WorldWideScience
 
 
1

[The regulation of human cardiac activity during the cyclical change of barometric pressure under sealed-cabin conditions].  

Science.gov (United States)

A cyclic change of barometric pressure from 790 to 720 mm Hg once a day to twice within 3 days under sealed conditions results in a functional rearrangement of the mechanisms to control cardiac activity which cause the predominance of vagotonic responses determined by a decrease of the body reserves and its asthenization. At the beginning of staying under pressurized conditions (2nd week) it appears as an occurrence of meteorotropic responses (in 13% of subjects tested) and at the end of living in pressurized conditions (9th week) as a significant decline with a change ("removal") in: pressure, index of strain, vegetative index of rhythm, index of regulation processes, index of vegetative equilibrium and as an increase in the number of individuals responding to a cyclic change of barometric pressure up to 44% which is indicative of a moderate relationship between manifestation rate of these sensations and an effect duration of a given factor. PMID:1363596

Novikov, V S; Myznikov, I L; Bortnovski?, V N

1992-01-01

2

Barometric pressure transient testing applications at the Nevada Test Site: formation permeability analysis. Final report  

Energy Technology Data Exchange (ETDEWEB)

The report evaluates previous investigations of the gas permeability of the rock surrounding emplacement holes at the Nevada Test Site. The discussion sets the framework from which the present uncertainty in gas permeability can be overcome. The usefulness of the barometric pressure testing method has been established. Flow models were used to evaluate barometric pressure transients taken at NTS holes U2fe, U19ac and U20ai. 31 refs., 103 figs., 18 tabs. (ACR)

Hanson, J.M.

1984-12-01

3

Barometric pressure transient testing applications at the Nevada Test Site: formation permeability analysis. Final report  

International Nuclear Information System (INIS)

The report evaluates previous investigations of the gas permeability of the rock surrounding emplacement holes at the Nevada Test Site. The discussion sets the framework from which the present uncertainty in gas permeability can be overcome. The usefulness of the barometric pressure testing method has been established. Flow models were used to evaluate barometric pressure transients taken at NTS holes U2fe, U19ac and U20ai. 31 refs., 103 figs., 18 tabs

1984-01-01

4

Removal of barometric pressure effects and earth tides from observed water levels.  

Science.gov (United States)

The effects of barometric pressure and earth tide changes are often observed in ground water level measurements. These disturbances can make aquifer test interpretation difficult by masking the small changes induced by aquifer testing at late times and great distances. A computer utility is now available that automatically removes the effects of barometric pressure and earth tides from water level observations using regression deconvolution. This procedure has been shown to remove more noise then traditional constant barometric efficiency techniques in both confined and unconfined aquifers. Instead of a single, instantaneous barometric efficiency, the procedure more correctly accounts for the lagged responses caused by barometric pressure and earth tide changes. Simultaneous measurements of water levels (or total heads) and nearby barometric pressures are required. As an additional option, the effects of earth tides can also be removed using theoretical earth tides. The program is demonstrated for two data sets collected at the Waste Isolation Pilot Plant, Carlsbad, New Mexico. The program is available free by request at http://www.hydrology.uga.edu/tools.html. PMID:17257346

Toll, Nathanial J; Rasmussen, Todd C

2007-01-01

5

Insights into aquifer vulnerability and potential recharge zones from the borehole response to barometric pressure changes  

Science.gov (United States)

Borehole water levels fluctuate in response to deformation of the surrounding aquifer caused by surface loading due to barometric pressure or strain caused by Earth and ocean tides. The magnitude and nature of this response mainly depend on the hydraulic properties of the aquifer and overlying units and borehole design. Thus water level responses reflect the effectiveness of a confining unit as a protective layer against aquifer contamination (and therefore groundwater vulnerability) and to potential aquifer recharge/discharge zones. In this study, time series of borehole water levels and barometric pressure are being investigated using time series analysis and signal processing techniques with the aim of developing a methodology for assessing recharge/discharge distribution and groundwater vulnerability in the confined/semi-confined part of the Chalk aquifer in East Yorkshire, UK. The chalk aquifer in East Yorkshire is an important source for industrial and domestic water supply. The aquifer water quality is threatened by surface pollution particularly by nitrates from agricultural fertilizers. The confined/semi-confined part of this aquifer is covered by various types of superficial deposits resulting in a wide range of the aquifer's degree of confinement. A number of boreholes have been selected for monitoring to cover all these various types of confining units. Automatic pressure transducers are installed to record water levels and barometric pressure measurements at each borehole on 15 minutes recording intervals. In strictly confined aquifers, borehole water level response to barometric pressure is an un-drained instantaneous response and is a constant fraction of the barometric pressure changes. This static confined constant is called the barometric efficiency which can be estimated simply by the slope of a regression plot of water levels versus barometric pressure. However, in the semi confined aquifer case this response is lagged due to water movement between the aquifer and the confining layer. In this case the static constant barometric efficiency is not applicable and the response is represented by a barometric response function which reflects the timing and frequency of the barometric pressure loading. In this study, the barometric response function is estimated using de-convolution techniques both in the time domain (least squares regression de-convolution) and in the frequency domain (discrete Fourier transform de-convolution). In order to estimate the barometric response function, borehole water level fluctuations due to factors other than barometric pressure should be removed (de-trended) as otherwise they will mask the response relation of interest. It is shown from the collected borehole data records that the main four factors other than barometric pressure contribute to borehole water level fluctuations. These are the rainfall recharge, Earth tides, sea tides and pumping activities close to the borehole location. Due to the highly variable nature of the UK weather, rainfall recharge shows a wide variation throughout the winter and summer seasons. This gives a complicated recharge signal over a wide range of frequencies which must be de-trended from the borehole water level data in order to estimate the barometric response function. Methods for removing this recharge signal are developed and discussed. Earth tides are calculated theoretically at each borehole location taking into account oceanic loading effects. Ocean tide effects on water levels fluctuations are clear for the boreholes located close to the coast. A Matlab code has been designed to calculate and de-trend the periodic fluctuations in borehole water levels due to Earth and ocean tides using the least squares regression technique based on a sum of sine and cosine fitting model functions. The program results have been confirmed using spectral analysis techniques.

El Araby, Mahmoud; Odling, Noelle; Clark, Roger; West, Jared

2010-05-01

6

Suitability of commercial barometric pressure sensors to distinguish sitting and standing activities for wearable monitoring.  

Science.gov (United States)

Despite its medical relevance, accurate recognition of sedentary (sitting and lying) and dynamic activities (e.g. standing and walking) remains challenging using a single wearable device. Currently, trunk-worn wearable systems can differentiate sitting from standing with moderate success, as activity classifiers often rely on inertial signals at the transition period (e.g. from sitting to standing) which contains limited information. Discriminating sitting from standing thus requires additional sources of information such as elevation change. The aim of this study is to demonstrate the suitability of barometric pressure, providing an absolute estimate of elevation, for evaluating sitting and standing periods during daily activities. Three sensors were evaluated in both calm laboratory conditions and a pilot study involving seven healthy subjects performing 322 sitting and standing transitions, both indoor and outdoor, in real-world conditions. The MS5611-BA01 barometric pressure sensor (Measurement Specialties, USA) demonstrated superior performance to counterparts. It discriminates actual sitting and standing transitions from stationary postures with 99.5% accuracy and is also capable to completely dissociate Sit-to-Stand from Stand-to-Sit transitions. PMID:24485500

Massé, F; Bourke, A K; Chardonnens, J; Paraschiv-Ionescu, A; Aminian, K

2014-06-01

7

The effects of temperature, humidity, and barometric pressure on short-sprint race times  

Science.gov (United States)

A numerical model of 100 m and 200 m world class sprinting performances is modified using standard hydrodynamic principles to include effects of air temperature, pressure, and humidity levels on aerodynamic drag. The magnitude of the effects are found to be dependent on wind speed. This implies that differing atmospheric conditions can yield slightly different corrections for the same wind-gauge reading. In the absence of wind, temperature is found to induce the largest variation in times (0.01 s per 10 degrees C increment in the 100 m), while relative humidity contributes the least (under 0.01 s for all realistic conditions for 100 m). Barometric pressure variations at a particular venue can also introduce fluctuations in performance times on the order of a 0.01 s for this race. The combination of all three variables is essentially additive, and is more important for head-wind conditions that for tail-winds. As expected, calculated corrections in the 200 m are magnified due to the longer duration of the race. The overall effects of these factors on sprint times can be considered a ``second order'' adjustment to previous methods that rely strictly on a venue's physical elevation, but can become important in extreme conditions.

Mureika, J. R.

2006-04-01

8

The Effects of Temperature, Humidity and Barometric Pressure on Short Sprint Race Times  

CERN Document Server

A numerical model of 100 m and 200 m world class sprinting performances is modified using standard hydrodynamic principles to include effects of air temperature, pressure, and humidity levels on aerodynamic drag. The magnitude of the effects are found to be dependent on wind speed. This implies that differing atmospheric conditions can yield slightly different corrections for the same wind gauge reading. In the absence of wind, temperature is found to induce the largest variation in times (0.01 s per $10\\dc$ increment in the 100 m), while relative humidity contributes the least (under 0.01 s for all realistic conditions for 100 m). Barometric pressure variations at a particular venue can also introduce fluctuations in performance times on the order of a 0.01 s for this race. The combination of all three variables is essentially additive, and is more important for head-wind conditions that for tail-winds. As expected, calculated corrections in the 200 m are magnified due to the longer duration of the race. The...

Mureika, J R

2006-01-01

9

Activity classification based on inertial and barometric pressure sensors at different anatomical locations.  

Science.gov (United States)

Miniature, wearable sensor modules are a promising technology to monitor activities of daily living (ADL) over extended periods of time. To assure both user compliance and meaningful results, the selection and placement site of sensors requires careful consideration. We investigated these aspects for the classification of 16 ADL in 6 healthy subjects under laboratory conditions using ReSense, our custom-made inertial measurement unit enhanced with a barometric pressure sensor used to capture activity-related altitude changes. Subjects wore a module on each wrist and ankle, and one on the trunk. Activities comprised whole body movements as well as gross and dextrous upper-limb activities. Wrist-module data outperformed the other locations for the three activity groups. Specifically, overall classification accuracy rates of almost 93% and more than 95% were achieved for the repeated holdout and user-specific validation methods, respectively, for all 16 activities. Including the altitude profile resulted in a considerable improvement of up to 20% in the classification accuracy for stair ascent and descent. The gyroscopes provided no useful information for activity classification under this scheme. The proposed sensor setting could allow for robust long-term activity monitoring with high compliance in different patient populations. PMID:24853451

Moncada-Torres, A; Leuenberger, K; Gonzenbach, R; Luft, A; Gassert, R

2014-07-01

10

Stochastic Inversion of Pneumatic Cross-hole Tests and Barometric Pressure Fluctuations in Heterogeneous Unsaturated Formations  

Science.gov (United States)

The distributions of permeability and porosity are key factors that control airflow and gas phase transport in unsaturated formations. To understand the behavior of flow and transport in such formations, characterization procedure is a typical approach that has been widely applied to laboratories and fields. As is recognized by most investigations, this approach relies on accurate measurements, and more importantly, an adequate tool to interpret those measurements from experiments. This study presents a pneumatic inverse model that is capable to estimate the distributions of permeability (Ka) and porosity (n) with high resolution in heterogeneous unsaturated formations. Based on the concept of sequential successive linear estimator (SSLE), the developed model accounts for compressibility and density of air and estimates the geologic parameters using air pressure measurements from sequential cross-hole pneumatic pumping or injection tests. Four synthetic examples, including a one-dimensional well-posed, a horizontally two-dimensional, and two three-dimensional problems, are used to evaluate the developed model in estimating the distributions of permeability and porosity in unsaturated formations. Results of the numerical experiments are promising. The developed pneumatic inverse model can reconstruct the property (i.e., permeability and porosity) fields if the well-defined conditions are met. With relatively small number of available measurements, the proposed model can accurately capture the patterns and the magnitudes of estimated properties for unsaturated formations. Results of two complex three-dimensional examples show that the proposed model can map the fracture connectivity using relatively small number of subsurface pressure measurements and estimate and in shallow soil layers using spatial variations of barometric pressure.

Ni, C.-F.; Yeh, T.-C. J.; Hsu, H.-H.; Deng, Y.-T.

2009-04-01

11

Barometric pressure forcing on radon-222 and temperature in fumarolic gases: a tool to describe flow-rate dynamics  

Science.gov (United States)

We propose two conceptual models for the dynamics of fumarolic gases, during their ascent through the volcano plumbing, based on radon-222 and temperature data collected on fumaroles of La Soufrière volcano (Guadeloupe,FWI) together with local barometric pressure, and on a new interpretation of older data collected on Merapi volcano (1), Indonesia. All these in-situ measurements prove that the diurnal (24h, S1 barometric wave) and semidiurnal (12h, S2 barometric wave) variations in radon concentration are clearly observable, and positively or negatively correlated with barometric pressure variation. Two models are used to interpret this correlation. The first model, called “Accumulation mode”, is characterized by an initial and negligible deep radon-222 source and by a major contribution of radon-222 from conduit walls and connected fractures (emanation and exhalation mechanisms) during the gas ascent through the fumarolic system. This model is substantiated by a positive correlation between radon and pressure in the Merapi fumaroles. The second model, or “Decay mode”, is exemplified by a negative correlation between radon and pressure as measured in fumaroles at La Soufrière volcano. It is characterized by radioactive decay of a strong initial radon-222 source generated by a deeper reservoir (hydrothermal system or magmatic chamber) whereas contribution by conduit walls and connected fractures to the total radon-222 activity in the fumarole is comparatively minor during the transit time of the gas. In these two modes, it is possible to infer that, for transit times longer than ca. 21 days, the barometric pressure does not modulate the radon signal. Thus, the simultaneous monitoring of radon-222, temperature and barometric pressure provides a precise fumarole flowmeter. In addition, it is a tool to decipher shallow versus deep feeding of volcanic fumaroles that should prove useful for volcano monitoring. (1)Zimmer, M. & Erzinger, J. Continuous H2O, CO2, 222Rn and temperature measurements on Merapi Volcano, Indonesia. J. Volcanol. Geoth. Res. 125, 25-38 (2003).

Richon, P.; Salaun, A.; Boudon, G.; Villemant, B.; Crispi, O.; Sabroux, J.

2010-12-01

12

Energy expenditure estimation during normal ambulation using triaxial accelerometry and barometric pressure.  

Science.gov (United States)

Energy expenditure (EE) is an important parameter in the assessment of physical activity. Most reliable techniques for EE estimation are too impractical for deployment in unsupervised free-living environments; those which do prove practical for unsupervised use often poorly estimate EE when the subject is working to change their altitude by walking up or down stairs or inclines. This study evaluates the augmentation of a standard triaxial accelerometry waist-worn wearable sensor with a barometric pressure sensor (as a surrogate measure for altitude) to improve EE estimates, particularly when the subject is ascending or descending stairs. Using a number of features extracted from the accelerometry and barometric pressure signals, a state space model is trained for EE estimation. An activity classification algorithm is also presented, and this activity classification output is also investigated as a model input parameter when estimating EE. This EE estimation model is compared against a similar model which solely utilizes accelerometry-derived features. A protocol (comprising lying, sitting, standing, walking, walking up stairs, walking down stairs and transitioning between activities) was performed by 13 healthy volunteers (8 males and 5 females; age: 23.8 ± 3.7 years; weight: 70.5 ± 14.9 kg), whose instantaneous oxygen uptake was measured by means of an indirect calorimetry system (K4b(2), COSMED, Italy). Activity classification improves from 81.65% to 90.91% when including barometric pressure information; when analyzing walking activities alone the accuracy increases from 70.23% to 98.54%. Using features derived from both accelerometry and barometry signals, combined with features relating to the activity classification in a state space model, resulted in a VO(2) estimation bias of -0.00 095 and precision (1.96SD) of 3.54 ml min(-1) kg(-1). Using only accelerometry features gives a relatively worse performance, with a bias of -0.09 and precision (1.96SD) of 5.99 ml min(-1) kg(-1), with the largest errors due to an underestimation of VO(2) when walking up stairs. PMID:23110944

Wang, Jingjing; Redmond, Stephen J; Voleno, Matteo; Narayanan, Michael R; Wang, Ning; Cerutti, Sergio; Lovell, Nigel H

2012-11-01

13

The influence of barometric pressure fluctuations, earth tides and rainfall loading on fluid pressures in coastal plain aquifers, Burke County, Georgia  

Energy Technology Data Exchange (ETDEWEB)

High precision pressure measurements from several aquifers in the top 225 m of coastal plain sediments reveal that barometric pressure fluctuations, earth tides and rainfall loading create pressure fluctuations on the order of tens of centimeters. If not correctly identified, erroneous conclusions regarding the magnitude of pressure communication within and across aquifers during pumping tests may be inferred. Aquifer pressure data with an equivalent resolution of 0.1 mm change in water level were measured in 4 wells over a 10 day period at the USGS Miller's Pond Test Site. During this time, barometric pressures fluctuated by the equivalent of 20 cm of water. Aquifer pressures mimicked these changes, with corresponding barometric efficiencies ranging from 0.59 for the deepest well (215 to 224 m) to 0.73 for the shallowest (136 to 145 m). After removing barometric influences from the pressure data, periodic pressure fluctuations of 2 cm were observed. These correlate well with fluctuations in the earths gravitational field created by planetary motion. A twelve component earth tide model was used to calculate the magnitude of the gravitational fluctuations and provide a quantitative basis for comparing them to observed aquifer pressure fluctuations. Additionally, three rainfall events caused rapid and relatively large increases in aquifer pressures. Up to 4 cm increase in the aquifer pressure accompanied the heaviest rains. The pressures increased concurrent to the rains and decayed slowly to background levels over a several day period, indicating a loading response instead of an infiltration induced pressure increase. The relatively large magnitude of these influences, compared to the small changes induced by leakage across confining layers requires careful consideration in the data analysis.

Benson, S.M.; Moore, J.; Daggett, J.; Snipes, D.S. (Clemson Univ., SC (United States). Dept. of Earth Sciences)

1993-03-01

14

Evaluation of Viking Lander barometric pressure sensor. [performance related to Viking mission environments  

Science.gov (United States)

Variable reluctance type pressure sensors were evaluated to determine their performance characteristics related to Viking Mission environment levels. Static calibrations were performed throughout the evaluation over the full range of the sensors using two point contact manometer standards. From the beginning of the evaluation to the end of the evaluation, the zero shift in the two sensors was within 0.5 percent, and the sensitivity shift was 0.05 percent. The maximum thermal zero coefficient exhibited by the sensors was 0.032 percent over the temperature range of -28.89 C to 71.11 C. The evaluation results indicated that the sensors are capable of making high accuracy pressure measurements while being exposed to the conditions mentioned.

Mitchell, M.

1977-01-01

15

The Influence od Air Temperature and Barometric Pressure on Radon and Carbon Dioxide Levels in Air of a Karst Cave  

International Nuclear Information System (INIS)

Radioactive noble gas radon (222Rn) is created in minerals by radioactive transformation of 226Ra within the 238U natural decay chain. It migrates through the ground, accumulates in underground rooms (e. g., karst caves) and eventually enters the atmosphere. It is always present in our living and working environment. Because of its harmful health effect, it presents a serious social concern but is, on the other hand, a useful tool in several scientific disciplines. It is thus used as a tracer in exploring movement of air masses and an indicator of tectonic faults. Another minor constituent of air is carbon dioxide. Similar as radon, it is dangerous at high levels, but its presence in air of karst caves is indispensable for their life, because it governs speleogenetic processes. In the cave air, its concentration is determined by the inflow of outside air, biogenic activity of soil, degradation of organic matter and carbonate, degassing from water, and human activity. Therefore, ventilation of the cave is crucial for its conservation. Based on temporal variations of radon and carbon dioxide levels, ventilation regime in the cave can be estimated. Radon has been surveyed in all the twenty show caves and in thirty other caves in Slovenia, with emphasis on the Postojna Cave. In the present study, in addition to radon, monitoring of carbon dioxide was introduced for the first time. The Kostanjevica Cave, situated in southern Slovenia in an isolated island of karst, was selected because it is crossed by a tectonic fault at which measurements of three-dimensional micro displacements are underway. Because of the fault, high levels of radon and carbon dioxide were expected. In this paper, measurements are described and both the spatial and time variations of radon and carbon dioxide levels are presented and commented on. Continuous radon monitoring was carried out with the RadonScout devices (Sarad, Germany) from April to December 2009, with several interruptions because of the instrument failures. At several points along the guided tourist route, instantaneous concentrations of radon and carbon dioxide were measured monthly from August 2009 to March 2010. Outdoor air temperature and barometric pressure for the nearby meteorological station were obtained from the Office of Meteorology of the Environmental Agency of the Republic of Slovenia. Change of ventilation regime in the cave is reflected in seasonal variation of radon concentration. It is high in summer (1800 - 2200 Bq m-3) and substantially reduced in winter (20 - 500 Bq m-3), when temperature in the cave is higher than outside and radon is diluted by the inflow of outside air, caused by natural air draught. This draught is minimal or reversed in summer. Concentrations of both gases, radon and CO2, are well correlated. (author)

2011-04-13

16

Effects of Barometric Fluctuations on Well Water-Level Measurements and Aquifer Test Data  

Energy Technology Data Exchange (ETDEWEB)

The Pacific Northwest National Laboratory, as part of the Hanford Groundwater Monitoring Project, examines the potential for offsite migration of contamination within underlying aquifer systems. Well water-level elevation measurements from selected wells within these aquifer systems commonly form the basis for delineating groundwater-flow patterns (i.e., flow direction and hydraulic gradient). In addition, the analysis of water-level responses obtained in wells during hydrologic tests provides estimates of hydraulic properties that are important for evaluating groundwater-flow velocity and transport characteristics. Barometric pressure fluctuations, however, can have a discernible impact on well water-level measurements. These barometric effects may lead to erroneous indications of hydraulic head within the aquifer. Total hydraulic head (i.e., sum of the water-table elevation and the atmospheric pressure at the water-table surface) within the aquifer, not well water-level elevation, is the hydrologic parameter for determining groundwater-flow direction and hydraulic gradient conditions. Temporal variations in barometric pressure may also adversely affect well water-level responses obtained during hydrologic tests. If significant, adjustments or removal of these barometric effects from the test-response record may be required for quantitative hydraulic property determination. This report examines the effects of barometric fluctuations on well water-level measurements and evaluates adjustment and removal methods for determining areal aquifer head conditions and aquifer test analysis. Two examples of Hanford Site unconfined aquifer tests are examined that demonstrate barometric response analysis and illustrate the predictive/removal capabilities of various methods for well water-level and aquifer total head values. Good predictive/removal characteristics were demonstrated with best corrective results provided by multiple-regression deconvolution methods.

FA Spane, Jr.

1999-12-16

17

Mapping of multi-floor buildings: A barometric approach  

DEFF Research Database (Denmark)

This paper presents a new method for mapping multi5floor buildings. The method combines laser range sensor for metric mapping and barometric pressure sensor for detecting floor transitions and map segmentation. We exploit the fact that the barometric pressure is a function of the elevation, and it varies between different floors. The method is tested with a real robot in a typical indoor environment, and the results show that physically consistent multi5floor representations are achievable.

�zkil, Ali Gürcan; Fan, Zhun

2011-01-01

18

Correlation between seismicity and barometric tidal exalting  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Changes of barometric pressure in the area of Thessaloniki in Northern Greece were studied by analyzing a sample of 31 years of hourly measurements. The results of this analysis on the periodicities of tidal components are expressed in terms of amplitude and phases variability. An earlier investigation revealed a detectable correlation between the exalting of the amplitude parameters of the tidal waves with strong seismic events. A problem of this work was that we had compared the tidal param...

2008-01-01

19

Control of barometric methane emission (2)  

Energy Technology Data Exchange (ETDEWEB)

In this second part the authors examine the measures to be taken during the stemming of the shotholes and describe the difficulties which may be encountered when stemming the last open shothole (a practical example is given). States that secondary gas emission, i.e. emission from natural or artificial excavations in the strata, is not directly affected by working and heading operations. Rather, this depends to a large extent on atmospheric pressure, hence the expression barometric emission. The physical laws associated with gas emission of this type and a simple model to describe this are described.

Noack, K.

1981-10-01

20

Barometric fluctuations in wells tapping deep unconfined aquifers.  

Science.gov (United States)

Barometric effects on water levels in unconfined aquifers can be computed by solution of the differential equation governing the flow of gas in the unsaturated zone subject to the appropriate boundary conditions. Solutions to this equation for two sets of boundary conditions were applied to compute water level response in a well tapping the Ogallala Formation near Lubbock, Texas from simultaneous microbarograph records. -from Author

Weeks, E. P.

1979-01-01

 
 
 
 
21

Barometric pumping with a twist: VOC containment and remediation without boreholes  

International Nuclear Information System (INIS)

A large national cost is incurred in remediating near-surface contamination such as surface spills, leaking buried pipelines, and underground storage tank sites. Many of these sites can be contained and remediated using enhanced natural venting, capitalizing on barometric pumping. Barometric pumping is the cyclic movement experienced by soil gas due to oscillations in atmospheric pressure. Daily variations of 5 millibars are typical, while changes of 25 to 50 millibars can occur due to major weather front passage. The fluctuations can cause bulk vertical movement in soil gas ranging from centimeters to meters, depending on the amplitude of the pressure oscillation, soil gas permeability, and depth to an impermeable boundary such as the water table. Since the bulk gas movement is cyclic, under natural conditions no net advective vertical movement occurs over time. Science and Engineering Associates, Inc., is developing an engineered system to capitalize on the oscillatory flow for soil contaminant remediation and containment. By design, the system allows normal upward movement of soil gas but restricts the downward movement during barometric highs. The earth's surface is modified with a sealant and vent valve such that the soil gas flow is literally open-quotes ratchetedclose quotes to cause a net upward flow over time. A key feature of the design is that it does not require boreholes, resulting in a very low cost remediation effort and reduced personnel exposure risk. In the current phase (Phase I) the system's performance is being evaluated. Static and transient analysis results are presented which illustrate the relative magnitude of this advective movement compared to downward contaminant diffusion rates. Calculations also indicate the depth of influence for various surface and soil configurations. The system design will be presented, as well as a cost assessment compared to conventional techniques

1995-10-01

22

[A device for measuring the burning rate of light and thin homogeneous solid under low barometric pressure and in enriched oxygen].  

Science.gov (United States)

Oxygen enrichment of room air is an effective way to resist hypoxia at high altitude, but it may introduce a potential fire hazard. In common, the burning rate of light and thin homogeneous solid in oxygen enriched atmosphere was used to assess the fire hazard. For the purpose of measuring the burning rate of light and thin homogeneous solid in oxygen enriched atmosphere, we used the methods of laser contact ignition and direct calculation of burning rate, and invented a device that includes mixing gas system, ignition equipment, system of measuring the burning rate and self-made specimen frame. By using the homemade device, we studied the burning rate of filter paper under low pressure and in oxygen-enriched atmosphere and in that of the oxygen concentration of reached stationary burning rate. The results showed that this device was simple, and could obtain the burning rate of light and thin homogeneous solid quantitatively. PMID:23198421

Cheng, Haiyang; Sun, Xuechuan; Zhu, Yinhua; Deng, Weiming; Lin, Zhuo; Liu, Tao

2012-10-01

23

Passive remediation of chlorinated volatile organic compounds using barometric pumping  

International Nuclear Information System (INIS)

The purpose of the Savannah River Integrated Demonstration Program, sponsored by the Department of Energy, is to demonstrate new subsurface characterization, monitoring, and remediation technologies. The interbedded clay and sand layers at the Integrated Demonstration Site (IDS) are contaminated with chlorinated volatile organic compounds (CVOCs). Characterization studies show that the bulk of the contamination is located in the approximately 40 m thick vadose zone. The most successful strategy for removing contaminants of this type from this environment is vapor extraction alone or in combination with other methods such as air sparging or enhanced bioremediation. Preliminary work at the IDS has indicated that natural pressure differences between surface and subsurface air caused by surface barometric fluctuations can produce enough gas flow to make barometric pumping a viable method for subsurface remediation. Air flow and pressure were measured in wells that are across three stratigraphic intervals in the vadose zone' The subsurface pressures were correlated to surface pressure fluctuations but were damped and lagging in phase corresponding to depth and stratum permeability. Piezometer wells screened at lower elevations exhibited a greater phase lag and damping than wells screened at higher elevations where the pressure wave from barometric fluctuations passes through a smaller number of low permeable layers. The phase lag between surface and subsurface pressures results in significant fluxes through these wells. The resultant air flows through the subsurface impacts CVOC fate and transport. With the appropriate controls (e.g. solenoid valves) a naturally driven vapor extraction system can be implemented requiring negligible operating costs yet capable of a large CVOC removal rate (as much as 1--2 kg/day in each well at the IDS)

1993-01-01

24

Passive remediation of chlorinated volatile organic compounds using barometric pumping  

Energy Technology Data Exchange (ETDEWEB)

The purpose of the Savannah River Integrated Demonstration Program, sponsored by the Department of Energy, is to demonstrate new subsurface characterization, monitoring, and remediation technologies. The interbedded clay and sand layers at the Integrated Demonstration Site (IDS) are contaminated with chlorinated volatile organic compounds (CVOCs). Characterization studies show that the bulk of the contamination is located in the approximately 40 m thick vadose zone. The most successful strategy for removing contaminants of this type from this environment is vapor extraction alone or in combination with other methods such as air sparging or enhanced bioremediation. Preliminary work at the IDS has indicated that natural pressure differences between surface and subsurface air caused by surface barometric fluctuations can produce enough gas flow to make barometric pumping a viable method for subsurface remediation. Air flow and pressure were measured in wells that are across three stratigraphic intervals in the vadose zone` The subsurface pressures were correlated to surface pressure fluctuations but were damped and lagging in phase corresponding to depth and stratum permeability. Piezometer wells screened at lower elevations exhibited a greater phase lag and damping than wells screened at higher elevations where the pressure wave from barometric fluctuations passes through a smaller number of low permeable layers. The phase lag between surface and subsurface pressures results in significant fluxes through these wells. The resultant air flows through the subsurface impacts CVOC fate and transport. With the appropriate controls (e.g. solenoid valves) a naturally driven vapor extraction system can be implemented requiring negligible operating costs yet capable of a large CVOC removal rate (as much as 1--2 kg/day in each well at the IDS).

Rossabi, J.; Looney, B.B.; Dilek, C.A.E.; Riha, B.; Rohay, V.J.

1993-12-31

25

Field measurements of tracer gas transport by barometric pumping  

International Nuclear Information System (INIS)

Vertical gas motions induced by barometric pressure variations can carry radioactive gases out of the rubblized region produced by an underground nuclear explosion, through overburden rock, into the atmosphere. To better quantify transit time and amount of transport, field experiments were conducted at two sites on Pahute Mesa, Kapelli and Tierra, where radioactive gases had been earlier detected in surface cracks. At each site, two tracer gases were injected into the rubblized chimney 300-400 m beneath the surface and their arrival was monitored by concentration measurements in gas samples extracted from shallow collection holes. The first ''active'' tracer was driven by a large quantity of injected air; the second ''passive'' tracer was introduced with minimal gas drive to observe the natural transport by barometric pumping. Kapelli was injected in the fall of 1990, followed by Tierra in the fall of 1991. Data was collected at both sites through the summer of 1993. At both sites, no surface arrival of tracer was observed during the active phase of the experiment despite the injection of several million cubic feet of air, suggesting that cavity pressurization is likely to induce horizontal transport along high permeability layers rather than vertical transport to the surface. In contrast, the vertical pressure gradients associated with barometric pumping brought both tracers to the surface in comparable concentrations within three months at Kapelli, whereas 15 months elapsed before surface arrival at Tierra. At Kapelli, a quasisteady pumping regime was established, with tracer concentrations in effluent gases 1000 times smaller than concentrations thought to exist in the chimney. Tracer concentrations observed at Tierra were typically an order of magnitude smaller. Comparisons with theoretical calculations suggest that the gases are traveling through ?1 millimeter vertical fractures spaced 2 to 4 meters apart. 6 refs., 18 figs., 3 tabs

1994-01-01

26

Barometric pumping of a fractured porous medium  

Science.gov (United States)

Fluctuations in the ambient atmospheric pressure result in motion of air in porous and fractured media. This mechanism, known as barometric (or atmospheric) pumping, efficiently transports gaseous species through the vadose zone to the atmosphere. This is of interest in many environmental and engineering fields, such as transport of trace gases from soil to atmosphere, environmental remediation of contaminated sites, radon in buildings and last but not least detection of nuclear explosions or leakage from carbon sequestration sites. The physical situation has been addressed in the following way. The fractures are modeled as polygonal plane surfaces with a given transmissivity embedded in a porous medium with a given permeability. The fluid is slightly compressible and is assumed to obey Darcy's law in the fractures and the porous medium with exchanges between them. The solute obeys convection-diffusion equations in both media again with exchanges between them. The fractures and the porous medium located in between them are meshed by triangles and tetrahedra. The equations are discretized by the finite volume method. In order to improve numerical precision, a Flux Limiting Scheme is applied to the transport equations ; moreover, special care is devoted to the description of the solute transfer between the fractures and the porous medium. The resulting equations are solved by conjugate gradient algorithms. This model is applied to the Roselend Natural Laboratory. At a 55 m depth, a sealed cavity allows for gas release experiments across fractured porous rocks in the unsaturated zone. The fractures are hexagons with a radius of 5m; their density is larger than 2.4 10-3 m-3; the aperture is of the order of 0.5 mm. The pressure fluctuations are sinusoidal, of amplitude 0.01 bar and period 1 week. The solute concentration is supposed to be equal to 1 at the bottom of the site. Systematic results will be presented. First, the precision of the calculations is assessed. Second, the pressure fluctuations and the solute concentration in the fractured porous medium is displayed and discussed. Third, the influence of the major parameters (fracture density and aperture, porosity, diffusion coefficient,…) is illustrated and discussed. These results are discussed in terms of the amplification of solute transfer to the ground surface by the pressure fluctuations. Finally, it should be emphasized that the codes can be easily modified to address time dependent thermal transfers in fractured porous media.

Adler, Pierre; Varloteaux, Clément; Mourzenko, Valeri; François Thovert, Jean; Guillon, Sophie; Pili, Eric

2014-05-01

27

Pressure balance under hydrothermal conditions  

Science.gov (United States)

Low pressure, low temperature growth of potassium titanyl phosphate (KTP) crystals, the material of choice for certain kinds of laser eye surgery apparatus and other applications, requires hydrothermal growth in pressure balance noble metal cans. This paper discusses the problem of pressure balancing the Au cans used for hydrothermal KTP growth. The P-V-T behavior of the pressure balance medium (H2O) and the growth medium (KTP saturated K2HPO4) are described and the source of the 'dimples' in growth cans is explained and remediation strategies are suggested.

Laudise, R. A.; Bridenbaugh, P. M.; Iradi, T.

1994-06-01

28

A Graphical Method for Estimation of Barometric Efficiency from Continuous Data - Concepts and Application to a Site in the Piedmont, Air Force Plant 6, Marietta, Georgia  

Science.gov (United States)

A graphical method that uses continuous water-level and barometric-pressure data was developed to estimate barometric efficiency. A plot of nearly continuous water level (on the y-axis), as a function of nearly continuous barometric pressure (on the x-axis), will plot as a line curved into a series of connected elliptical loops. Each loop represents a barometric-pressure fluctuation. The negative of the slope of the major axis of an elliptical loop will be the ratio of water-level change to barometric-pressure change, which is the sum of the barometric efficiency plus the error. The negative of the slope of the preferred orientation of many elliptical loops is an estimate of the barometric efficiency. The slope of the preferred orientation of many elliptical loops is approximately the median of the slopes of the major axes of the elliptical loops. If water-level change that is not caused by barometric-pressure change does not correlate with barometric-pressure change, the probability that the error will be greater than zero will be the same as the probability that it will be less than zero. As a result, the negative of the median of the slopes for many loops will be close to the barometric efficiency. The graphical method provided a rapid assessment of whether a well was affected by barometric-pressure change and also provided a rapid estimate of barometric efficiency. The graphical method was used to assess which wells at Air Force Plant 6, Marietta, Georgia, had water levels affected by barometric-pressure changes during a 2003 constant-discharge aquifer test. The graphical method was also used to estimate barometric efficiency. Barometric-efficiency estimates from the graphical method were compared to those of four other methods: average of ratios, median of ratios, Clark, and slope. The two methods (the graphical and median-of-ratios methods) that used the median values of water-level change divided by barometric-pressure change appeared to be most resistant to error caused by barometric-pressure-independent water-level change. The graphical method was particularly resistant to large amounts of barometric-pressure-independent water-level change, having an average and standard deviation of error for control wells that was less than one-quarter that of the other four methods. When using the graphical method, it is advisable that more than one person select the slope or that the same person fits the same data several times to minimize the effect of subjectivity. Also, a long study period should be used (at least 60 days) to ensure that loops affected by large amounts of barometric-pressure-independent water-level change do not significantly contribute to error in the barometric-efficiency estimate.

Gonthier, Gerard J.

2007-01-01

29

An Educational Study of the Barometric Effect of Cosmic Rays with a Geiger Counter  

Science.gov (United States)

An educational study of the barometric effect of cosmic rays was carried out using an inexpensive experimental set-up that allowed for long-term monitoring of atmospheric pressure and cosmic ray flux as measured in a Geiger counter. The investigation was intended as a pilot study in view of ongoing involvements of high-school teams operating…

Famoso, Barbara; La Rocca, Paola; Riggi, Francesco

2005-01-01

30

Pressure conditioning system for containment vessel  

International Nuclear Information System (INIS)

Purpose: To simplify the equipments in a reactor container by using existent pipelines passing through the container also as pressure release pipelines, as well as decrease the possibility of radioactive gas leakage by decreasing the number of pipelines passing through the container. Constitution: In a pressure conditioning system for controlling the inner pressure of a reactor container by substantially equalizing the inner and the outer pressure of the container, the pressure release pipelines for the pressure conditioning systems are connected and integrated with the existent pipelines passing through the container. As for the existent pipelines, the pipelines for a container spray system or vacuum destruction system can be used. The integration of the pipelines passing through the container enables to simplify the equipments in the container and decrease the danger of gas leakage. (Horiuchi, T.)

1981-01-01

31

Harmonic response of soil radon-222 flux and concentration induced by barometric oscillations  

Science.gov (United States)

Radon-222 flux and concentration in the soil are sensitive to changes in atmospheric pressure, and in particular to periodic signals, such as the semi-diurnal barometric tide S2. The response of radon flux and concentration to barometric oscillations is calculated analytically for all harmonic degrees in the case of a horizontal layer over a half-space, representing the situation of a soil layer over homogeneous bedrock, taking into account air and water phases and the presence of static vertical advection. The calculations show that the presence of an interface changes dramatically the response to barometric oscillations. Large amplitudes at the forcing frequency (fundamental) are concentrated in the vicinity of the interface, while amplitudes remain negligible at the same depth in a homogeneous half-space. A significant negative phase shift in the surface radon flux is introduced when a shallow interface is present, while radon flux is almost in phase opposition with atmospheric pressure over a homogeneous half-space. While, in most situations, the amplitudes are small and difficult to detect, situations can be exhibited where the amplitudes of harmonics 2 and 3 of radon concentration are larger than 100 Bq m-3, leading, for example, to possible detection of 4-hr peaks in the radon power spectra due to barometric tide S2. Optimal position of the radon sensors appears to be a few centimetres in the bedrock below the soil. Amplitudes of radon concentration and surface flux are sensitive to underlying bedrock permeability, porosity, water saturation and effective radium concentration, and depend also on the presence of advection. At large carrier gas velocities, a more precise calculation valid for multilayered media, is presented, which can be used in volcanic and hydrothermal areas. While the amplitudes of all harmonics for radon concentration in the soil become negligible, the fundamental in radon surface flux reaches a constant and, possibly, observable value dominated by the parameters of the deepest medium. A better knowledge of the response of radon flux and concentration to barometric oscillations is important to interpret the presence or absence of peaks in the power spectra of radon time-series collected for environmental and geodynamical purposes. This study provides further support to the relevance of long-term radon monitoring to constrain the transport properties of the subsurface.

Perrier, Frédéric; Girault, Frédéric

2013-11-01

32

Experimental exposure of rats to methylene chloride at varying controlled barometric altitudes  

Energy Technology Data Exchange (ETDEWEB)

This study investigated combined effects of three methylene chloride (MC) volume/volume concentrations (0,50, and 500 ppm) at three controlled barometric altitudes (760, 640, and 560 torr). This provided a three by three study design. For each scenario, three altitude acclimated (6 days) adult male rats were studied for eight hours in a nose-only inhalation chamber. Blood (0.35 mL) was drawn from the cannulated left carotid artery of each rat at 0, 0.5, 1, 2, 4, and 8 hours and hematocrit, pO[sub 2], pCO[sub 2], pH , total hemoglobin (Hb) and carboxyhemoglobin (CHb) were measured. Time, MC concentration and altitude had significant effects on CHb production. CHb increased with increasing MC concentration over time. Increased barometric altitude (reduced partial pressure of MC vapor at altitude for equal ppm concentrations) resulted in lower blood CHb levels. A statistical model was derived to explain variation in CHb levels for these three independent variables (r = 0.983). The data were applied to an equation assessing the impact of altitude, MC concentration and time on the potential oxygen carrying capacity (POCC) of blood. The POCC of HB in the blood was calculated using blood Hb, CHb levels, Hb oxygen saturation (based on the blood pO[sub 2] and the oxygen dissociation curve for rats), and oxygen binding potential of Hb. It was determined for the altitudes and MC concentrations used, polycythemia associated with increased altitude had a greater impact on POCC than decreased pO[sub 2]. A regression equation was derived modeling variation in POCC of blood for the three independent variables (r = 0.995). This study demonstrated that altitude affects airborne ppm MC concentrations. This ultimately impacts CHb levels and oxygen carrying capacity of the blood. These finding indicate that occupationally acceptable ppm MC exposure levels at altitude do need barometric pressure correction.

Lillquist, D.R.

1990-01-01

33

Variation of the barometric coefficient during a solarcycle NM64 Utrecht, 1969-1978; cut-off rigidity 2.7 GV  

International Nuclear Information System (INIS)

More reliable estimates for the barometric coefficient are obtained by applying a moving average model to 12 hourly sums of intensity and pressure data with a statistically optimal period length of 2 months. Plotting coefficients against corrected intensities large hysteresis loops show up. Clockwise or anti-clockwise directions seem to be connected to the polarity of the Solar Polar Fields

1981-07-25

34

Barometric tides from ECMWF operational analyses  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The solar diurnal and semidiurnal tidal oscillations in surface pressure are extracted from the operational analysis product of the European Centre for Medium Range Weather Forecasting (ECMWF). For the semidiurnal tide this involves a special temporal interpolation, following Van den Dool et al. (1997). The resulting tides are compared with a "ground truth" tide data set, a compilation of well-determined tide estimates deduced from many long time series of station barometer measurements. Thes...

Ray, R. D.; Ponte, R. M.

2003-01-01

35

Barometric tides from ECMWF operational analyses  

Directory of Open Access Journals (Sweden)

Full Text Available The solar diurnal and semidiurnal tidal oscillations in surface pressure are extracted from the operational analysis product of the European Centre for Medium Range Weather Forecasting (ECMWF. For the semidiurnal tide this involves a special temporal interpolation, following Van den Dool et al. (1997. The resulting tides are compared with a "ground truth" tide data set, a compilation of well-determined tide estimates deduced from many long time series of station barometer measurements. These comparisons show that the ECMWF (analysis tides are significantly more accurate than the tides deduced from two other widely available reanalysis products. Spectral analysis of ECMWF pressure series shows that the tides consist of sharp central peaks with modulating sidelines at integer multiples of 1 cycle/year, superimposed on a broad cusp of stochastic energy. The integrated energy in the cusp dominates that of the side-lines. This complicates the development of a simple empirical model that can characterize the full temporal variability of the tides.

Key words. Meteorology and atmospheric dynamics (waves and tides

R. D. Ray

36

Sealing of rotary drums for operation under pressurized conditions  

International Nuclear Information System (INIS)

In practice, rotary drums are always designed for operation under vacuum conditions. In this paper, a novel technique is proposed for sealing the rotary drums under pressurized conditions. The proposed system is based on applying a secondary pressurized volume around the leaking gap of the drum. By controlling the pressure of this volume above the pressure of the drum, it will be possible to prevent from any leakage of gases to the ambient. The objective of a controller in this system is that the pressure of secondary volume be kept above the pressure of the drum in spite of the disturbances which may be exerted on the system by the wind outside the drum. The control system is also required to trace the variations in the drum pressure with the least fluctuations in the pressure difference among the drum and the volume

2006-11-01

37

Initial condition effect on pressure waves in an axisymmetric jet  

Science.gov (United States)

A pair of microphones (separated axially by 5.08 cm and laterally by 1.3 cm) are placed on either side of the jet centerline to investigate coherent pressure fluctuations in an axisymmetric jet at Strouhal numbers less than unity. Auto-spectra, transfer-function, and coherence measurements are made for a tripped and untripped boundary layer initial condition. It was found that coherent acoustic pressure waves originating in the upstream plenum chamber propagate a greater distance downstream for the tripped initial condition than for the untripped initial condition. In addition, for the untripped initial condition the development of the coherent hydrodynamic pressure waves shifts downstream.

Miles, Jeffrey H.; Raman, Ganesh

1988-01-01

38

Initial conditional effect on pressure waves in an axisymmetric jet  

Science.gov (United States)

A pair of microphones (separated axially by 5.08 cm and laterally by 1.3 cm) are placed on either side of the jet centerline to investigate coherent pressure fluctuations in an axisymmetric jet at Strouhal numbers less than unity. Auto-spectra, transfer-function, and coherence measurements are made for a tripped and untripped boundary layer initial condition. It was found that coherent acoustic pressure waves originating in the upstream plenum chamber propagate a greater distance downstream for the tripped initial condition than for the untripped initial condition. In addition, for the untripped initial condition the developmet of the coherent hydrodynamic pressure waves shifts downstream.

Miles, Jeffrey H.; Raman, Ganesh

1988-01-01

39

Magnetohydrodynamic Jump Conditions for Oblique Relativistic Shocks with Gyrotropic Pressure  

CERN Multimedia

Shock jump conditions are obtained for steady-state, plane shocks with oblique magnetic fields and arbitrary flow speeds. For ultrarelativistic and nonrelativistic shocks, the jump conditions may be solved analytically. For mildly relativistic shocks, analytic solutions are obtained for isotropic pressure using an approximation for the adiabatic index that is valid in high sonic Mach number cases. In the more general case of gyrotropic pressure, the jump conditions cannot be solved analytically without additional assumptions, and the effects of gyrotropic pressure are investigated by parameterizing the distribution of pressure parallel and perpendicular to the magnetic field. Our numerical solutions reveal that relatively small departures from isotropy (e.g., about 20%) produce significant changes in the shock compression ratio, r, at all shock Lorentz factors, including ultrarelativistic ones, where an analytic solution with gyrotropic pressure is obtained. In particular, either dynamically important fields ...

Double, G P; Jones, F C; Ellison, D C; Double, Glen P.; Baring, Matthew G.; Jones, Frank C.; Ellison, Donald C.

2004-01-01

40

Effects of the imposed pressure differential conditions on duoplasmatron performance  

International Nuclear Information System (INIS)

The duoplasmatron plasma source (D.P.T.) was modified to allow access to the arc discharge (to measure the discharge properties) and to vary independently the pressures in different volumes of the arc with the aim of seeing if this freedom would help in optimising the output. The duoplasmatron plasma source was operated under normal running condition (N.R.C.), positive imposed pressure differential condition (P.I.P.D.C.) and negative imposed pressure differential condition (N.I.P.D.C.) and the corresponding properties of the plasma output were measured. Running the duoplasmatron under P.I.P.D. condition did not seem to improve the output as compared to that under N.R.C. However, running the duoplasmatron under N.I.P.D. condition seemed to be advantageous as the output increased by about 30%. It was observed that the back pressure was critical in maintaining the arc and the gap pressure could be lowered much below the normal minimum (while the arc was on) if back pressure was kept above a critical value. The results showed that the effects of varying the dimensions of the intermediate electrode nozzle on the output could be understood in terms of the effect of changes in these dimensions on the relative pressures. An empirical expression for the effect of the pressure ratio was developed from the observations and compared with the experimental results. The reasons for various results can be related to the plasma emission mechanism. (author). 8 refs, 6 figs, 1 tab

1987-06-19

 
 
 
 
41

Pyrolysis and gasification behavior of black liquor under pressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study has been to enhance the understanding of the processes involved in pressurized black liquor gasification. Gasification is known to occur in three stages: drying, pyrolysis and char gasification. The work presented here focuses on the pyrolysis and gasification stages. Experiments were carried out primarily in two laboratory-scale reactors. A pressurized grid heater was used to study black liquor pyrolysis under pressurized conditions. Char yields and the fate of elements in the liquor, as well as the degree of liquor swelling, were measured in this device. A pressurized thermogravimetric reactor was used to measure the rate of the char gasification process under different temperatures and pressures and in various gas atmospheres. Pyrolysis experiments were also carried out in this device, and data on swelling behavior, char yields and component release were obtained 317 refs.

Whitty, K.

1997-11-01

42

Sources of corrosive conditions in low pressure steam turbines  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this paper is to provide a brief review of those aspects of power plant circuit chemistry that can lead to the formation of corrosive conditions in low-pressure steam turbines. The topic has received considerable attention in the recent past, and there has been a major review of turbine steam path damage from EPRI.

Bignold, G.J. [National Power, London (United Kingdom)

2000-09-01

43

Investigations on pressure suppression system loads at accident conditions  

International Nuclear Information System (INIS)

For simulation of the integral behavior of pressure suppresion systems at accident conditions a mathematical model was developed which simulates a wide range of the loads occurring during a loss-of coolant accident. The multi-zone point model DRASYS serves for mathematical simulation of quasistatic (pressure and temperature build-up in the dry well and the suppression chamber) as well as dynamic loads (free-blowing process, water throw-up and condensing oscillations) in the course of a loss-of-coolant accident. For determination of the state variations with time in the individual pressure sections thermodynamic equilibrium is assumed between steam and water phases. Thermal non-equilibrium states are taken into account if phase separation interfaces between water and steam/air mixture exist. The flows between the individual pressure sections are treated as homogeneous, nonsteady, incompressible flows. For verification of the mathematical model recalculations were made of experiments performed at various test stands. Teh recalculations showed that the mathematical model has got a wide range of application and is suited for design and assessment of pressure suppression systems at accident conditions. (orig.)

1979-01-01

44

Characterization of solid fuels at pressurized fluidized bed gasification conditions  

Energy Technology Data Exchange (ETDEWEB)

The gasification of co-gasification of solid fuel (coal, peat, wood) in air-blown fluidized bed gasifiers is receiving continued attention as an alternative to entrained flow gasifiers which in general are oxygen-blown. Fluidized bed gasification of wood and wood-waste at elevated pressures, and the so-called air-blown gasification cycle are examples of processes which are under development in Europe. based on complete or partial gasification of a solid fuel in a pressurized fluidized bed. At the same time, fuel characterization data for the combination of temperature, pressure and fuel particle heating rate that is encountered in fluidized bed gasification are very scarce. In this paper, quantitative data on the characterization of fuels for advanced combustion and gasification technologies based on fluidized beds are given, as a result from the authors participation in the JOULE 2 extension project on clean coal technology of the European community. Eleven solid fuels, ranging from coal via peat to wood, have been studied under typical fluidized bed gasification conditions: 800--1,000 C, 1--25 bar, fuel heating rate in the order of 100--1,000 C/s. Carbon dioxide was used as gasifying agent. A pressurized thermogravimetric reactor was used for the experiments. The results show that the solid residue yield after pyrolysis/devolatilization increases with pressure and decreases with temperature. For coal, the gasification reactivity of the char increases by a factor of 3 to 4 when pressurizing from 1 to 25 bar, for the younger fuels such as peat and wood, this effect is negligible. Several empirical engineering equations are given which relate the fuel performance to the process parameters and the proximate and chemical analyses of the fuel. A pressure maximum was found at which a maximum gasification reactivity occurs, for practically all fuels, and depending on temperature. It is shown that this can be explained and modeled using a Langmuir-Hinshelwood model.

Zevenhoven, R.; Hupa, M.

1998-07-01

45

Modeling of Spray Combustion under Cryogenic and High Pressure Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper concerns both the numerical and experimental investigation of turbulent liquid oxygen/hydrogen spray combustion for elevated subcritical pressure and cryogenic inlet temperature conditions. In particular, the combustion in the single injector combustion chamber is studied where experimental data are obtained for gas phase temperature and both droplet size and velocities. The model uses an Eulerian--Lagrangian formulation for the gas and the liquid phase, respectively. Detailed ...

Schlotz, D.; Vogelgesang, M.; Gutheil, E.; Clauss, W.; Sender, J.

2005-01-01

46

Centrifuge measurements of capillary pressure. Part 1; Outflow boundary condition  

Energy Technology Data Exchange (ETDEWEB)

In this paper the capillary pressure curve is estimated from centrifuge measurements with the assumption that P{sub c} = 0 at the outflow end of the core. With the proper end piece to support the core sample, this boundary condition is valid in practically all circumstances. If the end piece is wetted by the produced liquid, however, experiments show that the capillary pressure curve is altered significantly. Theoretical analysis demonstrates that film drainage can displace the zero-capillary-pressure boundary condition to the bottom of the end piece or farther. Accordingly, the authors recommend that the displaced phase not wet the end piece; in the case of water, a teflon end piece is recommended over the commonly used rubber one. When the end piece is not a problem, the condition for 100% liquid saturation at the outflow face can be expressed as a critical Bond number, which is rarely exceeded. Saturation profiles for an experiment just below the critical Bond number were in excellent agreement with predictions.

