Analysis of concrete ablation depth by MCCI assuming top flooding condition of APR1400 NPP

2021 ◽  
Vol 160 ◽  
pp. 108363
Author(s):  
Hanbee Na ◽  
Seongnyeon Lee ◽  
Han-Chul Kim ◽  
Kyun-Tae Kim
Keyword(s):  
Ablation Depth

scholarly journals Photorefractive keratectomy for correction of myopia: Our one-year experience

2012 ◽  
Vol 69 (10) ◽  
pp. 852-857
Author(s):  
Mirko Resan ◽  
Miroslav Vukosavljevic ◽  
Milorad Milivojevic
Keyword(s):  
Visual Acuity ◽  
Postoperative Complications ◽  
Intraoperative Complications ◽  
Mean Value ◽  
Ablation Depth ◽  
Laser In Situ Keratomileusis ◽  
Photorefractive Keratectomy ◽  
Corneal Tissue ◽  
Surgical Method ◽  
A Prospective Study

Background/Aim. Photorefractive keratectomy (PRK), after laser in situ keratomileusis (LASIK), is commonly performed refractive surgical method worldwide. The aim of this study was to examine the effectiveness and safety of PRK in correction of various strengths of myopia and to assess how much corneal tissue is being removed with one diopter sphere (Dsph) correction by using different optical zones (OZ). Methods. A prospective study with a follow-up period of 6 months included 55 patients of which 100 myopic eyes were treated by PRK method (one eye was included in 10 patients). Myopic eyes with a preoperative best corrected visual acuity (BCVA) = 1.0 (20/20) were analysed. In order to assess the effectiveness of PRK operated myopic eyes were divided into four groups according to the dioptric power: 1)? -1.75 Dsph (n = 26); 2) from -2 to -3.75 Dsph (n = 44); 3) from -4 to -6.75 Dsph (n = 23), and 4) ? -7 Dsph (n = 7). Myopic eyes with preoperative BCVA ? 0.9 (amblyopic eyes) were excluded from the study, as well as eyes with astigmatism > -1.5 Dcyl. To assess the effectiveness of PRK we examined the percentage of eyes in the mentioned groups, which derived uncorrected visual acuity (UCVA) 6 months after the intervention to the following: a) UCVA = 1.0 (20/20) and b) UCVA ? 0.5 (20/40). To assess the safety of PRK we examined the frequency of intraoperative and postoperative complications. To estimate how much corneal tissue was removed with one Dsph correction by using different OZ, we used preoperative and postoperative (after 6 months) central pachymetry values expressed in ?m and volume of cornea (central 7 mm) expressed in mm?. In that sense, we used only the myopic eyes with clear preoperative spherical refraction. The total number of these eyes was 27, of which 16 eyes were treated using a 6.5 mm OZ and 11 eyes using a 7 mm OZ. Results. Refractive spherical equivalent (RSE) for all eyes was in the range from -0.75 to -8.75 Dsph, and preoperative mean value of RSE with standard deviation (mean RSE ? SD) was -3.32 ? 1.83 Dsph. Six months after PRK, 91% of eyes had UCVA = 20/20, and 99% of eyes had UCVA ? 20/40. In the first group (? -1.75 Dsph) preoperative mean RSE ? SD was -1.34 ? 0.32 Dsph, six months after PRK, 96% of eyes had UCVA = 20/20, and 100% of eyes had UCVA ? 20/40. In the second group (from -2 to -3.75 Dsph) preoperative mean RSE ? SD was - 2.95 ? 0.57 Dsph, six months after PRK, 89% of eyes had UCVA = 20/20, and 100% of eyes had UCVA ? 20/40. In the third group (from -4 to -6.75 Dsph) preoperative mean RSE ? SD was - 4.93 ? 0.70 Dsph, six months after PRK, 100% of eyes had UCVA = 20/20. In the fourth group (? - 7 Dsph) preoperative mean RSE ? SD was -7.71 ? 0.67 Dsph, six months after PRK, 57% of eyes had UCVA = 20/20, and 86% of eyes had UCVA ? 20/40. There were no intraoperative complications while postoperative complications occurred in 2 patients - in both cases in one eye (2%). In that cases, epithelial defects were detected. In the group of eyes that were treated by 6.5 mm OZ mean RSE ? SD was -2.45 ? 0.99 Dsph, the ablation depth per 1 Dsph was 17.54 ? 5.58 ?m and ablated volume of central 7 mm cornea by 1 Dsph was 0.43 ? 0.18 mm?. In the group of eyes that were treated by 7 mm OZ mean RSE ? SD was -3.32 ? 2.26 Dsph, the ablation depth per 1 Dsph was 23.73 ? 6.91 ?m and ablated volume of central 7 mm cornea by 1 Dsph was 0.61 ? 0.31 mm?. Conclusion. PRK is effective and safe refractive surgical method for correcting myopia up to -8 .75 Dsph. OZ size is the main factor determining the depth of the excimer laser ablation of the corneal tissue volume consumed by 1 Dsph. Higher OZ value determines higher consumption of cornea tissue.

