scholarly journals Alpha dose rate and decay dose impacts on the long-term alteration of HLW nuclear glasses

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Magaly Tribet ◽  
Caroline Marques ◽  
Sarah Mougnaud ◽  
Véronique Broudic ◽  
Christophe Jegou ◽  
...  
Keyword(s):  
Dose Rate ◽  
Chemical Reactivity ◽  
Alpha Decay ◽  
Glass Block ◽  
Alpha Radiation ◽  
Wide Range ◽  
High Level ◽  
Static Conditions ◽  
Doped Glass

AbstractIn the prospect of deep geological disposal, the long-term behavior of high-level nuclear glasses has to be investigated regarding alpha radiation induced by long-life minor actinides. The present study focuses on the effects of alpha radiation on the long-term chemical reactivity of R7T7-type glasses, by separately considering the alpha dose rate and the alpha decay dose. Old SON68 glasses doped with 238/239PuO2 or 244CmO2 were studied to simulate high alpha dose rates corresponding to an early water ingress and a high level of alpha decay doses corresponding to long-term disposal conditions. A part of the 238/239Pu-doped glass block was annealed to fully recover the irradiation-induced damage accumulated since the glass was fabricated and to dissociate the effect of the alpha dose rate from that of the alpha decay dose. The glasses were then leached under static conditions at 90 °C for several years. The results showed that the residual alteration rate is not affected by the alpha dose rate over a wide range of dose rate values expected under disposal conditions: this glass remained relatively insensitive to the alpha radiolysis phenomena at the glass–water interface. However, over the duration of the experiments, the residual alteration rate of the damaged 238/239Pu-doped glass was enhanced compared to that of the annealed glass. This result is in agreement with those obtained on the 244Cm-doped glass and with reported values in the literature on simplified externally irradiated glasses, indicating that the ballistic effects of the recoil nuclei are responsible for this increase in the residual alteration rate.

Long-term aqueous alteration kinetics of an alpha-doped SON68 borosilicate glass

2013 ◽  
Vol 1518 ◽  
pp. 9-14 ◽  
Author(s):  
Magaly Tribet ◽  
Séverine Rolland ◽  
Sylvain Peuget ◽  
Magali Magnin ◽  
Véronique Broudic ◽  
...  
Keyword(s):  
Radiation Effects ◽  
Chemical Reactivity ◽  
Pure Water ◽  
High Surface ◽  
Protective Layer ◽  
Chemical Oxidation ◽  
Alpha Radiation ◽  
Sem And Tem ◽  
Static Conditions

ABSTRACTThe long-term behavior of nuclear glass subjected to alpha radiation by minor actinides must be investigated with a view to geological disposal. This study focuses on the effect of alpha radiation on the chemical reactivity of R7T7 glass with pure water, mainly on the residual alteration rate regime. A glass specimen doped with 0.85 wt% 239PuO2 (α emitter) is leached under static conditions in argon atmosphere at 90°C and at a high surface-area-to-volume ratio (S/V = 20 cm−1). The alteration rate is monitored by the release of glass alteration tracer elements (B, Na and Li). Radiation effects on the leached glass and its gel network are characterized by SEM and TEM analyses. Plutonium release is also measured by radiometry and its chemical oxidation state is assessed by measuring the pH and redox potential of the leachates. The results do not highlight any significant effect of alpha radiation on the residual alteration of this doped glass. This observation is consistent with SEM and TEM characterizations, which show that a protective layer can be formed under alpha radiation. Very low concentrations of soluble plutonium are measured in the leachate. These Pu releases are three orders of magnitude lower than the boron release, indicating strong plutonium retention.

