I. Introduction. Background. Focus of the review. Review procedure and results. The NEA-TDB data base system. Presentation of the selected data. II. Standards and Conventions. Symbols, terminology and nomenclature. Units and conversion factors. Standard and reference conditions. Fundamental physical constants. III. Selected Uranium Data. IV. Selected Auxiliary Data. V. Discussion of Data Selection. Elemental uranium. Aqua ions. Oxide, hydride and hydroxide species. VI. Discussion of Auxiliary Data Selection. Reference list. Authors list. Formula list. Discussion of selected references. Ionic strength corrections. Assigned uncertainties. The estimation of entropies.

Chemical thermodynamics of uranium

The separation of trivalent transplutonium actinides from fission product lanthanide ions represents arguably the most challenging aspect of advanced nuclear fuel partitioning schemes. A considerable amount of effort has been dedicated to the development of effective methods for accomplishing this separation, essential for transmutation of the actinides heavier than Pu. Among the methods currently considered to be ready for technological deployment is the TALSPEAK (Trivalent Actinide ‐ Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexes) Process, developed in the late 1960s at Oak Ridge National Laboratory. This process is based on the partitioning of lanthanides and actinides between an acidic organophosphorus extractant ((RO)2PO2H) solution and an aqueous phase containing a high concentration of a carboxylic acid buffer and a polyaminopolycarboxylate complexant. The latter reagent is principally responsible for holding back the trivalent actinides, allowing the selecti...

Review Article: A Review of the Development and Operational Characteristics of the TALSPEAK Process

The Phase Stability of Cerium Species in Aqueous Systems : I. E-pH Diagram for the System

Equilibria and thermodynamic data for cerium dimer species were calculated for both the Ce-H 2 O-O 2 and Ce-H 2 O-H 2 O 2 systems. It was found that Ce(IV) has a tendency to form dimers, especially when the total cerium concentration is higher than 0.001 M. There are three major soluble dimer forms considered in this paper: (CeOCe) 6 + , (CeOCe)(OH) 5 + , and (CeOCe)(OH) 4 + 2 , all having very similar standard potentials (E 0 C e ( I V ) d i m e r / C e ( I I I ) .1.66 V 0.02 V). When they coexist in solution, the concentration ratio of the Ce(IV) dimer to Ce 3 + depends on the total cerium concentrations, the oxidizing agent, and in some cases the pH. Increasing the value of each individual factor favors the formation of dimers. It was also found that the direct oxidation of Ce 3 + to dimers (CeOCe)(OH) ( 6 - x ) + x by O 2 appeared to be insignificant, but the oxidation of Ce 3 + to the three dimers by H 2 O 2 would be much more favorable.

The phase stability of cerium species in aqueous systems. III. The Ce(III/IV)-H2O-H2O2/O2 systems dimeric Ce(IV) species

Recent concerns on the radiotoxicity and longevity of nuclides have prompted the development of new technologies for their removal from wastes produced from nuclear power programs and nuclear fuel reprocessing activities. Alongside developments from traditional chemical treatment processes, interest has also centered on the application of biotechnology for efficient waste treatment. Many biological techniques have relied on empirical approaches in simple model systems, with scant regard to the nature and volume of actual target wastes; such considerations may limit the application of the new technologies in practice. This review aims to identify some of the likely problems, to discuss the various approaches under current consideration, and to evaluate ways in which either the target waste or the detoxifying biomass may be modified or presented for the most efficient treatment.

The application of biotechnology to the treatment of wastes produced from the nuclear fuel cycle: biodegradation and bioaccumulation as a means of treating radionuclide-containing streams.

Expected species of uranium, neptunium and plutonium in neutral aqueous solutions

Distribution ratios and empirical equations for the extraction of elements in Purex high level waste solution—II: HDEHP

Investigation of complex formation between neptunium(IV) and acetylacetone by solvent extraction

Experience from Cold Tests of the CTH Actinide Separation Process

Spent nuclear fuel can either be incapsulated and stored permanently in a deep underground repository or reprocessed to recover valuable U and Pu. The high level liquid waste (HLLW) solution resulting from PUREX reprocessing contains the fission products, small fractions of the U and Pu, and most of the Np, Am and higher actinides originally present in the spent fuel. The α-activity in the HLLW amounts to more than 99% of all such activity in wastes from the nuclear fuel cycle (1). This solution can be vitrified and stored as high active glass in deep underground repositories in a similar way as the unprocessed fuel. The Swedish KBS study (2, 3) shows that such repositories can be placed in granite bedrock at 500 m depth. Careful analysis of the possible releases from a repository of this kind shows that U and Np isotopes, with daughters, are responsible for the main radiation doses generated by the repository (2, 4). Because of the enormous time scale, a remedy seems to be a reduction of actinide content by about a factor 100 before solidification of the waste. In anticipation that a separation process might eventually be required or at least had to be considered as an option, we began development work on an actinide separation process in 1974. The general philosophy and a broad outline of our flowsheet was presented in 1976 at the Symposium on Waste Management in Tucson (5).

J.O. Liljenzin

Papers

Expected species of uranium, neptunium and plutonium in neutral aqueous solutions

Distribution ratios and empirical equations for the extraction of elements in Purex high level waste solution—II: HDEHP

Investigation of complex formation between neptunium(IV) and acetylacetone by solvent extraction

Experience from Cold Tests of the CTH Actinide Separation Process

Actinide Separation from HLLW