population density and nutrition restriction can lead to phase variation in morphology and development, and subsequently induce changes in the reaction norms of adult flight in migrant insects. However, response of migratory propensity to such stress in Endopterygote insects, especially in several species of Lepidoptera, remains unclear. In this study, larval and adult developmental responses to crowding and food stress were investigated in the migratory moth, Cnaphalocrocis medinalis (Guenée). A high larval rearing density significantly reduced pupal mass, survival rate and female fecundity. Larvae developed rapidly under crowding conditions, and time to pupation was 2 days earlier than individuals reared alone. By contrast, short‐term starvation and associated compensatory growth prolonged larval duration by 3–4 days and pupal duration by 1–2 days. It also reduced the pupal mass, but showed no detectable effects on female reproductive performance. Both sexes had similar development strategies; however, females seemed to be more sensitive to crowding and food shortage than males. A positive effect was expected if such stress factors acted as cues that triggering a behavioural or physiological shift to a distinct migratory phase. To the contrary, we found no proof that crowding and starvation caused maturation delay in female reproductive development. All treatments did not significantly increase female pre‐oviposition period. Therefore, we concluded that life developmental responses to crowding and food shortage in this species were different. Adult migration propensity was not enhanced under such stress conditions during the larval phase.
Compositional decoupling of savanna canopy and understory tree communities in Serengeti
Authors: Anderson T. Michael , Morrison Thomas , Rugemalila Deusdedith , Holdo Ricardo
Published: November 2014

Questions

What is the pattern of compositional similarity for woody plants across the demographic bottleneck (i.e. canopy trees >2 m vs understorey trees <2 m) commonly observed in savannas? Does compositional similarity between woody plants in the canopy and understorey change across environmental gradients, and if so, which resource or disturbance factors explain the pattern? Finally, does disturbance history, i.e. whether individuals are newly established seedlings or top‐killed resprouts, help to explain the compositional similarity between canopy and understorey woody plants across sites?

Location

The Serengeti ecosystem, Tanzania, East Africa.

Methods

We compared the observed similarity to that expected from a simulated null model, and investigated the association between compositional similarity and soil bulk density, mean annual rainfall, fire return interval and elephant damage using a model selection approach. Moreover, we asked if disturbance history, i.e. whether individuals were newly established seedlings or top‐killed resprouts, helped explain compositional similarity between the canopy and understorey.

Results

The composition of canopy (>2 m) and understorey (<2 m) trees was surprisingly distinct: Acacia robusta (37.9%) and Acacia tortilis (23.7%) dominated the canopy, while Ormocarpum trichocarpum (43.0%) and Dichrostachys cinerea (19.6%) dominated the understorey. Compositional similarity between canopy and understorey woody plants generally decreased with soil bulk density, while for top‐killed individuals there was support for an increase in compositional similarity with fire return interval.

Conclusions

Our results suggest that the similarity between the canopy and recruitment communities is primarily associated with soil factors. Our results also suggest that long fire return intervals (i.e. infrequent fires) lead to increased similarity between the composition of the canopy and the recruitment pool, suggesting that disturbance promotes heterogeneity in the community across demographic bottlenecks. Despite the prominent role that megaherbivores and disturbance play in driving structural changes in savannas, our results suggest that previously unreported but pervasive species decoupling across demographic bottlenecks is primarily driven by resource availability or other bottom‐up constraints.
Genome‐wide scans of genetic variants for psychophysiological endophenotypes: A methodological overview
Authors: Iacono William. G. , Malone Stephen. M. , Vaidyanathan Uma , Vrieze Scott I.
Published: November 2014

This article provides an introductory overview of the investigative strategy employed to evaluate the genetic basis of 17 endophenotypes examined as part of a 20‐year data collection effort from the Minnesota Center for Twin and Family Research. Included are characterization of the study samples, descriptive statistics for key properties of the psychophysiological measures, and rationale behind the steps taken in the molecular genetic study design. The statistical approach included (a) biometric analysis of twin and family data, (b) heritability analysis using 527,829 single nucleotide polymorphisms (SNPs), (c) genome‐wide association analysis of these SNPs and 17,601 autosomal genes, (d) follow‐up analyses of candidate SNPs and genes hypothesized to have an association with each endophenotype, (e) rare variant analysis of nonsynonymous SNPs in the exome, and (f) whole genome sequencing association analysis using 27 million genetic variants. These methods were used in the accompanying empirical articles comprising this special issue, Genome‐Wide Scans of Genetic Variants for Psychophysiological Endophenotypes.
Heritability and molecular genetic basis of acoustic startle eye blink and affectively modulated startle response: A genome‐wide association study
Authors: Vaidyanathan Uma , Malone Stephen M. , Miller Michael B. , McGue Matt , Iacono William G.
Published: November 2014

