scholarly journals Determination of the Forward Dissolution Rate for International Simple Glass in Alkaline Solutions

MRS Advances ◽  
2017 ◽  
Vol 2 (12) ◽  
pp. 661-667 ◽  
Author(s):  
Alice Elia ◽  
Karine Ferrand ◽  
Karel Lemmens
Keyword(s):  
Dissolution Rate ◽  
Nuclear Waste ◽  
International Collaboration ◽  
Alkaline Solutions ◽  
Alkaline Ph ◽  
Geological Disposal ◽  
Ph Range ◽  
High Level ◽  
Good Agreement

ABSTRACTThe International Simple Glass (ISG) is considered as reference benchmark glass and is used in the frame of an international collaboration for the study of the dissolution mechanisms of high-level vitrified nuclear waste.In this work the forward dissolution rate of the ISG was determined in different alkaline solutions, as a simulation of the disposal conditions foreseen by the Belgian concept for geological disposal of vitrified waste. The determination of the forward dissolution rate was done by measuring the Si released from the glass in solution in tests performed at 30 °C in four different KOH solutions with pH varying from 9 to 14 and in artificial cementitious water at pH 13.5.The forward dissolution rates determined for the ISG in high pH solutions are in good agreement with the results obtained for a lower pH range.The rates obtained in this study, moreover, were compared with the rates measured in the same conditions for SON68 glass from a previous work. The values obtained for the two glasses are comparable in artificial cementitious water and in KOH at moderately alkaline pH. At higher pH, ISG glass shows a lower forward dissolution rate with respect to SON68 (0.20 g·m-2·d for ISG and 0.35 g·m-2 d for SON68 at pH 14).

Experimental Investigation on the Active Range of Sulfate-Reducing Bacteria for Geological Disposal

1994 ◽  
Vol 353 ◽  
Author(s):  
S. Fukunaga ◽  
H. Yoshikawa ◽  
K. Fujiki ◽  
H. Asano
Keyword(s):  
Experimental Investigation ◽  
Environmental Conditions ◽  
Desulfovibrio Desulfuricans ◽  
Sulfate Reducing Bacteria ◽  
Geological Disposal ◽  
Sulfate Reducing ◽  
Buffer Material ◽  
Ph Range ◽  
High Level ◽  
Reducing Bacteria

AbstractThe active range ofDesulfovibrio desulfuricans. a species of sulfate-reducing bacteria, was examined in terms of pH and Eh using a fermenter at controlled pH and Eh. Such research is important because sulfate-reducing bacteria (SRB) are thought to exist underground at depths equal to those of supposed repositories for high-level radioactive wastes and to be capable of inducing corrosion of the metals used in containment vessels.SRB activity was estimated at 35°C, with lactate as an electron donor, at a pH range from 7 to 11 and Eh range from 0 to -380 mV. Activity increased as pH approached neutral and Eh declined. The upper pH limit for activity was between 9.9 and 10.3, at Eh of -360 to -384 mV. The upper Eh limit for activity was between -68 and -3 mV, at pH 7.1. These results show that SRB can be made active at higher pH by decreasing Eh, and that the higher pH levels of 8 to 10 produced by use of the buffer material bentonite does not suppress SRB completely.A chart was obtained showing the active range ofDesulfovibrio desulfuricansin terms of pH and Eh. Such charts can be used to estimate the viability of SRB and other microorganisms when the environmental conditions of a repository are specified.

scholarly journals A Critical Review of the Recent Improvements in Minimizing Nuclear Waste by Innovative Gas-Cooled Reactors

2008 ◽  
Vol 2008 ◽  
pp. 1-18 ◽  
Author(s):  
E. Bomboni ◽  
N. Cerullo ◽  
G. Lomonaco ◽  
V. Romanello
Keyword(s):  
Nuclear Waste ◽  
Critical Review ◽  
Simplified Models ◽  
Geological Disposal ◽  
Fuel Cycles ◽  
Multiple Recycling ◽  
High Level ◽  
Coupling Current ◽  
The University

