According to the continued generation of spent nuclear fuel, a reliable safety assessment is highly required with the precise modeling of the migration and retardation behavior of radionuclides to enhance public acceptance and hinder excessive conservativeness during the construction of the repository. In particular, the colloids formed in the repository-relevant condition are known to accelerate the migration of radionuclides. Thus, geochemical behavior and relevant characteristics of colloids are needed to be unambiguously clarified. The objective of the present work is to investigate the fundamental characteristics of colloids contained in the natural groundwater system by using various analytical methods and the tangential flow ultra-filtration (TFUF) system. The granitic groundwater sample from the DB-3 borehole at the KURT (KAERI Underground Research Tunnel) was taken by an airtight stainless steel cylinder coated on the inside with PTFE to prevent the infiltration of ambient air into the geologic groundwater sample. And then, the groundwater sample was transferred to the inert glovebox filled with Ar gas to monitor the pH and Eh equilibrium of the aqueous sample. For further investigation, the colloid contained in the groundwater sample was concentrated by using the TFUF system equipped with a membrane filter (pore size: 3 kDa). The concentrated groundwater sample was analyzed with various methods such as ICP-MS/OES, IC, DLS/ELS, FE-TEM/SEM-EDS, ATR-FTIR, TOC, LC-OCD, etc. In this study, the size of groundwater colloids was determined to be 182.3 ± 52.7 nm with the major constituents of C, S, O, Fe, Al, Si, etc. The amount of organic carbon and the concentrations of organic substances determined by means of the molecular weight fraction with the TOC and LC-OCD provide further detailed information for the colloids in the KURT groundwater sample. The results obtained in this study are expected to be used as preliminary experimental data for modeling the colloid-facilitated migration of radionuclides to improve the reliability of the safety assessment of the geologic repository.

In this study, to develop and verify the Jeju-type groundwater thermal system design program, the energy consumption and system performance derived by input into the design program based on the load calculated on the demonstration site and the groundwater temperature were compared and analyzed with the actual measured values. The theoretical values ​​of energy consumption and heating and cooling COP ​​obtained through the Jeju-type groundwater thermal system design program were 11.24kW, 5.28 for heating, 13.31kW, 3.94 for cooling respectively. The measured values ​​of energy consumption and COP of the Jeju-type groundwater thermal system were 3967.2kW and 4.5, respectively. The error between the theoretical value and the measured value obtained through the design program is 0% and 2.39%, respectively. The errors that occur in the predicted values ​​and the actual values ​​are due to variables that are ignored in the system assumptions. If users consider errors and use it when designing groundwater thermal systems, they can estimate the cost of required drilling works, heat exchangers, and heat pumps and analyze economic feasibility.

국내 중·저준위 방사성폐기물 처분시설로 고려되고 있는 표층처분시설의 불포화대에서 핵종 이동을 야기하는 지하수 유동을 평가하기 위하여 유한요소법 기반의 COMSOL Multiphysics을 이용한 수치모델을 개발하였다. 그리고, 처분장 가장자리 를 대상으로 처분고, 뒤채움재, 처분덮개로 구성되는 표층처분시설과 그 아래에 위치한 불포화대를 포함한 수직 2차원의 모델 영역을 구성하여, 시나리오 별 모델링을 수행하였다. 지속적 강수 유입 조건과 간헐적 강수 유입 조건 비교에서 포화도의 파동 현상을 제외하고는 뚜렷한 차이점을 보이지 않는 것으로 판단되었다. 불포화대의 공극률이나 잔류함수비와 같은 입력 자료는 전반적으로 불포화대 지하수 유동에 큰 영향도가 없는 것으로 판단되었다. 하지만, 불포화대의 수리전도도는 지하수 유동에 큰 영향을 미치는 것으로 판단되었다. 즉, 처분고로의 지하수 유입 속도를 판단하기 위해서는 불포화대의 수리전도도 특성이 신중하게 고려되어야 할 것으로 판단되었다.

한국원자력연구원 내 지하 처분 연구시설(KURT)에서 채취한 지하수에 존재하는 나노 콜로이드 입자의 크기 및 농도를 현장에서 조사하기 위해 이동식 레이저 유도 파열 검출 장치를 개발하였다. 제작한 장치는 CCD 카메라를 이용하여 레이저 유도 플라즈마가 발생한 위치를 2-차원 영상으로 기록함으로써 광학적으로 입자의 크기를 결정할 수 있다. 크기가 정확히 알려진 폴리스틸렌 표준 입자를 이용하여 입자 크기 측정용 검정 곡선(calibration curve)을 구했고, 이를 이용하여 지하 처분 연구시설에서 채취한 지하수내 콜로이드 입자의 크기를 측정하였다. 지하수 내 존재하는 콜로이드 입자의 평균 크기는 108±26 nm임을 보였고, 농도는 50 ppb 이하인 것으로 추정하였다.