Acoustic startle responses have been studied extensively in relation to individual differences and psychopathology. We examined three indices of the blink response in a picture‐viewing paradigm—overall startle magnitude across all picture types, and aversive and pleasant modulation scores—in 3,323 twins and parents. Biometric models and molecular genetic analyses showed that half the variance in overall startle was due to additive genetic effects. No single nucleotide polymorphism was genome‐wide significant, but GRIK3 produced a significant effect when examined as part of a candidate gene set. In contrast, emotion modulation scores showed little evidence of heritability in either biometric or molecular genetic analyses. However, in a genome‐wide scan, PARP14 produced a significant effect for aversive modulation. We conclude that, although overall startle retains potential as an endophenotype, emotion‐modulated startle does not.
Genomic substrates of neurophysiological endophenotypes: Where we've been and where we're going
Authors: Braff David L.
Published: November 2014

This special issue of Psychophysiology is focused on an imaginative and labor‐intensive examination of the genomic substrates of heritable neurophysiological endophenotypes in the Minnesota Center for Twin and Family Research (MCTFR) cohorts. The authors artfully combine the power of family‐based behavioral data with the atheoretical genome‐wide association study (GWAS) platform to enrich the examination of the genomic substrates of endophenotypes. Neurophysiological endophenotype deficits are found in psychiatric patients and are heritable in families of these psychiatric patients, allowing the investigators to combine the explanatory power of endophenotypes, with their known neural and functional substrates, with the otherwise agnostic identification of genes in the GWAS platform. This amplifies the power of the MCTFR endophenotype database. These well‐considered studies add significantly to our understanding of normal human neurobiology and stimulate the use of these endophenotypes to expand our knowledge of the role of these measures and their genomic substrates in normal and psychopathology research.
Activation of Ca2+‐activated Cl− channel ANO1 by localized Ca2+ signals
Authors: Jin Xin , Shah Sihab , Du Xiaona , Zhang Hailin , Gamper Nikita
Published: November 2014

Ca2+‐activated chloride channels (CaCCs) regulate numerous physiological processes including epithelial transport, smooth muscle contraction and sensory processing. Anoctamin‐1 (ANO1, TMEM16A) is a principal CaCC subunit in many cell types, yet our understanding of the mechanisms of ANO1 activation and regulation are only beginning to emerge. Ca2+ sensitivity of ANO1 is rather low and at negative membrane potentials the channel requires several micromoles of intracellular Ca2+ for activation. However, global Ca2+ levels in cells rarely reach such levels and, therefore, there must be mechanisms that focus intracellular Ca2+ transients towards the ANO1 channels. Recent findings indeed indicate that ANO1 channels often co‐localize with sources of intracellular Ca2+ signals. Interestingly, it appears that in many cell types ANO1 is particularly tightly coupled to the Ca2+ release sites of the intracellular Ca2+ stores. Such preferential coupling may represent a general mechanism of ANO1 activation in native tissues.
Experimental Modeling of Wind-Driven Bin-by-Bin Resuspension Factors of Freshly Fallen Radionuclides After an Energetic Release From a Radiological Dispersal Device
Authors: Perera Sharman , Waller Edward , Akhtar Ali
Published: November 2014

Small-scale experiments were carried out to characterize the resuspension factor of radioactive lanthanum oxide powder in an environmentally controlled wind tunnel, with the majority using particle sizes less than 10 μm in order to assess the impact of wind resuspension stresses and surface roughness conditions on resuspension. Operational principles of the measuring devices used in the radionuclide resuspension experiments and corresponding uncertainties are discussed. The average bin-by-bin particle resuspension factors (ki) for particle sizes, in the range of 0.25–7.00 μm and 7.00–12.5 μm for downwind fallout locations, were calculated and are reported here as 1.14×10−3 1/m and 4.39×10−2 1/m, respectively.
Dynamic Behavior of the AMB’s Vertical Arranged Rotor During Its Drop Process
Authors: Kang Xiao , Yang Guojun , Yu Suyuan
Published: November 2014

