bluuebunny/crossref_metadata_2025 huggingface dataset:
Residency Duration and Shelter Quality Influence Vibratory Signalling Displays in A Territorial Caterpillar
Authors: Yack Jayne E. , Gill Sharleen , Drummond‐Main Chris , Sherratt Thomas N.
Published: February 2014

Residents are more likely to win territorial disputes than intruders. One explanation for this prior resident advantage is that residents place a higher value on the resource and are therefore more motivated to win. Although value asymmetry models of animal contests often assume that contestants use information about resource value, information on the proximate cues affecting territorial behaviour is often lacking. We use a simple model system – territorial behaviour in the masked birch caterpillar (Drepana arcuata) to identify factors that affect territorial behaviour. Late instar caterpillars occupy solitary silken leaf shelters, which they defend against wandering conspecifics with a vibratory display. We evaluated how a caterpillar identifies itself as the owner and the factors that influence a resident's motivation to signal. To do so, we conducted three experiments between size‐matched residents and intruders to assess how residency duration and shelter quality independently affected territorial displays during the early stages of a contest. Experiment 1 (Time Exp.) demonstrated that resident signalling rates increase with increased duration on the leaf prior to introducing the intruder. Residents also signal more than intruders after residency periods of 1–3 min and longer, demonstrating that residents gather information about resource value shortly after occupying a leaf. Experiment 2 (Squatter Exp.) aimed to disentangle the effects of time on the leaf and silk accumulation. Squatters (individuals in a shelter made by another) placed for 1–3 min on a leaf containing a full silk shelter signalled more to intruders than did caterpillars placed on a fresh leaf for 1–3 min. Experiment 3 (Shelter Removal Exp.) showed that residents whose shelters had been removed signal less than those occupying an intact shelter, despite an equal length of time investing in them. Our experiment is the first to covary both prior residency duration and territory quality, and we find that the motivation of caterpillars to signal is a function of both of these attributes.
Thermal fatigue resistance characterization and ranking of materials using the V‐shape specimen testing method
Authors: Wei Z. , Konson D. , Yang F. , Luo L. , Lin B. , Ellinghaus K. , Pieszkalla M.
Published: February 2014

Thermal fatigue resistance of materials is an extremely important criterion for the long‐term durability and reliability performance of very high‐temperature components and systems, such as advanced auto engine and exhaust systems. There is a broad range of material choices for thermal fatigue resistance applications. The final selection of the materials depends on the balance of engineering performance of the materials and the cost. To optimize the thermal fatigue resistance and cost of those materials, a reliable testing procedure for material thermal fatigue characterization and a material evaluation/selection matrix must be established.

In this paper, the V‐shape specimen testing method in evaluating thermal fatigue resistance performance is introduced first. The influence of several factors, such as the thickness of specimens, operating temperature and hold time, on the thermal fatigue resistance is experimentally investigated. Subsequently, the statistical and probabilistic characteristics of the thermal fatigue failure data are analysed to reveal the possible failure mechanisms. Finally, a general rational approach for thermal fatigue resistance characterization and ranking is demonstrated, and a simple parameter λ = kσf/Eα, which combines the material strength, thermal conductivity and thermal expansion, is found to be the new breakthrough parameter, correlating to V‐shape thermal fatigue test results. Results on four currently used stainless steels verify the correlations and indicate the validity of this approach.
Rome III Criteria Cannot Distinguish Patients with Chronic Gastritis from Those Functional Dyspepsia Patients
Authors: Wei Zhu , Ying Liu , Wen Guo , Mengnan Zhang , Yali Zhang
Published: February 2014

Background

Functional dyspepsia is thought to be a diagnosis made after excluding endoscopically detectable lesions by the current Rome III criteria. However, whether these “functional dyspepsia” patients were diagnosed appropriately is still controversial.

Materials and Methods

A total of 223 patients diagnosed with functional dyspepsia by Rome III criteria were enrolled. All patients were submitted to endoscopic examination, rapid urease test, and histologic evaluation. We also appraised the effect of a 7‐day treatment based on the Glasgow Dyspepsia Severity Score.

Results

Helicobacter pylori infection and neutrophil infiltration were found in 37.7% and 36.3% cases, respectively, and were both more frequent in the subgroup with epigastric pain symptom (EPS) than in the other two subgroups. In addition, neutrophil infiltration was more common and severe in the H. pylori‐positive individuals than in the patients without infection (Mann–Whitney U‐test = 431.500, p < .001). The treatment was useful in symptom improvement of all three subgroups, and the EPS subgroup had the greatest change of symptom scores before and after treatment as compared with the subgroup with postprandial distress symptom (PDS) and PDS/EPS subgroup (χ2 = 42.745, p < .001), and the eradication of H. pylori revealed a statistical significant difference in different subgroups (χ2 = 11.300, p = .001).

