• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.5
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• pp.553-562
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• 2012

Computational Fluid Dynamics (CFD) analysis has been performed to estimate the air temperature inside an Auxiliary Feed Water (AFW) Motor-Driven (MD) pump room for the case where there is loss of Heating, Ventilation, and Air-Conditioning (HVAC). A transient calculation for the closed pump room without cooling by any HVAC system shows that the volume-averaged air temperature reaches around $60^{\circ}C$ for a transient period of 8.0 h. From previous studies, the external air and surface boundary temperatures are assumed to increase slowly starting from an initial temperature of $35^{\circ}C$. For the cases where the door is opened at 2, 4, and 6 h after the initiation of HVAC failure, the average air temperature promptly drops by about $4^{\circ}C$ when the door is opened and then slowly increases. The current calculations based on the CFD technique predict the rate of increase of air temperature to be lower than that determined by previous conservative calculations on the basis of a lumped model.

• Restorative Dentistry and Endodontics
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• v.15 no.2
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• pp.46-57
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• 1990

The purpose of this study was to spectrophotometrically investigate the sealing effect of the ultrasonic canal obturation with softened gutta-percha utilizing an endosonic plugger by means of ultrasonic vibrations and heat. The 120 extracted human central and lateral incisors with single root were randomly selected, and the root canals were instrumented up to size #60 file by conventional method. The prepared canals were obtruated with gutta-percha by lateral condensation method, McSpadden technique and ultrasonic condensation method, with or without sealer. All specimens were immersed in 2% methylene blue in an incubator at $37^{\circ}C$ for 10 days. The teeth were then dissolved in 5ml of 60% nitric acid solution and the dye present within the root canal system was returned to solution. The leakage of dye was quantitatively measured via spectrophotometric method. The obtained data statistically evaluated usint two-way ANOVA and Student's t-test. The results were as follows : No statistically significant difference in leakage was observed between the lateral condensation method and ultrasonic condensation method, with and without sealer. When sealer was used or not, McSpadden technique showed significantly greater leakage than lateral or ultrasonic condensation method. Statistical analysis of the data indicated that the canals obturated in conjunction with sealer demonstrated less dye leakage than the canals obturated without sealer(p<0.01), except McSpadden technique. The ultrasonic condensation method appeared comparable sealing ability to the lateral condensation method.

• Restorative Dentistry and Endodontics
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• v.11 no.1
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• pp.77-88
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• 1985

The purpose of this study was to examine the thermal diffusion through bases and restorations. The three principle types of base and two restorative materials were included in this study. They were representive brands of a zinc phosphate cement, a zinc oxide-eugenol cement, a calcium hydroxide paste, an amalgam and a composite resin (table 1). The specimens were prepared by placing the bases or restorative materials in laminated plastic molds. 5-mm diameter holes were prepared in the center of square of plastics which were 0.5, 1.0, 2.0, and 3.0mm thick respectively (fig. 1). All materials were manipulated in accordance with manufacturer's recommended proportions. All experimental procedures were carried out dividing them into eight different groups (table 2). Thermal diffusion was measured by means of digital thermometer (DP-100, RKC. instrument Inc. JAPAN) with the surface thermocouple placed on bottom surface of the specimen applying a constant source of heat and cold to the top surface of the each specimen. The thermal stimulus temperature applied on the each specimen surface was in the range of $60^{\circ}C$, $0^{\circ}C$ and $-50^{\circ}C$ respectively. The thermal change were recorded automatically on the multi-Pen recorder (R-16, Rikadenki, Co. JAPAN) connected with thermocouple tips which were centered on the bottom of the specimen. The following results were as follows, 1. Temperature diffusion was highest through amalgam and slowest through the composite resin. 2. As the thickness of restorations increased, the temperature change was decreased. 3. Thermal diffusion was slowest in the presence of zinc oxide-eugenol bases, followed by calcium hydroxide and zinc phosphate cement. 4. The efficiency of the cement bases in providing thermal insulation was dependent on their thickness beneath the restorations. 5. Thermal change was great in the range of $60^{\circ}C$ and $-50^{\circ}C$, but little in the range of $0^{\circ}C$.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.1
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• pp.103-111
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• 2020

Pulling-type cutting devices, which use a diamond wire saw, have been used generally for cutting concrete structures. In this study, a pushing-type cutting device with a collection cover was developed by overcoming the disadvantages of pulling-type devices. In this device, dry or liquid methods can be selected to cool frictional heat. Operation and leakage tests of the dust generated during the dismantling of a concrete structure were carried out, confirming the suitable operation of the fabricated cutting device; the leakage rate was approximately 1.7%. For a conservative evaluation, the internal dose of workers was estimated in dismantling the core center part of biological shield concrete with a specific activity of 99.5 Bq·g^-1. The committed effective dose per worker was 0.25 mSv. The developed cutting device contributed to reducing radioactive concrete waste and minimizing worker exposure due to its easy installation. Therefore, it can be utilized as a cutting apparatus for dismantling not only reinforced concrete structures but also radioactive biological shield concrete in nuclear power plant decommissioning efforts.

• Nuclear Engineering and Technology
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• v.17 no.4
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• pp.290-301
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• 1985

600MW(e) CANDU Primary Heat Transport System (PHTS) is composed of the two “figure-of-eight” loops and is designed to operate with the 4% Reactor Outlet Header (ROH) quality at its rated power. This existence of the two compressible regions and the positive flow-qualitly-void feedbacks are the sources of the PHTS flow instability. To ensure the PHTS stability, ROH-ROH interconnect pipes are installed as passive systems. This paper describes the investigation of the PHTS flow instability at its design full power condition. Also studied are the interconnect effect and the inherent system damping effect on the system stability. The time domain stability analyses are accessed by using the ATHER/MOD-I code which is the improved version of the KAERI developed ATHER code. Under the most adverse system modelling, the “figure-of-eight” symmetric loop shows divergent flow oscillations. Under with the interconnect, the PHTS stability is remarkably enhanced so that the system becomes stable. However, even under the conservative pressurizer modelling, the PHTS shows the more convergent flow oscillations. With the interconnect and the pressurizer modelling, its stability is highly credited. Conclusively, the inherent system damping by pressurizer itself can credit the PHTS stability without the interconnect.

• Elastomers and Composites
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• v.45 no.4
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• pp.263-271
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• 2010

Intermittent CSR testing was used to investigate the degradation of an FKM O-ring, also the prediction of its life-time. An intermittent CSR jig was designed taking into consideration the O-ring's environment under use. The testing allowed observation of the effects of friction, heat loss, and stress relaxation by the Mullins effect. Degradation of O-rings by thermal aging was observed between 60 and $160^{\circ}C$. In the high temperature of range ($100-160^{\circ}C$) O-rings showed linear degradation behavior and satisfied the Arrhenius relationship. The activation energy was about 60.2 kJ/mol. From Arrhenius plots, predicted life-times were 43.3 years and 69.9 years for 50% and 40% failure conditions, respectively. Based on TTS (time-temperature superposition) principle, degradation was observed at $60^{\circ}C$, and could save testing time. Between 60 and $100^{\circ}C$ the activation energy decreased to 48.3 kJ/mol. WLF(William-Landel-Ferry) plot confirmed that O-rings show non-linear degradation behavior under $80^{\circ}C$. The life-time of O-rings predicted by TTS principle was 19.1 years and 25.2 years for each failure condition. The life-time predicted by TTS principle is more conservative than that from the Arrhenius relationship.