Quantitative assessment of groundwater level change under extreme event is important since groundwater system is directly affected by drought. Substantially, groundwater level fluctuation reveals to be delayed from several hours to few months after raining according to the aquifer characteristics. Groundwater system in Jeju Island would be also affected by drought and almost all regions were suffered from a severe drought during summer season (July to September) in 2013. To estimate the effect of precipitation to groundwater system, monthly mean groundwater levels in 2013 compared to those in the past from 48 monitoring wells belong to be largely affected by rainfall(Dr) over Jeju Island were analyzed. Mean groundwater levels during summer season recorded 100 mm lowered of precipitation compared to the past 30 years became decreased to range from 2.63 m to 5.42 m in southern region compared to the past and continued to December. These decreasing trends are also found in western(from –1.21 m to –4.06 m), eastern(-0.91 m to –3.24 m), and northern region(from 0.58 m to –4.02 m), respectively. Moreover, the response of groundwater level from drought turned out to be –3.80 m in August after delaying about one month. Therefore, severe drought in 2013 played an important role on groundwater system in Jeju Island and the effect of drought for groundwater level fluctuation was higher in southern region than other ones according to the regional difference of precipitation decrease.

가축매몰지 인근 지하수 수질은 지하수 이용과 관련하여 많은 관심이 집중되고 있다. 한국 환경부에서는 지하수 수질 감시를 위하여 지하수 수질을 직접 측정하는 방법을 제시하고 있다. 이 방법은 수질분석에 많은 시간과 비용이 소요되기 때문에 관측지점이 수백개 이상인 경우에는 효율적인 모니터링이 어려울 수 있다. 금회 연구에서는 지하수의 전기 전도도를 매몰지에서의 지하수 수질 지표로 사용하는 방안을 제안하였다. 지하수 수질 수준을 판별하기 위하여 가축 매물지 근방의 장기적인 지하수 수질 측정자료를 통계학적인 방법으로 분석하여 지하수 수질 지표와의 상관관계를 도출하였고, 무선 통신망을 이용한 원격 모니터링 기법을 이용하여 보다 신속하게 지하수 상태를 감시할 수 있는 가능성을 제시하였다.

본 연구에서는 대상유역인 경안천 유역 (유역면적 )에 대한 지하수 함양량 추정을 위해, 완전 분포형 모형인 MIKE SHE를 적용하였다. 모형 입력자료로서 DEM 토지이용도, 정밀토양도 등과 같은 GIS 자료를 구축하고, 기상자료를 이용하여 증발산 입력자료를 생성하였다. 유역 최종 출구점인 경안 수위표 지점에서의 유출자료를 활용하여 모형 보정과 검증을 수행한 결과, 관측치의 경향을 잘 모의하는 것으로 나타났으며, 유역내 운영되고 있는 마평 지하수위 관측

The reaction path of water-gneiss in 200m borehole at the Soorichi site of Yugu Myeon, Chungnam was simulated by the EQ3NR/EQ6 program. Mineral composition of borehole core and fracture-filling minerals, and chemical composition of groundwater was published by authors. In this study, chemical evolution of groundwater and formation of secondary minerals in water-gneiss system was modelled on the basis of published results. The surface water was used as a starting solution for reaction. Input parameters for modelling such as mineral assemblage and their volume percent, chemical composition of mineral phases, water/rock ratio reactive surface area, dissolution rates of mineral phases were determined by experimental measurement and model fit. EQ6 modelling of the reaction path in water-gneiss system has been carried out by a flow-centered flow through open system which can be considered as a suitable option for fracture flow of groundwater. The modelling results show that reaction time of 133 years is required to reach equilibrium state in water-gneiss system, and evolution of present groundwater will continue to pH 9.45 and higher na ion concentration. The secondary minerals formed from equeous phase are kaolinite, smectite, saponite, muscovite, mesolite, celadonite, microcline and calcite with uincreasing time. Modeling results are comparatively well fitted to pH and chemical composition of borehole groudwater, secondary minerals identified and tritium age of groundwater. The EQ6 modelling results are dependent on reliability of input parameters: water-rock ratio, effective reaction surface area and dissolution rates of mineral phases, which are difficult parameters to be measured.