Plutonium sulfate

Simulated storage experiments showed (Figure 2) that radiolysis would be inadequate for valence adjustment of Pu(IIl) to Pu(lV) within the available time frame. It was also necessary to assure that plutonium sulfates would not precipitate during storage. The solubility of plutonium vs. nitric acid concentration at various concentrations of sulfate is shown in Figure 3. Because the plutonium concentration in canyon tanks is kept at <6 g Pu/L, nitric acid concentrations as high as 6M can be tolerated as the sulfate ion concentration is diluted to <0.4M. while diluting the Pu. 

Plutonium behavior under dynamic conditions was studied by injecting dissolved plutonium sulfate and preformed Pu02 into a circulating stream of 12 liters of Am UO2SO4 at 250°C under 350 psi oxygen. This solution was contained in a type-347 stainless steel loop equipped with a canned rotor pump, a hydroclone, metal adsorption coupon holders, and a small... 

Historically, ferrous sulfamate, Fe(NH2S02)2, was added to the HNO scmbbing solution in sufficient excess to ensure the destmction of nitrite ions and the resulting reduction of the Pu to the less extractable Pu . However, the sulfate ion is undesirable because sulfate complexes with the plutonium to compHcate the subsequent plutonium purification step, adds to corrosion problems, and as SO2 is an off-gas pollutant during any subsequent high temperature waste solidification operations. The associated ferric ion contributes significantly to the solidified waste volume. 

Several components are required in the practical appHcation of nuclear reactors (1 5). The first and most vital component of a nuclear reactor is the fuel, which is usually uranium slightly enriched in uranium-235 [15117-96-1] to approximately 3%, in contrast to natural uranium which has 0.72% Less commonly, reactors are fueled with plutonium produced by neutron absorption in uranium-238 [24678-82-8]. Even more rare are reactors fueled with uranium-233 [13968-55-3] produced by neutron absorption in thorium-232 (see Nuclear reactors, nuclear fuel reserves). The chemical form of the reactor fuel typically is uranium dioxide, UO2, but uranium metal and other compounds have been used, including sulfates, siUcides, nitrates, carbides, and molten salts. 

Pu(N03 ) -5H2 0 deep red plutonyl nitrate hexahydrate [19125-90-7], Pu02(N03 )2-6H2 0 coral red anhydrous plutonium(IV) sulfate [13692-89-2], Pu(S0 2i pinh or redPu(S0 2 4H20 and moss green plutonyl carbonate/ P2P2-/(9-P/, PUO2CO2 (30). 

Comparison of these results for plutonium with those for other tetravalent metals reveals some interesting facts. Thor-ium(IV), uranium(IV) and neptunium(IV) sulfates have been investigated under hydrothermal hydrolytic conditions. For uranium, the stable phases which have been reported include U(0H)2S0i (2), U60i, (OH)i, (SO.,) 6 (2). U (SOi,) 2 4H20 (23) and IKSO (24). 

Although the phase which appears to be very stable for plutonium has not been observed in other An02 S03 H20 systems, phases of identical composition have been observed for Zr, Hf and Ce. The crystal structure of the zirconium compound Zr2(0H)2-(SOO 3 (H20) i,, is well known 05). One very interesting feature of the M02 S03 H20 systems for Zr, Hf and Co is that there are a large number of phases which have been observed. Some of these correspond to phases which are known for Th, U and Np. For zirconium, a series of basic sulfates is known to include Zr2(0H)2-(SOi,) 3 (H20)i, and two modifications of Zr(0H)2S0i, as the major constituents (5). Other basic sulfates such as Zr(OH)2S0if,H20,... 

The conditions under which the basic sulfates of tetraval-ent, Zr, Hf and Ce form provide analogies on which to base speculation about the hydrothermal hydrolysis of tetravalent plutonium. In the zirconium system at 100°C, the only basic sulfate observed is Zr2 (0H)2 (SOO3 ( 0), i.e., the zirconium analog of... 

Stability Constants, Enthalpies, and Entropies of Plutonium(III) and Plutonium(IV) Sulfate Complexes... 

The physical nature of the sulfate complexes formed by plutonium(III) and plutonium(IV) in 1 M acid 2 M ionic strength perchlorate media has been inferred from thermodynamic parameters for complexation reactions and acid dependence of stability constants. The stability constants of 1 1 and 1 2 complexes were determined by solvent extraction and ion-exchange techniques, and the thermodynamic parameters calculated from the temperature dependence of the stability constants. The data are consistent with the formation of complexes of the form PuSOi,(n-2)+ for the 1 1 complexes of both plutonium(III) and plutonium(IV). The second HSO4 ligand appears to be added without deprotonation in both systems to form complexes of the form PuSOifHSOit(n"3) +. ... 

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. 

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