• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.669-674
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• 1996

The analysis for the coolability of the reactor cavity in typical Korean 1000 MWe Nuclear Unit under severe accidents is performed using MELCOR 1.8.3 code. The key parameters molten core-concrete interaction(MCCI) such as melt temperature, concrete ablation history and gas generation are investigated. Total twenty cases are selected according to ejected debris fraction and coolant mass, The ablation rate of concrete decreases as mass of the melt decreases and coolant mass increases. Heat loss from molten pool to coolant is comparable to total decay heat, so concrete ablation is delayed until water is absent and crust begins to remove. Also, overpressurization due to non-condensible gases generated during corium and concrete interacts can cause to additional risk of containment failure. It is concluded that flooded reactor cavity condition is very important to minimize the cavity ablation and pressure load by non-condensible gases on containment.

• 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.

• Nuclear Engineering and Technology
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• 제44권3호
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• pp.261-272
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• 2012

Molten Core Concrete Interaction (MCCI) is a complex process characterized by concrete ablation and volatile generation; Thermal and solutal convection in a bubble-agitated melt; Physico-chemical evolution of the corium pool with a wide solidification range (of the order of 1000 K). Twelve experiments have been carried out in the VULCANO facility with prototypic corium and sustained heating. The dry oxidic corium tests have contributed to show that silica-rich concrete experience an anisotropic ablation. This unexpected ablation pattern is quite reproducible and can be recalculated, provided an empirical anisotropy factor is assumed. Dry tests with oxide and metal liquid phases have also yielded unexpected results: a larger than expected steel oxidation and unexpected topology of the metallic phase (at the bottom of the cavity and also on the vertical concrete walls). Finally, VULCANO has proved its interest for the study of mitigation solutions such as the COMET bottom flooding core catcher.

• Clinical and Experimental Reproductive Medicine
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• 제49권2호
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• pp.76-86
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• 2022

Ovarian cystectomy is the preferred technique for the surgical management of ovarian endometrioma. However, other techniques such as ablation or sclerotherapy are also commonly used. The aim of this review is to summarize information regarding the efficacy of ablation and sclerotherapy compared to cystectomy in terms of ovarian reserve, the recurrence rate, and the pregnancy rate. Several studies comparing ablation versus cystectomy or sclerotherapy versus cystectomy in terms of the serum anti-Müllerian hormone (AMH) decrement, endometrioma recurrence, or the pregnancy rate were identified and summarized. Both ablation and cystectomy have a negative impact on ovarian reserve, but ablation results in a smaller serum AMH decrement than cystectomy. Nonetheless, the recurrence rate is higher after ablation than after cystectomy. More studies are needed to demonstrate whether the pregnancy rate is different according to whether patients undergo ablation or cystectomy. The evidence remains inconclusive regarding whether sclerotherapy is better than cystectomy in terms of ovarian reserve. The recurrence rates appear to be similar between sclerotherapy and cystectomy. There is not yet concrete evidence that sclerotherapy helps to improve the pregnancy rate via in vitro fertilization in comparison to cystectomy or no sclerotherapy.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3491-3496
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• 2007

If a molten core is released from a reactor vessel into a reactor cavity during a severe accident, an important safety issue of coolability of the molten core from top-flooding and concrete ablation due to a molten core concrete interaction (MCCI) is still unresolved. The released molten core debris would attack the concrete wall and basemat of the reactor cavity, which will lead to inevitable concrete decompositions and possible radiological releases. In a OECD/MCCI project scheduled for 4 years from 2002. 1 to 2005. 12, a series of tests were performed to secure the data for cooling the molten core spread out at the reactor cavity and for the 2-D long-term core concrete interaction (CCI). The tests included not only separate effect tests such as a melt eruption, water ingression, and crust failure tests with a prototypic material but also 2-D CCI tests with a prototypic material under dry and flooded cavity conditions. The paper deals with the transient simulations on the CCI-2 test by using a severe accident analysis code, CORQUENCH, which was developed at Argonne National Laboratory (ANL). Similar simulations had been already per for me d by using MELCOR 1.8.5 code. Unlike the MELCOR 1.8.5, the CORQUENCH includes a melt eruption mode I and a newly developed water ingression model based on the water ingression tests under the OECD/MCCI project. In order to adjust the geometrical differences between the CCI-2 test (rectangular geometry) and the simulations (cylindrical geometry), the same scaling methodology as used in the MELCOR simulation was applied. For the direct comparison of the simulation results, the same inputs for the MELCOR simulation were used. The simulation results were compared with the previous results by using MELCOR 1.8.5.

