Plutonium-Doped Monazite and Other Orthophosphates—Thermodynamics and Experimental Data on Long-Term Behavior

Mikhailova, Polina; Burakov, Boris; Eremin, Nikolai; Averin, Alexei; Shiryaev, Andrey

doi:10.3390/su13031203

Open AccessArticle

Plutonium-Doped Monazite and Other Orthophosphates—Thermodynamics and Experimental Data on Long-Term Behavior

by

Polina Mikhailova

¹,

Boris Burakov

^2,3,*

,

Nikolai Eremin

¹,

Alexei Averin

⁴

and

Andrey Shiryaev

^4,*

¹

Geology Department, Moscow State University, 119991 Moscow, Russia

²

V.G. Khlopin Radium Institute, 194021 St. Petersburg, Russia

³

A.F. Ioffe Institute, 194021 St. Petersburg, Russia

⁴

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS, 119071 Moscow, Russia

^*

Authors to whom correspondence should be addressed.

Sustainability 2021, 13(3), 1203; https://doi.org/10.3390/su13031203

Submission received: 15 December 2020 / Revised: 16 January 2021 / Accepted: 20 January 2021 / Published: 24 January 2021

(This article belongs to the Special Issue Challenges in the Long-Term Behaviour of Highly Radioactive Materials)

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Abstract

The paper consists of two main parts: a microscopic and spectroscopic investigation of the single crystal of 17-year-old ²³⁸Pu-doped Eu-monazite, and a theoretical calculation of the properties of several structural types of orthophosphates. It is shown that actinide-doped monazite is prone to the formation of mechanically weak, poorly crystalline crust, presumably consisting of rhabdophane. Its formation is likely promoted by the formation of peroxides and, potentially, acidic compounds, due to the radiolysis of atmospheric moisture. The calculations of mixing the enthalpies and Gibbs energies of binary solid solutions of Pu and rare earth element (REE) phosphates that were performed for the principal structural types—monazite, xenotime, rhabdophane—show that, in the case of light REEs, the plutonium admixture is preferentially redistributed into the rhabdophane. This process strongly affects the behavior of actinides, leached from a monazite-based waste form. The applications of these results for the development of actinide waste forms are discussed. The current data on the behavior of real actinide-doped monazite suggest that this type of ceramic waste form is not very resistant, even in relatively short time periods.

Keywords: plutonium; monazite; rhabdophane; orthophosphate; radiolysis; nuclear waste

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MDPI and ACS Style

Mikhailova, P.; Burakov, B.; Eremin, N.; Averin, A.; Shiryaev, A. Plutonium-Doped Monazite and Other Orthophosphates—Thermodynamics and Experimental Data on Long-Term Behavior. Sustainability 2021, 13, 1203. https://doi.org/10.3390/su13031203

AMA Style

Mikhailova P, Burakov B, Eremin N, Averin A, Shiryaev A. Plutonium-Doped Monazite and Other Orthophosphates—Thermodynamics and Experimental Data on Long-Term Behavior. Sustainability. 2021; 13(3):1203. https://doi.org/10.3390/su13031203

Chicago/Turabian Style

Mikhailova, Polina, Boris Burakov, Nikolai Eremin, Alexei Averin, and Andrey Shiryaev. 2021. "Plutonium-Doped Monazite and Other Orthophosphates—Thermodynamics and Experimental Data on Long-Term Behavior" Sustainability 13, no. 3: 1203. https://doi.org/10.3390/su13031203

APA Style

Mikhailova, P., Burakov, B., Eremin, N., Averin, A., & Shiryaev, A. (2021). Plutonium-Doped Monazite and Other Orthophosphates—Thermodynamics and Experimental Data on Long-Term Behavior. Sustainability, 13(3), 1203. https://doi.org/10.3390/su13031203

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Plutonium-Doped Monazite and Other Orthophosphates—Thermodynamics and Experimental Data on Long-Term Behavior

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