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Radiochimica Acta

International Journal for chemical aspects of nuclear science and technology

Ed. by Qaim, Syed M.

12 Issues per year

IMPACT FACTOR 2012: 1.373
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Rank 6 out of 34 in category Nuclear Science & Technology in the 2012 Thomson Reuters Journal Citation Report/Science Edition

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Reduction of plutonium(VI) in brine under subsurface conditions

Donald T. Reed / J. F. Lucchini / S. B. Aase / A. J. Kropf

Citation Information: Radiochimica Acta. Volume 94, Issue 9-11, Pages 591–597, ISSN (Print) 0033-8230, DOI: 10.1524/ract.2006.94.9-11.591, September 2009

Publication History:
Received:
2005-09-23
Accepted:
2006-03-26
Published Online:
2009-09-25

The redox stability of PuO22+ was investigated in brine under subsurface conditions. In simulated brines, when no reducing agent was present, 0.1 mM concentrations of plutonium(VI) were stable as regards to reduction for over two years, which was the duration of the experiments performed. In these systems, the plutonyl existed as a carbonate or hydroxy-chloride species. The introduction of reducing agents (e.g. steel coupons, and aqueous Fe2+) typically present in a subsurface repository, however, led to the destabilization of the plutonium(VI) complexes and the subsequent reduction to Pu(IV) under most conditions investigated. X-ray Absorption Near-Edge Spectroscopy (XANES) confirmed that the final oxidation state in these systems was Pu(IV). This reduction lowered the overall steady state concentration of plutonium in the brine by 3−4 orders of magnitude. These results show the importance of considering repository constituents in evaluating subsurface actinide solubility/mobility and provide further evidence of the effectiveness of reduced iron species in the reduction and immobilization of higher-valent plutonium species.

Keywords: Plutonium; WIPP; XANES; Iron Reduction; Brine Chemistry

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