O' Meara, D.J. Jr.; Hirasaki, G.J.; Rohan, J.A. (Shell Development Co. (US))

1992-02-01

47

Material dynamics under extreme conditions of pressure and strain rate  

Energy Technology Data Exchange (ETDEWEB)

Solid state experiments at extreme pressures (10-100 GPa) and strain rates ({approx}10{sup 6}-10{sup 8}s{sup -1}) are being developed on high-energy laser facilities, and offer the possibility for exploring new regimes of materials science. These extreme solid-state conditions can be accessed with either shock loading or with a quasi-isentropic ramped pressure drive. Velocity interferometer measurements establish the high pressure conditions. Constitutive models for solid-state strength under these conditions are tested by comparing 2D continuum simulations with experiments measuring perturbation growth due to the Rayleigh-Taylor instability in solid-state samples. Lattice compression, phase, and temperature are deduced from extended x-ray absorption fine structure (EXAFS) measurements, from which the shock-induced {alpha}-{omega} phase transition in Ti and the {alpha}-{var_epsilon} phase transition in Fe are inferred to occur on sub-nanosec time scales. Time resolved lattice response and phase can also be measured with dynamic x-ray diffraction measurements, where the elastic-plastic (1D-3D) lattice relaxation in shocked Cu is shown to occur promptly (< 1 ns). Subsequent large-scale molecular dynamics (MD) simulations elucidate the microscopic dynamics that underlie the 3D lattice relaxation. Deformation mechanisms are identified by examining the residual microstructure in recovered samples. The slip-twinning threshold in single-crystal Cu shocked along the [001] direction is shown to occur at shock strengths of {approx}20 GPa, whereas the corresponding transition for Cu shocked along the [134] direction occurs at higher shock strengths. This slip-twinning threshold also depends on the stacking fault energy (SFE), being lower for low SFE materials. Designs have been developed for achieving much higher pressures, P > 1000 GPa, in the solid state on the National Ignition Facility (NIF) laser.

Remington, B A; Allen, P; Bringa, E; Hawreliak, J; Ho, D; Lorenz, K T; Lorenzana, H; Meyers, M A; Pollaine, S W; Rosolankova, K; Sadik, B; Schneider, M S; Swift, D; Wark, J; Yaakobi, B

2005-09-06

48

A multigrid fluid pressure solver handling separating solid boundary conditions.  

Science.gov (United States)

We present a multigrid method for solving the linear complementarity problem (LCP) resulting from discretizing the Poisson equation subject to separating solid boundary conditions in an Eulerian liquid simulation’s pressure projection step. The method requires only a few small changes to a multigrid solver for linear systems. Our generalized solver is fast enough to handle 3D liquid simulations with separating boundary conditions in practical domain sizes. Previous methods could only handle relatively small 2D domains in reasonable time, because they used expensive quadratic programming (QP) solvers. We demonstrate our technique in several practical scenarios, including nonaxis-aligned containers and moving solids in which the omission of separating boundary conditions results in disturbing artifacts of liquid sticking to solids. Our measurements show, that the convergence rate of our LCP solver is close to that of a standard multigrid solver. PMID:22411885

Chentanez, Nuttapong; Müller-Fischer, Matthias

2012-08-01

49

Deviation from LTE conditions in high pressure mercury discharge lamps  

Energy Technology Data Exchange (ETDEWEB)

Up to now the positive column of high light sources have been investigated mainly as a system in local thermodynamic equilibrium (LTE). Recent measurements in mercury arcs suggest the existence of departures from equilibrium in the axis and in the periphery in such an arc. The deviation from equilibrium leads to complicated distributions such that the plasma cannot be described by a single temperature. In these conditions, the only practical way of investigations is the direct the measurements of the neutral atom densities. In a recent paper the authors have proposed a method allowing the determination of the ground state density in a high pressure mercury discharge from the broadening of the red wing of the 253.7 nm self reversed resonance line. This method, which does not require the LTE assumption, has proved to be very convenient for measuring the ground state density in a wide range of pressure (from 0.2 to 5 bar in the authors` case). From spatially resolved line intensity measurements, local densities are inferred by Abel inversion. The experiment was described previously. Mercury discharge lamps, having the same internal diameter (18.2 mm) and inter-electrode distance (72 mm), operated vertically through a current invertor (current equal to 3.2 A). In the present work the authors investigate the same range of pressure as in Ref. 1. They compare the experimental results by those calculated using a two temperature model. The opportunity to compare such densities gave as a lot of additional information. Therefore, the results are interpreted in term of non equilibrium. Results for the lowest pressure (0.2 bar) show that the discrepancy are very pronounced in the arc core and in the periphery of the discharge (the axial density is 0.25 {times} 10{sup 18} cm{sup {minus}3}), while the departure from equilibrium becomes insignificant for high pressure (the axial density is 6.5 {times} 10{sup 18} cm{sup {minus}3}).

Elloumi, H.; Zissis, G. [Centre de Physique des Plasmas et de Leurs Applications, Toulouse (France); Charrada, K. [ESSTT, Tunis (Tunisia)

1998-12-31

50

Barometric pumping with a twist: VOC containment and remediation without boreholes. Phase I  

Energy Technology Data Exchange (ETDEWEB)

The majority of the planned remediation sites within the DOE complex are contaminated with volatile organic compounds (VOCs). In many instances the contamination has not reached the water table, does not pose an immediate threat, and is not considered a high priority problem. These sites will ultimately require remediation of some type, either by active vapor extraction, bioremediation, or excavation and ex-situ soil treatment. The cost of remediating these sites can range from $50 K to more than $150 K, depending on site characteristics, contaminants, and remediation method. Additionally, for many remediated sites, residual contamination exists which could not practically be removed by the applied remediation technology. These circumstances result in modest sites with contamination of limited risk, but by regulation they must still be controlled. A remediation solution being developed by Science and Engineering Associates, Inc. (SEA) for the Department of Energy serves as an in-situ containment and extraction methodology for sites where most or all of the contamination resides in the vadose zone soil. The approach capitalizes on the advective soil gas movement resulting from barometric pressure oscillations.

NONE

1996-08-01

51

Micromachined capacitive pressure sensor with signal conditioning electronics  

DEFF Research Database (Denmark)

Micromachined capacitive pressure sensors for harsh environment together with interfacing electronic circuits have been studied in this project. Micro-electromechanical systems (MEMS) have been proposed as substitutes for macro scale sensorâ??s systems in many different fields and are the only possible solution in many cases where, for example, the dimensions of the sensing element is the limiting factor. Furthermore, MEMS can significantly reduce costs and power consumption being the best candidate for consumer electronics such as mobile phones and cameras, or for the automotive industry where a great deal of sensors are used. Pressure sensors are among the most successful MEMS and are used in a huge variety of applications. In this project an absolute capacitive pressure sensor has been developed with the aim to integrate it in pump control systems to improve the efficiency of the pump. The developed MEMS consist of hermetically sealed vacuum cavities surrounded by two heavily doped silicon layers which constitute the plates of a capacitor. The top plate is also the sensing element being a thin diaphragm that deflects when pressure is applied, thus increasing the capacitance (i.e. the output signal) of the device. Fusion bonding of two wafers has been used in order to obtain the cavities, this is also the only non-standard cleanroom process involved in the fabrication of the transducers. The device developed can measure absolute pressures from 0 to 10 bar with sensitivity up to 80 pF/bar. As a part of the project a suitable interfacing circuit has been developed. Different solutions have been studied in order to optimize size, costs, sensitivity and stability. A comparative analysis between them has been carried out and suggestion for the final product has been proposed. Both the electronic conditioning circuits and the MEMS have been fully described with mathematical models and simulated with electrical networks software for the circuit part and finite element for the sensor part. A good matching between analytical models and simulations results has been achieved. Furthermore, the experimental results are in good agreement with the models proposed. Finally a demonstrator has been fabricated under the constraints of a previously designed case in order to contain costs; modification or re-design of the packaging is in fact one of the major costs for the MEMS industry. This demonstrator has been characterized and presented at Grundfos Direct Sensors A/S and constitute the preliminary work for a new product which is intended target the low power or wireless pressure sensor for harsh environment market.

Fragiacomo, Giulio

2012-01-01

52

Evaluating road surface conditions using dynamic tire pressure sensor  

Science.gov (United States)

In order to best prioritize road maintenance, the level of deterioration must be known for all roads in a city's network. Pavement Condition Index (PCI) and International Roughness Index (IRI) are two standard methods for obtaining this information. However, IRI is substantially easier to measure. Significant time and money could be saved if a method were developed to estimate PCI from IRI. This research introduces a new method to estimate IRI and correlate IRI with PCI. A vehicle-mounted dynamic tire pressure sensor (DTPS) system is used. The DTPS measures the signals generated from the tire/road interaction while driving. The tire/road interaction excites surface waves that travel through the road. DTPS, which is mounted on the tire's valve stem, measures tire/road interaction by analyzing the pressure change inside the tire due to the road vibration, road geometry and tire wall vibration. The road conditions are sensible to sensors in a similar way to human beings in a car. When driving on a smooth road, tire pressure stays almost constant and there are minimal changes in the DTPS data. When driving on a rough road, DTPS data changes drastically. IRI is estimated from the reconstructed road profile using DTPS data. In order to correlate IRI with PCI, field tests were conducted on roads with known PCI values in the city of Brockton, MA. Results show a high correlation between the estimated IRI values and the known PCI values, which suggests that DTPS-based IRI can provide accurate predictions of PCI.

Zhao, Yubo; Wu, H. Felix; McDaniel, J. Gregory; Wang, Ming L.

2014-03-01

53

PRESSURE INTEGRITY OF 3013 CONTAINER UNDER POSTULATED ACCIDENT CONDITIONS  

Energy Technology Data Exchange (ETDEWEB)

A series of tests was carried out to determine the threshold for deflagration-to-detonation transition (DDT), structural loading, and structural response of the Department of Energy 3013 storage systems for the case of an accidental explosion of evolved gas within the storage containers. Three experimental fixtures were used to examine the various issues and three mixtures consisting of either stoichiometric hydrogen-oxygen, stoichiometric hydrogen-oxygen with added nitrogen, or stoichiometric hydrogen-oxygen with an added nitrogen-helium mixture were tested. Tests were carried out as a function of initial pressure from 1 to 3.5 bar and initial temperature from room temperature to 150 C. The elevated temperature tests resulted in a slight increase in the threshold pressure for DDT. The elevated temperature tests were performed to ensure the test results were bounding. Because the change was not significant the elevated temperature data are not presented in the paper. The explosions were initiated with either a small spark or a hot surface. Based on the results of these tests under the conditions investigated, it can be concluded that DDT of a stoichiometric hydrogen-oxygen mixture (and mixtures diluted with nitrogen and helium) within the 3013 containment system does not pose a threat to the structural integrity of the outer container.

Rawls, G.

2010-02-01

54

Critical heat flux at low velocity and pressure conditions  

International Nuclear Information System (INIS)

The purpose of this study is to provide some systematic understanding on critical heat flux (CHF) at low velocity and pressure conditions in which the effects of gravity and flow instability are remarkable. Experimental data obtained previously for water in an annulus, rectangular ducts and a round tube are briefly reviewed and augmented in collaboration with existing data and correlations to extract more generic information. The effect of channel geometry is then discussed. The effect of channel geometry turned out to be significant at intermediate mass velocities. The difference in CHF at these mass velocities between a round tube and the other channel geometries was attributed mainly to the existence of unheated wall which causes a nonuniform distribution of liquid film. (author)

1986-01-01

55

Critical heat flux at low pressure and low velocity conditions  

International Nuclear Information System (INIS)

Critical heat flux(CHF) at low pressure and low velocity conditions is important in relation to the design of passive safety reactors, research reactors and district heating reactors as well as accident analyses of commercial nuclear reactors. However, experimental data and design correlations are scarce and physical mechanisms are not well known. KAIST is studying this subject through experiments, theoretical modeling and correlation development. This paper describes the results of the first-phase work. It includes a brief literature survey, introduction of KAIST experimental loop, discussion on the experimental results with a 6mm-ID and 0.685m-long vertical round tube, postulation of physical mechanisms, and suggestion of design correlations

1990-05-25

56

Behaviour of concrete containment under over-pressure conditions  

International Nuclear Information System (INIS)

The Atomic Energy Control Board of Canada initiated June, 1975, a major study of the behaviour of concrete containment under over-pressure conditions. Although extensive theoretical and experimental work has been carried out for thick-walled Prestressed Concrete Reactor Vessels (PCRV's), there is a want of information on the non-linear response of thin-walled structures typical of the CANDU, 600 MW(e) cylindrical/spherical, post-tensioned containment shells. The purpose of this paper is to provide an overview of the total program, to present the reasons behind the research contract, and the specification and implementation of the work. The results of the theoretical and experimental work and their implications with respect to Canadian Concrete Containment practice are discussed. This study is unique, and, as far as is known, has no world-wide precedence. (orig.)

1979-08-21

57

PDHT-LP, Low Pressure Post Dryout Loop, Upflow Conditions  

International Nuclear Information System (INIS)

1 - Description of test facility: Water was heated to the desired temperature via a preheater with the flow monitored by turbine flow meters. The vertically mounted test section consisted of a 920 mm long Nimonic 75 tube, 9.85 mm ID and 14.0 mm OD, which was surrounded by five concentric layers of polished nickel and 50 mm of insulation to act as a heat shield and minimise heat losses. Two 36 mm thick nickel-plated copper blocks were brazed to either end of the heated length, which acted as the hot patches. The position of the dry-out front was maintained upstream of the test section by heat transfer from the hot patches, which were instrumented with thermocouples to enable the heat fluxes to be evaluated, although only up-flow tests (using the lower hot patch) were performed in this facility. The test section itself had a total of 39 thermocouples attached to the outer surface. 2 - Description of tests: Both the 0.2 Mpa and 0.4 Mpa test series were performed at the same set of flow rates; 25, 50, 100 and 150 kg/m2s. For the 0.2 Mpa test series, inlet subcooling was varied over 21 - 46167 C, whereas for the 0.4 Mpa test series, inlet subcooling was varied over 28 - 50 deg. C. 3 - Experimental limitations or shortcomings: Low pressures only suitable for Large Break LOCA conditions. Up-flow test data only

1998-01-01

58

Touch mode micromachined capacitive pressure sensor with signal conditioning electronics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the last decades, pressure sensors have been one of the greatest successes of the MEMS industry. Many companies are using them in a variety of applications from the automotive to the environmental field. Currently piezoresistive pressure sensors are the most developed, and a well established technology to design and fabricate these sensors has been implemented. Capacitive pressure sensing, on the other hand, is still an open and really promising field.

Fragiacomo, Giulio; Eriksen, Gert F.; Christensen, Carsten; Thomsen, Erik Vilain

2011-01-01

59

Overall Spray Characteristics of Dimethyl ether and Biodiesel Fuel under the Ambient Pressure Conditions in a High Pressure Chamber  

Science.gov (United States)

The purpose of this paper is to investigate the effect of the ambient pressure on the overall spray characteristics of dimethyl ether (DME) and biodiesel fuel spray in a high-pressure combustion chamber. In order to investigate the spray performance under the various ambient pressure conditions, the high-pressure combustion chamber, which can be controlled by nitrogen gas to obtain the ambient pressure conditions, was applied. To determine the macroscopic structure of the spray, such as the spray development process and the axial/radial distance, frozen images of the spray can be obtained directly using a high-speed camera with a light source according to the elapsed time after energizing begins. At the same time, the results from the DME and biodiesel spray under atmospheric conditions were compared with the results from the spray under various ambient pressure conditions in the chamber. According to the spray characteristics, the axial and maximum radial distances of the biodiesel and DME spray decreased with an increase in the ambient pressure. Also, it was shown that the SMD (Sauter mean diameter) of droplets becomes smaller than that of the spray under the atmosphere condition as the ambient pressure in the high pressure chamber increases.

Kim, Hyung Jun; Park, Su Han; Lee, Chang Sik

60

An alternative method to Mariotte reservoir system for maintaining constant hydraulic pressure  

International Nuclear Information System (INIS)

Some studies being done to evaluate the suitability of the Yucca Mountain area as a potential radioactive waste repository require the application of a constant water pressure as a boundary condition to study water flow through porous media. The Mariotte reservoir system is commonly used to supply such a boundary condition. Several problems with the Mariotte reservoir system were discovered when it was used to apply a constant water pressure as a boundary condition for a prolonged period. The constant-pressure boundary condition is required for some lab. experiments to study water flow through porous media. The observed problems were caused by temperature and barometric-pressure fluctuations while the flow rates were very small and caused erroneous water flow-rate measurements. An alternative method was developed and used where the water pressure is controlled by regulating its level by using water-level sensing electrodes. The new method eliminated the effects of temperature and barometric-pressure fluctuations and maintained an acceptable accuracy of the estimated water flow rate without compromising the advantage of the Mariotte reservoir

1991-05-03

 
 
 
 
61

Particle behavior and char burnout mechanisms under pressurized combustion conditions  

Energy Technology Data Exchange (ETDEWEB)

Combined cycle systems with coal-fired gas turbines promise highest cycle efficiencies for this fuel. Pressurized pulverized coal combustion, in particular, yields high cycle efficiencies due to the high flue gas temperatures possible. The main problem, however, is to ensure a flue gas clean enough to meet the high gas turbine standards with a dirty fuel like coal. On the one hand, a profound knowledge of the basic chemical and physical processes during fuel conversion under elevated pressures is required whereas on the other hand suitable hot gas cleaning systems need to be developed. The objective of this work was to provide experimental data to enable a detailed description of pressurized coal combustion processes. A series of experiments were performed with two German hvb coals, Ensdorf and Goettelborn, and one German brown coal, Garzweiler, using a semi-technical scale pressurized entrained flow reactor. The parameters varied in the experiments were pressure, gas temperature and bulk gas oxygen concentration. A two-color pyrometer was used for in-situ determination of particle surface temperatures and particle sizes. Flue gas composition was measured and solid residue samples taken and subsequently analyzed. The char burnout reaction rates were determinated varying the parameters pressure, gas temperature and initial oxygen concentration. Variation of residence time was achieved by taking the samples at different points along the reaction zone. The most influential parameters on char burnout reaction rates were found to be oxygen partial pressure and fuel volatile content. With increasing pressure the burn-out reactions are accelerated and are mostly controlled by product desorption and pore diffusion being the limiting processes. The char burnout process is enhanced by a higher fuel volatile content.

Bauer, C.M.; Spliethoff, H.; Hein, K.R.G.

1999-07-01

62

Intelligent fiber optic pressure sensor for measurements in extreme conditions  

International Nuclear Information System (INIS)

Application of a fiber optic Fabry-Perot interferometer (FFPI) for measurements of pressure and speed of pressure variation in water reactors of nuclear power plants contributes to improving their safety and long-term metrological stability, which demands for intelligent sensors. It is shown that the manufacturing of a FFPI sensitive element based on a molecular layering nano-technology provides for substantial enhancement of the quality of the gauge. The algorithm of self-calibration of the pressure sensor based on the fact that the length of the FFPI cavity depends on the pressure at a constant spectrum of an optical source is considered. By means of fast tuning of the spectrum of an optical source it is possible to make self-calibration in the course of continuous work of the pressure gauge. It is also shown that the intelligent FFPI pressure sensor maintains metrological characteristics when the total dose of high-neutron/ gamma radiation is over 2 MGy. (authors)

2009-06-07

63

Behaviour of polymer muds under high pressure – high temperature conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A well is classified as a HPHT (High Pressure High Temperature) well if the static bottomhole temperatures are greater than 350 °C and when the formation pressures exceed 1800 kg/m3 ECD. Mud weights as high as 2400 kg/m3 may be required to maintain a proper well control. The temperature of the drilling fluid when circulating in the well may range from 0 °C to 150 °C and it is important that the drilling fluid maintain acceptable rheological properties within the whole range. The rheologica...

Larsen, Ha?vard

2007-01-01

64

Analysis of air-conditioning and drying processes using spreadsheet add-in for psychrometric data  

Directory of Open Access Journals (Sweden)

Full Text Available A spreadsheet add-in for the psychrometric data at any barometric pressure and in the air-conditioning and drying temperatureranges was developed using appropriate correlations. It was then used to simulate and analyse air-conditioning and dryingprocesses in the Microsoft Excel environment by exploiting its spreadsheet and graphic potentials. The package allowsone to determine the properties of humid air at any desired state, and to simulate and analyse air-conditioning as well asdrying processes. This, as a teaching tool, evokes the intellectual curiosity of students and enhances their interest and abilityin the thermodynamics of humid-air processes.

E.O. Diemuodeke

2010-01-01

65

Solid Nitrogen at Extreme Conditions of High Pressure and Temperature  

Energy Technology Data Exchange (ETDEWEB)

We review the phase diagram of nitrogen in a wide pressure and temperature range. Recent optical and x-ray diffraction studies at pressures up to 300 GPa and temperatures in excess of 1000 K have provided a wealth of information on the transformation of molecular nitrogen to a nonmolecular (polymeric) semiconducting and two new molecular phases. These newly found phases have very large stability (metastability) range. Moreover, two new molecular phases have considerably different orientational order from the previously known phases. In the iota phase (unlike most of other known molecular phases), N{sub 2} molecules are orientationally equivalent. The nitrogen molecules in the theta phase might be associated into larger aggregates, which is in line with theoretical predictions on polyatomic nitrogen.

Goncharov, A; Gregoryanz, E

2004-04-05

66

Estimation of partial pressure during graphite conditioning by matrix method  

International Nuclear Information System (INIS)

Plasma Facing Components (PFC) of SST-1 tokamak are designed to be compatible for UHV as it is kept in the main vacuum vessel. Graphite is the most widely used plasma facing material in present day tokamaks. High thermal shock resistance and low atomic number carbon are the most important properties of graphite for this application. However, graphite is porous and absorbs gases, which may be released during plasma operation. Graphite tiles are baked at high temperature of about 1000 deg. C in high vacuum (10-5 Torr) for several hours before installing them in the tokamak to remove the impurities (mainly water vapour and metal impurities), which may have been deposited during machining of the tiles. The measurements of the released gas (such as H2, H2O, CO, CO2, Hydrocarbons, etc.) from graphite tiles during baking are accomplished with the help of a Quadrupole Mass Analyzer (QMA). Since, the output of this measurement is a mass spectrum and not the partial pressures of the residual gases, one needs to adopt some procedure to convert the spectrum to obtain the partial pressures. The conventional method of analysis is tedious and time consuming. We propose a new approach based on constructing a set of linear equations and solving them using matrix operations. This is a simple method compared to the conventional one and also eliminates the limitations of the conventional method. A Fortran program has been developed which identifies the likely gases present in the vacuum system and calculates their partial pressures from the data of the residual gas analyzers. Application of this method of calculating partial pressures from mass spectra data will be discussed in detail in this paper

2008-05-01

67

Stability of Perovskite under Lower Mantle Pressure and Temperature Conditions  

Science.gov (United States)

Shock recovery experiments of (Mg0.92, Fe0.08)SiO3 enstatite were conducted at pressures between 60 and 120GPa with the corresponding temperatures of 1600-3000K. X-ray diffraction (XRD) and infrared absorption spectra (IR) analysis on recovered samples indicates that the main phase of the recovered samples is not perovskite, but similar to enstatite. There is no evidence for presence of oxides SiO2 and (Mg0.92, Fe0.08)O in the recovered samples. The XRD data show that some diffraction peaks of the recovered samples cannot be matched with the diffraction pattern of the original sample. These peaks are more obvious with increasing pressure. The shock recovery experiments were performed in the stability field of perovskite. The shocked sample is expected to be of the perovskite structure, supported by the observed Hugoniot equation of state of perovskite. The non-perovskite phase in the recovered sample is likely resulted from a retrogressive transformation of the shocked samples during the unloading process. It is evident that the high-pressure phase did not undergo a chemical decomposition reaction of (Mg0.92, Fe0.08)SiO3 to oxides SiO2 and (Mg0.92, Fe0.08)O during the shock compression because no SiO2 and (Mg0.92, Fe0.08)O oxides were found in the recovered samples. The observed extra diffraction in the recovered sample may be caused by crystal distortion. Further characterization of the recovered sample by TEM may shine some light on the nature of the retrogressive transformation of the shocked samples.

Zhang, L.; Gong, Z.; Fei, Y.; Jing, F.

2003-12-01

68

Barometric gas transport along faults and its application to nuclear test-ban monitoring  

International Nuclear Information System (INIS)

Underground nuclear explosions produce a unique but evanescent set of radionuclide gases that potentially can be used in the context of an on-site, test-ban monitoring program to differentiate them from other detected events such as earthquakes or mining activity. In Part I of this report we describe an experiment to evaluate the upward transport of gases from an underground explosion using two gas tracers with very different diffusivities that were released in a 400-m-deep, chemical explosive detonation. The less diffusive (more massive) tracer was detected on a nearby geologic fault 50 days following the detonation while the more diffusive tracer was detected 375 days after release. Computer simulations indicate that the arrival time and the chromatographic behavior of transport are characteristic of barometrically induced flow in a fractured, porous matrix regime. For a hypothetical 1-kiloton fission explosion subject to the same weather and gas transport conditions of the chemical explosion, simulations predict the detectability of argon-37 after 80 days in spite of depletion by radioactive decay. Largely because of the earlier arrival of xenon-133, owing to its lower binary gas diffusivity, the exceedingly short lived isotope should also be detectable - arriving about 30 days earlier than argon. In Part II we consider that our prediction of the detectability of argon and xenon is based upon the small volume (0.00001 m3) sampling technique of the NPE tracer-gas sampling study while actual sampling for radionuclides would involve drawing much larger volume (possibly 0.1-1 m3) gas samples from the near-surface. Extraction of such a large volume of gas from 1-5 meter depths in the soil raises the possibility of significant atmospheric infiltration, leading to substantial dilution of the extracted gas sample. However, an infiltration experiment suggests that significant dilution would not, in fact, occur at the most prolific sampling stations of the earlier gas-tracer study. Of the soil gas being extracted at the shallowest sample site, less than 10% of the gas in the sample volume can be attributed to the infiltration of atmospheric gas. (author)

1997-01-01

69

Intramuscular pressures for monitoring different tasks and muscle conditions  

Science.gov (United States)

Intramuscular fluid pressure (IMP) can easily be measured in man and animals. It follows the law of Laplace which means that it is determined by the tension of the muscle fibers, the recording depth and by fiber geometry (fiber curvature or pennation angle). Thick, bulging muscles create high IMPs (up to 1000 mmHg) and force transmission to tendons becomes inefficient. High resting or postexercise IMPs are indicative of a compartment syndrome due to muscle swelling within a low-compliance osseofascial boundary. IMP increases linearly with force (torque) independent of the mode or speed of contraction (isometric, eccentric, concentric). IMP is also a much better predictor of muscle force than the EMG signal. During prolonged low-force isometric contractions, cyclic variations in IMP are seen. Since IMP influences muscle blood flow through the muscle pump, autoregulating vascular elements, and compression of the intramuscular vasculature, alterations in IMP have important implications for muscle function.

Sejersted, O. M.; Hargens, A. R.

1995-01-01

70

Pressurized water reactor iodine spiking behavior under power transient conditions  

International Nuclear Information System (INIS)

The most accepted theory explaining the cause of pressurized water reactor iodine spiking is steam formation and condensation in damaged fuel rods. The phase transformation of the primary coolant from water to steam and back again is believed to cause the iodine spiking phenomenon. But due to the complex nature of the phenomenon, a comprehensive model of the behavior has not yet been successfully developed. This paper presents a new model based on an empirical approach, which gives a first-order estimation of the peak iodine spiking magnitude. Based on the proposed iodine spiking model, it is apparent that it is feasible to derive a correlation using the plant operating data base to monitor and control the peak iodine spiking magnitude

1992-06-07

71

The impact of hepatic pressurization on liver shear wave speed estimates in constrained versus unconstrained conditions  

Science.gov (United States)

Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force-derived shear wave-based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood and is not explained with commonly used linear elastic mechanical models. An experiment was designed to determine whether the stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation-force-derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (0-35 mmHg) from 1.5 to 3.5 m s-1. These increases were observed only under conditions in which the liver was free to expand while pressurized. This behavior is consistent with hyperelastic nonlinear material models that could be used in the future to explore methods for estimating hepatic interstitial pressure noninvasively.

Rotemberg, V.; Palmeri, M.; Nightingale, R.; Rouze, N.; Nightingale, K.

2012-01-01

72

The impact of hepatic pressurization on liver shear wave speed estimates in constrained versus unconstrained conditions  

International Nuclear Information System (INIS)

Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force-derived shear wave-based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood and is not explained with commonly used linear elastic mechanical models. An experiment was designed to determine whether the stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation-force-derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (0–35 mmHg) from 1.5 to 3.5 m s?1. These increases were observed only under conditions in which the liver was free to expand while pressurized. This behavior is consistent with hyperelastic nonlinear material models that could be used in the future to explore methods for estimating hepatic interstitial pressure noninvasively. (paper)

2012-01-21

73

The Impact of Hepatic Pressurization on Liver Shear Wave Speed Estimates in Constrained vs. Unconstrained Conditions  

Science.gov (United States)

Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force derived shear wave based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood, and is not explained with commonly-used linear elastic mechanical models. An experiment was designed to determine whether the stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation force derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (0–35mmHg) from 1.5 to 3.5 m/s. These increases were observed only under conditions in which the liver was free to expand while pressurized. This behavior is consistent with hyperelastic nonlinear material models that could be used in the future to explore methods for estimating hepatic interstitial pressure noninvasively.

Rotemberg, V.; Palmeri, M.; Nightingale, R.; Rouze, N.; Nightingale, K.

2012-01-01

74

Assessment of the conditions for coal seam pressure release by an outburst of gas  

Energy Technology Data Exchange (ETDEWEB)

One type of outburst of gas involves a release of gas and rock pressure from part of a coal seam which has fractured or become geologically plastic. The authors describe the conditions leading to a pressure release of this type, and outline the factors that determine the rate of pressure release. Numerical calculations are employed to evaluate the possibility of an outburst. The following conditions are inserted into the calculations: cross-section: 100 x 100 cm; depth: 800 m; methane gas pressure: 20 kg/cm/sup 2/; inclination: 45 degrees. 3 references, 4 figures.

Ujibira, M.; Higuchi, S.; Nakazaki, I.

1986-01-01

75

Application of the subchannel analysis code MATRA for low flow and low pressure conditions  

International Nuclear Information System (INIS)

Subchannel analysis codes usually solve a boundary value problem and use a multipass marching scheme. This multi-pass marching scheme finds the enthalpy, density, cross flow, axial flow and pressure at each axial plane until errors of the cross flow and axial flow satisfy convergence criteria and then the scheme iterates an axial sweep until finding unknown inlet boundary conditions that satisfy the outlet boundary conditions. In this approach, numerical errors at each iteration are accumulated and may induce numerical instabilities such as a numerical oscillation or loss of diagonal dominance under low-pressure and low-flow conditions. This paper presents an improvement of a convergence of a subchannel analysis code under low-pressure and low-flow rate conditions. A once-through marching scheme was implemented into the subchannel analysis code MATRA. The scheme obtains converged numerical solutions at each axial plane by marching from the inlet to the outlet only once. Based on the assumption that the pressure distribution is uniform at each axial plane, the lateral pressure difference between subchannels is sufficiently small. The once through marching scheme was validated firstly by comparisons with the multi-pass marching scheme at high-pressure and high flow conditions. And the performance of the once-through marching scheme was assessed for the low flow and low pressure conditions in the CHF experiments carried out at the Winfrith establishment of the UKAEA. (authors)

2008-06-08

76

A study on the manufacturing conditions of metal matrix composites by low pressure infiltration process  

International Nuclear Information System (INIS)

Metal fiber preform reinforced aluminum alloy composite as made by the infiltration of molten metal under low pressure casting process. The infiltration behavior of filling pattern and the velocity profile with low-pressure casting process was investigated. The thermocouple was inserted into the preform in order to observe the infiltration behavior. The infiltration of applied pressure time, 1, 2 and 5 s under constant pressure of 0.4 MPa was completely filled during 0.4 s. In these conditions, molten aluminum alloy has successfully infiltrated to FeCrSi metal fiber preform by low-pressure casting process. It was observed the porosity of composites for reliability of composites. The automobile piston was developed with FeCrSi reinforced aluminum alloy that is 0% porosity by the optimal applied pressure and applied pressure time

2007-10-01

77

Stability of Pressure Boundary Conditions for Stokes and Navier-Stokes Equations  

Science.gov (United States)

The stability of a finite difference discretization of the time-dependent incompressible Navier-Stokes equations in velocity-pressure formulation is studied. In paticular, we compare the stability for different pressure boundary conditions in a semiimplicit time-integration scheme. where only the viscous term is treated implicitly. The stability is studied in three different ways: by a normal-mode analysis, by numerical computation of the amplification factors, and by direct numerical simulation of the governing equations. All three approaches identify the same pressure boundary condition as the best alternative. This condition implicitly enforces the normal derivative of the divergence to be zero on the boundary by coupling the normal derivative of the pressure to the normal component of the curl of the vorticity. Using this boundary condition, we demonstrate that the time-step is determined only by the convective term.

Petersson, N. Anders

2001-09-01

78

Flash-type barometric desalination plant powered by waste heat from electricity power stations in Cyprus  

International Nuclear Information System (INIS)

This paper describes and evaluates the results of a study into the problems of freshwater production and shortages on the island of Cyprus. The use of a novel barometric flash-type desalinator, driven by otherwise waste-heat from the island's power-stations, is proposed as a means of increasing freshwater supplies. Mathematical models are described and used to investigate the thermodynamic performance and economic viability of the proposed system. Although water and electricity-supply data for the island of Cyprus were used for the purposes of this investigation, the overall findings are thought to have a wider applicability

2007-01-01

79

Individual Pressure Vessel (PV) and Common Pressure Vessel (CPV) Nickel-Hydrogen Battery Performance Under LEO Cycling Conditions  

Science.gov (United States)

LEO life cycle testing of Individual Pressure Vessel (PV) and Common Pressure Vessel (CPV) nickel-hydrogen cell packs have been sponsored by the NASA Aerospace Flight Battery Program. The cell packs have cycled under both 35% and 60% depth-of- discharge and temperature conditions of -5 C and +lO C. The packs have been on test since as early as 1992 and have generated a substantial database. This report will provide insight into performance trends as a function of the specific cell configuration and manufacturer for eight separate nickel-hydrogen battery cell packs.

Miller, Thomas B.; Lewis, Harlan L.

2004-01-01

80

Earth tidal and barometric responses observed in the Callovo-Oxfordian formation at ANDRA Meuse/Haute-Marne underground research laboratory  

International Nuclear Information System (INIS)

Document available in extended abstract form only. Fluid pressure or hydraulic head measured in wells in geological formations can respond to Earth tidal forces and atmospheric pressure variations. At Andra Meuse/Haute-Marne underground research laboratory located in Bure (France), water level and fluid pressure are measured in several boreholes in the Callovo-Oxfordian clay formation (COX) and in overlying geological formations. One of these boreholes (EST207) is equipped with a multi-packer system monitoring 11 intervals, including 8 in the COX. The recorded fluid pressures in EST207 were analyzed to determine possible Earth tidal responses. In this borehole, the fluid pressure and atmospheric pressure variations data are recorded every fifteen minutes and 6.5 years of such data from 2004/06/02 to 2010/12/31 were analyzed. Various perturbed data, gaps, drift and abnormal data were corrected through a data preprocessing process. Data interpolation and filtering processes were performed to have data available every 15 minutes at 0, 15, 30 and 45 minutes on the hour. A spectral analysis (Fast Fourier Transform) of each pressure data series shows amplitude peaks at frequencies corresponding to various Earth tidal frequencies: diurnal and semi diurnal waves can be identified. Spectral analyses were also performed on the atmospheric pressure data. The solar semi diurnal wave (S2) was identified. The 'Earth Tides ETERNA package' was used to separate the waves according to the frequencies bands. The analyses performed using ETERNA are indicated as 'Earth Tidal Analyses' (ETAN). Tidal parameters are estimated from ETAN: amplitudes A and its standard deviation ?(A)[hPa], phase ? for the main waves in diurnal and semi diurnal frequencies bands before and after atmospheric pressure variations correction. The barometric efficiency (BE) and its standard deviation ? (BE) as regression coefficient is calculated. The atmospheric pressure data are also analyzed with ETERNA; the wave S2 amplitude and phase values usually taken into account as references are in good agreement with values calculated at others sites. This result validates the atmospheric pressure data sets. Having high quality data and multi-year data sets, it was possible to separate several main tidal waves in the diurnal band and in the semi diurnal band. K1, O1, P1, S1 and M2, N2, S2, K2 bands were first taken into account in each series to determine whether they were significant or not. The ETAN results are in good agreement with the spectral analyses results and with these results it can be concluded that the 11 monitoring intervals in borehole EST207 respond to Earth Tidal forces and to atmospheric pressure variations. The ETERNA software allows identifying more tidal waves with more accuracy. In all the intervals, the best identified significant waves are O1, K1, M2 and S2. While the M2 amplitude is not or only slightly perturbed by atmospheric pressure variations and the M2 phase is not, the S2 wave amplitude and phase are very sensitive to atmospheric pressure. After barometric correction, the amplitudes through the borehole are generally decreasing from the bottom to the top. In a preliminary hydrogeological interpretation, the detailed intercomparison of tidal analyses results according to the barometric correction effect, the BE values and the waves identification quality provide a classification of the barometric and tidal responses as a function of the various intervals. These responses were classified into four groups depending on the monitoring intervals in the Dogger, the lower COX, the upper COX and the base of Oxfordian. The BE values show that the greater the clay content of the formation is, the greater the BE values are. The BE values in the Dogger are similar to the values estimated in the Oxfordian. In 2003, Andra investigated earth tides and barometric responses in the Oxfordian of two boreholes, EST203 and EST104. The hydrogeological interpretation in these two boreholes provided estimates of transmissivity and storage coefficient consistent wi

2012-10-01

 
 
 
 
81

Detectability and significance of 12 hr barometric tide in radon-222 signal, dripwater flow rate, air temperature and carbon dioxide concentration in an underground tunnel  

Science.gov (United States)

Searching for small periodic signals, such as the 12 hr (S2) barometric tide, and monitoring their amplitude as a function of time, can provide important clues on the complex processes affecting fluid transport in unsaturated fractured media under multiple influences. Here, first, we show that a modified spectrogram analysis (MSA) is more efficient than simple Fourier transform to reveal weak periodic signals. Secondly, we show how transient periodic signals can be monitored as a function of time using spectrograms. These methods are applied to time-series of radon and carbon dioxide concentration, dripwater flow rates and air temperature measured during several years in the Roselend dead-end tunnel, located in the French Alps near an artificial lake. A weak S2 line is evidenced in radon concentration, with enhanced amplitude during transient radon bursts. Similarly, the S2 line is observed using MSA in dripwater flow rates which sample mainly fracture flow, as suggested by a hydrochemical analysis, while it is not seen in dripwater flow rates sampling matrix flow. In the absence of a strong 24 hr line, the presence of a S2 line suggests sensitivity to barometric pressure, and thus a significant advective contribution in radon and some dripwater transport. No S2 line is observed in the carbon dioxide time-series. The temporal structure of the S2 component, however, is not similar in the radon concentration and the dripwater flow rates, suggesting, in particular, that dripwater does not play a significant role in the generation of radon bursts. Temperature time-series exhibit a significant S2 contribution, induced by atmospheric pressure, spatially organised in the tunnel, decreasing vertically upwards. A remarkable transient temperature inversion during radon bursts suggests that the additional advective air contributions responsible for the radon bursts occur from the non-saturated rocks below the tunnel.

Richon, Patrick; Perrier, Frédéric; Pili, Eric; Sabroux, Jean-Christophe

2009-03-01

82

Analytic Modeling of Pressurization and Cryogenic Propellant Conditions for Lunar Landing Vehicle  

Science.gov (United States)

This slide presentation reviews the development, validation and application of the model to the Lunar Landing Vehicle. The model named, Computational Propellant and Pressurization Program -- One Dimensional (CPPPO), is used to model in this case cryogenic propellant conditions of the Altair Lunar lander. The validation of CPPPO was accomplished via comparison to an existing analytic model (i.e., ROCETS), flight experiment and ground experiments. The model was used to the Lunar Landing Vehicle perform a parametric analysis on pressurant conditions and to examine the results of unequal tank pressurization and draining for multiple tank designs.

Corpening, Jeremy

2010-01-01

83

Indirect Calorimetry in Low Pressure Environments.  

Science.gov (United States)

Equipment to measure energy exchange in low pressure environments was evaluated. A volume-summing apparatus with a proportional gas sampler, the Muller-Franz gas meter, proved to be reliable at barometric pressures of 447 and 259 torr (equivalent to 14,00...

M. J. Ryan S. M. Cain

1967-01-01

84

Unsteady Pressure Measurements around Rotor of an Axial Flow Fan under Stable and Unstable Operating Conditions  

Science.gov (United States)

This study presents some measurement results on the unsteady pressure fields around rotor under stable and unstable operating conditions of an axial flow fan. The unsteady static pressure of rotor passage was measured by using high frequency pressure transducers mounted on the casing wall. The measurements on the unsteady total pressure at rotor inlet and outlet were also conducted with specially designed high frequency total pressure probe. Double Phase-Locked Ensemble Averaging Technique was used for analysis of pressure fluctuations around the rotor at rotating stall onset point. From the results, the unsteady pressure fields during stable and unstable operations of the axial fan were investigated and compared with each other. Particularly one period of rotating stall could be divided into two regions, stalled flow and unstalled flow region respectively. Furthermore the former could be also classified into two zones, bubbled and disturbed region by their features. The flow characteristics for each zone were described in detail and the static and total pressure fields were also analyzed in terms of the pressure distribution along pressure side and suction side on the blade tip profile.

Shin, You Hwan; Kim, Kwang Ho; Kang, Chang Sik

85

Accessing High Pressure States Relevant to Core Conditions in the Giant Planets  

Energy Technology Data Exchange (ETDEWEB)

We have designed an experimental technique to use on the National Ignition Facility (NIF) laser to achieve very high pressure (P{sub max} > 10 Mbar = 1000 GPa), dense states of matter at moderate temperatures (kT < 0.5 eV = 6000 K), relevant to the core conditions of the giant planets. A discussion of the conditions in the interiors of the giant planets is given, and an experimental design that can approach those conditions is described.

Remington, B A; Cavallo, R M; Edwards, M J; Ho, D D; Lorenz, K T; Lorenzana, H E; Lasinski, B F; McNaney, J M; Pollaine, S M; Smith, R F

2004-04-15

86

On pressure and velocity boundary conditions for the lattice Boltzmann BGK model  

International Nuclear Information System (INIS)

Pressure (density) and velocity boundary conditions are studied for 2-D and 3-D lattice Boltzmann BGK models (LBGK) and a new method to specify these conditions is proposed. These conditions are constructed in consistency with the wall boundary condition, based on the idea of bounceback of the non-equilibrium distribution. When these conditions are used together with the incompressible LBGK model [J. Stat. Phys. 81, 35 (1995)] the simulation results recover the analytical solution of the plane Poiseuille flow driven by a pressure (density) difference. The half-way wall bounceback boundary condition is also used with the pressure (density) inlet/outlet conditions proposed in this paper and in Phys. Fluids 8, 2527 (1996) to study 2-D Poiseuille flow and 3-D square duct flow. The numerical results are approximately second-order accurate. The magnitude of the error of the half-way wall bounceback boundary condition is comparable with that of other published boundary conditions and it has better stability behavior. copyright 1997 American Institute of Physics

1997-06-01

87

On pressure and velocity boundary conditions for the lattice Boltzmann BGK model  

Energy Technology Data Exchange (ETDEWEB)

Pressure (density) and velocity boundary conditions are studied for 2-D and 3-D lattice Boltzmann BGK models (LBGK) and a new method to specify these conditions is proposed. These conditions are constructed in consistency with the wall boundary condition, based on the idea of bounceback of the non-equilibrium distribution. When these conditions are used together with the incompressible LBGK model [J. Stat. Phys. {bold 81}, 35 (1995)] the simulation results recover the analytical solution of the plane Poiseuille flow driven by a pressure (density) difference. The half-way wall bounceback boundary condition is also used with the pressure (density) inlet/outlet conditions proposed in this paper and in Phys. Fluids {bold 8}, 2527 (1996) to study 2-D Poiseuille flow and 3-D square duct flow. The numerical results are approximately second-order accurate. The magnitude of the error of the half-way wall bounceback boundary condition is comparable with that of other published boundary conditions and it has better stability behavior. {copyright} {ital 1997 American Institute of Physics.}

Zou, Q. [Theoretical Division, Los Alamos National Lab, Los Alamos, New Mexico 87545 (United States)]|[Department of Mathematics, Kansas State University, Manhattan, Kansas 66506 (United States); He, X. [Center for Nonlinear Studies and Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1997-06-01

88

Pressure-temperature conditions in granulite facies rocks of the northern Canadian Shield, Arctic Canada  

Energy Technology Data Exchange (ETDEWEB)

The northernmost part of the Churchill Structural Province of the Canadian Shield, underlying 60,000 km/sup 2/ of southeastern Ellesmere Island, Coburg Island and eastern Devon Island, consists of granulite facies metasedimentary, meta-igneous and plutonic intrusive rocks 2400 to 1900 m.y. old. Garnet+pyroxene+plagioclase of quartzofeldspathic gneisses from Ellesmere and Coburg islands indicate pressures, at 750/sup 0/C, ranging from greater than or equal to 6 to approx. 4kb; the lower pressures are derived largely, but not solely, from rim compositions. Similar rocks from Devon Island consistently indicate higher pressures of 6 to 7 kb. Garnet and plagioclase cores in sillimanite+cordierite-rich pelitic gneisses give pressures between 5 and 6.5 kb at 750/sup 0/C, the highest pressures being found in Devon Island rocks. Orthopyroxene+cordierite symplectites around garnet in magnesian metapelites indicate pressures under 4 kb at 650/sup 0/C. All cordierite is clearly of retrograde origin, having formed as a result of decompression during uplift, but even the highest pressures determined fall below the stability limit of cordierite in metapelites. Circumstantial evidence exists for the former stable coexistence of orthopyroxene+sillimanite, which would attest to pressures well in excess of 7 kb, but existing geobarometric equilibria have been strongly influenced by retrograde processes. Retrograde pressure-temperature conditions may well predominate in many granulite terranes but are not always recognized due to a scarcity of suitable mineral assemblages.

Frisch, T.

1985-01-01

89

Simulation of subcooled boiling at low pressure conditions with RELAP5-3D computer program  

International Nuclear Information System (INIS)

Simulation of subcooled boiling was carried out using RELAP5 thermal hydraulic computer programs. Both 1D and 3D analyses were carried out with RELAP5/MOD3.2 and RELAP5-3D code. Experimental data from the subcooled boiling experiment at low pressure conditions of Bartel, and Zeitoun and Shoukri were simulated. The RELAP5/MOD3.2 was executed to determine the axial void faction distribution. The predictions of void fraction distributions at low-pressure conditions were underestimated. The same model was used to simulate high pressure subcooled boiling data. High pressure subcooled boiling experiments of Bartolomey and Sabotinov were simulated. The axial void fraction distribution results of RELAP5/MOD3.2 were in a good agreement with the experimental data. (author)

2003-04-20

90

A SUGGESTION FOR THE PERMANENT SUPPORT DRIVE IN CONDITIONS OF CONSIDERABLE UNDERGROUND PRESSURE  

Directory of Open Access Journals (Sweden)

Full Text Available In the conditions of considerable underground pressures 12 different technologies were applied during the drift driving in the lignite mine »Titovo Velenje«. The drift is driven largely through marly clays and tuffs with sandstone. The most of applied technologies of performance, especially in the areas with considerable pressures, have not given satisfactory results in view considering the realized dynamics of works, stability maintenance and the cross-section clearance diagram of the drift. The analysis of the used driving technologies and underground pressures serves fur the construction of permanent support, differing basically from standing rigid classical supports. The characteristics of a conceived support, in conditions of considerable underground pressures, enable the construction of a drift with the complete profile, the maintenance of planned working dynamics, the stability and safety of the drift which decreases the cost price for the built meter of the drift.

Darko Vrkljan

1989-12-01

91

Determination of optimal conditions for pressure oxidative leaching of Sarcheshmeh Molybdenite concentrate using Taguchi method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present research work is based on finding the optimum conditions for pressure oxidative leaching of the molybdenite concentrate to produce technical-grade molybdic oxide (MoO3) with high recovery through further treatment of the filtrate solution. The Taguchi method was used to design and minimize the number of experiments. By using Taguchi orthogonal (L25) array, five parameters (time, temperature, oxygen pressure, pulp density and acid concentration) at five levels were selected f...

Khoshnevisana A.; Yoozbashizadeha H.

2012-01-01

92

Effects of pressure and inter-electrode distance on deposition of nanocrystalline silicon under high pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

Pressure (p) and inter-electrode distance (d) are important parameters in the process of depositing hydrogenated nanocrystalline silicon (nc-Si:H) by very high frequency plasma enhanced chemical vapour deposition (VHF PECVD). High quality nc-Si:H materials are normally deposited at high pressure (1 mbar < p < 7 mbar). However, systematic research on the combined effects of p and d is rare. In order to optimize nc-Si:H for solar cells, such effects are investigated for a silane-hydrogen discharge at high pressure conditions. All nc-Si:H layers were deposited at fixed hydrogen dilution ratio (H{sub 2}/SiH{sub 4}), power and frequency. With optical emission spectroscopy, direct images taken by a photo camera and by 1D SiH{sub 4}/H{sub 2} plasma simulation, three different series were analyzed to study the combined effects of p and d at high pressure. The effects on the crystalline ratio and the porosity of the deposited silicon layers were also investigated. When the p .d product is constant, the plasma sheath becomes relatively thinner when d increases. When p or d increases independently, the electron density decreases. All the above modifications can increase the deposition rate, but by different mechanisms. When nc-Si:H is deposited at a p.d product of 30 mbar.mm, compact material with high crystalline ratio is obtained (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Liu, Yanchao; Verkerk, Arjan D.; Rath, Jatindra K.; Schropp, Ruud E.I. [Debye Institute for Nanomaterials Science, Section Nanophotonics - Physics of Devices, Faculty of Science, Utrecht University (Netherlands); Goedheer, Wim J. [FOM-Institute for Plasma Physics, Nieuwegein (Netherlands)

2010-04-15

93

LHe Flow Regime/Pressure Drop for D0 Solenoid at Steady State Conditions  

Energy Technology Data Exchange (ETDEWEB)

This paper describes in a note taking format what was learned from several sources on two phase liquid helium flow regimes and pressure drops as applied to the D-Zero solenoid upgrade project. Calculations to estimate the steady state conditions for the D-Zero solenoid at 5, 10 and 15 g/s are also presented. For the lower flow rates a stratified type regime can be expected with a pressure drop less than 0.5 psi. For the higher flow rate a more homogeneous flow regime can be expected with a pressure drop between 0.4 to 1.5 psi.

Rucinski, R.; /Fermilab

1993-03-03

94

Cutting and conditioning of the reactor pressure vessel in the NPP Wuergassen  

International Nuclear Information System (INIS)

NPP Wuergassen was shutdown in 1995 after 23 years of operation. Since 1997 the nuclear power plant is being dismantled. The cutting of the reactor pressure vessel internals was performed between 2003 and 2008. After decontamination the cylindrical parts of the reactor pressure vessel were dissected, the process was finalized in 2010. AREVA has now a 30 years-experience concerning repair, replacement and dismantling of reactor components. In the contribution the authors describe the process planning, manufacture and testing of appropriate remote handled tools, decontamination, dissection of the pressure vessel (320 t), conditioning, packaging and transport of the radioactive waste including radiation protection monitoring.

2011-05-17

95

On pressure and velocity flow boundary conditions for the lattice Boltzmann BGK model  

CERN Multimedia

Pressure (density) and velocity boundary conditions inside a flow domain are studied for 2-D and 3-D lattice Boltzmann BGK models (LBGK) and new method to specify these conditions are proposed. These conditions are consistent with the boundary condition we proposed in a previous paper using an idea of bounce-back of non-equilibrium distribution. These conditions give excellent results for the regular LBGK models, and were shown to be second-order accurate by numerical examples. When they are used together with the improved incompressible LBGK model proposed by zou et al. the simulation results recover the analytical solution of the plane Poiseuille flow driven by pressure (density) difference with machine accuracy.

Zou, Q; Zou, Qisu; He, Xiaoyi

1995-01-01

96

A facility for solid-propellant response measurements under pressure-driven conditions  

Science.gov (United States)

An acoustic driver system was developed to investigate unsteady combustion characteristics of solid propellants under pressure oscillations. Two model airplane engines driven by an electric motor were used to produce nearly sinusoidal pressure variations; a consistent peak-to-peak pressure variation of 10% of the mean pressure was obtained using the engines. A pressure insensitive, sub-miniature load cell was used to measure the thrust response of the solid propellants. The load cell was placed in a ceramic holder to protect it from the high temperature of gaseous products evolved during experiments, and the bottom of the holder was coated with several layers of a damping material to reduce the effect of vibrations produced by the engines. Measurements of the thrust response were successfully made over the frequency range 4-130 Hz near atmospheric pressure in air. A minimum signal-to-noise ratio of 3:1 was obtained using the system, and both amplitude and phase information could be simultaneously extracted from the thrust response data. The reliability of the present acoustic driver system was verified by comparing response data obtained from the present and radiation-driven facilities under radiation-driven conditions. For an AP/HTPB composite propellant under pressure-driven conditions with the present facility, maximum non-dimensional thrust responses at 35 W cm-2 were measured at 12 and 16 Hz, respectively, where the phase passed through approximately zero.

