Low Pressure Vessel Research Articles

Correlating Irradiation-Induced Solute Clustering with Changes of Hardness in Low and High Flux Reactor Pressure Vessel Steels

Correlating Irradiation-Induced Solute Clustering with Changes of Hardness in Low and High Flux Reactor Pressure Vessel Steels

Coronary artery fi stulas in children: Experience from a Southern African tertiary care centre complex

Coronary artery fi stulas (CAF) are unusual coronary artery connections with low pressure cardiac chambers or vessels. The majority are congenital, but can also be acquired. Complications include heart failure, myocardial infarction and arrhythmias. Symptomatic and large CAF require treatment and options include surgical ligation or percutaneous device embolisation of the fi stula which has emerged as a less invasive and equally effi cacious management modality. Careful interrogation of the CAF is required prior to occlusion in order not to compromise normal coronary artery vasculature that may arise from the fi stula which can lead to myocardial ischaemia and infarction. Several reported cases highlight thrombus formation within large CAF after surgical ligation with propagation of the thrombus into coronary vessels arising proximally, resulting in myocardial compromise. We present a series of 6 children with CAF, 2 were treated by percutaneous embolisation (one developed a myocardial infarction post procedure) and 3 were treated surgically.

J0540203 熱誘導流れを利用したポンプシステム

In this study, the performance of Knudsen pump which works by the use of thermal induced flow was studied experimentally. The driven force of the pump system presented in this study is thermal edge flow around laminated plates which one surface is black and the other is white. The thermal induced flow is generated by irradiating the infrared lamp to the laminated plates. The system was placed in a glass pipe which was connected to two vessels and irradiated by infrared. It was observed that the pressure ratio of the high pressure vessel and low pressure vessel was about 96% when the temperature difference between the black and white surfaces of the plates were about 40 degrees in the centigrade scale.

Spectroscopic Characteristics of Supersonically Expanding Nitrogen Arc-Jet Plume—Strong Atomic Lines and Weak Molecular Band Spectra

We generate recombining nitrogen plasma plume by expansion of nitrogen arc into lower pressure vessel with a weak longitudinal magnetic field in a steady state. Spectroscopic observation reveals that the plasma has almost no component of molecular band spectra. Meanwhile, atomic nitrogen lines are observed with considerable intensity. The reason for this spectroscopic peculiarity is discussed in terms of chemical thermodynamics of the nitrogen thermal arc plasma and of nonequilibrium characteristics.

Spectroscopic study of recombination continuum in arc-heated cold expanding plasma jet

Cold recombining H2–He mixture plasma and pure He plasma with low electron density are generated by arc discharge followed by expansion into a lower-pressure vessel, and their recombination radiation is analyzed by optical emission spectroscopic measurement. Their electron temperature is determined from the continuum spectra, which is found to agree with those determined from the line intensities of LTE levels within 10% accuracy. Meanwhile, the agreement of electron density is found to be about 20–25%. It is experimentally found that the conventional theory of spectral intensity of the recombination continuum explains the observed continuum spectra very well even for very low electron temperature within the range from 0.07 to 0.2 eV.

Conceptual design of a helium heater for high temperature applications

The Karlsruhe Advanced Technologies Helium Loop (KATHELO) has been designed for testing divertor modules as well as qualifying materials for high heat flux, high temperature (up to 800°C) and high pressure (10MPa) applications. The test section inlet temperature level is controlled using a process electrical heater. To cope with the extreme operating conditions, a special design of this unit has been proposed. In this paper the conceptual design of the unit will be presented and the impact of the coupling between the cold and hot helium gas on the overall efficiency of the loop will be investigated. The detailed thermal-hydraulic analysis of the feed through of the hot helium into the low temperature pressure vessel using ANSYS CFX will be presented. The impact of the design choices on the overall energy budget of the loop will be analyzed using RELAP5-3D.