Conclusions

Our findings showed that many H. pylori‐positive subjects diagnosed as “functional dyspepsia” were actually chronic gastritis patients, especially the EPS cases who are more likely to be patients with “active gastritis under microscope,” and also benefit most from the treatment of proton‐pump inhibitors or eradication of H. pylori.
Synthesis of Volcano‐Like CdS/Organic Nanocomposite
Authors: Davar Fatemeh , Loghman‐Estarki Mohammad Reza , Salavati‐Niasari Masoud , Ashiri Rouholah
Published: February 2014

Cadmium sulfide/organic nanocomposites, which were based on long nanowires, were synthesized by a simple reaction between cadmium nitrate and thioglycolic acid (TGA) at room temperature. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected‐area electron diffraction (SAED), Fourier transform infrared (FTIR) spectra, and thermogravimetric analysis (TG). The CdS/organic nanocomposites was decomposed into pure wurtzite CdS nanorods through hydrothermal treatment at 190°C. Photoluminescence (PL) spectra were used to study the optical properties of CdS/organic composite and pure CdS. It is found that the emission maximum of the CdS/TGA nanocomposite is significantly blue‐shifted, and the intensity is highly enhanced as compared to the luminescence spectrum of the bare CdS nanorods.
Porous Bulk Specimens in CaO‐MgO‐SiO2 Systems Using Steel Slag and Altered Additives by Conventional Sintering
Authors: Faeghinia Aida
Published: February 2014

To obtain the porous, bulk, brick like samples the following mixtures were pressed and sintered at different temperatures: steel slag, sintering aids (soda lime glass, sodium phosphate), and common foaming additives (like dolomite, perlite). The bulk densities of final composites were from 1.3 to 2.41 g/cm3, and open porosities were from 15 to 40 vol%. The bending strengths of composites varied from 5.5 to 15.9 MPa. The final phase of sintered samples was forming of calcium magnesium silicate. The samples which had 80 wt% slag–5 wt% SiC–5 wt% perlite–5 wt% boric acid–5 wt% sodium phosphate showed the 40 vol% porosity and 6.7 ± 0.2 MPa bending strength.
The evaluation of three diagnostic tests for the detection of equine influenza nucleoprotein in nasal swabs
Authors: Galvin Pamela , Gildea Sarah , Nelly Maura , Quinlivan Michelle , Arkins Sean , Walsh Cathal , Cullinane Ann
Published: February 2014

Background

Equine influenza (EI) is a highly contagious respiratory disease of horses.

Objectives

The aim of this study was to evaluate two rapid antigen detection kits (Directigen or DFA, and Espline) and a commercial ELISA for the detection of EI nucleoprotein in nasal swabs.

Method

Nasal swab samples from naturally and experimentally infected horses were used to compare the sensitivity and specificity of these assays to virus isolation (VI) and real‐time RT‐PCR.

Results

If real‐time RT‐PCR was considered as the gold standard, the sensitivity of the other tests in field samples was 68% (DFA), 35% (ELISA), 29% (Espline), and 9% (VI). These tests had 100% specificity when compared to real‐time RT‐PCR. A receiver operating characteristic (ROC) curve indicated that decreasing the cutoff of the ELISA would increase sensitivity with some loss of specificity. In samples from experimentally infected horses, the sensitivity of the tests compared with real‐time RT‐PCR was 69% (VI), 27% (DFA), 6% (Espline), and 2% (ELISA). The specificity was 100% for Espline and ELISA and 95% for VI and DFA.

Conclusions

This study illustrated that DFA is the most sensitive antigen detection test evaluated for the diagnosis of EI and that it can detect virus in some subclinical infected and vaccinated horses. The results suggest that DFA is a useful adjunct to laboratory tests and may be effective as a screening test in a quarantine station or similar facility where horses are monitored daily.
THE ECONOMICS OF COUNTERTERRORISM: A SURVEY
Authors: Schneider Friedrich , Brück Tilman , Meierrieks Daniel
Published: February 2014

We provide a review of theoretical and empirical contributions on the economic analysis of terrorism and counterterrorism. We argue that simple rational‐choice models of terrorist behavior – in the form of cost‐benefit models – already provide a well‐founded theoretical framework for the study of terrorism and counterterrorism. We also hint at their limitations which relate to the failure of accounting for the dynamics between terrorism and counterterrorism that may produce unintended second‐order effects as well as for the costs associated with counterterrorism and its international dimension. We reevaluate previously proposed counterterrorism strategies accordingly. Finally, in the light of our findings, we discuss interesting areas of future research.
Transitions from grassland to savanna under drought through passive facilitation by grasses
Authors: de Dios Víctor Resco , Weltzin Jake F. , Sun Wei , Huxman Travis E. , Williams David G.
Published: February 2014

Questions

Woody plant encroachment into former grasslands currently represents a major physiognomic shift globally. Seedling establishment is a critical demographic bottleneck and is considered to be alleviated by increases in water availability and negatively impacted by interactions with grasses, particularly when water stress increases. However, interactions with grasses that are not actively competing for resources (‘passive interactions’ when grasses are dead) has seldom been considered. Could the transition from a live to a dead grass (litter) canopy favour recruitment of woody seedlings in a semi‐arid grassland of the American SW? How does the sign and intensity of grass–seedling interactions change across drastically different summer precipitation regimes with and without passive interactions?

Location

Sonoran Desert shrub savanna at the Santa Rita Experimental Range, near Tucson, AZ, US.

