Nuclear Melt Glass Dissolution and Secondary Mineral Precipitation at 40 to 200C

Zavarin, Mavrik; Roberts, S; Viani, B.E.; Pawloski, G A; Rose, T.

doi:10.2172/15014339

Cited by 5 publications

(16 citation statements)

References 6 publications

(27 reference statements)

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“…-10 -decreased as a function of time [27,68]. Such observations can be better explained by the "chemical affinity" concept.…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

“…The rupture of all bridging bonds(1~4) around a silicon atom in the glass, leads to the release of an orthosilicic acid molecule, H 4 SiO 4 . The hydrolysis reaction has been observed to accelerate in both acid and basic conditions, with a lowest rate in neutral environment [26,27]. Based on the first principles, it has been found [28][29][30][31][32][33] that the activation energy of the hydrolysis of T m -O-T n (where T=Si, Al; m, n = number of bridge oxygen atoms and 0<m, n<4) bonds can be rather variable: lower in acid and basic conditions but higher in neutral conditions.…”

Section: The Hydrolysis Processmentioning

confidence: 99%

“…At present, more and more researchers realise that it is too simple to regard the control mechanisms of rate drop or residual rate as one single mechanism, the control mechanism can be a combination of the two [12,58,59]. Sometimes chemical affinity can be dominating [27,68], sometimes the protective properties of the gel dominating [51][52][53], and sometimes the rate can be controlled by both mechanisms [59], depending on the glass composition and the leaching conditions. It is essential to find a way to combine the two providing a model with comprehensive application to general glass dissolution.…”

Section: Summary Of Rate Drop Mechanismsmentioning

confidence: 99%

“…-11 -has the same difficulty to explain experimental observations of decreasing dissolution rate when no gel layer is formed, only crystallized secondary precipitation phases [27,68].…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

“…-17 -environment [26,27,70]. Equation (13b) captures both the temperature and pH dependence of the initial rate and therefore k + , E a,Si and potentially n are specific to a particular glass.…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

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A mechanistic model for long-term nuclear waste glass dissolution integrating chemical affinity and interfacial diffusion barrier

Jivkov

et al. 2017

Journal of Nuclear Materials

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Abstract:Understanding the alteration of nuclear waste glass in geological repository conditions is critical element of the analysis of repository retention function. Experimental observations of glass alterations provide a general agreement on the following regimes: inter-diffusion, hydrolysis process, rate drop, residual rate and, under very particular conditions, resumption of alteration. Of these, the mechanisms controlling the rate drop and the residual rate remain a subject of dispute. This paper offers a critical review of the two most competitive models related to these regimes: affinity-limited dissolution and diffusion barrier. The limitations of these models are highlighted by comparison of their predictions with available experimental evidence. Based on the comprehensive discussion of the existing models, a new mechanistic model is proposed as a combination of the chemical affinity and diffusion barrier concepts. It is demonstrated how the model can explain experimental phenomena and data, for which the existing models are shown to be not fully adequate.Key words: nuclear waste glasses, long-term dissolution, mechanisms, modelling IntroductionRadioactivity wastes are generated at all stages of the nuclear fuel cycle, including the decommissioning of nuclear facilities, as well as from military applications. Of particular concern for the storage/disposal of radioactivity wastes are those containing long-lived radionuclides [1].The current plan ( countries such as Belgium, Finland , Sweden , France etc.)for long-term management of such wastes is to store them in deep, stable and lowpermeable geological formations [2].The storage design is based on the so-called multi-barrier concept, where several barriers prevent for a period of time, or slow down the release and migration of radionuclides through the geosphere [3,4].Within this concept, hazardous nuclides are immobilized into solidified bodies. The wasteform selection is difficult, since durability is not the sole criterion [5]. Currently, vitrification is regarded as the best solution for immobilizing radionuclides. This technology has been progressively developed over the last half-century, has matured and has become industrially robust.Data collected to date suggest that glass waste forms offer the advantages that they can accommodate a wide range of waste streams, are resistant to radiation damage, and are relatively inert to both chemical and thermal perturbations [6].The use of natural and archeological analogues supported further the durability argument of glass as waste forms [7][8][9][10][11]. Except for the alumino-phosphate glass used in Russia, the borosilicate glass has been universally selected by all other nations [12].In order to make scientifically-underpinned safety cases, the long-term behaviour of glassy wasteforms requires further understanding and assessment. Half-lives of some radionuclides extend to millions of years, requiring isolation for geological periods, while the period of investigation possible in the field and the la...

