• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
• /
• pp.199-206
• /
• 1997

For the Korean Next Generation Reactor(KNGR) development, LBB is considered for the Main Steam Line(MSL) piping inside its containment to achieve cost and safety Improvement. To apply LBB concept to MSL, leak sensors highly sensitive to humidity is required. In this paper, a ceramic material, MgCr$_2$O$_4$-TiO$_2$ has been developed as a humidity sensor for MSL applications. Experiments peformed to characterize the electrical conductivity shows that the conductivity of MgCr$_2$O$_4$-TiO$_2$ responds sensitively to both temperature and humidity changes. At a constant temperature below 10$0^{\circ}C$, the conductivity increases as the relative humidity increases, which makes the sensor favorable for application to the outside of MSL insulation layer But as temperature increases beyond 10$0^{\circ}C$, the sensor composition should be adjusted for the application to KNGR is to be made at temperature above 10$0^{\circ}C$.

• Nuclear Engineering and Technology
• /
• 제41권8호
• /
• pp.1015-1024
• /
• 2009

The presence of a non-condensable gas can considerably reduce the level of condensation heat transfer. The non-condensable gas effect is a primary concern in some passive systems used in advanced design concepts, such as the Passive Residual Heat Removal System (PRHRS) of the System-integrated Modular Advanced ReacTor (SMART) and the Passive Containment Cooling System (PCCS) of the Simplified Boiling Water Reactor (SBWR). This study examined the capability of the Multi-dimensional Analysis of Reactor Safety (MARS) code to predict condensation heat transfer in a vertical tube containing a non-condensable gas. Five experiments were simulated to evaluate the MARS code. The results of the simulations showed that the MARS code overestimated the condensation heat transfer coefficient compared to the experimental data. In particular, in small-diameter cases, the MARS predictions showed significant differences from the measured data, and the condensation heat transfer coefficient behavior along the tube did not match the experimental data. A new method for calculating condensation heat transfer coefficient was incorporated in MARS that considers the interfacial shear stress as well as flow condition determination criterion. The predictions were improved by using the new condensation model.

• Nuclear Engineering and Technology
• /
• 제30권5호
• /
• pp.435-443
• /
• 1998

Leak-before-break(LBB) approach has been shown to be both cost effective and risk reductive when applied to high energy Piping in nuclear Power Plants. For the Korean Next Generation Reactor (KNGR) development, LBB application is considered for the Main Steam Line(MSL) piping inside containment. Unlike the primary system leakages, the MSL leak detection systems must be based on principles other than radioactivity measurements. Among humidity, heat and acoustic noise currently being considered as indicators of leakage, we explored humidity as an effective one and developed ceramic-based humidity sensor which can be qualified for LBB applications. The ceramic material, sintered and annealed MgCr$_2$O$_4$-TiO$_2$, is shown to increase its electrical conductivity drastically upon water vapor adsorption over the entire temperature range of interest. With this ceramic sensor specimen, we suggested installation-inside-the-piping method by which we can detect leakage more rapidly and sensitively. In this paper, we describe the progress in the development and characterization of ceramic humidity sensor for the LBB application to the MSL of KNGR.

• Nuclear Engineering and Technology
• /
• 제55권4호
• /
• pp.1518-1527
• /
• 2023

A method was proposed for in-situ evaluating the thickness and resistivity of the oxide/hydroxide film formed on the surface of aluminum alloy exposed to sump water formed in the containment after a loss-of-coolant accident. The evaluation entailed fitting a model for the film impedance, which has film thickness and other variables describing the resistivity profile of the film along its thickness direction as fitting parameters, to the practically measured electrochemical impedance data. The obtained resistivity profiles implied that the films formed at pHs_25℃ 7, 8, 9, 10, and 11 all had a duplex structure; compared to the outer layer in contact with the solution, the inner layer of the film had a much higher resistivity and was inferred to be denser and provide most of the protectiveness of the film. Both the thickness and the total resistance of the film decreased with the increasing solution pH_25℃, suggesting that the films formed in more alkaline solutions had less protectiveness against corrosion, consistent with the increasing aluminum alloy corrosion rates previously identified.

• Nuclear Engineering and Technology
• /
• 제16권3호
• /
• pp.141-154
• /
• 1984

고리 1호기의 소형파단냉각재 상실사고에 의해 개시된 중대사고 유형과 그 현상에 대할 분석이 제시되었다. 본 해석에서는 KAERI에서 기존 전산코드의 수정.보완된 MARCH 전산코드가 사용되었다. 특히 고리 1호기의 소형파단 LOCA 해석시 수소 거동과 중기과압에 대한 평가 및 그 응답성에 중점을 두고 검토되었으며, 2-loop 발전소 데이타 분석 및 debris-Water 상호작용 모델에 대한 비교 분석이 수행되었다. 제 1부 중대 사고유형 분석결과, 저농도에서 H$_2$ burning이 이루어지는 경우 계속적인 수소 생성으로 인해 반복 수소 spike가 야기 되나, 격납용기 설계압력치 보다낮게 예측되었다. 또한 debris/water 상호작용시 core debris의 입자크기는 첨두압력의 크기에 미치는 영향은 미세하나 첨두압력의 발생시점은 dryout모델사용에 의해서 상당히 지연시키게 되었다. 완전한 노심용융 사고시 수소연소와 증기과압으로부터 예측된 격납용기 최대압력은 격납용기 건전성에 심각한 위협을 초래하지 않는 것으로 나타났다.

