• Title/Summary/Keyword: Yucca Mountain

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Current Status of the YMP in the United States (미국 Yucca Mountain Project 현황)

  • 황용수;박진백;강철형;황주호;김상국
    • Tunnel and Underground Space
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    • v.12 no.2
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    • pp.71-83
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    • 2002
  • 본 기술보고에서는 미국의 고준위 방사성폐기물 발생 현황 및 최근 에너지성 장관의 최종 추천을 받는 등 활발하게 진행되고 있는 미국 유카산 고준위 방사성폐기물 처분장 후보 부지 선정 과정 및 조사 연구 현황을 요약하였다. 본 기술보고에 요약한 바와 같이 유카산 프로젝트의 자연 환경은 우리 나라와는 매우 상이하다. 그러나 세계 원자력 계에서의 미국의 영향력을 고려할 때 유카산 프로젝트의 성공은 2001년 핀란드 올킬루오토(Olkiluoto) 처분 부지 확보와 함께 원자력 계의 오랜 숙원이었던 고준위 방사성폐기물 처분을 실현시킴으로서 향후 원자력 에너지 사용의 증대와 함께 심부 지질에 대한 이해를 증진시키는데 크게 기여할 것이다.

CRITICALITY SAFETY OF GEOLOGIC DISPOSAL FOR HIGH-LEVEL RADIOACTIVE WASTES

  • Ahn, Joon-Hong
    • Nuclear Engineering and Technology
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    • v.38 no.6
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    • pp.489-504
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    • 2006
  • A review has been made for the previous studies on safety of a geologic repository for high-level radioactive wastes (HLW) related to autocatalytic criticality phenomena with positive reactivity feedback. Neutronic studies on geometric and materials configuration consisting of rock, water and thermally fissile materials and the radionuclide migration and accumulation studies were performed previously for the Yucca Mountain Repository and a hypothetical water-saturated repository for vitrified HLW. In either case, it was concluded that it would be highly unlikely for an autocatalytic criticality event to happen at a geologic repository. Remaining scenarios can be avoided by careful selection of a repository site, engineered-barrier design and conditioning of solidified HLW. Thus, criticality safety should be properly addressed in regulations and site selection criteria. The models developed for radiological safety assessment to obtain conservatively overestimated exposure dose rates to the public may not be used directly for the criticality safety assessment, where accumulated fissile materials mass needs to be conservatively overestimated. The models for criticality safety also require more careful treatment of geometry and heterogeneity in transport paths because a minimum critical mass is sensitive to geometry of fissile materials accumulation.

Tunnel and Site Investigations Using Seismic Tomography (탄성파 토모그래피를 이용한 터널탐사 및 부지조사)

  • 서백수;김학수;권병두
    • Tunnel and Underground Space
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    • v.4 no.3
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    • pp.250-255
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    • 1994
  • 복잡한 지하구조인 지하터널과 핵폐기물 저장소 부지조사에 관한 자료해석을 위하여 지오토모그래피를 이용하였다. 지하터널의 조사는 지하저장소, 자원개발 및 군사적인 측면에서 많은 연구와 응용이 요구된다. 본 연구에서는 미육군이 현장에서 얻은 자료를 처리하고 이를 이론모형의 결과와 비교하였다. 또한 핵폐기물 부지 조사는 미국의 핵폐기물 저장소의 후보로 지정된 Yucca Mountain의 지질구조에 대한 이론모형계산을 행하였으며, Jaramillio(1993)가 모형실험치를 image 방법에 의하여 계산한 결과와 비교하였다. 탐사방법으로는 탄성파 시추공-시추공 방법과 VSP 방법을 사용하였다. 지오토모그래피의 기본이론은 터널과 지하공간 제3권 1호(1993)에서 설명되었다.

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Site Selection Methods for High-Level Radioactive Waste Disposal Facilities: An International Comparison (고준위방사성폐기물 처분시설 부지선정 방식 해외사례 분석)

  • HyeRim Kim;MinJeong Kim;SunJu Park;WoonSang Yoon;JungHoon Park;JeongHwan Lee
    • The Journal of Engineering Geology
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    • v.33 no.2
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    • pp.335-353
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    • 2023
  • Site selection processes for high-level radioactive waste disposal facilities in different countries differ in terms of local geology and degree of public engagement. There seem to be three alternative processes for site selection: (1) selection with community consent after government choice; (2) selection with continuous community engagement after exclusion of unsuitable areas based on existing survey data; or (3) site selection where communities have expressed a willingness to participate. The Yucca Mountain site in Nevada, USA, was selected as the final disposal site by process (1) through six stages, but its development was suspended owing to opposition from the local governor and environmental groups. In Sweden, Switzerland, and Germany, process (2) is used and sites are selected through three stages. Sweden and Switzerland have completed site selection, and Germany is currently engaged in the process. The UK adopted process (3) with six stages, although the process has been suspended owing to poor community participation. In Korea, temporary storage facilities for spent nuclear fuel will reach saturation from 2030, so site selection must be promoted through various laws and systems, with continuous communication with local communities based on transparent and scientifically undertaken procedures.

