• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.1455-1456
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• 2004

• 한국지진공학회논문집
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• 제16권3호
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• pp.35-42
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• 2012

암반지반에 주어진 등재해도 스펙트럼에 상응하는 원전부지 토사지반에서의 등재해도 스펙트럼을 도출하기 위한 확률론적 방법론을 제시하였다. 이를 위해 지진 운동 및 지반의 불확실성을 고려한 지반응답 해석을 통해 토사지반 지표에서의 지진동 증폭계수를 산정하였다. 증폭계수는 가장 상관관계가 높은 지반운동의 스펙트럴 가속도 규모와의 회귀분석을 통해 계산되었다. 이 방법론을 적용하여 국내 KNGR (Korean Next Generation Reactor) 및 APR1400 (Advanced Power Reactor 1400) 원전의 포괄부지 지반 중 B1, B4, C1 및 C3 지반을 대상으로 등재해도 스펙트럼을 도출하였다. 등재해도 스펙트럼을 통해 지진동 발생 빈도 별 위험 주파수 대역을 평가하고 분석하였다. 이 결과는 원전의 종합적 지진리스크 평가 결과를 보다 합리적으로 개선하는 데에 활용될 수 있으며, 향후 다양한 종류의 토사지반에 대한 등재해도 스펙트럼을 평가하는 데에 적용할 수 있을 것으로 기대된다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.189-190
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• 2005

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2529-2539
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• 2022

Stochastic and an empirical Green's function (EGF) methods are preliminarily applied to simulate strong ground motions (SGMs) at seismic stations within nuclear power plant (NPP) sites in South Korea by an assumed large earthquake with M_W6.5 (scenario earthquake) on the causative fault of the 2016 Gyeongju earthquake with M_W5.5 (mainshock). In the stochastic method, a ratio of spectral amplitudes of observed and simulated waveforms for the mainshock is assumed to be an adjustment factor. In the EGF method, SGMs by the mainshock are simulated assuming SGMs by the 2016 Gyeongju earthquake with M_W5.0 (foreshock) as the EGF. To simulate SGMs by the scenario earthquake, a ratio of fault length to width is assumed to be 2:1 in the stochastic method, and SGMs by the mainshock are assumed to be EGF in the EGF method. The results are similar based on a bias of the simulated response spectra by the two methods, and the simulated response spectra by the two methods exceeded commonly standard design response spectra anchored at 0.3 g of NPP sites slightly at a frequency band above 4 Hz, but considerable attention to interpretation is required since it is an indirect comparison.

• 한국방사선학회논문지
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• 제16권2호
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• pp.185-194
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• 2022

국제적으로 과거 원자력 및 방사선 관련 활동으로 인해 부지 및 토양 등이 오염된 레거시 부지에 대한 해결과 관리가 관심의 대상이 되고 있다. 국내에서도 연구로 해체 등의 사례가 있었으며 북한은 최신화된 안전규제가 적용되고 있지 않을 가능성이 있으며 관련하여 운영 기록 등의 관리되지 않고 있을 가능성이 있어 레거시 부지가 될 가능성이 크다. 따라서 본 연구에서는 레거시 부지의 해결에 대한 국제 사례를 검토하고 이로부터 레거시 부지의 특성과 문제점을 파악하였다. 이에 국제 관리 기준에 따른 레거시 부지 대응 절차와 규제 체계를 분석하고 규제 체계 개발 시 고려되어야 할 사항을 도출 하였다. 레거시 부지 대응 방안의 개발은 향후 레거시 부지 발생시 대응과 레거시 부지의 발생을 예방하는데 사용될 수 있다.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1255-1262
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• 2009

This paper introduces the status of and issues related to the PSHA (Probabilistic Seismic Hazard Analysis) of Korean Nuclear Power Plant sites. PSHA was first introduced to the nuclear industry in the mid-1980s. The Korean PSHA is based on Cornell and accommodates the modem approach for eliciting expertise and statistical treatment. Due to the low seismicity in Korea, large uncertainties exist in the PSHA database including seismic source maps, seismicity parameters of seismic sources, and attenuation formulae. Though research in seismology, geology, and earthquake engineering since the mid-1990s has significantly reduced uncertainties, a considerable amount still exists. Considering the low seismicity of the Korean Peninsula, especially the lack of strong motion data, further reduction will take several decades.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.30-35
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• 2022