This paper presents a critical review of the recent improvements in minimizing nuclear waste in terms of quantities, long-term activities, and radiotoxicities by innovative GCRs, with particular emphasis to the results obtained at the University of Pisa. Regarding these last items, in the frame of some EU projects (GCFR, PUMA, and RAPHAEL), we analyzed symbiotic fuel cycles coupling current LWRs with HTRs, finally closing the cycle by GCFRs. Particularly, we analyzed fertile-free and Pu-Th-based fuel in HTR: we improved plutonium exploitation also by optimizing Pu/Th ratios in the fuel loaded in an HTR. Then, we chose GCFRs to burn residual MA. We have started the calculations on simplified models, but we ended them using more “realistic” models of the reactors. In addition, we have added the GCFR multiple recycling option usingkeffcalculations for all the reactors. As a conclusion, we can state that, coupling HTR with GCFR, the geological disposal issues concerning high-level radiotoxicity of MA can be considerably reduced.

scholarly journals DEVELOPMENT OF ANODIC STRIPPING VOLTAMMETRY FOR THE DETERMINATION OF PALLADIUM IN HIGH LEVEL NUCLEAR WASTE

2012 ◽  
Vol 44 (8) ◽  
pp. 939-944 ◽  
Author(s):  
T.K. Bhardwaj ◽  
H.S. Sharma ◽  
P.C. Jain ◽  
S.K. Aggarwal
Keyword(s):  
Nuclear Waste ◽  
Anodic Stripping Voltammetry ◽  
Stripping Voltammetry ◽  
Anodic Stripping ◽  
High Level Nuclear Waste ◽  
High Level

Creep of the copper canister in the Swedish program

2006 ◽  
Vol 932 ◽  
Author(s):  
William H Bowyer
Keyword(s):  
Nuclear Waste ◽  
Strengthening Mechanism ◽  
Test Results ◽  
Short Life ◽  
Iron Load ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Life Predictions ◽  
Good Agreement

ABSTRACTThe Swedish programme for disposal of high level nuclear waste includes the development of a container which comprises a cast iron load bearing canister contained in a 50 mm thick copper corrosionshield.The temperature of the outside of the canister is likely be up to 100°C, and repository processes may lead to long term loads of up to 50MPa. Creep of the copper is therefore an issue. SKB (The Swedish Nuclear Fuel and Waste Management Co.) have been conducted tests on three materials, OF copper containing 10ppm sulphur (OF1), OF copper containing 6ppm sulphur (OF2) and OF copper containing 6ppm sulphur and 50ppm phosphorus (OFP). In order to improve confidence in extrapolation of test results to practical temperatures and stresses, it is desirable to support the extrapolation procedures with a physical model.Life predictions made using the Frost and Ashby model [5] together with a simplification of the Cocksand Ashby model [6] provide good agreement with published experimental data for OF2 and OFPmaterials. Extrapolation of this data using the model leads to life predictions of 12,000 years for the OF2material and 120,000 years for OFP material. The prediction for OFP depends on an assumption that an observed strengthening mechanism conferred by phosphorus at high stresses and temperatures, is equally as effective under repository conditions.OF1 material fails after a relatively short life and by a different mechanism to OF2 and OFP. The changein mechanism may be explained, using the model [6], for cases where segregating species reduce surface energy of grain boundary voids. It is suggested that in this case the segregating species is sulphur.

Determination of the Forward Rate of Dissolution for SON68 and PAMELA Glasses in Contact With Alkaline Solutions

2008 ◽  
Vol 1107 ◽  
Author(s):  
K. Ferrand ◽  
K. Lemmens
Keyword(s):  
Waste Glass ◽  
Forward Rate ◽  
Alkaline Solutions ◽  
Dynamic Tests ◽  
Forward Rates ◽  
Rate Of Dissolution ◽  
Uv Visible ◽  
Radionuclide Release ◽  
Good Agreement