The active magnetic bearing (AMB) system is a crucial part in the helium circulator system of the 10MW high temperature gas-cooled reactor (HTR-10). Though the AMB has been widely used in industrial fields, it is still limited in the research of the dynamic behavior of AMB’s vertical arranged rotor with axial magnetic load during its drop process. This paper establishes the dynamic model of such drop process by Matlab. Meanwhile using the Hertz contact theory establishes the contact model of different configurations. Analyze the axial friction between the rotor and thrust interface of the inner ring of Auxiliary Bearing System (ABS). Besides, the numerical model is verified by the drop experiment with the axial magnetic force. Moreover, this paper analyzes the influence of the rotor’s drop rotational frequency and the axial bracing features including stiffness and damping on the dynamic behavior during vertical arranged rotor’s drop process. Moreover, the paper provides the optimal axial stiffness and damping for the ABS satisfying the experimental conditions so as to reduce the contact force. Such results provide important references to the design of the ABS with a vertical arranged rotor and its application in HTR-10 and High Temperature Reactor-Pebblebed Modules (HTR-PM).
Experimental Investigation Into Thermal Stratification by Direct Condensation in a Scaled Suppression Pool of Fukushima Daiichi Nuclear Power Plant
Authors: Jo Byeongnam , Takahashi Shinji , Song Daehun , Sagawa Wataru , Erkan Nejdet , Okamoto Koji
Published: November 2014

Experimental and numerical studies into thermal stratification by direct steam condensation in a torus type suppression pool were carried out to investigate the reactor core isolation cooling in the accidents of Fukushima Daiichi nuclear power plants. The suppression pool was manufactured to be a 1/22 scaled model of a Fukushima Daiichi nuclear power plant. Two different types of spargers were employed to simulate different units of the plants. In a sparger, 132 holes were uniformly drilled on the side of a pipe. However, the other sparger injected steam to the bottom. Flow rate was varied in a wide range to examine the effect on thermal stratification in the suppression pool. The experimental results showed that the sparger type influenced formation of thermal stratification. Moreover, steam flow rate strongly affected the onset time of thermal stratification, and the disappearance of the thermal stratification was affected by subcooling temperature. Computer simulation using a commercial software was conducted and the results show similar temperature profiles to the experimental results. Steam condensation was visualized in a vicinity of the spargers using high speed camera.
Investigation of ATHLET System Code for Supercritical Water Applications
Authors: Samuel J. , Lerchl G. , Harvel G. D. , Pioro I.
Published: November 2014

SuperCritical Water-cooled Reactors (SCWRs) are one of six Generation-IV nuclear-reactor concepts. They are expected to have high thermal efficiencies within the range of 45–50% owing to the reactor’s high pressures and outlet temperatures. Efforts have been made to study the supercritical phenomena both analytically and experimentally. However, codes that have been used to study the phenomena analytically have not been validated for supercritical water.

The thermal-hydraulic computer code ATHLET (Analysis of THermal-hydraulics of LEaks and Transients) is used for analysis of anticipated and abnormal plant transients, including safety analysis of Light Water Reactors (LWRs) and Russian Graphite-Moderated High Power Channel-type Reactors (RBMKs). The range of applicability of ATHLET has been extended to supercritical water by updating the fluid- and transport-properties packages, thus enabling a transition from subcritical to supercritical fluid states. This extension needs to be validated using experimental data.

In this work, the applicability of ATHLET code to predict supercritical-water behaviour in various heat-transfer conditions is assessed. Several well-known heat-transfer correlations for supercritical fluids are added to the code and applied for the first time in ATHLET simulations of experiments. A numerical model in ATHLET is created to represent an experimental test section and results for the heat transfer coefficient, bulk fluid temperature, and the tube inside-wall temperature are compared with the experimental data.