Methods

Four cohorts of Prosopis velutina seeds were planted annually (2002–2005) under rainout shelters that intercepted all incoming precipitation on a soil with sandy loam texture. Summer precipitation was manipulated to simulate either a 50% increase or decrease in the long‐term mean, and cover was manipulated to simulate a grassland dominated by the C4 bunchgrass Heteropogon contortus or left unvegetated. Emergence and survival of P. velutina was monitored and compared across cover types, along with monitoring of soil water content and light interception.

Results

Strong active competition was observed with live grasses, under both summer drought and also under ample summer water supply. However, the pattern was reversed and strong passive facilitation of P. velutina was observed over time when grass canopies died and remained in place. This passive facilitation under dry summers was so strong that recruitment under dead grass conditions was comparable to that observed when ample water supply removed the effects of competition on unvegetated plots.

Conclusions

After significant mortality of standing grass canopies, which typically compete for limited soil moisture resources, rates of recruitment by shrubs may increase even with significant seasonal drought. This work extends our understanding of interactions among co‐located organisms and their effects on plant community dynamics, and introduces a new hypothesis on how grass litter facilitates woody plant encroachment during seasonal droughts.
The gastric accommodation response to meal intake determines the occurrence of transient lower esophageal sphincter relaxations and reflux events in patients with gastro‐esophageal reflux disease
Authors: Pauwels A. , Altan E. , Tack J.
Published: February 2014

Background

Gastro‐esophageal reflux (GER), the retrograde flow of gastric contents into the esophagus is a physiologic phenomenon, which can evoke symptoms and/or lesions in the esophagus (=gastro‐esophageal reflux disease or GERD). Proton pump inhibitors (PPIs) reduce gastric acidity; however, as they are unable to control transient lower esophageal sphincter relaxations (TLESRs), the main mechanism for reflux in GERD, they do not abolish reflux. TLESRs occur predominantly in the postprandial period, and they are believed to be triggered by gastric distention. Gastric accommodation (GA) is the physiologic response to gastric distention and serves to prevent a rise in gastric wall tension during food intake. We aimed to study the relationship between GA and TLESRs, as they both are triggered by gastric distention.

Methods

We studied 12 GERD patients (average age 37 years [range 18–62], 7m/5f) and nine healthy volunteers (average age 27 years [range 22–36], 2m/7f) using high resolution manometry‐impedance measurement before and after a mixed meal challenge. We determined the number of TLESRs (with or without reflux) and measured pre‐ and postprandial IGP. The change in IGP between the pre‐ and postprandial period (ΔIGP) is used as surrogate for GA. We also measured LES pressure before and after the meal and calculated the change (ΔLESp).

Key Results

There were no statistical differences between pre‐ and postprandial IGP in GERD and healthy volunteers and similarly, there was no significant difference between pre‐ and postprandial LES pressures in GERD patients and healthy volunteers. The number of TLESRs (with or without reflux) was similar in GERD and healthy volunteers. More importantly, we did observe a negative correlation between ΔIGP and the number of TLESRs, irrespective of whether they were associated with reflux or not, in the GERD patients (without reflux r = −0.67, p = 0.017; with reflux r = −0.81, p = 0.0014). The same observations were found in healthy volunteers, where ΔIGP and the number of TLESRs are significantly inversely correlated (without reflux r = −0.87, p = 0.0045; with reflux r = −0.75, p = 0.021). We could not establish a correlation between ΔLESp and the number of TLESRs, neither in GERD patients nor in healthy volunteers.

Conclusions & Inferences

This is the first study showing a clear negative correlation between ΔIGP and the number of TLESRs, irrespective of whether they were associated with reflux or not, both in GERD patients and in healthy subjects. These results suggest that TLESRs and GA are closely linked, probably through activation of mechanoreceptors involved in triggering of TLESRs.
Functional characterization of the chloroplast ferric chelate oxidoreductase enzyme
Authors: Solti Ádám , Müller Brigitta , Czech Viktória , Sárvári Éva , Fodor Ferenc
Published: February 2014

Iron (Fe) has an essential role in the biosynthesis of chlorophylls and redox cofactors, and thus chloroplast iron uptake is a process of special importance. The chloroplast ferric chelate oxidoreductase (cFRO) has a crucial role in this process but it is poorly characterized.

To study the localization and mechanism of action of cFRO, sugar beet (Beta vulgaris cv Orbis) chloroplast envelope fractions were isolated by gradient ultracentrifugation, and their purity was tested by western blotting against different marker proteins. The ferric chelate reductase (FCR) activity of envelope fractions was studied in the presence of NAD(P)H (reductants) and FAD coenzymes. Reduction of Fe(III)‐ethylenediaminetetraacetic acid was monitored spectrophotometrically by the Fe(II)‐bathophenanthroline disulfonate complex formation.

FCR activity, that is production of free Fe(II) for Fe uptake, showed biphasic saturation kinetics, and was clearly associated only to chloroplast inner envelope (cIE) vesicles. The reaction rate was > 2.5 times higher with NADPH than with NADH, which indicates the natural coenzyme preference of cFRO activity and its dependence on photosynthesis.

