Radionuclides containment in nuclear glasses: an overview

2017 ◽  
Vol 105 (11) ◽  
Author(s):  
Stephane Gin ◽  
Patrick Jollivet ◽  
Magaly Tribet ◽  
Sylvain Peuget ◽  
Sophie Schuller
Keyword(s):  
Current Knowledge ◽  
Special Focus ◽  
Geological Time ◽  
Water Contact ◽  
Glass Processing ◽  
Waste Vitrification ◽  
Geological Repository ◽  
Glass Matrices ◽  
Long Term Behavior

AbstractRadioactive waste vitrification has been carried out industrially in several countries for nearly 40 years. Research into the formulation and long term behavior of high and intermediate level waste glasses, mainly borosilicate compositions, is still continuing in order to (i) safely condition new types of wastes and (ii) design and demonstrate the safety of the disposal of these long-lived waste forms in a deep geological repository. This article presents a summary of current knowledge on the formulation, irradiation resistance and the chemical durability of these conditioning materials, with a special focus on the fate of radionuclides during glass processing and aging. It is shown that, apart from the situation for certain elements with very low incorporation rate in glass matrices, vitrification in borosilicate glass can enable waste loadings of up to ~20 wt% while maintaining the glass homogeneity for geological time scales and guaranteeing a high stability level in spite of irradiation and water contact.

Evaluation of the long-term behavior of potential plutonium waste forms in a geological repository

2014 ◽  
Vol 1665 ◽  
pp. 23-30 ◽  
Author(s):  
Guido Deissmann ◽  
Stefan Neumeier ◽  
Felix Brandt ◽  
Giuseppe Modolo ◽  
Dirk Bosbach
Keyword(s):  
Current Knowledge ◽  
Geological Disposal ◽  
Ceramic Waste ◽  
Corrosion Rates ◽  
Waste Forms ◽  
Safety Margins ◽  
Geological Repository ◽  
Closure Conditions ◽  
Long Term Behavior

ABSTRACTVarious candidate waste matrices such as nuclear waste glasses, ceramic waste forms and low-specification “storage” MOX have been considered within the current UK geological disposal program for the immobilization of separated civilian plutonium, in the case this material is declared as waste. A review and evaluation of the long-term performance of potential plutonium waste forms in a deep geological repository showed that (i) the current knowledge base on the behavior and durability of plutonium waste forms under post-closure conditions is relatively limited compared to HLW-glasses from reprocessing and spent nuclear fuels, and (ii) the relevant processes and factors that govern plutonium waste form corrosion, radionuclide release and total systems behavior in the repository environment are not yet fully understood in detail on a molecular level. Bounding values for the corrosion rates of potential plutonium waste forms under repository conditions were derived from available experimental data and analogue evidence, taking into account that the current UK disposal program is in a generic stage, i.e. no preferred host rock type or disposal concept has yet been selected. The derived expected corrosion rates for potential plutonium waste forms under conditions relevant for a UK geological disposal facility are in the range of 10-4 to 10-2 g m-2 d-1 and 10-5 to 10-4 g m-2 d-1 for borosilicate glasses, and generic ceramic waste forms, respectively, and ∼5·10-6 g m-2 d-1 for storage MOX. More realistic assessments of the long-term behavior of the waste forms under post-closure conditions would require additional systematic studies regarding the corrosion and leaching behavior under more realistic post-closure conditions, to explore the safety margins of the various potential waste forms and to build confidence in long-term safety assessments for geological disposal.

Long-term behavior of R7T7-type nuclear glass: Current state of knowledge and outlook

2004 ◽  
Vol 824 ◽  
Author(s):  
S. Gin ◽  
N. Godon ◽  
I. Ribet ◽  
P. Jollivet ◽  
Y. Minet ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Influential Factors ◽  
Future Research ◽  
Operational Model ◽  
Geological Repository ◽  
Glass Current ◽  
Interim Storage ◽  
Parameter Values ◽  
Long Term Behavior

AbstractThis article reviews current knowledge of the long-term behavior of R7T7-type glass during the thermal phase and in geological repository conditions (aqueous alteration). In interim storage R7T7 glass can be considered to conserve its integrity over time. In geological repository conditions, the mechanisms of glass alteration by water have been identified and parameter values have been assigned to the reaction kinetics for wide variations of the influential factors (temperature, pH, flow rate, S/V ratio, etc.). CEA has developed an operational model to obtain robust and reasonably conservative predictions of the glass quantities altered after disposal. Examples of applications of the operational model are discussed, future research topics are also proposed to consolidate this approach.

