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- Title
Shedding Light on the Enigmatic TcO<sub>2</sub> ⋅ xH<sub>2</sub>O Structure with Density Functional Theory and EXAFS Spectroscopy.
- Authors
Oliveira, Augusto F.; Kuc, Agnieszka; Heine, Thomas; Abram, Ulrich; Scheinost, Andreas C.
- Abstract
The β‐emitting 99Tc isotope is a high‐yield fission product in 235U and 239Pu nuclear reactors, raising special concern in nuclear waste management due to its long half‐life and the high mobility of pertechnetate (TcO4−). Under the conditions of deep nuclear waste repositories, Tc is retained through biotic and abiotic reduction of TcO4− to compounds like amorphous TcO2 ⋅ xH2O precipitates. It is generally accepted that these precipitates have linear (Tc(μ‐O)2(H2O)2)n chains, with trans H2O. Although corresponding Tc−Tc and Tc−O distances have been obtained from extended X‐ray absorption fine structure (EXAFS) spectroscopy, this structure is largely based on analogy with other compounds. Here, we combine density‐functional theory with EXAFS measurements of fresh and aged samples to show that, instead, TcO2 ⋅ xH2O forms zigzag chains that undergo a slow aging process whereby they combine to form longer chains and, later, a tridimensional structure that might lead to a new TcO2 polymorph.
- Subjects
EXTENDED X-ray absorption fine structure; RADIOACTIVE waste repositories; DENSITY functional theory; RADIOACTIVE wastes; WASTE management; FISSION products
- Publication
Chemistry - A European Journal, 2022, Vol 28, Issue 59, p1
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.202203011