PURPOSES : According to government data, the Black Spot Program has resulted in an average 28.8% reduction in traffic accidents within one year of project implementation in areas where road conditions improved. However, there has been a lack of in-depth analysis of the midto- long-term effects, with a predominant focus on short-term results. This study aimed to analyze the mid-to-long-term effects of the Black Spot Program to assess the sustainability of its reported short-term impact. Additionally, the differences in the mid-to-long-term effects were investigated based on the scale of traffic accidents at intersections and the characteristics of these effects are revealed. METHODS : The mid-to-long-term effects of the Black Spot Program were analyzed at 122 intersections in Seoul, Korea, where the program was implemented between 2013 and 2017, using traffic accident data spanning five years before and after implementation. Additionally, the differences in the program's effects were analyzed at the top-100 intersections with the highest traffic accident concentration in Seoul using the chi-square test to identify these differences. To theoretically validate these differences, the Hurst exponent, commonly used in economics, was applied to analyze the regression to the mean of the intersections and reveal the correlation with improvement. RESULTS : Through the Black Spot Program at 122 intersections, a 33.3% short-term accident reduction was observed. However, the midto- long-term effect analysis showed a 25.8% reduction, indicating a slightly smaller effect than previously reported. Specifically, the top-100 intersections exhibit a 15.4% reduction. A chi-square test with a 95% confidence level indicated significant differences in the program’s effects based on the scale of traffic accidents at intersections. The Hurst index (H ) was measured for the top-100 intersections, yielding H = 0.331. This is stronger than the overall H = 0.382 for all intersections in Seoul, suggesting that the regression to the mean is more pronounced, which may lead to a lower effectiveness of the improvement. CONCLUSIONS : The mid-to-long-term effects of the Black Spot Program were relatively lower than its short-term effects, with larger differences in effectiveness observed based on the scale of traffic accidents at intersections. This indicates the need to redefine the criteria for selecting project targets by focusing on intensive improvements at intersections, where significant effects can be achieved.

Researching and estimating the ecological characteristics of target fish species is crucial for fisheries resource management. The results of these estimates significantly influence stock assessments and management reference points such as size limit and closed seasons. Recently, ecological characteristics have been changing due to overfishing, climate change, and marine pollution, making continuous estimation and monitoring essential. This study analyzed the ecological changes in small yellow croaker (Larimichthys polyactis) resources in Korea over 24 years (2000-2023) using biological data (growth and gonad traits). By estimating the annual length-weight relationship and length at maturity (L50 and L95), we interpreted the numerical trends of early maturation due to resource depletion. The parameter b of the length-weight relationship, indicating the nutritional status of the resources, showed a slight increase over the years, suggesting relatively good nutritional status (b > 3.0) during most periods. Trend analysis between length at maturity and biomass indicated that as biomass decreased, maturity length also decreased.

진해만은 우리나라 남해 연안의 주요 어장으로서, 여전히 전체 수산생산량에서 적지 않은 기여를 창출하고 있다. 그러나, 수십 년간 산업개발과 고수온과 같은 환경변화로 인하여 진해만의 해양생태계는 과거와 달라지고 있다. 본 연구는 2005년부터 2022년 까지 진해만 연안 5개 시군구의 수산생산량, 폐기량, 평균영양단계 및 어업균형지수를 분석하였으며, ARIMA 모델을 이용하여 2027년까 지 단기적인 변동 추세를 함께 관찰하였다. 그 결과, 고성지역은 2027년까지 지속적으로 수산생산량이 감소할 것으로 예측되었다. 통영 지역은 이매패류의 부산물 처리가 필요한 것으로 평가된다. 해양생태계 지표의 경우, 통영지역에서는 대형 어류 생산 비중이 회복되고, 어업균형지수가 0 이상을 나타내어 해양생태계 구조가 안정적인 것으로 나타났다. 마지막으로 IPCC의 기후변화 시나리오에 따라 2060 년까지 진해만의 부어성 어종 6종의 생산량 변동 추이를 비교하였으며, 2020년대 초반 2만 ton 부근까지 감소했던 생산량은 2020년대와 2040년대에 4만 ton 부근 가까이 회복한 후, 2060년까지 점진적인 감소 경향을 나타내는 것으로 예측되었다.