Durability of potential plutonium wasteforms under repository conditions

2012 ◽  
Vol 76 (8) ◽  
pp. 2911-2918 ◽  
Author(s):  
G. Deissmann ◽  
S. Neumeier ◽  
G. Modolo ◽  
D. Bosbach
Keyword(s):  
Chemical Reactivity ◽  
Final Decision ◽  
Geological Disposal ◽  
Aqueous Environments ◽  
Safety Case ◽  
Key Issues ◽  
The Uk ◽  
High Level ◽  
Radionuclide Release

AbstractSeparated stocks of UK civil plutonium are currently held as a zero value asset in storage, as there is no final decision about whether they should be treated as a resource for future use as nuclear fuel or as waste. Irrespective of future UK government strategies regarding plutonium, at least a portion of the UK civil plutonium inventory will be designated for geological disposal. In this context, we performed a high-level review of the performance of potential wasteforms for the disposal of separated civil plutonium. The key issues considered were the durability and chemical reactivity of the wasteforms in aqueous environments and the long-term radionuclide release under conditions relevant to geological disposal. The major findings of the review, relevant not only to the situation in the UK but to plutonium disposal in general, are summarized in this paper. The review showed that, in the event of a decision being taken to declare plutonium as a waste for disposal, more systematic studies would be required to constrain the wasteform performance under repository conditions in order to derive realistic source terms for a safety case.

Long-Term Radioactivity Release from Solidified High-Level Waste - Part II Parametric Study of Waste form Properties, Temperature and Time

1982 ◽  
Vol 15 ◽  
Author(s):  
Friedrich K. Altenhein ◽  
Werner Lutze ◽  
Rodney C. Ewing
Keyword(s):  
Parametric Study ◽  
Computer Code ◽  
Salt Dome ◽  
Waste Form ◽  
Glass Block ◽  
High Level Waste ◽  
Surface Layers ◽  
History Of ◽  
High Level

The computer code QTERM has been used to calculate the total released activity from a single glass block when in contact with brine in a salt dome repository as a function of: (1) waste form properties, (2) leaching mechanisms, (3) retention or precipitation of specific radionuclides in surface layers, (4) thermal history of the repository and (5) decreasing activity as a function of time.

Disposal of high-level nuclear wastes: a geological perspective

1985 ◽  
Vol 49 (351) ◽  
pp. 159-176 ◽  
Author(s):  
A. E. Ringwood
Keyword(s):  
Elevated Temperatures ◽  
Great Majority ◽  
Nuclear Industry ◽  
High Level Waste ◽  
Public Confidence ◽  
Wide Range ◽  
Close Relatives ◽  
High Level ◽  
Drill Holes

AbstractMost countries intend to dispose of their high-level radioactive wastes by converting them into a solidified wasteform which is to be buried within the earth. SYNROC is a titanate ceramic wasteform which has been designed for this purpose on the basis of geochemical principles. It comprises essentially rutile TiO2, ‘hollandite’ Ba(Al,Ti)Ti6O16, zirconolite CaZrTi2O7, and perovskite CaTiO3. The latter three phases have the capacity to accept the great majority of radioactive elements occurring in high-level wastes into their crystal lattice sites. These minerals (or their close relatives) also occur in nature, where they have demonstrated their capacity to survive for many millions of years in a wide range of geological environments. The properties of SYNROC and the crystal chemistry of its constituent minerals are reviewed in some detail and current formulations of SYNROC are summarized. A notable property of SYNROC it its extremely high resistance to leaching by groundwaters, particularly above 100°C. In addition, it can be shown that the capacity of SYNROC minerals to immobilize high-level waste elements is not markedly impaired by high levels of radiation damage. Current investigations are focused on developing a satisfactory production technology for SYNROC and progress towards this objective is described. The high leach resistance of SYNROC at elevated temperatures increases the range of geological environments in which the waste may be finally interred; in particular, SYNROC is well adapted for disposal in deep drill-holes, both in continental and marine environments. The fact that SYNROC is comprised of minerals which have demonstrated long-term geological stability is significant in establishing public confidence in the ability of the nuclear industry to immobilize high-level wastes for the very long periods required.

