• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.127-132
• /
• 2001

An experimental study on penetration integrity of the reactor vessel has been performed under external vessel cooling during a core melt accident. In this study a series of experiments are performed for the verification of the effects of coolant in the annulus between the ICI(In-Core Instrumentation) nozzle and the thimble tube and also the effects of external vessel cooling on the integrity of the penetration using the test section including only one penetration and $Al_{2}O_{3}$ melt as a corium simulant. The experimental results have shown that penetration is more damaged in the case of no external vessel cooling compared with the case of external vessel cooling. It is preliminarily concluded that the external vessel cooling is very effective measure for the improvement of the penetration integrity. Also it is confirmed from the experimental results that the coolant in the annulus reduces the melt penetration distance through the annulus and enhance the integrity of the reactor vessel penetration in the end.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.35 no.5
• /
• pp.17-25
• /
• 2003

The influence of base paper properties and fiber type on coating penetration was studied in terms of characterization of coating holdout using two types of hand sheets as the base paper which were prepared from thermomechanical pulp (TMP) and hardwood bleached kraft pulp(KP) sized internally with alkyl ketene dimmer (AKD). Laboratory rod draw down coater was used for surface sizing and coating application. Characterization of coating penetration was done by measuring the roughness of the backside of coating layer. The backside of the coating was exposed by dissolving the fibers in a solution of cupriethylenedimine (CEO). Data show that internal sizing of base paper is effective and surface sizing is more effective to prevent coating penetration. Comparing between the two types of base papers, backside roughness of coating layer of TMP sheet is much larger and sizing is more effective to reduce coating penetration than those of KP sheet. From the result of water absorption and sizing degree after surface sizing, it seems that internal sizing slows down molecular diffusion much more than capillary penetration, but surface sizing reduces the capillary penetration. Furthermore, predominant mechanism of water into paper of TMP sheet seems to be capillary penetration, but it is molecular diffusion in the case of KP sheet.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.10 no.1
• /
• pp.15-19
• /
• 2014

A Failure or degradation of reactor upper head penetration is a recurring problem due to long term operation at nuclear power plants. And a flaw in the reactor upper head penetration has caused unplanned plant shutdown for repair as well as high economic impact on the plants. Consequently, a detection of flaws is of the utmost importance. Prior to the replacement of reactor upper head penetration, some utilities have repaired the flaws of reactor upper head penetration generated by overlay weld. Until now, only the base metal in reactor upper head penetration has been inspected according to 10 CFR 50.55a and ASME code case N-729-1. Accordingly, it is difficult to detect manufacturing defects and repair defects in overlay weld. This paper presents a case study on the application of Time of Flight Diffraction technique for reactor head penetration mockup with artificial flaws in overlay weld. This study offers a way to understand the flaws detected in reactor upper head penetration overlay weld.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.401-404
• /
• 2008

Crack is a penetration path of harmful material such as chloride ion, and causes a serious deterioration in durability. So, the characteristics of chloride penetration are investigated for the cracked flexural concrete members using high-durable materials. For these, the flexural crack of beam specimen is introduced by transverse loading. And, Rapid Chloride Penetration Test (RCPT) and Long-term chloride penetration test are carried out to compare the chloride penetration depth. From test results when crack is happened, the chloride penetration resistance of the durable member was superior than that of the normal member. Blast furnace slag concrete member has a excellent chloride penetration resistance in long-term chloride penetration test.

• Laser Solutions
• /
• v.5 no.1
• /
• pp.33-42
• /
• 2002

In order to investigate the characteristics of the plasma induced by lap-joint CO$_2$ laser welding of automotive steel sheets, the effects of welding speed, shield gas flow rate, gap size, and laser beam defocus to plasma intensity emitted from keyhole have been investigated. The plasma light is measured by fiber and photodiode. Also, the plasma images were captured by the high speed digital camera in 1000frames/sec in order to correlate the plasma light signal with plasma pattern. From the results, it is observed that the difference of the plasma intensity for between the deep penetration and partial penetration exists from 1.2 to 2 times. The plasma light intensity decreased in case of the deep penetration Is observed due to the exhausting of the plasma gas under the sheet. On the other hand, under the conditions of the deep penetration, the plasma intensity is significantly increased by controling the conditions decreasing the penetration depth. It was specially founded that the effect of 0.3mm gap size at partial penetration condition is approximately similar to deep penetration in 0mm gap. It is concluded that the plasma intensity is able to evaluate the penetration depth in lap-joint welding and appears to offer the most straightforward correlation to the welding process.

• Journal of Electrical Engineering and Technology
• /
• v.7 no.6
• /
• pp.852-858
• /
• 2012

This paper describes evaluation results of the wind power penetration limit (WPPL) and the wind energy penetration (WEP) in the Mongolian central power system (MCPS). A wind power plant (WPP) in a power system possesses an output power limit because the power system must maintain a balance between the generation and consumption of electricity at all times in order to achieve an adequate level of quality. The instantaneous penetration limit (IPL) of wind generation at a load is determined as the minimum of the three technical constraints: the minimum output, the ramp rate capability, and the spinning reserve of the conventional generating units. In this paper, a WPPL is defined as the maximum IPL divided by the peak load. A maximal variation rate (VR) of wind power is a major factor in determining the IPL, WPPL, and WEP. This paper analyzes the effects of the maximal VR of wind power on the WPPL, WEP, and capacity factor (CF) in the MCPS. The results indicate that a small VR can facilitate a large amount of wind energy while maintaining a high CF with increased wind power penetration.