Cavity Ring-Down Spectroscopy Measurement of H(n=2) Density in Mesoplasma for Fast-Rate Silicon Epitaxy

The absolute density of the first excited state atomic hydrogen H(n=2) in an Ar/H2 mixture is measured in-situ by cavity ring-down spectroscopy under mesoplasma condition. The H(n=2) atom density is determined to be in the range of 1010–1011 cm-3 and the formation of H(n=2) having such high density is identified to be predominantly due to the associative charge exchange/dissociative recombination reactions, similar to dc-arc plasma expanding into a low-pressure vessel that have been previously reported. The local H(n=2) atom density is found to have a linear variation with deposition rate, which indicates that high H(n=2) atom density have a direct role in the reduction of SiHCl3 to Si.

Design of Civil Low-Pressure Vessel’s "4 in 1" Stamping Compound Dies

Traditional stamping process of civil low-pressure vessel deals with blanking, drawing, trimming and flaring process in different processing station separately, work-piece transmission between different processing stations increases the auxiliary time, and the work-piece needs reinstallation, reduce production efficiency and increase production cost. In order to overcome the above disadvantages, the optimized stamping technology process is designed, compress four process (blanking、drawing、trimming and flaring) into a integrity process, and the development of a "4 in 1" stamping compound dies, that makes stamping automation realize easily, improve processing efficiency, easy operation, and reduce the product processing cost and labor costs, and enhance economic performance.

On the Cu precipitation behavior in thermo-mechanically embrittlement processed low copper reactor pressure vessel model steel

Cu precipitation behavior in 30% pre-deformed reactor pressure vessel model steel has been investigated during thermal ageing. In this work, a thermo-mechanical treatment based embrittlement process, including high temperature quenching, pre-deformation and thermal ageing, has been applied to a low-Cu (0.17wt.%) RPV model steel to produce Cu-rich precipitates. Ultrafine Cu-rich precipitates were observed by transmission electron microscope (TEM) and energy dispersive X-ray microanalysis following this embrittlement process. Moreover, differential scanning calorimetry was used to study the structure transformation of Cu precipitates during long-term thermal ageing. It is noted that for dilute Cu containing steel, high temperature quenching and pre-deformation was found to promote the production of high density of vacancies in calculation, which may facilitate the formation of the fine Cu-rich precipitation. As a result, it leads to a significant hardness peak in the initial stage of thermal ageing. The results were discussed to link with the thermo-mechanical embrittlement process, which provides a method for studying the Cu-rich precipitates formation mechanism in steels containing less concentration of impurity Cu.

Fatigue Modeling of a Notched Flat Plate Under Variable Amplitude Loading Supported by Elastoplastic Finite Element Method Analyses

Although intensive research has been carried out to understand the fatigue behavior of steel notched components, under variable amplitude loading, no definite and general robust models have been derived so far. Therefore, every effort to augment the knowledge in this topic is welcomed. Within this context, existing variable amplitude data, derived by the authors for a notched low carbon pressure vessel steel (P355NL1) flat plate, is used to assess a local approach to fatigue. A linear damage summation framework, supported by elastoplastic finite element analyses, is used. Several variable amplitude loadings were selected and analyzed, using alternative configurations of kinematic hardening plasticity models (e.g., Chaboche’s model with distinct constants superposition). The predictions are assessed using available experimental data and data derived with simplified empirical elastoplastic tools. This paper highlights the difficulties of performing such elastoplastic analysis and compares the obtained results with those obtained using more classical tools for elastoplastic analysis (Glinka and Seeger–Heuler). It was found that fatigue predictions based on an elastoplastic finite element analysis, made using the Chaboche’s model, were significantly more accurate than predictions based on simplified elastoplastic analysis. These results have important practical relevance.

