The effect of cellulose degradation products on thorium sorption onto hematite: studies of a model ternary system

2012 ◽  
Vol 76 (8) ◽  
pp. 3381-3390 ◽  
Author(s):  
G. M. N. Baston ◽  
M. M. Cowper ◽  
T. G. Heath ◽  
T. A. Marshall ◽  
S. W. Swanton
Keyword(s):  
Degradation Products ◽  
Cellulose Degradation ◽  
Near Field ◽  
Principal Component ◽  
High Concentration ◽  
Sorption System ◽  
Model Predictions ◽  
The Impact ◽  
Isosaccharinic Acid ◽  
Good Agreement

AbstractCellulose degradation products (CDPs) can complex with radioelements causing solubility enhancement and sorption reduction, effects which are detrimental to the containment of radionuclides in the near field of a geological disposal facility and surrounding geosphere. Isosaccharinic acid (ISA) is the principal component of CDPs formed under the alkaline anaerobic conditions of a cement-based near field and appears to be largely responsible for the impact of CDPs on radionuclide solubility and sorption under near-field conditions. However, the situation appears to be more complicated under near-neutral pH geosphere conditions.A combined experimental and modelling study was undertaken to compare the impact of a CDP leachate to ISA in a simple model ternary sorption system consisting of hematite as a single mineral substrate, thorium as the radioelement and ISA or a CDP leachate as the complexant. Thorium sorbs strongly to hematite. A triple layer model for thorium sorption to hematite was refined to fit to the experimental data in the absence of ISA or CDP leachate; the effect of ISA on thorium sorption was then predicted.In the presence of CDP leachate, a significant reduction in thorium sorption was observed from pH 6 to 12 in good agreement with model predictions based on a high concentration of ISA. However, only a limited impact of ISA on thorium sorption was observed at pH 6 to 12, in contrast to predictions. The effects of ISA could be accounted for by assuming the formation of a ternary thorium–ISA–surface complex. The model has yet to be extended to the more complex CDP systems. Differences in the thorium speciation in solution due to the formation of a ternary calcium–thorium–ISA complex in the CDP leachate, which is absent from solutions with ISA only, provides the most likely explanation for the differences observed experimentally.

The Identification and Degradation of Isosaccharinic Acid, a Cellulose Degradation Product

1994 ◽  
Vol 353 ◽  
Author(s):  
B. F. Greenfield ◽  
G. J. Holtom ◽  
M. H. Hurdus ◽  
N. O’Kelly ◽  
N.J. Pilkington ◽  
...  
Keyword(s):  
High Performance ◽  
Degradation Products ◽  
Cellulose Degradation ◽  
Near Field ◽  
Experimental Studies ◽  
Water Soluble ◽  
Chemical Degradation ◽  
Alkaline Conditions ◽  
Isosaccharinic Acid ◽  
Microbial Action

AbstractNirex is seeking to develop a deep underground repository for the disposal of solid intermediate-level and low-level radioactive wastes (ILW and LLW) in the UK. One possible influence on the behaviour of radionuclides is the formation of water-soluble complexants by the degradation of the solid organic polymers that will be present in the wastes. The degradation products of cellulose have been shown to increase the solubility of plutonium and other radionuclides and to reduce sorption onto near-field and far-field materials. Degradation of cellulose under anaerobic alkaline conditions produces a range of organic acids. In this paper 2-C-(hydroxymethyl)-3-deoxy-D-pentonic acid (isosaccharinic acid, ISA) is identified by High Performance Liquid Chromatography as a significant component of cellulose leachates. A combination of fractionation of cellulose leachates and plutonium solubility determinations shows that ISA is responsible for the majority of the enhancement of plutonium solubility observed in such leachates. Further degradation of ISA by chemical or microbial action may lessen the effect of degraded cellulose leachates. Experimental studies on the chemical degradation of this compound under alkaline conditions suggest that the presence of oxygen is required. Microbial degradation studies show that the plutonium solubility in solutions of ISA is reduced by their exposure to microbial action.