FCR activity of cIE vesicles isolated from Fe‐deficient plants also showed clear biphasic kinetics, where the KM of the low affinity component was elevated, and thus this component was down‐regulated.
Anxiety and stress in mothers of food‐allergic children
Authors: Lau Gar‐Yen , Patel Nisha , Umasunthar Thisanayagam , Gore Claudia , Warner John O. , Hanna Heather , Phillips Katherine , Mohd Zaki Amirah , Hodes Matthew , Boyle Robert J.
Published: February 2014

Background

Previous reports suggest that parents especially mothers of food‐allergic children may have increased anxiety. Studies with an appropriate control group have not been undertaken, and the determinants of such anxiety are not known. We compared measures of anxiety and stress in mothers of food‐allergic children and atopic non‐food‐allergic children, with anxiety and stress in mothers of children with no chronic illness.

Methods

Cross‐sectional study of mothers attending a hospital appointment for their 8‐ to 16‐year‐old child. Mothers of children with food allergy, asthma but no food allergy or no chronic illness completed questionnaires including State‐Trait Anxiety Inventory, Perceived Stress Scale and measures of anxiety and psychologic adjustment in their child.

Results

Forty mothers of food‐allergic children, 18 mothers of asthmatic children without food allergy and 38 mothers of children with no chronic illness (controls) were recruited. Mothers of food‐allergic children showed increased state anxiety – median anxiety score 38.0 (IQR 30.0, 44.0) food allergy, 27.0 (22.0, 40.0) control p = 0.012; and increased stress – median stress score 18.5 (12.0, 22.0) food allergy, 14.0 (7.5, 19.5) control p = 0.035. No significant differences were seen between mothers in the asthmatic group and controls. In multivariate analysis, previous food anaphylaxis (p = 0.008) and poorly controlled asthma (p = 0.004) were associated with increased maternal anxiety. Child anxiety and adjustment did not differ between food‐allergic and control groups.

Conclusions

Mothers of food‐allergic children have increased anxiety and stress compared with mothers of children with no chronic illness. Anaphylaxis and poorly controlled asthma are associated with maternal anxiety.
A novel KIR3DL1*0200102 allele isolated from a West African donor by sequence‐based typing
Authors: Yindom L.‐M. , de Silva T. I. , Rowland‐Jones S. L.
Published: February 2014

KIR3DL1*0200102 allele differs from KIR3DL1*0200101 with four single nucleotide polymorphisms in introns 5 and 6, respectively.
A Study on SCWR Core Design and Fuel Management
Authors: Zhang Yong , Yang Jue , Li Dongsheng , Cao Liangzhi , Wang Fei , Zhao Shuai , Li Hongbo
Published: February 2014

A type of SCWR core design with Double-row fuel rods assembly will be introduced in this paper. The Double-row fuel rods SCWR (DL-SCWR) core is designed for reaching a thermal power of 2280 MW with an equivalent diameter of 3.16 m and length of 4.20 m. There are 249 fuel assemblies in the core, and 180 fuel rods in each assembly. The inlet coolant temperature is 280 °C and the operation pressure is 25 MPa. There are 80 fresh assemblies in the equilibrium cycle. The numerical results show that the average discharged burnup of the equilibrium is 37 GWD/tU, and the average temperature of outlet coolant is 500°C. In the equilibrium cycle, the maximum cladding surface temperature is less than 650 °C.
Investigation of Steady-State Characteristics of Natural Circulation Loop
Authors: Huang Zheng
Published: February 2014

Natural circulation is one of the most important mechanisms of passive safety systems in the advanced NPP design. By using RELAP5, steady-state behaviors of a typical natural circulation loop (NCL) were investigated. The Influences of various system parameters, such as pressure, cooling heat transfer area and loop height were studied. The results show that the heat transfer power of the NCL (i.e. the heat transferred from the heater to the tank by NCL) is linear with respect to the temperatures of boundary heat source and sink, excluding the phase transition region. The NCL operation mode (i.e. two-phase flow or one-phase flow) is mainly determined by the loop pressure. It is found that with the decrease of the pressure, the two-phase flow operation range is widened. The heat transfer power of two-phase flow case is always higher, and varies more substantially with pressure, than that of one-phase flow case under the same boundary temperatures. However, flow instability may occur for two-phase flow case. By increasing the area of heat transfer surface between loop cooling section and tank, the temperature difference between the inlet and the outlet of loop heating section as well as the heat transfer power of the NCL will increase. But the influence is insignificant when the tank temperature is relatively high. It is also observed that for both one-phase flow and two-phase flow, the change of loop height has little effect upon the heat transfer power of the NCL under the given boundary condition in this study.
Researches on the Simulation of the Degasifying Column Used in Nuclear Power Plant
Authors: Xie Jianhua , Ye Quanliu , Yang Jinchun
Published: February 2014

