Long Term Modelling of Spent Fuel Oxidation/Dissolution Under Repository Conditions

2001 ◽  
Author(s):  
Juan Merino ◽  
Esther Cera ◽  
Jordi Bruno ◽  
Trygve Eriksen ◽  
Javier Quiñones ◽  
...  
Keyword(s):  
Source Term ◽  
Redox System ◽  
Water Interface ◽  
Spent Fuel ◽  
Fuel Oxidation ◽  
The Subject ◽  
The Stability ◽  
Thermodynamic Processes

Abstract A model to study the stability of the spent fuel under repository conditions has been developed. The fuel-water interface is a dynamic redox system, where oxidising conditions due to the radiolysis of water can lead to the release of the uranium and the radionuclides embedded in the fuel matrix. Both kinetic and thermodynamic processes have been taken into account. Special attention is given to the unit rate of matrix oxidation/dissolution, which has been the subject of a specific radiolytic model. The findings of this work have important implications for the applicability of solubility limits in establishing source term models.

Experimental determination and chemical modelling of radiolytic processes at the spent fuel/water interface

2000 ◽  
Vol 88 (9-11) ◽  
Author(s):  
J. Bruno ◽  
E. Cera ◽  
U.-B. Eklund ◽  
T. Eriksen ◽  
M. Grivé ◽  
...  
Keyword(s):  
Redox Potential ◽  
Redox System ◽  
Water Interface ◽  
Spent Fuel ◽  
Gamma Radiolysis ◽  
Chemical Modelling ◽  
Bulk System ◽  
The Stability ◽  
Radionuclide Release ◽  
Radiolytic Production

The spent fuel matrix constitutes a dynamic redox system, due to the time-dependent generation of oxidants and reductants at the spent fuel/water interface by alpha, beta and gamma radiolysis. In this context it is critical to understand the main processes and mechanisms that control the radiolytic production of redox components at this interface and their impact on the stability of the UOIn order to achieve this, a series of carefully controlled experiments have been carried out in order to determine the time dependence of the radiolytic HThe results of these experiments indicate quite a consistent and reproducible behaviour of the radiolytically generated reductants and oxidants. The results indicate that it is possible to define an equilibrium redox potential for the main redox pairs in the bulk system and that the experimentally determined radionuclide release can be rationalised in terms of the system redox potential.

The Assessment of the Long-Term Evolution of the Spent Nuclear Fuel Matrix by Kinetic, Thermodynamic and Spectroscopic Studies of Uranium Minerals.

1994 ◽  
Vol 353 ◽  
Author(s):  
Jordi Bruno ◽  
I. Casas ◽  
E Cera ◽  
R. C. Ewing ◽  
R. J. Finch ◽  
...  
Keyword(s):  
Nuclear Fuel ◽  
Safety Assessment ◽  
Source Term ◽  
Spent Nuclear Fuel ◽  
Spectroscopic Studies ◽  
Spent Fuel ◽  
Term Evolution ◽  
Uranium Minerals ◽  
The Stability

AbstractThe long term behaviour of spent nuclear fuel is discussed in the light of recent thermodynamic and kinetic data on mineralogical analogues related to the key phases in the oxidative alteration of uraninite. The implications for the safety assessment of a repository of the established oxidative alteration sequence of the spent fuel matrix are illustrated with Pagoda calculations. The application to the kinetic and thermodynamic data to source term calculations indicates that the appearance and duration of the U(VI) oxyhydroxide transient is critical for the stability of the fuel matrix.

On the Role of H2 as an Inhibitor of UO2 Matrix Dissolution

2007 ◽  
Author(s):  
Juan Merino ◽  
Xavier Gaona ◽  
Lara Duro ◽  
Jordi Bruno ◽  
Aurora Marti´nez-Esparza
Keyword(s):  
Chemical Composition ◽  
Partial Pressure ◽  
Water Radiolysis ◽  
Water Interface ◽  
Spent Fuel ◽  
Dissolution Rates ◽  
Term Stability ◽  
Long Term Stability

The study of spent fuel behaviour under disposal conditions is usually based on conservative approaches assuming oxidising conditions produced by water radiolysis at the fuel/water interface. However, the presence of H2 from container corrosion can inhibit the dissolution of the UO2 matrix and enhance its long-term stability. Several studies have confirmed the decrease in dissolution rates when H2 is present in the system, although the exact mechanisms of interaction have not been fully established. This paper deals with a radiolytic modelling exercise to explore the consequences of the interaction of H2 with radicals generated by radiolysis in the homogeneous phase. The main conclusion is that in all the modelled cases the presence of H2 in the system leads to a decrease in matrix dissolution. The extent of the inhibition, and the threshold partial pressure for the inhibition to take place, both depend in a complex way on the chemical composition of the water and the type of radiation present in the system.

