Plutonyl carbonates

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). 

These mixed oxides can also be manufactured by mixing the uranium and nitrate solutions produeed during the reprocessing of spent nuclear fuels and converting these metal nitrate mixtures into a mixed oxide (coprecipitation). In this process the plutonium is first reoxidized, then gaseous ammonia and carbon dioxide are introduced into the aqueous nitrate mixture, whereupon ammonium uranyl-plutonyl carbonate is precipitated. This can be calcined to... 

U233 and 9433 may be dispersed in water as soluble 6 uranyl and plutonyl (PuOa ) salts, such as uranyl and plutonyl nitrate, sulphate or fluoride, or as an alkali metal uranyl or plutonyl carbonate. Such a solution with the proper isotope concentration in water of either type and in a container of the proper size will sustain a 10 chain reaction with a low neutron loss except for exterior neutron leakage, which will be very high. 

In the literature (2), the possible formation of plutonyl bicarbonate complex is discussed. In order to verify whether we are dealing with bicarbonate or carbonate complexes, the Pu(IV) solutions prepared in NaHC03 and Na2C03 solutions are examined by spectrophotometry. The absorption spectra measured up to 900 nm show no visible difference for both solutions. For this reason it is believed that the Pu(IV) ion forms carbonate complexes irrespective of carbonate or bicarbonate ions present in solution. 

In contrast, the solubilities of the neptunyl species were increased by HEDTA and unexpectedly decreased by EDTA. Plutonyl(V) solubility was not affected by HEDTA or EDTA. The component most significant to neptunium solubility was NaNOz. Sodium nitrite apparently decreased neptunium solubility by reducing the more soluble neptunyl(VI) to the less soluble (V) state. The existence of two oxidation states complicated interpretation of the neptunium data. Sodium carbonate, phosphate, aluminate, and sulfate all increased neptunium solubility, probably through complexation. Separation of the data... 

Carbonate Complexes. Of the many ligands which are known to complex plutonium, only those of primary environmental concern, that is, carbonate, sulfate, fluoride, chloride, nitrate, phosphate, citrate, tributyl phosphate (TBP), and ethylenediaminetet-raacetic acid (EDTA), will be discussed. Of these, none is more important in natural systems than carbonate, but data on its reactions with plutonium are meager, primarily because of competitive hydrolysis at the low acidities that must be used. No stability constants have been published on the carbonate complexes of plutonium(III) and plutonyl(V), and the data for the plutoni-um(IV) species are not credible. Results from studies on the solubility of plutonium(IV) oxalate in K2CO3 solutions of various concentrations have been interpreted to indicate the existence of complexes as high as Pu(C03) , a species that is most unlikely from both electrostatic and steric considerations. From the influence of K2CO3 concentration on the solubility of PuCOH) at an ionic strength of 10 M, the stability constant of the complex Pu(C03) was calculated (10) to be 9.1 X 10 at 20°. This value... 

Several areas of research seem to merit top priority attempt to verify published stability constants of environmental interest at lower metal concentrations and higher pH determine stability constants that are not currently known, the prime example being the plutonium-carbonate system assess the interplay of complexation, hydrolysis, and polymerization at environmental pH values, as these factors are important but not well understood under neutral conditions study the complex chemistry of plutonyl(V), which some workers believe to be an important species in ground waters attempt to elucidate the nature and behavior of polymeric species with the ultimate objective of developing quantitative, reproducible expressions for dispersion, precipitation. 

The solid state structure of rutherfordine, UO2CO3, has been determined from crystals of both the natural mineral and synthetic samples (see Figure 50). It has a layered structure in which the local coordination environment of the uranyl ion is hexagonal bipyramidal, with the uranyl units perpendicular to the orthorhombic plane. Each uranium atom forms six equatorial bonds with the oxygen atoms from two bidentate and two monodentate carbonates. The neptunyl and plutonyl analogs are isostructural with UO2CO3 based on Rietveldt analysis of powder X-ray diffraction data. 

---