• 한국압력기기공학회 논문집
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• 제17권2호
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• pp.90-100
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• 2021

Molten corium-concrete interaction (MCCI) is one of the most important phenomena that can lead to the potential hazard of late containment failure due to basemat penetration during a severe accident. In this study, MCCI analytical models of the CORQUENCH code were prepared through verification calculations of several experiments, which had been performed using concrete types similar to those of the calandria vault floor in CANDU-6 plants. The behaviors of thermal-hydraulic variables related to MCCI phenomena were analyzed under the conditions of dry floor and water flooding during the severe accident stemming from a hypothetic station blackout. Uncertainty analyses on the ablation depth were also carried out. It was estimated that the concrete ablation was not interrupted due to the continuous MCCI process under the dry condition but was terminated within 24 hours under the water flooding condition. It was confirmed that the water flooding as a mitigating action was effective to achieve the quenching and thermal stabilization of the melt discharged from the calandria vessel, showing that the present models are capable of reasonably simulating MCCI phenomena in CANDU-6 plants. This study is expected to provide the technical bases to the accident management strategy during the late-phase severe accidents.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1508-1515
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• 2022

In the present study, the cavity module of the MELCOR code is used for the simulation of molten corium concrete interaction (MCCI) during the late phase of postulated large break loss of coolant (LB-LOCA) accident in the APR1400 reactor design. Using the molten corium composition data from previous MELCOR Simulation of APR1400 under LB-LOCA accident, the ex-vessel phases of the accident sequences with long-term MCCI are recalculated with stand-alone cavity package of the MELCOR code to investigate the impact of water ingression and melt eruption models which were hitherto absent in MELCOR code. Significant changes in the MCCI behaviors in terms of the heat transfer rates, amount of gases released, and maximum cavity ablation depths are observed and reported in this study. Most especially, the incorporation of these models in the new release of MELCOR code has led to the reduction of the maximum ablation depth in radial and axial directions by ~38% and ~32%, respectively. These impacts are substantial enough to change the conclusions earlier reached by researchers who had used the older versions of the MELCOR code for their studies. and it could also impact the estimated cost of the severe accident mitigation system in the APR1400 reactor.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.268-271
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• 2008

If a reactor vessel is failed to retain a molten corium in a postulated severe accident, the molten corium is released outside the reactor vessel into a reactor cavity. The molten corium would attack the concrete wall and basemat of the reactor cavity, which may lead to inevitable concrete decompositions and possible radiological releases. In the OECD/MCCI project, a series of tests were performed to secure the data for cooling the molten corium spread out at the reactor cavity and for the long-term CCI (Core Concrete Interaction). Also, a MCCI (Molten Core Concrete Interaction) analysis code, CORQUENCH was upgraded at Argonne National Laboratory with embedding the new models developed for the tests. This paper deals with analyses of MCCI at plant scale under the conditions of top flooding using the upgraded CORQUENCH code. The modeling approach is briefly summarized first, followed by presentation of a validation calculation that illustrates the predicative capability of the modeling tool. With this background in place, the model is then used to carry out a parametric set of scoping calculations that define approximate coolability envelopes for the LCS (Limestone Common Sand) concrete that has been evaluated in the OECD/MCCI project.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1547-1554
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• 2017

