Separation of Pu and

In 1995, Nevissi and Strebin described a simple fluidic system to deliver sample and reagents to a TRU-Resin column for the separation of Pu and Am.79 A filter was included on-line to capture a precipitate containing the actinides dissolution of the precipitate transferred the sample onto the column downstream. Radionuclides were detected with a-spectrometry off-line. 

Therefore, for the separation of Pu and U by electrolytic reduction in HHO3 solutlons(as being practised in the Purex Process)9 enough hydrazine should be added as the supporting reducing agent. 

Several processes for the separation of Pu and U from irradiated U using tertiary... 

Nigon and Penneman report a separation of Pu and Am, based on extraction of the Pu in the presence of ferrous ammonium sulfate from 1 N HCl solutions. The fact... 

Separation of Pu and Am from nitrate-nitric acid feed was achieved with a SLM in which DHDECMP or n-octylphenyl N,N-diisobutylcarbamoyl methylphosphine oxide (CMPO) as the carriers (7). After transport of the Am into the 0.25 M oxalic acid strippant, it was recovered by sorption on an inorganic ion exchanger. 

The first successflil production method for the separation of Pu from U and its fission products was the bismuth phosphate process, based on the carrying of Pu by a precipitate of BiPO (126). That process has been superseded by Hquid-Hquid extraction (qv) and ion exchange (qv). In the Hquid-Hquid... 

FP) in the aqueous phase. Subsequent separation of U and Pu depends on their differing redox properties (Fig. 31.3). The separations are far from perfect (see p. 1097), and recycling or secondary purification by ion-exchange techniques is required to achieve the necessary overall separations. 

Los Alamos is processing a wide variety of residues, including Pu-Be neutron sources, polystyrene-Pu02-U02 blocks, incinerator ash, Pu-U alloys and oxides, Pu-Zr alloys and oxides, Pu-Np alloys and oxides, Pu-Th alloys and oxides, etc. Processes have been developed for these scrap items (see Figure 2), but we need to know more about Pu-Np separations Pu-Th separations oxalate precipitations for both plus 3 and plus 4 valences valence stabilization dissolution methods for high-fired impure oxides in-line alpha monitors to measure extremely low concentrations of Pu and Am in HNO3 solutions and solubility of various mixtures of Pu02 and UO2 under a variety of conditions. 

The Purex process, ie, plutonium uranium reduction extraction, employs an organic phase consisting of 30 wt % TBP dissolved in a kerosene-type diluent. Purification and separation of U and Pu is achieved because of the extractability of U02+2 and Pu(IV) nitrates by TBP and the relative inextractability of Pu(III) and most fission product nitrates. Plutonium nitrate and U02(N03)2 are extracted into the organic phase by the formation of compounds, eg, Pu(N03)4 -2TBP. The plutonium is reduced to Pu(III) by treatment with ferrous sulfamate, hydrazine, or hydroxylamine and is transferred to the aqueous phase U remains in the organic phase. Further purification is achieved by oxidation of Pu(III) to Pu(IV) and re-extraction with TBP. The plutonium is transferred to an aqueous product. Plutonium recovery from the Purex process is ca 99.9 wt % (128). Decontamination factors are 106 — 10s (97,126,129). A flow sheet of the Purex process is shown in Figure 7. 

As U is the major component of a SNF see Table 1.2, its initial separation in reprocessing alleviates the mass burden of following steps and is considered preferable. The UREX process developed in the AFCI program of the United States is based on the PUREX process (30 vol % TBP in n-dodecane) and suppression of extractions of Pu and Np by reduction/complexation (175-182). Plutonium and Np are reduced by acetohydroxamic acid (AHA, CH3CONHOH) to Pu(III), Np(V), and Np(IV). U is kept in an extractable U(VI) state. Although Np(IV) is also extractable, AHA forms a complex with Np(IV) that is soluble in the aqueous phase. In the case where reoxidation of Pu(III) occurs, the Pu(IV) also transfers to the aqueous phase by forming a Pu(IV)-AHA complex. Thus, U is exclusively extracted. AHA decomposes to hydroxylamine and acetic acid (176). 

Due to the ease of formation of third phase with CMPO, many literature reports are based on the use of the mixture of 0.2 M CMPO + 1.2 M TBP as the solvent (63). This mixture has also been used in the TRUEX process recommended for the partitioning of minor actinides from HLW. Some applications of CMPO for the separation of Pu include its recovery from assorted laboratory wastes and oxalate supernatant (64, 65). 

Pu, Am, and Cm determination in aged nuclear waste using SI system to automate separations of groups and individual actinides Off-line a spectroscopy 48... 

