Zirconolite Matrices for the Immobilization of REE–Actinide Wastes

Yudintsev, S. V.; Nickolsky, Maximilian S.; Ojovan, Michael I.; Stefanovsky, O.I.; Malkovsky, V. I.; Ulanova, Amina S.; Blackburn, Lewis R.

doi:10.3390/ceramics6030098

Cited by 6 publications

(3 citation statements)

References 202 publications

(514 reference statements)

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“…The maximum REE content in the zirconolite is 40 wt.% [23], and in the britholite, it reaches 75 wt.% [80]. Therefore, the REE content in glass-ceramics with britholite will also be approximately two times higher than in matrices with zirconolite.…”

Section: Britholite Glass-ceramicsmentioning

confidence: 96%

“…Stable elements or U and Th with a long half-life and low heat release are usually used in the laboratory synthesis and study of high-level waste matrices. For trivalent MAs (Am, Cm), REEs serve as simulants (Table 6); most often, Nd [22,23]. This approach is based on the proximity of the radii of Nd 3+ , Am 3+ , and Cm 3+ [24].…”

Section: Effect Of Radiogenic Heat On the Vitreous Matrix Of The Ree-...mentioning

confidence: 99%

“…The symbol Ln refers to individual REEs, primarily Nd, their mixtures, as well as the REE-MA fraction as a whole. These crystalline phases have long been studied as possible actinide matrices with the data on their radiation and corrosion resistance indicating promise for their use for this purpose [16,17,23,28,33,35,39,45,[60][61][62]. The important thing is that they have natural analogues, including radioactive minerals containing REEs, U, and Th, with an age of many millions of years.…”

Section: Experimental Studies Of Crystallization Of Glasses With Rees...mentioning

confidence: 99%

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Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

Yudintsev,

Ojovan,

Malkovsky

2024

J. Compos. Sci.

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The current policy of managing high-level waste (HLW) derived in the closed nuclear fuel cycle consists in their vitrification into B-Si or Al-P vitreous forms. These compounds have rather limited capacity with respect to the HLW (5–20 wt%), and their properties change over time due to devitrification of the glasses. Cardinal improvement in the management of HLW can be achieved by their separation onto groups of elements with similar properties, followed by their immobilization in robust waste forms (matrices) and emplacement in deep disposal facilities. One of the possible fractions contains trivalent rare-earth elements (REEs) and minor actinides (MAs = Am and Cm). REEs are the fission products of actinides, which are mainly represented by stable isotopes of elements from La to Gd as well as Y. This group also contains small amounts of short-lived radionuclides with half-lives (T1/2) from 284 days (144Ce) to 90 years (151Sm), including 147Pm (T1/2 = 2.6 years), 154Eu (T1/2 = 8.8 years), and 155Eu (T1/2 = 5 years). However, the main long-term environmental hazard of the REE–MA fraction is associated with Am and Cm, with half-lives from 18 years (244Cm) to 8500 years (245Cm), and their daughter products: 237Np (T1/2 = 2.14 × 106 years), 239Pu (T1/2 = 2.41 × 104 years), 240Pu (T1/2 = 6537 years), and 242Pu (T1/2 = 3.76 × 105 years), which should be immobilized into a durable waste form that prevents their release into the environment. Due to the heat generated by decaying radionuclides, the temperature of matrices with an REE–MA fraction will be increased by hundreds of centigrade above ambient. This process can be utilized by selecting a vitreous waste form that will crystallize to form durable crystalline phases with long-lived radionuclides. We estimated the thermal effects in a potential REE–MA glass composite material based on the size of the block, the content of waste, the time of storage before immobilization and after disposal, and showed that it is possible to select the waste loading, size of blocks, and storage time so that the temperature of the matrix during the first decades will reach 500–700 °C, which corresponds to the optimal range of glass crystallization. As a result, a glass–ceramic composite will be produced that contains monazite ((REE,MA)PO4) in phosphate glasses; britholite (Cax(REE,MA)10-x(SiO4)6O2) or zirconolite ((Ca,REE,MA)(Zr,REE,MA)(Ti,Al,Fe)2O7), in silicate systems. This possibility is confirmed by experimental data on the crystallization of glasses with REEs and actinides (Pu, Am). The prospect for the disposal of glasses with the REE–MA fraction in deep boreholes is briefly considered.

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Section: Britholite Glass-ceramicsmentioning

confidence: 96%

Section: Effect Of Radiogenic Heat On the Vitreous Matrix Of The Ree-...mentioning

confidence: 99%

Section: Experimental Studies Of Crystallization Of Glasses With Rees...mentioning

confidence: 99%

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Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

Yudintsev,

Ojovan,

Malkovsky

2024

J. Compos. Sci.

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Encapsulation of Uranium Oxide in Multiwall WS₂ Nanotubes

Kundrat,

Cohen,

Kossoy

et al. 2023

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Uranium is a high‐value energy element, yet also poses an appreciable environmental burden. The demand for a straightforward, low energy, and environmentally friendly method for encapsulating uranium species can be beneficial for long‐term storage of spent uranium fuel and a host of other applications. Leveraging on the low melting point (60 °C) of uranyl nitrate hexahydrate and nanocapillary effect, a uranium compound is entrapped in the hollow core of WS2 nanotubes. Followingly, the product is reduced at elevated temperatures in a hydrogen atmosphere. Nanocrystalline UO2 nanoparticles anchor within the WS2 nanotube lumen are obtained through this procedure. Such methodology can find utilization in the processing of spent nuclear fuel or other highly active radionuclides as well as a fuel for deep space missions. Moreover, the low melting temperatures of different heavy metal‐nitrate hydrates, pave the way for their encapsulation within the hollow core of the WS2 nanotubes, as demonstrated herein.

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Effect of sintering temperature on crystal growth and evolution of CaZrTi2O7–CaNdTiNbO7 ceramics: Minor actinides immobilization host materials

Ji,

Song

et al. 2024

Nuclear Engineering and Design

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Zirconolite Matrices for the Immobilization of REE–Actinide Wastes

Cited by 6 publications

References 202 publications

Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

Encapsulation of Uranium Oxide in Multiwall WS₂ Nanotubes

Effect of sintering temperature on crystal growth and evolution of CaZrTi2O7–CaNdTiNbO7 ceramics: Minor actinides immobilization host materials

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Zirconolite Matrices for the Immobilization of REE–Actinide Wastes

Cited by 6 publications

References 202 publications

Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

Encapsulation of Uranium Oxide in Multiwall WS2 Nanotubes

Effect of sintering temperature on crystal growth and evolution of CaZrTi2O7–CaNdTiNbO7 ceramics: Minor actinides immobilization host materials

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Encapsulation of Uranium Oxide in Multiwall WS₂ Nanotubes