The degasifying column is an important unit in nuclear power station. In order to verify the performance of the column, the degasifying process has been simulated by using the well-known software ASPEN Plus and on a basis of some proper hypothesizes and simplified models. Degasifying column is found that it has good capability on taking out key components such as krypton and oxygen from reactor coolant. On the other side, it’s difficult to carry out radioactive gas experiment on site which is seriously enslaved to the potential radioactive harm on operators. Simulation by using ASPEN Plus is a good way to solve this problem. Furthermore, three kinds of experiments such as ASPEN simulation, deoxidation experiment and radioactive gas experiment on site which are used for validating the performance of column are compared. The comparison shows that ASPEN simulation has less risk and less costs, but the simulation results are more exact and credible. Moreover, the debugging process of the column can be inducted and improved according to the simulation.
The Discussion of Nuclear Power Plant’s Cooling Chain Design for Freezing Site
Authors: Hu Jian , Jiang Xulun , Yang Ting , Xiao Wei , Wang Zhengguang
Published: February 2014

In order to satisfy the IAEA safety requirement, the conservative design of Nuclear Power Plant’s (NPP) cooling chain is applied by consideration of maximum heat load and high ultimate heat sink temperature. However, for the freezing site, combined with the low heat load in cooling chain, the low service water temperature in winter may possibly causes the unavailability of cooling chain.

This paper is mainly focused on the once-through cooling chain design at freezing site. By analyzing the thoughts and applicability of different kinds of cooling chain design for anti-freezing consideration, one solution called “SEC thermal discharge reflux” is proposed. The solution has already been approved by National Nuclear Safety Administration (NNSA) in China, and applied in one of the northern China NPP.

Comparing with the traditional anti-freezing designs, the solution has its feature as “Reactor low power operation”, “Reactor first time start-up” and “Change-over of RRI/SEC trains in winter”. Besides, it is also able to prevent the heat exchanger of RRI side from icing and SEC side from sediment deposition and mussel growth. The solution is applicable for once-through cooling type NPP, and is not restricted by the reactor type.
Studies on Source Effect in Experimental Design for Passive Cooling in Large Cavities Under LOCA conditions
Authors: Li Shengqiang , Xiong Yin , Hao Yalei , Zhu Hongyu , Jiang Shengyao
Published: February 2014

In recent years, most of the advanced Pressurize Water Reactor (PWR) design contains passive cooling features, especially for the containments, which are functioning as the final radioactive emission barriers. To evaluate the best estimation codes for containment design, large scale thermo-hydraulic experimental facilities will be necessary for Code Verification and validation (V&V). Normally, the multi-phase jet is the main source for containment thermo-hydraulic processes under Loss of Coolant Accident (LOCA) conditions. This paper presents the scaling studies of source effects in large cavity experiment facility design. The similarity in core safety features, such as cavity temperature and pressure, is preserved firstly in the scaling and some dominant design parameters are given. Some primary design features are decided. The jet mass flow rate and heat sink surface ratios are provided for the prevailing parameters for system transient simulation. Based on mass and energy conservative equations, the parameters ratio for jet mass flow rate, jet time scale, jet integral energy, break size and expansion structures size are determined. Furthermore, some transient multidimensional phenomena are also considered. A novel six regions hierarchical model is similarly provided specially for cavity space scaling. The interaction between jet and space natural circulation was modeled. The local heat and mass transfer simulation and system level evaluation are coherence in the experimental design. Based on the preceding results, estimation for distortion on experiments can also be made to evaluate the experimental data deviations from prototype design.
The Severe Accident Analysis of CPR1000 Based on MELCOR Code
Authors: Li Longze , Wang Mingjun , Tian Wenxi , Su Guanghui , Qiu Suizheng
Published: February 2014

The severe accident of CPR1000 caused by station blackout with the SG safety valve failure is simulated and analyzed using MELCOR code in this work. The CPR1000 power plant severe accident response process and the results with three different assumptions, which are no the seal leakage nor the auxiliary feed water, the seal leakage and auxiliary feed water exist, the seal leakage exist but no auxiliary feed water separately, are analyzed. According to the calculation results, without the seal leakage and auxiliary feed water, pressure vessel would fail at 9576 s. When auxiliary feed water was supplied, pressure vessel’s failure time would delay nearly 30000s. When the seal leakage exists, pressure vessel’s failure time would delay about 50 s. The results are meaningful and significant for comprehending the detailed process of severe accident for CPR1000 nuclear power plant, which is the basic standard for establishing the severe accident management guideline.
The Graphite Particle Movement in Fuel Handing System Bend Pipe in the High Temperature Gas-Cooled Reactor
Authors: Zhang Jinyi , Bo Hanliang , Hu Wenping
Published: February 2014

A typical bend pipe in the fuel transporting and refueling system in the HTR is studied. The helium three-dimension flow field in the bend pipe is simulated and the graphite dust particle movement and impingement in the helium flow field are researched by numerical simulation. The trajectories of graphite particles with different diameters and different initial positions are simulated. The position and probability of the graphite particle collision is studied by the numerical simulation on the particle movement.
Historical Perspectives and Insights on ACRS Review of AP1000 Design Certification
Authors: Nourbakhsh Hossein , Wang Weidong , Ray Harold , Kress Thomas
Published: February 2014