The results from the ATHLET simulations are promising in the Normal and Enhanced Heat-Transfer Regimes. However, important phenomena such as Deteriorated Heat Transfer are currently not accurately predicted. While ATHLET can be used to develop preliminary design solutions for SCWRs, a significant effort in analysis of experimental work is required to make further advancements in the use of ATHLET for SCW applications.
Assessment of the Effects of Anisotropy in TRIGA Based on 3D-AGENT Methodology
Authors: Hernandez Hermilo , Jevremovic Tatjana
Published: November 2014

The neutronics characterization of The University of Utah TRIGA reactor core focused at evaluating the effects of anisotropic neutron scattering is based on 3D AGENT methodology. The AGENT methodology is based on method of characteristics with exact modeling of geometry and material distribution in the reactor cores. This feature is unique to deterministic codes worldwide and is based on the originally developed R-function solid modeler. The anisotropic correction to neutron transport in 3D hexagonal and square reactors as implemented in AGENT, provides highly accurate solution with no limitations to core configuration or the degree of anisotropic scattering terms. In testing this new methodology on TRIGA type reactors, we conclude that the AGENT deterministic solution with P2 anisotropic scattering approximation provides fully comparable solution to the MCNP5 but with 93% CPU-time reduction.
Experimental Study on Transient Heat Transfer Enhancement for Helium Gas Flowing Over a Thin Twisted Plate
Authors: Zhao Zhou , Liu Qiusheng , Fukuda Katsuya
Published: November 2014

Transient forced convection heat transfer due to exponentially increasing heat input to a heater is important as a database for safety assessment of the transient heat transfer process in a Very High Temperature Reactor (VHTR). The knowledge of heat transfer enhancement using a heater with twisted configuration is also important for the high performance design of intermediate heater exchanger (IHX) in VHTR system. In this study, forced convection transient heat transfer for helium gas at various periods of exponential increase of heat input to a short thin twisted plate with various helix angles was experimentally studied. A forced convection heat transfer experimental apparatus was used to measure the experimental data. The test heater was mounted horizontally along the center part of a circular test channel. Twisted plates were made of thin platinum plate with a thickness of 0.1 mm and width of 2 mm and 4 mm. The heat generation rates of the heater were controlled and measured by a heat input control system. The heat generation rate, Q̇, was raised with exponential function, Q̇ = Q0exp(t/τ). Where, t is time, and τ is period of heat generation rate. The mean temperature of the test heater was measured by resistance thermometry. The heat flux was obtained by the energy conservation equation. The test heater surface temperature was calculated from heat conduction equation of the heater. The transient heat transfer experimental data were measured for the periods ranged from 80 ms to 17 s and at a gas temperature of 303 K under 500 kPa. The flow velocities ranged from 4 m/s to 10 m/s. In the experiments, the twisted plates with different width were tested. The surface temperature and heat flux are increasing exponentially with the time. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period longer than about 1 s, and it becomes higher for the period shorter than about 1 s. The heat transfer coefficients for total length of the twisted plate were compared with the values of flat plate which has the same width and thickness with the twisted one. The local mean heat transfer coefficients have been tested as well. The heat transfer coefficients of twisted plate are about 10% for 2 mm-width one and15% for 4 mm-width one higher than those of flat plate with same width at the quasi-steady state. And also, the heat transfer coefficients for the first half pitch are 24% higher than that for the total length of the same twisted plate. Therefore, an enhancement in the heat transfer coefficient for the twisted plate was clarified.
Comparison of ASME Code NB-3200 and NB-3600-Based Environmental Fatigue Calculations for Piping Components
Authors: Yang Kyeongjin , Kim Daesu , Lee Dongjae , Lee Joonho , Lee Sangbae , Kim Inyeung
Published: November 2014

