SYNTHESIS OF THE RESEARCH LITERATURE 3 



as fallout was produced by an (n,7) reaction with ^^^U and the subsequent decay of 

 ^^^U through "^Np to ^^^Pu (Joseph et al., 1971).* Thus a proportion of the 

 plutonium in the environment was formed as single atoms long after the explosion and 

 was never involved in a reaction to form a high-fired oxide. 



The chemical form of transuranic elements released in small quantity during nuclear 

 fuel reprocessing and fabrication may range from relatively insoluble oxide particles, 

 which are of different composition than fallout (Sanders, 1977), to relatively soluble 

 inorganic salts and organic complexes, which may be present in solid and liquid wastes. A 

 generalized representation of the chemical forms of the transuranic elements released to 

 the environment is given in Table 1. 



TABLE 1 Major Sources and Initial Forms of 

 Transuranic Elements Entering the Environment 



*Tu denotes plutonium and possibly americium, curium, 

 and neptunium. M represents metal impurities, dust, and 

 gaseous condensation products. 



The potential movement of a transuranic pollutant from several sources, as illustrated 

 for plutonium in Fig. 1, can be classified according to expected initial solubility in surface 

 waters, interstitial waters of soils and sediments, and perhaps even on lung surfaces. 

 Initially, particulate oxides of transuranic elements may be largely insoluble in solution. 

 Ultimately, solubility will be a function of the chemical and physical properties of the 

 particle and the matrix in which the particle is deposited. Oxide particles of the highest 

 specific activity and containing the highest concentrations of impurities in the crystal 

 lattice will exhibit the greatest solubility. The combination of configuration and 

 equivalent diameter, as reflected in surface area exposed to solution, will also influence 

 the rate of oxide solubility. Once dissolved, transuranic elements will be subject to 

 chemical reactions governing dissolved salts. Hydrolyzable transuranic elements entering 

 the environment in solutions sufficiently acidic to maintain soluble ions and in 

 concentrations exceeding that of natural complexing agents will be rapidly hydrolyzed on 

 dilution and subsequently precipitated on particle surfaces. These include Pu(III, IV, and 

 likely VI), Am(III), Cm(III), and Np(IV and VI), ahhough the rates of hydrolysis will 

 vary between oxidation states. Conversely, chemical species of transuranic elements not 

 subject to marked hydrolysis, such as Pu(V) and Np(V), initially may be more soluble 



*As stated in the reference, approximately 1 x 10^" atoms of ^^'Pu were generated by the 

 explosion of thermonuclear weapons. This amounts to 4000 kg, or about two-thirds of the total 

 plutonium estimated to have been deposited on the surface of the earth. 