The U.S. Nuclear Regulatory Commission (NRC) requires that each application for a standard design certification be referred to the Advisory Committee on Reactor Safeguards (ACRS) for a review and report on those portions of the application which concern safety. This paper begins with perspectives on the role of the ACRS in the design certification review process. It then summarizes the ACRS observations and recommendations made in the Committee’s reports during the AP1000 design certification reviews to date.
The Mechanism of Two Phase Flow Instability Enhanced the Interface Mass Transfer
Authors: Yang Yan , Pan Liang-ming , Hang Liu
Published: February 2014

Two phase flow instability is a common phenomenon in many applications such as nuclear reactor, boiler, heat exchanger, chemical reactor, etc. Flow instability will cause mechanical vibration, which may bring about the local heat transfer deterioration. But for the gas-liquid reactor, the mechanical vibration caused by flow instability will strengthen the destabilization and increase the mass transfer at the gas-liquid interface. Therefore, the mass transfer will be enhanced. Such as in nuclear reactor, we need increase the mass transfer of boron. Currently, few studies did the researches on the mechanism of mass transfer enhancement and regular pattern of interface phenomenon caused by two phase flow instability. This paper deals with the problems in improving the mass transfer at two phase interface, studies the effects of flow pattern on the transfer characteristics and the influence of bubble’s growth and aggregation on the mass flow rate and outlet pressure. The mechanism and the regular pattern of interface destabilization are analyzed. The results reveal that the two phase instability has significant effects on the mass transfer through the interface.
Analysis of Factors Influencing Compressive Bearing Capacity of Nuclear Containment
Authors: Hou Gangling , Song Chenning , Song Tianshu , Zhou Guoliang
Published: February 2014

Nuclear containment protects nuclear island from serious accident, while its compressive bearing capacity remains the key problem to nuclear safety. With reference to one nuclear containment, the special concrete damaged plasticity model in software ABAQUS, this article systematically analyzes influencing rules of compressive bearing capacity and factors such as gravity, steel liner, prestressed tendons etc. The result shows that steel liner and prestressed tendons play key parts in deformation inhibition and the failure mode of nuclear containment, meanwhile prestressed tendons are crucial to improve the compressive bearing capacity.
Numerical Study on the Influence of Non-Uniform Wall Roughness on Vortex Structure in Sparse Lattice
Authors: Xiao Hongguang , Zhang Yangwei , Yan Binghuo , Chen Wenzhen
Published: February 2014

Quasi periodic large scale vortex structure is an important phenomenon in rod-bundle-like lattice, which also plays an important role in the local flow and heat transfer around bundles. In this work, the heat transfer and vortex structure in sparse lattice with non-uniform wall roughness are investigated with the unsteady Reynolds-Averaged Navier-Stokes (URANS) simulation with a Reynolds Stress Model (RSM) in FLUENT 6.3. The pitch to diameter ratio (P/D) of the sparse lattice is 1.12. It is found that the transverse flow mixing, heat transfer and the vortex structure are enhanced with the wall roughness increasing.
Live Experimental Results of Melt Pool Behaviour in the PWR Lower Head With Insulated Upper Lid and External Cooling
Authors: Gaus-Liu Xiaoyang , Miassoedov Alexei
Published: February 2014

In-vessel melt retention has drawn renewed concern as an important severe accident management measure in existing and advanced light water reactors. Despite numerous studies the central question whether the maximum heat flux in a melt pool could exceed the critical heat flux (CHF) is not fully answered. The uncertainty comes from the variety of accident scenarios and the corresponding melt pool configurations, as well as from the applicability of the experimental results to the reactor case. It is therefore necessary to examine the melt heat transfer under different pool configurations and cooling conditions, as well as to compare the experimental results coming from different test vessel geometries and cooling regimes.

This study investigates the heat transfer characteristics of an oxidic pool in the PWR lower plenum in the case when the vessel wall is externally cooled by water, and the melt upper surface is free in a closed insulated environment. Thus the melt pool cooling conditions are quasi-isothermal at the inclined sidewall and at the upper surface free surface with thermal radiation. This pool configuration can occur before the melt layer stratification begins or the melt pool is composed only of oxide melt under certain melt relocation sequences.

A non-eutectic nitrate mixture with the composition of 20% NaNO3−80% KNO3 in mole relation is used as the simulant melt. Besides the determination of melt temperature and heat flux in their global average values, emphasis are given on the characterization of the axial distribution of melt temperature and heat flux at different power densities and pool heights. Results obtained in hemispherical geometry are analyzed and compared with other studies conducted under similar boundary conditions. The characterization of the heat flux distribution provide important data for the prediction of the maximum heat flux in the reactor case with similar boundary conditions and the evaluation of the concept of in-vessel melt retention by external cooling.
A New Design for SCWR Fuel Assemblies
Authors: Lu Donghua , Yang Jue , Su Qianhua , Wen Qinglong
Published: February 2014