Study of Refractory Material Installation in the Reactor Cavity

2014 ◽  
Author(s):  
Young Tae Moon ◽  
In Chul Ryu ◽  
Quan Zhou ◽  
Paul McMinn ◽  
Chan Y. Paik
Keyword(s):  
Refractory Material ◽  
Protective Layer ◽  
Ablation Depth ◽  
Severe Accident ◽  
Refractory Materials ◽  
Protective Material ◽  
Concrete Material ◽  
Combustible Gases ◽  
Accident Conditions ◽  
Containment Pressure

During a severe accident with a vessel failure, corium relocates from the vessel into the reactor cavity (PWR) or pedestal (BWR) and accumulates on top of the cavity floor to form a corium pool. This corium pool is hot enough to cause a Molten Corium-Concrete Interaction (MCCI) that can ablate the concrete structure even if water is present on top of the corium. MCCI will also produce steam and other gases that increase containment pressure as well as generate combustible gases (Hydrogen and Carbon Monoxide). Current MAAP5* calculations with conservative assumptions have shown that the ablation depth in a basemat constructed of siliceous concrete can be larger than the depth of liner, even if the reactor cavity is flooded by water. To retain the melt in the containment and to cool the corium pool before the erosion reaches the liner plate, several approaches are being considered. One of these approaches is the installation of a protective layer on top of the concrete floor to retard MCCI. The purpose of this paper is to study the performance of different protective materials under postulated severe accident conditions. The candidates for the protective materials are refractory materials and limestone/limestone-common-sand (LCS) concrete. The refractory material was chosen based on the thermal performance and dissolution rate of the refractory material calculated by analytical calculations and also by MAAP5. Adding the refractory protective material protects the underlying concrete basemat from melting temporarily, so that water ingression into the surface of the corium is not initially affected by addition of the concrete material. *MAAP5 is an integrated severe accident code owned by the Electric Power Research Institute and developed by Fauske and Associates, LLC.

scholarly journals Modeling of pulsed laser ablation of aluminum under the action of infrared nanosecond laser pulses

2019 ◽  
Vol 196 ◽  
pp. 00020
Author(s):  
Nikolay Rubtsov ◽  
Victor Bessmeltsev ◽  
Maksim Grishin
Keyword(s):  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Laser Pulses ◽  
Ablation Depth ◽  
Aluminum Surface ◽  
Nanosecond Laser ◽  
Ablation Process ◽  
Nanosecond Pulses ◽  
Nanosecond Laser Pulses ◽  
Plasma Shielding

The paper presents the results of numerical simulation of aluminum ablation process that is caused by a series of incident nanosecond pulses on a wavelength λ=1064 nm. The mechanism of normal evaporation and the effect of plasma shielding were taken into account. As a result of mathematical modeling the ablation depth was obtained. It is shown that plasma shielding reduces the effectiveness of ablation process much more than cooling of the aluminum surface between pulses.

scholarly journals Anterior Chamber Angle and Volume Do Not Change after Myopic Laser-Assisted In Situ Keratomileusis in Young Patients

2018 ◽  
Vol 2018 ◽  
pp. 1-4
Author(s):  
Ertuğrul Tan Yassa ◽  
Cihan Ünlü
Keyword(s):  
Anterior Chamber ◽  
Anterior Segment ◽  
Young Patients ◽  
Anterior Chamber Depth ◽  
Ablation Depth ◽  
Anterior Chamber Angle ◽  
Chamber Volume ◽  
The Mean ◽  
Chamber Angle