Sorption of radionuclides to a cementitious backfill material under near-field conditions

2012 ◽  
Vol 76 (8) ◽  
pp. 3401-3410 ◽  
Author(s):  
M. Felipe-Sotelo ◽  
J. Hinchliff ◽  
N. Evans ◽  
P. Warwick ◽  
D. Read
Keyword(s):  
Organic Compounds ◽  
Degradation Products ◽  
Cellulose Degradation ◽  
Near Field ◽  
Organic Ligand ◽  
Sorption Isotherms ◽  
Field Conditions ◽  
Sorption Behaviour ◽  
Backfill Material ◽  
Order Of Magnitude

AbstractThe sorption behaviour of I−, Cs+, Ni2+, Eu3+, Th4+ and UO2+2on NRVB (Nirex reference vault backfill) a possible vault backfill, at pH 12.8 was studied. Sorption isotherms generated were compared to results obtained in the presence of cellulose degradation products (CDP). Whereas Cs was not affected by the presence of the organic compounds, a notable reduction in the sorption of Th and Eu to cement was observed. The results also indicated limited removal of Ni from solution (with or without an organic ligand) by sorption, the concentration in solution seemingly being determined solely by solubility processes. In the case of uranium, the presence of CDP increased the sorption to cement by almost one order of magnitude. Further studies into the uptake of CDP by cement are being undertaken to identify the mechanism(s) responsible.

The Effect of Cellulose Degradation Products on the Solubility and Sorption of Pu and Am in Alkaline-Plume-Affected and in Unaffected Boom Clay

2003 ◽  
Vol 807 ◽  
Author(s):  
F. Rorif ◽  
E. Valcke ◽  
M. A. Glaus
Keyword(s):  
Radioactive Waste ◽  
Water Sorption ◽  
Degradation Products ◽  
Cellulose Degradation ◽  
Potential Effect ◽  
Water Soluble ◽  
Boom Clay ◽  
Effect Of Water ◽  
Isosaccharinic Acid

ABSTRACTThe potential effect of water-soluble degradation products (DPs) formed from cellulose-containing cemented radioactive waste on the behaviour of Pu(IV) and Am(III) in Alkaline-Plume-Affected (APA) and in unaffected Boom clay was assessed. After solubility measurements in APA Real Clay Water, sorption experiments of Pu(IV) and Am(III) onto APA Boom clay were performed in the presence or not of DPs or pure α-isosaccharinic acid (α-ISA). Moreover, the sorption of α-ISA onto the unaffected clay was studied.

The Degradation of Cellulose in the Near Field of a Radioactive Waste Repository

1993 ◽  
Vol 333 ◽  
Author(s):  
B.F. Greenfield ◽  
M.H. Hurdus ◽  
N.J. Pilkington ◽  
M.W. Spindler ◽  
S.J. Williams
Keyword(s):  
Degradation Products ◽  
Cellulose Degradation ◽  
Near Field ◽  
Research Programme ◽  
Water Soluble ◽  
Anaerobic Conditions ◽  
Factors Affecting ◽  
Deep Underground ◽  
The Uk ◽  
Assessment Research

ABSTRACTUK Nirex Ltd is seeking to develop a deep underground repository for the disposal of solid low- and intermediate-level radioactive wastes in the UK. The Nirex Safety Assessment Research Programme (NSARP) comprises scientific research to support the post-closure performance assessment of the repository. One of the investigations carried out by AEA Technology under the NSARP is the investigation of the formation of water-soluble complexants from the degradation of the solid organic polymers and cellulosic materials present in such wastes. The influence of these complexants on the solubility and sorption of a number of radionuclides is also being investigated by a combination of experimental measurements and thermodynamic modelling. Under the alkaline, anaerobic conditions representative of the near field of the repository, cellulose has previously been shown to degrade to yield soluble products which enhance the solubilities and reduce the sorption of several radionuclides. As part of this investigation, cellulose was chemically degraded under conditions similar to those expected in the near field and the leachate analysed. Separation of the products by HPLC gave direct identification of 2-C-(hydroxymethyl)-3-deoxy-D-erythro-pentonic (isosaccharinic) acid as one of the degradation products. More tentative assignments were made for glycolic, formic, lactic and acetic acids. A comparison was made with the degradation products suggested in the literature. The possible mechanisms and extent of cellulose degradation are discussed, as well as the factors affecting its degradation in the near field. The sorption of plutonium on to cement from a leachate produced under alkaline, anaerobic conditions is reported.