Glass Dissolution Rates From MCC-1 and Flow-Through Tests

  • Jeong, Seung-Young
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • 2004.06a
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    • pp.257-258
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    • 2004
  • The dose from radionuclides released from high-level radioactive waste (HLW) glasses as they corrode must be taken into account when assessing the performance of a disposal system. In the performance assessment (PA) calculations conducted for the proposed Yucca Mountain, Nevada, disposal system, the release of radionuclides is conservatively assumed to occur at the same rate the glass matrix dissolves. A simple model was developed to calculate the glass dissolution rate of HLW glasses in these PA calculations [1]. For the PA calculations that were conducted for Site Recommendation, it was necessary to identify ranges of parameter values that bounded the dissolution rates of the wide range of HLW glass compositions that will be disposed. The values and ranges of the model parameters for the pH and temperature dependencies were extracted from the results of SPFT, static leach tests, and Soxhlet tests available in the literature. Static leach tests were conducted with a range of glass compositions to measure values for the glass composition parameter. The glass dissolution rate depends on temperature, pH, and the compositions of the glass and solution, The dissolution rate is calculated using Eq. 1: $rate{\;}={\;}k_{o}10^{(ph){\eta})}{\cdot}e^{(-Ea/RT)}{\cdot}(1-Q/K){\;}+{\;}k_{long}$ where $k_{0},\;{\eta}$ and Eaare the parameters for glass composition, pH, $\eta$ and temperature dependence, respectively, and R is the gas constant. The term (1-Q/K) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_{0},\;{\eta}\;and\;E_{a}$ are the parameters for glass composition, pH, and temperature dependence, respectively, and R is the gas constant. The term (1-Q/C) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_0$, and Ea are determined under test conditions where the value of Q is maintained near zero, so that the value of the affinity term remains near 1. The dissolution rate under conditions in which the value of the affinity term is near 1 is referred to as the forward rate. This is the highest dissolution rate that can occur at a particular pH and temperature. The value of the parameter K is determined from experiments in which the value of the ion activity product approaches the value of K. This results in a decrease in the value of the affinity term and the dissolution rate. The highly dilute solutions required to measure the forward rate and extract values for $k_0$, $\eta$, and Ea can be maintained by conducting dynamic tests in which the test solution is removed from the reaction cell and replaced with fresh solution. In the single-pass flow-through (PFT) test method, this is done by continuously pumping the test solution through the reaction cell. Alternatively, static tests can be conducted with sufficient solution volume that the solution concentrations of dissolved glass components do not increase significantly during the test. Both the SPFT and static tests can ve conducted for a wide range of pH values and temperatures. Both static and SPFt tests have short-comings. the SPFT test requires analysis of several solutions (typically 6-10) at each of several flow rates to determine the glass dissolution rate at each pH and temperature. As will be shown, the rate measured in an SPFt test depends on the solution flow rate. The solutions in static tests will eventually become concentrated enough to affect the dissolution rate. In both the SPFt and static test methods. a compromise is required between the need to minimize the effects of dissolved components on the dissolution rate and the need to attain solution concentrations that are high enough to analyze. In the paper, we compare the results of static leach tests and SPFT tests conducted with simple 5-component glass to confirm the equivalence of SPFT tests and static tests conducted with pH buffer solutions. Tests were conducted over the range pH values that are most relevant for waste glass disssolution in a disposal system. The glass and temperature used in the tests were selected to allow direct comparison with SPFT tests conducted previously. The ability to measure parameter values with more than one test method and an understanding of how the rate measured in each test is affected by various test parameters provides added confidence to the measured values. The dissolution rate of a simple 5-component glass was measured at pH values of 6.2, 8.3, and 9.6 and $70^{\circ}C$ using static tests and single-pass flow-through (SPFT) tests. Similar rates were measured with the two methods. However, the measured rates are about 10X higher than the rates measured previously for a glass having the same composition using an SPFT test method. Differences are attributed to effects of the solution flow rate on the glass dissolution reate and how the specific surface area of crushed glass is estimated. This comparison indicates the need to standardize the SPFT test procedure.

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