생태계서비스 상쇄 효과(Trade-off) 규명과 같이 서비스 간 상호관계를 측정하는 것은 한정된 환경자원을 관리하는 측면에서 매우 중요하다. 이에, 본 연구에서는 약 30여 년간 토지 피복이 변화함에 따라 파생된 생태계서비스 우세경향 및 증감을 파악하고, 시간의 경과에 따라 발생한 생태계서비스 상호 간 관계 변화를 추적하였다. 이를 통해 토지 피복 변화와 생태계서비스 변화 간의 관계 및 지역마다 상이한 서비스 변화의 특성을 규명하였다. 연구는 생태계서비스 평가 모델인 InVEST Model을 주로 활용하였고, 평가결과를 0-1사이로 표준화한 후 차원축소기법 중 하나인 주성분 분석을 거쳐 시계열변화를 관찰하고 서비스 상호 간 관계를 파악하였다. 연구 결과, 시가화 지역 면적은 1989년에서 2019년 사이 급격하게 증가했으며, 산림은 2009년에서 2019년 사이 크게 증가하는 양상을 나타냈다. 1989년에서 2019년 사이에 생태계서비스 공급량에 있어 전국적으로 수량 공급은 13.9% 감소, 질소 저류는 10.5% 감소, 인 저류는 2.6% 증가, 탄소 저장은 0.9% 감소, 대기정화는 1.2% 증가, 서식처 질은 3.4% 감소하였다. 우리나라는 지난 30여 년간 시가화 지역이 증가하고, 농경지가 감소하며, 산림이 증가하는 동안 인 저류 기능과 서식처 질 사이에 상쇄 효과를 보였다. 본 연구는 우리나라의 환경관리 정책이 도시화로 인해 하락한 생태계 질을 향상시키고 생태계서비스를 극대화하는데 기여했다는 결론을 도출하였다. 이러한 연구 결과는 정책결정자들이 지속 가능한 자연환경 보전과 생태계 서비스 제공에 중점을 둔 조림 정책을 수립하고 추진하는 데 도움을 줄 수 있다.

In this research, a detailed analysis of the decay heat contributions of both actinides and non-actinides (fission fragments) from spent nuclear fuel (SNF) was made after 50 GWd·tHM−1 burnup of fresh uranium fuel with 4.5% enrichment lasted for 1,350 days. The calculations were made for a long storage period of 300 years divided into four sections 1, 10, 100, and 300 years so that we could study the decay heat and physical disposal ratios of radioactive waste in medium- and long-term storage periods. Fresh fuel burnup calculations were made using the code MCNP, while isotopic content and then decay heat were calculated using the built-in stiff equation solver in the MATLAB code. It is noted that only around 12 isotopes contribute more than 90% of the decay heat at all times. It is also noted that the contribution of actinides persists and is the dominant ether despite decreasing decay heat, while the effect of fission products decreases at a very rapid rate after about 40 years of storage.

In order to ensure the long-term safety of a deep geological repository, the performance assessment of the Engineered Barrier System (EBS) considering a thermal process should be performed. The maximum temperature at the side wall of a disposal canister for the technical design requirement should not exceed 100°C. In this study, the thermal modelling was conducted to analyze the effects of the thermal process from a disposal canister to the surrounding near-field host rock using the PFLOTRAN code. The mesh was generated using the LaGriT code and the material properties were assigned by applying the FracMan code. Initial conditions were set as the average geothermal gradient (25.7°C/km) and an average surface temperature (14.7°C) in Korea. The highest temperature was observed at the middle of the canister side wall. The temperature of the buffer was lower than that of the canister, and the temperature increase of the deposition tunnel and the host rock was insignificant due to the lower effect of the heat source. The result of the thermal evolution of the EBS represented the highest thermal effects in the vicinity of the canister. In addition, the thermal effects were largely decreased after 10 years of the entire simulation period. It demonstrated that the model took 3 years to heat up the buffer around the canister. The temperature at the canister side wall increased until 3 years and then decreased after that time. This is because that the radioactive decay heat from the heat source was emitted enough to raise the overall temperature of the EBS by 3 years. However, the decay heat rate of the canister decreased exponentially with the disposal time and then its decay heat was not emitted enough after 3 years. In conclusion, the peak temperature results of the EBS were lower than 70°C to meet the technical design requirement.