Lee, Young Joo; Kudva, Gautam N.; Litzinger, Thomas A.

2000-01-01

97

Heat transfer modelling of CANDU pressure tube under localized high temperature condition  

Energy Technology Data Exchange (ETDEWEB)

The main objective of this research is to develop thermal models in order to evaluate mechanical deformation of the potential contacts between fuel elements and pressure tube in the CANDU reactor. The consequence of concern is potential creep strain failure of a pressure tube and calandria tube challenging fuel channel integrity. The initial focus will be on the case where a fuel rod contacts the pressure tube at full power with high cooling flow. Such an event could occur if a fuel element was to become detached from a bundle. The heat conduction from fuel sheath to the inner surface of the pressure tube with appropriate convective and radiation boundary conditions has been simulated. The contact boundary could be a single spot or a small arc between the fuel sheath and pressure tube. The vapor pockets are considered in the areas beside the contact region where the convective cooling is drastically decreased. Subsequently, modelling has been extended to the contact of number of fuel elements where several fuel rods are postulated to contact the pressure tube under fully cooling conditions. It is observed that pressure tube creep strain will occur if sufficiently high temperature is reached. (author)

Talebi, F.; Luxat, J.C. [Engineering Physics Dept., McMaster Univ., Hamilton, Ontario (Canada)], E-mail: farshat@mcmaster.ca, luxatj@mcmaster.ca

2009-07-01

98

The Rheological Properties of Oil-Based Mud under High Pressure and High Temperature Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Designing a proper drilling fluid that can function properly under the conditions of High-Pressure, High-Temperature (HP/HT) operations is very challenging. Among these challenges is the alteration of the rheological properties of drilling fluid due to the high temperature and high pressure (Ibeh et. al, 2007). This work investigates the rheological behavior of oil-based drilling fluids with different properties at Ultra-HP/HT conditions using a state-of-the-art ...

Mahmood Amani

2012-01-01

99

Separating expansion from contraction: generalized TOV condition, LTB models with pressure and $\\Lambda$CDM  

CERN Multimedia

We discuss the existence of a dividing shell separating expanding and collapsing regions in spherically symmetric solutions with pressure. We obtain gauge invariant conditions relating not only the intrinsic spatial curvature of the shells to the ADM mass, but also a function of the pressure which we introduce that generalises the Tolman-Oppenheimer-Volkoff equilibrium condition, in the framework of a 3+1 spacetime splitting. We consider the particular case of a Lema\\^itre-Tolman-Bondi dust models with a cosmological constant (a $\\Lambda$-CDM model) as an example of our results.

Delliou, Morgan Le; Mimoso, José Pedro

2009-01-01

100

Effect of Specific Operating Conditions on the Properties of LPPS Plasma Jets Expanding at Low Pressure  

Energy Technology Data Exchange (ETDEWEB)

The LPPS processes, which use DG plasma jets expanding at low pressure, are widely used for the deposition of various kinds of layers. The supersonic expansion of the plasma jet in a low-pressure environment requires special care in the operating conditions in order to obtain the desired properties of the flow, regarding powder injection and transport and plasma jet-surface interaction. This paper presents measurements of the plasma jet properties for different chamber pressures. The torch is operated both in the over-expanded and under-expanded regimes, according to pressure measurements at the exit of the nozzle as a function of the backpressure. The topology of the expansion-compression zones of the plasma jet for the different operating pressures is inferred from imaging of the plasma jet. In addition, a modified enthalpy probe system is used to measure the specific enthalpy and the stagnation pressure profiles throughout the jet. De- termination of the local free-stream jet parameters, such as the temperature and velocity, for the case of supersonic flow is made assuming an isentropic frozen stagnation process at the probe tip. For these calculations the pressure dependence of the equilibrium thermodynamic and transport properties is accounted for. Discussion on expanded jet rarefaction is made for chamber pressure below 20 mbar, in the light of plasma jet imaging and nozzle exit pres- sure measurements. (author)

Gindrat, M.; Dorier, J.L.; Hollenstein, Ch.; Loch, M.; Refke, A.; Salito, A.; Barbezat, G

2001-10-01

 
 
 
 
101

Effect of Specific Operating Conditions on the Properties of LPPS Plasma Jets Expanding at Low Pressure  

International Nuclear Information System (INIS)

The LPPS processes, which use DG plasma jets expanding at low pressure, are widely used for the deposition of various kinds of layers. The supersonic expansion of the plasma jet in a low-pressure environment requires special care in the operating conditions in order to obtain the desired properties of the flow, regarding powder injection and transport and plasma jet-surface interaction. This paper presents measurements of the plasma jet properties for different chamber pressures. The torch is operated both in the over-expanded and under-expanded regimes, according to pressure measurements at the exit of the nozzle as a function of the backpressure. The topology of the expansion-compression zones of the plasma jet for the different operating pressures is inferred from imaging of the plasma jet. In addition, a modified enthalpy probe system is used to measure the specific enthalpy and the stagnation pressure profiles throughout the jet. De- termination of the local free-stream jet parameters, such as the temperature and velocity, for the case of supersonic flow is made assuming an isentropic frozen stagnation process at the probe tip. For these calculations the pressure dependence of the equilibrium thermodynamic and transport properties is accounted for. Discussion on expanded jet rarefaction is made for chamber pressure below 20 mbar, in the light of plasma jet imaging and nozzle exit pres- sure measurements. (author)

2001-01-01

102

Embedded optical probes for simultaneous pressure and temperature measurement of materials in extreme conditions  

Science.gov (United States)

We present recent efforts at Los Alamos National Laboratory (LANL) to develop sensors for simultaneous, in situ pressure and temperature measurements under dynamic conditions by using an all-optical fiber-based approach. While similar tests have been done previously in deflagration-to-detonation tests (DDT), where pressure and temperature were measured to 82 kbar and 400°C simultaneously, here we demonstrate the use of embedded fiber grating sensors to obtain high temporal resolution, in situ pressure measurements in inert materials. We present two experimental demonstrations of pressure measurements: (1) under precise shock loading from a gas-gun driven plate impact and (2) under high explosive driven shock in a water filled vessel. The system capitalizes on existing telecom components and fast transient digitizing recording technology. It operates as a relatively inexpensive embedded probe (single-mode 1550 nm fiber-based Bragg grating) that provides a continuous fast pressure record during shock and/or detonation. By applying well-controlled shock wave pressure profiles to these inert materials, we study the dynamic pressure response of embedded fiber Bragg gratings to extract pressure amplitude of the shock wave and compare our results with particle velocity wave profiles measured simultaneously.

Sandberg, R. L.; Rodriguez, G.; Gibson, L. L.; Dattelbaum, D. M.; Stevens, G. D.; Grover, M.; Lalone, B. M.; Udd, E.

2014-05-01

103

Study on Condensing Heat Transfer Test under High Temperature and High Pressure Conditions  

Science.gov (United States)

The condensing heat transfer coefficient is one of the important factors to evaluate the pressure change under BWR (Boiling Water Reactors) abnormal transients. Condensing condition is about 7 MPa of pressure with vapor flow. Many condensing studies have been done under atmospheric conditions with stagnant vapor. However, the condensing test results under BWR conditions have not reported. Therefore, the condensing heat transfer test of the saturated vapor with vertical upward vapor flow has been done under high temperature and high pressure conditions. The final purpose of this study is to develop the condensing correlation under BWR conditions. In this report, the data under pressures of 0.5 and 1 MPa are reported. Test section is tube. The inner diameter and condensing length is 57.6 mm and 2000 mm. Test fluid is saturated vapor. The following test results were obtained (1) Flooding may have occurred at a higher vapor velocity. (2) Vertical vapor flow has the effect to enhance the condensing heat transfer. (3) The measured heat transfer coefficients are larger than that of Nusselt model due to the vertical vapor flow

Morooka, Shinichi; Kubo, Shinji; Shirakawa, Ken-Etu; Yuasa, Hiroko; Yamamoto, Tetuzou; Ono, Hiroshi

104

On pressure and velocity flow boundary conditions and bounceback for the lattice Boltzmann BGK model  

CERN Document Server

Pressure (density) and velocity boundary conditions inside a flow domain are studied for 2-D and 3-D lattice Boltzmann BGK models (LBGK) and a new method to specify these conditions are proposed. These conditions are constructed in consistency of the wall boundary condition based on an idea of bounceback of non-equilibrium distribution. When these conditions are used together with the improved incompressible LBGK model by Zou et al., the simulation results recover the analytical solution of the plane Poiseuille flow driven by pressure (density) difference with machine accuracy. Since the half-way wall bounceback boundary condition is very easy to implement and was shown theoretically to give second-order accuracy for the 2-D Poiseuille flow with forcing, it is used with pressure (density) inlet/outlet conditions proposed in this paper and in Chen et al. to study the 2-D Poiseuille flow and the 3-D square duct flow. The numerical results are approximately second-order accurate. The magnitude of the error of th...

Zou, Q; Zou, Qisu; He, Xiaoyi

1996-01-01

105

Optimum thermodynamic conditions for upper pressure limits of transcritical carbon dioxide refrigeration cycle  

Energy Technology Data Exchange (ETDEWEB)

It is well known that the choice of upper pressure limit in a transcritical CO{sub 2} refrigeration cycle is independent of the gas cooler approach temperature. This is in contrast to sub-critical cycles, where the condensing pressure is invariably governed by the ambient conditions. The criteria used for limiting the upper pressure limit in a transcritical cycle are the state of maximum COP for a given set of evaporating and gas cooler exit temperatures. The latter is governed by the local ambient conditions and the possible approach. This paper provides a thermodynamic basis for the evaluation of this pressure for the case of ideal compression and with some compressors available in the market. In addition, it also provides an additional criterion that minimizes the cycle irreversibility which is predominantly due to gas throttling. This paper evaluates the pressure limits for these two criteria for some typical evaporating temperatures and ambient conditions. The possible compressor discharge temperatures in each case are calculated and criteria for two-stage compression are identified. (author)

Srinivasan, K. [Kandadai Intitiative for Sustainable Solutions, 2 Nepean Place, Willetton, WA 6155 (Australia); Sheahen, P.; Sarathy, C.S.P. [City Building Engineering Services (Aus) Pty. Ltd., Level 2, 350 Wellington Road, Mulgrave VIC 3170 (Australia)

2010-11-15

106

Study on condensing heat transfer test under high temperature and high pressure conditions  

International Nuclear Information System (INIS)

The condensing heat transfer test of the saturated vapor with vertical upward vapor flow has been done under high temperature and high pressure conditions. (1) Flooding may be occurred at higher vapor velocity. (2) Vertical vapor flow has the effect which increases the condensing heat transfer under laminar film conditions. (3) The measured heat transfer coefficients are larger than that of Nusselt model due to vertical vapor flow. (author)

2006-06-02

107

Analysis of the DHLW cask under normal and hypothetical accident-condition loads with initial pressure  

International Nuclear Information System (INIS)

The paper describes analyses performed for the Defense High-Level Waste (DHLW) cask design that establish an upper limit of 700 lbf/in2 (1 lbf/in2(g) = 6.895x103 Pa) for the cask maximum normal operating pressure (MNOP). Analyses of the cask with this MNOP as an initial condition show that for both normal and hypothetical accident conditions of transport, the stresses are within allowable values. (author)

1986-06-16

108

Relationship between the Effectiveness of Arthrocentesis under Sufficient Pressure and Conditions of the Temporomandibular Joint  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background. The purpose of this study is to investigate the conditions of the temporomandibular joint relative to the effectiveness of an arthrocentesis-like enforced manipulation technique followed by irrigation under high pressure in patients with closed lock. Methods. We performed arthroscopic examination and manipulation followed by irrigation as the initial treatment in 50 joints with closed lock. Relationship between the effectiveness of the procedure and conditions of the temporomandib...

Yura, Shinya; Ooi, Kazuhiro; Izumiyama, Yuri

2011-01-01

109

Study on vortex cavitation in a compact fast reactor. Effects of system pressure on inception condition  

International Nuclear Information System (INIS)

A compact sodium reactor is designed as a commercialized fast reactor cycle system. A 1/10 scaled water experiment was performed to optimize flow in an upper plenum of the reactor vessel, because of high flow velocity resulted from the compacted vessel. In the experiment, vortex cavitation was found at the hot leg inlet because of high velocity in the hot leg pipe (9.4m/s in the design). To evaluate cavitation inception condition of the commercialized reactor, we use the cavitation number k in order to consider the difference of system pressures (0.1MPa in the experiment and 0.3MPa in the design). The minimum pressure at the vortex center will depend on vortex core radius (size of forced vortex region). It is related to axial velocity gradient and fluid viscosity in theory of the Burger's stretched vortex model. We carried out a basic water experiment to investigate the influence of system pressure and fluid viscosity on the vortex cavitation. The cavitation number at the inception of vortex cavitation slightly increased according to the increase of the system pressure. It means that the vortex cavitation occurs easily under higher pressure condition as compared with the similar condition of cavitation number with lower pressure. However the increase was less than 30% when the system pressure was varied from 0.1 to 0.3MPa. The influence of fluid viscosity was examined by change of fluid temperature. Velocity distribution around the vortex was also measured to see the structure of vortex. (authors)

2005-01-01

110

Multiple uncontrolled conditions and blood pressure medication intensification: an observational study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Multiple uncontrolled medical conditions may act as competing demands for clinical decision making. We hypothesized that multiple uncontrolled cardiovascular risk factors would decrease blood pressure (BP) medication intensification among uncontrolled hypertensive patients. Methods We observed 946 encounters at two VA primary care clinics from May through August 2006. After each encounter, clinicians recorded BP medication intensification (BP...

2010-01-01

111

Effect of Low Pressure End Conditions on Steam Power Plant Performance  

Directory of Open Access Journals (Sweden)

Full Text Available Most of the electricity produced throughout the world today is from steam power plants and improving the performance of power plants is crucial to minimize the greenhouse gas emissions and fuel consumption. Energy efficiency of a thermal power plant strongly depends on its boiler-condenser operating conditions. The low pressure end conditions of a condenser have influence on the power output, steam consumption and efficiency of a plant. Hence, the objective this paper is to study the effect of the low pressure end conditions on a steam power plant performance. For the study each component was modelled thermodynamically. Simulation was done and the results showed that performance of the condenser is highly a function of its pressure which in turn depends on the flow rate and temperature of the cooling water. Furthermore, when the condenser pressure increases both net power output and plant efficiency decrease whereas the steam consumption increases. The results can be used to run a steam power cycle at optimum conditions.

Ali Syed Haider

2014-07-01

112

Experimental study of the pressure fluctuations in a pump turbine at large partial flow conditions  

Science.gov (United States)

Frequent shifts of output and operating mode require a pump turbine with excellent stability. Current researches show that large partial flow conditions in pump mode experience positive-slope phenomena with a large head drop. The pressure fluctuation at the positive slope is crucial to the pump turbine unit safety. The operating instabilities at large partial flow conditions for a pump turbine are analyzed. The hydraulic performance of a model pump turbine is tested with the pressure fluctuations measured at unstable operating points near a positive slope in the performance curve. The hydraulic performance tests show that there are two separated positive-slope regions for the pump turbine, with the flow discharge for the first positive slope from 0.85 to 0.91 times that at the maximum efficiency point. The amplitudes of the pressure fluctuations at these unstable large partial flow conditions near the first positive slope are much larger than those at stable operating condtions. A dominant frequency is measured at 0.2 times the impeller rotational frequency in the flow passage near the impeller exit, which is believed to be induced by the rotating stall in the flow passage of the wicket gates. The test results also show hysteresis with pressure fluctuations when the pump turbine is operated near the first positive slope. The hysteresis creates different pressure fluctuations for those operation points even though their flow rates and heads are similar respectively. The pressure fluctuation characteristics at large partial flow conditions obtained by the present study will be helpful for the safe operation of pumped storage units.

Ran, Hongjuan; Luo, Xianwu; Zhu, Lei; Zhang, Yao; Wang, Xin; Xu, Hongyuan

2012-11-01

113

Numerical simulation of pressure fluctuation in 1000MW Francis turbine under small opening condition  

Science.gov (United States)

In order to study the cause of abnormal vibration in large Francis turbine under small opening condition, CFD method was adopted to analyze the flow filed and pressure fluctuation. Numerical simulation was performed on the commercial CFD code Ansys FLUENT 12, using DES method. After an effective validation of the computation result, the flow behaviour of internal flow field under small opening condition is analyzed. Pressure fluctuation in different working mode is obtained by unsteady CFD simulation, and results is compared to study its change. Radial force fluctuation is also analyzed. The result shows that the unstable flow under small opening condition leads to an increase of turbine instability in reverse pump mode, and is one possible reason of the abnormal oscillation.

Gong, R. Z.; Wang, H. G.; Yao, Y.; Shu, L. F.; Huang, Y. J.

2012-11-01

114

Numerical simulation of pressure fluctuation in 1000MW Francis turbine under small opening condition  

International Nuclear Information System (INIS)

In order to study the cause of abnormal vibration in large Francis turbine under small opening condition, CFD method was adopted to analyze the flow filed and pressure fluctuation. Numerical simulation was performed on the commercial CFD code Ansys FLUENT 12, using DES method. After an effective validation of the computation result, the flow behaviour of internal flow field under small opening condition is analyzed. Pressure fluctuation in different working mode is obtained by unsteady CFD simulation, and results is compared to study its change. Radial force fluctuation is also analyzed. The result shows that the unstable flow under small opening condition leads to an increase of turbine instability in reverse pump mode, and is one possible reason of the abnormal oscillation.

2012-11-26

115

Impact of Mental and Physical Stress on Blood Pressure and Pulse Pressure under Normobaric versus Hypoxic Conditions  

Science.gov (United States)

Objective Hypobaric hypoxia, physical and psychosocial stress may influence key cardiovascular parameters including blood pressure (BP) and pulse pressure (PP). We investigated the effects of mild hypobaric hypoxia exposure on BP and PP reactivity to mental and physical stress and to passive elevation by cable car. Methods 36 healthy volunteers participated in a defined test procedure consisting of a period of rest 1, mental stress task (KLT-R), period of rest 2, combined mental (KLT-R) and physical task (bicycle ergometry) and a last period of rest both at Graz, Austria (353 m asl) and at the top station Dachstein (2700 m asl). Beat-to-beat heart rate and BP were analysed both during the test procedures at Graz and at Dachstein and during passive 1000 m elevation by cable car (from 1702 m to 2700 m). Results A significant interaction of kind of stress (mental vs. combined mental and physical) and study location (Graz vs. Dachstein) was found in the systolic BP (p?=?.007) and PP (p?=?.002) changes indicating that during the combined mental and physical stress task sBP was significantly higher under hypoxic conditions whereas sBP and PP were similar during mental stress both under normobaric normoxia (Graz) and under hypobaric hypoxia (Dachstein). During the passive ascent in cable car less trivialization (psychological coping strategy) was associated with an increase in PP (p?=?.004). Conclusion Our data show that combined mental and physical stress causes a significant higher raise in sBP and PP under hypoxic conditions whereas isolated mental stress did not affect sBP and PP under hypoxic conditions. PP-reaction to ascent in healthy subjects is not uniform. BP reactions to ascent that represents an accumulation of physical (mild hypobaric hypoxia) and psychological stressors depend on predetermined psychological traits (stress coping strategies). Thus divergent cardiovascular reactions can be explained by applying the multidimensional aspects of the biopsychosocial concept.

Trapp, Michael; Trapp, Eva-Maria; Egger, Josef W.; Domej, Wolfgang; Schillaci, Giuseppe; Avian, Alexander; Rohrer, Peter M.; Horlesberger, Nina; Magometschnigg, Dieter; Cervar-Zivkovic, Mila; Komericki, Peter; Velik, Rosemarie; Baulmann, Johannes

2014-01-01

116

Effect of pressure on the chromatographic separation of enantiomers under reversed-phase conditions.  

Science.gov (United States)

Commercially available ultra high pressure liquid chromatography (UHPLC) equipment offers the ability to explore the influence of backpressure on chromatographic separations. However, the influence of pressure on the chromatographic separation of enantiomers on chiral stationary phases remains largely unexplored. In this investigation we surveyed the effects of pressure on the separation of enantiomers using several reversed-phase chiral stationary phases. The experiments were conducted at constant flow rate and column temperature, using isocratic conditions. The only variable parameter was pressure, which was adjusted using a post-column backpressure regulator. For the separation of enantiomers on chiral stationary phases, an increase in pressure from approximately 2000psi (138bar) to approximately 8000psi (552bar) at constant flow rate and temperature led to an increase of retention factors for some analytes and a decrease for others. Achiral separations on a C-18 stationary phase always led only to an increase of retention factor. Interestingly, changes in pressure led to small changes in enantioselectivity during reversed-phase chiral separation of enantiomers, suggesting that such studies may be of value for better understanding the mechanisms underlying chromatographic enantioseparation. PMID:24928149

Makarov, Alexey A; Regalado, Erik L; Welch, Christopher J; Schafer, Wes A

2014-07-25

117

Improvement of the RELAP5 subcooled boiling model for low pressure conditions  

International Nuclear Information System (INIS)

The RELAP5/MOD3.2.2 Gamma code was assessed against low pressure subcooled boiling experiments performed by Zeitoun and Shoukri [1] in a vertical annulus. The predictions of subcooled boiling bubbly flow showed that the present version of the RELAP5 code underestimates the void fraction growth along the tube. To improve the void fraction prediction at low pressure conditions a set of model changes is proposed, which includes modifications of bubbly-slug transition criterion, drift-flux model, interphase heat transfer coefficient and wall evaporation modeling. The improved experiment predictions with the modified RELAP5 code are presented and analysed. (author)

2000-09-11

118

Local conditions separating expansion from collapse in spherically symmetric models with anisotropic pressures  

Science.gov (United States)

We investigate spherically symmetric spacetimes with an anisotropic fluid and discuss the existence and stability of a separating shell dividing expanding and collapsing regions. We resort to a 3+1 splitting and obtain gauge invariant conditions relating intrinsic spacetime quantities to properties of the matter source. We find that the separating shell is defined by a generalization of the Tolman-Oppenheimer-Volkoff equilibrium condition. The latter establishes a balance between the pressure gradients, both isotropic and anisotropic, and the strength of the fields induced by the Misner-Sharp mass inside the separating shell and by the pressure fluxes. This defines a local equilibrium condition, but conveys also a nonlocal character given the definition of the Misner-Sharp mass. By the same token, it is also a generalized thermodynamical equation of state as usually interpreted for the perfect fluid case, which now has the novel feature of involving both the isotropic and the anisotropic stresses. We have cast the governing equations in terms of local, gauge invariant quantities that are revealing of the role played by the anisotropic pressures and inhomogeneous electric part of the Weyl tensor. We analyze a particular solution with dust and radiation that provides an illustration of our conditions. In addition, our gauge invariant formalism not only encompasses the cracking process from Herrera and co-workers but also reveals transparently the interplay and importance of the shear and of the anisotropic stresses.

Mimoso, José P.; Le Delliou, Morgan; Mena, Filipe C.

2013-08-01

119

Nonlinear analysis for a double-channel natural circulation loop under low-pressure conditions  

International Nuclear Information System (INIS)

On the basis of the homogeneous flow model and Galerkin nodal approximation method, a numerical model for a double-channel natural circulation loop is developed. The calculated steady-state results provide a reasonable agreement against the experimental data in the high power region but over-estimate in the low power region under unequal heating conditions for the double channels. Nonlinear dynamics and stability boundary of the system are also analyzed under equal heating power conditions. Two unstable regions, Type-I and Type-II instabilities, are found in this system. In the low inlet subcooling region, the oscillations of the equal-heating double channels are out-of-phase under low power conditions due to the effect of the gravitational pressure drop; however, are in-phase under high power conditions resulting from the effect of the two-phase frictional pressure drop. On the other hand, in the high inlet subcooling region, these double channels are both nearly in-phase at Type-I and Type-II stability boundaries, where the two-phase frictional drop is dominate for the channel pressure drop. (author)

2003-04-20

120

Optimal heat rejection pressure in transcritical carbon dioxide air conditioning and heat pump systems  

DEFF Research Database (Denmark)

Due to the urgent need for environmentally benign refrigerants, the use of the natural substance carbon dioxide in refrigeration systems has gained more and more attention. In systems such as automobile air-conditioners and heat pumps, owing to the relatively high heat rejection temperatures, the cycles using carbon dioxide as refrigerant will have to operate in the transcritical area. In a transcritical carbon dioxide system, there is an optimal heat rejection pressure that gives a maximum COP. In this paper, it is shown that the value of this optimal heat rejection pressure mainly depends on the outlet temperature of the gas cooler, the evaporation temperature and the efficiency of the compressor. General correlations for this optimal heat rejection pressure were derived based on cycle simulations. The correlations presented in this paper provide a basisfor designing transcritical carbon dioxide air conditioning or heat pump systems and for intelligent controlling such systems.

Liao, Shengming; Jakobsen, Arne

1998-01-01

 
 
 
 
121

Cavitation and primary atomization in real injectors at low injection pressure condition  

Science.gov (United States)

This experimental work investigates the influence of the geometry of GDI devices on primary atomization processes under low injection pressure and reduced back pressure. These pressure conditions ensure cavitating flows and observable atomization processes. Measurements include mass flux, structure velocity from high-speed visualizations and spray characterization with a laser diffraction technique. Super-cavitation regime and cavitation string, which have their own influence on the mass flux, develop independently in different injector regions. These regimes impact the flow pattern in the orifice and the subsequent atomization process. A possible interaction between cavitation string and super-cavitation is found to promote a hydraulic-flip-like regime and to deteriorate atomization quality. As far as the geometry of the injector is concerned, the profile of the orifice inlet and the roughness of the sac volume region are found to be important geometrical characteristics.

Dumouchel, Christophe; Leboucher, Nicolas; Lisiecki, Denis

2013-06-01

122

The Rheological Properties of Oil-Based Mud under High Pressure and High Temperature Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available

Designing a proper drilling fluid that can function properly under the conditions of High-Pressure, High-Temperature (HP/HT operations is very challenging. Among these challenges is the alteration of the rheological properties of drilling fluid due to the high temperature and high pressure (Ibeh et. al, 2007. This work investigates the rheological behavior of oil-based drilling fluids with different properties at Ultra-HP/HT conditions using a state-of-the-art viscometer capable of measuring drilling fluids properties up to 600°F and 40,000 psi. For this purpose, two actual oil based mud samples used by industry with the same mud weight (12.5 ppg were chosen to carry out a matrix of experiments. The results of this study led to concluding that the viscosity, yield point and gel strength decrease with increasing temperature (until the mud sample fails, for oil-based mud with regular formulation. This behavior is the result of the thermal degradation of the solid, polymers, and other components of the mud samples and the expansion of the molecular distances which will lower the resistance of the fluid to flow and, hence, its viscosity, yield point, and gel strength. Moreover, it is concluded that the viscosity and yield point increase as the pressure increases. Pressure’s effect on these parameters, however, is more apparent at low temperature (below failure point, for oil-based mud with regular formulation.

Key words: High pressure high temperature; Oil-based mud; Rheology; Rheological properties

Mahmood Amani

2012-07-01

123

High temperature, high pressure absorption spectra of uranyl chloride solutions under shock conditions  

International Nuclear Information System (INIS)

A technique for photographing the absorption spectra of solutions under shock wave conditions was developed. A photograph of the spectrum of a uranyl nitrate solution exposed to a shock wave of 75 kbar showed the absorption to extend beyond 500 mn, the long wavelength limit for uranyl solutions under ordinary conditions. It was found that at room temperature pressure up to 6 kbar had no appreciable effect on absorption. An analysis of the spectrum of uranyl perchlorate solutions has been published. The intensity of very weak absorption bands increased when the solution was heated to 950C, and they were interpreted as hot bands due to absorption from an excited ground state. New absorption measurements made on uranyl solutions heated to 2500C at low pressure are presented and an interpretation of the effect observed in the shock experiments is offered

1983-07-25

124

Inelastic X-ray scattering experiments at extreme conditions: high temperatures and high pressures  

Directory of Open Access Journals (Sweden)

Full Text Available In this article, we review the present status of experimental techniques under extreme conditions of high temperature and high pressure used for inelastic X-ray scattering (IXS experiments of liquid metals, semiconductors, molten salts, molecular liquids, and supercritical water and methanol. For high temperature experiments, some types of single-crystal sapphire cells were designed depending on the temperature of interest and the sample thickness for the X-ray transmission. Single-crystal diamond X-ray windows attached to the externally heated high-pressure vessel were used for the IXS experiment of supercritical water and methanol. Some typical experimental results are also given, and the perspective of IXS technique under extreme conditions is discussed.

S.Hosokawa

2008-03-01

125

A modified resistance equation for modeling underwater spark discharge with salinity and high pressure conditions  

Science.gov (United States)

This work investigates the performance of underwater spark discharge relating to bubble growth and decay under high pressure and with salinity conditions by introducing a modified form of the resistance equation. Here, we study salinity influence on circuit parameters by fitting the experimental data for which gap resistance is much larger in conductive water than in dielectric water. Accordingly, the resistance equation is modified by considering the influence of both plasma and its surrounding liquid. Thermal radiation effect of the bubble is also studied by comparing two different radiation models. Numerical results predict a larger bubble pressure for saline water but a reduced size and a smaller bubble cycle at a greater water depth. Such study may be useful in many saltwater applications, including that for deep sea conditions.

Zhao, Pengfei; Roy, Subrata

2014-05-01

126

A SiC high-temperature Pressure Sensor Operating in Severe Condition  

Directory of Open Access Journals (Sweden)

Full Text Available The tranditional MEMS pressure sensor based on Silicon (Si material has not been suitable for operating in severe condition such as high-temperature (>500°C. However, as an alternative material, Silicon Carbide (SiC can be used in hash environment due to its unique properties. Hence this paper presents a touch mode capacitive pressure sensor with double-notches structure, which employs a special SiC-AlN-SiC sandwich structure to achieve high-accuracy pressure measurement in high-temperature environment. In order to get the relation of capacitance and external pressure, the large deflection theory is applied in simulation analysis of the diaphragm deformation. At the same time, the sandwich structure and technical process of the sensor are studied in the paper. The results showed that the sensor has excellent high-temperature performance due to application of SiC and AlN materials, and the sensor has higher sensitivity and longer linear range than traditional single-cavity structure. Consequently, the sensor can be applied to accuracy pressure measuremet in high-temperature and harsh environment.

Guoqing Hu

2012-12-01

127

The effect of pressure on the electrical conductivity of olivine under the hydrogen-rich conditions  

Science.gov (United States)

The influence of pressure on the hydrogen-assisted electrical conductivity in olivine has been studied under conditions of 4-10 GPa and 873-1273 K. Synthetic polycrystalline olivine samples with the water content of 160 ppm wt (Paterson calibration) were used and the electrical conductivity was determined from the results of the impedance spectroscopy. We found that the pressure reduces the hydrogen-assisted electrical conductivity, but its magnitude is small: between 4 and 10 GPa, the difference is a factor of ?2.5 for the same water content and temperature. The pressure dependence is characterized by a negative activation volume and the negative dependence of the pre-exponential factor on pressure. Such anomalous behavior is explained by a model where hydrogen-related defect is considered as a weak inclusion in a strong matrix. We use these new data to calculate the electrical conductivity contrast at the 410-km discontinuity. We found that if the water content of the mantle does not change with depth, there should be a large (a factor of ?10) drop in conductivity from above to below the 410-km discontinuity. In contrast, geophysically inferred electrical conductivity increases at 410-km suggesting the increase in water content from above to below the 410-km discontinuity. The present results are used to compare several previous results obtained at different pressures. It was shown that our results agree well with most of previous studies but not with (Yoshino et al., 2009). Possible causes for this discrepancy are discussed.

Dai, Lidong; Karato, Shun-ichiro

2014-07-01

128

Entropy Generation in Pressure Gradient Assisted Couette Flow with Different Thermal Boundary Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present paper is concerned with an analytical study of entropy generation in viscous, incompressible Couette flow between a stationary plate and a moving plate. The flow induced by the moving plate is assisted by a constant pressure gradient along the flow direction. Four different combinations of thermal boundary conditions are investigated: (a) plates at different temperatures, (b) stationary plate at a fixed temperature and moving plate subjected to a constant heat flux, (c) stationary...

Abdul Aziz

2006-01-01

129

Natural Circulation Characteristics at Low-Pressure Conditions through PANDA Experiments and ATHLET Simulations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Natural circulation characteristics at low pressure/low power have been studied by performing experimental investigations and numerical simulations. The PANDA large-scale facility was used to provide valuable, high quality data on natural circulation characteristics as a function of several parameters and for a wide range of operating conditions. The new experimental data allow for testing and improving the capabilities of the thermal-hydraulic computer codes to be used for treating natural c...

Domenico Paladino; Max Huggenberger; Frank Schäfer

2008-01-01

130

Durability of polydicyclopentadiene under high temperature, high pressure and seawater (offshore oil production conditions)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the offshore industry polymer coatings are widely used to ensure thermal insulation of steel pipes, and to avoid over-cooling of the hot oil inside. Because of very severe service conditions (i.e. high temperature, high pressure and presence of seawater) and an expected life time of 20 years, durability of these coatings is a major issue for this industry. Polypropylene and polyurethane are often used for this application, nevertheless these polymers have some limitations in terms of proce...

2013-01-01

131

Seismic-safe conditions of blasting near pressure pipe-lines during power installation construction  

International Nuclear Information System (INIS)

Seismic-safe conditions for performing drill-blasting operations in the vicinity of underground gas pipelines when constructing thermal- or nuclear power plants are discussed. It is shown that, for the determination of seismic-safe parameters, of drill-blasting operations, the maximum permissible level of seismic loads should be specified taking into account the mechanical properties of the pipeline.metal, structural parameters of the gas pipeline and the pressure of the medium transported. Besides, the seismic effect of the blast should be considered with regard to particular conditions of blasting and rock properties. The equations and diagrams used in the calculation are given

1980-01-01

132

A structural evaluation of the Shippingport reactor pressure vessel for transport impact conditions  

International Nuclear Information System (INIS)

The Shippingport Atomic Power Station in Shippingport, Pennsylvania, is being decommissioned and dismantled. This government-leased property will be returned, in a radiologically safe condition, to its owner. All radioactive material is being removed from the Shippingport Station and transported for burial to the DOE Hanford Reservation in Richland, Washington. The reactor pressure vessel (RPV) will be transported by barge to Hanford. This paper describes an evaluation of the structural response of the RPV to the normal and accident impact test conditions as required by the Code of Federal Regulations. 3 refs., 5 figs., 3 tabs

1989-07-23

133

Consideration of loading conditions initiated by thermal transients in PWR pressure vessels  

International Nuclear Information System (INIS)

This report describes the present state of PWR-plants in the Federal Republic of Germany with respect to - the design of the primary pressure boundary - the analysis of thermal transients and resulting loads - the material conditions and neutron fluence - the requirements for protection against fast fracture. The experimental and analytical research and development programs are delineated together with some foreign R and D programs. It is shown that the parameters investigated (loading condition, crack shape and orientation etc.) cover a broad range. Extensive analytical investigations are emphasized. (orig./RW)

1983-12-01

134

Modeling and Investigation of Electromechanical Valve Train Actuator at simulated Pressure conditions  

DEFF Research Database (Denmark)

In an electromechanical valve actuated engine, the valves are driven by solenoid-type actuators and cam-shaft is eliminated. Control of each valve provides flexibility in valve timings over all engine conditions and achieves the benefits of variable valve timing(VVT). This paper is about investigation of Electro-mechanical actuator at simulated pressure conditions for a single cylinder engine. For this purpose, a scaled down actuator with reduced armature lift and high stiffness springs are being used. Experiments are conducted to measure valve release timings, transition times and contact velocities. Furthermore, discussion about the spring, magnetic, exhausts gas forces and their ability to actuate the system as desired.

Habib, Tufail

2012-01-01

135

BWR In-Core Monitor Housing Replacement Under Dry Condition of Reactor Pressure Vessel  

International Nuclear Information System (INIS)

A new method of In-Core Monitor Housing replacement has been successfully applied to Tokai Unit 2 (BWR with 1100 MWe) in April of 2001. It was designed to replace a housing under dry condition of reactor pressure vessel (RPV): this enabled the elimination of water filled-up and drained processes during the replacement procedure resulting in the reduction of implementation schedule. To realize the dry condition, the radiation shields were placed in the RPV and the hollow guide pipe (GP) was adopted to transfer the apparatuses from the top to the bottom work area. (authors)

2002-04-14

136

Flare-out condition of a Morris-Thorne wormhole and finiteness of pressure  

Science.gov (United States)

A wormhole is defined as a topological structure with a throat connecting two asymptotically-flat spaces. In order to have and maintain the structure of the wormhole, a geometrical flare-out condition, i.e., a minimal size at throat, needs to be satisfied. In the case of a Morris-Thorne-type wormhole, the condition is given by surface tension which is huge compared to the energy density times the square of the light speed. In this paper, we re-considered the flare-out condition for a wormhole by using the Einstein equation, checked the finiteness of the pressure, and investigated its physical meaning. We also derived the power-law form of the flare-out condition.

Kim, Sung-Won

2013-11-01

137

Wall pressure and conditional flow structures downstream of a reattaching flow region  

International Nuclear Information System (INIS)

Highlights: ? Investigation of the separating and reattaching flow over a thick plate. ? Analysis of the evolution of the large scale vortices downstream of the reattachment. ? Stochastic estimation of the velocity correlated with the fluctuating wall pressure. ? Use of swirling strength and FTLE to detect and characterize the coherent structures. ? Observation of a rapid loss of coherence of vortices downstream of the reattachment. - Abstract: The separating and reattaching flow over a thick plate with sharp angle at Re = 80,000 is investigated using pressure and HS-PIV measurements. After having studied the mean flow properties, which are found in good agreement with the literature, a particular emphasis is given concerning the eduction and the analysis of the evolution of the large scale vortices downstream of the reattachment. This is done using an adapted multi-time and multichannel stochastic estimation of the velocity correlated with the fluctuating wall pressure. Swirling strength and Finite Time Lyapunov Exponents are then used in order to detect and characterize the structures and their dynamics. Conditional statistics based on the feature longitudinal position are computed in order to educe intensity, size, position and convection velocity of each conditional feature. A rapid longitudinal decrease of the fluctuating kinetic energy carried by these conditional structures has been observed, highlighting their rapid loss of coherence downstream mean reattachment.

2012-06-01

138

Wall pressure and conditional flow structures downstream of a reattaching flow region  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer Investigation of the separating and reattaching flow over a thick plate. Black-Right-Pointing-Pointer Analysis of the evolution of the large scale vortices downstream of the reattachment. Black-Right-Pointing-Pointer Stochastic estimation of the velocity correlated with the fluctuating wall pressure. Black-Right-Pointing-Pointer Use of swirling strength and FTLE to detect and characterize the coherent structures. Black-Right-Pointing-Pointer Observation of a rapid loss of coherence of vortices downstream of the reattachment. - Abstract: The separating and reattaching flow over a thick plate with sharp angle at Re = 80,000 is investigated using pressure and HS-PIV measurements. After having studied the mean flow properties, which are found in good agreement with the literature, a particular emphasis is given concerning the eduction and the analysis of the evolution of the large scale vortices downstream of the reattachment. This is done using an adapted multi-time and multichannel stochastic estimation of the velocity correlated with the fluctuating wall pressure. Swirling strength and Finite Time Lyapunov Exponents are then used in order to detect and characterize the structures and their dynamics. Conditional statistics based on the feature longitudinal position are computed in order to educe intensity, size, position and convection velocity of each conditional feature. A rapid longitudinal decrease of the fluctuating kinetic energy carried by these conditional structures has been observed, highlighting their rapid loss of coherence downstream mean reattachment.

Sicot, C., E-mail: christophe.sicot@ensma.fr [Institut Pprime, UPR CNRS 3346, ENSMA, Universite de Poitiers, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Perrin, R.; Tran, T.T.; Boree, J. [Institut Pprime, UPR CNRS 3346, ENSMA, Universite de Poitiers, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France)

2012-06-15

139

High-pressure behavior of cristobalite under quasi-hydrostatic conditions  

Science.gov (United States)

Cristobalite is a high-temperature, low-pressure polymorph of SiO2. It is comprised of a framework of SiO4 tetrahedra, like many other low-pressure silica polymorphs, e.g. quartz tridymite, or coesite. Its cubic form known as ?-cristobalite crystallizes above 1470 ° C and at atmospheric pressure. The tetragonal ?-phase is a metastable polymorph which appears upon cooling of the cubic ?-cristobalite to ambient temperature and it can be found in natural acidic volcanic rocks. High-pressure behavior of ?-cristobalite is of interest form the geological standpoint because it was experimentally observed that under elevated pressures and at ambient temperature this polymorph with 4-fold coordinated silicon can transform to seifertite - a lower mantle phase with octahedrally coordinated Si. The transformational sequence is as follows. The tetragonal ?-cristobalite transforms to a monoclinic cristobalite II near ~1.5 GPa upon hydrostatic compression. The structure of this higher-pressure polymorph was recently solved. Above ~10 GPa cristobalite II is found to transforms to cristobalite X-I. Apart from the recent determination of the unit cell parameters, the structure of the cristobalite X-I still remains unknown. Further compression of cristobalite X-I above pressures exceeding ~35 GPa leads to formation of cristobalite X-II, which is the polymorph reported to have the structure of seifertite. However, there is a large discrepancy among various experimental observations regarding the pressure at which this transition takes place. Motivated by the recent studies, we aim at understanding how the structure of this "bridging phase", cristobalite X-I, is evolving under pressure and how it transforms to the seifertite phase. We performed in-situ single crystal Raman spectroscopy and X-ray diffraction up to 82 GPa in steps of 3-5 GPa. We used diamond-anvil cells with 250 ?m diamond culet size and neon as the pressure-transmitting medium. In-situ Raman spectra indicated the phase transition to cristobalite II near 1.5 GPa and the formation of the X-I phase above 10 GPa, in agreement with previous studies. This high-pressure phase persists up the highest pressures achieved and it is not quenchable - upon decompression it retransforms into a phase with Raman spectra very similar to that of the starting ?-cristabolate. Single crystal X-ray diffraction data were collected at Extreme Conditions Beamline P02.2 at Petra III. We confirmed the phase transition to cristobalite II and further above 10 GPa to the phase X-I. Indexing of the diffraction patterns of the phase X-I collected at 17 GPa yields a primitive monoclinic unit cell with a = 6.5899(9) Å, b = 4.0493(6) Å, c = 6.841(8) Å, ? = 98.15(3)° and the most likely space groups P21/c or P21/n. A preliminary structure analysis reveals that all Si atoms are octahedrally coordinated at this pressure. Single-crystal X-ray diffraction data from experiments at higher pressures are currently being analyzed.

Cernok, Ana; Bykova, Elena; Liermann, Hanns-Peter; Dubrovinsky, Leonid

2014-05-01

140

Equation of state for solids with high accuracy and satisfying the limitation condition at high pressure  

International Nuclear Information System (INIS)

An equation of state (EOS) with high accuracy is proposed to strictly satisfy the Fermi gas limitation condition at high pressure. The EOS (SJX EOS) is a modification of the effective Rydberg (ER2) EOS. Instead of Holzapfel's method to directly modify the ER2 EOS, one modifying term is added to the ER2 EOS to make it not only satisfy the high pressure limitation condition, but also to avoid the disadvantages occurring in the Holzapfel and 'adapted polynomial expansion of the order 3' (AP3) EOSs. The two-parameter ER2, Holzapfel, and three-parameter SJX, AP3, Kumari and Dass (KD) EOSs are applied to 50 materials to fit all experimental compression data available. The five EOSs also are applied to 37 of the 50 materials to fit experimental compression data at low-pressure ranges. The results show that for all pressure ranges the AP3 EOS gives the best fitting results; the SJX, ER2, Holzapfel and KD EOSs sequentially give inferior results. Otherwise, it is shown that the values of B0, B0' and B0'' are different for different EOSs and also, within one EOS, for high and low-pressure ranges. The SJX EOS gives the best consistency between the values obtained by fitting all experimental data available, and the experimental data at low-pressure ranges, respectively. The AP3 EOS gives the worst results. The differences of the values of B0, B0' and B0'' obtained for the ER2, Holzapfel and KD EOSs with those obtained for the SJX EOS are large at high-pressure ranges, but decrease at low-pressure ranges. At present, the newest experimental compression data, within the widest compression range, are available for solid n-H2. The values of B0, B0' and B0'' fitted by using the SJX EOS are almost in agreement with these experimental data. The ER2 EOS gives inferior values, and other EOSs give fairly bad results. For the predicted compression curves and the cohesive energy, the SJX EOS gives the best results; the AP3 EOS gives the worst results, even for many solids the AP3 EOS cannot give physically correct results for the cohesive energy. The analysis shows that for such solids, the variation of pressure and energy versus compression ratio calculated by using the AP3 EOS would oscillate, physically incorrectly. Although the AP3 EOS has the best fitting ability to the pressures, it has the worst predicting ability, and fails to be a universal EOS. The SJX EOS is recommended and can be taken as a candidate of universal EOSs to predict compression curves of solids in a wide pressure range only using the values of B0, B0' and B0'' obtained from low-pressure data

2006-01-31

 
 
 
 
141

Change of permeability caused by 2011 Tohoku earthquake detected from pore pressure monitoring  

Science.gov (United States)

Earthquake-induced groundwater changes which are the pre- and co-seismic changes have been long reported (e.g. Roeloffs, 1996). For example, 1995 Kobe earthquake, water inflow into observation tunnel changed at Rokko (Fujimori et al., 1995), at the times of 1964 Alaska earthquake (M8.6) (Coble, 1967) and 1999 Taiwan Chi-Chi earthquake (M7.6) (Chia et al., 2001), groundwater leve were fluctuated. The shaking of seismic waves and crack formation by crustal deformation are proposed as one causes but the mechanism is controversial. We are monitoring pore pressure from 2005 to measure the stress changes at Kamioka mine, Gifu prefecture, central Japan. Barometric pressure and strain are observed to correct the pore pressure data. In general, the pore pressure changes associate with the meteorological effects, Earth tides and crustal deformation. Increase of pore pressure depends on the precipitation which flows into the ground. Especially, snow effects are bigger than the usual rainfall because our observation site has heavy snow in winter season. Melted snow flows in the ground and pore pressure increases at the March to April every year. When the 2011 Tohoku earthquake (M9.0) occurred, pore pressure remarkably decreased because the permeability increases by crustal deformation at Kamioka region. Thus, we estimated the hydraulic diffusivity before and after the earthquake from pore pressure response to crustal deformation. We made separated analyses on three frequency bands. First is the high frequency band, especially, seismic response. Second is response to Earth tides. Third frequency band is that of barometric response which is lower than other two bands. At high frequency band, we confirmed that the deformation occurred under undrained condition and estimated the bulk modulus from pore pressure and strain data. Next, tidal response is extracted from pore pressure which applied to every three months data of pore pressure, barometric pressure and strain. Time window shifted every one day. As a result, amplitude of O1 and M2 constituents decreased after the Tohoku earthquake. M2 and O1 amplitudes were 0.575 hPa and 0.277 hPa before the earthquake, and decreased to 0.554 hPa and 0.184 hPa after the earthquake respectively. The phase between pore pressure and strain, changed after the event and soon recovered. We estimated the hydraulic diffusivity from the change in ratio of tidal response. We have no strain data due to apparatus problem, so we used synthetic strain. From one-dimensional diffusion equation and poroelastic constitutive relations, we could approximate the relation between pore pressure and strain by the exponential curve. Estimated hydraulic diffusivity of preseismic period is 8.0 m2/s and postseismic period is 19 m2/s, and these results correspond to pore pressure decreases. In the case of the barometric pressure response, we made the spectrum analysis and estimated the hydraulic diffusivity. The results from three frequency domain bands were integrated to show how the hydraulic diffusivity depends on to frequency.

Kinoshita, C.; Kano, Y.; Ito, H.

2013-12-01

142

Correction of particulate matter concentrations to reference temperature and pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

The 1997 revisions to the particulate matter NAAQS included changes in the reporting method of observed concentrations. Pollutant concentration data contained in EPA`s Aerometric Information Retrieval System (AIRS) prior to the 1997 revisions had been required to be reported in units corrected to standard temperature and pressure (25{degree} C, 760 mm Hg). This requirement was removed so that, in the new regulations, the particulate matter data will be reported to AIRS at local temperature and pressure. This work analyzes the impact of this revision to the spatial and temporal pattern of PM10 concentrations. The influence of pressure and temperature individually on the correction of US PM10 concentrations was first examined over a seasonal time scale. The two correction factors were then combined to produce a total correction factor and, subsequently, uncorrected PM10 concentration maps at local conditions were derived. The temperature correction was further inspected for purposes of determining differences between quarterly and monthly aggregations. Particulate matter concentrations expressed in terms of local pressure may be between 10 and 25 percent lower than those reported at standard pressure with the largest decreases occurring in the high elevation areas of the western US The temperature correction is most influential in the Northeast and Upper Midwest during the cold months with PM concentrations up to 10% higher than those reported at standard temperature. Combing the temperature and pressure corrections results in PM10 increases up to 5% in the Northeast and Upper Midwest during the winter and decreases up to 25% in the West, with the summer months experiencing greater decreases than the winter.

Falke, S.R.; Husar, R.B. [Washington Univ., St. Louis, MO (United States). Center for Air Pollution Impact and Trend Analysis

1998-12-31

143

The Influence of Collar on Surge Pressure Caused by the Drill String Inertia Force Under Closed Pipe Condition  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The study of surge pressure is of significant importance for the safety of drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure calculation. In this paper, based on closed pipe condition, a steady-state calculation model for surge pressure caused by drill string inertia force is developed considering the presence of collar. In the end a case study is presented t...

2013-01-01

144

Experimental investigation of symmetric and asymmetric heating of pressure tube under accident conditions for Indian PHWR  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer Circumferential temperature gradient for asymmetric heat-up was 400 Degree-Sign C. Black-Right-Pointing-Pointer At same pressure ballooning initiates at lower temperature in asymmetrical heat-up. Black-Right-Pointing-Pointer At 1 MPa ballooning initiated at 408 Degree-Sign C and with expansion rate of 0.005 mm/s. Black-Right-Pointing-Pointer At 2 MPa ballooning initiation at 330 Degree-Sign C and with expansion rate of 0.0056 mm/s. Black-Right-Pointing-Pointer For symmetrical heat-up strain rate was 10 times faster than asymmetric heat-up. - Abstract: In pressurized heavy water reactor (PHWR), under postulated scenario of small break Loss of Coolant Accident (LOCA) coincident with the failure of Emergency Core Cooling System (ECCS), a situation may arise under which reduction in mass flow rate of coolant through individual reactor channel can lead to stratified flow. Such stratified flow condition creates partial uncover of fuel bundle, which creates a circumferential temperature gradient over PT. The present investigation has been carried out to study thermo-mechanical behaviour of PT under asymmetric heating conditions for a 220 MWe PHWR. A 19-pin fuel simulator has been developed in which preferential heating of elements could be done by supplying power to the selected pins. The asymmetric heating of PT has been carried out at pressure 2 MPa and 1 MPa, respectively, by supplying power to upper region heating elements thus creating an half filled stratified flow conditions. The temperature difference up to 425 Degree-Sign C has been observed along top to bottom periphery of PT. A comparison is made between thermo-mechanical behaviour of PT under asymmetrical and symmetrical heat-up, expected from a large break LOCA condition. The radial expansion rate during symmetrical heating is found to be much faster as compared to that for asymmetric ballooning of PT at the same internal pressure. Integrity of PT is found to be maintained under both loading conditions. Heat sink around of test section, simulating moderator is found to be helpful in arresting the rise in temperature for both fuel pins and PT, thus establishing moderator as an effective heat sink under accident conditions.

Yadav, Ashwini K., E-mail: ashwinikumaryadav@gmail.com [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee-247667 (India); Majumdar, P., E-mail: pmajum@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India); Kumar, Ravi, E-mail: ravikfme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee-247667 (India); Chatterjee, B., E-mail: barun@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India); Gupta, Akhilesh, E-mail: akhilfme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee-247667 (India); Lele, H.G., E-mail: hglele@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

2013-01-15

145

Pneumatic burst test under 'upper shelf conditions' of a pressure vessel containing an axial defect  

International Nuclear Information System (INIS)

In a programme of burst tests carried out in the 1960's on model steel pressure vessels with through thickness axial cracks, pressurised with water, some vessels when tested at temperatures in the upper part of the Charpy transition range underwent intermittent crack propagation. Each jump in crack length was accompanied by a drop in pressure, followed by a further crack extension on again raising the pressure. This behavior became more pronounced at higher temperatures and crack lengths and was suspected to be due to the low compressibility of the pressurising water and bulging of the pressure vessel shell local to the crack. Consequently, Test V15T1 was carried out using gas as the pressurising medium in order to demonstrate unambiguously that unstable crack propagation can continue if the loading is such as to give constant or increasing stress conditions as the crack propagates, even at temperatures corresponding to ''upper shelf'' Charpy values. Analyses of the test are given using two fracture assessment methods. (author)

1983-01-01

146

Measurements of mixtures with carbon dioxide under supercritical conditions using commercial high pressure equipment  

Energy Technology Data Exchange (ETDEWEB)

There is a growing interest in studying physical properties of binary and multicomponent fluid mixtures with supercritical carbon dioxide (CO{sub 2}) over an extended range of temperature and pressure. The estimation of properties such as density, viscosity, saturation pressure, compressibility, solubility and surface tension of mixtures is important in design, operation and control as well as optimization of chemical processes especially in extractions, separations, catalytic and enzymatic reactions. The phase behaviour of binary and multicomponent mixtures with supercritical CO{sub 2} is also important in the production and refining of petroleum where mixtures of paraffin, naphthene and aromatics with supercritical fluids are often encountered. Petroleum fluids can present a complex phase behaviour in the presence of CO{sub 2}, where two-phase (VLE and LLE) and three phase regions (VLLE) might occur within ranges of supercritical conditions of temperature and pressure. The objective of this study is to develop an experimental methodology for measuring the phase behaviour of mixtures containing CO{sub 2} in supercritical regions, using commercial high-pressure equipment. (author)

Andrade, Luciana L.P.R. de; Rutledge, Luis Augusto Medeiros; Moreno, Eesteban L.; Hovell, Ian; Rajagopal, Krishnaswamy [Universidade Federal do Rio de Janeiro (LATCA-EQ-UFRJ), RJ (Brazil). Escola de Quimica. Lab. de Termodinamica e Cinetica Aplicada

2012-07-01

147

Void-fraction distribution under high-pressure boil-off conditions in rod bundle geometry  

International Nuclear Information System (INIS)

Void fractions in a simulated pressurized water reactor (PWR) core rod bundle geometry were measured under boil-off conditions covering pressures from 3 to 12 MPa and mass fluxes from 5 to 100 kg m"-"2 s"-"1, with a particular interest in void fractions at higher pressures and relatively high mass fluxes. Test results showed that the Chexal-Lellouche model predicts best the present (volume-averaged) void-fraction data among correlations and models examined in this study. The volume-averaged void fractions obtained from differential pressure measurements are systematically smaller than the chordally averaged void fractions obtained from gamma densitometer measurements. Local void fractions were measured in the same bundle for non-heated steam-water two-phase flow of 3 MPa by using an optical void probe. It was found that the difference between the volume-averaged and chordally averaged void fractions mentioned above can be explained qualitatively by a local void-fraction distribution in the bundle measured in the latter tests. ((orig.))

