• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.522-523
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• 2005

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.444-445
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• 2005

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.213-218
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• 2003

Because of the development of digital technology, modern digital instrumentation & control systems are being innovativly developed in industrial plants. Whereas, many analog systems are still being used in nuclear plants, because of the demerits of digital equipment. As known, the demerits of digital equipment are the uncertainty and weaknesses in ambient environments such as smoke & electromagnetic interference In an Integral Reactor, a digital I&C system will be composed of microprocessor, memory and network card. Designers will apply new technique for digital equipment. Thus, it is important for digital I&C systems to operate according to designed functions & performance in the ambient environments during a life cycle. Digital I&C systems should have tolerance in such environments and environment qualification should be concluded To acquire electromagnetic interference qualification of digital equipment, this paper suggests an EMI test requirement. Designers should consider the electromagnetic compatibility and test digital equipment according to each test procedure. This paper involves an EMI test requirement and the results analysis of EUT(Equipment Under Test). Test result analysis will be used as electromagnetic compatibility design guides for Integral Reactor I&C systems.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.65-73
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• 1989

Continuum formulations for the expressions of dynamic energy release rates and computational methods for dynamic stress intensity factors are developed for the analysis of dynamic fracture problems subjected to stress wave loading. Explicit volume integral expressions for instantaneous dynamic energy release rates are derived by modeling virtual crack extensions with the dynamic Eulerian-Lagrangian kinematic description. In the finite element applications a finite region around a crack-tip is modeled by using quarter-point singular isoparametric elements, and the volume integrals are evaluated for each crack-tip element during virtual crack extensions while the singularity is maintained. It is shown that the use of the present method is more reliable and accurate for the dynamic fracture analysis than that of other path-independent integral methods when the effects of stress waves are significant.

• Nuclear Engineering and Technology
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• v.38 no.4
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• pp.343-352
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• 2006

Convenient analytical tools for evaluation of the aperiodic and the fluctuating instabilities of the passive residual heat removal system (PRHRS) of an integral reactor are developed and results are discussed from the viewpoint of the system design. First, a static model for the aperiodic instability using the system hydraulic loss relation and the downcomer feedwater heating equations is developed. The calculated hydraulic relation between the pressure drop and the feedwater flow rate shows that several static states can exist with various numbers of water-mode feedwater module pipes. It is shown that the most probable state can exist by basic physical reasoning, that there is no flow rate through the steam-mode feedwater module pipes. Second, a dynamic model for the fluctuating instability due to steam generation retardation in the steam generator and the dynamic interaction of two compressible volumes, that is, the steam volume of the main steam pipe lines and the gas volume of the compensating tank is formulated and the D-decomposition method is applied after linearization of the governing equations. The results show that the PRHRS becomes stabilized with a smaller volume compensating tank, a larger volume steam space and higher hydraulic resistance of the path $a_{ct}$. Increasing the operating steam pressure has a stabilizing effect. The analytical model and the results obtained from this study will be utilized for PRHRS performance improvement.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.10a
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• pp.21-28
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• 1998

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2000.04a
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• pp.281-286
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• 2000

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3350-3356
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• 2013

Quasi-classical trajectory calculations have been carried out for the reaction H+HS by using the newest triplet 3A" potential energy surface (PES). The effects of the collision energy and reagent initial rotational excitation are studied. The cross sections and thermal rate constants for the title reaction are calculated. The results indicate that the integral cross sections (ICSs) are sensitive to the collision energy and almost independent to the initial rotational states. The ro-vibrational distributions for the product $H_2$ at different collision energies are presented. The investigations on the vector correlations are also performed. It is found that the collision energies play a postive role on the forward scatter of the product molecules. There is a negative influence on both the alignment and orientation of the product angular momentum for low collision energy at low energy region. Whereas the influence of collision energy is not obvious at high energy region.

• Nuclear Engineering and Technology
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• v.41 no.1
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• pp.53-62
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• 2009

A set of experiments has been conducted on the performance sensitivity of the passive residual heat removal system (PRHRS) for an advanced integral type reactor, SMART, by using a high temperature and high pressure thermal-hydraulic test facility, the VISTA facility. In this paper the effects of the opening delay of the PRHRS bypass valves and the closing delay of the secondary system isolation valves, and the initial water level and the initial pressure of the compensating tank (CT) are investigated. During the reference test a stable flow occurs in a natural circulation loop that is composed of a steam generator secondary side, a secondary system, and a PRHRS; this is ascertained by a repetition test. When the PRHRS bypass valves are operated 10 seconds later than the secondary system isolation valves, the primary system is not properly cooled. When the secondary system isolation valves are operated 10 or 30 seconds later than the PRHRS bypass valves, the primary system is effectively cooled but the inventory of the PRHRS CT is drained earlier. As the initial water level of the CT is lowered to 16% of the full water level, the water is quickly drained and then nitrogen gas is introduced into the PRHRS, resulting in the deterioration of the PRHRS performance. When the initial pressure of the PRHRS is at 0.1MPa, the natural circulation is not performed properly. When the initial pressures of the PRHRS are 2.5 or 3.5 MPa, they show better performance than did the reference test.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.608-616
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• 2015

The migration of silver (Ag) in silicon carbide (SiC) and $^{110m}Ag$ through SiC of irradiated tristructural isotropic (TRISO) fuel has been studied for the past three to four decades. However, there is no satisfactory explanation for the transport mechanism of Ag in SiC. In this work, the diffusion coefficients of Ag measured and/or estimated in previous studies were reviewed, and then pre-exponential factors and activation energies from the previous experiments were evaluated using Arrhenius equation. The activation energy is $247.4kJ{\cdot}mol^{-1}$ from Ag paste experiments between two SiC layers produced using fluidized-bed chemical vapor deposition (FBCVD), $125.3kJ{\cdot}mol^{-1}$ from integral release experiments (annealing of irradiated TRISO fuel), $121.8kJ{\cdot}mol^{-1}$ from fractional Ag release during irradiation of TRISO fuel in high flux reactor (HFR), and $274.8kJ{\cdot}mol^{-1}$ from Ag ion implantation experiments, respectively. The activation energy from ion implantation experiments is greater than that from Ag paste, fractional release and integral release, and the activation energy from Ag paste experiments is approximately two times greater than that from integral release experiments and fractional Ag release during the irradiation of TRISO fuel in HFR. The pre-exponential factors are also very different depending on the experimental methods and estimation. From a comparison of the pre-exponential factors and activation energies, it can be analogized that the diffusion mechanism of Ag using ion implantation experiment is different from other experiments, such as a Ag paste experiment, integral release experiments, and heating experiments after irradiating TRISO fuel in HFR. However, the results of this work do not support the long held assumption that Ag release from FBCVD-SiC, used for the coating layer in TRISO fuel, is dominated by grain boundary diffusion. In order to understand in detail the transport mechanism of Ag through the coating layer, FBCVD-SiC in TRISO fuel, a microstructural change caused by neutron irradiation during operation has to be fully considered.