Environmentally-assisted fatigue evaluations are to be conducted for ASME Code Class 1 piping components in a pressurized water reactor. Environmental fatigue correction factor method for incorporating the effects of light water reactor coolant environments into ASME Section III fatigue evaluations was investigated in this paper. Both ASME Code NB-3200 and NB-3600 methods were used to determine the usage factors of the piping components. Considered in these calculations were the loads which are generally applied to the piping design for the nuclear power plants such as seismic, thermal expansions, thermal transients, thermal stratifications and building-filtered dynamic loadings. For the practical applications of NB-3600 method, regarded as the simple and conservative approach, to the piping components, it was presumed that the stress intensity and/or strain time histories for all or some of the external loadings were not known; therefore the time consistency might not be considered in calculating the usage factors as well as environmental correction factors (Fen). In NB-3200 method in contrast to NB-3600, the stress variations with time for all loads except for the dynamic loads were obtained for the fatigue evaluations in LWR environments, and therefore the time consistency was considered. The results showed that the environmental correction factors as well as in-air cumulative usage factors calculated from NB-3200 methods were significantly less than those from NB-3600 rules. In addition, comparing the results of conventional ASME fatigue evaluation applied until 2006 to the ones in accordance with USNRC RG 1.207 issued on 2007, one may identify that the cumulative usage factors in LWR environments were larger than the conventional one due to the change of design fatigue curves as well as Fen factors accounting for the environmental effects on fatigue. Although this work was focused on the detailed calculations of the usage factors and Fen values, one might identify or suggest a number of areas requiring further clarification or research through the efforts of this study, which were not yet addressed. A few items needed to be clarified, especially for NB-3600-based fatigue evaluations, are also discussed in this paper.
Two-Phase Natural Circulation Cooling Performance Assessment and Safety Analysis for APR1400 Core Catcher System
Authors: Song Ki Won , Revankar Shripad T. , Park Hyun Sun , Rhee Bo , Ha Kwang Soon , Park Rae Joon , Song Jin Ho
Published: November 2014

The two-phase natural circulation cooling performance of the APR1400 core catcher system is studied utilizing a drift flux flow model developed via scaling analysis and with an air-water experimental facility. Scaling analysis was carried out to identify key parameters, so that model facility could simulates two-phase natural circulation. In the experimental apparatus, instead of steam, air is injected into the top wall of the test channel to simulate bubble formation and void distribution due to boiling water in the core catcher channel. Measurement of void fraction critical to the heat transfer between the wall and coolant is carried out at certain key position using double-sensor conductivity probes. Results from the model provide expected natural circulation flow rate in the cooling channel of the core catcher system. The observed flow regimes and the data on void fraction are presented. For a given design of the down comer piping entrance condition bubble entrainment was observed that significantly reduced the natural circulation flow rate.
Analysis of a Concept for the Diagnosis of the Core State During Severe Accidents in Pressurized Water Reactors
Authors: Schmidt Sebastian , Fiß Daniel , Kratzsch Alexander
Published: November 2014

In line with the cooperative project “Non-invasive Condition Monitoring of Nuclear Reactors for the Detection of Level Change and Deformation of the Core” between the Technical University Dresden and the Institute of Process Technology, Process Automation and Measuring Technology (IPM) of Zittau/Goerlitz University of Applied Sciences, a measuring system for the core state diagnosis during a core melt accident in the reactor pressure vessel of a pressurized water reactor is going to be developed. The operational principle of this system is based on the non-invasive measurement of continuously changing gamma radiations (caused by the shifting of melted materials and fission products) outside of the reactor pressure vessel by means of several gamma radiation sensors. The sensors are arranged over the height of the core and the lower head. By using computer based and real-time capable methods for evaluation of the measured gamma radiations conclusions about the core state can subsequently be drawn. This paper includes a description of a concept as well as several methods for the core state diagnosis during a core melt accident. The main part is the analysis of the methods for the core state diagnosis based on different evaluation criteria.
Numerical Simulation of Steam Generator Tube Rupture Sequence in ADS Reactor
Authors: Yang Xu , Zhou Tao , Lin Daping , Fang Xiaolu , Chen Baixu , Ru Xiaolong
Published: November 2014

In ADS reactor which choose LBE (Lead-Bismuth Eutectic) as coolant and spallation target. While SGTR (Steam Generator Tube Rupture) accident occur, water in secondary side will inject to LBE in primary coolant, and flow with LBE. The code of FLUENT will be used, steam is looked as particle, and standard k-ε model is used to predict turbulence variation of continuous phase in core. The DPM (Discrete Phase Model) will be used to track the trajectory of the particles. The distribution of steam in core will be obtained, which will verify the safety of reactor. The results show that the steam flowing across the core with LBE, might accumulate in some position and cause a surge of power. At the same time, the aggregation of steam at the channel might lead to a steam plug, and hinder the flow of the coolant in core, then core overheating might occur. Last but not least, local accumulation of water vapor may accelerate the corrosion of stainless steel material in core.
Study on Turbulent Buffeting Characteristics of Liquid Lead Bismuth
Authors: Li Yun-Bo , Zhou Tao , Huo Qi-Jun , Chen Bai-Xu
Published: November 2014

