• Nuclear Engineering and Technology
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• 제43권6호
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• pp.499-508
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• 2011

The paper briefs a fuel performance code, COSMOS, which can be utilized for an analysis of the thermal behavior and fission gas release of fuel, up to a high burnup. Of particular concern are the models for the fuel thermal conductivity, the fission gas release, and the cladding corrosion and creep in $UO_2$ fuel. In addition, the code was developed so as to consider the inhomogeneity of MOX fuel, which requires restructuring the thermal conductivity and fission gas release models. These improvements enhanced COSMOS's precision for predicting the in-pile behavior of MOX fuel. The COSMOS code also extends its applicability to the instrumented fuel test in a research reactor. The various in-pile test results were analyzed and compared with the code's prediction. The database consists of the $UO_2$ irradiation test up to an ultra-high burnup, power ramp test of MOX fuel, and instrumented MOX fuel test in a research reactor after base irradiation in a commercial reactor. The comparisons demonstrated that the COSMOS code predicted the in-pile behaviors well, such as the fuel temperature, rod internal pressure, fission gas release, and cladding properties of MOX and $UO_2$ fuel. This sufficient accuracy reveals that the COSMOS can be utilized by both fuel vendors for fuel design, and license organizations for an understanding of fuel in-pile behaviors.

• 한국가스학회지
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• 제18권4호
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• pp.76-85
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• 2014

본 연구는 독성가스 사고의 주요 원인의 하나인 부식에 대해 고압 독성가스시설을 대상으로 필요한 안전기술을 정립하기 위하여 미국석유학회에서 개발한 API-581 절차를 채택하여 사고결과 분석방법에 대한 적용성을 검토하고, 이를 바탕으로 사고결과 분석방법을 제시하였다. 고압 독성가스시설에서 API-581의 8단계 사고결과 분석절차에 따라 단계별 적용성을 검토한 결과, 고압 독성가스시설에 적용할 사고결과 분석방법은 총 6단계로 단순화 할 수 있었다. 즉, Step 1(대표물질 결정), Step 5(누출유형 결정), Step 6(유체상 결정)과 Step 8(사고 피해영역 산출)은 적용하지 않고, Step 3(누출량 산출)은 inventory group 개념만 적용하며, Step 4(누출속도 산출)는 기체 누출속도만을 적용하고, Step 2(누출공 크기 선정)와 Step 7(완화시스템 등급 결정)은 전부 적용한다. 이때, Step 5와 Step 8은 일반적으로 적용이 가능한 CCPS 방법을 대안적인 방법으로 채택한다.

• 한국환경과학회지
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• 제17권6호
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• pp.689-698
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• 2008

Numerical study is conducted to predict effects of radiative heat loss and fuel composition in synthetic gas diffusion flame diluted with $CO_2$. The existing reaction models in synthetic gas flames diluted with $CO_2$ are evaluated. Numerical simulations with and without gas radiation, based on an optical thin model, are also performed to concrete impacts on effects of radiative heat loss in flame characteristics. Importantly contributing reaction steps to heat release rate are compared for synthetic gas flames with and without $CO_2$ dilution. It is also addressed that the composition of synthetic gas mixtures and their radiative heat losses through the addition of $CO_2$ modify the reaction pathways of oxidation diluted with $CO_2$.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.32-41
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• 1999

Natural gas is an attractive fuel in view of environment benefits due to its flow carbon-to-hydrogen ratio. However, its compositions and properties are varied depending upon production regional groups. Therefore, study on the combustion characteristics of natural gas engines with a variety of compositions has been demanded for the efficient application of gas engines. This study aims to investigate the effects of gas composition on engine combustion characteristics. It was found that , by controlling an engine with fixed fuel nozzle area, power and heat release were subject to Wobbe Index. And at fixed excess air ratios, power and heat release were subject to low heating value of unit mixture . In addition, in case of constant nozzle area, combustion duration was found to be inversely proportional to CP(Combustion Potential), and the condition of fixed excess air ratios showed no change in combustion duration, regardless of CP.

• Nuclear Engineering and Technology
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• 제22권2호
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• pp.116-127
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• 1990

