Plutonium distribution ratio

The early field studies revealed that elevated concentrations of fallout plutonium correlated with Increased concentrations of dissolved organic carbon. Experiments at Argonne National Laboratory corroborate this correlation the explanation Is probably that the organic compounds complex Pu(IV), and, hence, decrease the distribution ratio between water and sedlments(27). In these experiments the distribution ratio (Kj) between sediment and natural waters was measured as a function of DOC. Measurements of Kj In both field and laboratory experiments show an unmistakable effect of DOC upon the distribution ratio. Figure 4 shows the Inverse correlation between the K, of plutonium and concentration of DOC. 

Conceptual Flowsheet for the Extraction of Actinides from HLLW. Figure 5 shows a conceptual flowsheet for the extraction of all the actinides (U, Np, Pu, Am, and Cm) from HLLW using 0.4 M 0< >D[IB]CMP0 in DEB. The CMPO compound was selected for this process because of the high D m values attainable with a small concentration of extractant and because of the absence of macro-concentrations of uranyl ion. Distribution ratios relevant to the flowsheet are shown in previous tables, IV, V, VI, and VII and figures 1 and 2. One of the key features of the flowsheet is that plutonium is extracted from the feed solution and stripped from the organic phase without the addition of any nitric acid or use of ferrous sulfamate. However, oxalic acid is added to complex Zr and Mo (see Table IV). The presence of oxalic acid reduces any Np(VI) to Np(IV) (15). The presence of ferrous ion, which is... 

Distribution ratios and transport were carried out on real HAW arising from dissolution of a mixed oxide of uranium and plutonium (MOX) fuel (burnup 34,650 MW d/tU), where uranium and plutonium have been previously extracted by TBP.86 The experiments were performed in the CARMEN hot cell of CEA Fontenay aux Roses with two dialkoxy-calix[4]arene-crown-6 derivatives (diisopropoxy and dini-trophenyl-octyloxy). High cesium distribution ratios were obtained (higher than 50) by contacting the HAW solution with diisopropoxy calix[4]arene-crown-6 (0.1 M in NPHE). Moreover, the high selectivity observed with the simulated waste was confirmed for most of the elements and radionuclides (actinides or fission products Eu, Sb, Ce, Mo, Zr, and Nd). The residual concentration or activity of elements, other than cesium, was less than 1% in the stripping solution, except for iron (2%) and ruthenium (8%) the extraction of these two cations, probably under a complexed... 

These compounds, tested in NPHE at Cadarache, were used as reference compounds for the extraction of actinides by functionalized calixarenes (see below). The distribution ratios for neptunium mainly at the oxidation state (V), plutonium at the oxidation state (IV), and americium (III) are shown in Table 4.21 for OOCMPO. They were also used as references for the americium over europium selectivity (Table 4.22). 

Extraction of neptunium, plutonium, and americium from simulated radioactive liquid waste was carried out in particular with tert-butyl and dealkylated tetramers, hexamers, and octamers of calixarene [ethoxy(diphenylphosphine oxide)]. Among these six calixarenes, the highest distribution ratios were obtained with the dealkylated calix[8]arene. Using a different sample of the dealkylated hexamer, the Strasbourg group concluded that this compound is the most efficient. This discrepancy can be explained by the presence of impurities, detected by NMR, which were probably responsible for the poor performances of the dealkylated hexamer tested at Cadarache. 

The grafting of CMPO moieties on the narrow rim affords a strong decrease of extracting ability toward lanthanides, trivalent actinides, and tetravalent plutonium from acidic solutions. The distribution ratios for the different calixarenes in NPHE are low, except for CPn3 for which the number of carbon atoms in the spacer is four, but even for this compound, the distribution ratios are lower than those obtained with their wide-rim counterparts (Figure 4.11). 