Assessing the durability of nuclear glass with respect to silica controlling processes in a clayey underground disposal

2006 ◽  
Vol 932 ◽  
Author(s):  
Laurent De Windt ◽  
Stéphanie Leclercq ◽  
Jan van der Lee
Keyword(s):  
Host Rock ◽  
Reactive Transport ◽  
Transport Model ◽  
Glass Block ◽  
High Level Waste ◽  
Residual Rate ◽  
Glass Dissolution ◽  
Underground Disposal ◽  
High Level

ABSTRACTThe long-term behaviour of vitrified high-level waste in an underground clay repository was assessed by using the reactive transport model HYTEC with respect to silica diffusion, sorption and precipitation processes. Special attention was given to the chemical interactions between glass, corroded steel and the host-rock considering realistic time scale and repository design. A kinetic and congruent dissolution law of R7T7 nuclear glass was used assuming a first-order dissolution rate, which is chemistry dependent, as well as a long-term residual rate. Without silica sorption and precipitation, glass dissolution is diffusion-driven and the fraction of altered glass after 100,000 years ranges from 5% to 50% depending on the fracturation degree of the glass block. Corrosion products may limit glass dissolution by controlling silica diffusion, whereas silica sorption on such products has almost no effect on glass durability. Within the clayey host-rock, precipitation of silicate minerals such as chalcedony may affect glass durability much more significantly than sorption. In that case, however, a concomitant porosity drop is predicted that could progressively reduce silica diffusion and subsequent glass alteration.

Structure and alteration kinetics of rare-earth rich borosilicate glasses with (64 – 2x) SiO2 / 18 B2O3 / 18 Na2O / x RE2O3 composition (RE = Y or Eu+ La)

2010 ◽  
Vol 1265 ◽  
Author(s):  
Odile Majerus ◽  
Daniel Caurant ◽  
Ning Li ◽  
Jean-Baptiste Baudouin ◽  
Gabriela Manolescu ◽  
...  
Keyword(s):  
Rare Earth ◽  
Borosilicate Glasses ◽  
Altered Layer ◽  
Waste Load ◽  
High Level Nuclear Waste ◽  
Rapid Hydrolysis ◽  
High Level ◽  
Static Conditions ◽  
Kinetics Of

AbstractThe high level nuclear waste load is likely to increase in the future containment glasses, rising new questions about their long-term chemical durability. In this study sodium borosilicate compositions with Si substituted for RE (RE = rare earth) are altered under static conditions at fixed pH (8.5). The Na and B leached fractions reached just after the rate drop increase with the RE2O3 content. Part of the RE ions remain in the altered layer which is significantly de-polymerised (IR-ATR and NMR results). Their environment is reorganized and adopts a more centrosymetrical character. The higher leached fractions are attributed to rapid hydrolysis of Si/B-O-RE bonds with respect to Si-O-Si bonds.

scholarly journals Pharmacological cardioversion of atrial fibrillation paroxysm in elderly and senile patients at prehospital stage

2021 ◽  
Vol 2 (3) ◽  
pp. 26-32
Author(s):  
Andrei V. Syrov ◽  
◽  
Keyword(s):  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Heart Rhythm ◽  
Day Hospital ◽  
Drug Of Choice ◽  
Wide Range ◽  
Rhythm Disorder ◽  
Pharmacological Cardioversion ◽  
High Level

Atrial fibrillation (AF) is the most common heart rhythm disorder requiring treatment and is associated with an increased rate of hospitalization and death. When choosing the tactics of restoring and maintaining sinus rhythm in most patients with AF paroxysm without pronounced organic heart damage, the drug of choice is propafenone, which has a high level of safety and efficacy. The use of the drug within the framework of a «pill in a pocket» by the patient himself, intravenously in a day hospital of an outpatient medical institution or by an ambulance team allows stopping AF paroxysm in most patients at the prehospital stage. Propafenone is also the drug of choice for inpatient sinus rhythm restoration and for long-term antiarrhythmic therapy in a wide range of patients with AF.

Effect of Alpha Decay on Nuclear Borosilicate Glass Properties

2004 ◽  
Vol 824 ◽  
Author(s):  
Sylvain Peuget ◽  
Christophe Jégou ◽  
Véronique Broudic ◽  
Danièle Roudil ◽  
Xavier Deschanels ◽  
...  
Keyword(s):  
Alpha Decay ◽  
High Level Waste ◽  
Minor Actinide ◽  
Borosilicate Glasses ◽  
Leaching Behavior ◽  
Doped Glasses ◽  
High Burnup ◽  
High Level ◽  
Doped Glass ◽  
Glass Properties