SPEAR-BETA코드에서 사용된 핵분열 기체 방출 모델을 핵연료와 피복관 사이의 갭(gap)과 플레넘(plenum) 사이에서 축방향 핵분열 기체 혼합과 균열된 핵연료에 대한 유효 열전도도를 사용함으로써 개량하여, P$_{max}$와$\Delta$P가 변하는 다양한 출력 감발 조건하에서 핵분열기체 방출 거동을 해석하였다. 핵연료 균열의 영향을 고려한 유효 열전도도는 핵연료의 온도 분포와 내부 기체 압력을 계산하는데 사용되었고, 축방향 기체 유동으로 인한 혼합(mixing)과 회석(dilution)효과는 갭의 폭과 열전도도를 해석하는데에 고려되었다. 축방향 기체 유동 효과를 계산하는데 있어서 계산속도를 빠르게 하기 위하여 유한차분법의 하나인 Crank-Nicholson 방법을 사용하였다. 개량된 모델은 다양한 출력 감발 조건하에서 얻어진 실험 자료들과 SPEAR-BETA와 FEMAXl-IV 코드들에서 사용되는 모델들로부터 얻은 결과들을 비교함으로써 검증하였다. 개량된 모델의 결과는 위의 두 코드로부터 얻은 결과 보다는 실험자료들과 잘 일치하였다. 균열된 핵연료에 대해 유효 열전도도를 사용하여 계산한 핵연료의 중심 온도는 균열되지 않은 핵연료의 경우에 비해 20$0^{\circ}C$ 정도보다 높은 값을 나타냈고, 개량된 핵분열 기체 생성물의 분율은 SPEAR-BETA코드에서 얻은 값보다 평균 6% 정도가 높게 나타났다.평균 6% 정도가 높게 나타났다.다.

• 한국가스학회지
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• 제8권4호
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• pp.8-14
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• 2004

독성가스의 누출은 공정설비의 위험도에 크게 영향을 미친다. 본 연구에서는 API-581에 의한 위험기반검사에서 매개변수의 변화에 따른 독성가스(암모니아 및 염소 가스)의 누출사고 결과를 분석하였다. 그 결과, 독성물질의 누출에 의한 사고결과, 즉 독성 피해영역은 온도가 증가할수록, 그리고 압력과 파이프 직경이 감소할수록 감소하였으며, 동일한 누출조건에서 암모니아 보다 염소가스인 경우에 큰 값을 나타내었다.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2402-2409
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• 2020

Analytical criteria for the onset of fuel fragmentation and Burst Fission Gas Release in fuel rods with ballooned claddings are formulated. On that basis, the GRSW-A model integrated with a fuel behaviour code is updated. After modification, the updated code is successfully applied to simulation of the Halden LOCA test IFA-650.12. Specifically, the calculation with Burst Fission Gas Release during the test resulted in prediction of cladding failure, whereas it could not be predicted at the test planning, before new models were implemented. A good agreement of the current model with experimental data for transient Fission Gas Release in the tests IFA-650.12 and IFA-650.14 is shown, as well.

• Nuclear Engineering and Technology
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• 제29권1호
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• pp.7-14
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• 1997

Grain boundary diffusion plays a significant role in fission gas release, which is one of the crucial processes dominating nuclear fuel performance. Gaseous fission produce such as Xe and Kr generated during nuclear fission have to diffuse in the grain lattice and the boundary inside fuel pellets before they reach the open spaces in a fuel rod. These processes can be studied by 'tracer diffusion' techniques, by which grain boundary diffusivity can be estimated and directly used for low burn-up fission gas release analysis. However, only a few models accounting for the both processes are available and mostly handle them numerically due to mathematical complexity. Also the numerical solution has limitations in a practical use. In this paper, an approximate analytical solution in case of stationary grain boundary in a polycrystalline solid is developed for the tracer diffusion techniques. This closed-form solution is compared to available exact and numerical solutions and it turns out that it makes computation not only greatly easier but also more accurate than previous models. It can be applied to theoretical modelings for low bum-up fission gas release phenomena and experimental analyses as well, especially for PIE (post irradiation examination).

• Nuclear Engineering and Technology
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• 제32권5호
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• pp.425-432
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• 2000

It has been an essential part for the safety assessment of nuclear power plants to understand various phenomena associated with the molten core-concrete interaction(MCCI) under severe accidents. In this study, the severe accident analysis code MELCOR was used to simulate the MCCI experiments such as SWISS and SURC test series which had been performed in Sandia National Laboratories(SNL). The calculation results were compared with corresponding experimental data such as melt temperature, concrete ablation distance, gas generation rate, and aerosol release rate. Good agreements were observed between MELCOR calculation and experimental data. The melt pool was sustained within the range of high temperature and the concrete ablation occurred continuously. The gas generation and aerosol release were under the influence of melt temperature and overlying water pool, respectively.

• 대한안전경영과학회지
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• 제20권4호
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• pp.15-19
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• 2018

The purpose of this study is to enhance heat insulation effect and to decrease fire hazard by attaching aluminum foil to expanded polystyrene, which is mainly used for insulating materials, to have fire retardant. The result of the test confirmed that the insulating materials, expanded polystyrene of $10kg/m^3$ and $14kg/m^3$ of density attached aluminum foil on both sides, showed 12%, 14% of improved heat transfer coefficient respectively compared to existing expanded polystyrene of the same density. Besides, they met all the standards for the testing of heat release and gas hazard. On the other hand, the one made of general expanded polystyrene could not meet the standards of the heat release test and the gas hazard test.