Aldstadt et al. described the determination of U in groundwater using a FI system with a TRU-Resin column coupled on-line to an ICP-MS. The system used three 2-position valves and a flow-reversal scheme to load the sample in one direction and elute in the reverse direction. The system provided an enrichment factor on the order of 30-fold compared to direct groundwater analysis. Separate elution of Pu and Th in a group prior to eluting U was also discussed. 

One of the first experiments in this direction in our laboratories was the development of copolymers containing polyurethanes (PU) and maltose, oligosaccharides, or polysaccharides. The intention was to use the film-forming qualities of PU and its insolubility in water, whereas maltose, or the polysaccharides or oligosaccharides should function as a colon-biodegradable estimated site of separation. Maltose was used as the simplest building block, but it proved too short for an enzymatic attack. It was found that a straight, but not a branched,... 

Separation of Pu From Am and Cm by HDEHP - Plutonium(IV) can be extracted by HDEHP (di-(2-ethylhexyl) phosphoric acid) from nitric acid of medium concentration trivalent TPE and some other impurities are not extracted. 

The dependence of extraction distribution coefficients on the concentration of HDEHP and HN03 and also the influence of impurities such as sodium, aluminum, iron and fluorine have been studied in our laboratory. These experiments show that if the concentration of HDEHP in kerosene is kept between 0.1 and 0.5M and HN03 kept between 2 and 3M the distribution coefficient of Pu(IV) will exceed 103 and the separation factor of Pu and Am will exceed 103. Under these conditions impurities described above do not affect the extraction of Pu(IV). 

Hexamminecobalt(III) salt cannot be used as a precipitant in the oxalato complex precipitation system because it precipitates as hexamminecobalt(III) oxalate. Besides the hexaureachro-mium(III) salt, hexamminechromium(III), tris(ethylenediamine)cobalt (III) or tris(trimethylenediamine)cobalt(III) salts can be used as precipitants. Hexamminechromium(III) and tris(ethylenediamine) cobalt (III) salts form precipitates with actinide(IV) or (VI) oxalato complex ions, whereas tris(trimethylenediamine)co-balt(III) salt forms precipitates with Th(IV) or U(VI) oxalato complex ions leaving Pu(IV) ion in the supernatant solution.Therefore, this reagent plays the role of both a separating agent and a precipitant and is applicable for the separation of Pu(IV) ion from Th(IV) or U(VI) ion. 

Thus, a large excess of U(IV) is required to reduce Pu(IV), diluting the enrichment of the recovered U. Further, the reactions described by Eqs. 7 and 8 will reduce the efficiency of the separation process and may ultimately lead to incomplete separation of U and Pu due to lack of reducing agent, so increasing the cost of the procedure. Alternative methods to reduce Pu include the use of hydroxylamine nitrate with hydrazine as stabiliser or the electroreduction of Pu(III) [66] in situ. Nonetheless, the current use of U(IV) as a reductant for... 

A major topic in isotope mass spectrometry is the determination of the half-lives of long-lived radionuclides. De Bievre and Verbruggen " determined the half-life of " Pu for 3-decay in the isobaric radionuclide " Am on material from Oak Ridge that had initially been about 93% isotopically enriched. Due to the isobaric interference of " Pu and " Am radionuclides during mass spectrometric measurements by TIMS, Am had to be removed by chemical separation immediately (less than 48 h) prior to measurements as described in reference. On the basis of all the measurements performed over an extended period of more than 20 years and after considering the possible effects of systematic errors during these measurements, a half-life for the 3 decay of " Pu of t /2 = 14.290 0.006 a) was reported. " ... 

The result of the separation of U and Pu from the fission products and other actinides is characterized by the decontamination factor, given by the ratio of the activity of the fission products and actinides in the fuel to that in uranium and plutonium after separation. The decontamination factors should be in the order of 10 to 10, and the recoveries of U and Pu should be near to 100%. These requirements are best met by solvent extraction procedures. With respect to the high activity of the fuel, remote control of all operations is necessary. 

Tables 2, 3, and 4 show the overall recoveries of Pu and Am obtained with spiked 100 g samples of Northern Illinois topsoil and two MAPEP reference soils following the separation schemes outlined in Figures 3, 4 and 5. Figures 7 and 8 show the alpha spectra obtained for one of the reference soils. The overall recoveries are in the 50 to 60% range (with one exception). However, if one assumes that at least 25% is lost in the leaching step, then the overall recoveries in the actual separation steps is a respectable 80 to 90%. In the case of the two reference soils, the agreement between the Bq/Kg found for the Pu and...

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