In Pb Bi loop, the turbulent buffeting phenomenon of lead bismuth fluid in heat exchanger, may cause fatigue damage of heat transfer tube. Through the establishment of Pb-Bi loop heat exchanger model, invent a program for calculation, we can get the turbulent buffeting characteristics. The results show that: As the increases of heat exchange tube cross number, the buffeting coefficients pipeline is greater, the probability of occurrence of turbulent buffeting phenomenon is more low; The greater lead bismuth flow velocity is, the more prone to turbulent buffeting phenomenon. With vertical heat tube center distance increases, the buffeting coefficients decreased first and then increased, when the buffeting coefficients reached the minimum value, the turbulent buffeting phenomenon is most intense; As the horizontal heat pipe center distance is bigger, turbulent buffeting phenomenon is becoming less clear.
Thermal Hydraulic Studies of a Fluoride Salt Cooled High Temperature Test Reactor With Different CFD Methods
Authors: Wang Chenglong , Xiao Yao , Zhou Jianjun , Zhang Dalin , Qiu Suizheng , Tian Wenxi , Su Guanghui
Published: November 2014

The Fluoride-salt-cooled High temperature Reactor (FHR) is new reactor concept-about a decade old which is mainly on going in China and U.S. The preliminary thermal-hydraulic studies of the Fluoride salt cooled High temperature Test Reactor (FHTR) is necessary for the development of the FHR technology. In this paper, the thermal-hydraulics of FHTR (also called TMSR-SF) designed by Shanghai Instituted of Applied Physics (SINAP) is studied in different power modes. The temperature distributions of the coolant and the fuel pebble are obtained using a steady-state thermal-hydraulic analysis code for FHR. The comprehensive local flow and heat transfer are investigated by computational fluid dynamics (CFD) for the locations where may have the maximum pebble temperature based on the results from single channel analysis. The profiles of temperature, velocity, pressure and Nu of the coolant on the surface of the pebble as well as the temperature distribution of a fuel pebble are obtained and analyzed. Numerical results showed that the results of 3-D simulation are in reasonable agreement with that of single channel model and also illustrated safety operation of the preliminary designed TMSR-SF in different power mode.
I&C Integrated Test Phase of the Mochovce Nuclear Power Plant, Units 3 and 4
Authors: Ciriello Antonio , Kümmerling Stefan
Published: November 2014

This paper briefly introduces the safety instrumentation and control (I&C) system (Teleperm® XS) designed for the nuclear power plant in Mochovce units 3 and 4 (Slovak Republic). The overall I&C architecture of the concerned nuclear power plant is shortly introduced as well. An overview is given on the different test phases for the hardware and software I&C modules. The integrated I&C test concept and its implementation is presented as well as the description of the integrated test phase in the test bay in Erlangen (Germany). After a successful completion of the integrated test phase for unit 3, the Factory Acceptance Test (FAT) and the erection phase have been started for the concerned I&C safety systems (e.g., the Reactor Protection System and the Reactor Power Limitation System). This paper will also present the significant advantages and specifics of performing the concerned I&C tests in the aforementioned test bay.
Design of 1/4 Scale Performance Test Facility for the PMR200 RCCS
Authors: Bae Y. Y. , Cho B. H. , Kim J. H. , Kim M. H. , Kim Y. W.
Published: November 2014

One of the key technologies for the development of the PMR200, a VHTR demonstration plant, is a verification of the reactor cavity cooling system (RCCS) performance, which ensures reactor safety by passively removing heat from the reactor cavity. A preliminary numerical analysis of the RCCS showed that the maximum temperature in RCCS reached up to 700°C. Since radiation dominates the heat transfer at such a high temperature, it should be considered in both the design and associated numerical works for the test facility. For a verification of the RCCS performance, a 1/4 scale test facility has been constructed, and a performance test is being carried out. As the first step for the design of the test facility, a scaling analysis has been performed; and the ratio of variables between the model and prototype were determined. Numerical calculations using a CFD code were also performed to support the scaling analysis. It was confirmed that the scaling analysis was reasonably correct.
The Design of Experiment Equipment for Liquid Lithium Water Interaction
Authors: You Ximing , Tong Lili , Cao Xuewu
Published: November 2014