Fatigue modeling of a notched geometry under spectrum block loading supported on elastoplastic FEA

Despite intensive research has been carried out to understand the fatigue behaviour of steel notched geometries, under variable amplitude loading, no definite and general robust models have been derived so far. Therefore, any effort to increment the knowledge in the topic is welcome. Within this premise, it is proposed an assessment of existing variable amplitude data (spectrum block loading), which has been derived by authors for a notched geometry, made from a low carbon pressure vessel steel (P355NL1), within the local approaches and linear damage summation framework, and supported by elastoplastic finite element analyses. Several blocks are analyzed using elastoplastic finite element analysis with Mises plasticity theory and Chaboche's nonlinear kinematic hardening. The predictions are assessed using available experimental fatigue data as well as with predictions made with simplified elastoplastic analyses. This paper highlights the difficulties on performing the elastoplastic analysis and compares the obtained results with those obtained using simplified classical tools for elastoplastic analysis. Fatigue predictions based on elastoplastic analysis made using the Chaboche's model with four parameters were more accurate than predictions based on simplified elastoplastic analysis.

Graphitization in Low Alloy Steel Pressure Vessels and Piping

This article discusses the problem of graphitization that can occur in carbon steels exposed to high temperature for extended time when these are present in pressure vessels and piping. Several case studies are described dealing with actual failures that have been investigated by the authors.

Atom Probe Tomography characterization of the microstructural evolution of a low copper reactor pressure vessel steel under neutron irradiation

AbstractA low copper reactor pressure vessel steel was characterised by atom probe tomography after neutron irradiation at different fluences. The specimens were irradiated within the frame of the Surveillance Program of a production reactor. Roughly spherical clusters enriched in nickel, manganese, silicon and, in a lesser extent, phosphorus and copper were observed at all fluences. The chemical composition of these clusters shows no evolution with fluence, as well as their diameter, close to 3 nm. Their number density increases linearly with the neutron fluence. A continuous segregation of the elements found in the clusters is also observed along dislocation lines, with similar enrichments.

Debottlenecking and Computational-Fluid-Dynamics Studies of High-and Low-Pressure Production Separators

Summary Efficient and effective oil/water/gas separation is required for success of many production operations. A major oil producer was experiencing difficulties with the oil/water/gas separation equipment on an offshore platform and improvements were required to meet both present and future production rates. Both high-pressure (HP) and low-pressure (LP) separators on a major oil production platform were studied to determine the design limitations for foamy service and basic sediment and water (BS&W) levels. Computational-fluid-dynamics (CFD) studies were completed to show the volumetric utilization and flow-pattern improvements made with the design changes. Both HP and LP separators showed substantial foam and poor efficiency because of poor inlet-device design, plugging, and other general vessel-design limitations. Debottlenecking efforts determined that, while the inlet device was somewhat ineffective, major improvements could be made from changes to perforated plate baffles, fluid-level adjustments, and weir placement and operations. CFD calculations performed on both vessels indicated similar problems. The perforated plate baffles with improper design lead to countercurrent flow through the baffles, making them less effective in flow control and distribution. Fluid-level settings for the weir height affected the velocity differences between fluid layers and contributed to promotion of recirculation within the vessel, which lead to low volumetric utilization. With adjustments to vessel internal equipment and changes to fluid-phase levels, CFD calculations showed that overall vessel volumetric utilization was improved by 22% for the HP vessel and by 38% for the LP vessel. CFD results also showed the changes to the flow patterns accompanying these improvements. Vessels with the proposed changes were operating effectively with substantially higher throughputs and meeting the expected BS&W levels for operations of the downstream oil-processing equipment. Details about the vessel internals, flow properties, and other changes required to accomplish these improvements will be discussed.

