324铀矿床近地表矿体中长寿命铀系核素和类比微量元素迁移特征

MIGRATION OF URANIUM-SERIES RADIONUCLIDES AND SOME TRACE ELEMENTS IN A SUBSURFACE OREBODY OF THE URANIUM DEPOSIT NO.324, SOUTH CHINA

对一近地表铀矿体中某些铀系长寿命核素的放射性平衡状态和14种微量元素迁移特征研究得出，自该铀矿床63Ma前生成至今，仅近1Ma来，当上覆花岗岩遭剥蚀使矿体近地表时，矿石中天然放射性核和微量元素才因水-岩反应沿围岩破碎带、裂隙发生迁移；裂隙两侧岩石受水-岩反应影响的范围较小，裂隙面的化学组分以溶失为主，裂隙两侧粘土化花岗岩中则以核素、元素的扩散和吸附为主。最后阐述了本研究结果对高放废物处置库安全评价的类比意义。

Distribution of uranium-series radionuclides, i.e.238U 234U, 230Th and226Ra, and 14trace elements in subsurface granitic rock near an orebody of the uranium deposit No.324, South China, have been examined as natuthl analogue of safety assessment on granite-hosted highlevel radwaste repositories. The results indicate that a small distance migration of radionuclides and trace elements occured only during past 1 Ma when the orebody rose to subsurface owing to weathering. lsotopic data suggest that remobilization of uranium from the orebody would imply a time scale from 106-105a to recent. There is evidence of recent achve groundwater interaction occurring along and adjacent to mineralized faults and fractures, remobilizing both uranium and radium within a distance of 5 to 6cm from fracture surface. A secular isotopic eqtulibrium comes from clay-filled fratures, which helps to underiine how clay efficiently retard migration of radionunclides and trace elements. These results supply us with some valuable considerations in the performance assessment of concepts for the disposal of high-level radwaste.