1994-09-15

148

Effect of Antecedent Conditions on Prediction of Pore-Water Pressure using Artificial Neural Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The effect of antecedent conditions on the prediction of soil pore-water pressure (PWP using Artificial Neural Network (ANN was evaluated using a multilayer feed forward (MLFF type ANN model. The Scaled Conjugate Gradient (SCG training algorithm was used for training the ANN. Time series data of rainfall and PWP was used for training and testing the ANN model. In the training stage, time series of rainfall was used as input data and corresponding time series of PWP was used as the target output. In the testing stage, data from a different time period was used as input and the corresponding time series of pore-water pressure was predicted. The performance of the model was evaluated using statistical measures of root mean square error and coefficient of determination. The results of the model prediction revealed that when antecedent conditions (past rainfall and past pore-water pressures are included in the model input data, the prediction accuracy improves significantly.

Muhammad Raza Ul Mustafa

2012-01-01

149

Core void fraction distribution under high-temperature high-pressure boil-off conditions  

International Nuclear Information System (INIS)

The prediction of void fraction distributions in a core under boil-off conditions is important for analyzing the core cooling performance during reactor accidents. In this work, boil-off experiments were conducted under high-temperature high-pressure conditions using PWR-type and tight-lattice type (p/d = 1.11) simulated fuel assembly test sections of the Two-Phase flow Test Facility (TPTF). Several existing void fraction correlations and models were assessed against the experimental data. As a result, it has become clear that: 1) while the Chexal-Lellouche model predicts best the present experimental data, the model has a tendency to underestimate void fraction at higher pressures; 2) no significant problems are found in the applicability of the tested correlations and models to the tight-lattice geometry; and 3) void fractions measured by single-beam gamma densitometers tend to be larger than those measured by differential pressure transducers due to the radial void fraction distribution. (author)

1993-01-01

150

Dynamic response of berea sandstone shock-loaded under dry, wet and water-pressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

A single-stage light-gas gun was used to perform shock-recovery experiments on Berea sandstone under dry, wet and hydrostatically water-pressurized conditions. The samples were impacted by flyer-plates to achieve stress levels in the range 1.3 to 9.8 GPa. The microstructure of the shocked samples was analyzed using scanning electron microscopy (SEM), laser particle analysis and X-ray computed microtomography (XCMT). The dry samples show strongly fragmented and irregularly fractured quartz grains with a considerably reduced porosity, whereas the wet and water-pressurized specimens show less grain damage and less porosity reduction. During shock compression the water in the pores distributes the stresses and therefore the contact force between the grains is reduced. The interaction between the grains during the shock process was modeled by explicitly treating the grain-pore structure using Smooth Particle Hydrodynamics (SPH) and the Discrete Element Method (DEM).

Carney, T C; Hagelberg, C R; Hilt, M; Nellis, W J; Swift, R P

1999-09-03

151

Sulphation of oil shale ash under atmospheric and pressurized combustion conditions  

International Nuclear Information System (INIS)

One of the main problems in conventional combustion boilers firing pulverized oil shale is the corrosion and fouling of heating surfaces, which is caused by sulphur compounds. Another major problem, from the environmental point of view, are the high SO2 emissions. Consequently, the amount of sulphur in flue gases must be reduced. One alternative to lower the SO2, concentration is the use of new technologies, such as pressurized fluidized bed combustion (PFBC). In FBC processes, the sulphur components are usually removed by the addition of limestone (CaCO3) or dolomite (CaCO3 x MgCO3) into the bed. The calcium in these absorbents react with SO2, producing solid CaSO4. However, when burning oil shale, there would be no need to add limestone or dolomite into the bed, due to the initially high limestone content in the fuel (molar ratio Ca/S =10). The capture of sulphur by oil shale ashes has been studied using a pressurized thermogravimetric apparatus (PTGA). The chosen experimental conditions were typical for atmospheric and pressurized fluidized bed combustion. Four different materials were tested - one cyclone ash from an Estonian oil shale boiler, two size fractions of Estonian oil shale and, one fraction of Israeli oil shale. The cyclone ash was found to be the poorest sulphur absorbent. In general, the results from the sulphur capture experiments under both atmospheric and pressurized fluidized bed conditions showed that the oil shale can capture not only its own sulphur but also significant amounts of additional sulphur from another fuel if the fuels are mixed together. (author)

1995-01-01

152

Dissolution of borosilicate glasses under repository conditions of pressure and temperature  

International Nuclear Information System (INIS)

This paper described laboratory experimental work in progress in the UK to examine the mechanisms of fluid buffered interactions of materials at possible repository temperatures and pressures and aims at proposing limiting temperature values for a disposal facility from the geochemist's viewpoint. At present work is concentrated on reconnaissance experiments on dissolution rates of the vitrified waste form and the changes in near-field granite surface chemistry and fissure properties which will have a bearing on nuclide adsorption immediately after release. The major conclusions: in all of the experiments the fluid state remained as liquid since temperatures never exceeded 3740C, under these subcritical conditions pressure decreases dissolution rate; the ability to extrapolate dissolution rate from values of 1000C to about 2000C, together with the maintenance of physical integrity indicate that the glasses studied are likely to be stable and predictable in leach behavior to temperatures well in excess of those currently being considered for disposal; Glass 209 dissolves more slowly over a wide pressure and temperature spectrum than does glass 189, although the latter is easier to fabricate; dissolution rate decreases with increasing time. The principal conclusions of this study so far is that experimental application of realistic repository hydrothermal PT conditions indicate for the first time that current formulations of borosilicate glass would appear to provide for an adequate waste disposal medium which would maintain stability and predictable behavior over a wider pressure and temperature spectrum than previously realized, allowing sme latitude in both pre-disposal storage period and eventual loading at the time of disposal

1979-11-29

153

Effects of Soret and Dufour Diffusion on Conditional Expectations in Isotropic Turbulent Mixing at Supercritical Pressure  

Science.gov (United States)

Direct Numerical Simulations (DNS) of binary mixing in stationary compressible isotropic turbulence are conducted for initially segregated Heptane in Nitrogen at supercritical pressure. The governing equations are the compressible Navier-Stokes equations together with a cubic real gas state equation, and generalized heat and mass diffusion derived from non-equilibrium thermodynamics and fluctuation theory. The diffusion fluxes account for both temperature (Dufour) diffusion due to concentration and pressure gradients, and mass (Soret) diffusion due to temperature and pressure gradients. The DNS are conducted using a third order accurate Runge-Kutta temporal integration scheme coupled with eighth order accurate central finite differences at a resolution of 192 x 192 x 192 grid points. Results from two simulations with Taylor microscale based Reynolds number Re=80 and mean fluctuating Mach number Mc=0.5 are compared. One case includes the generalized diffusion formulation, whereas in the second case only standard Fickian and Fourier diffusion are considered. The results are analyzed in order to examine Soret and Dufour effects on the evolutions of the scalar probability density function (PDF), the conditional expected dissipation and the conditional expected diffusion. Evolutions of the scalar PDFs are investigated from initial "double delta" distributions to asymptotically mixed states. Results are similar for each of the flows at early times; however, it is observed that Soret diffusion results in markedly different behaviors of the statistical quantities, which become highly skewed as a function of the scalar fluctuation, at the later stages of mixing. Implications for modeling high pressure combustion are also discussed.

Miller, Richard; Lou, Hong

2000-11-01

154

Rheological contrast between olivine and garnet at high pressures under anhydrous conditions  

Science.gov (United States)

In this study, we carried out experiments investigating the rheological contrast between olivine and garnet, two major components of the mantle, at mantle temperatures and pressures. Experiments were carried out using a deformation-DIA at the National Synchrotron Light Source at Brookhaven National Laboratory. Samples were fabricated from powdered minerals; olivine was from San Carlos and garnet from the Dabie-Sulu orogenic belt in China. In the experiments, a cold-pressed cylinder of fine-grained olivine and one of garnet, each with a diameter of ~1.1 mm and a length of ~0.8 mm, were stacked together, separated by a nickel foil disk. This duplex sample was assembled with alumina pistons, a boron nitride sleeve, and graphite resistance heater into a 6.2-mm edge length cubic mullite-pyrophyllite pressure cell. Experiments were carried out at 1373 - 1573 K and pressures of 3 - 5 GPa. With the synchrotron x-ray beam, a time series of in-situ radiographs enables monitoring of the instantaneous lengths of both deforming samples at the same temperature, pressure, and load. At our experimental conditions, both samples deform with stress exponents of n ? 3 and with activation energies of Q ? 300 kJ/mol. Samples of olivine deform only a factor of ~1.5 faster than samples of garnet of similar grain size, indicating that there is no significant rheological contrast between samples of olivine and garnet under anhydrous conditions. This result, which is the first direct comparison of the rheological behavior of olivine and garnet, provides a solid basis for modeling the rheological structures of subducted lithosphere.

Mei, S.; Suzuki, A. M.; Kohlstedt, D. L.; Durham, W. B.; Dixon, N. A.

2010-12-01

155

High pressure gas pipeline in Artic conditions; Hochdruck-Gaspipeline in arktischen Gebieten  

Energy Technology Data Exchange (ETDEWEB)

More than 2000 km north of moscow, in the timan-pechora region, the kharyaga oil field is located. Gas is transported through a 9.5 km long 6{sup ''} pipeline with an operating pressure of up to 356 bar to a field injection well and is reinjected into the reservoir. The installations are erected in Artic conditions, with ambient temperatures of down to -56 C. The pipeline is laid above ground on piled supports, heat insulated in permafrost conditions. Due to environmental conditions the construction of pipelines is carried out during winter season. A particular difficulty for the design was the fact that Russian as well as western norms and standards for design and material selection had to be fulfilled. In October 2003 the pipeline has been successfully pressure tested with a pressure of 534 bar and put in operation. (orig.) [German] Mehr als 2000 km noerdlich von Moskau, in der Region Timan-Pechora, liegt das Kharjaga Oelfeld. Durch eine 9,5 km lange 6{sup ''} Pipeline mit einem Betriebsdruck von bis zu 356 bar wird Gas zu einer Sondenstation transportiert und wieder in die Lagerstaette eingepresst. Die Anlage wird unter arktischen Bedingungen errichtet und betrieben, mit Temperaturen bis -56 C. In dieser Gegend gibt es durchgaengig Permafrostboden. Deshalb ist die Leitung oberirdisch auf Pfaehlen installiert. Auf Grund der Umweltbedingungen kann der Bau nur im Winter erfolgen. Eine besondere Schwierigkeit fuer die Planung war die Tatsache, dass sowohl westliche als auch russische Normen beruecksichtigt werden mussten. Im Oktober 2003 wurde die Wasserdruckpruefung mit einem Druck von 534 bar erfolgreich durchgefuehrt und die Leitung in Betrieb genommen. (orig.)

Heinz, C. [ILF Beratende Ingenieure GmbH, Muenchen (Germany)

2004-03-01

156

Predicting CO2-water interfacial tension under pressure and temperature conditions of geologic CO2 storage  

Science.gov (United States)

Storage in subsurface geologic formations, principally saline aquifers, is currently under development as a major approach to counter anthropogenic CO2 emissions. To ensure the stability and long-term viability of geologic carbon storage, injected CO2 must be kept in place by an overlying cap rock of very low permeability. Capillary forces in the cap rock act to prevent upward migration and escape of the stored supercritical fluid, with interfacial tension (IFT) between the aqueous brine phase and the CO2 phase being the primary control. However, published experimental CO2-water IFT data vary widely, mainly because of inadequate experimental protocols or inappropriate use of bulk-fluid properties in computing IFT from experimental observations. Only two published data sets were found to meet all criteria of merit for an accurate measurement of IFT over the entire range of pressure (5-45 MPa) and temperature (298-383 K) pertinent to geologic carbon storage. In such circumstances, molecular simulations can enhance the utility of limited data when used to validate assumptions made in their interpretation, resolve discrepancies among data, and fill gaps where data are lacking. Simulations may also be used to provide insight into the relationship between IFT and fundamental properties, such as the strength of the CO2-H2O interaction. Through molecular dynamics simulations, we compared the quality of three CO2 models and two H2O models (SPC/E and TIP4P2005) in predicting IFT under the pressure and temperature conditions relevant to geologic CO2 sequestration. Interfacial tension at fixed temperature simulated via molecular dynamics decreased strongly with increasing pressure below the critical CO2 pressure of 7 MPa, then leveled off, in agreement with experiment, whereas increasing temperature from 300 to 383 K at fixed pressure had little effect on IFT, which is also consistent with experimental data. Our results demonstrated that the strength of the short-range portion of the CO2-H2O interaction exerts a major influence on IFT. The CO2 model that best represented the attractive part of this interaction for randomly-oriented water molecules also best captures the experimental pressure dependence of IFT when combined with either water model. When combined with the SPC/E water model, this CO2 model underestimated IFT by ˜10 mN/m, which approximately equals the amount by which the SPC/E water model underestimates the surface tension of pure water. When combined with the TIP4P2005 water model, this model accurately captured the pressure dependence of the CO2-H2O IFT at 383 K over the entire pressure range examined. These pressure variations will have the dominant effect on IFT—especially at pressures lower than the CO2 critical pressure (˜7 MPa)—and, therefore, on the CO2 storage capacity and sealing integrity of a subsurface reservoir.

Nielsen, Laura C.; Bourg, Ian C.; Sposito, Garrison

2012-03-01

157

Effect of Antecedent Conditions on Prediction of Pore-Water Pressure using Artificial Neural Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of antecedent conditions on the prediction of soil pore-water pressure (PWP) using Artificial Neural Network (ANN) was evaluated using a multilayer feed forward (MLFF) type ANN model. The Scaled Conjugate Gradient (SCG) training algorithm was used for training the ANN. Time series data of rainfall and PWP was used for training and testing the ANN model. In the training stage, time series of rainfall was used as input data and corresponding time series of PWP was used as the target ...

Muhammad Raza Ul Mustafa; Rezaur Rahman Bhuiyan; Mohamed Hasnain Isa; Saied Saiedi; Harianto Rahardjo

2012-01-01

158

Conditioning of waste from the dismantling of reactor pressure vessel components and of core components  

Energy Technology Data Exchange (ETDEWEB)

When power reactors are shut down, the treatment of the core components and of the reactor pressure vessel components constitutes a particular task. Due to its special radiological characteristics, this waste must basically be handled using remote-control equipment with regard to the treatment. For its conditioning in a manner appropriate for the final storage, the waste must be dried and packed into suitable packing drums. The solution implemented by GNS and DSD in order to treat this waste from the Wuergassen nuclear power plant is described in the present contribution. (orig.)

Cleve, R.; Oldiges, O.; Splittler, U.

2001-07-01

159

Experimental study of chloritoid stability at high pressure and various fO2 conditions  

Science.gov (United States)

The reaction chloritoid (ctd)=almandine (alm)+diaspore+H2O (CAD) has been reversed using Fe3+-free synthetic chloritoid and almandine, under fO2 conditions of the solid oxygen buffer Fe/FeO (CADWI), and using partially oxidized synthetic minerals under fO2 conditions of the solid oxygen buffer Ni/NiO (CADNNO). Experiments have been conducted between 550 and 700°C, 25 and 45 kbar. The equilibrium pressure and temperature conditions are strongly dependent on the fO2 conditions (CADNNO lies some-what 50°C higher than CADWI). This can be explained by a decrease in aH2O for experiments conducted on the Fe/FeO buffer, and a decrease in actd and aalm (through incorporation of ferric iron preferentially in chloritoid) for experiments conducted on the Ni/NiO buffer. The H2O activity has been calculated using the MRK equation of state, and the values obtained checked against the shift of the equilibrium diaspore=corundum+H2O bracketed on the Fe/FeO buffer and under unbuffered fO2 conditions. For fO2 buffered by the assemblage Fe/FeO, aH2O increases with pressure from about 0.85 at 600°C, 12 kbar to about 0.9 at 605°C, 25 kbar and 1 above 28 kbar. For fO2 buffered by the assemblage Ni/NiO, aH2O=1. The aH2O decrease from Ni/NiO to Fe/FeO is, however, too small to be entirely responsible for the temperature shift between CADNNO and CADWI. In consequence, the amount of ferric iron in almandine and chloritoid growing in the CADNNO experiments must be significant and change along the CADNNO, precluding calculation of the thermodynamic properties of chloritoid from this reaction. Our experimental data obtained on the Fe/FeO buffer are combined, using a thermodynamic analysis, with Ganguly's (1969) reversal of the reaction chloritoid=almandine+corundum +H2O (CAC) on the same oxygen buffer. Experimental brackets are mutually consistent and allow extraction of the thermodynamic parameters H o f,ctd and S octd. Our thermodynamic data are compared with others, generally calculated using Ganguly's bracketing of CACNNO. The agreement between the different data sets is relatively good at low pressure, but becomes rapidly very poor toward high pressure conditions. Using our thermodynamic data for chloritoid and KD=(Fe3+/Al)ctd/(Fe3+/Al)alm estimated from natural assemblages, we have calculated the composition of chloritoid and almandine growing from CADNNO and CACNNO. The Fe3+ content in chloritoid and almandine increases with pressure, from less than 0.038 per FeAl2SiO5(OH)2 formula unit at 10 kbar to at least 0.2 per formula unit above 30 kbar. This implies that chloritoid and almandine do contain Fe3+ in most natural assemblages. The reliability of our results compared to natural systems and thermodynamic data for Mg-chloritoid is tested by comparing the equilibrium conditions for the reaction chloritoid+quartz=garnet (gt)+kyanite+H2O (CQGK), calculated for intermediate Fe-Mg chloritoid and garnet compositions, from the system FASH and from the system MASH. For 0.65<( XFe)gt<0.8, CQKG calculated from FASH and MASH overlap for KD=(Mg/Fe)ctd/(Mg/Fe)gt=2. This is in good agreement with the KD values reported from chloritoid+garnet+quartz+kyanite natural assemblages.

Vidal, Olivier; Theye, Thomas; Chopin, Christian

1994-12-01

160

Finite Element Simulation of Photoacoustic Pressure in a Resonant Photoacoustic Cell Using Lossy Boundary Conditions  

DEFF Research Database (Denmark)

The finite-element method (FEM) is used to simulate the photoacoustic signal in a cylindrical resonant photoacoustic cell. Simulations include loss effects near the cell walls that appear in the boundary conditions for the inhomogeneous Helmholtz equation governing the acoustic pressure. Reasonably good agreement is obtained between theoretical results and experimental data. However, it was anticipated that loss mechanisms other than viscous and thermal boundary losses occur and should be included. Nevertheless, the feasibility to use FEM together with the derived boundary conditions to simulate the photoacoustic signal was demonstrated and good agreement with experiments for the actual resonance frequency and the quality factor of the cell was obtained despite its complicated geometry.

Duggen, L.; Lopes, N.

2011-01-01

 
 
 
 
161

Electrical conductivity measurement of granulite under mid- to lower crustal pressure-temperature conditions  

Science.gov (United States)

We have developed a technique to measure electrical conductivity of crustal rocks with relatively low conductivity and complicated mineral components in order to compare with results given by magneto-telluric (MT) measurements. A granulite from Hidaka metamorphic belt (HMB) in Hokkaido, Japan at high temperature and pressure conditions was obtained. The granulite sample was ground and sintered under the conditions similar to those of mid- to lower crust. We have observed smooth and reversible change of conductivity with temperature up to about 900 K at 1 GPa. The results were consistent with the electrical conductivity structures suggested by the MT data analysis. Considering pore fluid conduction mechanism or the role of accessory minerals in the rock, the mechanisms of electrical conductivity paths in dry or basic rocks should be reconsidered.

Fuji-ta, K.; Katsura, T.; Tainosho, Y.

2004-04-01

162

Scram characteristics of the control rods of a pressurized water reactor under seismic conditions  

International Nuclear Information System (INIS)

Control rod drop verification experiments of a pressurized water reactor under seismic conditions are performed to confirm the insertion function of control rods into a core. To evaluate these tests, computer simulations are performed. A fuel assembly, control rods, guide tube and other associated structures are immersed in a water tank, and shaken by four hydraulic shakers. The scram time of control rods under seismic conditions was measured, and confirmed to meet the scram function. Moreover, vibrational response characteristics of core structures and dropping behavior of control rods in consideration of collisions are calculated by using a finite difference method. The behavior of the dropping control rods and the scram time obtained by the computer simulation show a very good agreement with the verification experimental results. (author)

1987-01-01

163

Spherically symmetric models with pressure: separating expansion from contraction and generalizing TOV condition  

CERN Document Server

We investigate spherically symmetric perfect fluid spacetimes and discuss the existence and stability of a dividing shell separating expanding and collapsing regions. We perform a 3+1 splitting and obtain gauge invariant conditions relating the intrinsic spatial curvature of the shells to the ADM mass and to a function of the pressure which we introduce and that generalises the Tolman-Oppenheimer-Volkoff equilibrium condition. We analyse the particular cases of the Lema\\^itre-Tolman-Bondi dust models with a cosmological constant as an example of a $\\Lambda$-CDM model and its generalization to contain a central perfect fluid core. These models provide simple, but physically interesting illustrations of our results.

Mimoso, José Pedro; Mena, Filipe C

2009-01-01

164

Meshfree finite differences for vector Poisson and pressure Poisson equations with electric boundary conditions  

CERN Document Server

We demonstrate how meshfree finite difference methods can be applied to solve vector Poisson problems with electric boundary conditions. In these, the tangential velocity and the incompressibility of the vector field are prescribed at the boundary. Even on irregular domains with only convex corners, canonical nodal-based finite elements may converge to the wrong solution due to a version of the Babuska paradox. In turn, straightforward meshfree finite differences converge to the true solution, and even high-order accuracy can be achieved in a simple fashion. The methodology is then extended to a specific pressure Poisson equation reformulation of the Navier-Stokes equations that possesses the same type of boundary conditions. The resulting numerical approach is second order accurate and allows for a simple switching between an explicit and implicit treatment of the viscosity terms.

Zhou, Dong; Shirokoff, David; Chidyagwai, Prince; Rosales, Rodolfo Ruben

2013-01-01

165

The osmotic pressure of highly concentrated monoclonal antibody solutions: effect of solution conditions.  

Science.gov (United States)

The behavior of monoclonal antibodies at high concentrations is important in downstream processing, drug formulation, and drug delivery. The objective of this study was to evaluate the osmotic pressure of a highly purified monoclonal antibody at concentrations up to 250 g/L over a range of pH and ionic strength, and in the presence of specific excipients, using membrane osmometry. Independent measurements of the second virial coefficient were obtained using self-interaction chromatography, and the net protein charge was evaluated using electrophoretic light scattering. The osmotic pressure at pH 5 and low ionic strength was >50 kPa for antibody concentrations above 200 g/L. The second virial coefficients determined from the oncotic pressure (after subtracting the Donnan contribution) were in good qualitative agreement with those determined by self-interaction chromatography. The second virial coefficient decreased with increasing ionic strength and increasing pH due to the reduction in intermolecular electrostatic repulsion. The third virial coefficient was negative under all conditions, suggesting that multi-body interactions in this system are attractive. The virial coefficients were essentially unaffected by addition of sucrose or proline. These results have important implications for the analysis of protein-protein interactions in downstream processing at high protein concentrations. PMID:23996891

Binabaji, Elaheh; Rao, Suma; Zydney, Andrew L

2014-03-01

166

The Influence of Collar on Surge Pressure Caused by the Drill String Inertia Force Under Closed Pipe Condition  

Directory of Open Access Journals (Sweden)

Full Text Available The study of surge pressure is of significant importance for the safety of drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure calculation. In this paper, based on closed pipe condition, a steady-state calculation model for surge pressure caused by drill string inertia force is developed considering the presence of collar. In the end a case study is presented to demonstrate the importance of collar during the calculation of surge pressure.

Jun Li

2013-04-01

167

CFD simulation of pressure and discharge surge in Francis turbine at off-design conditions  

International Nuclear Information System (INIS)

A hybrid 1D-3D CFD model is developed for the numerical simulation of pressure and discharge surge in hydraulic power plants. The most essential part – the turbine itself – is simulated directly using 3D unsteady equations of turbulent motion of fluid-vapor mixture, while the rest of the hydraulic system is simulated in frames of 1D hydro-acoustic model. Thus the model accounts for the main factors responsible for excitation and propagation of pressure and discharge waves in hydraulic power plant. Boundary conditions at penstock inlet and draft tube outlet are discussed in detail. Then simulations of dynamic behavior at part load and full load operating points are performed. It is shown that the numerical model is able to capture self-excited oscillations in full load conditions. The influence of penstock length and flow structure behind the runner are investigated. The presented approach seems to be a promising tool for prediction and investigation the dynamic behavior in hydraulic power plants.

2012-11-26

168

Surveillance of prestressed concrete pressure vessels under commissioning and operational conditions at Hunterston 'B' Power Station  

International Nuclear Information System (INIS)

Monitoring procedures were established to satisfy the Statutory requirements set by the Licensing Authority (The Nuclear Installations Inspectorate), and to demonstrate the continuing safety of the Prestressed Concrete Pressure Vessels (P.C.P.V.) under operational conditions to the Purchaser and Operator (South of Scotland Electricity Board), and the N.I.I. For the long term, 80 vibrating wire strain gauges have been selected as indicating the general behaviour of each vessel under commissioning and operational conditions. A programme of tendon check loading has been set up, allowing an estimate of the prestress obtaining in the vessel to be made. Also, strands are withdrawn for visual and metallurgical examination. Regular temperature scans are carried out using the thermocouples installed in the vessel concrete and on the liner and penetrations. The results of these and other monitoring procedures are discussed. It is concluded that the Prestressed Concrete Pressure Vessels at Hunterston 'B' Power Station are performing in a predictable and satisfactory manner. (orig.)

1979-08-21

169

Thermal response of a modular high temperature reactor during passive cooldown under pressurized and depressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

The concept of inherent safety features of the modular HTR design with respect to passive decay heat removal through conduction, radiation and natural convection was first introduced in the German HTR-module (pebble fuel) design and subsequently extended to other modular HTR design in recent years, e.g. PBMR (pebble fuel), GT-MHR (prismatic fuel) and the new generation reactor V/HTR (prismatic fuel). This paper presents the numerical simulations of the V/HTR using the thermal-hydraulic code THERMIX which was initially developed for the analysis of HTRs with pebble fuels, verified by experiments, subsequently adopted for applications in the HTRs with prismatic fuels and checked against the results of CRP-3 benchmark problem analyzed by various countries with diverse codes. In this paper, the thermal response of the V/HTR (operating inlet/outlet temperatures 490/1000 deg. C) during post shutdown passive cooling under pressurized and depressurized primary system conditions has been investigated. Additional investigations have also been carried out to determine the influence of other inlet/outlet operating temperatures (e.g. 490/850, 350/850 or 350/1000 deg. C) on the maximum fuel and pressure vessel temperature during depressurized cooldown condition. In addition, some sensitivity analyses have also been performed to evaluate the effect of varying the parameters, i.e. decay heat, graphite conductivity, surface emissivity, etc., on the maximum fuel and pressure vessel temperature. The results show that the nominal peak fuel temperatures remain below 1600 deg. C for all these cases, which is the limiting temperature relating to radioactivity release from the fuel. The analyses presented in this paper demonstrate that the code THERMIX can be successfully applied for the thermal calculation of HTRs with prismatic fuel. The results also provide some fundamental information for the design optimization of V/HTR with respect to its maximum thermal power, operating temperatures, etc.

Haque, H. [Framatome ANP GmbH, Freyesleben Strasse 1, 91058 Erlangen (Germany)]. E-mail: hamidul.haque@framatome-anp.com; Feltes, W. [Framatome ANP GmbH, Freyesleben Strasse 1, 91058 Erlangen (Germany); Brinkmann, G. [Framatome ANP GmbH, Freyesleben Strasse 1, 91058 Erlangen (Germany)

2006-03-15

170

Thermal response of a modular high temperature reactor during passive cooldown under pressurized and depressurized conditions  

International Nuclear Information System (INIS)

The concept of inherent safety features of the modular HTR design with respect to passive decay heat removal through conduction, radiation and natural convection was first introduced in the German HTR-module (pebble fuel) design and subsequently extended to other modular HTR design in recent years, e.g. PBMR (pebble fuel), GT-MHR (prismatic fuel) and the new generation reactor V/HTR (prismatic fuel). This paper presents the numerical simulations of the V/HTR using the thermal-hydraulic code THERMIX which was initially developed for the analysis of HTRs with pebble fuels, verified by experiments, subsequently adopted for applications in the HTRs with prismatic fuels and checked against the results of CRP-3 benchmark problem analyzed by various countries with diverse codes. In this paper, the thermal response of the V/HTR (operating inlet/outlet temperatures 490/1000 deg. C) during post shutdown passive cooling under pressurized and depressurized primary system conditions has been investigated. Additional investigations have also been carried out to determine the influence of other inlet/outlet operating temperatures (e.g. 490/850, 350/850 or 350/1000 deg. C) on the maximum fuel and pressure vessel temperature during depressurized cooldown condition. In addition, some sensitivity analyses have also been performed to evaluate the effect of varying the parameters, i.e. decay heat, graphite conductivity, surface emissivity, etc., on the maximum fuel and pressure vessel temperature. The results show that the nominal peak fuel temperatures remain below 1600 deg. C for all these cases, which is the limiting temperature relating to radioactivity release from the fuel. The analyses presented in this paper demonstrate that the code THERMIX can be successfully applied for the thermal calculation of HTRs with prismatic fuel. The results also provide some fundamental information for the design optimization of V/HTR with respect to its maximum thermal power, operating temperatures, etc

2006-03-01

171

Synthesis of boron suboxide from boron and boric acid under mild pressure and temperature conditions  

International Nuclear Information System (INIS)

Graphical abstract: Well-crystallized and icosahedral B6O crystals were prepared by reacting boron and boric acid at milder reaction conditions (1 GPa and 1300 oC for 2 h) as compared to previous work.. Research highlights: ? Well-crystallized icosahedral B6O was synthesized by reacting boric acid and boron. ? The synthesis conditions (1 GPa and 1300 oC for 2 h) are milder in comparison with previous work. ? The more practical synthesis method may make B6O as a potential substitute for diamond in industry. -- Abstract: Boron suboxide (B6O) was synthesized by reacting boron and boric acid (H3BO3) at pressures between 1 and 10 GPa, and at temperatures between 1300 and 1400 oC. The B6O samples prepared were icosahedral with diameters ranging from 20 to 300 nm. Well-crystallized and icosahedral crystals with an average size of ?100 nm can be obtained at milder reaction conditions (1 GPa and 1300 oC for 2 h) as compared to previous work. The bulk B6O sample was stable in air at 600 oC and then slowly oxidized up to 1000 oC. The relatively mild synthetic conditions developed in this study provide a more practical synthesis of B6O, which may potentially be used as a substitute for diamond in industry as a new superhard material.

2011-05-01

172

Stress corrosion cracking of low-alloy reactor pressure vessel steels under boiling water reactor conditions  

Science.gov (United States)

The stress corrosion cracking (SCC) behaviour of different reactor pressure vessel (RPV) steels and weld filler/heat-affected zone materials was characterized under simulated boiling water reactor (BWR) normal water (NWC) and hydrogen water chemistry (HWC) conditions by periodical partial unloading, constant and ripple load tests with pre-cracked fracture mechanics specimens. The experiments were performed in oxygenated or hydrogenated high-purity or sulphate/chloride containing water at temperatures from 150 to 288 °C. In good agreement with field experience, these investigations revealed a very low susceptibility to SCC crack growth and small crack growth rates (BWR/NWC and material conditions. Critical water chemistry, loading and material conditions, which can result in sustained and fast SCC well above the 'BWRVIP-60 SCC disposition lines' were identified, but many of them generally appeared atypical for current optimized BWR power operation practice or modern RPVs. Application of HWC always resulted in a significant reduction of SCC crack growth rates by more than one order of magnitude under these critical system conditions and growth rates dropped well below the 'BWRVIP-60 SCC disposition lines'.

Seifert, H. P.; Ritter, S.

2008-01-01

173

The investigation of argon diffusion in phlogopite under high pressure conditions  

Science.gov (United States)

The present study deals with assessment of pressure effect on the mechanism of bleeding an argon from mica at high temperatures and pressures. The influence of pressure on the diffusion of argon in crustal conditions is not significant (Harrison et al., 2009), while in the mantle conditions, should be significant. The authors suggest that the findings will help to better understand the behavior of K/Ar isotopic system in mica under the lower crust and mantle, including xenoliths transport by kimberlite melt. The experiment was made by using high-pressure spacer "split-sphere" (BARS - 300). Phlogopite from veins cutting metamorphic rocks from the Sludyanka number 2 quarry was used as a testing material. Inclusions of other minerals were not found in the original phlogopite crystal. Chemical composition of phlogopite is homogeneous. 8 experiments was made at a constant pressure of 30 kbar and different temperature and duration: 20 degrees Celsius, 20 minutes; 700 degrees Celsius, 20 minutes; 800 degrees Celsius, 10 minutes; 800 degrees Celsius, 20 minutes; 800 degrees Celsius, 30 minutes; 900 degrees Celsius, 20 minutes; 1000 degrees Celsius, 20 minutes; 1100 degrees Celsius, 20 minutes. According the results of SEM-observation, there is no signs of recrystallization and solid state transformations and melting of phlogopite. It's chemical composition is identical to that of the original phlogopite. Diffractograms of phlogopites after the experiments are similar to the diffractograms of the original phlogopites. Research results of IR spectroscopy, together with the results of SEM and microprobe analysis suggest that phlogopite dehydroxylation in the temperature range T = 700-900 degrees Celsius was negligible. Numerical simulation of the behavior of radiogenic argon in phlogopite at high temperatures and pressure was performed using «Diffarg» software finite differences algorithm, based on the mechanism of bulk thermally activated diffusion (Wheeler, 1996). The size of the effective diffusion domain of mica was considered to be 100-150 microns, when modeling (Baxter, 2010). Comparison of results of simulations and experiments suggests that the mobility of argon isotopes in phlogopite at high temperatures and pressure is well described by the mechanism of thermally activated volume diffusion. Stepwise release of argon in a vacuum experiment was also conducted. The activation energy of 207,714 J/mol was calculated from the slope of the line on the Arrhenius chart. This value is consistent with data obtained by other authors in hydrothermal experiments (Baxter, 2010). The work was supported by the grant of the President of Russia MK-3240.2014.5. Baxter E.F. Diffusion of Noble Gases in Minerals // Reviews in Mineralogy & Geochemistry. 2010. V.72. P.509-557. Harrison T.M., Celerier J., Aikman A.B., Hermann J., Heizler M.T. Diffusion of 40Ar in muscovite // Geochim Cosmochim Acta. 2009. V.73. P.1039-1051. Wheeler J. Diffarg: A program for simulating argon diffusion profiles in minerals // Computers & Geosciences. 1996. V. 22(8). P. 919-929.

Yudin, Denis; Korzhova, Sophia; Travin, Alexey; Zhimulev, Egor; Murzintsev, Nikolay; Moroz, Tatiana

2014-05-01

174

Analysis of pressure locking and thermal binding conditions on shutdown cooling system suction isolation valves  

International Nuclear Information System (INIS)

Shutdown Cooling System (SCS) suction isolation valves for Yonggwang Nuclear Units 5 and 6 (YGN 5 and 6) had been selected as the valves susceptible to pressure locking and thermal binding (PLTB) phenomena considering valves' allowable internal leakage and various operating conditions. To prevent the anticipated PLTB phenomena, the isolation valve type was changed from the flexible-wedge gate valve to the double-disk gate valve with the drilled hole on the upstream disk. During plant pre-operational hydrostatic tests, however, the technical issue regarding the valve type change was raised due to the inherent difficulty in pressurizing the valve downstream piping, which was caused by the drilled hole. In order to resolve this technical issue, the technical adequacy of the valve type change was justified through the identification of the PLTB conditions on the SCS isolation valves using brief hand calculations and FLUENT code simulations. From these calculations and simulations, it was found that the upstream fluid temperatures of the second and third valves were almost the same as the ambient temperature for the case of no leakage in the isolation valves. However, if there were leakage through each isolation valve up to the maximum allowable leakage in the plant Technical Specification, the upstream fluid temperature of the farthest third isolation valve even increased enough to cause the PLTB phenomena. In these analyses, the valve leakage and turbulent penetration due to high-velocity flow in the RCS hot leg were identified as dominant factors which cause the PLTB conditions such as a valve bonnet overpressurization and a thermal difference between both ends of the valve disk. (author)

2003-04-20

175

Direct ion flux measurements at high-pressure-depletion conditions for microcrystalline silicon deposition  

International Nuclear Information System (INIS)

The contribution of ions to the growth of microcrystalline silicon thin films has been investigated in the well-known high-pressure-depletion (HPD) regime by coupling thin-film analysis with plasma studies. The ion flux, measured by means of a capacitive probe, has been studied in two regimes, i.e., the amorphous-to-microcrystalline transition regime and a low-to-high power regime; the latter regime had been investigated to evaluate the impact of the plasma power on the ion flux in collisional plasmas. The ion flux was found not to change considerably under the conditions where the deposited material undergoes a transition from the amorphous to the microcrystalline silicon phase; for solar-grade material, an ion-to-Si deposition flux of ?0.30 has been determined. As an upper-estimation of the ion energy, a mean ion energy of ?19 eV has been measured under low-pressure conditions (4 to an H2 plasma resulted in an increase of the ion flux by about 30% for higher power values, whereas the electron density, deduced from optical emission spectroscopy analysis, decreased. The electron temperature, also deduced from optical emission spectroscopy analysis, reveals a slight decrease with power. Although the dominant ion in the HPD regime is SiH3+, i.e., a change from H3+ in pure hydrogen HPD conditions, the measured larger ion loss can be explained by assuming steeper electron density profiles. These results, therefore, confirm the results reported so far: the ion-to-Si deposition flux is relatively large but has neither influence on the microcrystalline silicon film properties nor on the phase transition. Possible explanations are the reported high atomic hydrogen to deposition flux ratio, mitigating the detrimental effects of an excessive ion flux

2013-08-14

176

Thermal behaviour of pressure tube under fully and partially voided heating conditions using 19 pin fuel element simulator  

International Nuclear Information System (INIS)

In a nuclear reactor temperature can rise drastically during LOCA due to failure of heat transportation system and subsequently leads to mechanical deformations like sagging, ballooning and breaching of pressure tube. To understand the phenomenon an experiment has been carried out using 19 pin fuel element simulator. Main purpose of the experiment was to trace temperature profiles over the pressure tube, calandria tube and clad tubes of 220 MWe Indian Pressurised Heavy Water Reactor (IPHWR). The symmetrical heating of pressure tube of 1 m length was done through resistance heating of 19 pins under 13.5 kW power using a rectifier and the variation of temperatures over the circumference of pressure tube (PT), calandria tube (CT) and clad tubes were measured. The sagging of pressure tube was initiated at 460 deg C temperature and highest temperature attained was 650 deg C. The highest temperature attained by clad tubes was 680 deg C (over outer ring) and heat is dissipated to calandria vessel mainly due to radiation and natural convection. Again to simulate partially voided conditions, asymmetrical heating of pressure was carried out by injecting 8 kW power to upper 8 pins of fuel simulator. A maximum temperature difference of 295 deg C was observed over the circumference of pressure tube which highlights the magnitude of thermal stresses and its role in breaching of pressure tube under partially voided conditions. Integrity of pressure tube was retained during both symmetrical and asymmetrical heatup conditions. (author)

2011-03-01

177

The Influence of Collar on Surge Pressure Caused by the Drilling Fluid Viscous Force under Pumping Condition  

Directory of Open Access Journals (Sweden)

Full Text Available The study of surge pressure is of significant importance for the safety of drilling process because field practice shows that the surge pressure caused by fluid viscous force can cause a great damage to the drilling operation. The accurate calculation of surge pressure is directly related to the safety of the drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure calculation. In this study, based on the pumping condition, a steady-state calculation model for surge pressure caused by drilling fluid viscous force is developed considering the presence of collar. In the end a case study is presented to demonstrate the importance of collar during the calculation of surge pressure.

Jun Li

2013-02-01

178

Intraocular pressure vs intracranial pressure in disease conditions: A prospective cohort study (Beijing iCOP study)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background The correlation between intracranial pressure (ICP) and intraocular pressure (IOP) is still controversial in literature and hence whether IOP can be used as a non-invasive surrogate of ICP remains unknown. The aim of the current study was to further clarify the potential correlation between ICP and IOP. Methods The IOP measured with Goldmann applanation tonometer was carried out on 130 patients whose ICP was determined via lumber puncture. Th...

Li Zhen; Yang Yingxin; Lu Yan; Liu Dachuan; Xu Erhe; Jia Jianping; Yang Diya; Zhang Xiaojun; Yang Huiqing; Ma Daqing; Wang Ningli

2012-01-01

179

Comparison of three mineral candidates in middle and low-pressure condition. Experimental study  

Energy Technology Data Exchange (ETDEWEB)

''Greenhouse Effect'', which is scientifically proven to be main caused by the increasing concentration of CO{sub 2}, has become a topic of national and international concern. Mineral carbonation, such as carbonation of alkaline silicate Ca/Mg minerals, analogous to natural weathering processes, is a potentially attractive route to mitigate possible global warming on the basis of industrial imitation of natural weathering processes. In this paper, three typical natural mineral candidates in China, serpentine, olivine and wollastonite, were selected as carbonation raw materials for direct mineral carbonation experiments under middle and low-pressure. A series number of experiments were carried out to investigate the factors that influence the conversion of carbonation reaction, such as reaction temperature, reaction pressure, particle size, solution composition and pretreatment. The solid products from carbonation experiments were filtered, collected, dried and analyzed by X-ray diffraction (XRD) and field scanning electron microscopy equipped with energy dispersive X-ray analysis (FSEM-EDX) to identify the reaction of mineral carbonation. And the method of mass equilibrium after heat decomposition was used to calculate the mineral carbonation conversion. All the XRD and FSEM analysis validate that carbonation reaction was occurred during the experiments and mineral carbonation is one of the potential techniques for carbon dioxide sequestration. The data of mass equilibrium after heat decomposition was collected and then the conversion formula was used to calculate the carbonation conversion of all the three mineral candidates. The mass equilibrium results show that, for all of the three mineral materials, the carbonation conversion increases with the increasing of reaction temperature. But once the temperature increases above 150 C, the conversion of serpentine decreases a little. Reaction pressure is also an important factor to mineral carbonation process. For all of the three mineral materials, the carbonation conversion increases with the increasing of reaction pressure. Decrease of mineral particle sizes and use of heat treatment before carbonation experiments can effectively improve the carbonation conversion of mineral carbonation. And the addition of NaHCO{sub 3}, which had a buffering effect that kept the solution pH in a certain range, can also improve the carbonation conversion. In this paper, a highest carbonation conversion of 89.5% was obtained under the condition of T = 150 C, P{sub CO{sub 2}} = 4.0 MPa, particle sizes <37 {mu}m in 1 h using wollastonite as the raw material. Compared with serpentine and olivine, wollastonite is the most promising material for carbon dioxide mineral carbonation under middle and low-pressure.

Yan, Heng; Zhang, Jun-ying; Zhao, Yong-chun; Wang, Zhi-lang; Pan, Xia; Xu, Jun; Zheng, Chu-guang [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Lab. of Coal Combustion

2013-07-01

180

QUAVER - A programme to evaluate monopole and dipole boundary conditions in pressure tube reactor lattices  

International Nuclear Information System (INIS)

In order to apply source-sink theory to pressure tube reactor lattices it is necessary to calculate boundary conditions at the fuel channel/moderator interfaces to be satisfied by the neutron flux. A method is described for evaluating the necessary coefficients using multi-group diffusion theory in a cylindricalised lattice cell for both monopole and dipole components of flux. Provision is made for in or out leakage of neutrons in each group at the cell boundary so that allowance can be made for effects of cell environment on the channel boundary conditions. The programme QUAVER (written in EGTRAN) is described for use on the English Electric KDF9 Computer. QUAVER outputs the boundary condition matrices on cards for use in source-sink core calculations, and includes a facility for the condensation of the primary group output to a secondary group structure. The numerical method and the data input specification are described together with full details of a sample calculation. (author)

1967-01-01

 
 
 
 
181

Shock-induced incongruent crystallization from forsterite melt at extreme pressure and temperature conditions  

Science.gov (United States)

We have measured the Hugoniot of forsterite melt under laser-driven shock compression at pressures of 300-1000 GPa and sample temperatures of 6000-9000 K under shock at 300-400 GPa. We employed VISAR and SOP methods that become poluar in the laser-shock community recently, to monitor velocity and temperature simultaneously. The shock velocity-particle velocity relation displays a kink around 350-400 GPa. The slope increase beyond the kink is associated with heating and volume expansion. This has been discussed in the Huginot of antigorite which also displays a similar change. This can be explained as an exothermic reaction by incongruent crystallization of MgO and the residual melt composition becomes MgSiO3. The MgO will be a B2 structure based on the current proposed phase diagram of MgO. Further increasing of shock pressure follows complete melting above ~400 GPa. Laser-driven shock continues to decay with time but the measured temperature profile has indicated an abrupt increase around 250 GPa with decaying pressure. This state is on a linear extension of the phase transition of liquid-liquid on MgSiO3 that was reported recently. Shock-induced incongruent crystallization at extreme conditions has been recognized for the first time in this study, and it plays an important role in the process of planetary formation and giant impacts to change the melt composition abruptly. This research was performed at ILE as collaboration work.

Sekine, T.; Ozaki, N.; Asami, Y.; Miyanishi, K.; Uranishi, H.; Kodama, R.; Sano, T.; Sawaka, Y.

2012-12-01

182

Advanced development and operating experience with a canned motor pump under pressurized water reactor conditions  

International Nuclear Information System (INIS)

At the research reactor FRG-2, Geesthacht, an irradiation device is in operation for testing defective light-water-reactor (LWR) test fuel rods under pressurized water reactor conditions (3200C, 160 bar). The requirements to the canned motor pump for cooling water circulation: medium: Demineralized water, operating temperature 3200C, operating pressure 155 bar, radiation field of the reactor, integration in the irradiation capsule, helium leak rate -6mbar.dm3.s-1, minimum working life 3000 hours, were high and caused difficulties in the acquisition of this component. First test runs with supplied pumps showed that the desired working life could not be achieved. The results of the development steps, the test runs, and the performance in service show that for our range of applications, the best combination of materials for the radial bearings is silicon-infiltrated SiC (8% free Si) against the same material. These bearings allowed a good working life for the pump to be achieved. (orig./GL)

1988-10-04

183

Nonlinear Analysis of Onset of Nucleate Boiling in Natural Circulation under Different Pressure Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we obtain the flow signals before and after the ONB through natural circulation experiments under pressure conditions of 0.15MPa and 0.3MPa. Researches were conducted by applying nonlinear analysis techniques. Results revealed that the power spectrum of volume flow data declined exponentially over time in semi logarithmic coordinates, the autocorrelation coefficient declined gradually and the phase diagram exerted the subtle structures of chaotic movement, which might prove the existence of chaos in natural circulation system. The natural convection of single phase appeared before the occurrence of ONB belonged to a non equilibrium process which showed remarkable random features. The occurrence of ONB was a process containing the beginning of chaotic motion and the continuing occurrence of bubbles at ONB and the tendency of phase change to become nucleation boiling would achieve certain states, which embodied the characteristics of chaos. In addition, the intense density difference environment of natural circulation could accelerate the occurrences of both chaotic motion and ONB. While the density difference of heated liquid decreased with the increase of pressure, which could delay the occurrence of ONB.

Cheng Sheng

2013-04-01

184

Ultrasound propagation in air-filled cylindrical pores under pressurized conditions  

Science.gov (United States)

Ion-track membranes (ITM) are known as polymer films with straight pore channels the size, shape, orientation and density of which can be precisely controlled. Previous ultrasonic studies of ITM using air-coupled and wide-band ultrasound pulses (0.1-5.0 MHz) revealed the possibility to isolate and study ultrasound propagation in these pores. Hence a novel ultrasonic technique has been established to determine pore characteristics of ITM using this pore propagation mode. In this work, we present a modification of the technique based on the use of pressurized air. This is achieved by enclosing transducers and samples in a pressurized chamber (1-9 bar). The main objective of this study is to reduce the attenuation of the ultrasound waves propagating in the pores and to increase the coupling of the ultrasonic energy into this pore propagation mode at the membrane surface in order to extend the applicability range of the existing technique to the characterization of ITM with small pores (diameter < 200 nm), or with very low porosity (<5%), or with pores with partially closed aperture at the membrane surface, or in pores with a more complex geometry, where use of air-coupled ultrasound at room conditions may present some drawbacks.

Gómez Álvarez-Arenas, T. E.; Acosta, V.; Apel, P. Yu.; Orelovitch, O. L.

2012-05-01

185

High Pressure Compression-Molding of ?-Cellulose and Effects of Operating Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Commercial ?-cellulose was compression-molded to produce 1A dog-bone specimens under various operating conditions without any additive. The resulting agromaterials exhibited a smooth, plastic-like surface, and constituted a suitable target as replacement for plastic materials. Tensile and three-points bending tests were conducted according to ISO standards related to the evaluation of plastic materials. The specimens had strengths comparable to classical petroleum-based thermoplastics. They also exhibited high moduli, which is characteristic of brittle materials. A higher temperature and higher pressure rate produced specimens with higher mechanical properties while low moisture content produced weaker specimens. Generally, the strong specimen had higher specific gravity and lower moisture content. However, some parameters did not follow the general trend e.g., thinner specimen showed much higher Young’s Modulus, although their specific gravity and moisture content remained similar to control, revealing a marked skin-effect which was confirmed by SEM observations.

Antoine Rouilly

2013-05-01

186

Natural Circulation Characteristics at Low-Pressure Conditions through PANDA Experiments and ATHLET Simulations  

Directory of Open Access Journals (Sweden)

Full Text Available Natural circulation characteristics at low pressure/low power have been studied by performing experimental investigations and numerical simulations. The PANDA large-scale facility was used to provide valuable, high quality data on natural circulation characteristics as a function of several parameters and for a wide range of operating conditions. The new experimental data allow for testing and improving the capabilities of the thermal-hydraulic computer codes to be used for treating natural circulation loops in a range with increased attention. This paper presents a synthesis of a part of the results obtained within the EU-Project NACUSP “natural circulation and stability performance of boiling water reactors.” It does so by using the experimental results produced in PANDA and by showing some examples of numerical simulations performed with the thermal-hydraulic code ATHLET.

Frank Schäfer

2008-04-01

187

Molecular dynamics study of the dielectric constant of water under high pressure and temperature conditions  

International Nuclear Information System (INIS)

The static dielectric constant of a water model (extended simple point charges, SPC/E) was evaluated by molecular dynamics simulations in the (N, V, E) ensemble for temperatures ranging from T=324 K to 1278 K and densities from 0.257 g/cm3 to 1.1108 g/cm3. The dielectric constants calculated from fluctuations of the total dipole moment of the simulation box in the absence of an external field, and those obtained from the polarization response to an applied field were demonstrated to be consistent. Simulations within the pressure-temperature range (up to 500 MPa and 823 K) of available experimental data yield dielectric constant in very good agreement with experiment. It appears therefore that the SPC/E potential model can be used for the simulation of the dielectric properties of supercritical water and of aqueous solutions under supercritical conditions. (orig.)

1994-07-01

188

Case Study for the Numerical Instabilities of the MATRA at Low Flow and Low Pressure Conditions  

Energy Technology Data Exchange (ETDEWEB)

Subchannel analysis codes are very useful and have important roles in analyzing the thermal performance of nuclear reactors. The COBRA and its descendants, including the MATRA, have been widely used as a subchannel analysis code. These codes are known to be unstable for certain conditions. There have been many efforts to resolve unstableness and increase the stability of the subchannel analysis codes. Cuta et al. assessed the stabilities of subchannel analysis codes, VIPRE-01, COBRA-3C, COBRA-IV-I, and LYNX-T with five different experimental data. They found that those codes are unstable for certain cases in a steady state. And they suggested that the cause of unstableness of those codes is the way the lateral pressure difference is updated in the momentum equation. They introduced the crossflow parameter as a measure of the relative numerical stability.

