Radioelement distribution

Sorption Prediction Equations. Equations predicting radioelement distribution coefficients, K s, as arithmetic functions of component concentrations were obtained for sorption of strontium, neptunium, plutonium, and americium on two Hanford sediments. These equations, presented in Table VH and derived from statistical fits of Box-Behnken experimental designs, were generated for strontium in terms of sodium ion, HEDTA, and EDTA concentrations. Prediction equations for neptunium and plutonium sorption were derived from NaOH, NaA102, HEDTA, and EDTA concentrations. Americium sorption prediction equations were based on NaOH, HEDTA, and EDTA concentrations. 

Nuclear Energy Agency (2001) Using Thermodynamic Sorption Models for Guiding Radioelement Distribution... 

AR263 Using thermodynamic sorption models for guiding radioelement distribution coefficient (Aid) investigations A status report. Radioactive Waste Management, 27 April 2001. 

Dupuis, M., "Distribution and Evolution of Radioelements After a Nuclear Explosion," UCRL-Trans-10617-5, Lawrence Livermore Laboratory, (1972), from Bull. Infor. Sci. Tech., 149, 41 (1970). 

Each sorption experiment was conducted by adding 5.0 mL of the appropriate traced solution, prepared as described above, to a weighed (-1 g) portion of Hanford sediment. To simulate advancement of a radioelement plume from a failed tank through previously waste-wetted sediment, each sediment sample was preequilibrated twice with the relevant untraced solution prior to introduction of the traced solution. Each pre-equilibration lasted at least 2 hr. Following a 7-day equilibration with the traced solution, each sediment-solution mixture was centrifuged, the solution was filtered through an ultrafilter, and the radionuclide solution concentration was determined. Distribution coefficients and fractions of radionuclides sorbed were determined for each sorption experiment. The distribution coefficient, Kd, is the activity per gram of sediment divided by the activity per mL of solution at equilibrium. 

For special geochemical investigations, isotope ratios of other elements, such as B, N, Si, K and Se are also determined. The measurement of the distribution of the natural radioelements U and Th and their daughter nuclides in minerals, sediments, oil, water and the air gives information about the genesis of the minerals, sediments and oils, and about the processes taking place in the lithosphere, the hydrosphere and the atmosphere. The nuclear methods of dating will be discussed in chapter 16. 

Yatsevich and Honda 1997). Their rate of production is therefore related to radioelement and target-element concentrations as well as the distribution of the target element with respect to any radioelement heterogeneity. 

In liquid-liquid extraction, an immiscible liquid—usually an organic solution—is combined with the sample in aqueous solution in an extraction flask and shaken to achieve good contact between the liquids. A reagent that functions as an extractant may have been added to one phase or the other. Information on the distribution ratio D and the extraction yield E that indicate the extent of purification from specified contaminants is available from many studies (Sekine and Hasegaw 1977). The information should describe the extractant, the organic solvent and the conditions of purity, reagent concentrations, volumes, required time, and temperature. The value of D reflects the ratio of the radioelement solubility in the organic phase to that in the aqueous phase, hence the type of solvent and the chemical form of the radionuclide to be extracted may be inferred from radioelement solubility data. If the initial conditions of the extraction procedure are not identical to those for reported extractions, the extent of extraction must be tested. 

The distribution coefficients of the sane radioelements of Figure 33 on Dowex-l resin loaded with EDTA as a function of the EDTA concentration of the eluant Is shown In Figure 34. 

---