Abstract 4902: Renal Sinus Fat Influences the Number of Medications Needed to Regulate Blood Pressure in Patients With Hypertension

Introduction: A potential consequence of increasing intraperitoneal (IP) fat is the accumulation of fat in the renal sinus (RS). Compression of low pressure vessels (renal veins, lymphatics), by RS fat may result in activation of the renin-angiotensin system (RAS) and promote more extensive use of antihypertensive therapy. Hypothesis: RS fat would be associated with IP fat and number of medications for blood pressure control. Methods: Two hundred five participants aged 55 to 85 years, without renal artery stenosis, underwent magnetic resonance imaging measures of RS and abdominal fat (subcutaneous + IP + retroperitoneal). Data were analyzed for possible associations of RS fat with renal function, BP, and the number of prescribed antihypertensives. Results: Age averaged 69 ± 9 years; 50% were women. RS fat averaged 5 ± 3 cm 3 (up to 16 cm3). RS fat correlated with retroperitoneal and IP fat volumes, and cardiac risk factors (hypertension, diabetes, and coronary artery disease) (r = 0.49, 0.42, and r = 0.18, p = 0.001, 0.001, and 0.009 respectively); it did not correlate with subcutaneous fat (r = −0.08, p = 0.23). RS fat also showed a positive association with number of antihypertensive medications, renal size, creatinine, pulse pressure, and an inverse correlation with serum potassium, a marker of RAS activation (r = 0.21, 0.44, 0.23, 0.13, and 0.16; r = −0.18, p = 0.01) [Table ]. These associations of RS fat persisted after adjustment for age, gender, height, diabetes, coronary artery disease, serum lipids, and IP fat (p = 0.01 for all). Importantly, after adjusting IP fat to RS fat in our regression model, RS fat remained associated with the number of prescribed anti-hypertensive medications ( B = 0.27, p = 0.01), while IP fat did not. Conclusions: Higher volumes of renal sinus fat are associated with indirect evidence of the activation of the RAS and the number of medications used to treat hypertension. These data suggest a possible mechanism for central obesity to promote hypertension. Table: Correlations of different variables using renal sinus fat as a dependant variable

Using acoustic emission and fractography to evaluate defects induced by corrosive environment

Acoustic emission (AE) is now a well established technique for damage detection, quantification and location in large structures. It appears in its principle as a technique providing real time information about the origins and the importance of the degradation mechanisms inside the material. This paper demonstrates the use of AE technique to monitor the structural damage using data obtained from a phenomenological study of hydrogen induced cracking of a low alloy steel pressure vessel. In addition to the feature extraction, correlation and clustering procedures applied to the AE signals, data were studied in time and frequency domain to characterise and to find out the relation between AE parameter and damage sources. Moreover, the characterisation of the corrosive mechanisms using the optical microscopy as well as the scanning electron microscopy was carried out. These identified corrosive mechanisms and the sources of generated AE signals were discussed.

Modeling and experiments on differential pumping in linear plasma generators operating at high gas flows

The direct simulation Monte Carlo (DSMC) method was used to investigate the efficiency of differential pumping in linear plasma generators operating at high gas flows. Skimmers are used to separate the neutrals from the plasma beam, which is guided from the source to the target by a strong axial magnetic field. In this way, the neutrals are prevented to reach the target region. The neutral flux to the target must be lower than the plasma flux to enable ITER relevant plasma-surface interaction (PSI) studies. It is therefore essential to control the neutral gas dynamics. The DSMC method was used to model the expansion of a hot gas in a low pressure vessel where a small discrepancy in shock position was found between the simulations and a well-established empirical formula. Two stage differential pumping was modeled and applied in the linear plasma devices Pilot-PSI and PLEXIS. In Pilot-PSI a factor of 4.5 pressure reduction for H2 has been demonstrated. Both simulations and experiments showed that the optimum skimmer position depends on the position of the shock and therefore shifts for different gas parameters. The shape of the skimmer has to be designed such that it has a minimum impact on the shock structure. A too large angle between the skimmer and the forward direction of the gas flow leads to an influence on the expansion structure. A pressure increase in front of the skimmer is formed and the flow of the plasma beam becomes obstructed. It has been shown that a skimmer with an angle around 53° gives the best performance. The use of skimmers is implemented in the design of the large linear plasma generator Magnum-PSI. Here, a three stage differentially pumped vacuum system is used to reach low enough neutral pressures near the target, opening a door to PSI research in the ITER relevant regime.