AbstractIn the new Belgian disposal design, the nuclear waste glass will be surrounded by a 3 cm thick carbon steel overpack and a 70 cm thick concrete buffer. An initially high pH is expected after water intrusion in the concrete buffer and this may have an effect on the radionuclide release from the waste glass. This study was performed in order to determine the forward rate of dissolution for SON68 and PAMELA glasses (SM513 LW11 and SM539 HE 540-12), conducting dynamic tests at 30°C in contact with alkaline solutions. In these experiments, the silicon concentration in solution was determined by UV/Visible spectrophotometry according to the blue â-silicomolybdenum method. The forward rates of dissolution were quite similar for the three glasses except at the highest pH for which a slightly higher value was found for SM539 glass. For SON68 glass, a good agreement with the previously established interpolation law was observed until pH 11.5, but at higher pH, the interpolation law slightly overestimates the dissolution rate [1].

scholarly journals Comparison of different methods of determining β-lactam susceptibility in clinical strains of Pseudomonas aeruginosa

2009 ◽  
Vol 58 (5) ◽  
pp. 625-629 ◽  
Author(s):  
Eva Torres ◽  
Rosa Villanueva ◽  
Germán Bou
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Reference Method ◽  
Test System ◽  
Testing Susceptibility ◽  
Vitek 2 ◽  
High Level ◽  
Resistance Rates ◽  
Susceptibility And Resistance ◽  
Good Agreement

One hundred and one randomly selected (2003–2005) clinical isolates of Pseudomonas aeruginosa were used to assess the quantitative (MIC) and qualitative (susceptibility category) agreement between the microdilution broth reference method (RM) and disc diffusion (DD), Etest and the VITEK 2 automated susceptibility test system for determination of the susceptibility of P. aeruginosa to piperacillin (PIP), PIP–tazobactam (TZP), ceftazidime (CAZ), aztreonam (ATM) cefepime (FEP) and imipenem (IMP). The results obtained by the RM were compared with those obtained by the other methods. The RM and DD were performed according to CLSI criteria. Etest and VITEK 2 were according to the manufacturer's instructions. The Advanced Expert System (AES), which interprets MICs generated by VITEK 2, was modified with new rules of interpretation. Overall, VITEK 2 showed the lowest MIC90 values for the six antibiotics. The RM categorical testing (susceptibility and resistance) rates with P. aeruginosa were 11.8 and 88.1 for PIP, 22.7 and 77.2 for TZP, 14.8 and 78.2 for CAZ, 12.8 and 54.4 for ATM, 16.8 and 75.3 for FEP, and 7.9 and 90.1 for IMP, respectively. Very major errors (false susceptible) were only detected for ATM and FEP with DD and for IMP with three methods. Major errors (false resistant) were generally acceptable for all antibiotics except TZP. VITEK 2 yielded a high level of minor errors (trends toward false susceptibility), mainly with CAZ and FEP. A good agreement was obtained for all antibiotics/methods assayed, thus highlighting the importance of the AES for categorization of β-lactam susceptibility in P. aeruginosa.

Characterization of Chromium(III) Hydroxide Solids and Their Oxidation by Hydrogen Peroxide

2004 ◽  
Vol 824 ◽  
Author(s):  
Zhicheng Zhang ◽  
Linfeng Rao ◽  
Dhanpat Rai ◽  
Sue B. Clark
Keyword(s):  
Hydrogen Peroxide ◽  
Nuclear Waste ◽  
Molten Glass ◽  
Alkaline Solutions ◽  
Uv Absorption Spectroscopy ◽  
Oxidative Leaching ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Oxidation By Hydrogen Peroxide

AbstractChromium is of great concern in the vitrification of high-level nuclear waste sludges because it forms separate crystallites in the molten glass. Inadequate removal of chromium from sludges could result in the production of an unacceptably large volume of HLW glass. Alkaline oxidative leaching is considered one of the pretreatment strategies to remove chromium before the vitrification.In this study, Cr(III) hydroxide solids were prepared under different conditions and characterized by EXAFS and IR. The rate of oxidation of the solids by hydrogen peroxide in alkaline solutions was studied by UV absorption spectroscopy. EXAFS and IR experiments indicate that the degree of oligomerization in the Cr(III) hydroxide solids increases with the increase in the concentration of NaOH in solution, the aging temperature and the aging time. The rate of oxidation of the solids follows the same order previously observed for Cr(III) oligomers in solution, i.e., species with higher degree of oligomerization are oxidized more slowly.

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