• Nuclear Engineering and Technology
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• 제44권4호
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• pp.393-404
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• 2012

After the Fukushima nuclear accident in 2011, there has been increasing concern regarding severe accidents in nuclear facilities. Severe accident scenarios are difficult for operators to monitor and identify. Therefore, accurate prediction of a severe accident is important in order to manage it appropriately in the unfavorable conditions. In this study, artificial intelligence (AI) techniques, such as support vector classification (SVC), probabilistic neural network (PNN), group method of data handling (GMDH), and fuzzy neural network (FNN), were used to monitor the major transient scenarios of a severe accident caused by three different initiating events, the hot-leg loss of coolant accident (LOCA), the cold-leg LOCA, and the steam generator tube rupture in pressurized water reactors (PWRs). The SVC and PNN models were used for the event classification. The GMDH and FNN models were employed to accurately predict the important timing representing severe accident scenarios. In addition, in order to verify the proposed algorithm, data from a number of numerical simulations were required in order to train the AI techniques due to the shortage of real LOCA data. The data was acquired by performing simulations using the MAAP4 code. The prediction accuracy of the three types of initiating events was sufficiently high to predict severe accident scenarios. Therefore, the AI techniques can be applied successfully in the identification and monitoring of severe accident scenarios in real PWRs.

• 청정기술
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• 제5권2호
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• pp.53-61
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• 1999

대형 산업용 환경폐기물 처리 및 열병합 플랜트의 연소 및 소각 공정 후 발생하는 배기가스의 폐열회수장치 설계 방법을 제시하였다. 본 연구는 폐열회수장치의 기본 설계 개념을 폐열회수를 위한 보일러와 폐열을 이용한 증기 동력 사이클로 구성되는 것으로 가정하였고, 폐열회수장치에 필요한 각 구성요소들에 대한 모델링 기법과 그에 따른 설계 기준 및 설계 개념을 기술하였다. 또한 본 설계방법을 이용하여, 동일한 배기가스 조건에 대해, 폐열회수 보일러의 작동 압력 및 폐열회수 열교환기 설계에 따라 폐열회수장치의 열성능이 어떻게 변화되는지를 검토하였다.

• 한방안이비인후피부과학회지
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• 제17권3호
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• pp.153-166
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• 2004

In addition to antiseptic／antibiotic regimens, current therapies such as topical and systemic corticosteroids, anti-histamine agents, immune suppressing agent are generally used in the western medicine to treat atopic dermatitis(AD). However, there is almost a complete lack of effective strategies to achieve long-term control of disease, oriental medical treatments are proposed an alternative measure. It has been proved by experimental and clinical study that Oriental medical atopic dermatitis(AD) treatments such as herb-medicine, acupuncture and moxibustion therapy, and steam therapy are effective in long-term treatment. Nevertheless, oriental medical therapy has some limitations to treat acute stage of the disease. Recently developed No-Hoe(蘆？: Aloe vera L.) extract dressings will be a supplementary methods to the oriental medical therapy. The dressing can subside pruritus, exudation, erythema and scaling in the acute stage of atopic dermatitis(AD). We applied the No-Hoe(蘆？: Aloe vera L.) extract dressings to eight atopic dermatitis patients and got some good effects. This reports will provide an alternative choice for the oriental and westernal medical therapy for long-term AD treatment.

• 한국식품영양과학회지
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• 제27권1호
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• pp.69-74
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• 1998

자숙가리비의 shelf-life를 연장하기 위하여 열처리하여 탈각한 가리비에 보존제를 첨가한 다음 $5^{\circ}C$에 저장하면서 여러 가지 화학적 및 미생물적 변화를 분석하였다. pH는 저장기간이 증가할수록 감소하였으며, 보존제 첨가군들은 저장 후반에 급격한 pH 감소를 억제하였다. 보존제 첨가는 저장 후분에 있어서 TMA, VBN, 및 TBA 생성을 억제하였으며, 전반적으로 숙성 초기에 있어서 미생물의 성자을 억제하였다. 보존제 첨가는 자숙가리비의 shelf-life를 약 3~7일 정도 연장하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2664-2669
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• 2008

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction stream line- inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes operation of experience and numerical analysis composed similar condition with real high pressure feedwater heater. This study applied squared, curved and new type impingement baffle plates to feedwater heater same as previous study. In addition, it shows difference of pressure distribution and value between single phase and two phase based on experience and numerical analysis.

