The effect of various physicochemical processes, such as seawater intrusion, on the performance of the engineered barrier should be closely analyzed to precisely assess the safety of high-level radioactive waste repository. In order to evaluate the impact of such processes on the performance of the engineered barrier, a thermal-hydrological-chemical model was developed by using COMSOL Multiphysics and PHREEQC. The coupling of two software was achieved through the application of a sequential non-iterative approach. Model verification was executed through a comparative analysis between the outcomes derived from the developed model and those obtained in prior investigations. Two data were in a good agreement, demonstrating the model is capable of simulating aqueous speciation, adsorption, precipitation, and dissolution. Using the developed model, the geochemical evolution of bentonite buffer under a general condition was simulated as a base case. The model domain consists of 0.5 m of bentonite and 49.5 m of granite. The uraninite (UO2) was assigned at the canister-bentonite interface as the potential source of uranium. Assuming the lifetime of canister as 1,000 years, the porewater mixing without uranium leakage was simulated for 1,000 years. After then, the uranium leakage through the dissolution of uraninite was initiated and simulated for additional 1,000 years. In the base case model, where the porewater mixing between the bentonite and granite was the only considered process, the gypsum tended to dissolve throughout the bentonite, while it precipitated in the vicinity of bentonite-granite boundary. However, the precipitation and dissolution of gypsum only showed a limited effect on the performance of the bentonite. Due to the low solubility of uraninite in the reduced environment, only infinitesimal amounts of uranium dissolved and transported through the bentonite. Additional cases considering various environmental processes, such as seawater or cement porewater intrusion, will be further investigated.

Since the first operation of the Gori No. 1 nuclear power plant in Korea was started to operate in 1978, currently 24 nuclear power plants have been being operated, out of which 21 plants are PWR types and the rest are CANDU types. About 30% of total electricity consumed in Korea is from all these nuclear power plants. The accumulated spent nuclear fuels (SFs) generated from each site are temporarily being stored as wet or dry storage type at each plant site. These SFs with their high radiotoxicity, heat generating, and long-lived radioactivity are actually the only type of high-level radioactive waste (HLW) in Korea, which urgently requires to be disposed of in deep geological repository. Studies on disposal of HLW in various kind of geological repositories have been carried out in such countries as Sweden, Finland, United States, and etc. with their own methodologies and management policies in consideration of their situations. In Korea long-term R&D research program for safe management of SF has also been conducted during last couple of decades since around 1997, during which several various alternative type of disposal concepts for disposal of SNFs in deep geological formations have been investigated and developed. The first concept developed was KAERI Reference Disposal System (KRS) which is actually very much similar to Swedish KBS-3, a famous concept of direct disposal of SF in stable crystalline rock at a depth of around 500 m which has been regarded as one of the most plausible method worldwide. The world first Finnish repository which is expected to begin to operate sooner or later will be also this type. Since the characteristics of SF discharged from domestic nuclear reactors have been changed and improved, and burnup has sometimes increased, a more advanced deep geological repository system has been needed, KRS-HB (KRS with High Burnup SF) has been developed and in consideration of the dimensions of SNFs and the cooling period at the time point of the disposal time, KRS+, a rather improved disposal concept has also been subsequently developed which is especially focused on the efficient disposal area. Recently research has concentrated on rather advanced disposal technology focused on a safer and more economical repository system in recent view of the rapidly growing amount of accumulated SF. Especially in Korea the rock mass and the footprint area for the repository extremely limited for disposal site. Some preliminary studies to achieve rather higher efficiency repository concept for disposal of SF recently have already been emphasized. Among many possible ones for consideration of design for high-efficiency repository system, a double-layered system has been focused which is expected to maximize disposal capacity within the minimum footprint disposal area. Based on such disposal strategy a rather newly designed performance assessment methodology might be required to show long-term safety of the repository. Through the study some prerequisites for such methodological development has been being roughly checked and investigated, which covers FEP identification and pathway and scenario analyses as well as preliminary conceptual modeling for the nuclide release and transport in nearfield, far-field, and even biosphere in and around the conceptual repository system. Through the study such scenarios and models has been implemented to development of a safety assessment by utilizing GoldSim development tool for a rough quantitative comparison with existing disposal options and simple illustration purpose as well as for showing how to develop and implementation of the model to GoldSim templet.

Over the years, in the field of safety assessment of geological disposal system, system-level models have been widely employed, primarily due to considerations of computational efficiency and convenience. However, system-level models have their limitations when it comes to phenomenologically simulating the complex processes occurring within disposal systems, particularly when attempting to account for the coupled processes in the near-field. Therefore, this study investigates a machine learning-based methodology for incorporating phenomenological insights into system-level safety assessment models without compromising computational efficiency. The machine learning application targeted the calculation of waste degradation rates and the estimation of radionuclide flux around the deposition holes. To develop machine learning models for both degradation rates and radionuclide flux, key influencing factors or input parameters need to be identified. Subsequently, process models capable of computing degradation rates and radionuclide flux will be established. To facilitate the generation of machine learning data encompassing a wide range of input parameter combinations, Latin-hypercube sampling will be applied. Based on the predefined scenarios and input parameters, the machine learning models will generate time-series data for the degradation rates and radionuclide flux. The time-series data can subsequently be applied to the system-level safety assessment model as a time table format. The methodology presented in this study is expected to contribute to the enhancement of system-level safety assessment models when applied.