Rim Instant Release Radionuclide Inventory From French High Burnup Spent UOX Fuel

2009 ◽  
Vol 1193 ◽  
Author(s):  
D. Roudil ◽  
C. Jegou ◽  
V. Broudic ◽  
M. Tribet
Keyword(s):  
Small Volume ◽  
Source Term ◽  
Nuclear Waste Repository ◽  
Spent Fuel ◽  
Waste Container ◽  
High Burnup ◽  
Radionuclide Release ◽  
Long Term Behavior ◽  
The Impact

AbstractTo assess the long-term behavior of spent fuel in a nuclear waste repository, the chemical reactions between the fuel and possible intruding water must be understood and the resulting radionuclide release must be quantified. The instant release fraction (IRF) source term assumed to be instantaneously accessible to water after the failure of the waste container. Some IRF values for different kinds of spent fuel are available in the literature. However, the possible contribution the rim restructured zone for high-burnup UOX fuels, was not necessary taken into account. A specific study of the leaching behavior of the rim zone has been carried out on a UOX fuel sample with a burnup of 60 GWd·t-1 and 2.8% FGR. The 134/137Cs and 90Sr rim IRF are effectively higher than the gap and grain boundary inventories (respectively 4.4 wt% and 0.3 wt% of the total Cs and Sr inventories). Nevertheless because of the relative small volume of this zone in the pellet, the impact of the rim inventory appears to be limited and the complete Cs and Sr IRF (gap, grain boundaries and rim), were estimated at 1.85 and 0.3 wt%, respectively

Source Trends for Performance Assessment of HLW Glass and Spent Fuel as Waste Forms

1997 ◽  
Vol 506 ◽  
Author(s):  
B. Grambow
Keyword(s):  
Mass Transfer ◽  
Performance Assessment ◽  
Source Term ◽  
Reaction Rates ◽  
Dissolution Mechanism ◽  
Experimental Measurements ◽  
Source Terms ◽  
Spent Fuel ◽  
Fuel Oxidation ◽  
Waste Forms

ABSTRACTwith respect to the state of validation for source term development. Consequences of the various mechanism on mass half lives of the waste forms are calculated with analytical equations. For glass the largest uncertainty stems from the yet unclear dissolution mechanism under silica saturated conditions. Source terms based on silica solubility coupled to Si-mass transfer are probably neither conservative nor realistic. For spent fuel the largest uncertainty is in the extrapolation of radiolytic fuel oxidation for long periods of time. Considering the uncertainties involved, reaction rates cannot yet be extrapolated reliably to values much lower than the lowest reliable experimental measurements.

scholarly journals The interplay among prey preference, nutrient enrichment and stability in an omnivory system

2009 ◽  
Vol 69 (4) ◽  
pp. 1027-1035 ◽  
Author(s):  
LDB. Faria ◽  
MIS. Costa
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Interactions ◽  
Nutrient Enrichment ◽  
Strong Influence ◽  
Prey Preference ◽  
Top Predator ◽  
The Subject ◽  
The Stability

Food webs usually display an intricate mix of trophic interactions where multiple prey are common. In this context omnivory has been the subject of intensive analysis regarding food web stability and structure. In a three species omnivory setting it is shown that the modeling of prey preference by the top predator may exert a strong influence on the short as well as on the long term dynamics of the respective food web. Clearly, this has implications concerning the stability and the structure of omnivory systems under disturbances such as nutrient enrichment.

scholarly journals Results from Long-Term Dissolution Tests Using Oxidized Spent Fuel

1990 ◽  
Vol 212 ◽  
Author(s):  
Charles N. Wilson
Keyword(s):  
Test Site ◽  
Fused Silica ◽  
Spent Fuel ◽  
Test Cycle ◽  
Release Rates ◽  
Fuel Oxidation ◽  
Dissolution Tests ◽  
J 13 ◽  
Fractional Release

ABSTRACTTwo semi-static dissolution tests using oxidized PWR spent fuel specimens are being conducted under ambient hot cell conditions in Nevada Test Site J-13 well water and unsealed fused silica vessels. The test specimens were oxidized at 250°C in air to bulk oxygen-to-metal (O/M) values of 2.21 and 2.33. Following an initial 191-day test cycle, the specimens were restarted in fresh J-13 water for a second long-term test cycle. Results through the first 40 months of Cycle 2 are compared with results from similar tests at 25°C and 85°C using unoxidized spent fuel specimens.Increased concentrations of U, Am, Cm and Np were measured in 0.4- μm filtered samples from the oxidized fuel tests compared to the unoxidized fuel tested at 25°C; Pu concentrations were not affected by the fuel oxidation state. Most of the Am and Cm, and a portion of the Pu, measured in 0.4-μm filtered samples was removed by 2-nm filtration. Fission product release results were normalized to specimen inventories and reported as fractional release. No attempt was made to normalize the data to surface area. Initial 99Tc release was greatly increased, and prolonged increases in the fractional release rates of 99Tc and 129I occurred as a result of fuel oxidation. Fractional release rates for 137Cs and 90Sr from oxidized fuel eventually decreased to levels similar to those observed with unoxidized fuel after equivalent testing times, suggesting that matrix dissolution rates normalized to fuel mass were not increased as a result of oxidation.

