Transport of Plutonium by Rivers 



H. J. SIMPSON, R. M. TRIER, and C. R. OLSEN 



A number of nuclear facilities are-iocated on rivers and estuaries, and thus it is important 

 to understand the primary transport pathways of transuranic elements in such systems. 

 Relatively few field studies of point-source releases of plutonium to river systems have 

 been made up to now. Information from research on the behavior of fallout plutonium in 

 rivers can, however, provide some useful insights. The range of variation of soluble-phase 

 fallout, ^^^'^^^Pu, in freshwaters and estuaries is relatively small (0.3 ± 0.2 fCi/ liter) and 

 appears to be "buffered" to some extent by the large reservoir of fallout '^^^''^^^Pu in 

 soils and the relative uniformity of the specific activity on soil particles (~20 pCi/kg). 

 The Hudson River, Hudson estuary. New York City tap water. New York bight, and 

 Great Lakes all have reasonably similar concentrations of soluble-phase 239,240^^^ 

 despite the large range of chemical and other characteristics. The distribution of fallout 

 2-3 9,2 4 Op^ l)QP^QQfi soluble phases and particles in rivers can be approximated by a 

 partition coefficient of about 10~^. For suspended particle loads of about 10 mg/liter, 

 which are reasonably typical of low-flow summer conditions for rivers in the northeastern 

 United States, '^^^-'^^^Pu is transported by both soluble phases and particles in 

 approximately equal amounts. For higher suspended loads, typical of northeastern rivers 

 during greater freshwater discharge and of most other large, nontropical rivers, the 

 transport of fallout ^^^'^^°Pw is clearly dominated by particles (by about an order of 

 magnitude ). For point-source addition of plutonium to a river, the most important 

 transport pathway appears to be binding to the suspended load and the mobile portions 

 of the fine-grain sediments and subsequent downstream movement with the fine particles. 

 Since the kinetics and downstream transport pathways of fine particles of a particular 

 river depend on a number of factors peculiar to each system, the most direct approach 

 would be to exploit the presence of "tracers" already present to define the parameters of 

 most relevance to transuranic-element transport over various time scales. Nuclear facilities 

 often release sufficient quantities of fission and activation products during normal 

 operations which can be used .as indicators of fine-particle transport pathways. The 

 behavior of these radionuclides cannot be expected to be identical to transuranic 

 elements in river systems, but those elements with strong particle-phase associations can 

 provide very useful information for sites of primary interest for transuranic-element 

 transport assessments. 



A number of nuclear power plants are now located on rivers and estuaries, and many 

 more probably will be in the future. The only major reprocessing faciUty currently 

 operating in the United States is located on a small tributary of the Savannah River. Thus 

 knowledge of the transport pathways of transuranic elements in rivers is essential for 



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