A new type of fuel assemblies (FAs) was designed for super critical water reactors (SCWRs). A square FA is composed by 16 rectangular channels. Each channel has 26 fuel rods that are arranged into two rows and enclosed by thermal walls. The gap between each channel acts as water rods as usual design does. Flat absorbers are used as the control rods. They are placed in the gaps. Then computational fluid dynamics (CFD) was used to evaluate the design. The results show mixing vanes can lower the peak cladding temperature of fuel rods. The thermal wall between cold water rods and subchannels should be optimized to produce reasonable heat transfer.
Research on Adsorption Performance of Type III Adsorber Used in Nuclear Power Plant
Authors: Xu Xin , Yu Lian-tao
Published: February 2014

Based on operational principle and performance analysis of type III adsorber, a set of test platform for type III adsorber adsorption performance test is designed. After testing of the prototype and analyzing the test data, it is concluded that the prototype is qualified to be used in nuclear power plant and it fills the gap in China.
Capacity Calculation Method Study on the Emergency Diesel Generator Applied in HTR-PM
Authors: Chen Fan , Sun Weidong , Sun Linna
Published: February 2014

The paper introduces the capacity calculation method of emergency diesel generator sets applied in the HTR-PM, which is a demonstration project in China. This project is currently in the construction design stage. The designed reactor power is 250MW. Totally two class 1E emergency diesel generator sets are required for the safety of reactors. Due to the inherent safety feature of the reactor, the amount of safety related loads is comparatively less than regular PWRs in China. Therefore, the capacity calculation method basing on the composition of the shaft power of each electrical device is no longer suitable for this project. According to the loading features and loading sequence of the generator sets, the paper proposes a new method which uses conversion coefficient method in the load statistical process and analyzes the required capacity values for the generator sets in both steady and transient states. Basing on those values, by considering the performances of diesel engine and generator respectively, the ultimate capacity of two emergency diesel generator sets is able to be determined. In the process of load statistics, emergency loads of the generator sets are divided into several categories such as static loads, motor loads, power electronic loads, et al. In order to guarantee the accuracy of the calculation, several major parameters of the equation set are verified by targeted experiments. In order to ensure the power quality and safety of the emergency power system of the project, the voltage deviation caused by the startup of large capacity motor is verified as well.
Analysis of the Influence of Spot Diameter of Point Sources on HPGE Detector Γ-Ray Efficiencies Simulation for Volume Source
Authors: Tian Zining , Ouyang Xiaoping , Zeng Ming , Cheng Zhiwei
Published: February 2014

The concept of transforming the detector efficiency of ϕ 75mm×20mm 13737Cs gas sample to a virtual 137Cs point source simulation, in order to facilitate efficiency evaluations for different source location, was proposed for the HPGe detector. The virtual point source usually has spot diameter, so, analysis of the influence of spot diameter of point source was studied in the present work. It was found that the point source model does not seem to fit too well to the experimental data, for the small source-to-detector distances. A multi-parameter polynomial expression describing the dependence of the count rate versus the source-to detector distance was fitted to the experimental data. The point source (ϕ 4.0mm) and small disk source (ϕ 20mm) were used in this experimental simulation, and their result discrepancy was 5.6%. Monte Carlo simulations were also used to study above experiment process, the discrepancy was 2.6%. For another simulation, the point source (ϕ 4.0mm) and ideal point source (ϕ 0.0mm) were used in Monte Carlo simulation, and their result discrepancy was zero. So, for the whole gas sample simulation, the influence of spot diameter of point source can be neglected in this simulation method.
Hybrid Feedforward and Feedback Control of Steam Temperature in a Once-Through Direct Cycle Canadian SCWR
Authors: Sun Peiwei , Zhang Jianmin
Published: February 2014

Supercritical Water-cooled Reactor (SCWR) is the only water cooled reactor proposed for Generation IV potential nuclear reactors. Canadian SCWR is a pressure-tube type SCWR under development in Canada. A linearized dynamic model of the Canadian SCWR is developed based on the lumped-parameter method to investigate its dynamic characteristics. Through dynamic analysis, the Canadian SCWR can be modelled as a three-input and three-output system with high power-to-flow ratio and strong cross-coupling. Among the three outputs, the dynamics of the steam temperature are the most complex and vulnerable to disturbances, especially those from the reactor power. It is difficult and challenging to control the steam temperature.

In this paper, a hybrid feedforward and feedback control strategy is adopted for control system design of the steam temperature. Feedforward control can reduce the effect of the measured disturbance on the steam temperature. It starts to act before the disturbance actually affects the steam temperature. Feedback control is used to track the setpoint change and suppress unmeasured disturbances. The uncompensated effects from the feedforward control can also be eliminated by the feedback control. Combined feedforward and feedback control scheme can significantly improve performance.

The feedforward controller and feedback controller are designed based on the linearized dynamic model. The control performance is verified using nonlinear dynamic model. Through simulation, the steam temperature variation using designed control system satisfies its limit to a typical load pattern.
Study on the Prestressing Effect in Reinforced Concrete Containment by Using ANSYS
Authors: Sun Feng , Pan Rong
Published: February 2014

Prestressed reinforced concrete containment is an important part among the safety-related buildings, and the presressing technology is widely used in containment construction which is best suited to the cylindrical-type containment topped by a dome. It has been recognized that traditional methods for analysis of containment prestressing system have been unable to satisfy more accurate design, research and monitoring requirements. Prestressing tendons are placed complexly in containment structure, especially near the major equipment hatch area, which is the three-dimensional curve and the friction loss must be considered. Firstly, containment structure and the distribution of prestresseing system are introduced briefly. Furthermore, the calculating process of prestressing tendons losses is put forward in details which take the major equipment hatch as an example. Solid65 element and constitutive model of concrete in ANSYS are introduced in details, and the characteristic of simulating prestressing tendons in ANSYS is analyzed.