• Nuclear Engineering and Technology
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• 제36권1호
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• pp.36-46
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• 2004

The ISAAC fission product release calculation is based on detailed FPRAT models developed by Jaycor. For volatile fission product release calculations, either the Cubicciotti steam oxidation correlation or the NUREG-0772 correlation is used. In this study, evaluation is carried out for these volatile fission product release models. As a result, in the case of early release, the IDCOR model with an in-vessel Te release option shows the most conservative results and for the late release case, the NUREG-0772 model shows the most conservative results. Considering both early and late release, the IDCOR model with an in-vessel Te bound option is evaluated to show mitigated conservative results. In addition, a sensitivity study on detailed core nodalization is performed. In the study, 380 horizontal fuel channels in the Wolsong plant are nodalized into 12 (6 channels per loop, $3{\times}3$ Core Pass) representative channels and detailed by 16/20/24 channels. For reference accidents, LOAH and large LOCA are selected as representing high and low pressure sequences, respectively. According to the results, the original 12 channel approach with $3{\times}3$ core passes is evaluated to be sufficient as an optimal scheme.

• Nuclear Engineering and Technology
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• 제32권6호
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• pp.618-635
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• 2000

A total of 17 experimental data for the onset of slugging, which is assumed to be the precursor of the condensation-induced waterhammer (CIWH), have been obtained for various How rates of water Incorporating the most recent correlations of interfacial heat transfer and friction factor developed for a circular geometry and using an improved criterion of transition from stratified to a slug flow, two existing analytical models to predict lower and upper bounds for CIWH have been upgraded. Applicability of the present as well as existing CIWH models has been tested by comparison with two sets of CIWH data. The result of this comparison shows that the applicability of the present as well as existing models is reasonably good. Based on the present models for CIWH, a computer code entitled as“KAIST-CIWH”has been developed and sample guide charts to find CIWH free regions for a given combination of major flow parameters in a long horizontal pipe have been presented along with the results of parametric studies of major parameters (D, P, $T_{f,in}$, and L/D) on the critical inlet water flow rate（$W_{f,in}_crit$ for both lower and upper bounds. In addition, two simple formulas for lower and upper bounds that can be used in an emergency for quick results have been presented.

• 설비공학논문집
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• 제21권9호
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• pp.483-495
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• 2009

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction stream line-inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes operation of experience and numerical analysis composed similar condition with real high pressure feedwater heater. This study applied squared, curved and new type impingement baffle plates to feedwater heater same as previous study. In addition, it shows difference of pressure distribution and value between single phase and two phase based on experience and numerical analysis.

• 한국재료학회지
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• 제12권5호
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• pp.369-374
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• 2002

To investigate the corrosion behavior of Zr-1.0Nb-xSn (x=1.0, 1.5, 2.0 and 2.5wt. %)alloy system, the corrosion tests of Zr-1.0Nb-xSn alloys were carried out in steam at $400^{\circ}C$ for 125 days and in 70ppm LiOH solution at $360^{\circ}C$ for 180 days. The matrix microstructures of the test specimens were analyzed using TEM and the oxide structures on the test specimens were analyzed using XRD. It was found from the analyses that the more Sn content the alloy had, the faster it was corroded and with the increase of Sn content in the alloy the fraction of $t-ZrO_2$ to $m-ZrO_2$ was decreased. It was also found that the alloys having more Sn showed more dislocation density than those having less.

• 한국수소및신에너지학회논문집
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• 제27권5호
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• pp.571-580
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• 2016

In this paper, performance of the gas turbine combined cycle(GTCC) using pre-combustion carbon capture technology was comparatively analysed. Steam reforming and autothermal reforming were used. In the latter, two different methods were adopted to supply oxygen for the reforming process. One is to extract air form gas turbine compressor (air blowing) and the other is to supply oxygen directly from air separation unit ($O_2$ blowing). To separate $CO_2$ from the reformed gas, the chemical absorption system using MEA solution was used. The net cycle efficiency of the system adopting $O_2$ blown autothermal reforming was higher than the other two systems. The system using air blown autothermal reforming exhibited the largest net cycle power output. In addition to the performance analysis, the influence of fuel reforming and carbon capture on the operating condition of the gas turbine and the necessity of turbine re-design were investigated.