Plutonium distribution coefficients for

Estimated Values of Americium and Plutonium Distribution Coefficients for NaCl-KCl-MgCl2 Salt and Plutonium Metal System at 750°C... 

Procedures. Procedures were developed for measuring plutonium distribution coefficients for batch equilibrium adsorption measurements and for measuring plutonium breakthrough concentrations for column flow-through adsorption experiments. 

Plutonium distribution coefficients for each adsorbent at four pH levels and two plutonium concentration levels were calculated as follows ... 

Figure 1. Plutonium Distribution Coefficients For Alumina Adsorbents as a Function of pH.

Burger and coworkers (5) in 1952 reported that some distribution coefficients for Pu022+ in organic-aqueous systems at lighted conditions were different from those observed for dark conditions, and those authors believed that some Pu022+ had been photochemically reduced. That reduction was confirmed by others (6) in 1965, and in 1969 a report suggested that most aqueous plutonium reactions were affected by light (7 ). 

The effect of irradiation on the extractability of sulfoxides towards plutonium, uranium and some fission products were studied by Subramanian and coworkers . They studied mainly the effect of irradiation on dihexyl sulfoxide (DHSO) and found that irradiation did not change the distribution coefficient for Ru, Eu and Ce but increases the distribution coefficient for Zr and Pu. When comparing DHSO and tributyl phosphate (TBP), the usual solvent for the recovery and purification of plutonium and uranium from spent nuclear fuels, the effect of irradiation to deteriorate the extraction capability is much larger in TBP. Lan and coworkers studied diphenyl sulfoxides as protectors for the gamma radiolysis of TBP. It was found that diphenyl sulfoxide can accept energy from two different kinds of excited TBP and thus inhibits the decomposition of the latter. 

The distribution coefficients for americium and plutonium are estimated by using the appropriate constants in Equation 9 as shown in Equations 10 and 11. 

From equations 10 and 11, values of the americium and plutonium distribution coefficient can be estimated for MgCl2 contents in the salt ranging from 0.02 to 1.0 mole fraction (Table II). 

The pH range achieved was very narrow (6.5 to 7.5) because Bioclaim-MRA was a strong buffer. Distribution coefficients for plutonium adsorption on Remsorb-CP were somewhat lower and decreased dramatically as the pH increased to 9 as might be expected for a cation exchanger. There was no significant difference in Kd values for the two... 

Bone char appears to be the most effective adsorbent for removal of plutonium from the wastewaters because of high distribution coefficients for plutonium adsorption and rapid adsorption. The capacity of bone char for plutonium absorption can be calculated from a measured Kd value, assuming a reversible equilibrium adsorption reaction and a linear adsorption isotherm. If the capacity is defined as the point where the plutonium concentrations in the column feed and effluent are equal, the maximum volume of wastewater that can be treated (V ax) is (14)... 

Consider the plutonium-recovery extraction process shown in Figure 5.32. Determine the additional number of stages required for each ten-fold reduction in plutonium concentration, C, in stream 1 (for conditions of high plutonium recovery, i.e., C(l) < C(N + 1)). The plutonium distribution coefficient, Tfpu, is 5 (ratio of concentration in organic phase to concentration in aqueous phase). V denotes the relative volumetric flowrate. 

H2. Homer, D. E. A Mathematical Model and a Computer Program for Estimating Distribution Coefficients for Plutonium, Uranium and Nitric Acid with Tri-n-Butyl Phosphate, Report ORNL-TM-2711, Feb., 1971. 

More quantitative data on distribution coefficients for uranium, plutonium, and HNO3 are given in Sec. 4.15. 

Distribution coefficients for Pu(IV) may be obtained from Fig. 10.17. This plots the ratio of distribution coefficients of tetravalent plutonium to hexavalent uranium. 

These variations permit the separation of other components, if desired. Additional data on uranium, plutonium, and nitric acid distribution coefficients as a function of TBP concentration, solvent saturation, and salting strength are available (24,25). Algorithms have also been developed for the prediction of fission product distributions in the PUREX process (23). 

In Figure 1 dashed squares refer to water bodies, while solid squares refer to solid matter (also containing some water). Plutonium may appear in any of these squares. The ratio of the concentration of plutonium in two adjacent squares is usually referred to as the concentration factor (CF usually from the water to the solid substance), the transfer coefficient (TC usually between two biological species), or the sorption ratio (or between minerals and water). To avoid ambiguity, we shall use the expression distribution coefficient (abbreviated Kd) with unit dimension (Pu amount per kg product divided by Pu amount per kg source). For the transfer of plutonium from A to B, Pu(A) ->- Pu(B), we define... 

Table I summarizes some typical distribution coefficients. Sediments become enriched in plutonium with respect to water, usually with a factor of vlO5. Also living organisms enrich plutonium from natural waters, but usually less than sediments a factor of 103 - 101 is common. This indicates that the Kd-value for sediment (and soil) is probably governed by surface sorption phenomena. From the simplest organisms (plankton and plants) to man there is clear evidence of metabolic discrimination against transfer of plutonium. In general, the higher the species is on the trophic level, the smaller is the Kd-value. One may deduce from the Table that the concentration of plutonium accumulated in man in equilibrium with the environment, will not exceed the concentration of plutonium in the ground water, independent of the mode of ingestion.

Table I. Distribution Coefficients, K, For Plutonium in Different Natural Waters(10)...

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. 

Uranium(VI) and plutonium(IV) are separated from each other and from fission products by TBP, although phosphonates have better distribution coefficients than phosphates for Th and Carbamoylmethylphosphoryl (CMP) extractants are... 

Uranium transfers at a slower rate than plutonium because uranium has a lower solubility than plutonium in the donor alloy and uranium has a lower distribution coefficient that plutonium in the donor alloy-salt system. This difference in the rate of transfer is very desirable because it provides a means for enriching the plutonium content of the product to required concentrations for recycle to the reactor core. This enrichment is obtained by terminating the circulation of the transport salt between donor and acceptor alloys before complete uranium transfer has occurred. As uranium transfers, the solid UCU5 compound dissolves into the donor alloy. After plutonium and the desired amount of uranium are separated from FP-4 elements, the remaining uranium may be separated by diverting the transport salt to a second zinc-magnesium acceptor alloy. 

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