Rapid plutonium

Ohtsuka, Y., Takaku, Y., Kimura, J., Hisamatsu, S., and Inaba, J., Development of rapid plutonium analysis for environmental samples by isotope dilution/inductively coupled plasma mass spectrometry with on-line column, Anal. Sci., 21, 205-208, 2005. 

The corrosion behavior of plutonium metal has been summarized (60,61). a-Plutonium oxidizes very slowly in dry air, typically <10 mm/yr. The rate is accelerated by water vapor. Thus, a bright metal surface tarnishes rapidly in normal environments and a powdery surface soon forms. Eventually green PUO2 [12059-95-9] covers the surface. Plutonium is similar to uranium with respect to corrosion characteristics. The stabilization of 5-Pu confers substantial corrosion resistance to Pu in the same way that stabilization of y-U yields a more corrosion-resistant metal. The reaction of Pu metal with Hquid water produces both oxides and oxide-hydrides (62). The reaction with water vapor above 100°C also produces oxides and hydride (63). 

The first definite production of plutonium metal was made in November, 1943 by Baumbach and coworkers (1958). Approximately 35 micrograms of PuFi in a small thoria crucible in a high vacuum was reacted with barium metal at 1400 C to yield plutonium metal. The metal was found to have a silvery lustre, a density of about 16 grams j>er cubic centimeter and it rapidly absorbed hydrogen at about 210 C to form a black powder subsequently identified as PUH3 (a proof that metal had been produced). 

Vapor pressures and vapor compositions in equilibrium with a hypostoichiometric plutonium dioxide condensed phase have been calculated for the temperature range 1500 I H 4000 K. Thermodynamic functions for the condensed phase and for each of the gaseous species were combined with an oxygen-potential model, which we extended from the solid into the liquid region to obtain the partial pressures of O2, 0, Pu, PuO and Pu02 as functions of temperature and of condensed phase composition. The calculated oxygen pressures increase rapidly as stoichiometry is approached. At least part of this increase is a consequence of the exclusion of Pu +... 

This untimely polymer formation is understood to be caused by the very rapid hydrolysis and aggregation of monomeric Pu(IV) species (at the region of condensate reentry into the hot plutonium solution) to produce hydrous polymers that are not readily depolymerized. At high temperatures such as found under reflux conditions, the polymer rapidly ages through the conversion of hydroxyl- to oxo-bridges ... 

The existence of plutonium with an oxidation state of V (or VI) in neutral solutions or at high pH and in the presence of carbonate was previously observed (51). It has also been suggested that Pu(V) is the dominant oxidation state in sea-water and that Pu(VI) is rapidly reduced to Pu(V) in these waters (52). 

A second source of plutonium, dispersed more locally, is liquid effluent from fuel reprocessing facilities. One such is the fuel reprocessing plant at Windscale, Cumbria in the United Kingdom where liquid waste is released to the Irish Sea(6). Chemical analysis of this effluent shows that about one percent or less of the plutonium is in an oxidized form before it contacts the marine water(7). Approximately 95 percent of the plutonium rapidly adsorbs to particulate matter after discharge and deposits on the seabed while 5 percent is removed from the area as a soluble component ). Because this source provided concentrations that were readily detected, pioneering field research into plutonium oxidation states in the marine environment was conducted at this location. 

The mechanisms by which Pu(IV) is oxidized in aquatic environments is not entirely clear. At Oak Ridge, laboratory experiments have shown that oxidation occurs when small volumes of unhydrolyzed Pu(IV) species (i.e., Pu(IV) in strong acid solution as a citric acid complex or in 45 percent Na2Coj) are added to large volumes of neutral-to-alkaline solutions(23). In repeated experiments, the ratios of oxidized to reduced species were not reproducible after dilution/hydrolysis, nor did the ratios of the oxidation states come to any equilibrium concentrations after two months of observation. These results indicate that rapid oxidation probably occurs at some step in the hydrolysis of reduced plutonium, but that this oxidation was not experimentally controllable. The subsequent failure of the various experimental solutions to converge to similar high ratios of Pu(V+VI)/Pu(III+IV) demonstrated that the rate of oxidation is extremely slow after Pu(IV) hydrolysis reactions are complete. 

These observations contrast with some of the results obtained in natural waters. In the experiments where contaminated sediments were equilibrated with Lake Michigan water for a number of days, the Pu(IV) that was on the sediments and was transferred to the water was oxidized to Pu(V), with the oxidation occurring either during or after desorption (15). The studies in the Irish Sea near Windscale show that although no more than 1 percent of the waste effluent stream is oxidized plutonium, approximately 5 percent of the plutonium released leaves the area in the currents of the Irish Sea as oxidized plutonium. Most of the plutonium, therefore, must be oxidized fairly rapidly in sea water. 

Ideally, this information should be made available in the form of easy-to-use nomographs or empirical equations which can be quickly and rapidly solved on a programmable desk calculator. New instrumentation which can be used on an in-line basis to analyze process streams for the concentrations of plutonium in different oxidation states is also needed. 

The basic electrorefining process is now being used on a production scale for the purification of non-specification plutonium metal. The technology is sufficiently well developed to permit 24-hour unattended operation of the electrorefining cells, and the quality of the product metal is highly consistent. This technology is rapidly replacing aqueous chemistry for plutonium metal purification. 