The cardiovascular phenotype of a mouse model of acromegaly

Background Although, it is accepted that there is an excess of cardiovascular mortality in acromegaly, it is uncertain whether this is due to the direct effects of growth hormone-induced-cardiomyopathy or is a consequence of atherosclerosis secondary to the metabolic syndrome often observed in this condition. Direct comparison of a mouse model of acromegaly to a mouse model of Laron’s syndrome allowed us to carry out detailed phenotyping and better understand the role GH plays in the circulatory system. Methods and results Transgenic mice that overexpress the growth hormone gene (GH) developed gigantism, including insulin resistance and higher blood pressures commensurate with increased body mass. In these giant mice, the hearts were hypertrophied but haemodynamic studies suggested contractile function was normal. Segments of small arteries mounted in a pressure myograph showed vascular wall hypertrophy but a preserved lumen diameter. Vascular contractile function was normal. Mice in which the GH receptor gene was disrupted or ‘knocked out’ were dwarf and had low blood pressure, small hearts and blood vessels but a normally functioning circulation. Correlations of body mass with cardiovascular parameters suggested that blood pressure and structural characteristics develop in line with body size. Conclusion In this transgenic mouse model of acromegaly, there is cardiac and vascular hypertrophy commensurate with GH excess but normal function. Our findings support the contention that the excess mortality in this condition may be due to the development of hypertrophic cardiomyopathy rather than increased rates of atherosclerotic coronary artery disease.

The evaluation of RCS depressurization to prevent core melting in pressure tube reactors (CANDU-type)

Pressure tube reactors, especially of the CANDU-type, have a low-pressure vessel calandria – under an internal pressure near atmospheric. The calandria vessel is immersed into the water contained inside a concrete structure – the calandria vault. In the case of accidents with the loss of normal core heat sinks, the moderator inside the calandria (heavy water) could become the ultimate heat sink. Accident analysis using a newly developed model (ASQR) strengthens the importance of the inside cooling of the fuel channels in order to prevent severe accidents. Even if implementing those methods related to moderator for eliminating the impairment of the outside cooling of fuel channels, these are not sufficient. The new model has been compared against the well-known in-reactor LOCA experiment – PBF – NRU. Thus, the paper makes a review of author’s article [Mehedinteanu, S., 2001. An application of the new way to prevent core melting in pressure tube reactors (CANDU-type). Annals of Nuclear Energy 28, 79–88] and describes a new method to prevent the core melting in the pressure tube reactors. The method concerns the use of a safety depressurization of the pressurizer (PDS) by means of a new safety valve block located on the line to the degasser-condenser (DC) and subsequent “re-pumping” of the water as collected in the DC, by the pressure difference intrinsically created, back to RCS through new lines connected with the emergency core cooling system (ECCS) lines. The result of the calculation shows a full prevention of the core melting in the pressure tube reactor (CANDU-type) and this conclusion could also be extended to LWR.

A new technique for prosthetic reconstruction of the superior vena cava

CASTLE seem to have a better prognosis. However, CASTLE has a potentially invasive behavior, and invasion of neighboring cervical structures is possible. In particular, tracheal or laryngotracheal resections have been necessary to excise the lesion. The extent of this invasion may sometimes prevent a complete resection or require surgically challenging procedures, as in our experience. The parietal invasion can involve the muscles, connective tissue, and skin. Nodal involvement is probably a negative prognostic factor, because it has been associated with the occurrence of locoregional or systemic spread. Adjuvant radiotherapy is generally advocated in case of nodal metastasis. On the other hand, local recurrence is possible in the absence of nodal disease, thus suggesting a role for systematic adjuvant radiotherapy because of the radiosensitivity of this tumor.