• Nuclear Engineering and Technology
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• v.32 no.2
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• pp.99-107
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• 2000

A probabilistic integrity analysis method is presented for a reactor vessel under pressurized thermal shock(PTS) based on Monte Carlo simulation. This method can be applied to the structural integrity assessment of a reactor vessel subjected to pressurized thermal shock where the coolant temperature transient cannot be expressed explicitly as a time function. An axially or circumferentially oriented infinite length surface crack is assumed to be in the beltline weld region of the rector vessel's inside surface. The random variables are the initial crack depth, neutron fluence on the vessel's inside surface, the copper and nickel content of the vessel materials, R $T_{NDT}$ , $K_{IC}$ , and K/aub la/. The reliability of a sample reactor vessel under PTS is assessed quantitatively and the influence of the amount of neutron fluence is also examined by applying the present method.sent method.

• Nuclear Engineering and Technology
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• v.35 no.4
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• pp.261-273
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• 2003

The characteristics of the recirculation operation of LMR which are different from the conventional plants such as PWR and fossil fuel plants were investigated using a computer code TSGS developed in this study. For simulating the transient behavior of the steam generation system, a water level control algorithm utilizing digital control hardware features was introduced. By investigation, the function of the recirculation operation was defined, the major features of the operation were found. Also good performance of the level control algorithm was confirmed.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.154-161
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• 1997

Several studies have developed upward flame spread models which use somewhat different features. However, the models have not considered the transient effects of the igniter and the burning rate. Thus, the objective of this study is to examine a generalized upward flame spread model which includes these effects. We shall compare the results with results from simpler models used in the past in order to examine the importance of the simplifying assumptions. We compare these results using PMMA, and we also include experimental results for comparison. The results of the comparison indicate that flame velocity depends on the thermal properties of a material, the specific model for flame length and transient burning rate, as well as other variables including the heat flux by igniter and flame itself. The results from the generalized upward flame spread model can provide a prediction of flame velocity, flame and pyrolysis height, burnout time and position, and rate of energy output as a function of time.

• Bulletin of the Korean Mathematical Society
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• v.48 no.2
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• pp.397-412
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• 2011

In this paper, the equation of the transient Stokes flow of an incompressible viscous fluid is studied. Growth and decay estimates are established associating some appropriate cross sectional line and area integral measures. The method of the proof is based on a first-order differential inequality leading to an alternative of Phragm$\'{e}$n-Lindell$\"{o} $f type in terms of an area measure of the amplitude in question. In the case of decay, we also indicate how to bound the total energy.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.167-170
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• 1989

• Journal of the Korean Chemical Society
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• v.10 no.1
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• pp.18-24
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• 1966

In formulating the Transient State Theory of Significant Liquid Structure it is assumed that there exist holes of molecular size in liquids and that the liquid state is partitioned in three states, namely, solid-like state, representing the molecules apart from holes; gas-like state, representing the molecules jumping into the holes; and the transient state, representing the molecules in a possible state of jumping into the holes by aquiring the strain energy due to the holes. It is found that the partition function derived according to the proposed theory can be applied to the liquids of argon, nitrogen, benzene, chloroform, and carbon disulfide with good accuracy.

• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1572-1582
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• 2003

Hybrid rocket combustion has a manifestation of stable response to the perturbations compared to solid propellant combustion. Recently, it has revealed that the low frequency combustion instability about 10 Hz was occurred mainly due to thermal inertia of solid fuel. In this paper, the combustion response function was theoretically derived by use of ZN (Zeldovich-Novozhilov) method. The result with HTPB/LOX combination showed a quite good agreement in response function with previous works and could predict the low frequency oscillations with a peak around 10 Hz which was observed experimentally. Also, it was found that the amplification region in the frequency domain is independent of the regression rate exponent n but showed the dependence of activation energy. Moreover, the response function has shown that the hybrid combustion system was stable due to negative heat release of solid fuel for vaporization, even though the addition of energetic ingredients such as AP and Al could lead to increase heat release at the fuel surface.

• Nuclear Engineering and Technology
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• v.36 no.2
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• pp.184-195
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• 2004

The multi-tasking feature of digital I&C equipment could increase risk concentration because the I&C equipment affects the actuation of the safety functions in several ways. Anticipated Transient without Scram (ATWS) is a typical case of safety function failure in nuclear power plants. In a conventional analysis, mechanical failures are treated as the main contributors of the ATWS. This paper quantitatively presents the probability of the ATWS based on a fault tree analysis of a Korea Standard Nuclear Power Plant is also presented. An analysis of the digital equipment in the digital plant protection system. The results show that the digital system severely affects the ATWS frequency. We also present the results of a sensitivity study, which show the effects of the important factors, and discuss the dependency between human operator failure and digital equipment failure.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.302-311
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• 2016

This paper proposes a hybrid ESS that integrates an energy storage system (ESS) with an uninterruptible power supply (UPS). The hybrid ESS has a demand management and emergency power supply function while increasing the battery utilization of the UPS, which has just been used in a power failure. In addition to the critical load, the proposed system augments the capacity of emergency generation using an additional load, which has voltage and frequency-dependent characteristics to the grid side. The control algorithm of the AC-DC converter and bidirectional DC-DC converter is proposed for demand management and emergency power supply. Furthermore, seamless and autonomous transfer methods to alleviate the transient during mode transfer are proposed. To validate the proposed control scheme, experimental results from a 5 kW prototype are provided.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.4
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• pp.17-26
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• 2001

Simulation was conducted using TRNSYS to evaluate the thermal performance of a facility. This facility has a condensing-type heat exchanger which is able to recover the latent energy for the purpose of reducing the heating energy in winter. The boiler and chiller are selected based on the annual peak loads and controlled to maintain the facility at the set temperature of 14~$17^\circ{C}$. Supplied energy by the boiler and recovered energy by the heat exchanger were calculated as a function of number of pass through heat exchanger, kind of fuel and hot water velocity. Simulation results show that about 20% of the total heating load can be recovered by the heat exchanger and the amount of latent heat is increasing with the number of pass. This means that the efficiency of the waste energy recovery system can be increased by using a condensing-type heat exchanger rather than a traditional sensible heat exchanger.