Plutonium separate elution

Sample preparation is rather involved. A sample of urine or fecal matter is obtained and treated with calcium phosphate to precipitate the plutonium from solution. This mixture is then centrifuged, and the solids that separate are dissolved in 8 M nitric acid and heated to convert the plutonium to the +4 oxidation state. This nitric acid solution is passed through an anion exchange column, and the plutonium is eluted from the column with a hydrochloric-hydroiodic acid solution. The solution is evaporated to dryness, and the sample is redissolved in a sodium sulfate solution and electroplated onto a stainless steel planchette. The alpha particles emitted from this electroplated material are measured by the alpha spectroscopy system, and the quantity of radioactive plutonium ingested is calculated. Approximately 2000 samples per year are prepared for alpha spectroscopy analysis. The work is performed in a clean room environment like that described in Workplace Scene 1.2. 

Plutonium Purification. The same purification approach is used for plutonium separated from sediments or seawater. In case reduction may have occurred, the plutonium is oxidized to the quadrivalent state with either hydrogen peroxide or sodium nitrite and adsorbed on an anion exchange resin from 8M nitric acid as the nitrate complex. Americium, curium, transcurium elements, and lanthanides pass through this column unadsorbed and are collected for subsequent radiochemical purification. Thorium is also adsorbed on this column and is eluted with 12M hydrochloric acid. Plutonium is then eluted from the column with 12M hydrochloric acid containing ammonium iodide to reduce plutonium to the non-adsorbed tervalent state. For seawater samples, adequate cleanup from natural-series isotopes is obtained with this single column step so the plutonium fraction is electroplated on a stainless steel plate and stored for a-spectrometry measurement. Further purification, especially from thorium, is usually needed for sediment samples. Two additional column cycles of this type using fresh resin are usually required to reduce the thorium content of the separated plutonium fraction to insignificant levels. 

Neither Pa(lV) nor Th(lV) le adsorbed from 6m - 12.6m The elution of Fu(lll) by 12H HCl from strong base anion exchange resin has already been mentioned. Wish and Rowell have effected the separation of Th, Pu, Zr, and Np from U by elution with hydrochlorlo acid In a sequence of concentrations. The elements are 2ulsorbed on the resin (Dowex-2) from ISH HCl. Thorium does not adsorb. Plutonium Is eluted In the trlvalent state with 12N HCl saturated with hydroxyl-amine hydrochloride and amnonlum Iodide Zirconium Is eluted with 7.5M HCl neptunium (JV) with a % HCl - 5 NH OH HCl solution. Thranlum Is finally eluted with O.IM HCl. 

Other consideration for selective separation are related to the basic principles of ion exchange. For example, cation displacement should proceed until the column is loaded to capacity with plutonium and americium. If this procedure is not employed, the excess resin simply sorbs the displaced cations (e.g., Mg, Na, K, Ca, etc.) and they are rejoined with the actinides during the elution cycle. 

Exchange resins are also employed for the concentration of ions present in very dilute solutions instances are the recovery of silver from photographic residues, chromate from the waste liquor of chromium plating and magnesium from sea water. They have also been used for the separation of rare earths (p. 426), and of uranium, plutonium and radio-active fission products (p. 437), and for plutonium and uranium-233 purification. A striking application was the historic separation of single atoms of mendelevium on a sulphonated polystyrene resin and their elution therefrom, at 87 , with a-hydroxyisobutyrate (Seaborg, 1955). 

The thorium is removed from the column with 12N HCl, since it does not form a chloride complex, to separate it from neptunium and plutonium. The plutonium is removed by reduction to Pu(III) with 12N HCl-O.lM NH4I solution. The neptunium is then removed by dilute acid. The neptunium and plutonium can also be eluted together with dilute acid and the various nuclides determined by alpha spectrometry. 

For the mutual separation of plutonium and neptunium, both of those are adsorbed on an anion-exchange resin column and the resin converted to chloride form by washing with concentrated hydrochloric acid. Then the plutonium is reduced to the trivalent state and eluted with 9 H hydrochloric acid solution containing 0.1 M hydro-iodic acid. 

Plutonium, uranium, and the other actinide radionuclides can be separated on crown-ether extractant columns (Eichrom columns are discussed in Section 3.5) by selective sorption and elution. A sequential process collects uranium on the first column and the other elements on the second column. Plutonium and other actinides are then eluted with solutions specific for each element. 

Neptunium can easily be separated quantitatively from plutonium with the aid of anion exchangers. If both ions are in a concentrated hydrochloric acid solution, iodide ions are added to reduce plutonium to Pu(III) and neptunium to Np(IV). The solution then passes through a column filled with Dowex-1 anion exchanger. Plutonium is thus quantitatively eluted with concentrated hydrochloric acid, and neptunium can be desorbed with 0.5 mol 1 HCl. 

For the separation of uranium and plutonium in the organic phase, the plutonium is reduced (by Fe(II) sulfamate or other reducing agents) to the oxidation state III and is eluted to a new aqueous phase. Finally, uranium is stripped from the organic phase into a solution of dilute nitric acid. Further purification procedures that cannot be detailed here, follow for all the fractions discussed. Ample information is found in the literature (see, e.g., Choppin and Rydberg 1980 Pickert and Zech 1981). 

The separation of deserves particular attention, when the abundance is high and when a long time has elapsed since the plutonium fuel material was produced. This is the case with samples of high bum-up spent fuel. The standard anion exchange method described in section Isotopic Analysis by Tbermal Ionization Mass Spectrometry, para, (a) is well suited for the purpose, as Pu is eluted long after Am, fission products and U are. It is a good practice, nevertheless, to measure the Am gamma emission at 60 keV in the separated Pu fraction to verify that it will not bias the results. 

Publications on the analysis of soil samples by Smith et al. [78] and Crain et al. [79] summarized two possible routes for the analysis of aqueous samples in chromatography extraction columns, with detection by conventional radiometric techniques such as ICP-MS. In this procedure, TRU-Spec SPS columns were used for group separation of actinides and TEVA-Spec columns were used to isolate the trivalent actinides from the lanthanide elements. A reduced solution (with ascorbic acid) was passed through a 1 mL TRU-Spec column equilibrated with 2 M nitric acid and 0.5 M aluminum nitrate. The trivalent actinides including americium and the lanthanide elements were eluted from the column with 12 mL of 4 M HCl. Plutonium and thorium were removed with 30 mL of... 

O. 1 M tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THFTCA). The trivalent actinides were separated by using TEVA-Spec resin. The lanthanide elements were removed by washing the column with 10 mL of 1 M NH4SCN in 0.1 M formic acid. The trivalent actinides were eluted from the column with 15 mL of 2 M HCl. The THFTCA fraction containing plutonium (239,240py thorium (230,232 1 can be analyzed directly by ICP-MS. 

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