In order to assess the risk of using liquid lithium as plasma facing materials, the experiment equipment for liquid lithium water interaction was introduced in detail. The design temperature of liquid lithium and water were 200 °C to 600 °C and 25 °C to 90 °C, respectively. A furnace was designed to heat solid lithium to molten state in inert gases. The lithium droplets were released into the test section by adjusting the sample release rod made of stainless steel. The shape of lithium droplet and steam generated around the lithium could be observed by the high speed camera. The change of pressure and temperature would be recorded through transducers at the same time. The physical model of liquid lithium water interaction was analyzed, which contained a heat transfer model and a mass transfer model. In addition, an experiment of the solid lithium granule water interaction was performed to debug the devices and make a preliminary assessment of the risk for solid lithium water interaction.
Validation of a New PURC Module for Calculating Probability Table in Unresolved Resonance Region in RXSP Code
Authors: Yu Jiankai , Huo Honglei , Li Wanlin , Yu Ganglin , Wang Kan
Published: November 2014

Taking into consideration the unresolved resonance self-shielding effect, probability table is one of the most important and natural methods used to simulate the neutron transport in unresolved resonance range in reactor physics. A module named PURC for probabilistic unresolved resonance calculation which is embedded in the RXSP Beta2.0 code, has been developed by REAL team in Department of Engineering Physics in Tsinghua University. It is the optimization in sort algorithm that make PURC module more efficient. After applying the OpenMP parallel algorithm into this module, it has improved computational efficiency by more than one order of magnitude comparing with the corresponding functional module named PURR in NJOY code. Meanwhile the computational accuracy of PURC module is validated and verified by series of microscopic cross section comparisons and macroscopic criticality benchmarks.
Simulation of Molten Corium Concrete Interaction With the MOCO Code
Authors: Lin Bo , Qiu Sui-zheng , Su Guang-hui , Tian Wen-xi , Zhang Ya-pei
Published: November 2014

In the event of a severe accident in a pressurized water reactor, the core of a reactor melts and forms corium, a mixture that includes molten UO2 and ZrO2. If the reactor pressure vessel fails, corium can be relocated in the containment cavity and interact with concrete forming a melt pool. The melt pool can be flooded with water at the top for quenching it. However, the question is what extent the water can ingress in the corium melt pool to cool and quench it. To reveal that, a numerical study has been carried out using a new computer code MOCO. The code considers the heat transfer behavior in axial and radial directions from the molten pool to the overlaying water, crust generation and growth, and incorporates phenomenology that is deemed to be important for analyzing debris cooling behavior. The interaction between thermalhydraulics and physic-chemistry is modeled in MOCO. The main purpose of this paper is to present the modeling used in MOCO and some validation calculations using the data of experiments available in the literature.
Experimental Validation of PRHR System for Low Temperature and Low Pressure Pool-Type LWR Using Thermosyphon
Authors: Moon Jangsik , You Byung-Hyun , Jung Yong Hun , Jeong Yong Hoon
Published: November 2014

PRHR system for low temperature and low pressure pool-type LWR, AHR400 is designed by two-phase closed thermosyphon and experimental validation is conducted. AHR400 is dedicated only to heat generation used in seawater desalination and operation temperature and pressure. LBLOCA is not considered as DBA due to no pipeline in primary system. There are LOHS and SBO for DBAs and PRHR system reduces damage during DBAs. Design of the PRHR system follows Direct Reactor Auxiliary Cooling System (DRACS) type. Two-phase closed thermosyphon, which uses phase change of working fluid, is applied to the PRHR system and the heat transfer in thermosyphon are analyzed by thermal resistance calculation model. Experimental thermosyphon that has similar thermal condition with the thermosyphon in designed PRHR system was explored for validation. The results show that the evaporation model overestimates heat transfer rate on the evaporator region.
MAAP5 Simulation of the PWR Severe Accident Induced by Pressurizer Safety Valve Stuck-Open Accident
Authors: Li Longze , Zhang Yapei , Tian Wenxi , Su Guanghui , Qiu Suizheng
Published: November 2014