A methodology is under development to reconstruct and predict the long-term evolution of the natural barrier comprising the site of radioactive waste disposal. The natural barrier must protect the human zone from radionuclides for a long time. So for this, we need to be able to restore the evolution of the bedrock constituting the natural barrier from the past to the present and to predict from the present to the future. A methodology is being studied using surface outcrop, tunnel face of KURT (KAERI Underground Research Tunnel), and drill core at KAERI (Korea Atomic Energy Research Institute). Among them, drill core is an essential material for identifying deep geological properties, which could not be confirmed near the surface when considering the geological condition of the repository in the deep part. In this study, we selected several qualitative and quantitative analyses to construct a deep lithological model from the disposal perspective. These were applied to drill core samples around the KURT. There are the dikes presumed the Cretaceous were intruded by Jurassic granitoids in the study area. Analyzing trace elements of each rock type in the study area classified through geochemical characteristics and microstructure in previous studies made it possible to obtain qualitative information on the petrogenetic process. In addition, synthesizing the quantitative numerical age allows for grasping the evolution of bedrock, including intrusion and cutting relationships. LAICPMS was used for determining the age of zircons in plutonic rocks. The highly reliable 40Ar-39Ar method was selected for volcanic rocks because it can correct the loss of Ar gas and obtain the values of two types of Ar isotopes in a single sample. As a result, it was possible to infer the formation environment of rocks through anomalies in specific trace element content. And according to the numerical ages, it was possible to support the known separated rock type found in previous studies or to present a quantitative precedence relation for unclassified rocks. These methods could be applied to reconstruct the long-term evolution of bedrock within natural barriers.

해양사고 예방을 위해서는 사고의 원인과 결과에 대한 분석 및 진단뿐만 아니라, 사고의 발생 패턴과 변화 추이를 예측함으로 써 정량적 위험도를 제시할 필요성이 있다. 선박교통과 관련된 해양사고 예측은 선박의 충돌위험도 분석 및 항해 경로 탐색 등 선박교통 의 흐름에 관한 연구가 주로 수행되었으며, 해양사고의 발생 패턴에 대한 분석은 전통적인 통계 분석에 따라 제시되었다. 본 연구에서는 해양사고 통계 자료 중 선박교통관련 사고의 월별, 시간대별 발생 현황 데이터를 활용하여 해양사고 발생 예측 모델을 제시하고자 한다. 국내 해양사고 발생 현황 중 월별, 시간대별 데이터 집계가 가능한 1998년부터 2021년까지의 통계자료 중 선박교통 관련 데이터를 분류하 여 정형 시계열 데이터로 변환하였으며, 대표적인 인공지능 모델인 순환 신경망 기반 장단기 기억 신경망을 통하여 예측 모델을 구축하 였다. 검증데이터를 통하여 모델의 성능을 검증한 결과 RMSE는 초기 신경망 모델에서 월별 52.5471, 시간대별 126.5893으로 나타났으며, 관측값으로 신경망 모델을 업데이트한 결과 RMSE는 월별 31.3680, 시간대별 36.3967로 개선되었다. 본 연구에서 제안한 신경망 모델을 기 반으로 다양한 해양사고의 특징 데이터를 학습하여 해양사고 발생 패턴을 예측할 수 있을 것이다. 향후 해양사고 발생 위험의 정량적 제 시와 지역기반의 위험지도 개발 등에 관한 추가 연구가 필요하다.