Seo, Kyong-Won; Hwang, Dae-Hyun; Song, Jae-Seung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2008-05-15

189

Investigation of LPP combustors under elevated pressure conditions; Untersuchungen zu LPP-Flugtriebwerksbrennkammern unter erhoehtem Druck  

Energy Technology Data Exchange (ETDEWEB)

The development of new combustor concepts for aero engines to meet future emissions regulations in based on a detailed knowledge of the combustion process and the velocity field. In the presented thesis, non intrusive measurements were performed in a model combustion chamber under almost realistic pressure and temperature conditions. The species OH, NO, unburned hydrocarbons and fuel droplets were detected in 2 dimensions with the Laser Induced Fluorescence (LIF). The velocity field was measured with the Particle Image Velocimetry technique (PIV). [German] Die Weiterentwicklung neuer Brennkammerkonzepte zur Erfuellung zukuenftiger Schadstoffemissionsrichtlinien erfordert genaue Kenntnisse der ablaufenden Verbrennungs- und Stroemungsvorgaenge in der Brennkammer. Bei den in der Arbeit vorgestellten Untersuchungen wurden in einer LPP-Modellbrennkammer unter annaehernd realistischen Eintrittsbedingungen die Spezies OH, NO, unverbrannte Kohlenwasserstoffe sowie noch fluessiger Brennstoff zweidimensional anhand der Laserinduzierten Fluoreszenz (LIF) nachgewiesen. Das Stroemungsfeld wurde mit Hilfe der Particle Image Velocimetry (PIV) gemessen.

Fink, R.

2001-05-01

190

MCCI study for Pressurized Heavy Water Reactor under hypothetical accident condition  

International Nuclear Information System (INIS)

In case of severe core damage accident in Pressurized Heavy Water Reactor (PHWR), large amount of molten corium is expected to come out into the calandria vault due to failure of calandria vessel. Molten corium at high temperature is sufficient to decompose and ablate concrete. Such attack could fail CV by basement penetration. Since containment is ultimate barrier for activity release. The Molten Core Concrete Interaction (MCCI) of the resulting pool of debris with the concrete has been identified as an important part of the accident sequence. MCCI Analysis has been carried out for PHWR for a hypothetical accident condition where total core material is considered to be relocated in calandria vault. Concrete ablation rate in vertical and radial direction is evaluated for rectangular geometry using MEDICIS module of ASTEC Code. Amount of gases released during MCCI is also evaluated. (author)

2011-03-01

191

An attempt to prepare carbon clathrate compounds using high-pressure and high-temperature conditions  

International Nuclear Information System (INIS)

In an attempt to prepare a crystalline carbon compound having a three-dimensional (3D) network similar to silicon clathrate superconductors, fullerene C60 molecules were three-dimensionally polymerized using high-pressure and high-temperature conditions. A single crystal of 3D polymer was obtained from a two-dimensional C60 polymer with a body-centered orthorhombic symmetry. The X-ray structural analysis of the 3D polymer revealed that the spherical C60 monomer molecules were substantially deformed to cuboidal shapes, each unit being bonded to eight neighboring units to form a body-centered orthorhombic lattice. The new 3D polymer was electrically conductive and showed high micro-Vickers hardness comparable to that of cubic BN

2006-08-15

192

Theoretical and numerical investigations of TAP experiments. New approaches for variable pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

Temporal analysis of products (TAP) is a valuable tool for characterization of porous catalytic structures. Established TAP-modeling requires a spatially constant diffusion coefficient and neglect convective flows, which is only valid in Knudsen diffusion regime. Therefore in experiments, the number of molecules per pulse must be chosen accordingly. New approaches for variable process conditions are highly required. Thus, a new theoretical model is developed for estimating the number of molecules per pulse to meet these requirements under any conditions and at any time. The void volume is calculated as the biggest sphere fitting between three pellets. The total number of pulsed molecules is assumed to fill the first void volume at the inlet immediately. Molecule numbers from these calculations can be understood as maximum possible molecules at any time in the reactor to be in Knudsen diffusion regime, i.e., above the Knudsen number of 2. Moreover, a new methodology for generating a full three-dimensional geometrical representation of beds is presented and used for numerical simulations to investigate spatial effects. Based on a freely available open-source game physics engine library (BULLET), beds of arbitrary-sized pellets can be generated and transformed to CFD-usable geometry. In CFD-software (ANSYS CFX registered) a transient diffusive transport equation with time-dependent inlet boundary conditions is solved. Three different pellet diameters were investigated with 1e18 molecules per pulse, which is higher than the limit from the theoretical calculation. Spatial and temporal distributions of transported species show regions inside the reactor, where non-Knudsen conditions exist. From this results, the distance from inlet can be calculated where the theoretical pressure limit (Knudsen number equals 2) is obtained, i.e., from this point to the end of the reactor Knudsen regime can be assumed. Due to linear dependency of pressure and concentration (assuming ideal gas thermodynamics), the results from one numerical simulation can be converted to any number of molecules per pulse. With this procedure, the distance from inlet from which on Knudsen regime can be assumed for different molecules per pulse can be calculated easily. The new model will be applied to enhance the description of industrially relevant conversions, as for instance alkane conversions on transition metal oxides. (orig.)

Senechal, U.; Breitkopf, C. [Technische Univ. Dresden (Germany). Inst. fuer Energietechnik

2011-07-01

193

Intraocular pressure vs intracranial pressure in disease conditions: A prospective cohort study (Beijing iCOP study  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The correlation between intracranial pressure (ICP and intraocular pressure (IOP is still controversial in literature and hence whether IOP can be used as a non-invasive surrogate of ICP remains unknown. The aim of the current study was to further clarify the potential correlation between ICP and IOP. Methods The IOP measured with Goldmann applanation tonometer was carried out on 130 patients whose ICP was determined via lumber puncture. The Pearson correlation coefficient between ICP and IOP was calculated, the fisher line discriminated analysis to evaluate the effectivity of using IOP to predict the ICP level. Results A significant correlation between ICP and IOP was found. ICP was correlated significantly with IOP of the right eyes (p? Conclusion Our data suggested that although a significant correlation exists between ICP and IOP, caution needs to be taken when using IOP readings by Goldmann applanation tonometer as a surrogate for direct cerebrospinal fluid pressure measurement of ICP.

Li Zhen

2012-08-01

194

Effect of Nb additions on the microstructure, thermal stability and mechanical behavior of high pressure Zr phases under ambient conditions  

Energy Technology Data Exchange (ETDEWEB)

Research highlights: {yields} We analyze the influence of Nb additions on the shear-induced {alpha} {yields} {omega} {yields} {beta} phase transformations in pure Zr by high pressure torsion (HPT). {yields} Nb reduces the transition pressures and increases the transformation kinetics. {yields} High pressure phases are retained under ambient conditions due to the presence of an internal stress. {yields} Post-HPT annealing allows to fabricate bimodal/biphase nanostructures with enhanced mechanical behavior. - Abstract: This paper analyzes the influence of Nb on the shear-induced {alpha} {yields} {omega} {yields} {beta} transformation taking place when processing Zr by high pressure torsion (HPT) under suitable conditions of pressure and shear. With that purpose, pure Zr and Zr-2.5%Nb were processed by HPT at room temperature and at pressures ranging from 0.25 to 6 GPa using 5 anvil turns. Nb causes a further reduction of the transition pressures, which are already lower when applying shear besides pressure. Thus, the transition pressure to the {beta} phase is reduced at least 100 times in the Zr-Nb alloy. Alloying with Nb decreases the grain size of the transformed phases, significantly enhances their thermal stability and increases their UTS and elongation to failure. Selected post-HPT annealing treatments lead to the development of very tough, multiphase Zr and Zr-Nb with bimodal grain size distributions. The retention of the high pressure phases under ambient conditions is explained by the development of a high internal stress during processing. This stress is measured by synchrotron radiation diffraction at HZB-BESSY II. It is proposed that the presence of Nb reduces the internal stress level required for the retention of the high pressure phases.

Zhilyaev, A.P. [Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, 28040 Madrid (Spain); Institute for Metals Superplasticity Problems, RAS, 450001 Ufa (Russian Federation); Sabirov, I. [Madrid Institute for Advanced Studies of Materials (IMDEA-Materials Institute) C/Profesor Aranguren s/n, 28040 Madrid (Spain); Gonzalez-Doncel, G. [Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, 28040 Madrid (Spain); Molina-Aldareguia, J.; Srinivasarao, B. [Madrid Institute for Advanced Studies of Materials (IMDEA-Materials Institute) C/Profesor Aranguren s/n, 28040 Madrid (Spain); Perez-Prado, M.T., E-mail: teresa.perez.prado@imdea.org [Madrid Institute for Advanced Studies of Materials (IMDEA-Materials Institute) C/Profesor Aranguren s/n, 28040 Madrid (Spain)

2011-04-15

195

Effect of Nb additions on the microstructure, thermal stability and mechanical behavior of high pressure Zr phases under ambient conditions  

International Nuclear Information System (INIS)

Research highlights: ? We analyze the influence of Nb additions on the shear-induced ? ? ? ? ? phase transformations in pure Zr by high pressure torsion (HPT). ? Nb reduces the transition pressures and increases the transformation kinetics. ? High pressure phases are retained under ambient conditions due to the presence of an internal stress. ? Post-HPT annealing allows to fabricate bimodal/biphase nanostructures with enhanced mechanical behavior. - Abstract: This paper analyzes the influence of Nb on the shear-induced ? ? ? ? ? transformation taking place when processing Zr by high pressure torsion (HPT) under suitable conditions of pressure and shear. With that purpose, pure Zr and Zr-2.5%Nb were processed by HPT at room temperature and at pressures ranging from 0.25 to 6 GPa using 5 anvil turns. Nb causes a further reduction of the transition pressures, which are already lower when applying shear besides pressure. Thus, the transition pressure to the ? phase is reduced at least 100 times in the Zr-Nb alloy. Alloying with Nb decreases the grain size of the transformed phases, significantly enhances their thermal stability and increases their UTS and elongation to failure. Selected post-HPT annealing treatments lead to the development of very tough, multiphase Zr and Zr-Nb with bimodal grain size distributions. The retention of the high pressure phases under ambient conditions is explained by the development of a high internal stress during processing. This stress is measured by synchrotron radiation diffraction at HZB-BESSY II. It is proposed that the presence of Nb reduces the internal stress level required for the retention of the high pressure phases.

2011-04-15

196

Electrical Conductivity Measurement of Granulite Under Mid to Lower Crustal Pressure-Temperature Conditions  

Science.gov (United States)

We have developed a technique to measure electrical conductivity of crustal rocks with relatively low conductivity and complicated mineral components in order to compare with results given by Magneto-Telluric (MT) measurements. A granulite from Hidaka Metamorphic Belt (HMB) in Hokkaido, Japan at high temperature and pressure conditions was obtained. The granulite sample was ground and sintered under the conditions similar to those of mid to lower crust. We have observed smooth and reversible change of conductivity with temperature up to about 900 K at 1 GPa. Through the qualitative and quantitative evaluations using Electron Probe Micro Analysis (EPMA), microstructures of the sintered sample were inspected. This inspection is essential to confirm the sample was not affected by chemical interaction of minerals. We also examined the role of accessory minerals in the rock, and the mechanisms of electrical conductivity paths in _gdry_h or _gbasic_h rocks should be reconsidered. Finally, results from electrical conductivity measurements were consistent with the electrical conductivity structures suggested by the former MT data analysis.

Fuji-Ta, K.; Katsura, T.; Tainosho, Y.

2003-12-01

197

Appropriate welding conditions of temper bead weld repair for SQV2A pressure vessel steel  

Energy Technology Data Exchange (ETDEWEB)

Temper bead welding technique is one of the most important repair welding methods for large structures for which it is difficult to perform the specified post weld heat treatment. In this study, appropriate temper bead welding conditions to improve the characteristics of heat affected zone (HAZ) are studied using pressure vessel steel SQV2A corresponding to ASTM A533 Type B Class 1. Thermal/mechanical simulator is employed to give specimens welding thermal cycles from single to quadruple cycle. Charpy absorbed energy and hardness of simulated CGHAZ by first cycle were degraded as compared with base metal. Improvability of these degradations by subsequent cycles is discussed and appropriate temper bead thermal cycles are clarified. When the peak temperature lower than Ac1 and near Ac1 in the second thermal cycle is applied to CGAHZ by first thermal cycle, the characteristics of CGHAZ improve enough. When the other peak temperatures (that is, higher than Ac1) in the second thermal cycle are applied to the CGHAZ, third or more thermal cycle temper bead process should be applied to improve the properties. Appropriate weld condition ranges are selected based on the above results. The validity of the selected ranges is verified by the temper bead welding test. (orig.)

Mizuno, R.; Matsuda, F. [NDE Center, Japan Power Engineering and Inspection Corp. (Japan); Brziak, P. [Welding Research Inst. - Industrial Inst. of Slovak Republic (Slovakia); Lomozik, M. [Inst. of Welding (Poland)

2004-07-01

198

Direct ion flux measurements at high-pressure-depletion conditions for microcrystalline silicon deposition  

Energy Technology Data Exchange (ETDEWEB)

The contribution of ions to the growth of microcrystalline silicon thin films has been investigated in the well-known high-pressure-depletion (HPD) regime by coupling thin-film analysis with plasma studies. The ion flux, measured by means of a capacitive probe, has been studied in two regimes, i.e., the amorphous-to-microcrystalline transition regime and a low-to-high power regime; the latter regime had been investigated to evaluate the impact of the plasma power on the ion flux in collisional plasmas. The ion flux was found not to change considerably under the conditions where the deposited material undergoes a transition from the amorphous to the microcrystalline silicon phase; for solar-grade material, an ion-to-Si deposition flux of ?0.30 has been determined. As an upper-estimation of the ion energy, a mean ion energy of ?19 eV has been measured under low-pressure conditions (<1 mbar) by means of a retarding field energy analyzer. Combining this upper-estimate with an ion per deposited Si atom ratio of ?0.30, it is concluded that less than 6 eV is available per deposited Si atom. The addition of a small amount of SiH{sub 4} to an H{sub 2} plasma resulted in an increase of the ion flux by about 30% for higher power values, whereas the electron density, deduced from optical emission spectroscopy analysis, decreased. The electron temperature, also deduced from optical emission spectroscopy analysis, reveals a slight decrease with power. Although the dominant ion in the HPD regime is SiH{sub 3}{sup +}, i.e., a change from H{sub 3}{sup +} in pure hydrogen HPD conditions, the measured larger ion loss can be explained by assuming steeper electron density profiles. These results, therefore, confirm the results reported so far: the ion-to-Si deposition flux is relatively large but has neither influence on the microcrystalline silicon film properties nor on the phase transition. Possible explanations are the reported high atomic hydrogen to deposition flux ratio, mitigating the detrimental effects of an excessive ion flux.

Bronneberg, A. C.; Kang, X.; Palmans, J.; Janssen, P. H. J.; Lorne, T. [Applied Physics Department, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Creatore, M. [Applied Physics Department, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Solliance Solar Research, High Tech Campus 5, 5656AE Eindhoven (Netherlands); Sanden, M. C. M. van de [Applied Physics Department, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Dutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 1207, 3430BE Nieuwegein (Netherlands)

2013-08-14

199

The kinetics of dolomite reaction rim growth under isostatic and non-isostatic pressure conditions  

Science.gov (United States)

During burial and exhumation, rocks are simultaneously exposed to metamorphic reactions and tectonic stresses. Therefore, the reaction rate of newly formed minerals may depend on chemical and mechanical driving forces. Here, we investigate the reaction kinetics of dolomite (CaMg[CO3]2) rim growth by solid-state reactions experiments on oriented calcite (CaCO3) and magnesite (MgCO3) single crystals under isostatic and non-isostatic pressure conditions. Cylindrical samples of 3-5 mm length and 7 mm diameter were drilled and polished perpendicular to the rhombohedral cleavage planes of natural clear crystals. The tests were performed using a Paterson-type deformation apparatus at P = 400 MPa confining pressure, temperatures, T, between 750 and 850°C, and reaction durations, t, of 2 - 146 h to calculate the kinetic parameters of dolomite rim growth under isostatic stress conditions. For non-isostatic reaction experiments we applied in addition differential stresses, ?, up to 40 MPa perpendicular to the contact interface at T = 750°C for 4 - 171 h duration, initiating minor inelastic deformation of calcite. The thickness of the resulting dolomite reaction rims increases linearly with the square root of time, indicating a diffusion-controlled reaction. The rims consist of two different textural domains. Granular dolomite grains (? 2 -5 ?m grain size) form next to calcite and elongated palisade-shaped grains (1-6 ?m diameter) grow perpendicular to the magnesite interface. Texture measurements with the electron backscatter diffraction technique indicate that the orientations of dolomite grains are mainly influenced by the orientation of the calcite educt crystal, in particular in the granular rim. To some extent, the texture of dolomite palisades is also influenced by the orientation of magnesite. The thickness of the two individual layers increases with temperature. At 400 MPa isostatic pressure, T = 750°C and t = 29 hours, a 5 ?m thick granular dolomite layer and a 7 ?m thick palisade-shaped layer evolve. At similar conditions and a differential stress of 30 MPa, the rim thickness remains similar; consequently the effect of non-isostatic stress on dolomite rim growth is negligible. Platinum markers show that the initial calcite-magnesite interface is located between granular and palisade-forming dolomite, indicating that rim growth occurs by counter diffusion of MgO and CaO. Diffusion of MgO across the dolomite reaction rim into calcite forms additionally magnesio-calcite grains with diameters of ? 13 - 46 ?m, depending on the experimental conditions and increasing with increasing distance to the dolomite boundary. At T = 750°C, t = 29 hours, the thickness of the magnesio-calcite layer is 32 ?m (isostatic) - 35 ?m (? = 30 MPa). The experiments indicate that solid-state reaction rim growth of dolomite between calcite and magnesite is primarily controlled by diffusion of MgO and CaO, forming layers with different microstructures during growth into the educt phases. The kinetics of the reaction in the carbonate system are not significantly changed by differential stresses up to 40 MPa. We suggest that volume diffusion is the dominant transport mechanism, which is presumably less affected by non-isostatic stresses than grain boundary diffusion.

Helpa, V.; Rybacki, E.; Morales, L. G.; Abart, R.; Dresen, G. H.

2013-12-01

200

Magnetite reactivity in representative conditions of the secondary circuit of pressurized water reactors  

International Nuclear Information System (INIS)

In the secondary circuit of Pressurized Water Reactors (PWR), magnetite deposits lead to steam generators (SG) fouling, which decreases thermal performances and enhances stress corrosion cracking (SCC). The aim of this study is to improve the understanding of magnetite particles behaviour and their reactivity in the secondary circuit conditions. Experimental tests investigated the fast thermal decomposition of hydrazine, injected in the secondary circuit to eliminate oxygen. Temperature, pH, and catalytic properties of materials surfaces have an influence on the kinetics of hydrazine decomposition. A predictive model was proposed. Growing, transport and deposits of iron oxides, essentially formed with magnetite, responsible of the steam generator fouling, were studied in the experimental loop FORTRAND, Formation and Transport of Deposits. Surface characterizations show that magnetite is the corrosion product formed on carbon steel and stainless steel at 220 C, and goethite is formed at room temperature on stainless steel. Results indicate also that the effect of different amines, used in the secondary circuit, on the soluble iron is principally due to their effect on the pH. Performed tests highlight transport and deposition of magnetite particles in the loop. Deposits formed in the SG could promote SCC of tubes by sorption and reduction of sulfates. To reproduce secondary circuit conditions, studies of sorption were made in reducing medium imposed by hydrazine. At 275 C, the presence of hydrazine has an effect on the speciation of sulfates in solution but does not seem to influence the sorption nor to lead to H2S(g) emission predicted by thermodynamic calculations. These experimental results are used to predict sulfur and iron species behaviour in the secondary circuit. Low pH conditioning enhances soluble iron concentration, consequently iron transport in the SG. Sulfides are the most probable sulfur species in flow-restricted areas of SG, harmful for stress corrosion cracking. (author)

2010-01-01

 
 
 
 
201

Artificial maintenance of the relative ocular tissue pressure during eye surgery.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We describe an operating table in which the whole patient, apart from the eye undergoing surgery, is enclosed in a caisson within which the barometric pressure can be lowered at any time during surgery. This increases the effect of atmospheric pressure on the eye, enabling 'open sky' surgery to be carried out on patients of any age.

Maggi, C.; Maggi, R.

1990-01-01

202

Modeling swelling process of compacted bentonite. Part 1. Numerical simulation on effects of test conditions on swelling pressure  

International Nuclear Information System (INIS)

In the current concept of repository for radioactive waste disposal, compacted bentonite as well as bentonite-based material will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. In most cases, welling pressure is one of the most important characteristics of bentonite as an engineered barrier. However results of laboratory tests of swelling pressure often vary considerably even if index parameter, such as effective clay density, is constant. Thus, the joint study with JAEA for specifying causes of the variability was conducted, revealing that different among welling pressure test apparatuses was the most influencing factor. In this study, welling model of unsaturated bentonite is proposed for simulating the effects of three test conditions, which are deformability of swelling pressure test apparatuses, height of specimens and initial water content, on measured swelling pressure. Consequently, it is revealed that the effects of three test conditions on swelling pressures can be simulated by the model and that scattering of measured swelling pressure is mostly attributable to deformability of swelling pressure test apparatuses and height of specimens. (author)

2011-04-01

203

Numerical simulation on effects of test conditions on measured swelling pressure of compacted bentonite by swelling model  

International Nuclear Information System (INIS)

In the current concept of repository for radioactive waste disposal, compacted bentonite as well as bentonite-based material will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. In most cases, swelling pressure is one of the most important characteristics of bentonite as an engineered barrier. However measured swelling pressure by laboratory tests often varies considerably even if index parameter, such as effective clay density, is constant. Thus, existing study already revealed that difference among swelling pressure test apparatuses was the most influencing factor. In this study, swelling model of unsaturated bentonite is proposed for simulating the effects of three test conditions, which are deformability of swelling pressure test apparatuses, height of specimens and initial water content, on measured swelling pressure. Consequently, it is revealed that the effects of three test conditions on swelling pressures can be simulated by the model and that scattering of measured swelling pressure is mostly attributable to deformability of swelling pressure test apparatuses and height of specimens. (author)

2011-01-01

204

An Inexpensive Arterial Pressure Wave Sensor and its application in different physiological condition  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Arterial Blood Pressure wave monitoring is considered to be important in assessment of cardiovascular system. We developed a novel pulse wave detection system using low frequency specific piezoelectric material as pressure wave sensor. The transducer detects the periodic change in the arterial wall diameter produced by pressure wave and the amplified signal after integration represents the pressure wave. The signal before integration is proportional to the rate of change of ...

Sur, Shantanu; Ghatak, S. K.

2005-01-01

205

On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions  

Science.gov (United States)

The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05 , which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the physics of the separation phenomenon under periodic unsteady wake flow. Several physical mechanisms are discussed.

Schobeiri, Meinhard T.; Ozturk, Burak; Ashpis, David E.

2005-01-01

206

Pharmaceutical hydrates under ambient conditions from high-pressure seeds: a case study of GABA monohydrate.  

Science.gov (United States)

The monohydrate form of the neurotransmitter ?-amino butyric acid (GABA) has been crystallised in the 0.4-0.8 GPa pressure range, recovered to ambient pressure and then used as a seed. Theoretical calculations indicate that this hydrate is only thermodynamically favoured over the two anhydrous forms at high pressures. PMID:24400322

Fabbiani, Francesca P A; Buth, Gernot; Levendis, Demetrius C; Cruz-Cabeza, Aurora J

2014-02-21

207

Spatiotemporal variation of radon and carbon dioxide concentrations in an underground quarry: coupled processes of natural ventilation, barometric pumping and internal mixing  

Energy Technology Data Exchange (ETDEWEB)

Radon-222 and carbon dioxide concentrations have been measured during several years at several points in the atmosphere of an underground limestone quarry located at a depth of 18 m in Vincennes, near Paris, France. Both concentrations showed a seasonal cycle. Radon concentration varied from 1200 to 2000 Bq m{sup -3} in summer to about 800-1400 Bq m{sup -3} in winter, indicating winter ventilation rates varying from 0.6 to 2.5 x 10{sup -6} s{sup -1}. Carbon dioxide concentration varied from 0.9 to 1.0% in summer, to about 0.1-0.3% in winter. Radon concentration can be corrected for natural ventilation using temperature measurements. The obtained model also accounts for the measured seasonal variation of carbon dioxide. After correction, radon concentrations still exhibit significant temporal variation, mostly associated with the variation of atmospheric pressure, with coupling coefficients varying from -7 to -26 Bq m{sup -3} hPa{sup -1}. This variation can be accounted for using a barometric pumping model, coupled with natural ventilation in winter, and including internal mixing as well. After correction, radon concentrations exhibit residual temporal variation, poorly correlated between different points, with standard deviations varying from 3 to 6%. This study shows that temporal variation of radon concentrations in underground cavities can be understood to a satisfactory level of detail using non-linear and time-dependent modelling. It is important to understand the temporal variation of radon concentrations and the limitations in their modelling to monitor the properties of natural or artificial underground settings, and to be able to assess the existence of new processes, for example associated with the preparatory phases of volcanic eruptions or earthquakes.

Perrier, Frederic, E-mail: perrier@ipgp.jussieu.f [Equipe de Geomagnetisme, Institut de Physique du Globe de Paris UMR7154 et universite Paris Diderot, 4, Place Jussieu, F-75005 Paris (France); Richon, Patrick [CEA, DAM, DIF, F-91297 Arpajon (France); Equipe Geologie des Systemes Volcaniques, Institut de Physique du Globe de Paris UMR7154, 4, Place Jussieu, F-75005 Paris (France)

2010-04-15

208

Spatiotemporal variation of radon and carbon dioxide concentrations in an underground quarry: coupled processes of natural ventilation, barometric pumping and internal mixing  

International Nuclear Information System (INIS)

Radon-222 and carbon dioxide concentrations have been measured during several years at several points in the atmosphere of an underground limestone quarry located at a depth of 18 m in Vincennes, near Paris, France. Both concentrations showed a seasonal cycle. Radon concentration varied from 1200 to 2000 Bq m-3 in summer to about 800-1400 Bq m-3 in winter, indicating winter ventilation rates varying from 0.6 to 2.5 x 10-6 s-1. Carbon dioxide concentration varied from 0.9 to 1.0% in summer, to about 0.1-0.3% in winter. Radon concentration can be corrected for natural ventilation using temperature measurements. The obtained model also accounts for the measured seasonal variation of carbon dioxide. After correction, radon concentrations still exhibit significant temporal variation, mostly associated with the variation of atmospheric pressure, with coupling coefficients varying from -7 to -26 Bq m-3 hPa-1. This variation can be accounted for using a barometric pumping model, coupled with natural ventilation in winter, and including internal mixing as well. After correction, radon concentrations exhibit residual temporal variation, poorly correlated between different points, with standard deviations varying from 3 to 6%. This study shows that temporal variation of radon concentrations in underground cavities can be understood to a satisfactory level of detail using non-linear and time-dependent modelling. It is important to understand the temporal variation of radon concentrations and the limitations in their modelling to monitor the properties of natural or artificial underground settings, and to be able to assess the existence of new processes, for example associated with the preparatory phases of volcanic eruptions or earthquakes.

2010-04-01

209

Stress corrosion cracking of low alloy steels under high pressure and high temperature conditions  

International Nuclear Information System (INIS)

The stress corrosion behavior of fine grained, low alloy steels has been investigated using constant strain rate tensile tests. Studied materials were a A508 Class 2 type KS05 and a A533 B Class 1. The susceptibility to stress corrosion cracking was determined as a function of the amount of dissolved oxygen and temperature using cylindrical smooth specimen (DIN 50125) in purified water (conductivity below 0.2 microS/cm). The environment was controlled and conditioned using a closed loop refreshing apparatus. The strain rate was varied between 2 · 10-2 and 5 · 10-9 1/s. Most of the experiments have been carried out until fracture of the specimens. In addition some experiments were stopped after various exposure times and the specimens were broken in liquid nitrogen in order to observe initial stages of crack formation and crack propagation. The fracture surface of broken specimens has been examined by means of light and scanning electron microscopy. The fraction of brittle fracture mode on the rupture surface has been quantified in relation to exposure time to estimate a crack growth velocity. The results of the experiments indicate a lowest oxygen concentration in the water necessary for the appearance of stress corrosion cracking which is estimated to be 10 ppb. Brittle cracking generated by stress corrosion during exposure to high pressure high temperature conditions only appears beyond a preliminary plastic deformation. The value of this critical plastic deformation was found to be 3% but a lower critical value cannot be excluded. Additional stress corrosion is significant only at strain rates below 10-4 1/s. Values of true crack propagation rates can be determined only after correcting for the slow straining time necessary to reach the critical elongation. At this stage crack initiation always starts at sulfide inclusions in or beneath the specimen surface

1996-03-24

210

Measurement of subcooled boiling pressure drop and local heat transfer coefficient in horizontal tube under LPLF conditions  

International Nuclear Information System (INIS)

Highlights: ? Measured subcooled boiling pressure drop and local heat transfer coefficient in horizontal tubes. ? Infra-red thermal imaging is used for wall temperature measurement. ? Developed correlations for pressure drop and local heat transfer coefficient. -- Abstract: Horizontal flow is commonly encountered in boiler tubes, refrigerating equipments and nuclear reactor fuel channels of pressurized heavy water reactors (PHWR). Study of horizontal flow under low pressure and low flow (LPLF) conditions is important in understanding the nuclear core behavior during situations like LOCA (loss of coolant accidents). In the present work, local heat transfer coefficient and pressure drop are measured in a horizontal tube under LPLF conditions of subcooled boiling. Geometrical parameters covered in this study are diameter (5.5 mm, 7.5 mm and 9.5 mm) and length (550 mm, 750 mm and 1000 mm). The operating parameters varied are mass flux (450–935 kg/m2 s) and inlet subcooling (29 °C, 50 °C and 70 °C). Infra-red thermography is used for the measurement of local wall temperature to estimate the heat transfer coefficient in single phase and two phase flows with water as the working medium at atmospheric pressure. Correlation for single phase diabatic pressure drop ratio (diabatic to adiabatic) as a function of viscosity ratio (wall temperature to fluid temperature) is presented. Correlation for pressure drop under subcooled boiling conditions as a function of Boiling number (Bo) and Jakob number (Ja) is obtained. Correlation for single phase heat transfer coefficient in the thermal developing region is presented as a function of Reynolds number (Re), Prandtl number (Pr) and z/d (ratio of axial length of the test section to diameter). Correlation for two phase heat transfer coefficient under subcooled boiling condition is developed as a function of boiling number (Bo), Jakob number (Ja) and Prandtl number (Pr)

2013-02-01

211

Test equipment for the determination of the corrosion fatigue of reactor materials under pressurized water reactor conditions  

International Nuclear Information System (INIS)

An experimental set-up was developed for the determination of corrosion fatigue properties under pressure water conditions. The design of the autoclave and its arrangement in a servo-hydraulic pulsator are described. Tests can be performed with this apparatus in pressure water up to 350"0C and 165 bar with top loads of 20 000 N at frequencies up to 30 cycles per second. (orig.)

1979-01-01

212

Measurement of subcooled boiling pressure drop and local heat transfer coefficient in horizontal tube under LPLF conditions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? Measured subcooled boiling pressure drop and local heat transfer coefficient in horizontal tubes. ? Infra-red thermal imaging is used for wall temperature measurement. ? Developed correlations for pressure drop and local heat transfer coefficient. -- Abstract: Horizontal flow is commonly encountered in boiler tubes, refrigerating equipments and nuclear reactor fuel channels of pressurized heavy water reactors (PHWR). Study of horizontal flow under low pressure and low flow (LPLF) conditions is important in understanding the nuclear core behavior during situations like LOCA (loss of coolant accidents). In the present work, local heat transfer coefficient and pressure drop are measured in a horizontal tube under LPLF conditions of subcooled boiling. Geometrical parameters covered in this study are diameter (5.5 mm, 7.5 mm and 9.5 mm) and length (550 mm, 750 mm and 1000 mm). The operating parameters varied are mass flux (450–935 kg/m{sup 2} s) and inlet subcooling (29 °C, 50 °C and 70 °C). Infra-red thermography is used for the measurement of local wall temperature to estimate the heat transfer coefficient in single phase and two phase flows with water as the working medium at atmospheric pressure. Correlation for single phase diabatic pressure drop ratio (diabatic to adiabatic) as a function of viscosity ratio (wall temperature to fluid temperature) is presented. Correlation for pressure drop under subcooled boiling conditions as a function of Boiling number (Bo) and Jakob number (Ja) is obtained. Correlation for single phase heat transfer coefficient in the thermal developing region is presented as a function of Reynolds number (Re), Prandtl number (Pr) and z/d (ratio of axial length of the test section to diameter). Correlation for two phase heat transfer coefficient under subcooled boiling condition is developed as a function of boiling number (Bo), Jakob number (Ja) and Prandtl number (Pr)

Baburajan, P.K. [Atomic Energy Regulatory Board, Mumbai (India); Bisht, G.S. [Indian Institute of Technology, Bombay (India); Gupta, S.K. [Atomic Energy Regulatory Board, Mumbai (India); Prabhu, S.V., E-mail: svprabhu@iitb.ac.in [Indian Institute of Technology, Bombay (India)

2013-02-15

213

HEADCO: a program for converting observed water levels and pressure measurements to formation pressure and standard hydraulic head  

International Nuclear Information System (INIS)

Static water-level and fluid pressure measurements are commonly converted in hydrologic studies to formation pressure and hydraulic head, which are used to determine groundwater flow characteristics of aquifer systems. While the direct use of field measurements is usually adequate for determining formation pressure and hydraulic head for shallow flow systems (i.e., <1000 ft), corrections and conversion parameters must be used to properly account for fluid-column density effects, which commonly occur with deep systems. This report presents a program, HEADCO, for converting static water-level and pressure measurements to formation pressure and standard hydraulic head. The HEADCO program corrects field measurements for the effects of fluid-density variation and selected external stresses. Factors that affect density of the fluid column, in which field measurements are made, include temperature, pressure, salinity, suspended solids, and multiphase conditions. External stresses examined in HEADCO include barometric and earth tide fluctuations, and gravitational acceleration variation. A program description and procedures for converting field measurements obtained using field test arrangements commonly employed in the Basalt Waste Isolation Project field program are provided in this report. The report includes user instructions and an illustrative test example. Results of a field example comparison are also provided. This comparison examines observed and HEADCO-calculated pressures for 30 pressure probes recently calibrated in a laboratory and tested under field conditions at borehole DC-8. The test case and field example comparisons indicate that HEADCO provides accurate estimates of formation pressure and standard hydraulic head that are well within the accuracy range of downhole pressure-measuring instrumentation. 44 refs., 14 figs., 8 tabs

1985-01-01

214

Characterization of transient discharges under atmospheric-pressure conditions applying nitrogen photoemission and current measurements  

International Nuclear Information System (INIS)

The plasma parameters such as electron distribution function and electron density of three atmospheric-pressure transient discharges namely filamentary and homogeneous dielectric barrier discharges in air, and the spark discharge of an argon plasma coagulation (APC) system are determined. A combination of numerical simulation as well as diagnostic methods including current measurement and optical emission spectroscopy (OES) based on nitrogen emissions is used. The applied methods supplement each other and resolve problems, which arise when these methods are used individually. Nitrogen is used as a sensor gas and is admixed in low amount to argon for characterizing the APC discharge. Both direct and stepwise electron-impact excitation of nitrogen emissions are included in the plasma-chemical model applied for characterization of these transient discharges using OES where ambiguity arises in the determination of plasma parameters under specific discharge conditions. It is shown that the measured current solves this problem by providing additional information useful for the determination of discharge-specific plasma parameters. (paper)

2012-03-28

215

Bundle critical power predictions under normal and abnormal conditions in pressurized water reactors  

Energy Technology Data Exchange (ETDEWEB)

In this paper a new approach to bundle critical power predictions is presented. In addition to a very accurate critical heat flux (CHF) model, correction factors that account for the effects of grid spacers, heat flux non-uniformities, and cold walls, which are needed for critical power predictions for practical fuel bundles, are developed. By using the subchannel analysis code COBRA IIIC/MIT-1, local flow conditions needed as input to CHF correlations are obtained. Critical power is therefore obtained iteratively to ensure that the bundle power value from the subchannel analysis will cause CHF at only one point in the bundle. Good agreement with the experimental data is obtained. The accuracy is higher than that of the W-3 and EPRI-1 correlations for the limited data base used in this study. The effects of three types of fuel abnormalities, namely, local heat flux spikes, local flow blockages, and rod bowing, on bundle critical power are also analyzed. The local heat flux spikes and flow blockages have no significant influence on critical power. However, rod bowing phenomena have some effect, the severity of which depends on system pressure, the gap closure between adjacent rods, and the presence or absence of thimble tubes (cold walls). A correlation for the influence of various rod bowing phenomena on bundle critical power is developed. Good agreement with experimental data is shown.

Lin, W.S.; Pei, B.S. (National Tsing-Hua Univ., Dept. of Nuclear Engineering, Hsinchu 30043 (TW)); Lee, C.H. (Inst. of Nuclear Energy Research, Thermohydraulic Lab., P.O. Box 3-3, Lungtan 32500 (TW))

1992-06-01

216

Microstructure and spectroscopy studies on cubic boron nitride synthesized under high-pressure conditions  

CERN Document Server

High-resolution electron microscopy (HREM) studies of the microstructure and specific defects in hexagonal boron nitride (h-BN) precursors and cubic boron nitride (c-BN) crystals made under high-pressure high-temperature conditions revealed the presence of half-nanotubes at the edges of the h-BN particles. Their sp sup 3 bonding tendency could strongly influence the nucleation rates of c-BN. The atomic resolution at extended dislocations was insufficient to allow us to determine the stacking fault energy in the c-BN crystals. Its mean value of 191 pm, 15 mJ m sup - sup 2 is of the same order of magnitude as that of diamond. High-frequency (94 GHz) electron paramagnetic resonance studies on c-BN single crystals have produced new data on the D1 centres associated with the boron species. Ion-beam-induced luminescence measurements have indicated that c-BN is a very interesting luminescent material, which is characterized by four luminescence bands and exhibits a better resistance to ionizing radiation than CVD di...

Nistor, L C; Dinca, G; Georgeoni, P; Landuyt, J V; Manfredotti, C; Vittone, E

2002-01-01

217

Cutting and conditioning of the reactor pressure vessel in the NPP Wuergassen; Zerlegung und Konditionierung des Reaktordruckgefaesses im Kernkraftwerk Wuergassen  

Energy Technology Data Exchange (ETDEWEB)

NPP Wuergassen was shutdown in 1995 after 23 years of operation. Since 1997 the nuclear power plant is being dismantled. The cutting of the reactor pressure vessel internals was performed between 2003 and 2008. After decontamination the cylindrical parts of the reactor pressure vessel were dissected, the process was finalized in 2010. AREVA has now a 30 years-experience concerning repair, replacement and dismantling of reactor components. In the contribution the authors describe the process planning, manufacture and testing of appropriate remote handled tools, decontamination, dissection of the pressure vessel (320 t), conditioning, packaging and transport of the radioactive waste including radiation protection monitoring.

Kraps, Uwe [AREVA NP GmbH, Erlangen (Germany); Duwe, Peter [E.ON Kernkraft GmbH, Bewerungen (Germany)

2011-07-01

218

Generation of dielectric barrier discharge in high-pressure N2 and CO2 environments up to supercritical conditions  

International Nuclear Information System (INIS)

The generations of dielectric barrier discharge (DBD) in high-pressure nitrogen and carbon dioxide environments up to supercritical conditions with or without flow fields were performed. From the second positive system of nitrogen, the rotational temperature of N2 was estimated to be approximately 400 K under a supercritical N2 condition (4 MPa and 313 K). On the other hand, from emission spectra of DBD in a high-pressure CO2 environment (1-8 MPa), C2 and O spectra were remarkable in intensity instead of CO, CO+, CO2 and CO2 + spectra that were remarkable at atmospheric pressure. Furthermore, porous carbon film synthesis by DBD under a supercritical CO2 condition (7.5 MPa and 305 K) was also identified by scanning electron microscopy observation

2006-05-26

219

Adaptive generalized periodic boundary conditions for lattice Boltzmann simulations of pressure-driven flows through confined repetitive geometries  

Science.gov (United States)

An algorithm for an adaptive boundary condition for the simulation of fully developed, pressure driven flows using the lattice-Boltzmann method is introduced. The method simulates the effect of the solid walls confining a structure with dual periodicity, such as used in microfluidic devices. We combine a recently introduced boundary condition by Kim and Pitsch [Phys. Fluids 19, 108101 (2007)]10.1063/1.2780194 for the treatment of pressure driven flows in periodic structures with a controller loop that adjusts a perpendicular pressure gradient to suppress any net momentum perpendicular to the outer walls. The method’s accuracy in asymmetric geometries is tested against a periodic array structure that uses regularized zero-velocity boundary conditions as outer walls.

Gräser, Oliver; Grimm, Andrej

2010-07-01

220

COMPARISON OF VENTED AND ABSOLUTE PRESSURE TRANSDUCERS FOR WATER-LEVEL MONITORING IN HANFORD SITE CENTRAL PLATEAU WELLS  

Energy Technology Data Exchange (ETDEWEB)

Automated water-level data collected using vented pressure transducers deployed in Hanford Site Central Plateau wells commonly display more variability than manual tape measurements in response to barometric pressure fluctuations. To explain this difference, it was hypothesized that vented pressure transducers installed in some wells are subject to barometric pressure effects that reduce water-level measurement accuracy. Vented pressure transducers use a vent tube, which is open to the atmosphere at land surface, to supply air pressure to the transducer housing for barometric compensation so the transducer measurements will represent only the water pressure. When using vented transducers, the assumption is made that the air pressure between land surface and the well bore is in equilibrium. By comparison, absolute pressure transducers directly measure the air pressure within the wellbore. Barometric compensation is achieved by subtracting the well bore air pressure measurement from the total pressure measured by a second transducer submerged in the water. Thus, no assumption of air pressure equilibrium is needed. In this study, water-level measurements were collected from the same Central Plateau wells using both vented and absolute pressure transducers to evaluate the different methods of barometric compensation. Manual tape measurements were also collected to evaluate the transducers. Measurements collected during this study demonstrated that the vented pressure transducers over-responded to barometric pressure fluctuations due to a pressure disequilibrium between the air within the wellbores and the atmosphere at land surface. The disequilibrium is thought to be caused by the relatively long time required for barometric pressure changes to equilibrate between land surface and the deep vadose zone and may be exacerbated by the restriction of air flow between the well bore and the atmosphere due to the presence of sample pump landing plates and well caps. The disequilibrium is likely limited to wells screened across the water table (i.e., open to the deep vadose zone) where the depth to water is large or a low-permeability layer occurs in the vadose zone. Such wells are a pathway for air movement between the deep vadose zone and land surface and this sustains the pressure disequilibrium between the well bore and the atmosphere for longer time periods. Barometric over-response was not observed with the absolute pressure transducers because barometric compensation was achieved by directly measuring the air pressure within the well. Users of vented pressure transducers should be aware of the over-response issue in certain Hanford Site wells and ascertain if it will affect the use of the data. Pressure disequilibrium between the well and the atmosphere can be identified by substantial air movement through the wellbore. In wells exhibiting pressure disequilibrium, it is recommended that absolute pressure transducers be used rather than vented transducers for applications that require precise automated determinations of well water-level changes in response to barometric pressure fluctuations.

MCDONALD JP

2011-09-08

 
 
 
 
221

High-pressure phase transitions and subduction behavior of continental crust at pressure-temperature conditions up to the upper part of the lower mantle  

Science.gov (United States)

We precisely determined detailed phase relations of upper continental crust (UCC) at 20-28 GPa and 1200-1800 °C across the 660-km discontinuity conditions with a high-pressure multi-anvil apparatus. We used multi-sample chambers packed with both of UCC and pressure marker, and they were kept simultaneously at the same high-pressure and high-temperature conditions in each run. The high-pressure experiments were carried out in pressure and temperature intervals of about 1 GPa and 200 °C, respectively. At 22-25 GPa and 1600-1800 °C, UCC transformed from the assemblage of CaAl4Si2O11-rich phase (CAS)+clinopyroxene+garnet+hollandite+stishovite to that of calcium ferrite+calcium perovskite+hollandite+stishovite via the assemblage of CAS+calcium ferrite+calcium perovskite+garnet+hollandite+stishovite. No CAS was observed at 1200 °C. The textures and grain sizes in the run products suggested that hollandite (II) (monoclinic symmetry) was stable above 24-25 GPa and transformed to hollandite (I) (tetragonal symmetry) during decompression. We calculated the density of UCC at high pressure and high temperature from the mineral proportions which were calculated from the mineral compositions. UCC has a higher density than PREM up to 23.5 GPa in the range of 1200-1800 °C. Above 24 GPa, the density of UCC is lower than that of PREM at 1600-1800 °C, but is almost equal to that at 1400 °C and higher than PREM at temperature below 1400 °C. Therefore, we suggest that the subducted UCC may penetrate the 660-km discontinuity into the lower mantle, when its temperature is lower than 1400 °C at around 660 km depth.

Ishii, Takayuki; Kojitani, Hiroshi; Akaogi, Masaki

2012-12-01

222

Pressure-stability of phospholipid bicelles: Measurement of residual dipolar couplings under extreme conditions  

Energy Technology Data Exchange (ETDEWEB)

High-pressure NMR of proteins in solutions currently gains increasing interest. 3D structure determination of proteins under high pressure is, however, so far impossible due to the lack of NOE information. Residual dipolar couplings induced by the addition of magnetically orienting media are known to be capable of replacing NOE information to a very high extent. In the present contribution we study the pressure-wstability of dimyristoylphosphatidylcholine (DMPC)/ dihexanoylphosphatidylcholine (DHPC) bicelles and demonstrate the feasibility of measuring residual dipolar couplings in proteins under high pressure.

Brunner, E.; Arnold, M.R.; Kremer, W.; Kalbitzer, H.R. [University of Regensburg, Institute of Biophysics and Physical Biochemistry (Germany)

2001-10-15

223

Pressure-stability of phospholipid bicelles: Measurement of residual dipolar couplings under extreme conditions  

International Nuclear Information System (INIS)

High-pressure NMR of proteins in solutions currently gains increasing interest. 3D structure determination of proteins under high pressure is, however, so far impossible due to the lack of NOE information. Residual dipolar couplings induced by the addition of magnetically orienting media are known to be capable of replacing NOE information to a very high extent. In the present contribution we study the pressure-wstability of dimyristoylphosphatidylcholine (DMPC)/ dihexanoylphosphatidylcholine (DHPC) bicelles and demonstrate the feasibility of measuring residual dipolar couplings in proteins under high pressure

2001-10-01

224

Reactions of 1-tosyl-3-substituted indoles with conjugated dienes under thermal and/or high-pressure conditions.  

Science.gov (United States)

The behavior of 1-tosyl-3-acetylindole (1a), N,N-diethyl-1-tosyl-3-indoleglyoxylamide (1b), and 1-tosyl-3-nitroindole (1c) as dienophiles in Diels-Alder reactions under thermal and/or high-pressure conditions was explored with different dienes: isoprene (2), 1-(N-acetyl-N-propylamino)-1,3-butadiene (3), and 1-methoxy-3-trimethylsilyloxy-1,3-butadiene (Danishefsky's diene) (4). Compared to the acylated indoles, the nitro derivative proved to be the best dienophile. In general, the use of Danishefsky's diene led to high-yielding reactions under milder conditions. Likewise, high-pressure conditions proved to be better in producing high yields of products. The advantage of high-pressure over thermal conditions was the ability of the former to generate highly functionalized adducts in better yields, which were otherwise very difficult or impossible to obtain. The use of thermal or high-pressure conditions led to different regio- and/or stereoselectivity in the adducts, allowing control of the regio- or stereoisomer produced. PMID:11375014

Biolatto, B; Kneeteman, M; Paredes, E; Mancini, P M

2001-06-01

225

Transformation textures, mechanisms of formation of high-pressure minerals in shock melt veins of L6 chondrites, and pressure-temperature conditions of the shock events  

Science.gov (United States)

The high-pressure polymorphs of olivine, pyroxene, and plagioclase in or adjacent to shock melt veins (SMVs) in two L6 chondrites (Sahara 98222 and Yamato 74445) were investigated to clarify the related transformation mechanisms and to estimate the pressure-temperature conditions of the shock events. Wadsleyite and jadeite were identified in Sahara 98222. Wadsleyite, ringwoodite, majorite, akimotoite, jadeite, and lingunite (NaAlSi3O8-hollandite) were identified in Yamato 74445. Wadsleyite nucleated along the grain boundaries and fractures of original olivine. The nucleation and growth of ringwoodite occurred along the grain boundaries of original olivine, and as intracrystalline ringwoodite lamellae within original olivine. The nucleation and growth of majorite took place along the grain boundaries or fractures in original enstatite. Jadeite-containing assemblages have complicated textures containing “particle like,” “stringer-like,” and “polycrystalline-like” phases. Coexistence of lingunite and jadeite-containing assemblages shows a vein-like texture. We discuss these transformation mechanisms based on our textural observations and chemical composition analyses. The shock pressure and temperature conditions in the SMVs of these meteorites were also estimated based on the mineral assemblages in the SMVs and in comparison with static high-pressure experimental results as follows: 13-16 GPa, >1900 °C for Sahara 98222 and 17-24 GPa, >2100 °C for Yamato 74445.

Ozawa, S.; Ohtani, E.; Miyahara, M.; Suzuki, A.; Kimura, M.; Ito, Y.

2009-12-01

226

Sulphate chemistry under pressurized oxidizing, reducing and fluctuating conditions; Sulfatkemi under trycksatta oxiderande, reducerande och fluktuerande foerhaallanden  

Energy Technology Data Exchange (ETDEWEB)

In the literature it has been reported that sulfur capture with limestone (CaCO{sub 3}) under atmospheric fluidized bed combustion conditions reaches a maximum at about 850 deg C. Previously, the maximum has been attributed to the sintering of sorbent particles which decreases the reactive surface area. Lately, also another explanation has been reported. In this case the sulfur capture decrease at higher temperatures was concluded to be due to fluctuating oxidizing/reducing conditions in the atmospheric combustor. In this work the influence of alternating oxidizing/reducing conditions on SO{sub 2} capture at atmospheric and elevated pressure (15 bar) has been studied. In the pressurized case, the CO{sub 2} partial pressure was kept high enough to prevent CaCO{sub 3} from calcining and therefore the CaSO{sub 4} would not form CaO but CaCO{sub 3} under reducing conditions. The experiments were done with a pressurized TGA by periodically changing the gas environment between oxidizing (O{sub 2}. SO{sub 2}, CO{sub 2} and N{sub 2}) and slightly reducing (CO, SO{sub 2}, CO{sub 2} and N{sub 2}) gas mixtures at different temperatures. The results from the experiments showed that under normal pressure and slightly reducing conditions CaO formation from CaSO{sub 4} increased with temperature as expected. However, no significant amounts of CaCO{sub 3} were formed from CaSO{sub 4} at elevated pressure. It was also concluded that since the formation of CaO from CaSO{sub 4} was relatively slow it could not explain the sharp sulfur capture maximum at about 850 deg C. Therefore, it was assumed that the strongly reducing zones, where CaS thermodynamically is the stable compound, play a more important role concerning the sulfur capture in fluidized bed combustors. (orig.)

Hupa, M.; Yrjas, P.; Backman, P. [Aabo Akademi, Turku (Finland). Combustion Chemistry Research Group

1997-10-01

227

Multiple uncontrolled conditions and blood pressure medication intensification: an observational study  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Multiple uncontrolled medical conditions may act as competing demands for clinical decision making. We hypothesized that multiple uncontrolled cardiovascular risk factors would decrease blood pressure (BP medication intensification among uncontrolled hypertensive patients. Methods We observed 946 encounters at two VA primary care clinics from May through August 2006. After each encounter, clinicians recorded BP medication intensification (BP medication was added or titrated. Demographic, clinical, and laboratory information were collected from the medical record. We examined BP medication intensification by presence and control of diabetes and/or hyperlipidemia. 'Uncontrolled' was defined as hemoglobin A1c ? for diabetes, BP ? 140/90 mmHg (? 130/80 mmHg if diabetes present for hypertension, and low density lipoprotein cholesterol (LDL-c ? 130 mg/dl (? 100 mg/dl if diabetes present for hyperlipidemia. Hierarchical regression models accounted for patient clustering and adjusted medication intensification for age, systolic BP, and number of medications. Results Among 387 patients with uncontrolled hypertension, 51.4% had diabetes (25.3% were uncontrolled and 73.4% had hyperlipidemia (22.7% were uncontrolled. The BP medication intensification rate was 34.9% overall, but higher in individuals with uncontrolled diabetes and uncontrolled hyperlipidemia: 52.8% overall and 70.6% if systolic BP ? 10 mmHg above goal. Intensification rates were lowest if diabetes or hyperlipidemia were controlled, lower than if diabetes or hyperlipidemia were not present. Multivariable adjustment yielded similar results. Conclusions The presence of uncontrolled diabetes and hyperlipidemia was associated with more guideline-concordant hypertension care, particularly if BP was far from goal. Efforts to understand and improve BP medication intensification in patients with controlled diabetes and/or hyperlipidemia are warranted.