Natural and Anthropogenic Analogues for High-Level Nuclear Waste Disposal Repositories: A Review

2021 ◽  
Author(s):  
Mostafa Fayek ◽  
Julie Brown
Keyword(s):  
Nuclear Waste ◽  
Spatial Scales ◽  
Deep Geological Repository ◽  
Geological Time ◽  
Geological Repository ◽  
Safety Case ◽  
Natural Analogues ◽  
High Level Nuclear Waste ◽  
High Level

ABSTRACT Projects involving deep geological disposal of nuclear waste are unique in that predictive models of long-term safety often involve geological timeframes. This manuscript provides a review of natural and anthropogenic analogues for high-level nuclear waste disposal in a deep geological repository. We also occasionally highlight analogues that have been used for low- and intermediate-level waste. Most studies define natural analogues as either naturally occurring or anthropogenic systems. In this paper, we distinguish between natural analogues and anthropogenic analogues because the latter generally provide non-technical (anecdotal) illustrations of concepts and processes for the safety case, whereas the former can provide technical and quantitative information. In addition, natural analogues can provide information over geological time scales (millions of years) and spatial scales (kilometers), whereas anthropogenic analogues provide information over a much more limited time scale (hundreds or thousands of years). Regardless of the definition, analogue studies provide one of the multiple lines of evidence intended to increase confidence in the safe geological disposal of high-level nuclear waste. They are deemed necessary because they complement the experiments that are carried out over a period of months or years. They also provide a way to validate numerical long-term safety assessment models with information and data covering geological time scales and spatial scales. The first part of this review describes the analogue concept. The second and third parts provide examples of natural and anthropogenic analogues for engineered barrier systems and natural barriers. Part four describes analogues for complex coupled transport processes. Finally, we discuss general and specific areas of future research. A concerted effort should be made to ensure that there is a transfer of data from the complex, natural analogue field studies to simplistic models which, by necessity, are used to evaluate the long-term safety of deep geological repositories. Field analogue studies should be planned to interface with laboratory experiments and, ultimately, with in situ field experiments, when the final repository site is selected. This will involve using natural analogue data in a quantitative way to support the deep geological repository safety case.

Use of Archaeological Glass to Predict the Long-Term Behavior of HLW

2009 ◽  
Vol 1193 ◽  
Author(s):  
S. Gin ◽  
A. Verney-Carron ◽  
G. Libourel
Keyword(s):  
Internal Crack ◽  
Secondary Phases ◽  
Crack Network ◽  
Geochemical Model ◽  
Kinetic And Thermodynamic Parameters ◽  
Geological Repository ◽  
Mediterranean Island ◽  
Leaching Experiments ◽  
Long Term Behavior

AbstractThe predictability of models describing long-term nuclear glass behavior in a geological repository can be tested by means of natural or archaeological analogs. This study covers fractured archaeological glass blocks from a shipwreck discovered near the Mediterranean island of Embiez (France). The blocks were examined mainly because of their morphological analogy with nuclear glasses. Fractured after production (as in the case of nuclear glass), these blocks had been leached for 1800 years in seawater. The laboratory investigation led to the development and subsequent validation on archaeological objects of a geochemical model capable of accurately simulating the coupling between chemistry and transport to account for the alteration state of the cracks according to their geometric characteristics. Laboratory experiments allowed us to determine the kinetic and thermodynamic parameters for modeling glass alteration. The model was then tested against short-term experiments before simulating the crack alteration over 1800 years. We show that cracks in the outer regions of the block are the most severely altered because of rapid solution renewal, whereas internal cracks are very slightly altered because of a rate-limiting effect of water transport due to the formation of secondary phases. This study also establishes a direct link between data obtained at lab scale and the long-term evolution of a complex system in a natural environment, indicating that the key phenomena have been identified experimentally. The analogous behavior of archaeological and nuclear glass during leaching experiments and the similarities in their crack networks allow us to consider applying the model to nuclear glasses under geological repository conditions. This study clearly shows that the internal crack network does not play a major role in the overall long-term alteration of archeological glass blocks. The issue of the transposition studies will be to determine whether this conclusion can be generalized to nuclear glasses.

Enrichment of Uranium inside Wood: a Natural Analog from a Sandstone-hosted Roll-type Uranium Ore Deposit

2004 ◽  
Vol 824 ◽  
Author(s):  
Huifang X ◽  
Maozhong Min ◽  
Jia Zhen ◽  
Xinjian Peng ◽  
Jinping Wang ◽  
...  
Keyword(s):  
Anaerobic Bacteria ◽  
Ore Deposit ◽  
Uranium Ore ◽  
Natural Analog ◽  
Geological Repository ◽  
Roll Type ◽  
Wooden Furniture ◽  
Carbonized Wood ◽  
Long Term Behavior

AbstractFurniture contaminated with uranium will be disposed of, together with U-bearing waste, in ageological repository such as the WIPP site in New Mexico. It is important to understand the effect of the wooden furniture on the migration of uranium in order to predict long-term behavior of uranium in a geological repository environment. In this paper, we present natural uraninite-bearing carbonized wood pieces from a sandstone-hosted roll-type uranium ore deposit in NW China. Results from SEM and TEM observations show that there are nanometer sized, and micron-sized, uraninite crystals that have accumulated on cell walls of the carbonized wood. Some uranitite crystrals display oval and round shapes that may be the result of microbial-induced reduction of uranium from groundwater. The wood carbonized fragments are the most uranium-rich “phase.” In some areas, aggregates of pyrite crystals occur withthe uraninite. It is proposed that organic components from the decay of the wood cells provide nutrientsfor the anaerobic bacteria to grow. The wood pieces with the bacteria inside may serve as scavengers of uranium because of the local reducing chemical environment.

