The Solubility of Actinides in the Near-Field

1985 ◽  
Vol 50 ◽  
Author(s):  
F. T. Ewart ◽  
R. M. Howse ◽  
H. P. Thomason ◽  
S. J. Williams ◽  
J. E. Cross
Keyword(s):  
Data Base ◽  
Thermodynamic Data ◽  
Near Field ◽  
Geochemical Modelling ◽  
Actinide Elements

AbstractThe solubility of some of the radiologically important actinide elements have been determined in a water whose chemistry was representative of that believed to exist in potential repositories in the U.K. The solubilities of the actinides have been determined as a function of the pH of the water. The results of these experiments have been compared with the results of predictions made using the PHREEQE geochemical modelling code in order to test and validate the data base used in the model. In the light of these comparisons, suggestions are made for alternative values for the thermodynamic data and for further studies.

Validation of the SKBU1 Uranium Thermodynamic Data Base for its use in Geochemical Calculations with EQ3/6

1988 ◽  
Vol 127 ◽  
Author(s):  
Jordi Bruno ◽  
Ignasi Puigdomenech
Keyword(s):  
Data Base ◽  
Thermodynamic Data ◽  
Carbonate Concentration ◽  
Wide Range

ABSTRACTA validation of the SKBUl uranium thermodynamic data base is performed. Experimental solubilities for schoepite, rutherfordite, UO2(am) and UO2(c) determined in a wide range of pH, PCO2, carbonate concentration and temperature are compared to calculated ones by using EQ3NR.

scholarly journals The Chemkin Thermodynamic Data Base

1990 ◽  
Author(s):  
R. Kee ◽  
F. Rupley ◽  
J. Miller
Keyword(s):  
Data Base ◽  
Thermodynamic Data

scholarly journals Nagra/PSI Chemical Thermodynamic Data Base 01/01

2002 ◽  
Vol 90 (9-11) ◽  
Author(s):  
W. Hummel ◽  
U. Berner ◽  
E. Curti ◽  
F. J. Pearson ◽  
T. Thoenen
Keyword(s):  
Radioactive Waste ◽  
Data Base ◽  
Thermodynamic Data ◽  
Critical Appraisal ◽  
Fission Products ◽  
Performance Assessments ◽  
The Other ◽  
Chemical Thermodynamic ◽  
Carbonate Complexes

SummaryThe Nagra/PSI Chemical Thermodynamic Data Base has been updated to support performance assessments of the planned Swiss repositories for radioactive waste. The update from version 05/92 to 01/01 involved major revisions for most of the actinides and fission products. Altogether, more than 70% of the database contents have been revised. Data for U, Np, Pu, Am and Tc recommended by the NEA TDB project were considered in the update. Thermodynamic data for Th, Sn, Eu, Pd, Al, and solubility and metal complexation of sulphides and silicates were extensively reviewed. Data for Zr, Ni and Se were examined less rigorously as these elements are currently being reviewed in phase II of the NEA TDB project. Our experiences from this two year team effort can be summarised as follows. Detailed in-house reviews and critical appraisal of NEA recommendations greatly improved the chemical consistency and quality of the selected data. On the other hand, we could discern major gaps in the data, especially missing carbonate complexes. In some systems,

Metastable Phase Formation in Multi-Component Aluminium Alloys

2007 ◽  
Vol 263 ◽  
pp. 31-40 ◽  
Author(s):  
Alfred Peter Miodownik ◽  
N. Saunders ◽  
J.P. Schille ◽  
Zhan Li Guo
Keyword(s):  
Data Base ◽  
Phase Formation ◽  
Aluminium Alloys ◽  
Thermodynamic Data ◽  
Metastable Phase ◽  
Equilibrium Conditions ◽  
Metastable Structures ◽  
Metastable Phase Formation ◽  
Commercial Aluminium ◽  
Cct Diagrams

Many Aluminium alloys use the precipitation of metastable phases to generate optimum properties. The effect of including additional structures such as θ’ and GP zones is described in the context of a hierarchy of metastable structures. Extending a Thermodynamic data base that has been designed solely to deal with equilibrium conditions is a vital prerequisite to handling the heattreatment of aluminium alloys. It is then possible to generate TTT and CCT diagrams, using the Johnson-Mehl-Avrami treatment previously applied in to other materials providing provision is made for the presence of supersaturated quenched-in vacancies. Calculations using JMatPro are given for the expected behavior of commercial aluminium alloys of increasing complexity, including AA319, AA6061 and AA7075.

