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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2018: 2.631

CiteScore 2018: 2.55

SCImago Journal Rank (SJR) 2018: 1.355
Source Normalized Impact per Paper (SNIP) 2018: 1.103

Online
ISSN
1945-3027
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Volume 98, Issue 5-6

Issues

Versatile Monazite: Resolving geological records and solving challenges in materials science. Monazite as a promising long-term radioactive waste matrix: Benefits of high-structural flexibility and chemical durability

Nicolas Dacheux
  • Corresponding author
  • ICSM, UMR 5257 CEA/CNRS/UM2/ENSCM, Site de Marcoule–Bât 426, BP 17171, 30207 Bagnols/Cèze, France
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/ Nicolas Clavier
  • ICSM, UMR 5257 CEA/CNRS/UM2/ENSCM, Site de Marcoule–Bât 426, BP 17171, 30207 Bagnols/Cèze, France
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Renaud Podor
  • ICSM, UMR 5257 CEA/CNRS/UM2/ENSCM, Site de Marcoule–Bât 426, BP 17171, 30207 Bagnols/Cèze, France
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  • De Gruyter OnlineGoogle Scholar
Published Online: 2015-03-07 | DOI: https://doi.org/10.2138/am.2013.4307

Abstract

Monazite (Ln3+PO4) and related solid solutions are a well-known source of rare earth elements on earth. They may also accommodate large amounts of thorium and uranium without sustaining damage to the structure by self-irradiation. Such observations led to monazite-type structures being proposed as a potential host matrix for sequestering long-lived radionuclides produced during the nuclear fuel cycle and/or plutonium and americium from dismantled nuclear weapons. Monazite has two main advantages as a matrix for the containment of radioactive waste (or “radwaste”). The first is a highly flexible structure that permits accommodation of high concentrations of actinides. The incorporation of trivalent elements may be achieved by direct synthesis of An3+PO4 (An3+ = plutonium, Pu to einsteinium, Es), while tetravalent cation incorporation requires coupled substitutions, either on the anionic site (leading to monazite-huttonite solid solution) or on the cationic site (monazite-cheralite solid solution). Various methods developed for the preparation of such compounds are summarized here, as well as the experimental conditions required for the production of sintered pellets, with a particular focus on plutonium-bearing compositions. The second highly favorable property of monazite is its high chemical durability. Several experimental procedures developed to determine normalized leaching rates are reviewed, as well as results obtained from natural and synthetic monazite. Potential phases formed during dissolution were considered because they also partially control the concentration of actinides in the media. A preliminary list for such phases of interest, as well as corresponding thermodynamic data, is presented.

Keywords: Monazite; actinides; leaching; synthesis; phosphate; radwaste matrix

About the article

Received: 2012-07-26

Accepted: 2012-12-31

Published Online: 2015-03-07

Published in Print: 2013-05-01


Citation Information: American Mineralogist, Volume 98, Issue 5-6, Pages 833–847, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am.2013.4307.

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© 2015 by Walter de Gruyter Berlin/Boston.

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