Numerical Modeling of Turbulent Natural Convection in a Concentrating Photovoltaic System

2010 ◽  
Author(s):  
K. M. Nazmul Ahsan ◽  
Robert F. Boehm ◽  
Yitung Chen ◽  
Jianhu Nie
Keyword(s):  
Natural Convection ◽  
Photovoltaic System ◽  
Published Data ◽  
Wall Functions ◽  
Turbulent Natural Convection ◽  
Thermal Buoyancy ◽  
Model Predictions ◽  
The Impact ◽  
Asymmetric Heating ◽  
Good Agreement

A Concentrating Photovoltaic (CPV) system arranged in an asymmetrically heated inclined parallel plate configuration is numerically simulated to investigate the turbulent natural convection inside the system. The flow is induced by the thermal buoyancy force. A low-Reynolds-number k-ε model with modified near wall functions from the Yang-Shih turbulence model has been adapted to numerically solve transport equations for k and ε. The model predictions are validated with available numerical and experimental data given in the literature. The comparison with the published data indicates a good agreement. The calculations are performed for asymmetric heating and assuming the fixed value for CPV cell temperature. The aspect ratio (L/W) and Rayleigh number are kept constant at 36.75 and 2.49×108 respectively. The current study is focused on evaluating the impact of variation of channel inclination and Nusselt number on the thermal profile inside the CPV system.

Interaction of Eu(III) and Th(IV) With Sulfate-Resisting Portland Cement

1997 ◽  
Vol 506 ◽  
Author(s):  
E. Wieland ◽  
J. Tits ◽  
P. Spieler ◽  
J.P. Dobler
Keyword(s):  
Portland Cement ◽  
Pore Water ◽  
Degradation Products ◽  
Cellulose Degradation ◽  
Experimental Methodology ◽  
Batch Type ◽  
Kinetics Of ◽  
Isosaccharinic Acid

ABSTRACTThe uptake of Eu(III) and Th(IV) by a sulphate-resisting Portland cement has been investigated in batch type sorption experiments using 152 Eu and 234Th as tracers. Prior to performing sorption studies, the experimental methodology was assessed. The kinetics of Eu(III) and Th(IV) interactions with cement were measured for times up to about 130 days. The effect of isosaccharinic acid added to artificial cement pore water on Eu(III) and Th(IV) uptake was examined to elucidate the effect of cellulose degradation products.

scholarly journals Influence of Gamma Irradiation on Electric Cables Models: Study of Additive Effects by Mid-Infrared Spectroscopy

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1451
Author(s):  
Astrid Maléchaux ◽  
Juliette Colombani ◽  
Sandrine Amat ◽  
Sylvain R. A. Marque ◽  
Nathalie Dupuy
Keyword(s):  
Gamma Irradiation ◽  
Dose Rate ◽  
Nuclear Power ◽  
Degradation Products ◽  
Principal Component ◽  
High Dose Rate ◽  
Normal Operation ◽  
High Dose ◽  
Electric Cables ◽  
The Impact

Cables, especially their insulation and jacket materials made of polymers, are vulnerable to ageing degradation during normal operation. However, they must remain functional for the entire life of a nuclear power plant, or even in the event of an accident for cables with a safety requirement. This study focuses on models of crosslinked polyethylene (XLPE)-based insulation of cables and deals with the structure modification and the behavior of XLPE for nuclear applications due to the effect of additives. Various additives are added to the polymer formulation to evaluate their impact on ageing. The samples are irradiated at room temperature by several gamma doses, up to 374 kGy, with two dose rates (40 Gy/h and 300 Gy/h) and compared with a non-irradiated sample used as reference. To understand the impact of gamma irradiation on the materials, the principal component analysis (PCA) method is applied on spectra recorded through attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy. The results highlight the effects of ageing depending on the dose rate and on the formulation of the materials, with the identification of different degradation products. A curve resolution study compares the effects of different additives on polymer oxidation and shows that the low dose rate leads to a higher degradation than the high dose rate.