On the Problem of Consistency of Chemical Thermodynamic Data Bases

1990 ◽  
Vol 212 ◽  
Author(s):  
Hans Wanner
Keyword(s):  
Thermodynamic Data ◽  
Radioactive Waste Disposal ◽  
Geochemical Modelling ◽  
Chemical Model ◽  
List Type ◽  
Chemical Thermodynamic ◽  
Data Bases ◽  
Auxiliary Data ◽  
Additional Information

ABSTRACTThe geochemical modelling in support of the performance assessment of radioactive waste disposal systems calls for a large number of chemical thermodynamic data. For realistic modelling it is essential that the data used are fully consistent. The verification of consistency of existing data bases is complicated by the fact that it requires the knowledge of a considerable amount of primary information to ensure:1.Consistency with the fundamental laws of thermodynamics2.Consistency within a chemical model3.Consistency with auxiliary data4.Consistency in the data correction proceduresThis paper includes selected examples for each of the four items to visualize the problems. It should be noted that there are numerous other systems that could serve as examples as well, and the range of cases reported here is far from being exhaustive.Realistic geochemical modelling depends not only on the quality of the data base, but also on the quality of the chemical model used. For the establishment of a chemical model, additional information is needed that is not contained in thermodynamic data bases.

scholarly journals Radionuclide geochemistry: solubility and thermodynamics in an HLW repository

2021 ◽  
Vol 1 ◽  
pp. 149-150
Author(s):  
David Fellhauer ◽  
Xavier Gaona ◽  
Marcus Altmaier ◽  
Horst Geckeis
Keyword(s):  
Nuclear Waste ◽  
Host Rock ◽  
Thermodynamic Data ◽  
Near Field ◽  
Reference Database ◽  
Chemical Information ◽  
Energy Agency ◽  
Complex Formation Constants ◽  
The Impact ◽  
Hlw Repository

Abstract. Deep geological disposal is the internationally favoured option to isolate high-level nuclear waste (HLW) from the biosphere and to minimise the potential radiological risk for future generations. Potentially contacting aqueous solutions such as groundwater may, however, lead to the corrosion of the solid casks containing the nuclear waste, and the formation of aqueous radionuclide systems in the near-field of the emplacement rooms. As dissolved species, radionuclides can in principle further migrate into the far-field and finally reach the biosphere on medium and long timescales. Like all chemical species, the radionuclides are subject to fundamental (geo)chemical laws. Relevant reactions that control retention and release, and hence, the migration behaviour and fate of radionuclides in a repository, are solubility equilibria, formation of soluble complexes, redox reactions, sorption on and incorporation into mineral surfaces, transport phenomena etc. These processes depend directly on the (geo)chemical boundary conditions, and, consequently, can differ greatly for various host rock systems such as clay rock, rock salt, and crystalline rock. Many of the radionuclides in HLW are heavy metals that are sparingly soluble under various repository-relevant conditions, e.g. actinides, lanthanides, transition metals, so that only partial dissolution (mobilisation) from the solid waste matrices is expected. This underlines the importance of evaluating the radionuclide solubility within a geochemically based safety assessment for repositories as it provides reliable upper-limit concentrations of the mobile, potentially migrating radionuclide fraction in the near-field. In this contribution, we discuss relevant aspects related to the topic radionuclide solubility and thermodynamics in a HLW repository. This includes a summary of recent laboratory studies on the solubility behaviour and speciation of key radionuclides in repository-relevant solutions, which are an important basis for obtaining (geo)chemical information and models, and the corresponding fundamental thermodynamic constants on aqueous radionuclide systems. National and international thermodynamic database projects, where quality-assured thermodynamic data (solubility products, complex formation constants, and ion-interaction parameters) are evaluated and compiled, e.g. the Nuclear Energy Agency Thermochemical Database (http://www.oecd-nea.org, last access: 1 November 2021) or the Thermodynamic Reference Database (http://www.thereda.de, last access: 1 November 2021), are highlighted and the main remaining uncertainties discussed. The experimental information and the quantitative thermodynamic data are applied within a generic case study to demonstrate the impact of different geochemical solution conditions representing different host rock systems considered as HLW repositories in Germany on the solubility and speciation of selected radionuclides.

Assessment of the relevance of Coffinite formation within the near-field environment of spent nuclear fuel geological disposals

2006 ◽  
Vol 932 ◽  
Author(s):  
V. Robit-Pointeau ◽  
C. Poinssot ◽  
P. Vitorge ◽  
B. Grambow ◽  
D. Cui ◽  
...  
Keyword(s):  
Nuclear Fuel ◽  
Thermodynamic Data ◽  
Spent Nuclear Fuel ◽  
Near Field ◽  
New Mineral ◽  
Short Term ◽  
Geological Disposal ◽  
Field Environment ◽  
Permanent Presence

ABSTRACTExperiments were performed in anoxic gloves box in an attempt to synthesise Coffinite both in representative near-field conditions, and in conditions which were expected to favour its precipitation according to thermodynamic calculations. The experimental results did not confirm the predictions. However, a new mineral was observed instead of Coffinite. In addition, accurate characterization of various natural samples demonstrate the permanent presence of U(VI) within Coffinite contradictory to its theoretical composition. Our observations raise the question on the validity and applicability of available –actually estimated- thermodynamic data of Coffinite. Based on kinetic hindrance of Coffinite formation, coffinitization of spent nuclear fuel in geological disposal is not anticipated to be a dominant short term process.

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