• 대한기계학회논문집A
• /
• 제38권4호
• /
• pp.355-361
• /
• 2014

신규 원전에서 추진중인 외벽침수냉각 방식의 적용이 실패할 경우 노심용융물과 원자로공동 내유체의 상호작용으로 인해 증기폭발이 발생하며, 이는 격납건물 및 관통부 배관을 포함한 각 구조물의 건전성을 위협할 수 있다. 본 논문에서는 선행연구 분석결과를 토대로 증기폭발 현상을 모사할 수 있는 개선된 해석기법을 도출하고 알루미나 실험 모사를 통해 타당성을 확인하였다. 또한 동일한 기법을 원자로공동 해석에 적용하여 가상 파손위치에 따른 증기폭발 압력이력을 예측하였으며, 측면파손에 의한 최대압력 값이 하부파손에 의한 것보다 최대 70% 정도 높음을 보였다.

• Nuclear Engineering and Technology
• /
• 제50권5호
• /
• pp.627-638
• /
• 2018

This article describes an integrated Level 1-Level 2 probabilistic risk assessment (PRA) methodology to evaluate the radiological risk during postulated accident scenarios initiated during the decommissioning phase of a typical Mark I containment boiling water reactor. The fuel damage scenarios include those initiated while the reactor is permanently shut down, defueled, and the spent fuel is located into the spent fuel storage pool. This article focuses on the integrated Level 1-Level 2 PRA aspects of the analysis, from the beginning of the accident to the radiological release into the environment. The integrated Level 1-Level 2 decommissioning PRA uses event trees and fault trees that assess the accident progression until and after fuel damage. Detailed deterministic severe accident analyses are performed to support the fault tree/event tree development and to provide source term information for the various pieces of the Level 1-Level 2 model. Source terms information is collected from accidents occurring in both the reactor pressure vessel and the spent fuel pool, including simultaneous accidents. The Level 1-Level 2 PRA model evaluates the temporal and physical changes in plant conditions including consideration of major uncertainties. The goal of this article is to provide a methodology framework to perform a decommissioning Probabilistic Risk Assessment (PRA), and an application to a real case study is provided to show the use of the methodology. Results will be derived from the integrated Level 1-Level 2 decommissioning PSA event tree in terms of fuel damage frequency, large release frequency, and large early release frequency, including uncertainties.

• 한국해양공학회지
• /
• 제12권1호
• /
• pp.50-57
• /
• 1998

The leak before break(LBB) concept is generalized on the design of LNG tanks, pressure vessels and nuclear reactor in that any leakage of containment, in whatever amount, will not result in catastropic failure. For this purpose it is necessary to determine the surface crack shape, the opening displacement and the risk of catastropic brittle fracture when it becomes a through crack. In this study the crack propagation behavior of surface flaws and the crack opening displacement of through cracks under combined membrane and bending stresses were investigated with fatigue tests and fracture toughness test of aluminium alloy A5083-O. And fracture mechanics analysis of the crack opening displacement of through cracks were made in order to develop a new model expressing the behaviors of COD under combined membrane and bending stresses.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2009년도 정기 학술대회
• /
• pp.287-290
• /
• 2009

이 논문에서는 가압중수형(Pressurized Heavy Water Reactor) 프리스트레스 콘크리트 격납건물의 1/4 축소모델에 대한 극한내압능력과 전반적인 비선형거동에 관한 유한요소 해석을 수행하였다. 가압중수형 격납건물은 원통형 벽체와 돔으로 구성되었고, 4개의 부벽을 갖는다. 유한요소해석을 위해서 상용코드 ABAQUS를 이용하였고, 콘크리트, 철근 및 텐던에 대한 수치모델링을 작성하여 자중과 내압하중을 적용하였고, 텐던의 2% 변형률을 기준으로 극한내압능력을 평가하였다. 이때 사용된 재료모델로 콘크리트는 Concrete Damaged Plasticity 모델을 사용하였고, 철근과 텐던은 Elasto-Plastic 모델을 적용하였다. 유한요소 해석결과 콘크리트의 초기균열 0.41MPa에서 발생하였고, 극한내압은 0.56MPa 정도로 평가되었다.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2012년도 추계 학술논문 발표대회
• /
• pp.193-194
• /
• 2012

Construction work is affected by the weather; e.g. snowfall, rainfall and low-high ambient temperature, especially at a site in a severe climate. The influence of the weather is one of the possible reasons for delays in a construction schedule and quality deterioration. To protect the worksite from severe weather conditions, the temporary roof and wall could be installed on the outside of main structures designed in advance and the temporary structures could be took down after a period use. The greater coverage all-weather construction method is applied, the larger the effect. so, it is important and needs that the temporary roof and wall can be widely applied, designed to effectively about structure and layout.