Chemical Composition, Geochemical Alteration, and Radiation Damage Effects in Natural Perovskite

Lumpkin, Gregory R.; Colella, Michael; Smith, Katherine L.; Mitchell, Roger H.; Larsen, Alf Olav

doi:10.1557/proc-506-207

Cited by 12 publications

(10 citation statements)

References 15 publications

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“…5 in Hansmann, 1996). Lumpkin et al (1998) discussed the thermal histories of natural analogue-bearing host rocks in some detail. One advantage of working with late orogenic igneous rocks is that a simple mathematical approach, within the boundaries of reasonable assumptions, can be applied in order to derive the cooling history.…”

Section: Natural Analogue Host Rocks and Thermal Historymentioning

confidence: 99%

“…Furthermore, Lumpkin et al (1998) and Chakhmouradian et al (1999) described the hydrothermal alteration of Na-bearing perovskite ( i d e a l l y N a 0 . 5 L n 0 .…”

Section: Geochemical Behaviourmentioning

confidence: 99%

“…Using literature data for other crichtonite-group minerals from Tuscany, Italy and two Norwegian localities, Lumpkin et al (2013) were able to construct an approximate 'median' critical dose curve with values of D 0 = 0.51610 16 a/mg and K = 1.5610 À9 y À1 using equation 9. In-depth studies have not been conducted on radiation damage in natural perovskite; however, Lumpkin et al (1998) examined a suite of samples with ages of 295-520 Ma using analytical electron microscopy and reported ThO 2 contents of 1.4À3.1 wt.% indicating that the beginning of the crystallineÀamorphous transformation (e.g. first observable damage, not the critical dose) occurs within the dose range of 0.3À0.6610…”

Section: Radiation Damage Effectsmentioning

confidence: 99%

“…For geothermal gradients of 20À40ºC km À1 , the surrounding rocks would have been at temperatures of 100À250ºC. Using this approach, Lumpkin et al (1998) estimated that suites of zirconolite samples from different localities would have experienced average temperatures as high as 235ºC for the larger igneous intrusions (e.g. Adamello, Italy) to a minimum of~50ºC for some carbonatites.…”

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confidence: 99%

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The role of Th-U minerals in assessing the performance of nuclear waste forms

et al. 2014

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Materials designed for nuclear waste disposal include a range of ceramics, glass ceramics and glass waste forms. Those with crystalline phases have provided the momentum for studies of minerals as a means to understand aspects of waste-form crystal chemistry, behaviour in aqueous systems and radiation damage over geological periods of time. Although the utility of natural analogue studies varies, depending upon the degree of analogy to the proposed geological repository and other factors such as chemical composition, the available data suggest that Th-U host phases such as brannerite, monazite, pyrochlore, zircon and zirconolite are resistant generally to dissolution in aqueous fluids at low temperatures. Geochemical durability may or may not extend to hydrothermal systems depending on the specifics of fluid composition, temperature and pressure. At elevated temperatures, for example, davidite may break down to new phase assemblages including titanite, ilmenite and rutile. Perovskite is generally less resistant to dissolution at low temperatures and breaks down to TiO2, releasing A-site cations to the aqueous fluid. Studies of radiation damage indicate that the oxide and silicate phases become amorphous as a result of the gradual accumulation of alpha-recoil collision cascades. Monazite tends to remain crystalline on geological time scales, a very attractive property that potentially eliminates major changes in physical properties such as density and volume, thereby reducing the potential for cracking, which is a major concern for zircon. In spite of recent success in describing the behaviour of Th-U minerals in geological systems, considerable work remains in order to understand the P-T-X conditions during alteration and T-t history of the host rocks. ABSTRACTMaterials designed for nuclear waste disposal include a range of ceramics, glass ceramics and glass waste forms. Those with crystalline phases have provided the momentum for studies of minerals as a means to understand aspects of waste-form crystal chemistry, behaviour in aqueous systems and radiation damage over geological periods of time. Although the utility of natural analogue studies varies, depending upon the degree of analogy to the proposed geological repository and other factors such as chemical composition, the available data suggest that Th-U host phases such as brannerite, monazite, pyrochlore, zircon and zirconolite are resistant generally to dissolution in aqueous fluids at low temperatures. Geochemical durability may or may not extend to hydrothermal systems depending on the specifics of fluid composition, temperature and pressure. At elevated temperatures, for example, davidite may break down to new phase assemblages including titanite, ilmenite and rutile. Perovskite is generally less resistant to dissolution at low temperatures and breaks down to TiO 2 , releasing A-site cations to the aqueous fluid. Studies of radiation damage indicate that the oxide and silicate phases become amorphous as a result of the gradual accumulation of...

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Section: Natural Analogue Host Rocks and Thermal Historymentioning

confidence: 99%

“…Furthermore, Lumpkin et al (1998) and Chakhmouradian et al (1999) described the hydrothermal alteration of Na-bearing perovskite ( i d e a l l y N a 0 . 5 L n 0 .…”

Section: Geochemical Behaviourmentioning

confidence: 99%

Section: Radiation Damage Effectsmentioning

confidence: 99%

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The role of Th-U minerals in assessing the performance of nuclear waste forms

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“…could be due to a difference in the critical amorphization dose of loparite and the alteration product, provided that the alteration event occurred soon after crystallization of the loparite. For example, Smith et al (1998) andLumpkin et al (1998) have shown that the critical amorphization dose of perovskite structure types may be as much as a factor of five greater than the critical dose of other Nb-Ta-Ti minerals (e.g., pyrochlore and zirconolite).…”

Section: Perovskitementioning

confidence: 99%

Geochemical behaviour of host phases for actinides and fission products in crystalline ceramic nuclear waste forms

Lumpkin

Smith

Gieré

et al. 2004

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A number of polyphase or single-phase ceramic waste forms have been considered as options for the disposal of nuclear waste in geological repositories. Of critical concern in the scientific evaluation of these materials is their performance in natural systems over long periods of time (e.g., 103 to 106 years). This paper gives an overview of the aqueous durability of the major titanate host phases for actinides (e.g., Th, U, Np, Pu, Cm) and important fission products (e.g., Sr and Cs) in alternative crystalline ceramic waste forms. These host phases are compared with reference to some basic acceptance criteria, including the long-term behaviour determined from studies of natural samples. The available data indicate that zirconolite and pyrochlore are excellent candidate host phases for actinides. These structures exhibit excellent aqueous durability, crystal chemical flexibility, high waste loadings, and well-known processing conditions. Although both pyrochlore and zirconolite become amorphous due to alphadecay processes, the total volume swelling is only 5-6% and there is no significant effect of radiation damage on aqueous durability. Hollandite also appears to be an excellent candidate host phase for radioactive Cs isotopes. Brannerite and perovskite, on the other hand, are more prone to alteration in aqueous fluids and have a lower degree of chemical flexibility. With the exception of hollandite, many of the properties of these potential host phases have been confirmed through studies of natural samples.

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