Thermodynamic Modeling of Neptunium(V) Solubility in Concentrated Na-CO3-HCO3-Cl-ClO4-H-OH-H2O Systems

AbstractSafety assessments of nuclear waste repositories often require estimation of actinide solubilities as they vary with groundwater composition. Although a considerable amount of research has been done on the solubility and speciation of actinides,1,2 relatively little has been done to unify these data into a model applicable to concentrated brines. Numerous authors report data on the aqueous chemical properties of Np(V) in NaClO4, Na2CO3, and NaCl media, but a consistent thermodynamic model for predicting these properties is not available. To meet this need, a model was developed to describe the solubility of Np(V) in Na-Cl-ClO4-CO3 aqueous systems, based on the Pitzer activity coefficient formalism for concentrated electrolytes. Hydrolysis and/or carbonate complexation are the dominant aqueous reactions with the neptunyl ion in these systems. Literature data for neptunyl ion extraction and solubility are used to parameterize an integrated model for Np(V) solubility in the Np(V)-Na-CO3-HCO3-Cl-ClO4-H-OH-H2O system. The resulting model is tested against additional solubility and extraction data, and compared with Np(V) solubility experiments in complex synthetic brines.

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Climate Considerations in Long-Term Safety Assessments for Nuclear Waste Repositories

AMBIO ◽

10.1007/s13280-013-0406-6 ◽

2013 ◽

Vol 42 (4) ◽

pp. 393-401 ◽

Cited By ~ 12

Author(s):

Jens-Ove Näslund ◽

Jenny Brandefelt ◽

Lillemor Claesson Liljedahl

Keyword(s):

Nuclear Waste ◽

Safety Assessments ◽

Waste Repositories

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Optimizing the Modeling Performance for Safety Assessments of Nuclear Waste Repositories by Approximating Two-Phase Flow and Transport by Single-Phase Transport Simulations

Nuclear Technology ◽

10.13182/nt13-82 ◽

2014 ◽

Vol 187 (2) ◽

pp. 188-197 ◽

Cited By ~ 1

Author(s):

Philipp Schaedle ◽

Nicolas Hubschwerlen ◽

Holger Class

Keyword(s):

Nuclear Waste ◽

Single Phase ◽

Two Phase Flow ◽

Phase Flow ◽

Two Phase ◽

Flow And Transport ◽

Safety Assessments ◽

Waste Repositories ◽

Phase Transport

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Changes of Selected Structural and Mechanical Properties of the Strzelin Granites As Induced By Thermal Loads / Wpływ Obciążeń Termicznych Na Zmiany Niektórych Strukturalnych I Mechanicznych Właściwości Granitów Strzelińskich

Archives of Mining Sciences ◽

10.2478/v10267-012-0064-8 ◽

2012 ◽

Vol 57 (4) ◽

pp. 951-974 ◽

Cited By ~ 1

Author(s):

Andrzej Nowakowski ◽

Mariusz Młynarczuk

Keyword(s):

Mechanical Properties ◽

Nuclear Waste ◽

Structural Changes ◽

Structural Parameters ◽

Total Porosity ◽

Fracture Network ◽

Qualitative Description ◽

Temperature Changes ◽

Heating And Cooling ◽

Waste Repositories

Abstract Temperature is one of the basic factors influencing physical and structural properties of rocks. A quantitative and qualitative description of this influence becomes essential in underground construction and, in particular, in the construction of various underground storage facilities, including nuclear waste repositories. The present paper discusses the effects of temperature changes on selected mechanical and structural parameters of the Strzelin granites. Its authors focused on analyzing the changes of granite properties that accompany rapid temperature changes, for temperatures lower than 573ºC, which is the value at which the β - α phase transition in quartz occurs. Some of the criteria for selecting the temperature range were the results of measurements carried out at nuclear waste repositories. It was demonstrated that, as a result of the adopted procedure of heating and cooling of samples, the examined rock starts to reveal measurable structural changes, which, in turn, induces vital changes of its selected mechanical properties. In particular, it was shown that one of the quantities describing the structure of the rock - namely, the fracture network - grew significantly. As a consequence, vital changes could be observed in the following physical quantities characterizing the rock: primary wave velocity (vp), permeability coefficient (k), total porosity (n) and fracture porosity (η), limit of compressive strength (Rσ1) and the accompanying deformation (Rε1), Young’s modulus (E), and Poisson’s ratio (ν).

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Experimental study and modeling of uranium (VI) transport through ferrous olivine rock columns

Radiochimica Acta ◽

10.1524/ract.2000.88.9-11.665 ◽

2000 ◽

Vol 88 (9-11) ◽

Cited By ~ 15

Author(s):

M. Rovira ◽

F.Z. El Aamrani ◽

L. Duro ◽

Ignasi Casas ◽

Joan de Pablo ◽

...

Keyword(s):

Nuclear Waste ◽

Reactive Transport ◽

Calculated Data ◽

Buffering Capacity ◽

Retardation Factor ◽

Reactive Transport Modeling ◽

Redox Active ◽

Different Types ◽

Free Media ◽

Waste Repositories

The Lovasjärvi intrusion (SE-Finland) contents a high percentage of ferrous olivine (> 65%). This material has been suggested as a redox-active backfill-additive in deep nuclear waste repositories, due to the large Fe(II) proportion in its mineral composition. In order to understand the processes involved in the redox buffering capacity of this material the transport of uranium (VI) through olivine columns was studied. The results showed considerable retardation factor for the U(VI), particularly in carbonate-free media. The experimental data were simulated by means of reactive transport modeling. The best agreement between the experimental and calculated data was obtained considering that the interaction of U(VI) with the olivine surface occurred at two different types of sorption sites. One type accounts for the sorption capacity of the olivine mineral, and a second type accounts for the sorption on amorphous Fe(OH)

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