368 TRANS URANIC ELEMENTS IN THE ENVIRONMENT 



uptake of these two transuranics was approximately a factor of 16 times that of 

 plutonium. 



The significance of these CR values can be related to transuranics associated with 

 plutonium breeder reactor fuels. Thomas and Healy (1976) reviewed the uptake of 

 neptunium and transplutonium elements by plants. They calculated the relative 

 abundance of a number of long-lived transuranics relative to ^"'^Pu from data reported 

 earher by Bell (1970) on nuclide levels in spent Liquid Metal Fast Breeder Reactor 

 (LMFBR) fuels. As shown in Table 3, the concentration of ^"^ • Am, ^''^ Cm, ^-^ ^Np, and 

 ^■^^Np in vegetation would be higher than that of ^^^Pu for various time periods 

 following environmental releases of spent LMFBR fuels. A difference is noted in the 

 relative plant uptake values summarized by Thomas and Healy for americium and 

 neptunium when compared with the values reported in this study. The discrepancy in the 

 americium values is probably due to the fact that they included uptake data in which the 

 soil had been amended v^th a chelating agent, such as diethylenetriaminepentaacetic acid, 

 which significantly increases plant uptake (Hale and Wallace, 1970; Wallace, 1972). Their 

 relative neptunium uptake value was taken from Price (1972) and was approximately 

 one-tenth of the results presented here. Price noted some toxicity symptoms in the 

 neptunium-contaminated seedlings which may have caused a reduction in neptunium 

 uptake. 



Another interesting finding in this study was the low concentrations of transuranics 

 in pea and barley seeds when compared with those of the entire plant. This is important 

 because in many dose-assessment models the CR values used are often calculated from the 

 entire aboveground plant parts. As shown in this study, the levels of plutonium, 

 americium, and curium in barley seeds were lower by a factor of 30 to 50 of those in the 

 entire plant. For neptunium the seeds were one-fifth of the entire plant values. Pea seeds 

 were lower by a factor of 70 to 230 for plutonium, americium, and curium and a factor 

 of 30 lower for neptunium. Differences in plant-part concentrations must be considered 

 when CR values are used in dose-assessment models and can also describe some of the 

 discrepancy in CR values reported in the literature. 



Acknowledgments 



We thank W. T.- Hinds for his technical guidance during the initial stages of this study 

 and H. A. Sweany, M. J. Harris, L. F. Nelson, M. A. Combs, and V. D. Charles for their 

 teclinical assistance througliout the study. This research was funded by the U. S. 

 Department of Energy, Office of Health and Environmental Research, under contract 

 EY-76-C-06-1830. 



References 



Bell, M. J., 1970, Heavy Element Composition of Spent Power Reactor Fuels, USAEC Report 



ORNL-TM-2897, Oak Ridiie National Laboratory, NTIS. 

 Qine, J. F., 1968, Uptake of ^'" Am and "'Pu by Plants, in Pacific Northwest Laboratory Annual 



Report for 1967 to the USAEC Division of Biology and Mcdicinf. USAEC Report BNWL-714. pp. 



8.24-8.25, Battelle, Pacific Northwest Laboratories, NTIS. 

 Energy Research and Development Administration, 1975, Workshop on Environmental Research for 



Transuranium Elements, Proceedings of the Workshop, Battelle Seattle Research Center, Seattle, 



Wash., Nov. 12-14, 1975, ERDA Report ERDA-76/134, NTIS. 

 Hale, V. Q.. and A. Wallace, 1970, Effect of Chelates on Uptake of Some Heavy Metal Radionuclides 



from Soil by Bush Beans. Soil Sci., 109: 262-263. 



