Solid state diffusion during nuclear glass residual alteration in solution

Chave, Tony; Frugier, Pierre; Ayral, A.; Gin, Stéṕhane

doi:10.1016/j.jnucmat.2007.01.095

Cited by 83 publications

(110 citation statements)

References 16 publications

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“…This is consistent with the fact that, at high S/V ratio, processes leading to the boron release 30,31 become slower with increasing pH. 32 Alteration rates measured during the latency period (r P ) and the r RA are reported in Table 1. r RA is defined as the rate reached since the inflection point following the latency period and until the total alteration of the glass sample is about to be reached (or the end of the experimental period).…”

Section: Unseeded Leaching Testssupporting

confidence: 82%

Contribution of zeolite-seeded experiments to the understanding of resumption of glass alteration

et al. 2017

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Understanding the origin and the consequences of glass alteration regimes is necessary for the prediction of nuclear glass durability. The so-called "stage 3" or "resumption of alteration regime" of glasses used to sequester nuclear waste by vitrification, is characterized by a sudden acceleration of glass alteration rate arising from the precipitation of secondary minerals, mainly zeolites. To study this process, a promising approach is developed, based on seeding by synthesized zeolite seeds. This study quantitatively links the alteration of a six-oxide reference borosilicate glass (ISG) and the precipitation of zeolites that affects concentrations of key species-in particular aluminum-and thus the glass dissolution rate. The characterization of stage 3-easier at alkaline pH-can now be extended to pH conditions more representative of those found in a geological repository thanks to seeding that reduces, or even eliminates, the latency period preceding a resumption of glass alteration. The resumption occurrence and glass dissolution rate are related with temperature and pH. This study shows that the detrimental effect of zeolite precipitation decreases with decreasing pH and temperature, until it is no longer detectable at a pH around 9 imposed by the dissolution of the ISG glass. Even for both high temperature and high pH, the resumption rate is lower than the initial alteration rate, which remains the fastest kinetic regime.npj Materials Degradation (2017) 1:17 ; doi:10.1038/s41529-017-0018-x INTRODUCTION Like the United Kingdom, Japan, Russia and India, France has chosen to reprocess spent nuclear fuel. Ultimate waste arising from this recycling process-consisting of fission products and minor actinides-are confined by vitrification. The reference solution for the management of these waste packages over geological time scales is their storage in a deep, low-permeability and stable geological formation.In contact with water, the vitrified product of waste, usually called "nuclear glass", undergoes both dissolution and irreversible transformation into more stable phases; the rate of this transformation strongly depends on geochemical conditions. Formation of a passivating layer (also called "gel") causes the reduction of the initial alteration rate r 0 -due to the hydrolysis of the vitreous network by nucleophilic substitution of hydroxide ions-until the persistence of a residual rate. For a glass, this gel can exhibit a great variability in composition-and thus in properties-depending on the environmental parameters, in particular pH, temperature and solution composition. Gel stability and its passivation properties allow-under the most favorable conditions-a glass package lifetime of hundreds of thousands to millions of years. However, a resumption of alteration (RA, also called "stage 3" in the literature)-i.e., a sudden acceleration of the glass alteration rate-can occur.1,2 Resumptions of alteration have been observed in specific experimental conditions, particularly in alkaline environments-as a conseque...

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Section: Unseeded Leaching Testssupporting

confidence: 82%

Contribution of zeolite-seeded experiments to the understanding of resumption of glass alteration

et al. 2017

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“…We used SON68 glass as a reference, since its dissolution has been widely studied, e.g. Frugier et al (2008), Ribet and Gin (2004) and Chave et al (2007).…”

Section: Glass Dissolution In Alkaline Solutionmentioning

confidence: 99%

Transport- and surface reaction-controlled SON68 glass dissolution at 30°C and 70°C and pH=13.7

Liu

Ferrand

Lemmens

2015

Applied Geochemistry

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“…There is no general agreement on the cause of this rate reduction. Two theories suggest that it is due to:(a) chemical affinity change [13,[42][43][44][45][46][47]; and(b) diffusion barrier effect [14,15,48,[51][52][53][54], or the combination of both [17,49,50].…”

Section: Rate Drop and Residual Ratementioning

confidence: 99%

“…First, the model emphasizes the IDB, which has key effect on both diffusion and the chemical affinity. Researchers from Marcoule Laboratory had done a lot of work on the protective alteration layer and made great progresses [14,15,48,[51][52][53]64,65]. But still, much work needs to be done further.…”

Section: Recommendationsmentioning

confidence: 99%

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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Solid state diffusion during nuclear glass residual alteration in solution

Cited by 83 publications

References 16 publications

Contribution of zeolite-seeded experiments to the understanding of resumption of glass alteration

Contribution of zeolite-seeded experiments to the understanding of resumption of glass alteration

Transport- and surface reaction-controlled SON68 glass dissolution at 30°C and 70°C and pH=13.7

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

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