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Yanggu, South Korea

Youn B.-S.,KHNP Central Research Institute
International Congress on Advances in Nuclear Power Plants, ICAPP 2014 | Year: 2014

An integral effect test for a main stem line break (MSLB) was performed with the ATLAS (Advanced Thermal-Hydraulic Test Loop for Accident Simulation) by KAERI. A MSLB is defined as a pipe break in the main steam system. This data was used to validate the safety analysis code SPACE (Safety and Performance Analysis Code for Nuclear Power Plants). In the test, a double-ended guillotined break of the main steam line was simulated. After a steady-state was reached, the test was started by opening the break simulation valves. With the start of the test, the pressure of the secondary system was decreased rapidly, which is the set-point of the LSGP signal. With the occurrence of the LSGP signal, the secondary system was isolated. The SIP actuation signal was issued by the LPP signal. When the MSLB event was initiated by opening the break simulation valve, the SG was depressurized. The calculation results and experimental values differed due to the difference in the flow rate corresponding to the break point. In order to validate the SPACE code, a double-ended guillotine break of the main steam line at ATLAS was simulated. Most of the results were identical between the experiment data and the code values. Source

Kim D.,KAIST | Kim D.,Korea Atomic Energy Research Institute | Lee H.J.,KAIST | Jang C.,KAIST | Yoon D.J.,KHNP Central Research Institute
Journal of Nuclear Materials | Year: 2013

The hot steam corrosion behavior of Alloy 617 and Haynes 230 were evaluated in corrosion tests performed at 900 °C in steam and steam + 20 vol.% H 2 environments. Corrosion rates of Alloy 617 was faster than that of Haynes 230 at 900 °C in steam and steam + 20 vol.% H2 environments. When hydrogen was added to steam, the corrosion rate was accelerated because added hydrogen increased the concentration of Cr interstitial defects in the oxide layer. Isolated nodular MnTiO3 oxides were formed on the MnCr2O4/ Cr2O 3 oxide layer and sub-layer Cr2O3 was formed in steam and steam + 20 vol.% H2 for Alloy 617. On the other hand, a MnCr2O4 layer was formed on top of the Cr 2O3 oxide layer for Haynes 230. The extensive sub-layer Cr2O3 formation resulted from the oxygen or hydroxide inward diffusion in such environments. When hydrogen was added, the initial surface oxide morphology was changed from a convex shape to platelets because of the accelerated diffusion of cations under the oxide layer. © 2013 Elsevier B.V. All rights reserved. Source

Yang K.-H.,Kyonggi University | Mun J.-H.,Kyonggi University | Cho M.-S.,KHNP Central Research Institute | Kang T.H.-K.,Seoul National University
ACI Structural Journal | Year: 2014

This study aims to develop a simple and rational stress-strain model that is applicable to unconfined concretes in compression, covering a wide range of compressive strengths between 10 and 180 MPa (1.5 and 26.1 ksi) and concrete densities between 1200 and 4500 kg/m3 (75 and 280 lb/ft3). In developing the stressstrain model, the modulus of elasticity, the strain at peak stress, and the strain at 50% of the peak stress on the descending branch were formulated using regression analysis of 3295, 415, and 96 data points, respectively. Numerical and statistical analyses were then performed to derive equations for the key parameter determining the shapes of the ascending and descending branches of the stress-strain curves. The reliability of the developed model was confirmed by comparisons with actual stress-strain curves obtained from 100 specimens with different compressive strengths and densities. On the other hand, other existing models were shown to have limitations for use on lightweight concrete, heavyweight concrete, and high-strength concrete. © 2014, American Concrete Institute. Source

Lee H.C.,KHNP Central Research Institute
Applied Chemistry for Engineering | Year: 2013

ETA (ethanolamine), a pH control agent, has been used as an ammonia substitute in the secondary system of nuclear power plants since 2001. It is impossible to remove ETA from the wastewater treatment system in the nuclear power plant operating currently, because it is the non-biodegradable organics in terms of the environmental. The optimum process and chemicals for the removal of chemical oxygen demand (COD) & N with the field sample were investigated. More than 95% of Ammonium ions, contained much in wastewater, was removed with a diffused aeration system. COD could be removed over 90% through the process that includes the oxidation with mixed peroxidants (sodium persulfate/sodium percarbonate) followed by the physicochemical treatment with coagulants. Source

Kwak H.-G.,Korea Advanced Institute of Science and Technology | Kwon Y.,KHNP Central Research Institute
Annals of Nuclear Energy | Year: 2016

This paper proposes a modified stress-strain relation for bonded internal tendon in containment structures on the basis of the tension stiffening effect and the bond characteristics between a tendon and its surrounding concrete. Differently from general approaches for the consideration of bond-slip, which take the double nodes in defining the displacement field, the proposed model indirectly considers the bond-slip effect through the modification for the stress-strain relation of tendon. Since the proposed tendon model takes into account the bond-slip effect without taking double nodes in the numerical modeling of containment structures, it can effectively be implemented into commercialized programs which have a lot of limitation in considering the bond-slip effect at large complex containment structures. The solution algorithm for an un-bonded internal tendon whose structural response is not section-dependent but member-dependent is also introduced. The different structural responses from those in bonded tendon are evaluated by successive iterations and finally considered by the additional modification for the stress-strain relation of tendon. The validity of the proposed tendon model is verified through correlation studies between analytical and experimental results for PSC beams and 1/4 PCCV containment structures. © 2016 Elsevier B.V. All rights reserved. Source

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