Properties of bentonite, mainly used as buffer and/or backfill materials, will evolve with time due to thermo-hydro-mechanical-chemical (THMC) processes, which could deteriorate the long-term integrity of the engineered barrier system. In particular, degradation of the backfill in the evolution processes makes it impossible to sufficiently perform the safety functions assigned to prevent groundwater infiltration and retard radionuclide transport. To phenomenologically understand the performance degradation to be caused by evolution, it is essential to conduct the demonstration test for backfill material under the deep geological disposal environment. Accordingly, in this paper, we suggest types of tests and items to be measured for identifying the performance evolution of backfill for the Deep Geological Repository (DGR) in Korea, based on the review results on the performance assessment methodology conducted for the operating license application in Finland. Some of insights derived from reviewing the Finnish case are as follows: 1) The THMC evolution characteristics of backfill material are mainly originated from hydro-mechanical and/or hydrochemical processes driven by the groundwater behavior. 2) These evolutions could occur immediately upon installation of backfill materials and vary depending on characteristics of backfill and groundwater. 3) Through the demonstration experiments with various scales, the hydro-mechanical evolution (e.g. advection and mechanical erosion) of the backfill due to changes in hydraulic behavior could be identified. 4) The hydro-chemical evolution (e.g. alteration and microbial activity) could be identified by analyzing the fully-saturated backfill after completing the experiment. Given the findings, it is judged that the following studies should be first conducted for the candidate backfill materials of the domestic DGR. a) Lab-scale experiment: Measurement for dry density and swelling pressure due to saturation of various backfill materials, time required to reach full saturation, and change in hydraulic conductivity with injection pressure. b) Pilot-scale experiment: Measurement for the mass loss due to erosion; Investigation on the fracture (piping channel) forming and resealing in the saturation process; Identification of the hydro-mechanical evolution with the test scale. c) Post-experiment dismantling analysis for saturated backfill: Measurement of dry density, and contents of organic and harmful substances; Investigation of water content distribution and homogenization of density differences; Identification of the hydro-chemical evolution with groundwater conditions. The results of this study could be directly used to establishing the experimental plan for verifying performance of backfill materials of DGR in Korea, provided that the domestic data such as facility design and site characteristics (including information on groundwater) are acquired.

A variety of microorganisms are contained in the groundwater and surrounding environment at the depth of a deep geological repository, and could adversely affect the integrity and/or safety of the facility under certain thermal, hydraulic and chemical conditions. In particular, microbial activity (in the buffer and backfill) around the canister can cause corrosion of the canister through sulfide production by sulfate-reducing bacteria (SRB), and subsequently promote radionuclide release through the corroded part. Namely, this phenomenon is important in a perspective of performance assessment since it will have an impact on the post-closure exposure dose in the biosphere by accelerating radionuclide leakage into the near-field due to deterioration of the canister integrity In Finland, the performance assessment on microbial activity in buffer, backfill, and plug was performed for the licensing. However, in Korea, researches relevant to microbial activity are only in the early stage as of now. Accordingly, in this study, we draw initial considerations for the performance assessment on the phenomenon in the domestic facility based on review results for the methodology carried out as part of operating license application (i.e. SC-OLA). Studies on the performance assessment of microbial activity in Finland were mainly performed: (a) to investigate complex interactions among microorganisms in the repository by analyzing both indigenous and exogenous microorganisms through drilling, geological and geochemical analysis, (b) to identify microbial interactions at the buffer, backfill, and host rock interface for specific microorganisms that may affect activity of other microorganisms and integrity of the repository, (c) to analyze canister corrosion caused by microbial activity, particularly sulfide production by SRB, and (d) to characterize microbial illitization of montmorillonite that could affect permeability, hydraulic conductivity, and structural integrity of the repository. From reviewing studies above, it is judged that studies labelled as (b) through (d) are applicable to the performance assessment of microbial activity for the domestic facility regardless of specific conditions in Korea. However, for study labelled as (a), the following data on reflecting domestic conditions should be additionally obtained: (1) radionuclide inventory and temperature in spent nuclear fuel, (2) swelling pressure and organic carbon content of bentonite, and (3) size, shape, and gas composition of pores in bentonite. Results of this study could be directly applied to the design and performance assessment for buffer and backfill components, provided that input data specific to the domestic disposal facility is prepared for the assessment required.

