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Development of a Geochemical Speciation Model for Use in Evaluating Leaching from a Cementitious Radioactive Waste Form
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2021-06-16 , DOI: 10.1021/acs.est.0c06227
Zhiliang Chen 1 , Peng Zhang 1 , Kevin G Brown 1 , Janelle L Branch 1 , Hans A van der Sloot 2 , Johannes C L Meeussen 3 , Rossane C Delapp 1 , Wooyong Um 4, 5 , David S Kosson 1
Affiliation  

Cast Stone has been developed to immobilize a fraction of radioactive waste at the Hanford Site; however, constituents of potential concern (COPCs) can be released when in contact with water during disposal. Herein, a representative mineral and parameter set for geochemical speciation modeling was developed for Cast Stone aged in inert and oxic environments, to simulate leaching concentrations of major and trace constituents. The geochemical speciation model was verified using a monolithic diffusion model in conjunction with independent monolithic diffusion test results. Eskolaite (Cr2O3) was confirmed as the dominant mineral retaining Cr in Cast Stone doped with 0.1 or 0.2 wt % Cr. The immobilization of Tc as a primary COPC in Cast Stone was evaluated, and the redox states of porewater within monolithic Cast Stone indicated by Cr are insufficient for the reduction of Tc. However, redox states provided by blast furnace slag (BFS) within the interior of Cast Stone are capable of reducing Tc for immobilization, with the immobilization reaction rate postulated to be controlled by the diffusive migration of soluble Tc in porewater to the surface of reducing BFS particles. Aging in oxic conditions increased the flux of Cr and Tc from monolithic Cast Stone.

中文翻译:

开发用于评价胶结放射性废物形式的浸出的地球化学形态模型

铸石已被开发用于固定汉福德站点的一小部分放射性废物;然而,在处置过程中与水接触时,可能会释放出潜在关注成分 (COPC)。在此,为在惰性和有氧环境中老化的铸石开发了用于地球化学形态建模的代表性矿物和参数集,以模拟主要和痕量成分的浸出浓度。地球化学形态模型使用整体扩散模型结合独立整体扩散测试结果进行验证。Eskolaite (Cr 2 O 3) 被确认为在掺有 0.1 或 0.2 wt% Cr 的铸石中保留 Cr 的主要矿物。评估了 Tc 作为铸石中主要 COPC 的固定化,并且由 Cr 表示的整体铸石中孔隙水的氧化还原状态不足以降低 Tc。然而,高炉炉渣 (BFS) 在铸石内部提供的氧化还原状态能够降低 Tc 以进行固定,固定化反应速率假定由孔隙水中的可溶性 Tc 扩散迁移到还原 BFS 表面来控制粒子。在有氧条件下时效增加了整体铸石中 Cr 和 Tc 的通量。
更新日期:2021-07-06
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