Long-Term Stable Metal Organic Framework (MOF) Based Mixed Matrix Membranes for Ultrafiltration

2020 ◽  
Author(s):  
Muayad Al-shaeli ◽  
Stefan J. D. Smith ◽  
Shanxue Jiang ◽  
Huanting Wang ◽  
Kaisong Zhang ◽  
...  
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Mixed Matrix Membranes ◽  
Recovery Ratio ◽  
Mixed Matrix ◽  
Water Contact ◽  
Membrane Performance ◽  
Metal Organic ◽  
Matrix Membranes

<p>In this study, novel <a>mixed matrix polyethersulfone (PES) membranes</a> were synthesized by using two different kinds of metal organic frameworks (MOFs), namely UiO-66 and UiO-66-NH<sub>2</sub>. The composite membranes were characterised by SEM, EDX, FTIR, PXRD, water contact angle, porosity, pore size, etc. Membrane performance was investigated by water permeation flux, flux recovery ratio, fouling resistance and anti-fouling performance. The stability test was also conducted for the prepared mixed matrix membranes. A higher reduction in the water contact angle was observed after adding both MOFs to the PES and sulfonated PES membranes compared to pristine PES membranes. An enhancement in membrane performance was observed by embedding the MOF into PES membrane matrix, which may be attributed to the super-hydrophilic porous structure of UiO-66-NH<sub>2</sub> nanoparticles and hydrophilic structure of UiO-66 nanoparticles that could accelerate the exchange rate between solvent and non-solvent during the phase inversion process. By adding the MOFs into PES matrix, the flux recovery ratio was increased greatly (more than 99% for most mixed matrix membranes). The mixed matrix membranes showed higher resistance to protein adsorption compared to pristine PES membranes. After immersing the membranes in water for 3 months, 6 months and 12 months, both MOFs were stable and retained their structure. This study indicates that UiO-66 and UiO-66-NH<sub>2</sub> are great candidates for designing long-term stable mixed matrix membranes with higher anti-fouling performance.</p>

scholarly journals Impact of mobile stroke units

2021 ◽  
pp. jnnp-2020-324005
Author(s):  
Klaus Fassbender ◽  
Fatma Merzou ◽  
Martin Lesmeister ◽  
Silke Walter ◽  
Iris Quasar Grunwald ◽  
...  
Keyword(s):  
Cost Efficiency ◽  
Current Knowledge ◽  
Vascular Imaging ◽  
Vessel Occlusion ◽  
Stroke Units ◽  
Stroke Treatment ◽  
Stroke Research ◽  
Mobile Stroke Unit ◽  
Novel Strategy

Since its first introduction in clinical practice in 2008, the concept of mobile stroke unit enabling prehospital stroke treatment has rapidly expanded worldwide. This review summarises current knowledge in this young field of stroke research, discussing topics such as benefits in reduction of delay before treatment, vascular imaging-based triage of patients with large-vessel occlusion in the field, differential blood pressure management or prehospital antagonisation of anticoagulants. However, before mobile stroke units can become routine, several questions remain to be answered. Current research, therefore, focuses on safety, long-term medical benefit, best setting and cost-efficiency as crucial determinants for the sustainability of this novel strategy of acute stroke management.

scholarly journals Cardiac Cell Therapy: Insights into the Mechanisms of Tissue Repair

2021 ◽  
Vol 22 (3) ◽  
pp. 1201
Author(s):  
Hsuan Peng ◽  
Kazuhiro Shindo ◽  
Renée R. Donahue ◽  
Ahmed Abdel-Latif
Keyword(s):  
Stem Cell ◽  
Immune Responses ◽  
Tissue Repair ◽  
Molecular Mechanisms ◽  
Clinical Evidence ◽  
Current Knowledge ◽  
Cell Delivery ◽  
Cardiac Cell Therapy ◽  
Stem Cell Treatment

Stem cell-based cardiac therapies have been extensively studied in recent years. However, the efficacy of cell delivery, engraftment, and differentiation post-transplant remain continuous challenges and represent opportunities to further refine our current strategies. Despite limited long-term cardiac retention, stem cell treatment leads to sustained cardiac benefit following myocardial infarction (MI). This review summarizes the current knowledge on stem cell based cardiac immunomodulation by highlighting the cellular and molecular mechanisms of different immune responses to mesenchymal stem cells (MSCs) and their secretory factors. This review also addresses the clinical evidence in the field.

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