• Restorative Dentistry and Endodontics
• /
• v.40 no.2
• /
• pp.143-148
• /
• 2015

Objectives: This study evaluated the maximum depth and percentage of irrigant penetration into dentinal tubules by passive ultrasonic irrigation (PUI). Materials and Methods: Thirty extracted human teeth were instrumented and divided into three groups. According to final irrigation regimen, 5.25% sodium hypochlorite (Group A, NaOCl), 2% chlorhexidine (Group B, CHX) and saline solution (Group C, control group) were applied with Irrisafe 20 tips (Acteon) and PUI. Irrigant was mixed with 0.1% rhodamine B. Sections at 2 mm, 5 mm, and 8 mm from the apex were examined with confocal laser scanning microscopy (CLSM). The percentage and maximum depth of irrigant penetration were measured. Kruskal-Wallis test and Mann-Whitney test were performed for overall comparison between groups at each level and for pairwise comparison, respectively. Within a group, Wilcoxon test was performed among different levels. p values less than 0.05 were considered significant. Results: In all groups, highest penetration depth and percentage of penetration were observed at the 8 mm level. At 2 mm level, Groups A and B had significantly greater depths and percentages in penetration than Group C (p < 0.05), but there were no significant differences between Groups A and B. At 5 mm level, penetration depths and percentage of penetration was not significantly different among the groups. Conclusions: NaOCl and CHX applied by PUI showed similar depth and percentage of penetration at all evaluated levels.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.1
• /
• pp.55-62
• /
• 2010

Dynamic soil resistances were simulated by modified Ramberg-Osgood model in order to predict penetration rate of sheet pile installed by vibratory pile driver. Various factors which characterize modified Ramberg-Osgood model were determined considering the shapes of dynamic soil resistance curves obtained from field test and standard penetration value (N value) was used as parameter that relates field test results to the suggested model. Penetration rates calculated by analytical model were smaller than those of field test and penetration times were vice versa. Therefore, predicted penetration rate and penetration time by analytical model are more conservative than those of filed test.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.2
• /
• pp.164-171
• /
• 2005

This study aims to examine an effect of stacking sequence and curvature on the penetration characteristic of a composite laminated shell. For the purpose, we manufactured specimens with different stacking sequences and curvatures, and conducted a penetration test using an air-gun. To examine an influence according to stacking sequence, as flat plate and curvature specimen had more plies, their critical penetration energy was higher, Critical penetration energies of specimen A and C with less interfaces somewhat higher than those of B and D with more interfaces. The reason that with less interfaces, critical penetration energy was higher is pre-impact bending stiffness of composite laminated shell with less interfaces was lower than that of laminated shell with more interfaces, but bending stiffness after impact was higher. And it is because interface, the weakest part of the composite laminated shell, was influenced by transverse impact. As curvature increases, critical penetration energy increases linearly. It is because as curvature increases, resistance to in-plane deformation as well as bending deformation increases, which need higher critical penetration energy. Patterns of cracks caused by penetration of composite laminated shells include interlaminar crack, intralaminar crack, and laminar fracture. A 0$^{\circ}$ply laminar had a matrix crack, a 90$^{\circ}$ply laminar had intralaminar crack and laminar fracture, and interface between 0$^{\circ}$and 90$^{\circ}$laminar had a interlaminar crack. We examined crack length and delamination area through a penetration test. For the specimen A and C with 2 interface, the longest circumferential direction crack length and largest delamination area were observed on the first interface from the impact point. For the specimen B and D with 4 interface, the longest crack length and largest delamination area were observed on the third interface from the impact point.

• Smart Structures and Systems
• /
• v.18 no.2
• /
• pp.197-216
• /
• 2016

The increased speed of a train causes increased loads that act on the track substructures. To ensure the safety of the track substructures, proper maintenance and repair are necessary based on an accurate characterization of strength and stiffness. The objective of this study is to develop and apply a cone penetrometer incorporated with the dynamic cone penetration method (CPD) for investigating track substructures. The CPD consists of an outer rod for dynamic penetration in the ballast layer and an inner rod with load cells for static penetration in the subgrade. Additionally, an energy-monitoring module composed of strain gauges and an accelerometer is connected to the head of the outer rod to measure the dynamic responses during the dynamic penetration. Moreover, eight strain gauges are installed in the load cells for static penetration to measure the cone tip resistance and the friction resistance during static penetration. To investigate the applicability of the developed CPD, laboratory and field tests are performed. The results of the CPD tests, i.e., profiles of the corrected dynamic cone penetration index (CDI), profiles of the cone tip and friction resistances, and the friction ratio are obtained at high resolution. Moreover, the maximum shear modulus of the subgrade is estimated using the relationships between the static penetration resistances and the maximum shear modulus obtained from the laboratory tests. This study suggests that the CPD test may be a useful method for the characterization of track substructures.