Halanych Jewell H

2010-07-01

228

Photochemical modelling of the Barcelona area under weak pressure synoptic summer conditions  

International Nuclear Information System (INIS)

This city of Barcelona and its surrounding area, located in the western Mediterranean basin, can reach high levels of O3 in summertime under weak pressure synoptic conditions. To study the origin of this photochemical pollution, the episode that took place between the 3 and 5 August 1990 was chosen. The main meteorological mesoscale flows that take place in the region, such as sea and land breeze, convection cells and topographic injections, were reproduced with the meteorological non-hydrostatic mesoscale model MEMO for 5 August 1990. Industrial and commercial activity on 5 August 1990 was very low because it was a Sunday in the summer holiday period. Therefore, the emissions inventory calculated for this day in an area of 80x80 km2 around Barcelona showed that the main sources of VOC were traffic (51%) and vegetation (34%), while NOx were mostly emitted by traffic (88%). Photochemical simulation with the MARS model has shown that the combination of mesoscale circulations and local emissions is crucial in the production of O3. For instance, NOx inland transport towards regions where biogenic VOC are emitted causes the formation of O3, while topographic injections cause the formation of elevated O3 air layers. The synoptic wind, coming from the northeast in this case, also played an important role in advecting the air masses with local generated O3 away from their precursor emission sources. Evaluation of the model simulations is also performed and discussed by means of comparison of meteorological measurements in 9 surface stations and concentration measurements in 5 surface stations. (Author)

1990-08-05

229

The Effects of Temperature, Pressure, and Humidity Variations on 100 Meter Sprint Performances  

CERN Multimedia

It is well known that ``equivalent'' sprint race times run with different accompanying wind speeds or at different altitudes are anything but equivalent races. The drag force acting on a sprinter is a function of air density and the relative wind speed, where the former has traditionally been calculated using the race venue's elevation above sea level. However, air density variation is dependent on more than just altitude. This work will quantify how changes in air temperature, barometric pressure, and humidity levels influence 100 m sprint performances. When these effects are considered in combination, the corrections to performances can be very large. The results suggest that a non-negligible difference in race times can be expected for ``equivalent'' performances run with the same wind speed at the same venue or physical altitude, but under different atmospheric conditions.

Mureika, J R

2005-01-01

230

Void fraction predictions in rod bundles at low-pressure low-flow conditions based on Cunningham-Yeh model  

International Nuclear Information System (INIS)

Many experiments have been conducted in the past with full-scale rod bundles to develop void fraction correlations or interfacial drag model which can be used to predict the mixture level in a reactor core following a postulated Loss of Coolant Accident (LOCA). The Cunningham and Yeh correlation was originally developed and validated with boil-off data obtained in the 100 to 400 psi pressure range. Subsequently the validity of the correlation was successfully assessed against several other experiments. However most of the data concentrated in the intermediate to high pressure range (from 100 to 2200 psi). More recently, the development of advanced passive plant such as the AP1000, put more emphasis in the level swell behavior in the near-atmospheric pressure conditions. Following a postulated SBLOCA event for the AP1000 design, the reactor vessel is automatically de-pressurized to a near atmospheric condition and in the long term the core decay heat is removed by gravity driven injection flow while boiling is occurring in the core. In this paper the Cunningham-Yeh correlation was assessed against data beyond its original data base. Cunningham-Yeh model predictions were compared to several low-flow, low-pressure full-scale rod bundle experiments. Results show that the correlation performs relatively well against low pressure test data. However the Cunningham-Yeh model has the tendency to underpredict the void fraction and therefore to provide conservative results of level swell for plant safety analysis. (authors)

2004-04-25

231

Sensory and physical changes in chilled farmed coho salmon (Oncorhynchus kisutch): Effect of previous optimized hydrostatic high-pressure conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of a previous hydrostatic high-pressure (HHP) treatment on sensory and physical quality of chilled coho salmon (Oncorhynchus kisutch) was investigated. As a first stage, a 22 factorial design based on the response surface methodology was used for optimization of HHP conditions; for it, the effects on color uniformity, white spots appearance, elasticity, and hardness were analyzed. In a second stage, optimized HHP conditions (135 MPa for 30 s, 170 MPa for 30 s, and 200 MPa for 30 s;...

2012-01-01

232

Leakage rate through a non-cracked concrete wall, comparison between two situations: Air pressure test and accident conditions  

International Nuclear Information System (INIS)

This experimental research investigated the behaviour of a concrete wall, with a local zone very permeable to air, subjected to accident conditions. The high level of permeability in the concrete was obtained for one specimen with a porous concrete having connected pores (intrinsic permeability of 10-16 m2). The aim of this work was to study comparatively, in the laboratory, the permeability of a non-cracked concrete wall under two conditions. A cylindrical specimen 1.3 m thick was used. No appreciable stresses were applied on the concrete. The first condition was at ambient temperature, under an increasing pressure (up to 0.42 MPa) of the air applied on one face of the specimen, the other one being at atmospheric pressure. The second condition was an accident scenario with simultaneous effects of temperature and gas (a mix of air and steam) pressure applied on one face, the other one remaining at atmospheric pressure and temperature. During the test, the lateral face of the cylindrical specimen was thermally isolated and made leak tight. So, a uni-dimensional experimental analysis was performed. The accident conditions consisted of a rise from ambient conditions to a temperature of 141 deg C and a relative pressure of 0.42 MPa (steam pressure of 0.377 MPa and air pressure of 0.043 MPa) for 3 h, the maximum values remaining constant for several days. Thermocouples, pressure taps and moisture gauges were implanted in the specimens at the moment of casting, to provide local information about the inner wall under the simultaneous effects of temperature and steam pressure. Outside the specimen, the chamber enclosed a condenser with a humidity meter and thermocouple, so it was possible to quantify separately the saturated airflow with a flow-metre and the condensed water. During the permeability test at ambient temperature, the field of pressure was affected by the variation of local permeability of the concrete. Furthermore, some movement of interstitial water inside the specimen induced an increase of the predicted outflow, no liquid phase appeared. For the natural porous concrete, during accident testing, the field of pressure advanced slowly, the outflow progressively increased to obtain a maximum at 70 h, after this time on the one hand the airflow rate decreased and became equal to zero; on the other hand, the liquid flow rate was constant, at the end of the test, about 30 cm of the specimen was water saturated. A uni-dimensional numerical analysis was performed. The Tham model (non-saturated porous media thermo-hydro-mechanic) included in CodeAster[reg] was used. Two fluid phases can be considered in the material: a liquid phase (water) and a gas phase (dry air plus vapour) with the liquid/vapour phase changes. The thermodynamic aspects dealt with open systems framework, with temperature, capillary pressure and gas total pressure as variables. Observing the considered conditions (progressive saturation of the wall), the shape of sorption isotherm and permeabilities had an important influence on the results. The numerical results were in good agreement with experimental results, on the phenomenology and on flow rate through the wall. This study gave some indicators about the relations between airflow during a permeability test and gas (air + steam) flows during accident testing

2005-08-01

233

Asymptotic-numerical derivation of the Robin type coupling conditions for the macroscopic pressure at a reservoir-capillaries interface  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this article the Stokes equations are considered in a domain simulating a capillary bed system. The capillaries are supposed to be thin, parallel and periodic. An asymptotic approximation is constructed. The macroscopic pressure satisfies a Robin interface condition whose coefficients are calculated numerically through a finite element approximation of a boundary layer problem, which is inspired to a domain decomposition technique.

2013-01-01

234

Containment pressure response to a meltdown condition of the light water reactor  

International Nuclear Information System (INIS)

A one cell simplified containment pressure model is incorporated into the CORCON/MOD1 code in order to study the impact of different heat transfer correlations on the containment pressurization. The effect of heat absorbed in the containment concrete wall was also studied. The results show that the downward heat transfer is important in determining the concrete ablation rate, but the containment pressurization rate is not affected much for the cases studied. It is also shown that the heat conducted into the concrete wall is a very important inherent heat sink

1986-03-01

235

Seasonal variation in the incidence of preeclampsia and eclampsia in tropical climatic conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Observational studies have demonstrated various correlations between hypertensive disorders of pregnancy and different weather parameters. We aim to study if a correlation exists between the incidence of eclampsia and pre-eclampsia and various weather parameters in the tropical coastal city of Mumbai which has the distinction of having relatively uniform meteorological variables all throughout the year, except for the monsoon season. Methods We retrospectively analysed data from a large maternity centre in Mumbai, India over a period of 36 months from March 1993 to February 1996, recording the incidence of preeclampsia and eclampsia. Meteorological data was acquired from the regional meteorological centre recording the monthly average temperature, humidity, barometric pressure and rainfall during the study period. Study period was then divided into two climate conditions: monsoon season (June to August and dry season September to May. The incidence of preeclampsia and eclampsia and the meteorological differences between the two seasons were compared. Results Over a 36-month period, a total of 29562 deliveries were recorded, of which 1238 patients developed preeclampsia (4.18% and 34 developed eclampsia (0.11%. The incidence of preeclampsia did not differ between the monsoon and the dry season (4.3% vs. 4.15%, p = 0.5. The incidence of eclampsia was significantly higher in the monsoon (0.2% vs. 0.08%, p = 0.01. The monsoon was significantly cooler (median maximum temperature 30.7°C vs. 32.3°C, p = 0.01, more humid (median relative humidity 85% vs. 70%, p = 0.0008, and received higher rainfall (median 504.9 mm vs. 0.3 mm, p = 0.0002 than the rest of the year. The median barometric pressure (1005 mb during the monsoon season was significantly lower than the rest of the year (1012 mb, p Conclusion In the tropical climate of Mumbai, the incidence of eclampsia is significantly higher in monsoon, when the weather is cooler and humid with a lower barometric pressure than the rest of the year. This effect is not seen with preeclampsia. This strengthens the association of low temperature and high humidity with triggering of eclampsia.

Subramaniam Vidya

2007-10-01

236

Electronic properties of Fabre charge-transfer salts under various temperature and pressure conditions  

Science.gov (United States)

Using density functional theory, we determine parameters of tight-binding Hamiltonians for a variety of Fabre charge transfer salts, focusing, in particular, on the effects of temperature and pressure. Besides relying on previously published crystal structures, we experimentally determine two new sets of structures: (TMTTF)2SbF6 at different temperatures and (TMTTF)2PF6 under various hydrostatic pressures. We find that a few trends in the electronic behavior can be connected to the complex phase diagram shown by these materials. Decreasing temperature and increasing pressure cause the systems to become more two dimensional. We analyze the importance of correlations by considering an extended Hubbard model parameterized using Wannier orbital overlaps and show that while charge order is strongly activated by the intersite Coulomb interaction, the magnetic order is only weakly enhanced. Both orders are suppressed when the effective pressure is increased.

Jacko, A. C.; Feldner, H.; Rose, E.; Lissner, F.; Dressel, M.; Valentí, Roser; Jeschke, Harald O.

2013-04-01

237

Pressure conditions for the local regularity of solutions of the Navier-Stokes equations  

Directory of Open Access Journals (Sweden)

Full Text Available We obtain a relationship between the integrability of the pressure gradient and the the integrability of the velocity for local solutions of the Navier--Stokes equations with finite energy. In particular, we show that if the pressure gradient is sufficiently integrable, then the corresponding velocity is locally bounded and smooth in the spatial variables. The result is proven by using De Giorgi type estimates in $L^{ m weak}_p$ spaces.

Mike O'Leary

1998-05-01

238

SOLUTE CLUSTERING AND PRECIPITATION IN PRESSURE VESSEL STEELS UNDER LOW FLUENCE IRRADIATION CONDITIONS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The microstructural features present in reactor pressure vessel steels after low fluence neutron irradiation have been characterized by atom probe field-ion microscopy. Unlike the clusters and precipitates which have been reported in pressure vessel steels irradiated to intermediate and higher fluences, very diffuse solute-enriched atmospheres have been observed. Although copper is associated with a high proportion of these atmospheres, phosphorus appears to play a more dominant role in the f...

1988-01-01

239

Effect of Normal Operating Condition Analysis Method for Weld Residual Stress of CD-ROM Nozzle in Reactor Pressure Vessel  

International Nuclear Information System (INIS)

In pressurized water nuclear reactors (PWRs), the reactor pressure vessel (RSV) upper head contains penetration nozzles that use a control rod drive mechanism (CD-ROM). The penetration nozzle uses J-groove weld geometry. Recently, the occurrence of cracking in alloy 600 CD-ROM penetration nozzle has increased. This is attributable to primary water stress corrosion cracking (PWSCC). PWSCC is known to be susceptible to the welding residual stress and operational stress. Generally, the tensile residual stress is the main factor contributing to crack growth. Therefore, this study investigates the effect on weld residual stress through different analysis methods for normal operating conditions using finite element analysis. In addition, this study also considers the effect of repeated normal operating condition cycles on the weld residual stress. Based on the analysis result, this paper presents a normal operating condition analysis method

2013-09-01

240

Effect of Normal Operating Condition Analysis Method for Weld Residual Stress of CD-ROM Nozzle in Reactor Pressure Vessel  

Energy Technology Data Exchange (ETDEWEB)

In pressurized water nuclear reactors (PWRs), the reactor pressure vessel (RSV) upper head contains penetration nozzles that use a control rod drive mechanism (CD-ROM). The penetration nozzle uses J-groove weld geometry. Recently, the occurrence of cracking in alloy 600 CD-ROM penetration nozzle has increased. This is attributable to primary water stress corrosion cracking (PWSCC). PWSCC is known to be susceptible to the welding residual stress and operational stress. Generally, the tensile residual stress is the main factor contributing to crack growth. Therefore, this study investigates the effect on weld residual stress through different analysis methods for normal operating conditions using finite element analysis. In addition, this study also considers the effect of repeated normal operating condition cycles on the weld residual stress. Based on the analysis result, this paper presents a normal operating condition analysis method.

Nam, Hyun Suk; Bae, Hong Yeol; Oh, Chang Young; Kim, Ji Soo; Kim, Yun Jae [Korea Univ., Seoul (Korea, Republic of)

2013-09-15

 
 
 
 
241

EXAFS measurements under high pressure conditions using a combination of a diamond anvil cell and synchrotron radiation  

International Nuclear Information System (INIS)

EXAFS spectra for Fe, Co, Ni K-edges were successfully measured under high pressure conditions using a combination of a set of normal 1/8 carat diamond anvils, synchrotron radiation and a scintillation counter. A newly developed motor controlled goniometer stage was used for adjusting the position of a miniature diamond anvil cell. On the measurement of Cr and Mn spectra, specially designed thinner diamond anvil was necessary. EXAFS analysis of bis(dimethylglyoximato)nickel(II) at pressures from 1 atm to 5.6 GPa was made. (author)

1986-01-01

242

Effect of different reaction atmospheres on the sintering temperature of Jincheng coal ash under pressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

The sintering temperature of coal ash is studied to further understand ash behavior. The objective of this study is to obtain a detailed understanding of the effect of the reaction atmospheres on the sintering temperature under elevated pressure. A series of experiments and analyses have been completed using a pressurized pressure-drop measuring device and X-ray diffractometer (XRD) analyzer. The results show that the sintering temperatures decline markedly under all reaction atmospheres with the rise in pressure. The pressure influences the sintering temperatures by affecting the reaction rate and the mineral transformations undergone by the coal ash, as observed from the XRD patterns. The sintering temperatures measured under the reducing reaction atmospheres are lower than those for oxidizing atmospheres. The sintering temperature under N{sub 2} is lower than those under other oxidizing atmospheres. The sintering temperature under the gasification atmosphere is close to those under H{sub 2} and CO atmospheres, whereas the sintering temperature under a H{sub 2} atmosphere is lower than that under a CO atmosphere. 19 refs., 6 figs., 3 tabs.

Nijie Jing; Qinhui Wang; Zhongyang Luo; Kefa Cen [Zhejiang University, Hangzhou (China). State Key Laboratory of Clean Energy Utilization

2011-08-15

243

Synthesis of novel Ru2C under high pressure-high temperature conditions  

International Nuclear Information System (INIS)

We report here, for the first time, synthesis of the Fe2N type hexagonal phase of ruthenium carbide by a high pressure-high temperature technique using a laser heated diamond anvil cell (LHDAC). The synthesis is carried out by laser heating a mixture of pure elements, Ru and C, at very low ‘pressure’ of 5 GPa and T ? 2000 K. The structure of the temperature quenched high pressure phase is characterized by in situ high pressure x-ray diffraction (HPXRD) and is corroborated by ex situ TEM imaging and diffraction, carried out for the first time on the retrieved sample synthesized by LHDAC. The lattice parameters of Ru2C at ambient pressure are found to be a = 2.534 ? and c = 4.147 ?. In situ HPXRD studies up to 14.2 GPa yield a bulk modulus of 178(4) GPa. Electronic structure calculations reveal the system to be metallic in nature with a degree of covalence along the Ru-C bond. As ruthenium is isoelectronic to osmium, this result for Ru2C has significant implications in the synthesis and study of osmium carbides.

2012-09-12

244

Osmosis-induced water uptake by Eurobitum bituminized radioactive waste and pressure development in constant volume conditions  

International Nuclear Information System (INIS)

Highlights: ? The water uptake by Eurobitum is studied to judge the safety of geological disposal. ? High pressures of up to 20 MPa are measured in constant volume water uptake tests. ? The morphology of leached Eurobitum samples is studied with ?CT and ESEM. ? The observations are reproduced by an existing CHM formulation for Eurobitum. - Abstract: The chemo-hydro-mechanical (CHM) interaction between swelling Eurobitum radioactive bituminized waste (BW) and Boom Clay is investigated to assess the feasibility of geological disposal for the long-term management of this waste. These so-called compatibility studies include laboratory water uptake tests at Belgian Nuclear Research Center SCK-CEN, and the development of a coupled CHM formulation for Eurobitum by the International Center for Numerical Methods and Engineering (CIMNE, Polytechnical University of Cataluña, Spain). In the water uptake tests, the osmosis-induced swelling, pressure increase and NaNO3 leaching of small cylindrical BW samples (diameter 38 mm, height 10 mm) is studied under constant total stress conditions and nearly constant volume conditions; the actual geological disposal conditions should be intermediate between these extremes. Two nearly constant volume tests were stopped after 1036 and 1555 days to characterize the morphology of the hydrated BW samples and to visualize the hydrated part with microfocus X-ray Computer Tomography (?CT) and Environmental Scanning Electron Microscopy (ESEM). In parallel, a coupled CHM formulation is developed that describes chemically and hydraulically coupled flow processes in porous materials with salt crystals, and that incorporates a porosity dependent membrane efficiency, permeability and diffusivity. When Eurobitum BW is hydrated in (nearly) constant volume conditions, the osmosis-induced water uptake results in an increasing pressure to values that can be (in theory) as high as 42.8 MPa, being the osmotic pressure of a saturated NaNO3 solution. After about four years of hydration in nearly constant volume water uptake tests, pressures up to 20 MPa are measured. During this hydration period only the outer layers with a thickness of 1–2 mm were hydrated (as derived from ?CT and ESEM analyses), and only about 10–20% of the initial NaNO3 content was released by the samples. In the studied test conditions, the rates of water uptake and NaNO3 leaching are low because of the low porosity, and thus low permeability, of the hydrated BW samples in combination with a highly efficient semi-permeable bitumen membrane. In contrast to the hydration in free swelling conditions, the increase in porosity is limited by the high pressures in the nearly constant volume tests. Furthermore, at the interface with the stainless steel filters, a low permeable re-compressed bitumen layer is formed, as observed on the ESEM images. The experimental results of pressure increase and NaNO3 leaching, as well as observations on ?CT and ESEM images (e.g. compression of leached layers, high dissolved NaNO3 concentration in hydrated BW after about four years), were reproduced rather successfully by the coupled CHM formulation for Eurobitum BW. A long-term model prediction of the evolution of the osmosis-induced pressure in the nearly constant volume tests shows that the pressure would reach a maximal value of about 20 MPa after about 5.5 years, after which the pressure would start to decrease. After 10,000 days (?27 years) the pressure would have decreased to a value of ?2 MPa.

2013-01-01

245

Osmosis-induced water uptake by Eurobitum bituminized radioactive waste and pressure development in constant volume conditions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer The water uptake by Eurobitum is studied to judge the safety of geological disposal. Black-Right-Pointing-Pointer High pressures of up to 20 MPa are measured in constant volume water uptake tests. Black-Right-Pointing-Pointer The morphology of leached Eurobitum samples is studied with {mu}CT and ESEM. Black-Right-Pointing-Pointer The observations are reproduced by an existing CHM formulation for Eurobitum. - Abstract: The chemo-hydro-mechanical (CHM) interaction between swelling Eurobitum radioactive bituminized waste (BW) and Boom Clay is investigated to assess the feasibility of geological disposal for the long-term management of this waste. These so-called compatibility studies include laboratory water uptake tests at Belgian Nuclear Research Center SCK-CEN, and the development of a coupled CHM formulation for Eurobitum by the International Center for Numerical Methods and Engineering (CIMNE, Polytechnical University of Cataluna, Spain). In the water uptake tests, the osmosis-induced swelling, pressure increase and NaNO{sub 3} leaching of small cylindrical BW samples (diameter 38 mm, height 10 mm) is studied under constant total stress conditions and nearly constant volume conditions; the actual geological disposal conditions should be intermediate between these extremes. Two nearly constant volume tests were stopped after 1036 and 1555 days to characterize the morphology of the hydrated BW samples and to visualize the hydrated part with microfocus X-ray Computer Tomography ({mu}CT) and Environmental Scanning Electron Microscopy (ESEM). In parallel, a coupled CHM formulation is developed that describes chemically and hydraulically coupled flow processes in porous materials with salt crystals, and that incorporates a porosity dependent membrane efficiency, permeability and diffusivity. When Eurobitum BW is hydrated in (nearly) constant volume conditions, the osmosis-induced water uptake results in an increasing pressure to values that can be (in theory) as high as 42.8 MPa, being the osmotic pressure of a saturated NaNO{sub 3} solution. After about four years of hydration in nearly constant volume water uptake tests, pressures up to 20 MPa are measured. During this hydration period only the outer layers with a thickness of 1-2 mm were hydrated (as derived from {mu}CT and ESEM analyses), and only about 10-20% of the initial NaNO{sub 3} content was released by the samples. In the studied test conditions, the rates of water uptake and NaNO{sub 3} leaching are low because of the low porosity, and thus low permeability, of the hydrated BW samples in combination with a highly efficient semi-permeable bitumen membrane. In contrast to the hydration in free swelling conditions, the increase in porosity is limited by the high pressures in the nearly constant volume tests. Furthermore, at the interface with the stainless steel filters, a low permeable re-compressed bitumen layer is formed, as observed on the ESEM images. The experimental results of pressure increase and NaNO{sub 3} leaching, as well as observations on {mu}CT and ESEM images (e.g. compression of leached layers, high dissolved NaNO{sub 3} concentration in hydrated BW after about four years), were reproduced rather successfully by the coupled CHM formulation for Eurobitum BW. A long-term model prediction of the evolution of the osmosis-induced pressure in the nearly constant volume tests shows that the pressure would reach a maximal value of about 20 MPa after about 5.5 years, after which the pressure would start to decrease. After 10,000 days ({approx}27 years) the pressure would have decreased to a value of {approx}2 MPa.

Marieen, A., E-mail: amarien@sckcen.be [Waste and Disposal Expert Group, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, 2400 Mol (Belgium); Mokni, N., E-mail: Nadia.mokni@upc.edu [Department of Geotechnical Engineering and Geosciences, Universidad Politecnica de Catalunya (UPC), Calle Gran Capitan, s/n, Edificio C-1, 08034 Barcelona (Spain); Valcke, E. [Waste and Disposal Expert Group, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, 2400 Mol (Belgium); Olivella, S. [Department of Geotechnical Engineering and Geosciences, Universidad Politecnica de Catalunya (UPC), Calle Gran Capitan, s/n, Edificio C-1, 08034 Barcelona (Spain); Smets, S. [Waste and Disposal Expert Group, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, 2400 Mol (Belgium); Li, X., E-mail: xli@sckcen.be [EIG EURIDICE, Boeretang 200, 2400 Mol (Belgium)

2013-01-15

246

Void fraction under high pressure, low flow conditions in rod bundle geometry  

International Nuclear Information System (INIS)

Void-fraction data are reported from a series of high pressure, low heat and mass flux experiments. Testing was performed in a heated vertical rod bundle with internal dimensions similar to a PWR fuel bundle. The results are of interest in analyses of small break loss of coolant accidents. The experiments showed that, at a given pressure, void-fraction data could be fitted to a drift-flux equation with a constant drift-velocity. The drift-velocity was observed to decrease with increasing pressure and was independent of void fraction: a characteristic normally associated with churn-turbulent flow. However, relevant drift-flux correlations found in the literature gave relatively poor predictions of void fractions. The best predictions were obtained from an empirical correlation based on dimensional analyses. (orig.)

1983-04-01

247

Bacterial carbon dependence on freshly produced phytoplankton exudates under different nutrient availability and grazing pressure conditions in coastal marine waters.  

Science.gov (United States)

The effects of grazing pressure and inorganic nutrient availability on the direct carbon transfer from freshly produced phytoplankton exudates to heterotrophic bacteria biomass production were studied in Mediterranean coastal waters. The short-term incorporation of ¹³C (H¹³CO?) in phytoplankton and bacterial lipid biomarkers was measured as well as the total bacterial carbon production (BP), viral lysis and the microbial community structure under three experimental conditions: (1) High inorganic Nutrient and High Grazing (HN + HG), (2) High inorganic Nutrient and Low Grazing (HN + LG) and (3) under natural in situ conditions with Low inorganic Nutrient and High Grazing (LN + HG) during spring. Under phytoplankton bloom conditions (HN + LG), the bacterial use of freshly produced phytoplankton exudates as a source of carbon, estimated from ¹³C enrichment of bacterial lipids, contributed more than half of the total bacterial production. However, under conditions of high grazing pressure on phytoplankton with or without the addition of inorganic nutrients (HN + HG and LN + HG), the ¹³C enrichment of bacterial lipids was low compared with the high total bacterial production. BP therefore seems to depend mainly on freshly produced phytoplankton exudates during the early phase of phytoplankton bloom period. However, BP seems mainly relying on recycled carbon from viral lysis and predators under high grazing pressure. PMID:24741704

Fouilland, Eric; Tolosa, Imma; Bonnet, Delphine; Bouvier, Corinne; Bouvier, Thierry; Bouvy, Marc; Got, Patrice; Le Floc'h, Emilie; Mostajir, Behzad; Roques, Cécile; Sempéré, Richard; Sime-Ngando, Télesphore; Vidussi, Francesca

2014-03-01

248

Operating liquid-fuel airblast injectors in low-pressure test rigs: strategies for scaling down the flow conditions  

Energy Technology Data Exchange (ETDEWEB)

For reasons of economy, gas turbine atomizers are often tested at lower pressures and temperatures than exist in the engine. The spray behaviour differs in the rig from that in the engine. For good measurement practice it is necessary to find rig operating conditions at which the aspect of the two phase flow being measured (e.g. patternation, droplet size) is similar in the rig to that in the engine. We describe a number of strategies for finding operating conditions which allow good measurement. These conditions reduce the air and fuel flow rates below engine values but conserve certain flow quantities. We define an error function to quantify how well the rig conditions match key non-dimensional groups. We consider an example of a typical aero gas turbine airblast atomizer operated in a rig at 323 K. To preserve patternation it is desirable to conserve the Reynolds (Re), Mach (Ma) and Stokes (Stk) numbers. A perfect match is not possible but we find a number of acceptable compromise strategies. The match improves as the rig pressure increases up to {approx}600 kPa where Re and Ma are matched and Stk is correct to an order of magnitude. Further pressure increase gives little improvement. It may be possible to match Stk by using a different fuel. (author)

Jermy, M.C.; Hussain, M.; Greenhalgh, D.A. [Cranfield Univ. (United Kingdom). School of Engineering

2003-07-01

249

Operating liquid-fuel airblast injectors in low-pressure test rigs: strategies for scaling down the flow conditions  

Science.gov (United States)

For reasons of economy, gas turbine atomizers are often tested at lower pressures and temperatures than exist in the engine. The spray behaviour differs in the rig from that in the engine. For good measurement practice it is necessary to find rig operating conditions at which the aspect of the two phase flow being measured (e.g. patternation, droplet size) is similar in the rig to that in the engine. We describe a number of strategies for finding operating conditions which allow good measurement. These conditions reduce the air and fuel flow rates below engine values but conserve certain flow quantities. We define an error function to quantify how well the rig conditions match key non-dimensional groups. We consider an example of a typical aero gas turbine airblast atomizer operated in a rig at 323 K. To preserve patternation it is desirable to conserve the Reynolds (Re), Mach (Ma) and Stokes (Stk) numbers. A perfect match is not possible but we find a number of acceptable compromise strategies. The match improves as the rig pressure increases up to ~600 kPa where Re and Ma are matched and Stk is correct to an order of magnitude. Further pressure increase give little improvement. It may be possible to match Stk by using a different fuel.

Jermy, M. C.; Hussain, M.; Greenhalgh, D. A.

2003-07-01

250

Synthesis of Gd2Zr2O7 pyrochlore with a cubic structure at high pressure and temperature conditions  

International Nuclear Information System (INIS)

To investigate the possibility to synthesize cubic pyrochlore Gd2Zr2O7 by solid-solid reactions under high pressure and high temperature conditions, experiments were carried out at a fixed pressure of 5.2 GPa and a temperature range of 1573-1873 K using the mixed powders of Gd2O3 and ZrO2 as starting materials. The as-synthesized samples were characterized by XRD. The results show that a single phase compound Gd2Zr2O7 with a cubic pyrochlore structure was successfully synthesized at the applied pressure and 1873 K temperature with 30 min holding time. The novel method has vitally scientific values and practical significance for the researches on immobilization of plutonium and 'minor' actinides. (authors)

2010-11-01

251

Safety related studies on zircaloy cladding and Zr-2.5%Nb pressure tube under simulated LOCA conditions  

International Nuclear Information System (INIS)

The behavior of PHWR fuel pins and the pressure tubes under off-normal and postulated accident conditions of the reactor is not well understood. There is a need to carry out experimental studies to generate data and to develop understanding of fuel, cladding and pressure tube behaviour in order to develop and validate computer models. In view of this, an experimental program has been started to study (i) high temperature steam oxidation and embrittlement of zircaloy cladding used in PHWR fuel pins (ii) High temperature oxidation study of Zr-2.5%Nb pressure tube to generate kinetic data in the temperature range 500-1000 deg C and (iii) study of high temperature deformation and failure behaviour of Zircaloy cladding in the temperature range 700-900 deg C using irradiated fuel pins. This paper presents the details of the study and important findings

2011-02-09

252

Crack growth behaviour of low-alloy steels for pressure boundary components under transient light water reactor operating conditions - CASTOC, Part I: BWR/NWC conditions  

International Nuclear Information System (INIS)

One of the ageing phenomena of pressure boundary components of light water reactors (LWR) is environmentally-assisted cracking (EAC). The project CASTOC (5. Framework Programme of the EU) was launched September 2000 with six European partners and terminated August 2003. It was focused in particular on the EAC behaviour of low-alloy steels (LAS) and to some extent to weld metal, heat affected zone and the influence of an austenitic cladding. The main objective was directed to the clarification of EAC crack growth behaviour/mechanism of LAS in high-temperature water under steady-state power operation (constant load) and transient operating conditions (e.g., start-up/shut-down, transients in water chemistry and load). Autoclave tests were performed with Western and Russian type reactor pressure vessel steels under simulated boiling water reactor (BWR)/normal water chemistry (NWC) and pressurised water reactor (VVER) conditions. The investigations were performed with fracture mechanics specimens of different sizes and geometries. The applied loading comprised cyclic loads, static loads and load spectra where the static load was periodically interrupted by partial unloading. With regard to water chemistry, the oxygen content (VVER) and impurities of sulphate and chlorides (BWR) were varied beyond allowable limits for continuous operation. The current paper summarises the most important crack growth results obtained under simulated BWR/NWC conditions. The results are discussed in the context of the current crack growth rate curves in the corresponding nuclear codes. (authors)

2004-09-12

253

The pressurized suit and some considerations leading to the development of physiologically safe working conditions  

International Nuclear Information System (INIS)

The safe working environment of men wearing pressurized suits in the U.K.A.E.A. is based on the results of two experimental programmes, the first investigated the respiratory hazards, the second the assessment and control of the level of thermal stress. Both are described. (author)

1980-01-01

254

Experimental investigation of sagging of a completely voided pressure tube of Indian PHWR under heatup condition  

Energy Technology Data Exchange (ETDEWEB)

Pressure tube (zirconium 2.5 wt.% Nb) serves as a pressure boundary for the coolant that removes nuclear heat generated in the reactor core of Indian Pressurised Heavy Water Reactors (IPHWRs). Under postulated low frequency (<10{sup -6} per year) accidents like Loss of Coolant Accident (LOCA) along with failure of Emergency Core Cooling System (ECCS) injection, heatup of pressure tube (PT) combined with internal pressure and the weight of the fuel bundle may lead to deformation. The extent and nature of deformation is important from reactor safety point of view. An experimental set-up has been designed and fabricated to simulate sagging (downward deformation) of PT due to its own weight and the weight of fuel bundles for 220 MWe IPHWRs. Experiments are conducted at different heatup rates of voided PTs. It is observed that sagging initiates at a temperature around 450 {sup o}C. Contact between PT and calandria tube (CT) occurs at around 585-625 {sup o}C, respectively. Once PT-CT contact takes place, PT temperature either decreases or the temperature rise remains controlled whereas CT temperature keeps on increasing for next 20-30 s. The contact location in all the experiments was near the centre of the tube. Structural integrity of PT is retained (no breach) for all the experiments. The PT temperature rise is found to be arrested after the contact between PT and CT, thus establishing that moderator acts as an efficient heat sink for IPHWRs.

Nandan, Gopal [Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667 (India); Sahoo, P.K., E-mail: sahoofme@iitr.ernet.i [Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667 (India); Kumar, Ravi [Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667 (India); Chatterjee, B.; Mukhopadhyay, D.; Lele, H.G. [Reactor Safety Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India)

2010-10-15

255

Experimental investigation of sagging of a completely voided pressure tube of Indian PHWR under heatup condition  

International Nuclear Information System (INIS)

Pressure tube (zirconium 2.5 wt.% Nb) serves as a pressure boundary for the coolant that removes nuclear heat generated in the reactor core of Indian Pressurised Heavy Water Reactors (IPHWRs). Under postulated low frequency (-6 per year) accidents like Loss of Coolant Accident (LOCA) along with failure of Emergency Core Cooling System (ECCS) injection, heatup of pressure tube (PT) combined with internal pressure and the weight of the fuel bundle may lead to deformation. The extent and nature of deformation is important from reactor safety point of view. An experimental set-up has been designed and fabricated to simulate sagging (downward deformation) of PT due to its own weight and the weight of fuel bundles for 220 MWe IPHWRs. Experiments are conducted at different heatup rates of voided PTs. It is observed that sagging initiates at a temperature around 450 oC. Contact between PT and calandria tube (CT) occurs at around 585-625 oC, respectively. Once PT-CT contact takes place, PT temperature either decreases or the temperature rise remains controlled whereas CT temperature keeps on increasing for next 20-30 s. The contact location in all the experiments was near the centre of the tube. Structural integrity of PT is retained (no breach) for all the experiments. The PT temperature rise is found to be arrested after the contact between PT and CT, thus establishing that moderator acts as an efficient heat sink for IPHWRs.

2010-10-01

256

Aluminum oxide films deposited in low pressure conditions by reactive pulsed dc magnetron sputtering  

CERN Multimedia

The reactive pulsed dc sputtering technique is widely used for the deposition of oxide films. The operating pressure for sputtering is commonly above 0.13 Pa. In this study, however, aluminum oxide (alumina) films were deposited at operating pressures from 0.06 to 0.4 Pa using a sputtering system equipped with a scanning magnetron cathode and a pulsed dc power supply. The pulsed dc power was found to be useful not only to reduce arcing, but also to sustain the discharge at low pressure. The electrical breakdown field, intrinsic stress, O/Al ratio, refractive index, and surface roughness were investigated. Both a low intrinsic stress and an O/Al ratio around the stoichiometry were required to get the film having a high breakdown field. A low operating pressure of 0.1 Pa was found to provide the necessary stress and O/Al ratio targets. A 50-nm-thick alumina film having a maximum breakdown field of 7.4 MV/cm was obtained.

Seino, T

2002-01-01

257

Multiphase Binary Mixture Flows in Porous Media in a Wide Pressure and Temperature Range Including Critical Conditions  

Science.gov (United States)

Multiphase flows in porous media with a transition between sub- and supercritical thermodynamic conditions occur in many natural and technological processes (e.g. in deep regions of geothermal reservoirs where temperature reaches critical point of water or in gas-condensate fields where subject to critical conditions retrograde condensation occurs and even in underground carbon dioxide sequestration processes at high formation pressure). Simulation of these processes is complicated due to degeneration of conservation laws under critical conditions and requires non-classical mathematical models and methods. A new mathematical model is proposed for efficient simulation of binary mixture flows in a wide range of pressures and temperatures that includes critical conditions. The distinctive feature of the model lies in the methodology for mixture properties determination. Transport equations and Darcy law are solved together with calculation of the entropy maximum that is reached in thermodynamic equilibrium and determines mixture composition. To define and solve the problem only one function - mixture thermodynamic potential - is required. Such approach allows determination not only single-phase states and two-phase states of liquid-gas type as in classical models but also two-phase states of liquid-liquid type and three-phase states. The proposed mixture model was implemented in MUFITS (Multiphase Filtration Transport Simulator) code for hydrodynamic simulations. As opposed to classical approaches pressure, enthalpy and composition variables together with fully implicit method and cascade procedure are used. The code is capable of unstructured grids, heterogeneous porous media, relative permeability and capillary pressure dependence on temperature and pressure, multiphase diffusion, optional number of sink and sources, etc. There is an additional module for mixture properties specification. The starting point for the simulation is a cubic equation of state that is used for mixture thermodynamic potential - entropy - calculation in pressure, enthalpy and composition variables. A polynomial spline is implemented to save the potential for subsequent hydrodynamic simulations. At this stage the majority of complicated thermodynamic procedures are performed prior to hydrodynamic that results in sufficient acceleration of calculations. The code was used for analysis of multiphase water-carbon dioxide mixture flows in porous media. Using the developed methodology the mixture phase diagram was calculated both below and above critical point of water. A zone of three-phase state conditions was detected where the mixture splits in three phases: liquid water and liquefied and gaseous carbon dioxide. The mixture flows subjected to formation of the three-phase flow region were investigated. The work is supported by Grant of the President of the Russian Federation (575.2010.1, 4810.2010.1).

Afanasyev, A.

2011-12-01

258

The effect of high pressure-high temperature processing conditions on acrylamide formation and other Maillard reaction compounds.  

Science.gov (United States)

The effect of high pressure-high temperature (HPHT) processing on the formation of acrylamide and other Maillard-type reaction compounds was investigated in order to elucidate the impact of HPHT conditions on the different stages of the Maillard reaction. This study was performed in equimolar asparagine-glucose model systems that were treated at various HP/HT conditions (100-115 °C, 400-700 MPa, 0-60 min), and, for comparison, the model system was also heat-treated at ambient pressure. On the treated samples, the concentration of acrylamide, reactants, hydroxymethylfurfural, organic acids, and melanoidins was determined and the pH prior to and after treatment was measured. Based on the measured responses, the retarding effect of high pressure on the overall Maillard reaction was demonstrated; no or little differences were observed between 400 and 700 MPa. The study was conducted in two types of buffer, i.e. phosphate and MES buffer. In case of acrylamide, aspartic acid and browning, a higher concentration was generated in the MES buffer system, but these differences with the phosphate buffer system could be ascribed to pH changes resulting from the application of combined high pressure and high temperature. Based on the results, acrylamide formation is not expected to pose a major hazard to HPHT-treated products. PMID:20973553

De Vleeschouwer, Kristel; Van der Plancken, Iesel; Van Loey, Ann; Hendrickx, Marc E

2010-11-24

259

A Computational Fluid Dynamics Study of Transitional Flows in Low-Pressure Turbines under a Wide Range of Operating Conditions  

Science.gov (United States)

A transport equation for the intermittency factor is employed to predict the transitional flows in low-pressure turbines. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, mu(sub p) with the intermittency factor, gamma. Turbulent quantities are predicted using Menter's two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model which can produce both the experimentally observed streamwise variation of intermittency and a realistic profile in the cross stream direction. The model had been previously validated against low-pressure turbine experiments with success. In this paper, the model is applied to predictions of three sets of recent low-pressure turbine experiments on the Pack B blade to further validate its predicting capabilities under various flow conditions. Comparisons of computational results with experimental data are provided. Overall, good agreement between the experimental data and computational results is obtained. The new model has been shown to have the capability of accurately predicting transitional flows under a wide range of low-pressure turbine conditions.

Suzen, Y. B.; Huang, P. G.; Ashpis, D. E.; Volino, R. J.; Corke, T. C.; Thomas, F. O.; Huang, J.; Lake, J. P.; King, P. I.

2007-01-01

260

Feasibility Study of PM Elimination by Silent Discharge Type of DPF under Room Temperature and Atmospheric Pressure Condition  

Science.gov (United States)

This Silent Discharge type of DPF (Diesel Particulate Filter) has been studied for eliminating PM (Particulate Mater) we call it “SDeDPF”. Usually, exhaust gas temperature of diesel engines is under 200 or 250°C at normal city driving condition. Under that condition, generally PM is not bourn out in the normal ceramic DPF. This SDeDPF aims to remove PM electrically and chemically even at room temperature and atmospheric pressure continuously. Finally, in the basic lab test result, 95.6% reduction of PM has been verified by SDeDPF with a special MFS (Metal Fiber Sheet) for discharge electrode to reduce a back pressure, a special Turbulent Block for turbulent and slower velocity of exhaust gas, the 1mm gap between electrodes and an optimum total area of piled electrodes. Also, 98.1% reduction of PM could be designed by most suitable gap between electrodes.

Chuubachi, Minoru; Nagasawa, Takeshi

 
 
 
 
261

Two-phase CFD analyses in fuel assembly sub-channels of Pressurized Water Reactors under swirl conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Single-phase CFD calculations are already widely applied in nuclear industry for the thermal-hydraulic design optimization of fuel assemblies (FA). In contrast, two-phase CFD-applications are still in the state of development. The work presented in this thesis shows contributions towards the detailed two-phase modeling of boiling flows under swirl conditions in sub-channel geometries of pressurized water reactors (PWR) FAs, including a realistic description of the critical heat flux (CHF)-phe...

Salnikova, Tatiana

2010-01-01

262

The application of the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract The study presents the possibility of applying the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions. A list of independent parameters on which the water temperature at the outlet of the heat exchanger depends was selected; and by means of the Buckingham theorem a functional relation between two dimensionless quantities, where there is no overall heat transfer coefficient, was obtained. The exact form of the function was determined on the...

2011-01-01

263

Abiogenic hydrocarbons produced under upper-mantle pressure-temperature conditions  

Science.gov (United States)

There are growing evidences for abiogenic pathways of the petroleum production in the deep Earth. The laboratory experiments under extreme pressures and temperatures provide direct information about the chemical reactivity and stability of the natural oil components. Here we present new results on formation of hydrocarbons at high pressures and temperatures generated in diamond anvil cells (DAC). We use in situ Raman spectroscopy in laser heated diamond anvil cells to monitor the chemical reactivity; Raman spectroscopy and synchrotron x-ray diffraction are used to determine the reaction products quenched to ambient temperature. We have explored chemical reactions in the system consisting of CaCO3-H2O with either of the following mantle minerals: San Carlos olivine, peridodite, and Rockport fayalite. We also studied chemical reactivity of methane and ethane to explore possible routes to generate heavier hydrocarbons. The pressure range of the experiments (3-6 GPa) are similar to those studied by Kenney et al. [1] and Scott et al. [2] but temperatures up to 2500 K were generated. At pressures in the 5-6 GPa range, methanogenesis was observed in the olivine-calcite-water, fayalite-calcite-water system at temperatures greater than 2300 K and less than 800 K, respectively. We find that methane at 2-5 GPa and 1000-1500 K partially reacts and forms saturated hydrocarbons (C2-C4alkanes), molecular hydrogen and graphite. Formation of methane in similar experiments on ethane suggests reversibility of hydrocarbon formation. These results support proposals of abiogenic pathways for the formation of hydrocarbons in the Earth's upper mantle. 1 Kenney, J. F., Kutcherov, V. G., Bendeliani, N. A. & Alekseev, V. A. The Evolution of Multicomponent Systems at High Pressures: VI. The Thermodynamic Stability of the Hydrogen-Carbon System: The Genesis of Hydrocarbons and the Origin of Petroleum. Proc. Natl. Acad. Sci. U.S.A. 99, 10976-10981 (2002). 2 Scott, H.P., Hemley, R.J., Mao, H-K., Herschbach, D.R., Fried, L.E., Howard, W.M., and Bastea, S. Generation of methane in the Earth's mantle: In situ high pressure-temperature measurements of carbonate reduction, Proc. Nat. Acad. Sci. 39, 14023-14026 (2004).

Goncharov, Alexander F.; Chellappa, Raja S.; Kolesnikov, Anton; Somayazulu, Maddury; Kutcherov, Vladimir G.; Hemley, Russell J.

2010-05-01

264

Space-dependent core/reflector boundary conditions generated by the boundary element method for pressurized water reactors  

International Nuclear Information System (INIS)

This paper reports on the boundary element method used to generate energy-dependent matrix-type boundary conditions along core/reflector interfaces and along baffle-plate surfaces of pressurized water reactors. This method enables one to deal with all types of boundary geometries including convex and concave corners. The method is applicable to neutron diffusion problems with more than two energy groups and also can be used to model a reflector with or without a baffle plate. Excellent eigenvalue and flux shape results can be obtained when the boundary conditions generated by this technique are coupled with core-only finite difference calculations

1991-01-01

265

Experimental measurements of leak rates and burst pressures for cracked Alloy 600 tubes under steam generator conditions  

International Nuclear Information System (INIS)

The objectives of this program are to measure leak rates in steam generator tubes under simulated typical operating and accident conditions and to measure burst pressures of defective tubes at operating temperatures. Concerns about the behavior of tubes with defects in operating steam generators prompted this study. Tubes in the field have developed intergranular stress corrosion cracks (both ID and OD initiated) in straight lengths, U-bend regions, and in tubesheet roll transition areas which have resulted in primary to secondary leakage and resulted in unscheduled outages. This report describes test conditions, material used, and test results

1987-06-01

266

Unsteady blade pressure measurements for the SR-7A propeller at cruise conditions  

Science.gov (United States)

The unsteady blade surface pressures were measured on the SR-7A propeller. The freestream Mach number, inflow angle, and advance ratio were varied while measurements were made at nine blade stations. At a freestream Mach number of 0.8, the data in terms of unsteady pressure coefficient versus azimuth angle are compared to an unsteady three-dimensional Euler solution, yielding very encouraging results. The code predicts the shape (phase) of the waveform very well, while the magnitude is over-predicted in many cases. At tunnel Mach numbers below 0.6, an unusually large response on the suction surface at 0.15 chord and 0.88 radius was observed. The behavior of this response suggests the presence of a leading-edge vortex.

Heidelberg, L. J.; Nallasamy, M.

1990-01-01

267

Reduced herbivore pressure under rainy ENSO conditions could facilitate dryland reforestation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Most semi-arid and arid regions around the world have lost a major part of their original vegetation. Restoration of once shrublands and woodlands is often challenged by low seedling establishment success due to water stress and herbivory. In some regions, increased rainfall during El Niño Southern Oscillation (ENSO) events can significantly stimulate plant recruitment. However, recruitment seems to be strongly modulated by herbivore pressure. Also, seedling establishment in arid ecosystems ...

Gutierrez, J. R.; Holmgren, M.; Manrique, R.; Squeo, F. A.

2007-01-01

268

Surface tension measurements of coal ash slags under reducing conditions at elevated pressures  

Energy Technology Data Exchange (ETDEWEB)

The aim of limiting the amount of CO{sub 2} that is released together with other exhaust gases from power plants can be reached by technologies allowing for a systematic separation of this greenhouse gas. One such technology is the integrated gasification combined cycle power plant which makes use of a coal gasification step. For the gasification involving temperatures far higher than in typical pulverised combustion chambers, ash contained in the fuel is liquefied (slag) and must be removed from the cycle to guarantee safe operation of downstream equipment. To keep the efficiency of the power plant as high as possible, hot gas cleaning facilities are most desirable for this purpose. The design of these installations necessitates knowledge about thermophysical properties of coal ash slags, especially in reducing, pressurised atmospheres. In this work, the surface tension of 15 coal ash slags was measured in argon hydrogen gas of up to 10 bar absolute pressure according to the sessile drop method. Compared to experiments at 1 bar, surface tension values up to 42% lower were found on applying pressure. Additionally, shifts in the melting temperature interval of the ashes due to increased pressure were observed. The surface tension values obtained in pressurised atmospheres ranged from 270 to 490 mN/m with respect to temperature intervals where almost no data scattering occured. 43 refs., 11 figs., 1 tab.

Tobias Melchior; Marc Blaesing; Guenther Puetz; Michael Mueller [Forschungszentrum Juelich GmbH, Juelich (Germany). Institute of Energy Research

2011-01-15

269

Two boil-off patterns in rod bundles under high-pressure conditions  

International Nuclear Information System (INIS)

It is believed that the nuclear core or steam generator tube bundle becomes partially uncovered due to transient boil-off during a small-break loss-of-coolant accident. In the boil-off, the water inventory in the nuclear core or the steam generator boiling section decreases due to the effluent steam or water. Existing studies have focused on the boil-off experiments in low bundle powers at system pressures from 0.7 to 7.5 MPa. The boil-off experiments in a wide range of bundle powers at system pressures from 3.1 to 11.9 MPa were conducted by using the Two-Phase Flow Test Facility (TPTF). The paper presents a schematic of boil-off patterns in the high or low bundle power considered in the present study. The high and low power boil-off patterns are observed in the TPTF high-pressure boil-off experiments. The difference between the two patterns is considered to be due to the slug-to-annular-flow transition as explained with the present transition model

1985-11-01

270

Evaluation of High-Pressure RCS Natural Circulations Under Severe Accident Conditions  

International Nuclear Information System (INIS)

Since TMI-2 accident, the occurrence of severe accident natural circulations inside RCS during entire in-vessel core melt progressions before the reactor vessel breach had been emphasized and tried to clarify its thermal-hydraulic characteristics. As one of consolidated outcomes of these efforts, sophisticated models have been presented to explain the effects of a variety of engineering and phenomenological factors involved during severe accident mitigation on the integrity of RCS pressure boundaries, i.e. reactor pressure vessel(RPV), RCS coolant pipe and steam generator tubes. In general, natural circulation occurs due to density differences, which for single phase flow, is typically generated by temperature differences. Three natural circulation flows can be formed during severe accidents: in-vessel, hot leg countercurrent flow and flow through the coolant loops. Each of these flows may be present during high-pressure transients such as station blackout (SBO) and total loss of feedwater (TLOFW). As a part of research works in order to contribute on the completeness of severe accident management guidance (SAMG) in domestic plants by quantitatively assessing the RCS natural circulations on its integrity, this study presents basic approach for this work and some preliminary results of these efforts with development of appropriately detailed RCS model using MELCOR computer code

2006-11-02

271

Boundary-Layer Separation Control under Low-Pressure Turbine Airfoil Conditions using Glow-Discharge Plasma Actuators  

Science.gov (United States)

Modem low-pressure turbines, in general, utilize highly loaded airfoils in an effort to improve efficiency and to lower the number of airfoils needed. Typically, the airfoil boundary layers are turbulent and fully attached at takeoff conditions, whereas a substantial fraction of the boundary layers on the airfoils may be transitional at cruise conditions due to the change of density with altitude. The strong adverse pressure gradients on the suction side of these airfoils can lead to boundary-layer separation at the latter low Reynolds number conditions. Large separation bubbles, particularly those which fail to reattach, cause a significant degradation of engine efficiency. A component efficiency drop of the order 2% may occur between takeoff and cruise conditions for large commercial transport engines and could be as large as 7% for smaller engines at higher altitude. An efficient means of of separation elimination/reduction is, therefore, crucial to improved turbine design. Because the large change in the Reynolds number from takeoff to cruise leads to a distinct change in the airfoil flow physics, a separation control strategy intended for cruise conditions will need to be carefully constructed so as to incur minimum impact/penalty at takeoff. A complicating factor, but also a potential advantage in the quest for an efficient strategy, is the intricate interplay between separation and transition for the situation at hand. Volino gives a comprehensive discussion of several recent studies on transition and separation under low-pressure-turbine conditions, among them one in the present facility. Transition may begin before or after separation, depending on the Reynolds number and other flow conditions. If the transition occurs early in the boundary layer then separation may be reduced or completely eliminated. Transition in the shear layer of a separation bubble can lead to rapid reattachment. This suggests using control mechanisms to trigger and enhance early transition. Gad-el-Hak provides a review of various techniques for flow control in general and Volino discusses recent studies on separation control under low-pressure-turbine conditions utilizing passive as well as active devices. As pointed out by Volino, passive devices optimized for separation control at low Reynolds numbers tend to increase losses at high Reynolds numbers, Active devices have the attractive feature that they can be utilized only in operational regimes where they are needed and when turned off would not affect the flow. The focus in the present paper is an experimental Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil ('Pak-B'). The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) Gee-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface- flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control. of active separation control using glow discharge plasma actuators.

Hultgren, Lennart S.; Ashpis, David E.