The deep geologic repository (DGR) concept is widely accepted as the most feasible option for the final disposal of spent nuclear fuels. In this concept, a series of engineered and natural barrier systems are combined to safely store spent nuclear fuel and to isolate it from the biosphere for a practically indefinite period of time. Due to the extremely long lifetime of the DGR, the performance of the DGR replies especially on the natural geologic barriers. Assessing the safety of the DGR is thus required to evaluate the impacts of a wide range of geological, hydrogeological, and physicochemical processes including rare geological events as well as present water cycles and deep groundwater flow systems. Due to the time scale and the complexity of the physicochemical processes and geologic media involved, the numerical models used for safety evaluation need to be comprehensive, robust, and efficient. This study describes the development of an accessible, transparent, and extensible integrated hydrologic models (IHM) which can be approved with confidence by the regulators as well as scientific community and thus suitable for current and future safety assessment of the DGR systems. The IHM under development can currently simulate overland flow, groundwater flow, near surface evapotranspiration in a modular manner. The IHM can also be considered as a framework as it can 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 illustrative examples.

To obtain confidence in the safety of disposal facilities for radioactive waste, it is essential to quantitatively evaluate the performance of the waste disposal facilities by using safety assessment models. Thus, safety assessment models require uncertainty management as a key part of the confidencebuilding process. In application to the numerical modelling, the global sensitivity analysis is widely employed for dealing with parametric and conceptual uncertainties. In particular, the parametric uncertainty can be effectively reduced by minimizing the uncertainty of critical parameters in the safety assessment model. In this paper, the numerical model of each step disposal facility (Silo, Near surface, and Trench type) at Wolsong Low and Immediate Level Waste (LILW) Disposal Center is designed by using a two-dimensional finite element code (COMSOL Multiphysics). In order to determine the critical parameters for non-adsorbed nuclides such as H-3, C-14, Tc-99, we introduced the variance-based sensitivity analysis methodology of the global sensitivity analysis. In the case of Silo type, the density of waste is highly sensitive to the total leakage quantity of all nuclides. Additionally, the initial nuclide concentration of H-3 was identified as another important parameter of H-3. On the other hands, the mass transport coefficient showed a high contribution in C-14 and Tc-99. In other types of disposal facilities, the leaking properties of H-3 are significantly affected by the amount of infiltration water. However, C-14 and Tc-99 were found to be more sensitive to the density of waste.

The major issue in aircraft industry is aviation safety management because of demand improvement and advancement of the aircraft. This study is to assess the risks for aviation safety management using IRPN( importance-risk priority number) which is added to importance coefficient from RPN(risk priority number). In FMEA, RPN requires the factors like the occurrence (O), Severity (S), and Detection (D) of each failure mode to be precisely evaluated. Therefore, the severity and detection is derived by the value from FMEA of expert group based on the Fuzzy theory. The occurrence is calculated from the accident statistics of IATA(international air transport association) database. Particularly, this study introduces importance coefficient to prevent from RPN distortions. It is also derived from FMEA based on the Fuzzy theory. Finally, the critical ranking of risk factors according to I-RPN is compared with the existing research.

The occupational health and safety accidents were continuously increased during handling, usage and manufacturing the chemical materials according to increase of small and medium sized enterprises in domestic industries. These accidents mainly resulted from insufficient occupational health and safety management and deteriorative facilities and focused on corresponding operation to minimize the damage of accidents after occurrence. But, it was required that we grasped the occurrence causes of occupational health and safety risk in handling, usage and manufacturing the chemical materials and develop the adequate corresponding operation and system according to the possible occurrence of occupational health and safety risk. This study deals with the development of risk assessment model to derive the risk and important risk of occupational health and safety and then help to construct the self-controlled occupational health and safety system for small and medium sized enterprises handling the chemical materials.

해상교통안전진단제도가 도입된 이후 제도개선을 위한 노력은 계속되어 왔다. 이 제도가 정착단계를 거쳐 고도화 단계로 나아가기 위해서는 진단활동 전반에 대한 종합적이고 체계적인 검토가 필요하다. 이에 본 연구에서는 해상교통안전진단에 대한 종합적인 분석 모형 설계를 목적으로 진단수행의 질적 향상을 위한 수단으로 파악되는 평가에 대한 평가, 즉 메타평가에 관한 이론을 적용하였다. 구체적으로는 메타평가의 주요 접근방식인 문헌연구와 전문가 검토, 설문조사 등의 방법으로 해상교통안전진단에 적합한 메타평가 기본모형을 도출하고, 이에 대한 타당성과 신뢰성을 검증하여 활용 가능한 ‘PIP'OU 메타평가 모형’을 제시하였다. 본 모형은 해상교통안전진단제도에 대한 최초의 메타평가 모형으로써 향후 제도의 문제점 도출과 개선방안 마련을 위한 해상교통안전진단제도의 메타평가 분석틀로 활용될 수 있을 것으로 기대한다.

