铀与锝是对氧化还原条件敏感元素，存在多种价态，其迁移性受价态影响大，在还原性环境下，二者的迁移性将大大降低。铀是乏燃料的主要组成部分，主要存在形态为UO2，乏燃料的氧化破损也会导致其它长半衰期的裂变产物核素及超铀元素的浸出与迁移；而99-锝是核反应过程中产生的长半衰期裂变产物（产率高达6.13%），是高放废物（HLW）地质处置重点关注的几个放射性核素之一。甘肃北山花岗岩地区为我国高放废物地质处置库的重点研究区。本项目拟研究铀与锝在北山花岗岩场址条件下的氧化还原行为，查明花岗岩围岩中存在的Fe(II)-矿物对U(VI)与Tc(VII)的还原固定作用，并探讨Fe(III)和U(VI)对乏燃料UO2的氧化作用，研究结果将为处置库的选址、建造及性能评价提供基础参数与科学依据。

Uranium and technetium are redox-sensitive elements that can exist in several oxidation states, and their mobility is largely controlled by the oxidation states. Under reducing condition, both uranium and technetium are largely immobilized. Uranium is the matrix material of spent nuclear fuel (exists as UO2), and its oxidation can also cause the leaching of long-lived fission products and transuranium actinides. 99-Tc is a long-lived and high-yield (6.13%) fission product of nuclear reaction, and it is one of the key radionuclides concerned in the geologic disposal of high-level radioactive waste (HLW). Beishan granite area in Gansu province is considered as the most potential site for China’s repository of HLW. This project aims to investigate the redox behavior of uranium and technetium in Beishan granitic site condition, ascertain the role of the Fe(II)-minerals contained in granite host-rock on the reductive immobilization of U(VI) and Tc(VII), and unravel the role of Fe(III) and U(VI) on the oxidative dissolution of spent fuel (UO2). The findings will provide fundamental data and scientific basis for the site selection and repository construction, as well as the site performance assessment.