Purpose. We aimed to investigate whether anterior chamber angle, depth, and volume change after myopic laser-assisted in situ keratomileusis (LASIK) in young patients. Methods. This retrospective study included 29 eyes of 29 patients (15 females and 14 males) between the ages of 18 and 39 years who underwent LASIK for the treatment of myopia. In addition to complete ophthalmic examination, anterior chamber angle (ACA), central anterior chamber depth (ACD), and anterior chamber volume (ACV) were measured by using a Sirius rotating Scheimpflug camera combined with Placido disc corneal topography (CSO, Florence, Italy). Preoperative and postoperative values were compared using paired t-tests. Linear regression was used to evaluate the relationship between changes in refraction and changes in ACA, ACD, and ACV as well as between attempted maximum ablation depth and changes in ACA, ACD, and ACV. Results. The mean age of the study population was 25.5 ± 6.2 years. The mean preoperative and postoperative spherical equivalent values were −3.30 ± 1.92 D and −0.18 ± 0.29 D, respectively. ACV and ACA were not significantly changed after surgery; however, central ACD was significantly decreased (preoperatively = 3.366 ± 0.316 mm vs postoperatively = 3.3 ± 0.298 mm) with a mean difference of 0.066 ± 1.121 mm. There were no significant relationships between changes in refraction and anterior segment dimensions or between attempted maximum ablation depth and anterior segment dimensions. Conclusion. Measurements with Sirius showed that ACA and ACV did not change; however, central ACD significantly decreased after myopic LASIK in young patients, indicating that the preoperative central ACD value should not be used interchangeably with the postoperative central ACD value.

Numerical Simulation Study on Truing and Dressing of Bronze-Bonded Diamond Wheel with Pulsed Laser

2007 ◽  
Vol 359-360 ◽  
pp. 166-170
Author(s):  
Gen Yu Chen ◽  
Li Fang Mei ◽  
Bi Zhang ◽  
Ding Jun Zhu ◽  
Guo Gui Chen
Keyword(s):  
Laser Ablation ◽  
Pulsed Laser ◽  
Diamond Wheel ◽  
Ablation Depth ◽  
Grinding Wheel ◽  
Ablation Process ◽  
Wheel Surface ◽  
Laser Ablation Process ◽  
Topographic Information ◽  
Single Process

A two-dimensional mathematical model is developed to simulate laser truing and dressing of bronze-bonded diamond grinding wheel. Based on the model, the ablation depth produced on bond and diamond abrasives by an acousto-optic Q-switched YAG pulsed laser under different parameters as well as the temperature field on grinding wheel surface produced in the laser ablation process are numerically simulated. An experimental study on laser truing and dressing of grinding wheel is also conducted. In the study, the wheel surface is ablated by the single-pulsed laser and measured with a measurement device for surface topographic information. Both the theoretical analysis and the experimental results indicate that the truing and dressing processes can be simultaneously realized with the laser ablation as a single process.

Fluid modeling of the laser ablation depth as a function of the pulse duration for conductors

2002 ◽  
Vol 66 (6) ◽  
Author(s):  
S. Laville ◽  
F. Vidal ◽  
T. W. Johnston ◽  
O. Barthélemy ◽  
M. Chaker ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Pulse Duration ◽  
Ablation Depth ◽  
Fluid Modeling

Modeling the Femtosecond Laser Pulse-Train Ablation of Dielectrics

2005 ◽  
Author(s):  
L. Jiang ◽  
H. L. Tsai
Keyword(s):  
Optical Properties ◽  
Laser Pulse ◽  
Femtosecond Laser ◽  
Pulse Train ◽  
Femtosecond Pulse ◽  
Laser System ◽  
Ablation Depth ◽  
Plasma Model ◽  
Depth Zone

Recently, a new laser micromachining technique using multiple femtosecond pulses with a picosecond-to-nanosecond separation as a train group has demonstrated the ability to increase the ablation quality of dielectrics and semiconductors. However, the mechanisms involved in the technique are not fully understood. This study employs the plasma model recently developed by the authors to analyze the femtosecond pulse-train ablation of dielectrics. It is found that the transient significantly varying optical properties are the important reasons that lead to the advantages of the pulse-train technique. It has demonstrated that there exits a constant ablation-depth zone with respect to fluence, which has also been observed experimentally. By using the pulse-train technology, it is possible to obtain repeatable nanostructures, even when the laser system is subject to some fluctuations in fluences.

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