A Kinetic Model for the Stability of the Spent Fuel Matrix Under Oxic Conditions: Model Development Against Experimental Evidence

1996 ◽  
Vol 465 ◽  
Author(s):  
Jordi Bruno ◽  
E. Cera ◽  
L. Duro ◽  
T. E. Eriksen ◽  
P. Sellin ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Closed System ◽  
Model Development ◽  
Experimental Studies ◽  
Experimental Information ◽  
Spent Fuel ◽  
The Stability ◽  
Long Term Performance ◽  
Term Performance

ABSTRACTA kinetic model recently developed [1] for the radiolytically induced oxidative dissolution of the spent fuel matrix is presented. This is based on experimental studies on the generation and evolution of radiolytic products in a closed system containing fragments of PWR-fuel [2]. The outcome of this model is currently being integrated in the present PA exercise being prepared by SKB. The calibration of the model against various experimental information and its predictive capabilities for the long term performance of the spent fuel matrix are presented.

Experimental Investigation of Amine-Surfactant CO2 Foam Stability Enhanced by Silica Nanoparticles

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Liang Zhang ◽  
Jun Kang ◽  
Yin Zhang ◽  
Panfeng Zhang ◽  
Shaoran Ren ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Silica Nanoparticles ◽  
Foam Stability ◽  
Water Interface ◽  
High Adsorption ◽  
Long Term Stability ◽  
Co2 Foam ◽  
The Stability

The CO2 foam generated by the conventional surfactants usually does not show long-term stability due to the substantial solubility and diffusivity of CO2 in water. Silica nanoparticles with different wettability and high adsorption energy on the gas–water interface can be used as a stabilizer to enhance the stability of the CO2 foam. In this study, nine kinds of nonionic amine surfactants were employed to generate the CO2 foam, while three kinds of silica nanoparticles were selected and added to improve the CO2 foam stability. The influences of various factors, including pressure, temperature, pH, surfactant, and nanoparticle, on the CO2 foam stability have been investigated. The experimental results show that without nanoparticles, the CO2 foam stability decreases with the increase of the number of EO groups in the ethoxylated amine surfactant, especially under high-temperature and high-pressure (HTHP) conditions. In general, the nanoparticles with a low concentration (<0.5 wt %) have little influence on the CO2 foam stability, but when the concentration of nanoparticle is enhanced high enough (1.0 wt %), the CO2 foam stability can be improved significantly. In particular, by adding 1.0 wt % nanoparticle of QS-150 to 0.5 wt % surfactant of C18N(EO)2/10, the CO2 foam stability has been increased 5–6 times, while the volume of generated CO2 foam has been increased by 17–31%. Therefore, in this study, the synergetic mechanisms between the amine surfactants and the silica nanoparticles to generate and stabilize CO2 foam have been identified.

scholarly journals Energy potential of sustainable development of the region

2019 ◽  
Vol 135 ◽  
pp. 03023
Author(s):  
Botagoz Saparova ◽  
Aigerim Zhussupova ◽  
Bibinur Sydykova ◽  
Natalia Rud
Keyword(s):  
Economic Growth ◽  
Sustainable Development ◽  
Electric Power Industry ◽  
Energy Potential ◽  
The Sustainable Development ◽  
The Subject ◽  
The Stability ◽  
Relationship Of ◽  
The Relationship

At the present stage, the whole world is facing serious energy challenges, including the rapid growth of energy consumption, the inevitable exhaustion of energy resources with an extremely uneven distribution, a large environmental burden on nature, and the globalization of energy. The electric power industry harms the environment with its excessive emissions of pollutants, which is reflected globally. The article first of all offers a literary review of studies on this topic. A comparative description of the achievements of countries in the field of emission schedules is proposed, as well as the prospects for drawing up a schedule of emission intensity for the period up to 2030 in comparison with countries. In addition, this paper presents unresolved problems that impede sustainable development, which guarantees the stability of the future existence of mankind. These challenges hamper the sustainable development of the energy industry in the long term and the global sustainable development and prospects for green economic growth of the country. Thus, the relevance of the subject of the study is due to the lack of resources, reflecting the relationship of trends in reducing pollution from the activities of industry with the conditions of economic growth.

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