2003-01-01

272

The influence of meteorological conditions on the side effects of contrast media during infusion urograms  

International Nuclear Information System (INIS)

A relationship between certain weather conditions and the frequency of some diseases has been recognised for a long time. During a period of two and a quarter years, the course of infusion urograms in 6862 patients was carefully monitored. At the same time, records were kept of the weather, including the general weather situation, changes in the weather, its dynamics, atmospheric pressure and 'vorticity'. 7.96% of patients showed side effects from the contrast medium. 32.6% of all patients admitted to having been affected by the weather, with an incidence of side effects of 9.7%. Older patients and over-weight patients tended to suffer fewer side effects. There was no correlation with the seasons. As regards the general weather situation, there was an increased incidence associated with changes coming from the east, fewer incidents during the in-flow of cold air and high pressure situations. There were marked differences during periods of high and low pressure ('vorticity'). High pressure situations and periods of increasing barometric pressure had complication rates of 5.3% and 4.7% respectively, low pressure, 11%. Statistical analysis showed no significant difference between the groups, but tendencies were unmistakable. A large number of individual factors are known to have an effect, such as abnormalities of the complement system, antigen-antibody reactions and others, but the importance of each factor remains uncertain. The present results indicate that the reaction of a patient at the moment of the investigation also plays a significant part. (org.)

1981-01-01

273

Shear Veins Under High Pore Pressure Condition Along Subduction Interface: Yokonami Mélange, Cretaceous Shimanto Belt, Shikoku, Southwest Japan  

Science.gov (United States)

Fluid pressure along subdcution interface is a key parameter to understand the fault strength, wedge geometry and seismogenic behavior. In this study, we focused on shear veins pervasively observed in exhumed accretionary complex, Yokonami mélange, Cretaceous Shiamanto Belt, Southwest Japan to examine paleo-stress, effective friction coefficient, fluid pressure ratio and fluid pressure along subduction interface. Lithology of the Yokonami mélange is mainly sandstones surrounded by foliated black shales with minor components of basalts, cherts, tuffs, and limestones, representing tectonic mélange textures. Shear veins cutting mélange foliations are pervasively observed. Shear veins are composed of quartz and calcite. Slicken lines and slicken steps are always observed on the surfaces of shear veins. Pressure-temperature conditions for shear veins are about 180MPa and about 200 degree C on the basis of fluid inclusion analysis. Since the distribution of shear veins are related to packages of ocean floor stratigraphy, formation of shear vein can be before underplating and after mélange formation along subduction interface. We conducted multiple inversion method using slip data of shear veins to examine paleo-stress. In the result, we obtained maximum shear stress horizontal to foliations with 0.3 of stress ratio that is defined as (sigma2-sigma3)/(sigma1-sigma3). Effective friction coefficient was estimated as about 0.10-0.22 by the lowest value of ratio of normal and shear stresses in the normalized Mohr's circle on each plane of shear vein. If we put friction coefficient under dry condition as 0.7 because shear veins cut lithified mélange through out, fluid pressure ratio is equivalent to 0.68-0.86. This is very high fluid pressure ratio along subduction plate interface. On the basis of this fluid pressure ratio and P-T conditions of shear veins from fluid inclusion analysis, 7-12km of depth and 20-30 degree C of geothermal gradient were estimated. The age of subducting plate in the Yokonami mélange was about 50-60Ma from the difference of depositional ages between chert and black shale. The geothermal gradient estimated from the slab age is consistent with from fluid pressure ratio and fluid inclusion analysis. This suggests that the low effective frictional coefficient and high fluid pressure ratio estimated from geological evidences are reasonable values for the formation of shear veins. Kitajima and Saffer (2012) revealed that very low frequency earthquakes (VLFs) occur in the high pore pressure area. Saito et al. (2013) found the quartz cemented fault rocks represent velocity weakening behavior and suggested that the quartz-rich shear veins in shallow accretionary complex might be a geological evidence of VLFs. Our result in this study can support this idea as a shear veins with high fluid pressure at the time of their formation.

Hashimoto, Y.; Eida, M.

2013-12-01

274

Creep failure of a reactor pressure vessel lower head under severe accident conditions  

International Nuclear Information System (INIS)

A severe accident in a nuclear power plant could result in the relocation of large quantities of molten core material onto the lower head of he reactor pressure vessel (RPV). In the absence of inherent cooling mechanisms, failure of the RPV ultimately becomes possible under the combined effects of system pressure and the thermal heat-up of the lower head. Sandia National Laboratories has performed seven experiments at 1:5th scale simulating creep failure of a RPV lower head. This paper describes a modeling program that complements the experimental program. Analyses have been performed using the general-purpose finite-element code ABAQUS-5.6. In order to make ABAQUS solve the specific problem at hand, a material constitutive model that utilizes temperature dependent properties has been developed and attached to ABAQUS-executable through its UMAT utility. Analyses of the LHF-1 experiment predict instability-type failure. Predicted strains are delayed relative to the observed strain histories. Parametric variations on either the yield stress, creep rate, or both (within the range of material property data) can bring predictions into agreement with experiment. The analysis indicates that it is necessary to conduct material property tests on the actual material used in the experimental program. The constitutive model employed in the present analyses is the subject of a separate publication

1998-07-26

275

Post-dryout heat transfer and entrained droplet sizes at low pressure and low flow conditions  

International Nuclear Information System (INIS)

The entrainment mechanisms and the entrained droplet sizes with relation to the flow regimes are investigated. Through the analysis of many experimental post-dryout data, it is shown that the most probable flow regime near dryout or quench front is not annular flow but churn-turbulent flow when the mass flux is low. A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. The history-dependent post-dryout model of Varone and Rohsenow replaced by the Webb-Chen model for wall-vapor heat transfer is used as a reference model in the analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is not applicable when the vapor superficial velocity is very low. This is explained by the change of main entrainment mechanism with the change of flow regime. In bubbly or slug flow a number of tiny droplets generated from bubble burst become important in the heat transfer after dryout. Therefore, the suggested correlation is valid only in the churn-turbulent flow regime (jg* = 0.5?4.5). It is also suggested that the droplet size generated from the churn-turbulent surface is dependent not only on the pressure but also on the vapor velocity. It turns out that the present model can predict the measured cladding and vapor temperatures within 20% and 25%, respectively

1997-04-14

276

The launching condition of a jet driven by the magnetic field and radiation pressure of an accretion disc  

CERN Multimedia

We find that the cold gas can be magnetically launched from the disc surface with the help of the radiation pressure if the angular velocity of the radiation pressure dominated accretion disc is greater than a critical value, which decreases with increasing the disc thickness H/R (radiation pressure). This indicates the force exerted by the radiation from the disc indeed helps launching the outflow. The rotational velocity of the gas in the disc depends on the strength of the magnetic field threading the disc and the inclination B_z/B_r of the field line at the disc surface. The launching condition for the cold gas at the disc surface sets an upper limit on the magnetic field strength, which is a function of the field line inclination B_z/B_r and the disc thickness H/R. This implies a more strict constraint on the maximal jet power can be extracted from a radiation pressure dominated accretion disc than that derived conventionally on the equipartition assumption.

Cao, Xinwu

2012-01-01

277

The dynamic pressure measurements of the nuclear reactor coolant for condition-based maintenance of the reactor  

International Nuclear Information System (INIS)

The condition-based maintenance of the nuclear reactor, by monitoring and measuring the instantaneous dynamic pressure distribution of the coolant (water) impact on the solid surfaces of the reactor during operation is presented. The behaviour of water domes (jets) produced by underwater explosions of small changes of P.E.T.N. at various depths in two different size cylindrical containers, which simulate the nuclear reactor, is investigated. Water surface domes (jets) from the underwater explosions are photographed. Depending on the depth of the charge, curved and flat top jets of up to 455 mm diameter and impact speeds of up to 70 m/sec. are observed. The instabilities in the dome surfaces are observed and the instantaneous profiles are analysed. It is found that, in all cases tested, the maximum pressure takes place at the center of the jet and could reach up to 3.0 times the on-dimensional impact pressure value. The use of their measurements, as online monitoring for condition-based maintenance and design-out maintenance is discussed. 18 refs

1990-03-17

278

Electrical safety equipment for pressurized water reactor power stations: insulation losses under accident conditions  

International Nuclear Information System (INIS)

Thermodynamic conditions prevailing during the accidents examined often cause high insulation losses in K1 safety equipment located in the containment building. This article analyses the physical phenomena involved, gives examples of calculation of minimal insulation resistances which are necessary for the system operation and maximum insulation resistance required, indicates some rules for defining threshold values required in equipment qualification tests

1985-01-01

279

The application of the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract The study presents the possibility of applying the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions. A list of independent parameters on which the water temperature at the outlet of the heat exchanger depends was selected; and by means of the Buckingham theorem a functional relation between two dimensionless quantities, where there is no overall heat transfer coefficient, was obtained. The exact form of the function was determined on the basis of actual measurement data and a linear relation between two dimensionless quantities was obtained. The correctness of the proposed relation was examined for two high-pressure regenerative exchangers for a 200 MW power plant.

Rafal Marcin Laskowski

2011-01-01

280

Evaluation of hydraulic and mechanical properties of Berea sandstone under different conditions of temperature and confining pressure  

International Nuclear Information System (INIS)

The isotropic compression experiments using Berea sandstone were conducted under the different temperature and confining pressure conditions, and the evolutions of hydraulic and mechanical properties were observed. The temperatures and confining pressures prescribed for the experiments are 20 and 90degC, and 7.5 or 8.0 MPa, respectively. The observed permeability at 20degC did not significantly evolve during the experiment period, while that at 90degC decreased by roughly 20% relative to the original value. This reduction may be attributed to the change of pore-structure induced by mineral dissolution and/or precipitation. Unlikely, the uniaxial compression tests showed no obvious change observed between pre- and post-experimental results. The XRD observation also showed no significant difference of mineralogy between them. (author)

2011-01-01

 
 
 
 
281

Experimental investigation of supersonic low pressure air plasma flows obtained with different arc-jet operating conditions  

International Nuclear Information System (INIS)

A stationary arc-jet plasma flow at low pressure is used to simulate some properties of the gas flow surrounding a vehicle during its entry into celestial body's atmospheres. This paper presents an experimental study concerning plasmas simulating a re-entry into our planet. Optical measurements have been carried out for several operating plasma conditions in the free stream, and in the shock layer formed in front of a flat cylindrical plate, placed in the plasma jet. The analysis of the spectral radiation enabled the identification of the emitting species, the determination of the rotational and vibrational temperatures in the free-stream and in the shock layer and the determination of the distance of the shock to the flat plate face. Some plasma fluid parameters like, stagnation pressure, specific enthalpy and heat flux have been determined experimentally along the plasma-jet axis.

2012-11-27

282

Numerical study of the pressure drop in a plain fin-and-circular tube heat exchanger under frost condition  

International Nuclear Information System (INIS)

Full text: Three-dimensional computational fluid dynamics (CFD) simulations are carried out to study the pressure drop behavior in a plain fin-and-four staggered layout and circular tube rows for different fin pitches under frost conditions using FLUENT 6.3 CFD code. Models geometry is created and meshed using GAMBIT 2.3. Fluid flow and heat transfer are simulated and results calculated using (Transitional SST k-omega) turbulence model, with steady-state solver. Model validation is carried out by comparing the pressure drop of a simulated case with experimental results from the literature. It was found that Fluent 6.3 software has been sufficient for simulating the flow characteristics in tube-fin heat exchangers. (author)

2009-11-03

283

Interfacial effects of surface-active agents under zinc pressure leach conditions  

Science.gov (United States)

Liquid sulfur-zinc sulfate solution interfacial tensions and liquid sulfur-zinc sulfate solution-zinc sulfide (marmatite) contact angles were measured in the absence and presence of surface-active agents. Interfacial tensions measured varied between 54 ± 1 mN/m in the surfactant-free system and 20 ± 1 mN/m in the presence of a surfactant. The liquid sulfur-zinc sulfide mineral-zinc sulfate solution contact angle varies between 80 ± 5 deg, in the absence of any surfactant, and 148 ± 5 deg, depending on the surfactant used. The surface-active agents were used as dispersants for sulfur in bench-scale zinc pressure-leaching experiments. The observed extent of zinc extraction depends on the surfactant and varies from 40 to 96 pct.

Owusu, George; Dreisinger, David B.; Peters, Ernest

1995-02-01

284

Experimental study on DNB heat flux of plate-type fuel in pressurized condition  

International Nuclear Information System (INIS)

Experimental study was carried out in order to determine the DNB correlation for the safety analysis of the JMTR low enrichment fuel core. Since it is essential to examine applicability and safety margin of the correlation for the safety analysis, DNB heat fluxes were measured with the test section of rectangular flow channel simulating JMTR fuel element subchannel in the pressure range of 1 ? 13 kg/cm"2 abs and the velocity range of 0 ? 4.4 m/s. Reviewing existed DNB correlations based on the experimental data, Sudo correlations scheme was selected for the JMTR safety analysis with minor modification for the high flow rate region. Comparing the correlations scheme with experimental data, allowable limit of the minimum DNBR was determined to be 1.5. (author)

1992-01-01

285

Influence of dc Pulsed Atmospheric Pressure Plasma Jet Processing Conditions on Polymer Activation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Plasma treatments are widely used to activate polymer surfaces prior to adhesive bonding. This study investigates the influence of plasma treatment conditions on the surface activation of a range of polymers using the PlasmaTreat (Open Air) system. In this study the effect of dc pulse plasma cycle time, compressed air flow rate and the plasma jet nozzle to substrate distance on the plasma discharge was examined. The influence that the dc pulse plasma cycle time parameter has on the activation...

Dowling, Denis P.; O Neill, Feidhlim T.; Langlais, Simon J.; Law, Victor J.

2011-01-01

286

High Pressure Compression-Molding of ?-Cellulose and Effects of Operating Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Commercial ?-cellulose was compression-molded to produce 1A dog-bone specimens under various operating conditions without any additive. The resulting agromaterials exhibited a smooth, plastic-like surface, and constituted a suitable target as replacement for plastic materials. Tensile and three-points bending tests were conducted according to ISO standards related to the evaluation of plastic materials. The specimens had strengths comparable to classical petroleum-based thermoplastics. They ...

Thibaud Pintiaux; David Viet; Virginie Vandenbossche; Luc Rigal; Antoine Rouilly

2013-01-01

287

Working conditions under economic pressure: The case of the German cleaning industry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper investigates changes in collective bargaining policy in the German cleaning industry in recent years. It uses the Socio-economic Panel (GSOEP) to survey employees on employment conditions and expert interviews with key members of the industry to look at possible new paths of development in the industry as well as the range of attitudes of the players involved. The socio-demography of the employees in the industry was given close attention and, with regard to collective labour agree...

2005-01-01

288

Factors association and predisposing conditions in the event of pressure ulcers  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: to examine the association between predisposing conditions (CP, intrinsic (FI and extrinsic factors (EF with occurrence of PU in bedridden patients in the intensive care unit and wards of a university hospital. Metodology: it’s a descriptive and quantitative study, performed at a University Hospital from Natal/RN city, after approved by the Ethics Committee of Hospital Universitário Onofre Lopes (protocol number135/07 in which data were collected from December 2007 to February 2008, through a structured form, data from medical records and physical examination of the skin. The results were organized using SPSS 15.0 and analyzed using descriptive and inferential statistics. Results: of the 30 patients studied, were diagnosed in 19 UP 43.3% of them. Was found an association of 35.7% of the Predisposing conditions, Intrinsic factors and Extrinsic factors for all patients studied, statistically significant (p-value = 0001, between the average scores in patients with and without PU, with reason chance to 12.0 for the development of PU and there was moderate correlation (r=0618 in the presence of this association. Conclusion: results show the influence of the multiplicity of factors and conditions on the occurrence of PU, which brings us to reflect on the assistance focused on.

Thalyne Yuri de Araújo Farias

2010-01-01

289

Preparation and calibration of pressure-sensitive and temperature-sensitive paints for fluorescence lifetime imaging applications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis describes various methods for time-resolved luminescence lifetime determination, and their applications to imaging barometric pressure and temperature. These approaches are superior to luminescence intensity imaging in that they are less influenced by sources of errors like light scattering, inhomogeneous indicator distribution, photobleaching, or background fluorescence because they are intrinsically referenced. The data obtained are precise and unambiguous. Novel sensor material...

Stich, Matthias I. J.

2010-01-01

290

Advances in Thin Film Thermocouple Durability Under High Temperature and Pressure Testing Conditions  

Science.gov (United States)

Thin film thermocouples for measuring material surface temperature have been previously demonstrated on several material systems and in various hostile test environments. A well-developed thin film fabrication procedure utilizing shadow masking for patterning the sensors elements had produced thin films with sufficient durability for applications in high temperature and pressure environments that exist in air-breathing and hydrogen-fueled burner rig and engine test facilities. However, while shadow masking had been a reliable method for specimens with flat and gently curved surfaces, it had not been consistently reliable for use on test components with sharp contours. This work reports on the feasibility of utilizing photolithography processing for patterning thin film thermocouples. Because this patterning process required changes in the thin film deposition process from that developed for shadow masking, the effect of these changes on thin film adherence during burner rig testing was evaluated. In addition to the results of changing the patterning method, the effects on thin film adherence of other processes used in the thin film fabrication procedure is also presented.

Martin, Lisa C.; Fralick, Gustave C.; Taylor, Keith F.

1999-01-01

291

Farmers Under Pressure : Analysis of the Social Conditions of Cases of Animal Neglect  

DEFF Research Database (Denmark)

In this paper we analyse how risk factors in highly industrialised agriculture are connected to animal neglect. With Danish agriculture as a case study, we use two types of data. First, we use register data from Statistics Denmark to map how risk factors such as farmersâ?? financial and social troubles are connected to convictions of neglect. Second, we analyse narratives where interviewed farmers, involved in cases of neglect, describe how they themselves experienced the incidents. We find that while livestock farmers in general have a low risk of animal neglect problems, a small percentage of them face severe financial difficulties, divorce and psychiatric problems, which are connected to an increased risk of being convicted for the neglect of farm animals. The narratives bring forward themes of pressure related to financial trouble, technological break down, family problems, stress and a growing concern among the farmers towards the governmental control in farm animal production. We discuss how these factorscan be used to identify and help farmers with a high risk of being convicted of livestock neglect.

Andrade, Stefan Bastholm; Anneberg, Inger

2014-01-01

292

Stability and Compressibility of RbAlSi3O8 at High Pressure Conditions  

Science.gov (United States)

Potassium and Rubidium are minor and trace elements of the Earth's mantle, both of which have long-lived radioactive isotopes. The decay of 87Rb to 87Sr in particular serves as a geochemical tracer for long-lived mantle processes. While Rb in the crust is stored as a feldspar (RbAlSi3O8), the most abundant mineral of the Earth's crust, the mineral host of Rb in the mantle is uncertain. Here we report the phase stability and compressibility of RbAlSi3O8, rubicline, from laser-heated diamond anvil cell (LHDAC) experiments with synchrotron-based x-ray diffraction. The high-pressure phase diagram of rubicline is similar to that of microcline, transforming to the hollandite structure at ˜15 GPa, then to the hollandite II structure at ˜25 GPa, suggesting that the host mineral for K and Rb in the mantle are identical. Preliminary results yield the bulk modulus of Rubidium hollandite-I to be 210 (± 10) GPa, assuming a K'=4.

Hyung, E.; Whitaker, S.; Hovis, G.; Panero, W. R.

2009-05-01

293

The influence of testing conditions on burst pressure assessment for inconel tubing  

International Nuclear Information System (INIS)

Because at the lack of normalization for burst testing of tubes with TWD flaws, large divergences are observed between laboratory results. This could result in either unsafe or unduly penalizing consequences. Testing flawed tubes under representative conditions (high leak rate without any sealing provision) yielded results matching previous laboratory data that were obtained with a locally reinforced bladder. This should not be construed to validate any similar laboratory technique, as the particular combination of materials (plastic and metal) strength and thickness, together with other testing details (such as load rate) may affect the results. (author)

1991-01-01

294

A reactor water level and pressure prediction method under small loss-of-coolant-accident conditions in boiling water reactors  

International Nuclear Information System (INIS)

An on-line method of predicting reactor water level and pressure under small loss-of-coolant-accident (LOCA) conditions has been proposed. The method features initialization of a simplified reactor model in transient conditions. This is done by using plant data in time series and estimating unknown parameters, such as break area, by a nonlinear optimization method. Off-line simulations were performed for small LOCAs (break area: about100 cm2) using the results of a reference LOCA analysis code for plant data. These showed that the difference from the reference calculation during a 10-min period was within 10%, normalized by the value at the initialization time, and the estimation error for break area was below 11%. The overall CPU time required for the prediction was below 10 s in a general purpose computer of 10 million instructions per second

1985-01-01

295

Simulation and analysis of bearing pad to pressure tube contact heat transfer under large break LOCA conditions  

International Nuclear Information System (INIS)

In some postulated loss-of-coolant accidents (LOCAs) in a CANDU reactor, localized 'hot spots' can develop on the pressure tube as a result of decay heat dissipation by conduction through bearing pad/pressure tube contact locations. Depending on the severity of flow degradation in the channel, these 'hot spots' could represent a potential threat to fuel channel integrity. The most important parameter in the simulation of BP/PT contact is the contact conductance. Since BP/PT thermal contact conductance is a complex parameter which depends upon the thermal and physical characteristics of the material junction and the surrounding environment, contact conductance is determined from experiments relevant to the reactor conditions. A series of twelve full scale integrated BP/PT contact experiments have been conducted at AECL-WRL under CANDU Owner Group (COG). The objective of the experiments was to investigate the effect of BP/PT contact on PT thermal-mechanical behaviour. This paper presents the simulation of BP/PT interaction integrated experiments using SMARTT and MINI-SMARTT computer codes and subsequent derivation of the BP/PT contact conductance by best fitting of the experimental pressure tube temperature measurements. (author)

1996-06-09

296

Experimental study on the transfer while helium turbulent convection at supercritical pressure in conditions of strong nonisothermality  

International Nuclear Information System (INIS)

Experimental study of heat transfer to helium of supercritical pressure in the range of quasi-stabilized heat transfer and in the initial part of a heated tube is carried out. The experiments are conducted in the range of regime parameters: pressure P=(0.24-0.68)x106 Pa (P/Psub(cr)=1.05-3.1); flow rate (0.037-0.2)x10sup(-3) kg/s (Re9x103-6.5x104); heat flux density 900-6000 W/m2; Tsub(in)4.41-7.1 K. Experimental model presents a horizontally placed stainless steel of inner diameter d=1.4 mm, heated part length 545 mm. The temperature of the wall was controlled at the distances x/d=(11-239) from the heated part end. The dependence of heat transfer intensity on the input temperature, pressure, distance from the input and heat flux density during liquid heating is studied. A formula, taking into account the peculiriarities of heat exchange variation in the range of pseudocritical temperatures in the flow under conditions of a strong nonisothermicity and effect of the initial section, is suggested

1986-01-01

297

Influence of the external conditions on salt retention and pressure-induced electrical potential measured across a composite membrane  

DEFF Research Database (Denmark)

Transport on single electrolyte solutions (NaCl and MgCl2) due to pressure gradients across a commercial reverse osmosis membrane was studied by measuring volume flux (J(v)), salt rejection (S) and pressure induced electrical potential (Delta E) in a crossflow cell. The influence on these parameters of different external conditions due to hydrodynamic or chemical changes in the feed solutions was also studied. Changes were carried out by variation of the feed solution velocity (Reynolds numbers between 1500 and 3300) or the concentration ratio of mixed electrolytes (r = HCl/NaCl and HCl/MgCl2, r = 1, 0.5 and 0.1), respectively. Results show that J(v), S and Delta E values slightly increase when the velocity of the feed solution increases, but the mixed electrolytes strongly affect both salt rejection and pressure-induced electrical potential. A change in the sign of both parameters with respect to the value determined with single electrolytes at the same concentration was obtained, which is attributed to a strong coupling among the fluxes of individual ions and their distribution in the membrane when transport of mixed salt is studied. (C) 1999 Elsevier Science B.V. All rights reserved.

Benavente, Juana; Jonsson, Gunnar Eigil

1999-01-01

298

Effect of feedwater conditioning on corrosion behaviour of steam generator pipework materials in pressurized water reactors  

International Nuclear Information System (INIS)

The effect of the phosphate process and the low all volatile treatment procedure on the corrosion resistance of heating tubes of U tube-banked steam boilers is discussed. In individual cases the redox potential of the medium which results from the interaction of various oxidation and reduction agents present in the high temperature water and the self-regulating corrosion potential of the pipework cannot be determined by investigatory methods based on water analyses. In order to establish this type of potential independent of the procedure, the incorporation of potential probes in the components of interest is recommended. In this way any increased danger of corrosion of pipework due to oxidizing water conditions in the steam generator can be detected at an early state. The procedure is described. (orig.)

1986-10-01

299

Phenomenology during the loss of residual heat removal system at midloop conditions with pressurizer PORVs open: Associated boron dilution  

Energy Technology Data Exchange (ETDEWEB)

The loss of residual heat removal system (RHRS) at midloop operation is an important risk contributor at low power and shutdown conditions. In this kind of transient the reflux-condensation can play an important role during the sequence to avoid the core damage. Several simulations concerning the loss of the RHRS in a PWR-W with the pressurizer PORVs open have been carried out with TRACE code considering the availability of steam generators. The present study aims to analyze, firstly, the thermal-hydraulic behavior after the loss of RHRS at midloop conditions throughout different configurations with reflux-condensation as the sole cooling mechanism available, and secondly, the issue related to the boron dilution that takes place during this kind of transient. The simulation results show that in the open RCS configuration, an equilibrium pressure is obtained in all cases and the reflux-condensation removes an important part of the decay heat. Moreover, in some configurations, this mechanism may cause the formation of an unborated water slug in the crossover leg that can lead to a boron dilution sequence.

Gonzalez, Isaac [Energy Systems Department, Universidad Politecnica de Madrid, Rios Rosas, 21, 28003 Madrid (Spain)]. E-mail: igs@dse.upm.es; Queral, Cesar [Energy Systems Department, Universidad Politecnica de Madrid, Rios Rosas, 21, 28003 Madrid (Spain)]. E-mail: cesar@dse.upm.es; Exposito, Antonio [Energy Systems Department, Universidad Politecnica de Madrid, Rios Rosas, 21, 28003 Madrid (Spain)]. E-mail: ael@dse.upm.es

2007-03-15

300

Geochemistry of ultrahigh-pressure anatexis: fractionation of elements in the Kokchetav gneisses during melting at diamond-facies conditions  

Science.gov (United States)

The Kokchetav complex in Kazakhstan contains garnet-bearing gneisses that formed by partial melting of metasedimentary rocks at ultrahigh-pressure (UHP) conditions. Partial melting and melt extraction from these rocks is documented by a decrease in K2O and an increase in FeO + MgO in the restites. The most characteristic trace element feature of the Kokchetav UHP restites is a strong depletion in light rare earth elements (LREE), Th and U. This is attributed to complete dissolution of monazite/allanite in the melt and variable degree of melt extraction. In contrast, Zr concentrations remain approximately constant in all gneisses. Using experimentally determined solubilities of LREE and Zr in high-pressure melts, these data constrain the temperature of melting to ~1,000 °C. Large ion lithophile elements (LILE) are only moderately depleted in the samples that have the lowest U, Th and LREE contents, indicating that phengite retains some LILE in the residue. Some restites display an increase in Nb/Ta with respect to the protolith. This further suggests the presence of phengite, which, in contrast to rutile, preferentially incorporates Nb over Ta. The trace element fractionation observed during UHP anatexis in the Kokchetav gneisses is significantly different from depletions reported in low-pressure restites, where generally no LREE and Th depletion occurs. Melting at UHP conditions resulted in an increase in the Sm/Nd ratio and a decoupling of the Sm-Nd and Lu-Hf systems in the restite. Further subduction of such restites and mixing with mantle rocks might thus lead to a distinct isotopic reservoir different from the bulk continental crust.

Stepanov, Aleksandr S.; Hermann, Joerg; Korsakov, Andrey V.; Rubatto, Daniela

2014-05-01

 
 
 
 
301

Detectability and significance of the 12h barometric tide in the radon-222 signal, dripwater flow rate, carbon dioxide concentration and air temperature of an underground laboratory.  

Science.gov (United States)

Radon concentration has been measured since 1995 in the Roselend dead-end tunnel, in the French Alps, together with other geophysical and geochemical parameters. Bursts of radon concentration, reaching 65,600 Bq m-3 and up to several weeks duration, are observed over a background level of ca. 800 Bq m-3. These bursts appear to be related to the bedrock deformation or to the hydrogeological processes associated with the yearly cycle of water level in the nearby artificial Roselend Lake. In order to work out a generation mechanism, for these bursts, we developed tools to characterize the transport properties in the host rocks. Here, we concentrate on the 12h (S2) barometric tide. We first show, using real radon time series integrating synthetic signals, that a modified spectrogram method is more efficient than simple FFT to evidence weak periodic signals in such a context. Then, we apply this method to the radon concentration in the tunnel atmosphere measured by two different sensors: the AlphaGUARDTM sensor based on volumetric detection in an ionizing chamber, and the BarasolTM sensor, based on surface detection. Using the time series recorded by the AlphaGUARDTM, the S2 line, difficult to see with a simple FFT method, emerges clearly with our spectrogram method. This S2 line is not seen using the BarasolTM time series, illustrating the superior sensitivity of the AlphaGUARDTM for this particular purpose. Using a regular spectrogram analysis, we further show that the amplitude of the S2 line in the AlphaGUARDTM data depends on time, and appears particularly strong during the radon bursts. The presence of the S2 line reveals a high sensitivity of radon exhalation flux from the tunnel wall to changes of atmospheric pressure, and thus supports the advective transport mechanism for the radon bursts. A small but clear S2 component is also evidenced using our spectrogram method in a dripwater flow rate time series, representing a flow averaged over a 6 m2 area of the tunnel ceiling, while it is not observed in the flow rate of a more localized dripping. This suggests that some water drippings can also be affected by atmospheric pressure variations. The temporal structures of the S2 component in the flow rate and in the radon concentration, however, are not similar, indicating that water dripping from the ceiling cannot be the dominant source mechanism for the radon bursts. No S2 component is observed in the time series of carbon dioxide, but an interesting pattern is revealed by the S2 component of a temperature profile in the atmosphere. This study illustrates how a refined analysis to extract the S2 component in various geophysical time series can provide interesting clues on the complex processes affecting transport of fluids in unsaturated fractured media under multiple influences.

Richon, P.; Perrier, F.; Pili, E.; Boudon, G.; Villemant, B.; Sabroux, J.

2007-12-01

302

Experimental device to investigate crack propagation in pressure vessel steel under BWR conditions  

International Nuclear Information System (INIS)

An experimental device is developed to investigate the crack growth behaviour of RPV steel specimens under service conditions. It will be installed in the experimental power station VAK-Kahl (BWR, 16 MWe). The in pile part is composed of a stable frame with a hydraulically actuated load mechanism, the specimen chain and a measuring instrumentation. The specimen chain, fastened between load mechanism and a lower fixing point at the frame, is made up of five compact tensile specimens (CT40) and the associated connecting links. Specimen strain, crack opening and temperature are measured; for neutron dose monitoring activation wires are disposed. Out of pile, in the reactor hall, the hydraulic loading system is installed. The loading force is generated by a 100 kN-material testing machine; it moves a piston in the control cylinder, which is connected to the loading bellows of the in pile section. The measuring and control equipment and a desk computer serving for data preparation and reduction is placed in the reactor control room. (orig.)

1983-01-01

303

Ethanol preference, metabolism, blood pressure, and conditioned taste aversion in experimental cholestasis.  

Science.gov (United States)

The effect of a ligation of the common bile duct (BDL) on the chronic free-selection intake of ethanol was investigated. Rats were given a choice between water and a solution of either 6% (v/v) ethanol, 0.06% (w/v) sodium saccharin, or a mixture of both ethanol and saccharin. In different experiments, solutions were first presented either 3 weeks before surgery, about the time of surgery, or 2 weeks after surgery. Reductions in ethanol or saccharin intake were observed in BDL rats whenever the solutions were first presented either 3 weeks before or shortly after the surgery. No differences attributable to BDL were seen when ethanol solutions were first presented 2 weeks after surgery. The contingent nature of the effect suggests that the reduction results from a conditioned taste aversion rather than from differences in ethanol metabolism, sensitivity, or neurohormones such as angiotensin. The findings urge caution in the monitoring of the dietary habits of patients with a rapidly developing biliary obstruction. PMID:9259003

Lane, J R; Starbuck, E M; Fitts, D A

1997-08-01

304

The Formation of Oxide Films Under Pressurized Water Reactor Primary Coolant Conditions  

International Nuclear Information System (INIS)

The study investigated the effects of steam generator (SG) alloy composition and post-processing (e.g. heat treatment), and coolant boron concentration and zinc addition, on oxide film formation under PWR primary coolant conditions. Specimens of Alloy 600, Alloy 690, Alloy 800, type 304 stainless steel (SS304) and zircaloy-4 - the major materials of construction of primary circuits - were exposed to high-temperature coolant of different chemistries in autoclaves. In experiments with heat flux, surface-area ratios of specimens involved just the heated or cooled portions of zircaloy or SG alloy while the SS was isothermal; ratios were typical of actual reactor systems. In isothermal experiments, the ratios involved all wetted surfaces. After exposures of several days, specimens were removed and the oxides characterized with surface analysis techniques. As expected, the results revealed that Ni-based alloys and SS304 were both covered with iron rich crystallites overlaying an amorphous chromium rich layer, while zircaloy-4 was covered with a single oxide layer. For the SG tubing of the same post-processing, the higher chromium alloys apparently produced a more compact oxide than the lower chromium alloys. This effect of post-processing was observed on all alloys, but was not as obvious as the effect of alloy composition. The most compact oxides were formed in coolant containing boron, which tended to concentrate in the inner oxide layers. Thicker and looser outer layer oxides were found on Alloy 600 exposed for 30 days to coolant with pH300oC of 7.4 than on the same alloy for five or ten days to coolant with pH300oC of 7.1. Zinc in the coolant was incorporated in the inner oxide layer on SG material but had different effects on the outer layers on different materials. Observed differences in oxide morphologies may account for differences in crud behaviour in operating plants. (author)

2013-03-01

305

A standalone decay heat removal device for the Gas-cooled Fast Reactor for intermediate to atmospheric pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer An analytical model predicting Brayton cycle off-design steady states, is developed. Black-Right-Pointing-Pointer The model is used to design an autonomous decay heat removal system for the GFR. Black-Right-Pointing-Pointer Predictions of the analytical model are verified using CATHARE. Black-Right-Pointing-Pointer CATHARE code is used to simulate a set of GFR safety depressurization transients using this device. Black-Right-Pointing-Pointer Convenient turbo-machine designs exist for the targeted autonomous decay heat removal for a wide pressure range. - Abstract: This paper reports a design study for a Brayton cycle machine, which would constitute a dedicated, standalone decay heat removal (DHR) device for the Generation IV Gas-cooled Fast Reactor (GFR). In comparison to the DHR reference strategy developed by the French Commissariat a l'Energie Atomique during the GFR pre-conceptual design phase (which was completed at the end of 2007), the salient feature of this alternative device would be to combine the energetic autonomy of the natural convection process - which is foreseen for operation at high and medium pressures - with the efficiency of the forced convection process which is foreseen for operation down to very low pressures. An analytical model, the so-called 'Brayton scoping model', is described first. This is based on simplified thermodynamic and aerodynamic equations, and was developed to highlight design choices. Two different machine designs are analyzed: a Brayton loop turbo-machine working with helium, and a second one working with nitrogen, since nitrogen is the heavy gas foreseen to be injected into the primary system to enhance the natural convection under loss-of-coolant-accident (LOCA) conditions. Simulations of the steady-state and transient behavior of the proposed device have then been carried out using the CATHARE code. These serve to confirm the insights obtained from usage of the 'Brayton scoping' model, e.g., that the turbo-machine conveniently accelerates during the depressurization process to tend towards a steady rotational speed value, the speed rise being inversely proportional to the experienced pressure drop. Finally, CATHARE simulations are presented for complete DHR scenarios for the GFR, involving loss-of-coolant-accidents (LOCAs) in conjunction with loss of back-up-pressure (LOBP). Thereby, it is shown that, in each of the investigated cases, incorporation of the Brayton loop turbo-machine with nitrogen indeed leads to fuel temperatures remaining considerably below Category 4 accident limits.

Epiney, A., E-mail: aaron@epiney.ch [Paul Scherrer Institute PSI, Villigen (Switzerland); Ecole Polytechnique Federale EPFL, Lausanne (Switzerland); Alpy, N., E-mail: nicolas.alpy@cea.fr [CEA, DEN, Service d' Etudes des Systemes Innovants, F-13108 Saint Paul Lez Durance (France); Mikityuk, K., E-mail: konstantin.mikityuk@psi.ch [Paul Scherrer Institute PSI, Villigen (Switzerland); Chawla, R., E-mail: rakesh.chawla@psi.ch [Paul Scherrer Institute PSI, Villigen (Switzerland); Ecole Polytechnique Federale EPFL, Lausanne (Switzerland)

2012-01-15

306

Pulsatile ex vivo perfusion of human saphenous vein grafts under controlled pressure conditions increases MMP-2 expression  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The use of human saphenous vein grafts (HSVGs as a bypass conduit is a standard procedure in the treatment of coronary artery disease while their early occlusion remains a major problem. Methods We have developed an ex vivo perfusion system, which uses standardized and strictly controlled hemodynamic parameters for the pulsatile and non-static perfusion of HSVGs to guarantee a reliable analysis of molecular parameters under different pressure conditions. Cell viability of HSVGs (n = 12 was determined by the metabolic conversion of 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyl-tetrazolium bromide (MTT into a purple formazan dye. Results Under physiological flow rates (10 mmHg HSVGs remained viable for two weeks. Their exposure to arterial conditions (100 mmHg was possible for one week without important reduction in viability. Baseline expression of matrix metalloproteinase-2 (MMP-2 after venous perfusion (2.2 ± 0.5, n = 5 was strongly up-regulated after exposure to arterial conditions for three days (19.8 ± 4.3 or five days (23.9 ± 6.1, p Conclusion Therefore, our system might be helpful to more precisely understand the molecular mechanisms leading to an early failure of HSVGs.

Lange Rüdiger

2011-07-01

307

High-pressure X-ray photoelectron spectroscopy applied to vanadium phosphorus oxide catalysts under reaction conditions  

International Nuclear Information System (INIS)

This thesis is devoted to improvement of the high-pressure X-ray photoelectron spectroscopy (XPS) technique and to investigation by means of this technique of the industrially important vanadium phosphorus oxide (VPO) catalyst for oxidation of n-butane to maleic anhydride (MA). The design of a new instrument for high-pressure XPS is presented. Introduction into the design of a differential pumping system, combined with electrostatic lenses for collection of photoelectrons, makes possible the recording of XPS spectra of a gas or solid sample in a gas atmosphere at a pressure in the sample cell of up to 5 mbar. Calculation of the dimensions of the differential pumping system was performed using the molecular and viscous gas flow models. The electrostatic lenses were designed by numerical modeling. Details of the calculations are reported. High-pressure XPS on VPO catalysts was performed under reaction conditions with simultaneous monitoring of the catalytic activity by mass-spectrometry (i.e. in situ). Two differently prepared VPO samples were investigated in the reaction gas mixture at a pressure of 2 mbar at various temperatures. Both samples produced MA at the reaction temperature (400 C) and had during the experiment a similar catalytic activity towards MA normalized to the surface area. XPS spectra with the photon energies corresponding to the information depths of 1.0 and 1.8 nm were recorded. One sample showed no changes in the vanadium oxidation state with conditions and had a homogeneous distribution of oxidation state with depth. Another sample showed dramatic changes in the oxidation state. This sample was inhomogeneous both at low temperature and at 400 C. The oxidation state of the surface was determined to be of the same value (4.0±0.1) for both samples at the reaction temperature (400 C). The thickness of the topmost layer, in which changes in the oxidation state for the inhomogeneous sample occurred, was determined to be (3.5±2.0) nm. Similar catalytic properties of the samples together with the same oxidation state of the surface lead one to the conclusion that this value is the upper estimation of the thickness of the catalytically active layer and the structure of the catalytically active layer does not necessarily match the structure of the bulk. Additionally, experiments in n-butane/He gas mixture at the pressure of 1.6 mbar and a temperature of 400 C were performed. The homogeneous sample showed slower changes in the vanadium oxidation state of the surface during stay in the gas mixture compared with the inhomogeneous sample. This correlates with a slower drop in MA yield for the homogeneous sample. A P/V atomic ratio for the homogeneous sample was determined using some reference compounds. The ratio had not changed during the experiments greater than the experimental error. The results prove in situ XPS to be a suitable and useful technique for investigation of a real catalyst

2005-01-01

308

Potential application of a flash-type barometric desalination plant powered by waste heat from electric-power stations in Cyprus  

International Nuclear Information System (INIS)

This paper describes and evaluates the results of a study into the problems of freshwater production and shortages on the island of Cyprus. The use of a novel barometric flash-type desalinator, driven by otherwise waste-heat from the island's power-stations, is proposed as a means of increasing freshwater supplies. Mathematical models are described and used to investigate the thermodynamic performance and economic viability of the proposed system. Although water and electricity supply data for the island of Cyprus were used for the purposes of this investigation, the overall findings are thought have a wider applicability

2006-10-01

309

Potential application of a flash-type barometric desalination plant powered by waste heat from electric-power stations in Cyprus  

Energy Technology Data Exchange (ETDEWEB)

This paper describes and evaluates the results of a study into the problems of freshwater production and shortages on the island of Cyprus. The use of a novel barometric flash-type desalinator, driven by otherwise waste-heat from the island's power-stations, is proposed as a means of increasing freshwater supplies. Mathematical models are described and used to investigate the thermodynamic performance and economic viability of the proposed system. Although water and electricity supply data for the island of Cyprus were used for the purposes of this investigation, the overall findings are thought have a wider applicability. (author)

Maidment, G.G.; Eames, I.W.; Psaltas, M.; Lalzad, A. [Department of Engineering Systems, Faculty of Engineering, Science and the Built Environment, London South Bank University, 103 Borough Road, London SE1 0AA (United Kingdom)

2006-10-15

310

Multiwell CO2 injectivity: impact of boundary conditions and brine extraction on geologic CO2 storage efficiency and pressure buildup.  

Science.gov (United States)

CO2 storage efficiency is a metric that expresses the portion of the pore space of a subsurface geologic formation that is available to store CO2. Estimates of storage efficiency for large-scale geologic CO2 storage depend on a variety of factors including geologic properties and operational design. These factors govern estimates on CO2 storage resources, the longevity of storage sites, and potential pressure buildup in storage reservoirs. This study employs numerical modeling to quantify CO2 injection well numbers, well spacing, and storage efficiency as a function of geologic formation properties, open-versus-closed boundary conditions, and injection with or without brine extraction. The set of modeling runs is important as it allows the comparison of controlling factors on CO2 storage efficiency. Brine extraction in closed domains can result in storage efficiencies that are similar to those of injection in open-boundary domains. Geomechanical constraints on downhole pressure at both injection and extraction wells lower CO2 storage efficiency as compared to the idealized scenario in which the same volumes of CO2 and brine are injected and extracted, respectively. Geomechanical constraints should be taken into account to avoid potential damage to the storage site. PMID:23971876

Heath, Jason E; McKenna, Sean A; Dewers, Thomas A; Roach, Jesse D; Kobos, Peter H

2014-01-21

311

Low-temperature rupture behavior of Zircaloy-clad pressurized water reactor spent fuel rods under dry storage conditions  

International Nuclear Information System (INIS)

Creep rupture studies on five well-characterized Zircaloy-clad pressurized water reactor spent fuel rods, which were pressurized to a hoop stress of about145 MPa, were conducted for up to 2101 h at 3230C. The conditions were chosen for limited annealing of in-reactor irradiation hardening. No cladding breaches occurred, although significant hydride agglomeration and reorientation took place in rods that cooled under stress. Observations are interpreted in terms of a conservatively modified Larson-Miller curve to provide a lower bound on permissible maximum dry-storage temperatures, assuming creep rupture as the life-limiting mechanism. If hydride reorientation can be ruled out during dry storage, 3050C is a conservative lower bound, based on the creep-rupture mechanism, for the maximum storage temperature of rods with irradiation-hardened cladding to ensure a 100-yr cladding lifetime in an inert atmosphere. An oxidizing atmosphere reduced the lower bound on the maximum permissible storage temperature by about50C. While this lower bound is based on whole-rod data, other types of data on spent fuel behavior in dry storage might support a higher limit. This isothermal temperature limit does not take credit for the decreasing rod temperature during dry storage. High-temperature tests based on creep rupture as the limiting mechanism indicate that storage at temperatures between 400 and 4400C may be feasible for rods that are annealed

1984-01-01

312

Low-temperature rupture behavior of Zircaloy clad pressurized water reactor spent fuel rods under dry storage conditions  

International Nuclear Information System (INIS)

Creep rupture studies on five well-characterized Zircaloy clad pressurized water reactor spent fuel rods, which were pressurized to a hoop stress of approximately 145 MPa, were conducted for up to 2101 h at 3230C. The conditions were chosen for limited annealing of in-reactor irradiation-hardening. No cladding breaches occurred, although significant hydride agglomeration and reorientation took place in rods that cooled under stress. Observations are interpreted in terms of a conservatively modified Larson-Miller curve to provide a lower bound on permissible maximum dry-storage temperatures, assuming creep rupture as the life-limiting mechanism. If hydride reorientation can be ruled out during dry storage, 3050C is a conservative lower bound, based on the creep rupture mechanism, for the maximum storage temperature of rods with irradiation hardened cladding to ensure a 100-year cladding lifetime in an inert atmosphere. An oxidizing atmosphere reduces the lower bound on the maximum permissible storage temperature by approx. 50C. While high-temperature tests based on creep rupture as the limiting mechanism indicate that storage at temperatures between 4000C and 4400C may be feasible for rods which are annealed, tests to study rod performance in the 3050 to 4000C temperature range have not been conducted. 37 references, 10 figures, 7 tables

1983-01-01

313

Investigations of Response Time Parameters of a Pneumatic 3/2 Direct Acting Solenoid Valve Under Various Working Pressure Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available In pneumatic circuits, a solenoid valve is a key component for controlling and directing pneumatic energy. The solenoid valve functional performances are defined as response time parameters with respect to its actuations in terms of direction changing time. This paper aims to present response time parameters of solenoid valves under various working pressures. An experimental setup is employed in order to measure response time with reference to the input signals. The response time plays significant role for evaluating the valve performance in sensitive applications. The response time parameters includes the on delay, the off delay, the on time, the off time, the cycle time and the switching frequency. In this experimental investigation the influence of various input pressure conditions is recorded and tabulated. Valves with varying orifice diameter are employed and the investigation reveals the influence of orifice diameter in response time variations. The newly-proposed six response time parameters can be used to rate and select the appropriate valve for various industrial applications.

K. A. Venkataraman

2013-08-01

314

Effects of a carbon convection field on large diamond growth under high-pressure high-temperature conditions  

International Nuclear Information System (INIS)

Large diamond crystals were successfully synthesized by a FeNi—C system using the temperature gradient method under high-pressure high-temperature conditions. The assembly of the growth cell was improved and the growth process of diamond was investigated. Effects of the symmetry of the carbon convection field around the growing diamond crystal were investigated systematically by adjusting the position of the seed crystal in the melted catalyst/solvent. The results indicate that the morphologies and metal inclusion distributions of the synthetic diamond crystals vary obviously in both symmetric and non-symmetric carbon convection fields with temperature. Moreover, the finite element method was applied to analyze the carbon convection mode of the melted catalyst/solvent around the diamond crystal. This work is helpful for understanding the growth mechanism of diamond

2012-09-01

315

Influence of the cathode surface conditions on V–A characteristics in low-pressure nitrogen discharge  

Science.gov (United States)

In this paper we demonstrate and analyse the influence of cathode surface inhomogeneities on the breakdown, volt–ampere (V–A) characteristics and the spatial structure of the low-pressure non-equilibrium discharges. The idea for this work came from the need to explain the non-typical V–A characteristics (positive slope of the characteristics in low-current regime of the discharge) that we observed in a parallel-plate, dc discharge in nitrogen. It was found that the cathode was locally conditioned by the discharge that operated in the constricted glow regime. Spatial inhomogeneity of the cathode surface strongly affected the subsequent operation in the breakdown-Townsend regime where discharge is supposed to be uniform.

Goci?, S.; Škoro, N.; Mari?, D.; Petrovi?, Z. Lj

2014-06-01

316

Influence of deposition conditions on mechanical properties of low-pressure chemical vapor deposited low-stress silicon nitride films  

International Nuclear Information System (INIS)

The effect of deposition temperature, deposition pressure, or input gas ratio (SiH2Cl2:NH3) on film stress was determined for low-pressure chemical vapor deposited silicon nitride films. Wafer curvature measurements were performed for films deposited on single crystal silicon and amorphous silica wafer substrates to determine film stress ?dep, biaxial modulus Ef+, and coefficient of thermal expansion ?f. Apparent plane strain film modulus E-barf' and hardness H were measured using depth-sensing indentation. Ellipsometry was used to measure film thickness tf and refractive index n. Infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), forward recoil energy spectroscopy (FReS), and Rutherford backscattering spectroscopy (RBS) experiments were performed to determine film composition. Although film deposition stress varied from -135 MPa (compressive) to 235 MPa (tensile) Ef+, E-barf', H, and ?f remained nearly constant. Infrared spectroscopy resolved only Si-N species for all films, and results from FReS on three films confirmed that the hydrogen content was negligible. RBS and XPS indicated that Si/N increased with increased compressive ?dep. Ellipsometry and RBS indicated that all films were silicon-rich, to a greater extent with increased compressive ?dep. As RBS indicated that atomic density decreased with increased compressive deposition stress, it was concluded that the deposition conditions changed both thermal and intrinsic deposition stress for all films. In particular, intrinsic stress was tensile, and became increasingly tensile for increased Si/N and decreased atomic density. Assuming thermal stress was similar for all films examined here, the intrinsic stress must have varied from changes dependent on the deposition conditions

2003-11-15

317

Pre-explosive Conduit Conditions of the 1997 Vulcanian Explosions at Soufrière Hills Volcano (Montserrat): Pressure and Vesicularity Distributions  

Science.gov (United States)

An authoritative case of Vulcanian eruptive dynamics is the series of 88 explosions that occurred between August and October 1997 at Soufrière Hills volcano on Montserrat Island. The state of the magmatic column just before a Vulcanian explosion is still poorly understood and conditions the eruptive style. We establish such a pre-explosive stratigraphy by 1) documenting the textures covering the range of the 1997 products, 2) quantitative analysis of water content in interstitial glass measured by Karl-Fischer Titration, and 3) combining these data with a simple model linking pre- and post-explosive vesicularities. The model takes in account that porosity evolves by decompression during an explosion, and that quenching may occur before the pressure inside the bubbles can reach atmospheric values. The stratigraphy reconstruction shows a three-part vertical layering of the conduit prior to explosion with overall denser values than those previously suggested. A dense and strongly degassed plug caps the column. It is underlain by a shallow transition zone featuring complex mingling between vesicular and dense magma up to 10 MPa. This transition zone contains heterogeneous amounts of exsolved gas that possibly explain the pulsatory nature of the Vulcanian jets. At higher depth lies a more homogeneous zone that gently decreases from 20 to 10 vol% vesicularity to reach near equilibrium degassing conditions around 80 MPa. This conduit stratigraphy gives the vision of a strongly heterogeneous magma column that suffered some gas loss prior to its disruption. Our analysis suggests that fragmenting such a composite magma column likely happens in stages that extend from explosion triggering to clasts ejection in the Vulcanian plume. The moderate porosities extending from depth to very shallow pressures, however, are propitious to general disruption of the column in a single coherent pulse.

Burgisser, A.; Poussineau, S.; Arbaret, L.; Druitt, T. H.; Giachetti, T.; Bourdier, J.

2009-12-01

318

An assessment of the failure rate for the beltline region of PWR pressure vessels during normal operation and certain transient conditions. Technical report  

International Nuclear Information System (INIS)

A study was conducted to assess the failure rate for the beltline region of a generic pressurized-water reactor (PWR) pressure vessel. This assessment included the evaluation of several normal operating and transient reactor conditions. Failure rates were calculated from a computer code that used fracture mechanics methods to model the failure process; random number generation techniques were used to simulate random variables and model their interaction in the failure-process. This investigation had three major objectives: (1) to better define the effect of neutron irradiation, material variation, and flaw distribution on the failure rate for the beltline region of PWR pressure vessels, (2) to estimate the relative margins against failure for normal operation and certain transient conditions associated with nuclear pressure vessels, and (3) to evaluate the current limitations for using fracture mechanics models to predict failure rates for nuclear pressure vessels

1981-01-01

319

The Influence of Collar on Surge Pressure Caused by the Drilling Fluid Viscous Force under Pumping Condition  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The study of surge pressure is of significant importance for the safety of drilling process because field practice shows that the surge pressure caused by fluid viscous force can cause a great damage to the drilling operation. The accurate calculation of surge pressure is directly related to the safety of the drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure ...