We complete the survey for finite-source/point-lens (FSPL) giant-source events in 2016–2019 KMTNet microlensing data. The 30 FSPL events show a clear gap in Einstein radius, 9 μas < θE < 26 μas, which is consistent with the gap in Einstein timescales near tE ∼ 0.5 days found by Mr´oz et al. (2017) in an independent sample of point-source/point-lens (PSPL) events. We demonstrate that the two surveys are consistent. We estimate that the 4 events below this gap are due to a power-law distribution of freefloating planet candidates (FFPs) dNFFP/d logM = (0.4 ± 0.2) (M/38 M⊕)−p/star, with 0.9 ≲ p ≲ 1.2. There are substantially more FFPs than known bound planets, implying that the bound planet power-law index γ = 0.6 is likely shaped by the ejection process at least as much as by formation. The mass density per decade of FFPs in the Solar neighborhood is of the same order as that of ‘Oumuamua-like objects. In particular, if we assume that ‘Oumuamua is part of the same process that ejected the FFPs to very wide or unbound orbits, the power-law index is p = 0.89 ± 0.06. If the Solar System’s endowment of Neptune-mass objects in Neptune-like orbits is typical, which is consistent with the results of Poleski et al. (2021), then these could account for a substantial fraction of the FFPs in the Neptune-mass range.

In this study, a manual that can be applied to conflict management of clearance waste recycling by stakeholders was researched to recycle clearance waste that is most frequently generated when decommissioning nuclear power plants. In order to develop a manual that can be applied to conflict management, the content of the conflict should be derived first. In order to derive conflict, it is necessary to organize major issues in recycling clearance waste in consideration of domestic nuclear energy and social environment. In order to organize major issues in consideration of the domestic environment, a literature survey and a domestic current situation investigation were conducted. At this time, the subject of the major issue was selected based on the Level 1 influencing factors of the previous study. As a result of the investigation, it was confirmed that there were many major issues due to lack of reliability/understanding in nuclear energy/radiation. Through this Conflicts caused by recycling clearance waste were derived based on the organized issues. As a result of deriving conflicts, eight conflicts were derived below. 1) Reduced business availability due to lack of understanding/reliability 2) Lack of reliability in the selection and technology of nuclide analysis technology 3) Additional time and equipment required due to establishment of clearance waste regulatory requirements 4) Low economic benefits due to reduction in the effect of substituting raw materials 5) Political interference due to worsening public opinion 6) Rejection of final products due to recycling due to distrust of radiation 7) Public acceptance along the transport route from the source to the recycling plant 8) Business promotion deteriorated due to changes in energy policy As a result of the derived conflict analysis, the most conflicts related to lack of reliability/understanding in nuclear energy/radiation were derived. Accordingly, in future research, it is necessary to prepare a specific plan to enhance the understanding of stakeholders about self-disposal waste recycling. Considering that research that can solve the conflicts that will be faced when the domestic/foreign clearance waste recycling industry is activated is not activated, this study is meaningful in that it derived the conflicts that will be faced when recycling clearance waste. Also, it is expected that the conflicts derived from this study will be used meaningfully in the establishment of the clearance waste recycling management manual.

The decommissioning of Kori Unit 1 is expected to generate a large amount of clearance waste. Disposing of a large amount of clearance waste is economically costly, so a recycling method has emerged. However, clearance waste recycling is expected to cause many conflicts among various stakeholders. In the previous study, possible conflicts were selected in consideration of the domestic environment and major issues. Based on this, this study classifies stakeholders involved in conflicts by group, and suggests ways to enhance understanding by stakeholder and enhance reliability. In this study, stakeholders are classified into four groups that share the same conflicts, and each of the following measures is suggested. 1) Stakeholder Engagement. 2) Common understanding of radiation risks, dialogue between the public/recycling industry/ regulatory agency. 3) Incentives to promote recycling clearance waste. 4) Reliable outlet store for recyclable clearance waste. The above understanding enhancement measures are presented so that a solution to conflict can be smoothly derived when designing a clearance waste-related consultative body composed of interested parties in the future. As a more specific solution, measures to enhance stakeholder trust can be suggested for each understanding enhancement measure. Reliability enhancement measures are also presented so that they can be applied to each stakeholder group, and these are as follows. 1) Write a stakeholder engagement plan, Measures for stakeholder participation in measuring the radioactivity concentration of clearance waste. 2) Active use of easy-to-understand radioactivity comparison data, Expansion of information on environmental radiation dose to public, nuclear/radiation education, Held a tour event at the nuclear power plant decommissioning site, New website for clearance waste information disclosure. 3) Incentives for recycling industries in which the Ministry of Environment or KHNP partially bears the losses that occur when the sales rate is low. Incentives are provided to consumers by including recyclables of clearance waste for Green Card’s green consumption points. 4) Online outlets open for recyclable clearance waste with easy-to-understand radioactivity comparison data. It is expected that if the above-mentioned reliability enhancement measures are used, it will be possible to secure the trust of stakeholders and reduce the gap between stakeholders in the future clearance-related consultative body.