본 연구에서는 칠발도, 거문도, 동해에서 20년 이상 관측된 파랑자료를 16 방위별 극치확률분석을 통해 재현빈도별 심해설 계파를 산정하였고, 이 값을 방향을 고려하지 않은 전방향파의 심해설계파와 비교하였다. Weibull 분포함수를 확률분포함수로 사용하였 으며, 최소자승법을 사용해서 매개변수를 결정하였다. 추정된 분포함수는 Kolmogorov-Smirnov 방법을 사용하여 적합도를 검증하였다. 그 결과 방향별로 구한 심해설계파가 전방향파의 심해설계파보다 모든 방향에서 상대적으로 작은 것으로 나타났다. 파향별로 구한 50년 빈도 설계파고는 칠발도, 거문도, 동해에서 각각 7.46 m(NNE), 12.05 m(S), 9.69 m(SSW)가 최대값이지만, 전방향파로 구한 설계파고는 각각 7.91 m, 13.82 m, 10.38 m이었다. 이는 현재 해양 및 연안 구조물 설계에 사용하고 있는 16 방위별 심해설계파고가 과소산정되었을 가능 성이 있음을 보여준다.

During the normal operation boron concentrates and spent resins are generated. The boron concentrates are treated by concentrated waste drying system (CWDS) and results in fine powder form. The solidification or application of high integrity container (HIC) is required for the disposal of the dried boron concentrates. The spent resin is stored in storage tank after the water treatment. The spent resin also requires solidification or application of HIC to satisfy the waste acceptance criteria (WAC) in Korea. The solidification process requires periodic validation. The repeated validation and complicated process hesitates the practical application. The application of HIC offers various advantages, including flexible free standing water requirement, higher waste loading compared to solidification, and simple process. The polymer concrete (PC), which is a primary component for PC-HIC exhibits good material stability. The expected transportation mechanism of nuclide in the PC-HIC are 1) diffusion by concentration, 2) permeation by pressure, and 3) capillary suction when considering the disposal condition. Since the PC-HIC effectively prevents the intrusion of neighboring water and volume of free standing water is lower than 1%, it seems that diffusion by concentration is the primary transportation mechanism. In this study, the property of PC is investigated based on Cl ion diffusion test to evaluate the material reliability. The results indicate that PC exhibits superior stability compared to ordinary portland cement. In addition, the reliable life time of PC is estimated base on the element transportation phenomena.

Since it takes hundreds of thousands of years for the radiotoxicity of spent nuclear fuel to decrease to natural levels, interactions between each repository barrier, climate change, and geological evolutions are inevitable. These processes should be defined as the long-term evolution FEPs and considered in the performance assessment to ensure the long-term safety of the disposal system. The literature survey on geological characteristics and history of the Korean peninsula was conducted, and the list of A-KRS-FEPs which are directly or indirectly related to long-term evolutions was identified in this study. The ice age and geological change are the capital phenomena considered in the exceedingly long-term evolution before/after climate change. The historical data on ice sheets and permafrost were analyzed to investigate the effects of the ice ages on the Korean peninsula. The sealevel changes were investigated based on the research on the coastal terrace to identify the impact on uplift and shoreline change accompanying the ice age. Also, the survey on the geological history data was conducted from the perspective of tectonic activity, metamorphism, igneous activity, and seismic activities to consider the geodynamic evolution of the Korean peninsula. As results, it was suggested that 14 FEPs were directly related to climate change, 18 FEPs were directly related to geological evolution, and 47 FEPs were indirectly relevant to long-term geodynamics. The consent-based FEPs and scenarios for the long-term evolution will be developed shortly, including most of the critical long-term evolution phenomena defined in this study and which are highly probable in domestic disposal conditions. The evaluation and verification of the APro system for long-term safety will accomplish using these FEPs and scenarios.