2013-01-01

320

Development of Evaluation Technique for Hydrogen Embrittlement Behavior of Metallic Materials Using in-situ SP Testing under Pressurized Hydrogen Gas Conditions  

International Nuclear Information System (INIS)

Recently, alternative and novel energy resources have been developed for use in the future because of the current environmental problems and exhaustion of fossil energy resources. Hydrogen energy has many merits, such as its environmental friendliness, easy storage, and easy production, but it also has disadvantages, in that it is highly combustible and explosive. In this study, a test procedure using a simple SP test under highly pressurized hydrogen gas conditions was established. In order to evaluate its applicability, SP tests were carried out using a stainless steel (SUS316L) sample under atmospheric, pressurized helium, and pressurized hydrogen gas conditions. The results under the pressurized hydrogen gas condition showed fissuring and produced a reduction of the elongation in the plastic instability region due to hydrogen embrittlement, showing the effectiveness of the current in-situ SP test

2011-11-01

 
 
 
 
321

Stability of supercritical water-cooled reactor during steady-state and sliding pressure start-up conditions  

International Nuclear Information System (INIS)

Full text of publication follows: The drastic change of fluid density in the reactor core of a supercritical water-cooled reactor (SCWR) gives rise to the concern of density wave stability. Using a single channel thermal-hydraulic model, the stability boundary maps of the U.S. reference SCWR design have been constructed for both the steady state and the sliding pressure start-up conditions. For the steady state, the supercritical water in the reactor core has been simulated using a three-region model - (1) a 'heavy fluid' with constant density, (2) a mixture of 'heavy fluid' and 'light fluid' similar to homogeneous-equilibrium two-phase mixture, and finally (3) a 'light fluid' which behaves like an ideal gas or superheated steam. The governing non-dimensional groups have been determined from a non-dimensional analysis of the conservation equations for this three-region supercritical water model. Two important non-dimensional groups, namely, Pseudo-Subcooling number (Npsub) and Expansion number (Nexp), which are similar to the Subcooling number (Nsub) and Phase Change number (Npch) commonly used in the analysis of the subcritical two-phase flow, have been identified for the supercritical region. The stability map in the supercritical region has been plotted in the Pseudo-Subcooling number versus Expansion number plane. It has been found that the U. S. reference SCWR design operates in the stable region with a big margin. Sensitivity studies have been performed with respect to the inlet orifice coefficient, system pressure and the inlet coolant velocity. It has been found that the stability boundary in the Npsub - Nexp plane is not sensitive to the system pressure and the inlet coolant velocity, but it is sensitive to the inlet orifice coefficient. This is consistent with the findings of the earlier research done for the subcritical two-phase flow. During the sliding pressure start-up operation of the SCWR, two-phase steam-water mixture at subcritical pressure will appear in the reactor core. A non-homogeneous (e. g., drift-flux) nonequilibrium two-phase flow model was applied. An exponential vapor generation rate for subcooled boiling was assumed along with a simplified but recent correlation for vapor drift velocity. The characteristic equation was numerically integrated, and the stability boundary map was plotted on the traditional Subcooling number versus Phase Change number plane. The effects of different two-phase flow models on the stability boundary have also been investigated. Thus, stability boundary maps have been constructed using four different models, namely, the Homogenous-Equilibrium model, the Homogenous-Nonequilibrium model, the Non-homogenous-Equilibrium model and the Non-homogenous-Non-Equilibrium model. It has been found that the Homogenous-Nonequilibrium model predicts the most conservative stability boundary at high Subcooling numbers, while the Homogenous-Equilibrium model yields the most conservative boundary at low Subcooling numbers. These maps are being used to develop the sliding pressure start-up strategies of the SCWR. Work is underway to expand the single channel model to a multi-channel model with neutronic feedback to study the local flow instabilities in a SCWR. (authors)

2005-10-02

322

Shape-controlled synthesis of diamond crystal by epitaxial growth under high pressure and high temperature conditions  

International Nuclear Information System (INIS)

In this paper, the diamond epitaxial growth mechanism has been studied in detail by employing several types of diamond as a seed in a catalyst—graphite system under high pressure and high temperature (HPHT) conditions. We find that the diamond nucleation, growth rate, crystal orientation, and morphology are significantly influenced by the original seeds. The smooth surfaces of seeds are beneficial for the fabrication of high-quality diamond. Our results reveal that the diamond morphology is mainly determined by the original shape of seeds in the early growth stage, but it has an adjustment process during the growth and leads to well symmetry. Additionally, we have also established the growth model for the twinned diamond grown on several seeds, and proposed the possible growth processes by tracking the particular shapes of seeds before and after treatment under HPHT conditions. These results suggest that the shape-controlled synthesis of diamond with well morphology can be realized by employing certain suitable diamond seeds. This work is expected to play an important role in the preparation of trustworthy diamond-based electronic and photonic devices. (interdisciplinary physics and related areas of science and technology)

2011-12-01

323

Environmentally-Assisted Cracking of Low-Alloy Reactor Pressure Vessel Steels under Boiling Water Reactor Conditions  

Energy Technology Data Exchange (ETDEWEB)

The present report summarizes the experimental work performed by PSI on the environmentally-assisted cracking (EAC) of low-alloy steels (LAS) in the frame of the RIKORR-project during the period from January 2000 to August 2001. Within this project, the EAC crack growth behaviour of different low-alloy reactor pressure vessel (RPV) steels, weld filler and weld heat-affected zone materials is investigated under simulated transient and steady-state BWR/NWC power operation conditions. The EAC crack growth behaviour of different low-alloy RPV steels was characterized by slow rising load (SRL) / low-frequency corrosion fatigue (LFCF) and constant load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. These tests revealed the following important interim results: Under low-flow and highly oxidizing (ECP >= 100 mV SHE) conditions, the ASME XI 'wet' reference fatigue crack growth curve could be significantly exceeded by cyclic fatigue loading at low frequencies (<0.001 Hz), at high and low load-ratios R, and by ripple loading near to DKth fatigue thresholds. The BWR VIP 60 SCC disposition lines may be significantly or slightly exceeded (even in steels with a low sulphur content) in the case of small load fluctuations at high load ratios (ripple loading) or at intermediate temperatures (200 -250 C) in RPV materials, which show a distinct susceptibility to dynamic strain ageing (DSA). (author)

Seifert, H.P.; Ritter, S

2002-02-01

324

Environmentally-Assisted Cracking of Low-Alloy Reactor Pressure Vessel Steels under Boiling Water Reactor Conditions  

International Nuclear Information System (INIS)

The present report summarizes the experimental work performed by PSI on the environmentally-assisted cracking (EAC) of low-alloy steels (LAS) in the frame of the RIKORR-project during the period from January 2000 to August 2001. Within this project, the EAC crack growth behaviour of different low-alloy reactor pressure vessel (RPV) steels, weld filler and weld heat-affected zone materials is investigated under simulated transient and steady-state BWR/NWC power operation conditions. The EAC crack growth behaviour of different low-alloy RPV steels was characterized by slow rising load (SRL) / low-frequency corrosion fatigue (LFCF) and constant load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. These tests revealed the following important interim results: Under low-flow and highly oxidizing (ECP >= 100 mV SHE) conditions, the ASME XI 'wet' reference fatigue crack growth curve could be significantly exceeded by cyclic fatigue loading at low frequencies (<0.001 Hz), at high and low load-ratios R, and by ripple loading near to DKth fatigue thresholds. The BWR VIP 60 SCC disposition lines may be significantly or slightly exceeded (even in steels with a low sulphur content) in the case of small load fluctuations at high load ratios (ripple loading) or at intermediate temperatures (200 -250 C) in RPV materials, which show a distinct susceptibility to dynamic strain ageing (DSA). (author)

2002-01-01

325

A study on the numerical instability of COBRA-series subchannel analysis codes at low-pressure and low-flow conditions  

International Nuclear Information System (INIS)

The numerical instability at low-pressure and low-flow conditions has been confirmed to be the common problem of the existing COBRA-series subchannel analysis codes. In addition, the range of operating conditions at which the analyses by the codes are impossible has been evaluated. To evaluate the MATRA's inapplicable range of operating conditions of the SMART core that is to be operated at the low flow condition, i.e. about 30% of the flow of the existing commercial pressurized water reactors at the steady-state condition, the analyses of various operating conditions were performed by using several representative COBRA-series subchannel analysis codes including MATRA. TORC of CE, COBRA3CP of Siemens/KWU, COBRA4I of PNL, and MATRA of KAERI were chosen as the subchannel analysis codes to be evaluated. The various operating conditions used in the CHF tests carried out at the Winfrith Establishment of UKAEA were chosen as the conditions to be analyzed. As the result, the numerical instabilities at low-pressure and low-flow conditions occurred in the analyses by all of the codes. It was revealed that the MATRA code, which numerically more stable thatn the other codes, was not able to analyze the conditions of the pressure not more than 100 bar and the mass velocity not more than 300 kg/sec-m2. Hereafter it is required to find out the exact reason for the numerical instability of the existing COBRA-series subchannel analysis codes at low-pressure and low-flow conditions and to devise the new method to get over that numerical problem

2001-05-01

326

Behavior of low alloy steel SA-508 and carbon steel A-410b in operation and shutdown conditions in primary loop of pressurized water reactor (PWR)  

International Nuclear Information System (INIS)

The corrosion rate of low alloy steel SA-508 and carbon steel A-410b in simulated operation and shutdown conditions of pressurized water reactor has been determined Moreover potentiodynamic polarization curves and galvanic effect through coupling of AISI-304 have been carried out under shutdown simulated condition. (Author) 8 refs

2000-01-01

327

Study of hydride blisters grown on Zr-2.5Nb pressure tube spool piece under simulated condition of in-reactor pressure and temperature  

International Nuclear Information System (INIS)

Indian Pressurised Heavy Water Reactor (PHWR) have pressure tubes, made from zirconium alloy. These pressure tubes undergo corrosion with the high temperature (300 deg C) heavy water coolant under the reactor environment and pick up a part of hydrogen generated as result of this corrosion reaction. This hydrogen affects the integrity of pressure tubes in many ways; nucleation and growth of hydride blisters being one of them. The present study has been carried out to understand the mechanisms of nucleation and growth of hydride blisters and their effect on the serviceability of the component in the reactor environment. (author)

2006-01-01

328

Crack growth behaviour of low alloy steels for pressure boundary components under transient light water reactor operating conditions (CASTOC)  

Energy Technology Data Exchange (ETDEWEB)

The CASTOC project addresses environmentally assisted cracking (EAC) phenomena in low alloy steels used for pressure boundary components in both Western type boiling water reactors (BWR) and Russian type pressurised water reactors (VVER). It comprises the four work packages (WP): inter-laboratory comparison test (WP1); EAC behaviour under static load (WP2), EAC behaviour under cyclic load and load transients (WP3); evaluation of the results with regard to their relevance for components in practice (WP4). The use of sophisticated test facilities and measurement techniques for the on-line detection of crack advances have provided a more detailed understanding of the mechanisms of environmentally assisted cracking and provided quantitative data of crack growth rates as a function of loading events and time, respectively. The effect of several major parameters controlling EAC was investigated with particular emphasis on the transferability of the results to components in service. The obtained crack growth rate data were reflected on literature data and on commonly applied prediction curves as presented in the appropriate Code. At relevant stress intensity factors it could be shown that immediate cessation of growing cracks occurs after changing from cyclic to static load in high purity oxygenated BWR water and oxygen-free VVER water corresponding to steady state operation conditions. Susceptibility to environmentally assisted cracking under static load was observed for a heat affected zone material in oxygenated high purity water and also in base materials during a chloride transient representing BWR water condition below Action Level 1 of the EPRI Water Chemistry Guidelines according to the lectrical conductivity of the water but in the range of Action Level 2 according to the content of chlorides. Time based crack growth was also observed in one Russian type base material in oxygenated VVER water and in one Western type base material in oxygenated high purity BWR water at stress intensity factors above the limit for linear elastic fracture mechanics. There is evidence that the prediction curves of the ASME Boiler and Pressure Vessel Code Section XI, Appendix A are not conservative for some relevant cases with regard to crack growth rates under cyclic load even in oxygenated high purity BWR water. The CASTOC results have provided an important contribution to the understanding of crack growth behavior on the one hand as a function of time and on the other hand as a consequence of the number and height of loading events. This is an important key for the evaluation of transient events, which may occur in a plant during service. (orig.)

Foehl, J.; Weissenberg, T. [Materialpruefungsanstalt, Univ. Stuttgart (Germany); Gomez-Briceno, D.; Lapena, J. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT) (Spain); Ernestova, M.; Zamboch, M. [Nuclear Research Inst. (NRI) (Czech Republic); Seifert, H.P.; Ritter, S. [Paul Scherrer Inst. (PSI) (Switzerland); Roth, A.; Devrient, B. [Framatome ANP GmbH (F ANP) (Germany); Ehrnsten, U. [Technical Research Centre of Finland (VTT) (Finland)

2004-07-01

329

Crack growth behaviour of low alloy steels for pressure boundary components under transient light water reactor operating conditions (CASTOC)  

International Nuclear Information System (INIS)

The CASTOC project addresses environmentally assisted cracking (EAC) phenomena in low alloy steels used for pressure boundary components in both Western type boiling water reactors (BWR) and Russian type pressurised water reactors (VVER). It comprises the four work packages (WP): inter-laboratory comparison test (WP1); EAC behaviour under static load (WP2), EAC behaviour under cyclic load and load transients (WP3); evaluation of the results with regard to their relevance for components in practice (WP4). The use of sophisticated test facilities and measurement techniques for the on-line detection of crack advances have provided a more detailed understanding of the mechanisms of environmentally assisted cracking and provided quantitative data of crack growth rates as a function of loading events and time, respectively. The effect of several major parameters controlling EAC was investigated with particular emphasis on the transferability of the results to components in service. The obtained crack growth rate data were reflected on literature data and on commonly applied prediction curves as presented in the appropriate Code. At relevant stress intensity factors it could be shown that immediate cessation of growing cracks occurs after changing from cyclic to static load in high purity oxygenated BWR water and oxygen-free VVER water corresponding to steady state operation conditions. Susceptibility to environmentally assisted cracking under static load was observed for a heat affected zone material in oxygenated high purity water and also in base materials during a chloride transient representing BWR water condition below Action Level 1 of the EPRI Water Chemistry Guidelines according to the lectrical conductivity of the water but in the range of Action Level 2 according to the content of chlorides. Time based crack growth was also observed in one Russian type base material in oxygenated VVER water and in one Western type base material in oxygenated high purity BWR water at stress intensity factors above the limit for linear elastic fracture mechanics. There is evidence that the prediction curves of the ASME Boiler and Pressure Vessel Code Section XI, Appendix A are not conservative for some relevant cases with regard to crack growth rates under cyclic load even in oxygenated high purity BWR water. The CASTOC results have provided an important contribution to the understanding of crack growth behavior on the one hand as a function of time and on the other hand as a consequence of the number and height of loading events. This is an important key for the evaluation of transient events, which may occur in a plant during service. (orig.)

2004-10-06

330

Small angle X-ray scattering study of the effect of pressure on the aggregation of asphaltene fractions in petroleum fluids under near-critical solvent conditions  

Energy Technology Data Exchange (ETDEWEB)

Small angle X-ray scattering was used to determine the effect of pressure on the extent of asphaltene aggregation for a system under near-critical conditions. A mixture containing 60 vol% Crude Oil A in n-pentane was studied at 110[degree]C, at pressures ranging from 25 to 400 bar. As the pressure of the near-critical solution is isothermally decreased, these results indicate (1) an increase in the extent of asphaltene aggregation and/or; (2) increased attractive interactions among aggregates. Information derived from different regions of the X-ray scattering curve indicate increasing aggregation with decreasing pressure. From these experimental results, together with theoretical interpretation, we infer that as the pressure is reduced, increased aggregation of asphaltenes results which may contribute to formation damage in hydrocarbon reservoirs, and to fouling in hydrotreatment and cracking catalysts. 71 refs., 10 figs., 2 tabs.

Carnahan, N.F.; Quintero, L. (Rice Univ., Houston, TX (United States)); Pfund, D.M.; Fulton, J.L.; Smith, R.D. (Pacific Northwest Lab., Richland, WA (United States)); Capel, M. (Brookhaven National Lab., Upton, NY (United States)); Leontaritis, K. (Core Lab., Houston, TX (United States))

1993-08-01

331

An evaluation of the quantitative effects on radon gas from the modification of a home heating and air conditioning system  

International Nuclear Information System (INIS)

The quantitative effects associated with the design, construction, operation, environmental and meteorological conditions on radon gas levels in a typical residential dwelling with a basement, having a measured radon level of approximately 20 pico-curies/liter (pCi/L), are evaluated. After several mechanical and electrical modifications are made on the dwelling's heating system, two different furnace breathing modes are studied. The effect on radon levels in the dwelling are observed as the furnace receives all of its combustion, draft and ventilation air - as the experiment alternates, on a bi-weekly basis - from inside and then outside the dwelling. Radon, barometric pressure, outside temperature, relative humidity, wind-speed and direction are monitored continuously; special household activity in the dwelling is also observed. A novel differential air pressure technique is used to measure inside versus outside house air pressure variations, twice each day, resulting from meteorological conditions, dwelling activity, and the furnace breathing mode. A rigorous statistical analysis is employed that includes sequential linear regression of time-series data, trend corrections to remove variations that contribute to the variance in the data without addition useful information. A novel approach using an electrical analog, to screen out unwanted variations is applied, by utilizing a computer routine to simulate the effect of an electronic RC filter, to achieve the desired analytical discrimination

1991-01-01

332

Evaluation of Low Pressure Fogging System for Improving Crop Yield of Tomato (Lycopersicon esculentum Mill.: Grown under Heat Stress Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available In Mediterranean regions, many tomato plants are grown throughout the hot summer period (May–September in sheltered cultivation, mainly for plant protection reasons. Most of the shelters that are used are low cost net houses covered with 50 mesh insect proof net. In most cases these net houses have a flat roof and no ventilation or climate control measures. This insufficient ventilation during the hot summer leads to above optimal air temperatures and causes moderate heat stress inside the shelters, which leads to yield reduction. The aim of this study was to evaluate the ability of a simple and inexpensive low pressure fogging system installed in a naturally ventilated net house to lower temperatures and improve the yield during the summer. The study showed that in areas where relative air humidity (RH during the daytime is less than 60%, tomato plants improved their performance when grown through the summer in net houses under moderate heat stress. Under fogging conditions pollen grain viability and fruit set were significantly improved. This improvement influenced the yield picked during September (104–136 DAP. However, total seasonal yield was not affected by the fogging treatment.

Kobi Shilo

2013-06-01

333

Surface charging patterns of stainless alloys - Effect of ageing in conditions of primary cooling circuit of pressurized water reactors  

Science.gov (United States)

The predominance of electrostatic interactions in the mechanism of particle deposition onto solid surfaces is well documented. Therefore, an electrostatic approach has been used to predict the behavior of activated corrosion products in the primary cooling circuit of a pressurized water reactor (PWR). Only few results have been published on the potential at the interface of metallic alloys and aqueous solutions, even at room temperature. In this study, we present results about the characterization of representative materials such as Inconel 690, stainless steel 304 and Zircaloy 4 at room temperature, for pristine polished samples as well as after an 80-day ageing step in physico-chemical conditions similar to those of a primary circuit (360 °C, boron 1 g L-1 (as H3BO3), lithium 2 mg L-1 (as LiOH), hydrogen 30 cm3 kg-1). The surface potentials of these alloys have been determined using a streaming current method for pH from 3 to 7. Isoelectric points between 4.1 and 4.6 have been found for all samples and there is no effect of the ageing step. These values have been confirmed by adhesion studies of grafted latex particles either positively charged (amidine surface groups) or negatively charged (carboxylate groups) at pH 3.3 and pH 5.5. The results show that particles deposition is favored only when they carry a charge opposite to the substrate surfaces.

Martin Cabanas, B.; Lützenkirchen, J.; Leclercq, S.; Barboux, P.; Lefèvre, G.

2012-11-01

334

Numerical investigation of the spray-mesh-turbulence interactions for high-pressure, evaporating sprays at engine conditions  

International Nuclear Information System (INIS)

This work presents a numerical methodology to simulate evaporating, high pressure Diesel sprays using the Eulerian-Lagrangian approach. Specific sub-models were developed to describe the liquid spray injection and breakup, and the influence of the liquid jet on the turbulence viscosity in the vicinity of the nozzle. To reduce the computational time and easily solve the problem of the grid dependency, the possibility to dynamically refine the grid where the fuel-air mixing process takes place was also included. The validity of the proposed approach was firstly verified simulating an evaporating spray in a constant-volume vessel at non-reacting conditions. The availability of a large quantity of experimental data allowed us to investigate in detail the effects of grid size, ambient diffusivity and used spray sub-models. In this way, different guidelines were derived for a successful simulation of the fuel-air mixture formation process. Finally, fuel injection and evaporation were simulated in an optical engine geometry and computed mixture fraction distributions were compared with experimental data.

2011-02-01

335

Numerical investigation of the spray-mesh-turbulence interactions for high-pressure, evaporating sprays at engine conditions  

Energy Technology Data Exchange (ETDEWEB)

This work presents a numerical methodology to simulate evaporating, high pressure Diesel sprays using the Eulerian-Lagrangian approach. Specific sub-models were developed to describe the liquid spray injection and breakup, and the influence of the liquid jet on the turbulence viscosity in the vicinity of the nozzle. To reduce the computational time and easily solve the problem of the grid dependency, the possibility to dynamically refine the grid where the fuel-air mixing process takes place was also included. The validity of the proposed approach was firstly verified simulating an evaporating spray in a constant-volume vessel at non-reacting conditions. The availability of a large quantity of experimental data allowed us to investigate in detail the effects of grid size, ambient diffusivity and used spray sub-models. In this way, different guidelines were derived for a successful simulation of the fuel-air mixture formation process. Finally, fuel injection and evaporation were simulated in an optical engine geometry and computed mixture fraction distributions were compared with experimental data.

Lucchini, Tommaso, E-mail: tommaso.lucchini@polimi.i [Internal Combustion Engine Group, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini 4, 20156 Milan (Italy); D' Errico, Gianluca; Ettorre, Daniele [Internal Combustion Engine Group, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini 4, 20156 Milan (Italy)

2011-02-15

336

Stability of Hydrogen-Bonded Supramolecular Architecture under High Pressure Conditions: Pressure-Induced Amorphization in Melamine-Boric Acid Adduct  

International Nuclear Information System (INIS)

The effects of high pressure on the structural stability of the melamine-boric acid adduct (C3N6H6 2H3BO3, M 2B), a three-dimensional hydrogen-bonded supramolecular architecture, were studied by in situ synchrotron X-ray diffraction (XRD) and Raman spectroscopy. M 2B exhibited a high compressibility and a strong anisotropic compression, which can be explained by the layerlike crystal packing. Furthermore, evolution of XRD patterns and Raman spectra indicated that the M 2B crystal undergoes a reversible pressure-induced amorphization (PIA) at 18 GPa. The mechanism for the PIA was attributed to the competition between close packing and long-range order. Ab initio calculations were also performed to account for the behavior of hydrogen bonding under high pressure.

2009-01-01

337

Experimental Study of Abiotic Organic Synthesis at High Temperature and Pressure Conditions: Carbon Isotope and Mineral Surface Characterizations  

Science.gov (United States)

Abiotic organic synthesis processes have been proposed as potential mechanisms for methane generation in subseafloor hydrothermal systems on Earth, and on other planets. To better understand the detailed reaction pathways and carbon isotope fractionations in this process under a wide range of physical and chemical conditions, hydrothermal experiments at high temperature (750 °C) and pressure (0.55 GPa) were performed using piston cylinder apparatus. Formic acid was used as the source of CO2 and H2, and magnetite was the mineral catalyst. The chemical and carbon isotopic compositions of dissolved organic products were determined by GC-C-MS-IRMS, while organic intermediaries on the mineral catalyst were characterized by Pyrolysis-GC-MS. Among experimental products, dissolved CO2 was the dominant carbon species with a relative abundance of 88 mol%. Dissolved CH4 and C2H6 were also identified with a mole ratio of CH4 over C2H6 of 15:1. No dissolved CO was detected in the experiment, which might be attributable to the loss of H2 through the Au capsule used in the experiments at high temperature and pressure conditions and corresponding conversion of CO to CO2 by the water-gas shift reaction. Carbon isotope results showed that the ?13C values of CH4 and C2H6 were -50.3‰ and -39.3‰ (V-PDB), respectively. CO2 derived from decarboxylation of formic acid had a ?13C value of -19.2‰, which was 3.2‰ heavier than its source, formic acid. The ?13C difference between CO2 and CH4 was 31.1‰, which was higher than the value of 9.4‰ calculated from theoretical isotopic equilibrium predictions at experimental conditions, suggesting the presence of a kinetic isotope effect. This number was also higher than the values (4.6 to 27.1‰) observed in similar experiments previously performed at 400 °C and 50 MPa with longer reaction times. CH4 is 11.0‰ less enriched in 13C than C2H6. Alcohols were observed as carbon compounds on magnetite surfaces by Pyrolysis-GC-MS, which confirms the hypothesis regarding the reaction pathways of hydrothermal abiotic organic synthesis proposed by Fu et al. (2007, 2008). In this proposed pathway, hydroxymethylene (-CHOH) groups serve as organic intermediaries on mineral surfaces while dissolved H2 serves as a chain terminator/breaker to generate short chain hydrocarbons and oxygenated compounds. This pathway is different from the carbide polymerization theory of Fischer-Tropsch-type (FTT) synthesis in a gas phase. The observed increase of ?13C values of C1 and C2 alkanes with carbon number in our hydrothermal experiments can be readily interpreted by hydroxymethylene pathway, and might be used to differentiate between hydroxymethylene and carbide polymerization pathways. Carbon isotope analysis of alcohols on mineral catalyst surfaces is under way to provide further constraints on formation of organic compounds by FTT in hydrothermal systems.

Fu, Q.; Socki, R. A.; Niles, P. B.

2010-12-01

338

Experimental Study of Abiotic Organic Synthesis at High Temperature and Pressure Conditions: Carbon Isotope and Mineral Surface Characterizations  

Science.gov (United States)

Abiotic organic synthesis processes have been proposed as potential mechanisms for methane generation in subseafloor hydrothermal systems on Earth, and on other planets. To better understand the detailed reaction pathways and carbon isotope fractionations in this process under a wide range of physical and chemical conditions, hydrothermal experiments at high temperature (750 C) and pressure (0.55 GPa) were performed using piston cylinder apparatus. Formic acid was used as the source of CO2 and H2, and magnetite was the mineral catalyst. The chemical and carbon isotopic compositions of dissolved organic products were determined by GC-C-MS-IRMS, while organic intermediaries on the mineral catalyst were characterized by Pyrolysis-GC-MS. Among experimental products, dissolved CO2 was the dominant carbon species with a relative abundance of 88 mol%. Dissolved CH4 and C2H6 were also identified with a mole ratio of CH4 over C2H6 of 15:1. No dissolved CO was detected in the experiment, which might be attributable to the loss of H2 through the Au capsule used in the experiments at high temperature and pressure conditions and corresponding conversion of CO to CO2 by the water-gas shift reaction. Carbon isotope results showed that the 13C values of CH4 and C2H6 were -50.3% and -39.3% (V-PDB), respectively. CO2 derived from decarboxylation of formic acid had a (sigma)C-13 value of -19.2%, which was 3.2% heavier than its source, formic acid. The (sigma)C-13 difference between CO2 and CH4 was 31.1%, which was higher than the value of 9.4% calculated from theoretical isotopic equilibrium predictions at experimental conditions, suggesting the presence of a kinetic isotope effect. This number was also higher than the values (4.6 to 27.1%) observed in similar experiments previously performed at 400 C and 50 MPa with longer reaction times. CH4 is 11.0% less enriched in C-13 than C2H6. Alcohols were observed as carbon compounds on magnetite surfaces by Pyrolysis-GC-MS, which confirms the hypothesis regarding the reaction pathways of hydrothermal abiotic organic synthesis proposed by Fu et al. (2007, 2008). In this proposed pathway, hydroxymethylene (-CHOH) groups serve as organic intermediaries on mineral surfaces while dissolved H2 serves as a chain terminator/breaker to generate short chain hydrocarbons and oxygenated compounds. This pathway is different from the carbide polymerization theory of Fischer- Tropsch-type (FTT) synthesis in a gas phase. The observed increase of (sigma)C-13 values of C1 and C2 alkanes with carbon number in our hydrothermal experiments can be readily interpreted by hydroxymethylene pathway, and might be used to differentiate between hydroxymethylene and carbide polymerization pathways. Carbon isotope analysis of alcohols on mineral catalyst surfaces is under way to provide further constraints on formation of organic compounds by FTT in hydrothermal systems.

Fu, Qi; Socki, R. A.; Niles, P. B.

2010-01-01

339

RELAP5 Capability to Predict Pressure Wave Propagation Phenomena in Single- and Two-Phase Flow Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Correct evaluation of the hydrodynamic loads induced by large and rapid pressure waves propagating with the speed of sound along the reactor piping systems and Reactor Pressure Vessel (RPV) is an important and difficult issue of nuclear power plant safety. The pressure shock transients and resulting hydrodynamic loads on the pipes and RPV structures are commonly calculated with one-dimensional thermo-hydraulic system codes such as RELAP5, TRACE, DRAKO and ROLAST. In Sweden, the most widely us...

2012-01-01

340

The accuracy of the crystal chemical parameters at high-pressure conditions from single-crystal X-ray diffraction in diamond-anvil cell  

DEFF Research Database (Denmark)

The high-pressure studies have been increasingly applied for the investigation of crystal structures under non ambient-conditions and phase-transition of minerals forming the Earthâ??s lower crust and upper mantle. The knowledge of the behavior of minerals under non-ambient conditions has important applications also in the materials science as it can provide useful information about the properties and performance of new materials. Over the past decades, the research in this field has been strongly developed due to the advances in computer capabilities and to the technological improvements of X-ray instruments. At the same time, the high-pressure experiments have benefited by the strong improvements on the high-pressure devices, in particular the diamond-anvil cell (DAC). The aim of this research project is to assess the quality of the data obtained by means of the single-crystal X-ray diffraction technique through the study of different mineral phases. The procedure for setting up an experiment under high-pressure conditions, using a single crystal as sample held within a DAC, are presented here with all the details of the in situ measurements at high-pressure conditions. The research project started with a comparison between two different DACs, in order to define the capabilities of one of the most common types of pressure device, the ETH-type DAC. Application examples of data quality analysis have been conducted on pyroxenes (NaInSi2O6, orthoenstatite MgSiO3 and LiCrSi2O6), which are important components of the Earthâ??s lower crust and upper mantle. In the last part of the thesis, the berthierite sulfosalt (FeSb2S4) was measured under pressure in order to test the data accuracy on a slightly more complicated structure

Periotto, Benedetta

2012-01-01

 
 
 
 
341

Desaturation of a clay-stone around a ventilated gallery: numerical modelling of pressures and water contents under various conditions  

International Nuclear Information System (INIS)

Document available in extended abstract form only. We present simulation tests focusing on the drying process around a gallery in an initially saturated (water-filled) porous clay rock, in the framework of a research on the isolation properties and hydro-mechanical behaviour of a clayey geologic repository for radioactive waste. The saturated/unsaturated hydrodynamic parameters used in these tests correspond to a hypothetical clay-stone, similar to the 130 m thick Callovo-Oxfordian formation located between depths 400 m and 600 m at the Meuse / Haute-Marne (MHM) Underground Research Laboratory (URL), operated by ANDRA (Bure, France). The simulations tests were designed according to 3 'types' of computational geometries. The drying period was extended to very long time scales in some cases. The clay rock was taken homogeneous in many tests, but the damaged zone was represented in some (Type III) tests. Type (I) tests are conducted in a simplified non circular geometry. Assuming a square cross-section for the drift, the drying process is obtained by imposing a fixed suction on a flat piece of wall at the roof. The bottom of the porous domain coincides with the roof of the drift. The imposed suction at the roof affects the near field pressure both horizontally and vertically. Type (II) tests reproduce the circular cylindrical geometry of a partially or perfectly filled gallery, with drying conditions imposed at both ends of the drift. Finally, Type (III) tests consider the case of an empty ventilated cylindrical drift with circular cross-section. In this case the drying is imposed on the curved walls of the drift via a transmission mechanism thanks the 'macro-porous immersion' method. In all cases, the drying of the porous clay rock is modeled by imposing a suction condition (?), obtained from relative air humidity (HR) via Kelvin's law (?). Briefly, the macro-porous immersion method consists in the following interrelated procedures. First, the volumetric excavation (cylindrical drift) is discretized and internalized as a 3D 'macro-porous' body within the computational porous domain. Secondly, the properties of this internal macro-porous body are adjusted in such a way that it will transmit properly the imposed suction (or pressure, or flux, as the case may be) from external to internal boundaries. Here, the suction is imposed on the entry face of the gallery (external boundary), and it is transmitted to the clay/gallery interface (internal boundary). The macro-porous body has a porosity of 100%, a large Darcy permeability compared to the clay-stone, and other special nonlinear and non-isotropic unsaturated properties. Briefly, numerical modelling was conducted with BIGFLOW 3D, an implicit finite volume solver of the saturated/unsaturated Richards equation in mixed form (moisture content '?', pressure head 'h'). We used the nonlinear Van Genuchten / Mualem conductivity and water retention curves (K(h); ?(h)) in the unsaturated zone. A specific elastic storativity (SS) was added in the saturated zone to take into account slight deformation mechanisms in a simplified way (the storativity model does not deal with total stress; it assumes ??EFF ? ?p, where p is pore pressure, and ?EFF is Terzaghi's effective stress taken positive when extensional). Finally, the BIGFLOW code can also handle 3D heterogeneity and nonlinear diagonal anisotropy, that is: [Kii(h,x,y,z); ?(h,x,y,z)]. We used these additional capabilities of the code in some of the tests. Figs.1 and 2 show the evolution of desaturation for a 'Type I' test, i.e., with suction imposed on a flat horizontal piece of wall located at the roof of the drift. The drift 'radius' (half-side) is R=2 m. The case shown here is only 'moderately dry': the prescribed suction is ?=3000 m (?30 MPa), corresponding to HR=80.74% at TAIR=25 C and PATM=1 bar (according to Kelvin's law). The imposed desaturation of the porous medium at the drift wall is significant (more than 50% drop of the degree of saturation). The steady state is attained after ?10-30 years, due to the infl

2012-10-01

342

Hydrogen transfer hydrocracking of C. procera latex under ambient pressure conditions to get value added chemicals and fuels  

Energy Technology Data Exchange (ETDEWEB)

Biomass is renewable source of energy while the reserves of petroleum are being depleted. The latex of a potential petrocrop, Calotropis procera, a laticifer, arid-plant which is rich in hydrocarbon type triterpene compounds etc. was found to be a better feed stock for thermal hydrocracking as compared to whole plant biomass in terms of liquid product yield. Studies of chemical reaction dynamics of the thermal cracking of latex at 200-400[degree]C showed that the process should be termed as hydrogen-transfer (H-T) hydrocracking of latex under ambient pressure conditions. The hydrogen rich cracked triterpenoids act as the H-donors in this process, where nascent hydrogen atoms and free radicals chemically plug the cracked moieties to stabilise these. Latex was also coagulated and the H-T hydrocracking of the feedstock coagulum gave a higher yield of cracked oil in comparison to that from the dried latex. The temperature for hydrocracking of latex has been optimized to 350[degree]C and molecular sieve was found to catalyse the H-T hydrocracking process to yield more liquid product. The distillation range of cracked latex oil (CLO) obtained from H-T hydrocracking of C. procera latex indicated that it can be used as fuel oil or substitute for diesel fuel. Moreover, CLO resembled diesel fuels and was predominantly paraffinic in nature as characterised by NMR and FTIR spectral analysis. A process has been recommended for getting value added fuels and chemicals from C. procera latex. 29 refs., 5 figs., 3 tabs.

Sharma, D.K.; Behera, B.K.; Arora, M. (Indian Institute of Technology, New Delhi (India). Fuels and Biofuels Engineering Lab.)

1994-01-01

343

Pre-explosive conduit conditions of the 1997 Vulcanian explosions at Soufrière Hills Volcano, Montserrat: I. Pressure and vesicularity distributions  

Science.gov (United States)

An authoritative case of Vulcanian eruptive dynamics is the series of 88 explosions that occurred between August and October 1997 at Soufrière Hills volcano on Montserrat Island. The state of the magmatic column just before a Vulcanian explosion is still poorly understood, but conditions the eruptive style. This study establishes such a pre-explosive stratigraphy by 1) documenting the textures covering the range of the 1997 products, 2) quantitative analysis of H 2O content in interstitial glass measured by Karl-Fischer Titration, and 3) combining these data with a simple model linking pre- and post-explosive vesicularities. The model shows that syn-explosive degassing affects greatly the way porosity evolves by decompression during an explosion. The stratigraphy reconstruction shows a three-part vertical layering of the conduit prior to explosion with overall denser values than those previously suggested. A dense and strongly degassed plug caps the column. It is underlain by a shallow transition zone featuring complex mingling between vesicular and dense magma up to 10 MPa. At higher pressure, up to 80 MPa, lies a more homogeneous zone of relatively dense (10-20 vol.%) magma, which was emplaced under partly open-system degassing. This conduit stratigraphy gives the vision of a strongly heterogeneous magma column immediately prior to its disruption. Our analysis suggests that fragmenting such a composite magma cannot happen in a single coherent pulse, but rather as stages. The transition zone contains heterogeneous amounts of exsolved gas that could explain the pulsatory nature of the Vulcanian jets at the beginning of the explosions. This contrasts with the nearly constant vesicularities of the deeper part of the pre-explosive magma column, which are propitious to a general, short-lived disruption.

Burgisser, Alain; Poussineau, Stéphane; Arbaret, Laurent; Druitt, Timothy H.; Giachetti, Thomas; Bourdier, Jean-Louis

2010-07-01

344

Dynamic observations of the effect of pressure and temperature conditions on the selective synthesis of carbon nanotubes  

International Nuclear Information System (INIS)

In situ transmission electron microscopy studies have been carried out to determine the effect of temperature and pressure on the growth of carbon nanotubes by the Ni-catalyzed chemical vapour deposition of acetylene. The temperature range explored was 450-650 deg. C and the acetylene pressure range was 0.8-20 mTorr. Our observations show that straight, single-wall, carbon nanotubes tend to form at higher temperatures and lower pressures while bent, zigzag, multi-wall carbon nanotubes form at lower temperatures and higher pressures. These results can be understood as the result of competition between the arrival rate of carbon and the nucleation rate of carbon hexagons (which increases at high pressure and low temperature), and the annealing rate of the 5-ring and 7-ring defects that are responsible for the nanotube curvature

2007-03-28

345

Influence of the synthesis conditions of silicon nanodots in an industrial low pressure chemical vapor deposition reactor  

International Nuclear Information System (INIS)

Experiments conducted in an industrial tubular low pressure chemical vapor deposition (LPCVD) reactor have demonstrated the reproducibility and spatial uniformity of silicon nanodots (NDs) area density and mean radius. The wafer to wafer uniformity was satisfactory (density and radius standard deviations 11 and 6.5 x 1011 NDs/cm2 for the two highest silane pressures tested in the range 60-150 Pa

2008-03-15

346

Asthma and climatic conditions: experience from Bermuda, an isolated island community.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A retrospective study of patients attending the emergency department with acute asthma was performed in Bermuda. Climatic data (barometric pressure, rainfall, humidity, and wind strength and direction) were obtained and compared with frequency of exacerbations of asthma. Three factors--namely, relative humidity, average daily temperature, and northeasterly winds--were found to be related to worsening asthma. Owing to Bermuda's lack of pollution and aeroallergens it was thought that these weat...

Carey, M. J.; Cordon, I.

1986-01-01

347

Heat transfer parameters for glass-peened calandria tube in pressure tube and calandria tube contact conditions  

International Nuclear Information System (INIS)

During a postulated event of large LOCA in CANDU reactors, the pressure tube may balloon to contact with its surrounding calandria tube to transfer heat to the moderator. To confirm the integrity of the fuel channel after the contact with a given moderator subcooling, many experiments have been performed in the last three decades by applying different pressure tube heatup rates, different pressure tube pressures and different moderator subcoolings for calandria tubes with smooth outer surface and glass-peened surface. A concept of Equivalent Moderator Subcooling (EMS) has been put forward to determine integrity of fuel channel upon pressure tube/calandria tube contact based on the existing experiment results. This concept has been presented in another work. In this work, the contact thermal conductance between pressure tube and calandria tube, critical heat flux, minimum film boiling temperature, empirical methods for nucleate boiling and film boiling heat transfer coefficient on the glass-peened calandria tube surface are discussed and estimated based on some experimental results and the EMS concept. These parameters are confirmed by simulating the existing experiments using a computer code. The estimated results may help detailed analyses on fuel channel integrity upon PT/CT contact if necessary. (author)

2010-05-24

348

Experimental and theoretical investigation of the dynamic behaviour of a reactor pressure vessel and a primary steam pipe line under operating conditions  

International Nuclear Information System (INIS)

A new remotely operated snapback excitation system was used for vibration tests at the pressure vessel and a primary steam pipe of a nuclear power plant under different operating conditions (temperature 20-285"0C in steps, internal pressure 0-70 bar). The measured acceleration-, displacement- and strain time histories were compared with results of pre-calculations of the test load cases using a FE-model. Additionally, a modal analysis of the measured signals permitted a comparison of resonance frequencies, mode shapes and damping values of the system investigated with the modal parameters of the computation model. (orig.)

1985-01-01

349

RELAP5 Capability to Predict Pressure Wave Propagation Phenomena in Single- and Two-Phase Flow Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Correct evaluation of the hydrodynamic loads induced by large and rapid pressure waves propagating with the speed of sound along the reactor piping systems and Reactor Pressure Vessel (RPV is an important and difficult issue of nuclear power plant safety. The pressure shock transients and resulting hydrodynamic loads on the pipes and RPV structures are commonly calculated with one-dimensional thermo-hydraulic system codes such as RELAP5, TRACE, DRAKO and ROLAST. In Sweden, the most widely used computer code for this purpose is RELAP5. This code needs, therefore, to be assessed for its capability to predict pressure wave behavior. The conducted assessment involves simulations of single- and two-phase shock-tube problems and two-phase blowdown as well as water hammer experiments. The performed numerical experiments clearly show that RELAP5, with the proper time step and spatial mesh size, is capable of predicting the complex dynamics of single- and two-phase pressure wave phenomena with good to reasonable accuracy.

Lukasz Sokolowski

2012-01-01

350

Self-overcoming of the boiling condition by pressure increment in a water target irradiated by proton beam  

Energy Technology Data Exchange (ETDEWEB)

An experiment was conducted to examine and visualize the boiling phenomena inside a water target by irradiating it with a proton beam from MC-50 cyclotron. The boiling phenomena were recorded with a CMOS camera. While an increase of the fraction of the water vapor volume is generally considered to be normal when water is boiled by a proton beam, our experiment showed the opposite result. The volume expansion of the liquid water exceeded the compressibility of the initial air volume. A grid structure in front of the entrance window foil held the target volume constant. Therefore, the phenomena inside the target underwent an isochoric process, and the pressure inside the target was increased rapidly beyond the pressure at the boiling point. Consequently, there was no more bulk boiling in the Bragg-peak region in the target water. Our results show that the boiling of the water can be controlled by controlling the equilibrium pressure of the water target.

Hong, Bong Hwan, E-mail: burnn@kirams.re.kr [Korea Institute of Radiological and Medical Sciences (KIRMAS), 75 Nowon-Gil, Nowon-Gu, Seoul 139-706 (Korea, Republic of); Kang, Joonsun; Jung, In Su; Ram, Han Ga; Park, Yeun Soo [Korea Institute of Radiological and Medical Sciences (KIRMAS), 75 Nowon-Gil, Nowon-Gu, Seoul 139-706 (Korea, Republic of); Cho, Hyung Hee [Department of Mechanical Engineering, Yonsei University, 134 Sinchon-Dong, Seodaemun-Gu, Seoul 120-749 (Korea, Republic of)

2013-11-11

351

The dynamics crossover region in phenol- and cresol-phthalein-dimethylethers under different conditions of pressure and temperature  

Energy Technology Data Exchange (ETDEWEB)

Dielectric relaxation times over a broad range of temperature and pressure for the glass former phenolphthalein-dimethylether (PDE) reveal a change of dynamics at a characteristic relaxation time {tau}{sub B}. The value of {tau}{sub B} was found to be largely insensitive to the particular combination of pressure and temperature of the measurement. Data for a second glass former, cresol-phthalein-dimethylether, having a molecular structure very close to that of PDE, were also analysed. In this case, {tau}{sub B} is much smaller, so the change of dynamics could not be observed in the elevated pressure experiments. The PDE data were in good agreement with the Adam-Gibbs model near T{sub g} ({tau} > {tau}{sub B}), while deviating for {tau} < {tau}{sub B}. Finally, a possible connection between the observed T{sub B} and theoretical models is presented.

Casalini, Riccardo [Naval Research Laboratory, Chemistry Division, Code 6120, Washington, DC 20375-5342 (United States); Paluch, Marian [Naval Research Laboratory, Chemistry Division, Code 6120, Washington, DC 20375-5342 (United States); Roland, C Michael [Naval Research Laboratory, Chemistry Division, Code 6120, Washington, DC 20375-5342 (United States)

2003-03-26

352

The dynamics crossover region in phenol- and cresol-phthalein-dimethylethers under different conditions of pressure and temperature  

International Nuclear Information System (INIS)

Dielectric relaxation times over a broad range of temperature and pressure for the glass former phenolphthalein-dimethylether (PDE) reveal a change of dynamics at a characteristic relaxation time ?B. The value of ?B was found to be largely insensitive to the particular combination of pressure and temperature of the measurement. Data for a second glass former, cresol-phthalein-dimethylether, having a molecular structure very close to that of PDE, were also analysed. In this case, ?B is much smaller, so the change of dynamics could not be observed in the elevated pressure experiments. The PDE data were in good agreement with the Adam-Gibbs model near Tg (? > ?B), while deviating for ? B. Finally, a possible connection between the observed TB and theoretical models is presented

2003-03-26

353

Pulsed laser ablation plasmas generated in CO{sub 2} under high-pressure conditions up to supercritical fluid  

Energy Technology Data Exchange (ETDEWEB)

Pulsed laser ablation of solids in supercritical media has a large potential for nanomaterials fabrication. We investigated plasmas generated by pulsed laser ablation of Ni targets in CO{sub 2} at pressures ranging from 0.1 to 16 MPa at 304.5 K. Plasma species were characterized by optical emission spectroscopy, and the evolution of cavitation bubbles and shockwaves were observed by time-resolved shadowgraph imaging. Ni and O atomic emissions decreased with increasing gas pressure; however, near the critical point the intensities reached local maxima, probably due to the enhancement of the plasma excitation and effective quenching resulting from the large density fluctuation.

Kato, Toru; Stauss, Sven; Kato, Satoshi; Urabe, Keiichiro; Terashima, Kazuo [Department of Advanced Materials Science, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Baba, Motoyoshi; Suemoto, Tohru [Division of Advanced Spectroscopy, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

2012-11-26

354

High-temperature phase transitions in CsH2PO4 under ambient and high-pressure conditions: a synchrotron x-ray diffraction study.  

Science.gov (United States)

To clarify the microscopic origin of the temperature-induced three-order-of-magnitude jump in the proton conductivity of CsH(2)PO(4) (superprotonic behavior), we have investigated its crystal structure modifications within the 25-300 degrees C temperature range under both ambient- and high-pressure conditions using synchrotron x-ray diffraction. Our high-pressure data show no indication of the thermal decomposition/polymerization at the crystal surface recently proposed as the origin of the enhanced proton conductivity [Phys. Rev. B 69, 054104 (2004)]. Instead, we found direct evidence that the superprotonic behavior of the title material is associated with a polymorphic structural transition to a high-temperature cubic phase. Our results are in excellent agreement with previous high-pressure ac impedance measurements. PMID:18035892

Botez, Cristian E; Hermosillo, Juan D; Zhang, Jianzhong; Qian, Jiang; Zhao, Yusheng; Majzlan, Juraj; Chianelli, Russell R; Pantea, Cristian

2007-11-21

355

High-Temperature Phase Transitions in CsH2PO4 Under Ambient and High-Pressure Conditions: A Synchrotron X-ray Diffraction Study  

Energy Technology Data Exchange (ETDEWEB)

To clarify the microscopic origin of the temperature-induced three-order-of-magnitude jump in the proton conductivity of CsH2PO4 (superprotonic behavior), we have investigated its crystal structure modifications within the 25-300 C temperature range under both ambient- and high-pressure conditions using synchrotron x-ray diffraction. Our high-pressure data show no indication of the thermal decomposition/polymerization at the crystal surface recently proposed as the origin of the enhanced proton conductivity. Instead, we found direct evidence that the superprotonic behavior of the title material is associated with a polymorphic structural transition to a high-temperature cubic phase. Our results are in excellent agreement with previous high-pressure ac impedance measurements.

Botez,C.; Hermosillo, J.; Zhang, J.; Qian, J.; Zhao, Y.; Majzlan, J.; Chianelli, R.; Pantea, C.

2007-01-01

356

Measurement of the constant-pressure heat capacity of water-oxygen mixtures at near-critical conditions  

Energy Technology Data Exchange (ETDEWEB)

Pilot scale studies were conducted at the UBC-NORAM Supercritical Water Oxidation (SCWO) facility to obtain heat capacity measurements of water-oxygen mixtures. This pilot plant is capable of processing aqueous waste at a rate of 1 to 2 L/minute. SCWO is a method for destroying very toxic water-borne organic wastes. The impetus of this study was to try to better establish the thermodynamics of the mixtures found in SCWO since the technology is only in its early commercial phase and the engineering and modeling of such systems has not yet been refined. Distilled water, pressurized with a triplex plunger pump was used in these experiments. The water flow was measured by graduated cylinder stopwatch at the system outlet for a cold, pressurized system without oxygen. Experiments were conducted at pressures between 23.9 and 26.1 MPa and at temperatures from 320 to 430 degrees C. Oxygen flow was between 2 and 5 wt. per cent of the total mixture. Results showed that the oxygen addition created a significant lowering of the temperature at which the maximum heat capacity occurs. It also created a reduction in the magnitude of the maximum constant-pressure heat capacity. 8 refs., 1 tab., 5 figs.

Rogak, S.N. [British Columbia Univ., Vancouver, BC (Canada)

2000-07-01

357

Macroscopic electric field and osmotic pressure in ultracentrifugal sedimentation diffusion equilibria of charged colloids  

Science.gov (United States)

Sedimentation-diffusion (SD) equilibria from analytical ultracentrifugation of well-characterized charged silica spheres in ethanol deviate strongly from a barometric profile and demonstrate the existence and substantial effects of a recently predicted internal macroscopic electric field (van Roij 2003 J. Phys.: Condens. Matter 15 S3569). Experimental SD-profiles yield the gradient of the electrostatic potential energy of the colloids, which clearly manifests an almost homogeneous macroscopic electric field. Electrochemical Donnan potential measurements confirm a difference in electrical potential between the top and bottom of the profiles. A 'non-barometric' limiting law derived from electroneutrality explains the trends in the SD-profiles quite well. Our analysis of osmotic pressures (obtained from integrating SD-profiles) beyond this simple law includes, among other things, colloid-ion attractions and extra volume terms in the free energy.

Rasa, M.; Erné, B. H.; Zoetekouw, B.; van Roij, R.; Philipse, A. P.

2005-04-01

358

Macroscopic electric field and osmotic pressure in ultracentrifugal sedimentation-diffusion equilibria of charged colloids  

International Nuclear Information System (INIS)

Sedimentation-diffusion (SD) equilibria from analytical ultracentrifugation of well-characterized charged silica spheres in ethanol deviate strongly from a barometric profile and demonstrate the existence and substantial effects of a recently predicted internal macroscopic electric field (van Roij 2003 J. Phys.: Condens. Matter 15 S3569). Experimental SD-profiles yield the gradient of the electrostatic potential energy of the colloids, which clearly manifests an almost homogeneous macroscopic electric field. Electrochemical Donnan potential measurements confirm a difference in electrical potential between the top and bottom of the profiles. A 'non-barometric' limiting law derived from electroneutrality explains the trends in the SD-profiles quite well. Our analysis of osmotic pressures (obtained from integrating SD-profiles) beyond this simple law includes, among other things, colloid-ion attractions and extra volume terms in the free energy

2005-04-20

359

Microbial Survival Rates of Escherichia coli and Deinococcus radiodurans Under Low Temperature, Low Pressure, and UV-Irradiation Conditions, and Their Relevance to Possible Martian Life  

Science.gov (United States)

Viability rates were determined for microbial populations of Escherichia coli and Deinococcus radiodurans under the environmental stresses of low temperature (-35°C), low-pressure conditions (83.3 kPa), and ultraviolet (UV) irradiation (37 W/m2). During the stress tests the organisms were suspended in saltwater soil and freshwater soil media, at variable burial depths, and in seawater. Microbial populations of both organisms were most susceptible to dehydration stress associated with low-pressure conditions, and to UV irradiation. However, suspension in a liquid water medium and burial at larger depths (5 cm) improved survival rates markedly. Our results indicate that planetary surfaces that possess little to no atmosphere and have low water availability do not constitute a favorable environment for terrestrial microorganisms.

Diaz, Benjamin; Schulze-Makuch, Dirk

2006-04-01

360

Development of a CATHENA Fuel Channel Analysis Model for a Fuel Channel with Axial Variation of Radial Pressure Tube Creep in a Stratified Two-Phase Flow Condition  

International Nuclear Information System (INIS)

A two-phase heat transfer phenomena in the fuel bundle strings located in a horizontal pressure tube with an axial variation of the radial creep, especially under a low stratified two-phase flow condition such as encountered in the CANDU reactor under the later stage of the blowdown phase of a LBLOCA, involves a complex heat transfer nature. This includes the conduction in the fuel rods, pressure tube, convection in the vapor and liquid regions, and radiation between the fuel rods exposed in the steam and the pressure tube, pressure tube and calandria tube. As these three modes of heat transfer has to be treated in a combined way, modeling the heat transfer phenomena inside the fuel bundle under the stratified flow during the later stage of LBLOCA blowdown has been one of the most challenging tasks in the CANDU safety analyses. The main reason for this hot attention is that it closely related to the integrity of the pressure tube. In this study a heat transfer model for handling this situation is developed, implemented and under preliminary testing of the analysis results. The analysis result up to now is encouraging and the validation of the model developed is ongoing. The major motivation of