We present the analysis of a planetary microlensing event OGLE-2019-BLG-0362 with a shortduration anomaly (∼0.4 days) near the peak of the light curve, which is caused by the resonant caustic. The event has a severe degeneracy with Δχ2 = 0.9 between the close and the wide binary lens models both with planet-host mass ratio q ≃ 0.007. We measure the angular Einstein radius but not the microlens parallax, and thus we perform a Bayesian analysis to estimate the physical parameters of the lens. We find that the OGLE-2019-BLG-0362L system is a super-Jovian-mass planet Mp = 3.26+0.83 −0.58 MJ orbiting an M dwarf Mh = 0.42+0.34 −0.23 M⊙ at a distance DL = 5.83+1.04 −1.55 kpc. The projected star-planet separation is a⊥ = 2.18+0.58 −0.72 AU, which indicates that the planet lies beyond the snow line of the host star.

The decommissioning of Kori unit 1 is just around the corner. Accordingly, it is required to construct a hot cell facility for decommissioning nuclear power plants to analyze the characteristics of intermediate-level waste and low-level waste generated in the decommissioning process. In this study, a Design Base Accident (DBA) scenario of the facility is developed. To identify and characterize potential hazards at the facility, a Preliminary Fact Sheet (PFS) is filled out and consider external events in consideration of the surrounding site environment. The external event screening and evaluation method is based on the external event evaluation method covered in the probabilistic risk assessment. In PFS, only natural and artificial hazards that may have a meaningful impact on the facility are considered as the sources of the accident, and accident prevention and mitigation systems, etc., which exist in each compartment or facility, are described. Based on PFS and external events, potential hazard assessment is systematically performed using each potential hazards, impact and defense function identified using the preliminary hazard analysis (PHA) methodology. The potential hazard analysis methodology applied to this assessment is a qualitative assessment method consistent with the US DOE Hazard Analysis methodology (DOE 1992b; DOE 1994b). After that, the potential mitigation functions that can be used under normal, abnormal and accident conditions are examined, and the contribution of public and workers to safety is evaluated. The results of the PHA are basic data that prioritize potential hazards and can be used to develop potential accident scenarios. Among potential hazards generally considered for non-reactor facilities, only possible accidents during operation of the facilities are selected as potential hazards. The level of potential hazards is obtained by qualitatively examining the frequency and consequence estimates for each hazard or accident scenario developed in PHA. Based on the results of the potential hazards assessment, representative accidents that require further quantitative analysis are screened. Selected accidents are DBA and are the most dangerous and most significant impacts on workers.

인간의 평균수명 연장으로 일상생활을 수행하기 어려운 노인들은 개인의 욕구에 맞는 요양서비스를 필요로 하고 있으며, 노인의 신체활동이나 가사활동 등의 개별화된 서비스 를 제공하는 요양보호사의 일자리는 지속해서 증가하고 있다. 본 연구의 목적은 노인의 료복지시설의 요양보호사가 인지하고 있는 현재의 사회적 지지가 서비스 질에 미치는 영향을 분석하고, 직무만족과 직무스트레스의 매개효과를 검증하여 요양서비스 질을 향 상하는 것에 있다. 본 연구는 서울, 경기, 인천지역의 의료복지시설에 근무하고 있는 요양보호사 488명을 대상으로 하였으며, SPSS WIN 24.0과 AMOS 24.0 프로그램을 사용하여 분석하였다. 본 연구의 결과는 구조모형을 통해 연구 변인 간 영향 관계를 검증한 결과, 요양보호 사의 사회적 지지는 직무만족에 유의한 정(+)적 영향을 미쳤고, 직무스트레스에는 유의 한 부(-)적 영향을 미쳤다. 직무만족은 서비스 질에 유의한 정(+)적 영향을 미쳤고, 직무 스트레스는 서비스 질에 유의한 부(-)적 영향을 미쳤다. 또한 요양보호사의 사회적 지지 와 서비스 질 관계에서 직무만족은 매개역할을 하는 것으로 검증되었다. 따라서 요양보 호사의 사회적 지지는 직무만족을 매개하여 서비스 질에 간접적으로 영향을 미치는 것 으로 검증되었다. 본 논문은 요양보호사의 사회적 지지가 서비스 질에 미치는 영향에서 직무만족과 직 무스트레스의 매개효과를 검증함으로써 변수 간의 구조적 관계를 설명하고 요양보호사 의 사회적 지지가 요양서비스 질의 수준을 높여 요양보호 대상자들의 삶의 질을 향상하 는 실천적 방안을 마련하였다.