In a nuclear reactor, gamma radiation is the dominant energy deposition in non-fuel regions. Heat is generated upon gamma deposition and consequently affects the mechanical and thermal structure of the material. Therefore, the safety of samples should be carefully considered so that their integrity and quality can be retained. To evaluate relevant parameters, an in-core gamma thermometer (GT) was used to measure gamma heating (GH) throughout the operation of the McMaster nuclear reactor (MNR) at four irradiation sites. Additionally, a Monte Carlo reactor physics code (Serpent-2) was utilized to model the MNR with the GT located in the same irradiation sites used in the measurement to verify its predictions against measured GH. This research aids in the development of modeling, calculation, and prediction of the GH utilizing Serpent-2 as well as implementing a new GH measurement at the MNR core. After all uncertainties were quantified for both approaches, comparable GH profiles were observed between the measurements and calculations. In addition, the GH values found in the four sites represent a strong level of radiation based on the distance of the sample from the core. In this study, the maximum and minimum GH values were found at 0.32 ± 0.05 W/g and 0.15 ± 0.02 W/g, respectively, corresponding to 320 Sv/s and 150 Sv/s. These values are crucial to be considered whenever sample is planned to be irradiated inside the MNR core.

• Nuclear Engineering and Technology
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• 제44권5호
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• pp.437-452
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• 2012

The Tohoku earthquake (Mw9.0) occurred on March 11, 2011 and caused a large tsunami. The Fukushima Dai-ichi NPP (F1-NPP) were overwhelmed by the tsunami and core damage occurred. This paper describes the overview of F1-NPP accident and the usability of tsunami PRA at Tohoku earthquake. The paper makes reference to the following current issues: influence on seismic hazard of gigantic aftershocks and triggered earthquakes, concepts for evaluating core damage frequency considering common cause failure with correlation coefficient against seismic event at multi units and sites, and concepts of "seismic-tsunami PSA" considering a combination of seismic motion and tsunami effects.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.366-372
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• 2020

Using several accessible published data sets, we analyzed the temporal change of ¹³⁷Cs radioactivity (per unit mass of sample) in marine sediments and investigated the effect of the water content of sediment on the ¹³⁷Cs radioactivity, to understand the behavior of ¹³⁷Cs present in marine environments. The ¹³⁷Cs radioactivity in sediments decreased more slowly in the Baltic Sea (near the Chernobyl nuclear power plant) than in the ocean near the Fukushima Daiichi nuclear power plant (FDNPP). The ¹³⁷Cs radioactivity in the sediment near the FDNPP tended to increase as the water content increased, and the water content decreased at certain sampling sites near the FDNPP for several years. Additionally, the decrease in the water content contributed to 51.2% of the average ¹³⁷Cs radioactivity decrease rate for the same period. Thus, it may be necessary to monitor both the ¹³⁷Cs radioactivity and the water content for marine sediments to track the ¹³⁷Cs that was discharged from the sites of Chernobyl and Fukushima nuclear power plants where severe accidents occurred.

• Nuclear Engineering and Technology
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• 제52권5호
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• pp.975-983
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• 2020

Since the Fukushima Daiichi accident in 2011, concerns for the safety of multi-unit Nuclear Power Plant (NPP) sites have risen. This is because more than 70% of NPP sites are multi-unit sites that have two or more NPP units and a multi-unit accident occurred for the first time. After this accident, Probability Safety Assessment (PSA) has been considered in many countries as one of the tools to quantitatively assess the safety for multi-unit NPP sites. One of the biggest concerns for a multi-unit accident such as Fukushima is that the consequences (health and economic) will be significantly higher than in the case of a single-unit accident. However, many studies on multi-unit PSA have focused on Level 1 & 2 PSA, and there are many challenges in terms of public acceptance due to various speculations without an engineering background. In this study, two kinds of multi-unit Level 3 PSA for multi-unit site have been carried out. The first case was the estimation of multi-unit risk with conservative assumptions to investigate the margin between multi-unit risk and QHO, and the other was to identify the effect of time delays in releases between NPP units on the same site. Through these two kinds of assessments, we aimed at investigating the level of multi-unit risk and understanding the characteristics of risk in a multiunit context.