Actinides solubility

Ekberg, Ch. Uncertainties in Actinide Solubility Calculations Illustrated Using the Th—0H—P04 System, Diss. Chalmers tekniska hogskola, GSteborg, 1999. 

Meaker, T. F Peeler, D. K., Marra, J. C., Pareizs, J. M. Ramsey, W. G. 1997. Actinide solubility in lanthanide borosilicate glass for possible immobilization and disposition. Materials Research Society Symposium Proceedings, 465, 1281-1286. 

Rai, Dhanpat Strickert, R. G. Swanson, J. L., "Actinide Solubilities in the Near-Field of a Nuclear Waste Repository," In Workshop on Near-Field Phenomena in Geologic Repositories, (August 31 - September 3, 1981, Seattle, Washington), Nuclear Energy Agency of OECD, Paris, France, 1981 pp. 13-20. 

Introduction actinide solubilities in reference waters. In this section, the environmental chemistry of the actinides is examined in more detail by considering three different geochemical environments. Compositions of groundwater from these environments are described in Tables 5 and 6. These include (i) low-ionic-strength reducing waters from crystalline rocks at nuclear waste research sites in Sweden (ii) oxic water from the J-13 well at Yucca Mountain, Nevada, the site of a proposed repository for high-level nuclear waste in tuffaceous rocks and (iii) reference brines associated with the WIPP, a repository for TRU in... 

Table 7 contains the results of actinide solubility and speciation calculations for the J-13 and SKI-90 reference waters carried out using the MINTEQ2A code (Allison et al., 1991) as described by Langmuir (1997a). The MINTEQ2A thermodynamic database of Turner et al. (1993) was used with revised data for americium (Silva et al., 1995) and modifications for uranium... 

Table 8 Calculated actinide solubilities in WIPP brines.

Actinide Solubility (M) Solubility-limiting phase Dominant aqueous phases... 

Nitsche H., Muller A., Standifer E. M., Deinhammer R. S., Becraft K., Prussin T., and Gatti R. C. (1992) Dependence of actinide solubility and speciation on carbonate concentration and ionic strength in ground water. Radiochim. Acta 58/59, 27-32. 

Novak C. F. (1997) Calculation of actinide solubilities in WIPP SPC and ERDA-6 brines under MgO backfill scenarios containing either nesquehonite or hydromagnesite as the Mg-COs solubility-limiting phase. Sandia National Labs, WIPP Records Center. 

Since LPAS application to actinide chemistry is in its infancy, only a limited number of works are available in the published literature. Experiments hitherto performed are confined to either hydrolysis, complexation reactions with carbonate, EDTA and humate ligands and a variety of speciation works for Am(III) and to much lesser extent for U(IV), U(VI) Np(IV), Np(V), Np(VI) Pu(IV), Pu(VI). Of considerable interest is the LPAS application to the direct speciation of actinides in natural aquifer systems, where the solubility of actinides is in general very low and multi-component constituent elements as well as compounds are in much higher concentrations than actinide solubilities. The study of the chemical behaviour of actinides in such natural systems requires a selective spectroscopic method of high sensitivity. LPAS is an invaluable method for this purpose but its application to the problem is only just beginning. 

In vitro tests are regarded as an approximation to in vivo tests, but they are much cheaper, quicker and easier to conduct. The strength of in vitro tests is the facility to investigate the effect of factors of interest, for example the composition of the limg fluid simulant, on the actinide solubility whilst maintaining other variables (e.g. particle size) constant. 

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