The Modular Accident Analysis Program version 5 (MAAP5) is a computer code that can simulate the response of light water reactor power plants during severe accident sequences. The present work aims to simulate the severe accident of a typical Chinese pressure water reactor (PWR) induced by the he pressurizer safety valve stuck-open accident with MAAP5. Three cases corresponding to 1, 2 and 3 pressurizer safety valves stuck open accidents without high pressure injection (HPI) and the auxiliary feed water (AFW) of steam generator (SG) were analyzed. The results showed that the pressure safety valve stuck open with HPI and AFW failure accident would lead to a severe accident. And the severe accident sequence was correlated with the number of the stuck open valve. In the case of 1 valve stuck open, the coolant lost slowly and the primary system depressurized slowly which delayed the activation of the low pressure injection (LPI). The reactor pressure vessel (RPV) failed at this case. On the contrary, in the case of 2 and 3 valves stuck open, the coolant lost faster and the pressure decreased rapidly to the critical pressure of the LPI. Thus, the consequences of the two cases were much slighter. The results are meaningful and significant for comprehending the detailed process of PWR severe accident, which is the basic standard for establishing the severe accident management guidelines.
Flow Characteristics in an Open Two-Phase Natural Circulation Loop
Authors: Hou Xiaofan , Sun Zhongning , Fan Guangming , Tang Jiguo , Su Jiqiang
Published: November 2014

The flow characteristics of an open single-tube (Φ38×2000 mm), two-phase natural circulation (TPNC) loop was investigated, under the condition of constant saturated temperature at the atmosphere (99±0.5°C) at the inlet of heating tube. Five typical circulation modes are observed in the range of experiment heating power (from 2.8 kW to 34.8kW), namely intermittent flashing oscillation, geysering and flashing induced oscillation, flashing boiling eruption and flashing induced oscillation, sustained flashing and steady two-phase flow. It was shown that flashing and geysering or boiling eruption are predominant factors influencing flow characteristics. Moreover, a calculation model is developed to investigate the static flow characteristics of the TPNC system. The calculation results show a good agreement with the experiments. In addition, the calculation results show that the static flow excursion phenomenon may occurs in the open TPNC system, under the higher heating powers.
RELAP5 Code Analysis of LSTF Small Break LOCA Tests With Steam Generator Intentional Depressurization as an Accident Management Procedure: Investigation on Base Case Result Appropriate for the Best Estimate Plus Uncertainty (BEPU) Application
Authors: Kinoshita Ikuo , Torige Toshihide , Murase Michio , Yoshida Yoshitaka , Takeda Takeshi , Satou Akira , Nakamura Hideo
Published: November 2014

The application of the Best Estimate Plus Uncertainty (BEPU) method is made to analysis of the “Intentional depressurization of steam generator secondary side” which is an accident management procedure in a small-break loss-of-coolant accident (SBLOCA) with high pressure injection (HPI) system failure. RELAP5/MOD3.2 is used as the analysis code. By applying the BEPU method, the uncertainties of the analysis results can be estimated quantitatively. However, the accuracy of the analysis results depends primarily on the base case result predicted by the best estimate code. In this study, in order to investigate the appropriate base case model, simulation analyses using the RELAP5/MOD3.2 were carried out for the ROSA Large Scale Test Facility (ROSA/LSTF) secondary-side depressurization tests. It was found that the code predicted well the major event progressions such as pressure responses, core liquid level responses, and rod surface temperatures, as well as important phenomena such as formation and clearing of loop seals, accumulation of water from condensation, and countercurrent flow limitation (CCFL) at the inlet of the U-tubes, which are characteristic features of this accident scenario.
Assessment Oxidation Kinetics and Products in SCWR Media of Austenitic ODS Steels With Different Austenite Stabilisers
Authors: Mihalache Maria , Mihalache Mihail , Dumitrescu Iulia , Zhou Zhangjian
Published: November 2014

In order to fulfil requirements for corrosion resistance for new reactor GIV, the austenitic 304L stainless steel and 18Cr-20Mn austenitic steel were improved by oxide dispersion strengthening (ODS), using two nano-oxide types: titanium and yttrium oxides.

Two new ODS steels and a reference material, A/SA-270 grade 304L SS as plate, were characterised by different techniques and its behaviour in SCWR environment was considered. Coolant compatibility studies have been performed in demineralised water at supercritical conditions: temperature of about 550°C and 25 MPa pressure. The oxide developed on the 304ODS samples is layered, thicker and more uniform than on 304L SS. Some oxides grown on 18Cr-20MnODS steel are un-adherently and they are lost in the simulated water coolant.

The weight gains of ODS samples are positive and higher than 304L SS up to approximately 1320 hours while on 18Cr-20MnODS steel is negative. The oxide films were investigated by SEM and EDS techniques.