VESTA (Verification of Ex-vessel corium STAbilization) and VESTA-S (-small) test facilities were constructed at the Korea Atomic Energy Research Institute in 2010 to perform various corium melt experiments. Since then, several tests have been performed for the verification of an ex-vessel core catcher design for the EU-APR1400. Ablation tests of an impinging $ZrO_2$ melt jet on a sacrificial material were performed to investigate the ablation characteristics. $ZrO_2$ melt in an amount of 65-70 kg was discharged onto a sacrificial material through a well-designed nozzle, after which the ablation depths were measured. Interaction tests between the metallic melt and sacrificial material were performed to investigate the interaction kinetics of the sacrificial material. Two types of melt were used: one is a metallic corium melt with Fe 46%, U 31%, Zr 16%, and Cr 7% (maximum possible content of U and Zr for C-40), and the other is a stainless steel (SUS304) melt. Metallic melt in an amount of 1.5-2.0 kg was delivered onto the sacrificial material, and the ablation depths were measured. Penetration tube failure tests were performed for an APR1400 equipped with 61 in-core instrumentation penetration nozzles and extended tubes at the reactor lower vessel. $ZrO_2$ melt was generated in a melting crucible and delivered down into an interaction crucible where the test specimen is installed. To evaluate the tube ejection mechanism, temperature distributions of the reactor bottom head and in-core instrumentation penetration were measured by a series of thermocouples embedded along the specimen. In addition, lower vessel failure tests for the Fukushima Daiichi nuclear power plant are being performed. As a first step, the configuration of the molten core in the plant was investigated by a melting and solidification experiment. Approximately 5 kg of a mixture, whose composition in terms of weight is $UO_2$ 60%, Zr 10%, $ZrO_2$ 15%, SUS304 14%, and $B_4C$ 1%, was melted in a cold crucible using an induction heating technique.

• Nuclear Medicine and Molecular Imaging
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• 제40권6호
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• pp.322-326
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• 2006

목적: 갑상선암 방사성요오드 치료를 위한 전처치로 1주${\sim}$2주간 저요오드식이를 시행하는 것이 국제 권고안에서 권고되고 있으나 각 병원마다 저요오드식이를 자체적인 교육방법에 따라 시행하고 있으며 저요오드식이를 통해 체내 요오드량을 효과적으로 낮추었는지에 대한 측정도 대부분의 병원에서 시행되지 않고 있어, 연구자들의 병원에 의뢰된 환자들의 소변 내 I/Cr비를 측정하여 고전적인 엄격한 저요오드식 이를 1주일간 시 행하는 방법과 덜 엄격한 저요오드식이를 2주일간 시행하는 방법을 비교하여 그 적절성을 평가하고자 하였다. 대상 및 방법: 2006년 4월 10일부터 6월 19일까지 본원에 의뢰된 27명의 환자를 대상으로 제한 및 허용식품 목록, 영양사 교육 유무, 예시 식단 유무, 저요오드식이 기간을 비교하여 가장 빈도가 높은 2가지 방법, 즉 관용적인 기준을 채택하는 군과 엄격한 제한식품을 설명한 군으로 나누어 두 군의 아침 소변을 채집, iodide selective electrode method를 사용하여 소변 내 요오드량을 측정하고 이를 소변 내 크레아티닌으로 나누어 I/Cr비를 구하였다. 두 군의 결과는 t-test를 이용하여 검정하였다. 결과: 두 군간의 특성에는 유의한 차이가 없었으며 각 군에서의 소변 내 I/Cr 비는 2주간 덜 엄격한 저요오드식이 군에서 $289.75{\pm}188.24{\mu}g/g$, 1주간 엄격한 저요오드식이를 시행한 군에서는 $127.87{\pm}78.52{\mu}g/g$으로 측정되었으며 1주간 엄격하게 시행한 군에서 유의하게 낮았다 (p=0.008). 2주간 덜 엄격한 저요오드식이를 시행한 군에서는 14명중 3명(21.42%), 1주간 엄격한 저요오드식이를 시행한 군에서는 13명중 6명(46.15%)이 방사성요오드치료를 위한 적정한 수준으로 제시된 소변 내 요오드배설량 $100{\mu}g/g$이하를 만족했다. 결론: 2주간 덜 엄격한 저요오드식이를 시행한 군에서 1주간 엄격한 교육을 시행한 군보다 높은 소변 내 I/Cr비가 나온 것을 볼 때 교육 방법을 엄격하게 시행하지 않고 간단하게 변형된 방법을 사용할 경우 기간을 길게 하더라도 치료에 필요한 적정 수준의 체내 요오드량 감소를 달성하기 어려울 것으로 판단된다. 그러나 1주간 엄격한 저요오드식이를 시행한 군에서도 체내 요오드량의 감소가 충분히 감소하는 비율이 여전히 낮기 때문에 엄격한 저요오드식이 방법을 2주간 시행하는 것이 더바람직하리라 기대된다.