Durability of hot uniaxially pressed Synroc derivative wasteform for EURO-GANEX wastes

Hsieh, Yun‐Hao; Humphry-Baker, Samuel A.; Horlait, Denis; Gregg, Daniel J.; Vance, E. R.; Lee, William

doi:10.1016/j.jnucmat.2018.06.006

Cited by 8 publications

(4 citation statements)

References 24 publications

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“…The measured NLRi values for Ca and P were found in close agreement with the literature values. 55,56 Hassan et al studied the possibility of cobalt immobilization by pure HAp under the identical sintering condition to our study. 33 Their reported NLRi value for cobalt (2.5 Â 10 À5 g per m 2 per day) is very close to our reported value for cobalt (3.3 Â 10 À5 g per m 2 per day).…”

Section: Resultsmentioning

confidence: 75%

Efficient immobilization of ionic corrosion products by a silica-hydroxyapatite composite via a cold sintering route

et al. 2019

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Section: Resultsmentioning

confidence: 75%

Efficient immobilization of ionic corrosion products by a silica-hydroxyapatite composite via a cold sintering route

et al. 2019

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“…The Ti-metal relics were partly coated in deposits of micrometer-sized TiO 2 microspheres at the sample surface as seen in Figure 12, as a result of preferential TiF x leaching and titania formation. This phenomenon has been studied previously with several Synroc formulations, [36][37][38][39][40][41][42] the titania particles in the form of anatase providing a protective layer on the surface of the sample. CaF 2 particles remained reasonably unchanged at the surface of the sample, although for GC3A the surrounding residual glass appeared to have also preferentially leached (see Figure 12).…”

Section: Gc2b and Gc3amentioning

confidence: 90%

Hot Isostatically Pressed (HIPed) fluorite glass‐ceramic wasteforms for fluoride molten salt wastes

et al. 2020

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Molten pyroprocessing salts can be used to dissolve used nuclear fuel from a reactor allowing recovery of the actinides. Previously, ANSTO have demonstrated hot isostatically pressed (HIPed) sodalite glass‐ceramic wasteforms for eutectic (Li,K)Cl salts containing fission products, but this system cannot be used for the analogous molten alkali fluoride salts (eg, FLiNaK), which have utility in the application of the next generation of nuclear reactors. In this work, a novel glass‐ceramic composite wasteform has been prepared by HIPing, as a candidate for the immobilization of fission product‐bearing FLiNaK salts. The wasteform has been tailored to immobilize the high fluoride content of the waste within fluorite, whereas the waste alkali elements are incorporated in a durable sodium aluminoborosilicate glass, with total waste loadings of ~17‐21 wt% achieved. It was also demonstrated that the speciation of Mo‐ and Sb‐simulated fission products was altered by adding Ti metal due to a controlled redox environment. The resulting candidate wasteform has been studied by X‐ray diffraction and scanning electron microscopy, including the HIP canister‐wasteform interaction zone, and its performance assessed via leaching studies using the PCT and ASTM C1220 leaching protocols. Dr Vance very much enjoyed the challenge of wasteform design for problematic nuclear wastes, for which fission product‐bearing FLiNaK salts are a clear example. His ability to hone in on a wasteform solution with viable waste loadings that meet performance requirements was testament to his nearly 40 years experience in nuclear waste immobilization. The samples discussed in this work represent the last wasteform materials that he prepared.

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“…Such defects are known to arise from mechanical deformation during sample preparation as a function of particle size or monolith surface finish 127,131 . Further, changes in reactive surface area can be present arising from adhering fines 27,131 , surface roughness 132 and sample porosity 131,133 , also causing variations in short-term dissolution rates. In particular, difficulties remain in meaningfully representing these effects on heterogeneous surface energy distributions using geometric or BET surface areas 125 .…”

Section: Discussionmentioning

confidence: 99%

“…For perovskite phases, increasing mechanical deformation, increasing surface roughness and decreasing particle size have been shown to increase Ca release rates at short times due to changes in high-energy site distributions [131][132][133] . Similarly, for Ce-doped zirconolites, whilst Nikoloski et al observed Ca release rates decreased with increasing particle size 27 , contrastingly excellent agreement between powder and monolith Ca release rates was observed by Pöml et al 28 .…”

Section: Discussionmentioning

confidence: 99%

Undetected perovskite phase interference with zirconolite dissolution measurements

Goût,

Mir,

Fairclough

et al. 2024

npj Mater Degrad

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Zirconolite ceramics present a chemically durable host matrix for waste actinides, but zirconolite dissolution rates reported in the literature often vary significantly. Here, the release of Ca and Al from a hot isostatically pressed zirconolite (Ca0.8Zr0.9Ce0.3Ti1.6Al0.4O7.0) was shown to be predominantly driven by preferential dissolution of minor perovskite and alumina phases. Both phases were undetectable by XRD, and the perovskite was difficult to detect by SEM-EDS. Whilst the zirconolite phase exhibited no signs of alteration, dissolution of the perovskite proceeded congruently without forming a hydrated altered layer or diffusion of protons into the solid that would be indicative of an ion-exchange mechanism. The weak temperature dependence of dissolution (40, 90 and 150 °C) showed that kinetics were limited by transport and a mixed transport-surface controlled reaction for Ca and Al, respectively. A significant H2O-D2O isotope effect on dissolution was observed for Ca but not for Al at all temperatures. The former was consistent with an abated rate of hydrolysis in the absence of a contribution from diffusion, whilst the latter could be attributed to differences in the activated complex for Ca and Al release through hydrolysis. These results demonstrate the role of a secondary phase perovskite in the dissolution kinetics of zirconolite even when perovskite occurs at low concentration and evades detection by bulk techniques such as XRD. This study provides a potential explanation of variations in zirconolite ceramic dissolution rates present in the literature and provides a null result to tests of an incongruent Ca release mechanism from zirconolite.

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Durability of hot uniaxially pressed Synroc derivative wasteform for EURO-GANEX wastes

Cited by 8 publications

References 24 publications

Efficient immobilization of ionic corrosion products by a silica-hydroxyapatite composite via a cold sintering route

Efficient immobilization of ionic corrosion products by a silica-hydroxyapatite composite via a cold sintering route

Hot Isostatically Pressed (HIPed) fluorite glass‐ceramic wasteforms for fluoride molten salt wastes

Undetected perovskite phase interference with zirconolite dissolution measurements

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