The Effects of the Degradation of Organic Materials in the Near Field of a Radioactive Waste Repository

1991 ◽  
Vol 257 ◽  
Author(s):  
B.F. Greenfield ◽  
A.D. Moreton ◽  
M.W. Spindler ◽  
S.J. Williams ◽  
D.R. Woodwark
Keyword(s):  
Organic Materials ◽  
Degradation Products ◽  
Near Field ◽  
Water Soluble ◽  
Hydroxyl Groups ◽  
Modelling Studies ◽  
Deep Underground ◽  
Exchange Resins ◽  
The Uk ◽  
Isosaccharinic Acid

ABSTRACTUK Nirex Ltd are seeking to develop a deep underground repository for the disposal of solid ILW and LLW in the UK. The formation of water-soluble complexants from the degradation of the solid organic polymers and cellulosic materials present in such wastes may influence the solubility and sorption properties of a number of radioelements. A number of materials have been chemically degraded under alkaline, anaerobic conditions representative of the near field of the repository. Measurements of plutonium solubility in the leachates obtained show that the degradation of cellulose is of particular concern; the effects on the solubility can be several orders of magnitude greater than those of other organic materials. Products formed from the degradation of ion-exchange resins were found to have little effect. Solubilities of a number of other radioelements in aerobically degraded cellulose leachates are also given. The effect of reducing the ratio of celluloseto cement in the degradation experiments results in a decrease in plutonium solubility in the corresponding leachate. Several of the likely degradation products of cellulose have been individually synthesised including isosaccharinic acid, a key degradation product of cellulose. Enhanced plutonium solubilities have been measured in 10-3M solutions of these compounds. Sorption of plutonium onto cement from leachates obtained by the degradation of 10% cellulose in cement is reduced by about two orders of magnitude. Interaction with cement removes significant concentrations of complexants from solution. Thermodynamic modelling studies show that hydroxyl groups present in the compounds which result from the alkaline degradation of cellulose can strongly complex with plutonium.

scholarly journals Source apportionment of circum-Arctic atmospheric black carbon from isotopes and modeling

2019 ◽  
Vol 5 (2) ◽  
pp. eaau8052 ◽  
Author(s):  
P. Winiger ◽  
T. E. Barrett ◽  
R. J. Sheesley ◽  
L. Huang ◽  
S. Sharma ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Climate Warming ◽  
Transport Model ◽  
The Arctic ◽  
Emission Inventories ◽  
Source Contributions ◽  
Model Predictions ◽  
The Impact ◽  
Good Agreement

Black carbon (BC) contributes to Arctic climate warming, yet source attributions are inaccurate due to lacking observational constraints and uncertainties in emission inventories. Year-round, isotope-constrained observations reveal strong seasonal variations in BC sources with a consistent and synchronous pattern at all Arctic sites. These sources were dominated by emissions from fossil fuel combustion in the winter and by biomass burning in the summer. The annual mean source of BC to the circum-Arctic was 39 ± 10% from biomass burning. Comparison of transport-model predictions with the observations showed good agreement for BC concentrations, with larger discrepancies for (fossil/biomass burning) sources. The accuracy of simulated BC concentration, but not of origin, points to misallocations of emissions in the emission inventories. The consistency in seasonal source contributions of BC throughout the Arctic provides strong justification for targeted emission reductions to limit the impact of BC on climate warming in the Arctic and beyond.

scholarly journals Assessment of the impact of a phosphatic fertilizer plant on the adjacent environment using fuzzy logic

2006 ◽  
Vol 4 (1) ◽  
pp. 29-55 ◽  
Author(s):  
K. Szczepaniak ◽  
C. Sârbu ◽  
A. Astel ◽  
E. Raińska ◽  
M. Biziuk ◽  
...  
Keyword(s):  
Element Concentration ◽  
Principal Component ◽  
Soil Samples ◽  
Concentration Gradients ◽  
Fertilizer Plant ◽  
Phosphatic Fertilizer ◽  
Fuzzy Principal Component Analysis ◽  
The Impact ◽  
New Algorithms ◽  
Good Agreement

AbstractThe impact of a phosphatic fertilizer plant on the adjacent environment was examined. Selected rare earth elements, heavy metals and metalloids were determined in substrates and products, waste by-product, and grass and soil samples. Concentration gradients of elements in grass and soil samples along the southerly and easterly directions were examined and compared with the content of interior soil and grass samples, substrates, and products. Results were compared with available data on soil permissible element concentration levels. Two fuzzy principal component analysis (FPCA) methods for robust estimation of principal components were applied and compared with classical PCA. The efficiency of the new algorithms is illustrated. The investigation explored the impact of the plant on the adjacent environment. The most reliable results, in good agreement with types of samples, were produced using the FPCA-O algorithm

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