Induced nuclear fission is fission caused by bombarding a heavy nucleus with neutrons (Fig. 17.23). The nucleus breaks into two fragments when struck by a projectile. Nuclei that can undergo induced fission are called fissionable. For most nuclei, fission takes place only if the impinging neutrons travel so rapidly that they can smash into the nucleus and drive it apart with the shock of impact uranium-238 undergoes fission in this way. Fissile nuclei, however, are nuclei that can be nudged into breaking apart even by slow neutrons. They include uranium-235, uranium-233, and plutonium-239—the fuels of nuclear power plants. 

The aqueous chemistry of plutonium is dictated by two factors its tendency to hydrolyse and its tendency to form complexes. As the plutonium ions have a high charge and relatively small ionic radius they all exhibit a strong tendency to hydrolyse quite rapidly. Kraus (9) has shown that the tendency to hydrolyse follows the order ... 

At the end of the above reaction sequence Pu(OH)4 precipitates out - Katz and Seaborg (11) have calculated the solubility product as 7 x 10-56. Polymer formation is a rapid process when the Pu4+ solution is adjusted to contain 0.4 x 10 4m to 1.2 x 10 2m in 0.1m HN03,40% of the plutonium polymerised within the first 30 minutes and within 60 minutes 55 % had polymerised. 

Catalado and Craig (134) demonstrated that the maximum accumulation of plutonium occurred when the plant had attained its maximum growth. However, Catalado and Craig did not demonstrate that this maximum accumulation of plutonium was the result of elevated citrate levels in the plant tissue. The presence of citrate in the leaves could exert a significant alteration in the foliar transport of Pu02 since it has been shown that citrate (10-4m) can bring about a rapid solubilisation of small particles of Pu02 (38). 

Because the isotope uranium-235 is fissionable, meaning that it produces free neutrons that cause other atoms to split, it generates enough free neutrons to make it unstable. When the unstable U-235 reaches a critical mass of a few pounds, it produces a self-sustaining fission chain reaction that results in a rapid explosion with tremendous energy and becomes a nuclear (atomic) bomb. The first nuclear bombs were made of uranium and plutonium. Today, both of these fuels are used in reactors to produce electrical power. Moderators (control rods) in nuclear power reactors absorb some of the neutrons, which prevents the mass... 

The first actinide metals to be prepared were those of the three members of the actinide series present in nature in macro amounts, namely, thorium (Th), protactinium (Pa), and uranium (U). Until the discovery of neptunium (Np) and plutonium (Pu) and the subsequent manufacture of milligram amounts of these metals during the hectic World War II years (i.e., the early 1940s), no other actinide element was known. The demand for Pu metal for military purposes resulted in rapid development of preparative methods and considerable study of the chemical and physical properties of the other actinide metals in order to obtain basic knowledge of these unusual metallic elements. 

The effects of tetracycline injection following injection of thorium-228 were not reported. Studies with a similar actinide element, plutonium, suggest that a thorium-tetracycline complex may be formed, which is excreted rapidly through the kidneys. Similarly, chelating agents such as EDTA... 

Bernabee RP. 1983. A rapid method for the determination of americium, curium, plutonium and thorium in biological and environmental samples. Health Phys 44 688-692. 

Figure 3 illustrates the distributions found for Pu and Am when a mixed sample of these tracers was infiltrated into a large (30 cm x 30 cm) block of Bandolier tuff (6). The nuclide activities were determined simultaneously by coring sections of the tuff and represent the activity distributions in the rock. It is obvious that although the activities are both normalized at 100% at the surface the increased dispersion of the plutonium concentration during elution leads to an increase of almost an order of magnitude in its activity relative to Am at the 5-6 cm depth. It is highly unlikely that abnormal flow paths or movement of colloidal clay particles would discriminate between americium and plutonium therefore this experimental result tends to discount these possible types of mechanisms. However, a pure Pu polymer could carry the Pu more rapidly downstream. 

The only recorded hydroxide, Pu(0H)3 jcH20, rapidly oxidizes to a plutonium(IV) species, but two forms of Pu203 are known, one with the hexagonal La203 structure and the other cubic in these the Pu3+ is seven- and six-coordinate respectively. Ternary oxides, such as PuA103, are also known. 

The only other recorded compound for the +3 oxidation state is the 8-hydroxyquinoline complex, Pu(C9H6NO)3, precipitated when an aqueous solution containing plutonium(III) is added dropwise, in a stream of nitrogen, to an aqueous solution of the ligand in the presence of reducing agents. It is rapidly oxidized in air. 

All the known tetraalkoxides are very easily hydrolyzed by water vapour and the uranium(IV) compounds oxidize rapidly in air, so their preparation must be carried out under nitrogen. Molecular weight determinations (M = Th, U) indicate a considerable degree of polymerization, approximately tetrameric in the case of Th(OR)4 with R = Pr or MeEtCH, but the molecular complexity decreases to about 3.4 for R = Bu, and with R = CEt3 and CMeEtPr the alkoxides are monomers in boiling benzene.653 The plutonium compound Pu(OCMeEt2)4 is volatile at 150 °C/0.05 torr, suggesting a low molecular complexity. 

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