It is dicult for observers to conduct an optical alignment at an observatory without the assistance of an optical engineer if optomechanical parts are to be replaced at night. We present a prac- tical tilt correction method to obtain the optimal optical alignment condition using the symmetricity of optical aberrations of a wide-eld on-axis telescope at night. We conducted coarse tilt correction by visually examining the symmetry of two representative star shapes obtained at two guide chips facing each other, such as east{west or north{south pairs. After coarse correction, we observed four sets of small stamp images using four guide cameras located at each cardinal position by changing the focus positions in 10-m increments and passing through the optimum focus position in the range of 200 m. The standard deviation of each image, as a function of the focus position, was tted with a second-order polynomial function to derive the optimal focus position at each cardinal edge. We derived the tilt angles from the slopes converted by the distance and the focus position dierence between two paired guide chip combinations such as east{west and north{south. We used this method to collimate the on-axis wide-eld telescope KMTNet in Chile after replacing two old focus actuators. The total optical alignment time was less than 30 min. Our method is practical and straightforward for maintaining the optical performance of wide-eld telescopes such as KMTNet.

We report the discovery of a giant exoplanet in the microlensing event OGLE-2017-BLG-1049, with a planet―host star mass ratio of q = 9.53 ± 0.39 × 10-3 and a caustic crossing feature in Korea Microlensing Telescope Network (KMTNet) observations. The caustic crossing feature yields an angular Einstein radius of θE = 0.52 ± 0.11 mas. However, the microlens parallax is not measured because the time scale of the event, tE ≃ 29 days, is too short. Thus, we perform a Bayesian analysis to estimate physical quantities of the lens system. We find that the lens system has a star with mass Mh = 0.55+0.36 -0.29 M⊙ hosting a giant planet with Mp = 5.53+3.62 -2.87 MJup, at a distance of DL = 5.67+1.11 -1.52 kpc. The projected star{planet separation is aㅗ = 3.92+1.10 -1.32 au. This means that the planet is located beyond the snow line of the host. The relative lens{source proper motion is μrel ~ 7 mas yr-1, thus the lens and source will be separated from each other within 10 years. After this, it will be possible to measure the flux of the host star with 30 meter class telescopes and to determine its mass.

At q = 1.81 ± 0.20 × 10-5, KMT-2018-BLG-0029Lb has the lowest planet-host mass ratio q of any microlensing planet to date by more than a factor of two. Hence, it is the first planet that probes below the apparent "pile-up" at q = 5-10 ×10-5. The event was observed by Spitzer, yielding a microlens-parallax πE measurement. Combined with a measurement of the Einstein radius θE from finite-source effects during the caustic crossings, these measurements imply masses of the host Mhost = 1.14+0.10-0.12 M⊙ and planet Mplanet = 7.59+0.75-0.69 M⊕, system distance DL = 3.38+0.22-0.26 kpc and projected separation a⊥ = 4.27+0.21-0.23 AU. The blended light, which is substantially brighter than the microlensed source, is plausibly due to the lens and could be observed at high resolution immediately.

토지이용별로 토양 물리성 변화를 평가하기 위하여 2009년부터 2017년까지 전국의 밭, 과수원, 논을 대상으로 토양물리성 특성을 4년 주기로 분석하였다. 밭은 작토심, 심토 유기물 함량, 심토 산중식 경도가 증가하고 심토 용적밀도가 감소하며, 개량기준 초과비율도 지속적으로 감소하였다. 과수원은 경운심이 증가하였으나 심토 유기물 함량이 감소하고 적정기준을 초과하는 비율은 4년 전보다 증가하였다. 논은 작토심, 심토 유기물 함량이 감소하고 심토 용적밀도가 증가하며 개량기준 초과비율이 증가하는 등 물리성 불량이 심화되었다. 최근 10년간 밭, 과수원에 비해 논의 물리성이 악화되는 것을 확인할 수 있었으며, 공통적으로 심토 유기물 함량이 감소하고 심토 용적밀도가 증가하는 주요한 요인은 토양유기물로 평가되었다. 따라서 토양물리성 질 관리에 유기물은 중요한 요소이었으며, 특히 논에서 지속적인 유기물 관리와 경운방법 개선 등이 필요하다.

Despite the accident rate for fishing vessels accounts for 70% of all maritime accidents, few studies on such accidents have been done and most of the them mainly focus on causes and mitigation policies to reduce that accident rate. Thus, this risk analysis on sea accidents is the first to be performed for the successful and efficient implementation of accident reducing measures. In risk analysis, risk is calculated based on the combination of frequency and the consequence of an accident, and is usually expressed as a single number. However, there exists uncertainty in the risk calculation process if one uses a limited number of data for analysis. Therefore, in the study we propose a probabilistic simulation method to forecast risk not as a single number, but in a range of possible risk values. For the capability of the proposed method, using the criteria with the ALARP region, we show the possible risk values spanning across the different risk regions, whereas the single risk value calculated from the existing method lies in one of the risk regions. Therefore, a decision maker could employ appropriate risk mitigation options to handle the risks lying in different regions. For this study, we used fishing vessel accident data from 1988 to 2016.