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Laboratory actinide partitioning: Whitlockite/liquid and influence of actinide concentration levels

Benjamin, T. M. and Jones, J. H. and Heuser, W. R. and Burnett, D. S. (1983) Laboratory actinide partitioning: Whitlockite/liquid and influence of actinide concentration levels. Geochimica et Cosmochimica Acta, 47 (10). pp. 1695-1705. ISSN 0016-7037. https://resolver.caltech.edu/CaltechAUTHORS:20150427-102542957

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Abstract

Fission and alpha track radiography techniques have been used to measure partition coefficients (D) at trace (ppm) concentration levels for the actinide elements Th, U, and Pu between synthetic whitlockite and coexisting “haplobasaltic” silicate liquid at 1 bar pressure and 1250°C at oxygen fugacities from 10^(−8.5) and 10^(−0.7) bars. Pu is much more readily incorporated into crystalline phases than is U or Th under reducing conditions (fO_2 = 10^(−8.5)), because Pu is primarily trivalent, whereas U and Th are tetravalent. Definitive valence state assignments cannot be made, but our best estimates of corrected partition coefficients for Pu^(+3), Pu^(+4), Th^(+4), U^(+4), and U^(+6) are, for whitlockite 3.6/<⩽0.6/1.2/0.5/⩽0.002. The effect of changing pressure and liquidus temperature is relatively small, which probably reflects a weak temperature dependence for D (whitlockite) but possibly could be due to cancellation of opposing temperature and pressure effects. Comparison of experiments at trace U levels with those containing percent concentrations of UO_2 indicate that Si is involved in the substitution of U in whitlockite with U + 2Si ⇄ Ca + 2P being the most likely mechanism. D_u is lower. 0.3 vs 0.5. at percent levels compared to 20 ppm. This is best explained by the effect of U on melt structure or by a decrease in the fraction of tetravalent U at high U concentrations.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/0016-7037(83)90019-4DOIArticle
http://www.sciencedirect.com/science/article/pii/0016703783900194PublisherArticle
ORCID:
AuthorORCID
Burnett, D. S.0000-0001-9521-8675
Additional Information:© 1983 Pergamon Press Ltd. Received 6 August 1982, Accepted 27 June 1983. This research was supported by NASA grant NSG 7202. We thank M. T. Murrell for helpful discussions. The manuscript profited greatly from reviews by E. Dowty and L. Haskin.
Funders:
Funding AgencyGrant Number
NASANSG 7202
Issue or Number:10
Record Number:CaltechAUTHORS:20150427-102542957
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150427-102542957
Official Citation:T.M. Benjamin, J.H. Jones, W.R. Heuser, D.S. Burnett, Laboratory actinide partitioning: Whitlockite/liquid and influence of actinide concentration levels, Geochimica et Cosmochimica Acta, Volume 47, Issue 10, October 1983, Pages 1695-1705, ISSN 0016-7037, http://dx.doi.org/10.1016/0016-7037(83)90019-4. (http://www.sciencedirect.com/science/article/pii/0016703783900194)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57001
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:27 Apr 2015 19:27
Last Modified:09 Mar 2020 13:18

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