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“…-10 -decreased as a function of time [27,68]. Such observations can be better explained by the "chemical affinity" concept.…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Section: The Hydrolysis Processmentioning

confidence: 99%

Section: Summary Of Rate Drop Mechanismsmentioning

confidence: 99%

“…-11 -has the same difficulty to explain experimental observations of decreasing dissolution rate when no gel layer is formed, only crystallized secondary precipitation phases [27,68].…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

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A mechanistic model for long-term nuclear waste glass dissolution integrating chemical affinity and interfacial diffusion barrier

Jivkov

et al. 2017

Journal of Nuclear Materials

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Mapping of Uranium in Surrogate Nuclear Debris Using Laser-Induced Breakdown Spectroscopy (LIBS)

et al. 2019

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This work describes the use of a laser-induced breakdown spectroscopy (LIBS) system to conduct macroscopic elemental mapping of uranium and iron on the exterior surface and interior center cross-section of surrogate nuclear debris for the first time. The results suggest that similar LIBS systems could be packaged for use as an effective instrument for screening samples during collection activities in the field or to conduct process control measurements during the production of debris surrogates. The technique focuses on the mitigation of chemical and physical matrix effects of four uranium atomic emission lines, relatively free of interferences and of good analytical value. At a spatial resolution of 0.5 mm, a material fractionation pattern in the surrogate debris is identified and discussed in terms of constituent melting temperatures and thermal gradients experienced.

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Radionuclide Partitioning in an Underground Nuclear Test Cavity

Rose¹,

Hu²,

Zhao³

et al. 2009

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In 2004, a borehole was drilled into the 1983 Chancellor underground nuclear test cavity to investigate the distribution of radionuclides within the cavity. Sidewall core samples were collected from a range of depths within the re-entry hole and two sidetrack holes. Upon completion of drilling, casing was installed and a submersible pump was used to collect groundwater samples. Test debris and groundwater samples were analyzed for a variety of radionuclides including the fission products 99 Tc, 125 Sb, 129 I, 137 Cs, and 155 Eu, the activation products 60 Co, 152 Eu, and 154 Eu, and the actinides U, Pu, and Am. In addition, the physical and bulk chemical properties of the test debris were characterized using Scanning Electron Microscopy (SEM) and Electron Microprobe measurements. Analytical results were used to evaluate the partitioning of radionuclides between the melt glass, rubble, and groundwater phases in the Chancellor test cavity. Three comparative approaches were used to calculate partitioning values, though each method could not be applied to every nuclide. These approaches are based on: (1) the average Area 19 inventory from Bowen et al. (2001); (2) melt glass, rubble, and groundwater mass estimates from Zhao et al. (2008); and (3) fission product mass yield data from England and Rider (1994). The U and Pu analyses of the test debris are classified and partitioning estimates for these elements were calculated directly from the classified Miller et al. (2002) inventory for the Chancellor test. The partitioning results from this study were compared to partitioning data that were previously published by the IAEA (1998). Predictions of radionuclide distributions from the two studies are in agreement for a majority of the nuclides under consideration. Substantial differences were noted in the partitioning values for 99 Tc, 125 Sb, 129 I, and uranium. These differences are attributable to two factors: chemical volatility effects that occur during the initial plasma condensation, and groundwater remobilization that occurs over a much longer time frame.

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Nuclear Melt Glass Dissolution and Secondary Mineral Precipitation at 40 to 200C

Cited by 5 publications

References 6 publications

A mechanistic model for long-term nuclear waste glass dissolution integrating chemical affinity and interfacial diffusion barrier

A mechanistic model for long-term nuclear waste glass dissolution integrating chemical affinity and interfacial diffusion barrier

Mapping of Uranium in Surrogate Nuclear Debris Using Laser-Induced Breakdown Spectroscopy (LIBS)

Radionuclide Partitioning in an Underground Nuclear Test Cavity

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