While a number of Korean companies have undergone ceaseless restructuring to survive today's rapidly changing global economy, the brick and mortar industry has been exerting their efforts to enhance the productivity through the development of new products, quality improvement, cost reduction measures. At present, various risk-evaluation measures have been taken in the fields at the discretion of an enterpriser, though, the effective methods enabling quantitative analysis are insufficient. Accordingly, this study is intended to contribute to the synthetic safety manage -ment in the factory fields and to suggest the quantitative -risk-analysis system by introducing such safety-estimation steps as assortment of processes, pre-assessment of risk factors, decision of risks, counter measures against studied risks, establishment of remedies.

The numerical model was developed to estimate the transient behavior of pressure waves in pipe systems. The computational algorithm was proposed to model the water hammer phenomenon in a pipe system with pump shutdown at midstream and sudden valve closure at downstream. To predict the pressure head and the flow velocity as a function of time as a result of rapidly closing a valve and pump shutdown, two boundary conditions at the ends considering pump operation and valve control can be implemented as specified equations of the pressure head and flow velocity based on the characteristics method. It was shown that the effects of transient flow make it determine the needs for protection devices, such as surge tanks, surge relief valves, or air valves, at various points in the system against overpressure and low pressure. It produced reasonably good performance with the results of the proposed transient model for pipeline systems. The proposed numerical model can be used as an efficient tool for the safety assessment of hydropower plants due to water hammer.

Although Korea coastal area has the increasing potential marine accident due to frequent ship’s encounter, increased vessel traffic and large vessel, there is no specific model to evaluate the navigating vessel’s risk considering the domestic traffic situation. The maritime transport environmental assessment is necessary due to the amended maritime traffic law. However, marine safety diagnosis is now carried out by foreign model. In this paper, therefore, we suggest a domestic traffic model reflecting the characteristics of korea coastal area and navigator’s risk as we named PARK(Potential Assessment of Risk) model. We can evaluate the subjective risk by establishing the model and model output into maritime risk exposure system. To evaluate this model’s effectiveness, we used ship handling simulation and applied, analyzed collision accident which occurred in korea coastal area. And also, we applied integrated to an ECDIS program for monitoring traffic risk of vessels with real time based AIS data and apply to evaluate traffic risk in busan harbor waterway. As a result, we could evaluate busan harbor waterway risk effectively.

해상교통안전진단제도가 해사안전법(구. 해상교통안전법)에 명시(2009. 5. 27)되어 제도적 기반을 구축한 이후 개선을 위한 지속적인 노력은 계속되어 왔으나 아직까지 제도의 고도화를 위한 종합적이고 체계적인 검토가 이루어지지 못하고 있는 실정이다. 이에, 본 연구는 메타평가에 관한 이론을 토대로 설계된 해상교통안전진단제도의 메타평가 분석틀, 즉 'PIP'OU 메타평가 모형'을 적용, 진단활동 전반에 대한 메타평가를 실시하여 현황 및 문제점을 분석하고 개선방안을 제시하였다. 그 결과, 진단 관련자들은 진단활동 자체가 제도의 목적에 부합하고 있으나 운영 측면은 미흡하여 '진단계획' 영역을 중심으로 개선이 필요하고 특히, 관련 이해당사자간 시각차를 최소화 할 수 있는 방안을 함께 고려하여야 하는 것으로 분석되었다. 본 연구는 제도 개선사항의 시급성을 정량화하여 우선순위를 제안함으로써 향후 관련 정책의 체계적인 개선에 활용될 수 있을 것으로 기대한다.

최근 해상교통 안전성 평가의 주요 기법으로 부각되고 있는 “환경 스트레스 모델”을 구성하는 두 요소 중, 본선 주변의 지형적인 제약에 기인하는 조선 환경 스트레스 모델의 개념과 특성에 대해 살펴보고, 이러한 기법을 항만이나 항로의 설계시 그 안전성 평가에 어떻게 활용할 수 있는가에 대하여 고찰해 보았다. 본 모델을, 가상적인 몇 가지 경우에 적용함으로써 그 개념과 특성을 보다 명확하게 고찰하고자 하였으며, 또한 부산항, 광양항 등 우리나라 주요 항만의 실제 접근 항로에 적용하여 보았다. 본 기법은, 항만이나 항로의 설계 및 그 안전성 평가에 큰 도움이 될 수 있을 것으로 판단된다.