The DBBP extraction scheme provides excellent decontamination of plutonium and americium from all the other metals in the neutralized CAW solution. Kingsley(7) reports that distribution ratios for Fe3+, Al3+, Ca2+, and Mg between 30 vol% DBBP-CCI4 and neutralized CAW are, respectively, 0.11, <0.003, 0.025, and <0.0005. Primarily because of entrainment but partly because of extraction, small amounts of aluminum, iron, and sodium accompany 21tlAm into the dilute HNO3 strip solution. Richardson(9 ) in nonradioactive tests of the countercurrent DBBP 2 1Am recovery process observed decontamination factors in the range 80-180 for iron and in the range 2 x 103 - 1.5 x 105 for aluminum. 

The results of two investigations from two diverse locations provided evidence that this distribution ratio might be due to reversible sorption-desorption reactions. Scientists at Argonne National Laboratory (ANL) equilibrated filtered Lake Michigan water with sediments that had been contaminated with Pu ten years earlier. As many as nine extractions on the same portions of sediment produced essentially identical values(15). Noshkin has observed that the concentrations of plutonium in the waters of Enewetak remain relatively constant although there is a continual replacement of water at an estimated residence time of 144 days (16). The concentration corresponds well with that predicted from the experimental distribution ratio between lagoon sediment and water. 

Figure 5. Plutonium concentration profile and distribution ratio in Contactor III using HAN as reductant (%) aqueous phase (O) solvent phase (X) distribution...

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. 

Figure 10.9 illustrates the effect of uranium saturation of solvent on distribution coefficients, at nitric acid concentrations approximately those in the extracting and scrubbing sections. The ratio of plutonium distribution coefficient to fission products is improved at high uranium loadings, a condition sought at the feed point. 

Distribution ratio experiments with Inorganic cation exchangers were performed by equilibrating 1.0 g of the exchanger with 10 ml of either 0.25M oxalic acid or water In a 14 ml vial on a rotating wheel for up to 72 hours. The aqueous pH was adjusted with 50Z NaOH or 7M HNO. The Initial and final americium and plutonium concentrations were determined radlometrlcally. The volume distribution ratio, D, Is defined as [Am]/g solid r [Am]/ml aqueous phase,and Is calculated from 10 x ([Am]aq - [Amjaq /[Am]aq... 

TaUe 21.20 The distribution ratio D for tetra- and hexavalent plutonium between various organic solvents and an aqueous solution, containing 1 m nitric acid and 10 M ammonium nitrate, if not otherwise stated [176]. 

For the first purification of plutonium in the processing of irradiated nuclear fuels, an anion-exchange process has been widely used [202]. In this process, complex formation of plutonium(iv) with nitrate is utilized in order to remove the last traces of uranium (present as uranyl(vi)) and fission products (primarily lanthanides). In this system, the maximum sorption of plutonium (iv) occurs at a nitric acid concentration of 7.2 m. The process is run at 60°C. At lower temperatures, the sorption is too slow at higher temperatures, the distribution ratio becomes more unfavorable and the resin is more liable to deteriorate. Under the conditions chosen, neither uranyl(vi) nor lanthanides are sorbed. The elution of plutonium(iv) is readily achieved by dilute (0.7 m) nitric acid. The weak point of the process is the limited resistance of organic ion exchangers to chemical attack and to high doses of radiation, already discussed in Section 21.6.1. These difficulties can be overcome, at least partly, by careful selection of the resin to be used. 

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... 

Because of the above uncertainties in estimating actual weights of liquid salt and molten plutonium at equilibrium, it is more practical (although not rigorous) to base the salt-to-metal ratio on the weights of the salt and metal fed to the extraction rather than on the estimated weights of the salt and metal at equilibrium. This puts a low bias on the value of the salt-to-metal ratio and a high bias on the value of the apparent distribution coefficient. 

Research since 1974 has provided information on the uptake of Pu by native and crop plants 30 years after initial contamination of the floodplain soil. The distribution of Pu in native plants and soil has been determined for the 2 hectare (ha) flood-plain, and assimilation of Pu has been determined for forage and vegetable crops planted in a field plot established on the floodplain. A measurable fraction of the Pu was assimilated by plants growing in the contaminated soil (Table V). Plutonium was determined in the foliage of 65% of the tree samples. When detectable, the concentration ratios (CR) (see footnote a,... 

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. 

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