Based above study, finite element model of the prestressed structure is built based on some concrete containment by using ANSYS program, the prestressing effect on concrete containment is put forward. The numerical results show that most of the design pressure is beared by the prestressing system under the design-basis pressure condition, and the simulation method is effective with a high accuracy which agrees well with stress tests performed on-site in some operating NPPs such as LINGAO PHASE II.
Research for Crossing Strait Transportation Accident of Nuclear Fuel Assemblies
Authors: Xu Xiaoxiao , Wang Xuexin , Zhang Jiangang , Li Chaoduan , Fan Gao , Tang Rongyao , Cao Lian , Wen Bing
Published: February 2014

Hainan nuclear power plant (HNPP) is the first nuclear power plant built on China’s Hainan Island. Therefore the nuclear fuel assemblies must transport through the Qiongzhou Strait.

There are two transportation plans to be used in crossing strait transportation of the fuel assemblies. One plan is railway ferry stretching across sea; the other is road vehicular crossing strait on roll-on/roll-off (Ro/Ro) ships.

According to crossing strait transportation scenario and statistical analysis of sea transport accidents in Qiongzhou Strait, three ferrying transportation accidents are considered in this paper. Through research of ship-to-ship collision, fire and sunk, the following conclusions: Collision, fire or foundered are not caused by the leakage of radioactive material, the environmental impact is very small. The accident hazards of crossing strait transportation does not lie in the radiological consequences, but in the effects of public psychology and international repercussions.
Analysis of Dynamic Effects Associated With Postulated Breaks of Piping
Authors: Qin Manqing , Li Xinghua , Zhao Jicheng
Published: February 2014

High energy pipe break hypothesis and engineering practice shall be taken into account and performed during nuclear power plant design due to defense-in-depth concept unless leak-before-break or break preclusion concept is applied. High energy pipe breaks potentially occur in the high stress area and break locations can be recognized by specific regulations based on mechanical analysis of piping systems. Engineering measures shall be applied to mitigate the consequences caused by high energy pipe breaks later.

From engineering point of view High Energy Line Break analysis requires an essential knowledge in the different fields, such as: structural and dynamic mechanics, hydrodynamics, plant arrangements and so on.

Aims of this paper consist of two aspects: definition of break locations associated with engineering practice of piping stress analysis and a conservative model of anti-whip analysis based on some assumptions. Comparison results are given after analytical investigation of the piping whip analysis with different numerical modeling and tools at the same time. An example of such comparison between transient model and energy balance methods is performed based on some basic assumptions in relation to specific piping layout.

The simplified calculation model appears well for a conservative estimation of pipe whip characteristics, both for maximum displacements of piping and maximum loads impacted on anti-whip restraints.
Thermal and Stability Considerations for a Supercritical Water-Cooled Fast Reactor During Pressurization Phase of Plant Sliding Pressure Startup
Authors: Cai Jiejin , Tang Qi
Published: February 2014

This paper describes the studies on the procedure of the pressurization phase of plant sliding pressure startup for the supercritical water-cooled fast reactor (SWFR). Thermal analysis and thermal-hydraulic stability analysis models for SWFR are developed and validated using the available references’ experimental data. The models are then used to analyze the pressurization phase to obtain the available plant parameters from the points of view of the thermal-hydraulic and stability. The three hot channels, two seed assemblies with upward/downward flow and a blanket assembly during pressurization are analyzed at both beginning of equilibrium cycle (BOEC) and end of equilibrium cycle (EOEC). Results show that the proposed pressurization procedure of the plant sliding pressure startup for SWFR is feasible and both the thermal and stability criteria can be satisfied during the pressurization phase.
ASSERT-PV 3.2: Improved Subchannel Thermalhydraulics Code for CANDU Fuel Bundles
Authors: Rao Y. F. , Cheng Z. , Waddington G. M. , Nava-Dominguez A.
Published: February 2014

Atomic Energy of Canada Limited (AECL) has developed the subchannel thermalhydraulics code ASSERT-PV for the Canadian nuclear industry. The most recent release version, ASSERT-PV 3.2 has enhanced phenomenon models for improved predictions of flow distribution, dryout power and CHF location, and post-dryout (PDO) sheath temperature in horizontal CANDU fuel bundles. The focus of the improvements is mainly on modelling considerations for the unique features of CANDU bundles such as horizontal flows, small pitch to diameter ratios, high mass fluxes, and mixed and irregular subchannel geometries, compared to PWR/BWR fuel assemblies. This paper describes the model changes or additions in the new version to improve predictions of flow distribution, dryout power and CHF location, and PDO sheath temperature.