Understanding of long-term behaviors of radioactive materials is of crucial importance in areas relevant to nuclear waste management. Especially, the safe disposal of high-level radioactive wastes (HLW) under the deep geological environment strongly relies upon not only the man-made engineering barrier system, but also the natural barrier system, i.e., the understanding and learnings from the nature. Currently in Korea, the KAERI Underground Research Tunnel (KURT) serves as a generic underground research site and provides relevant domestic geological values related to granitic rocks at various geological depths (40 – 500 m). Thus, the interpretation of uranium characteristics in the KURT granitic rocks can further provide the understanding of long-term behaviors of representative high-level radionuclides under the Korean geological environment of granites. Here, we report the characteristics of the uranium existing in the KURT rock samples at various depths analyzed by Electro-Probe Microscopic Analyzer (EPMA), micro X-ray Fluorescence Spectroscopy (XRF), X-ray Diffraction (XRD), etc. The analytical results of KURT rocks and groundwater revealed that the uranium mineralization consisted of the coffinite (USiO<sub>4</sub>) and relevant uranium phases with phosphates and rare earth elements. We note that most of uranium in the KURT rocks coexists with thorium, which is an indicative of solid-solution formations in mineralization under the KURT conditions. The information obtained in this study will be further useful in developing Safety Case based on the KURT for the disposability of HLW.<br/>

Characterization of KURT rock samples at various depths to understand the long-term uranium behaviors under the Korean geological environment of granites

251st National Meeting (2016)

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