AbstractThe properties of actinide glasses are studied in the context of high-level waste management programs. Reprocessing high burnup fuels in particular will increase the minor actinide content in the glass package, resulting in higher cumulative alpha decay doses in the glass, and raising the question of the glass matrix behavior and especially its containment properties. The effect of alpha self-irradiation on the glass behavior is evaluated by doping the glass with a short-lived actinide (244Cm) to reach in several years the alpha dose received by the future glass packages over several thousand years. “R7T7” borosilicate glasses were doped with 3 different curium contents (0.04 wt%, 0.4 wt% and 1.2 wt% 244CmO2). The glass homogeneity was characterized by SEM and XRD. Chemical analysis after dissolution of the glass confirmed the chemical composition. The curium content and its distribution in the glass specimens were checked by calorimetry measurements and gamma spectrometry on 243Cm and 245Cm isotopes. The density and mechanical properties of the curium-doped glasses were characterized up to 2 × 1018 α/g, revealing only a slight evolution of the macroscopic behavior of R7T7 glass in this range. The leaching behavior of curium-doped glass was also studied by Soxhlet tests. The results do not show any significant evolution of the initial alteration rate with the alpha dose.

scholarly journals Disordered eating and eating disorders in male elite athletes: a scoping review

2020 ◽  
Vol 6 (1) ◽  
pp. e000801
Author(s):  
Yannis Karrer ◽  
Robin Halioua ◽  
Sonja Mötteli ◽  
Samuel Iff ◽  
Erich Seifritz ◽  
...  
Keyword(s):  
Eating Disorders ◽  
Disordered Eating ◽  
Scoping Review ◽  
Elite Athletes ◽  
Adolescent Male ◽  
Wide Range ◽  
High Prevalence ◽  
Sport Type ◽  
High Level

BackgroundEating disorders (ED) and disordered eating (DE) among male elite athletes share some of the characteristics seen in female elite athletes and the population, but also exhibit some key differences.ObjectiveScoping review of ED and DE in male elite athletes.MethodsIn May 2020, a comprehensive systematic literature search was conducted for DE and ED in male elite athletes.ResultsWe identified 80 studies which included 47 uncontrolled, 14 controlled studies, one interventional trial and 18 reviews.DiscussionThere was a wide range of definitions of DE and a high level of heterogeneity regarding competitive level, age and sport type. In adult male elite athletes, ED prevalence rates up to 32.5% were found, higher than in the general population. Prevalence was not higher in young/adolescent male elite athletes. The most frequently associated factor was competing in weight-sensitive sports. Male elite athletes tended to exhibit less body dissatisfaction than controls and were not always associated with DE. There were no studies looking at the prognosis or reporting an evidence-based approach for the management of DE in male elite athletes.ConclusionExisting literature indicates high prevalence of DE and ED in male elite athletes, with a wide range of aetiopathogenesis. There is a need for longitudinal studies to characterise the pathology and long-term outcomes, as well as develop standardised tools for assessment and treatments.

Crystal Chemistry of Natural Zirconolite: Implications for High-Level Waste Incorporation in Synroc

1997 ◽  
Vol 506 ◽  
Author(s):  
Reto Gierpé ◽  
C. Terry Williams ◽  
Gregory R. Lumpkin
Keyword(s):  
Statistical Study ◽  
Alpha Decay ◽  
High Level Waste ◽  
Rock Types ◽  
Naturally Occurring ◽  
Geological Conditions ◽  
Wide Range ◽  
Alteration Processes ◽  
High Level Nuclear Waste ◽  
High Level

ABSTRACTZirconolite, ideally CaZrTi2O7, is a relatively rare mineral crystallizing at different geological conditions and in a wide range of generally SiO2-poor rock types. Synthetic zirconolite is one of two major actinide (ACT) host phases in SYNROC, a very promising option for the disposal of high-level nuclear waste (HLW). The available samples of naturally occurring zirconolite cover an extensive range in ACT content, age and host rock type, and thus offer an ideal opportunity to study the relationships between alpha-decay doses, radiation damage, and geochemical alteration processes [1]. In this paper, we present results obtained from a statistical study of nearly 300 chemical analyses of natural zirconolite [2].

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