Plutonium environmental considerations

In comparison to plutonium both americium and curium are taken up by plants quite readily. The concentration factors for both americium and curium are 10-4 to 10-2 (127). While plutonium has been the subject of considerable research into its environmental impact there have been few investigations into americium and curium. Bondi-etti et al (94) have concluded that plutonium hydroxide polymers would be resistant... 

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... 

For practical considerations, one can use a conservative value of 7.4 kBq of plutonium proposed by the U.S. Environmental Protection Agency in 1985 as a recommended screening level , below which land can be considered suitable for unrestricted use (US EPA, 1985). This corresponds to a concentration of approximately 0.5 Bq g" for the soils in the region, where the observed penetration of plutonium into the soil is about 1 cm, or to a surface density of approximately 1 kBq m of Am in the north-west plume for which the measured ratio of plutonium to americium is seven (Bums et al., 1989). 

It is used in the mining industry to recover metals such as copper and nickel. Parasite plants, based on solvent extraction, are used in the phosphate industry to recover by-product uranium from crude phosphoric acid. The uranium concentration in phosphoric acid is very low but, because of the high volume of phosphoric acid that is produced to meet agricultural needs, considerable uranium can be recovered using solvent extraction. In the nuclear industry [5], solvent extraction is used to purify uranium and plutonium [using the plutonium and uranium recovery by extraction (PUREX) process], zirconium from hafnium, and for many other applications. It is also used in environmental applications to clean soil, say, to remove polychlorinated biphenyls (PCBs), dioxins, pesticides, and other hazardous pollutants. 

The operational costs of a plutonium-fuel fabrication facility are expected to be two to three times those currently encountered for the uranium-based fuel fabrication facilities, because of such considerations as personnel safety, physical security, and environmental restraints. Plutonium-fuel fabrication times are also expected to be increased by factors of 2 or 3 when compared to uranium-fuel fabrication times for similar reasons. 

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