Deep geologic repositories (DGR) are designed to store spent nuclear fuel and to isolate it from the biosphere for an extended period of time as long as millions of years. The long-term performance of the DGR replies on the performance of the natural geologic barriers after the end of the lifetime for the engineered barrier systems. Typically, multiple analytical and numerical models are used to analyze and ensure the safety of the repositories along both engineered and natural barrier systems. Despite the immense advancement in computing power and modeling techniques over the last few decades, a series of models and their linkage often require many simplifying assumptions in this safety assessment. The degree of the reliability and confidence of the safety analysis is thus highly dependent on the validity of those tools used. Considering the significance of the DGR performance and public attention, the highest level of quality control is necessary for the models employed in the assessment. The performance of the ultimate long-term geologic barrier is determined by the expected travel time of the radioactive species of interest, the level of their dilution or radioactivity at compliance areas, and the uncertainty associated with them. As the species of interest can be carried away from the repository location by groundwater flow, the travel time is determined by groundwater velocity along the flow path from source to biosphere while the dilution is a function of the decay and production rates as well as the diffusion and dispersion. Due to the time scale and the complexity of the physicochemical processes and geologic media involved, the models used for safety evaluation will need to become more and more comprehensive, robust, and efficient which is difficult to achieve in principle. They will also need to be transparent and flexible to satisfy the regulatory quality control requirements. This study thus attempts to develop an accessible, transparent, and extensible integrated hydrologic models (IHM) which can be widely accepted by the regulators as well as scientific community and thus suitable for current and future safety assessment of the DGR systems. The IHM can be considered as a tool and a framework at the same time when it is designed to easily accommodate additional processes and requirements for the future as it is necessary. The IHM is capable of handling the atmospheric, land surface, and subsurface processes for simultaneously analyzing the regional groundwater driving force and deep subsurface flow, and repository scale safety features, providing an ultimate basis for seamless safety assessment in the DGR program. The applicability of the IHM to the DGR safety assessment is demonstrated using simple illustrative examples.

초고층 건물에서 수평변위 제어와 수직부재에서 발생하는 부등축소에 대한 검토가 필수적이다. 이러한 부등축소는 비구조요소의 사용성과 구조요소의 안전성에 대해 문제를 야기할 수 있다. 따라서 이 연구에서는 120층 규모의 철근콘크리트 주거용 초고층 건물에 대해 시공단계해석을 수행하여 각 수직부재의 부등축소량을 비교하고 콘크리트의 장기거동의 영향을 분석하였다. 이를 위해 영향요 인에 따라 축소량을 탄성축소량, 크리프축소량, 건조수축축소량으로 구분하여 검토하였으며 최대 절대축소량에 대한 지배적 요인을 분석하였다. 또한, 입주완료 후 30년에서 발생한 부등축소량에 대해 사용성 검토를 진행하였으며, 구조요소에 대해 설계단계와 시공 단계의 부재력을 비교하여 분석하였다.

PURPOSES : In this study, the results of an intensive field survey of a composite pavement applied to an expressway in Korea are analyzed. The results are intended to be used as basic data for evaluating the composite pavement and for preparing quality control measures through a review and analysis of the change in the state of the tensile bonding strength of the composite pavement. METHODS : To evaluate, repeated field coring and indoor tensile bonding strength evaluations are conducted for five years, and the commonality evaluation of pavement using pavement condition investigation equipment is conducted annually. RESULTS : The results of this study show that the degree of reflective crack generation varies depending on the type of concrete pavement and type of asphalt mixture applied to the intermediate layer, and that the CRCP composite pavement exhibits better initial commonality than the JCP composite pavement. In addition, it is confirmed that the composite cross-section pavement section with MASTIC applied as an intermediate layer shows excellent adhesion performance between the lower concrete layers from the beginning of construction in all sections, as well as satisfied the quality control standards for good pavement and tensile adhesion even after approximately five years of public use. CONCLUSIONS : Based on a follow-up survey of the composite pavement testing sections, it is confirmed that the section constructed with the MASTIC intermediate layer and CRCP satisfies the quality control standards for good pavement conditions and tensile adhesion even after approximately five years of public use.