382 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



determine plant uptake of plutonium under both field and controlled conditions (Francis, 

 1973; Price, 1972; Hanson, 1975; Bennett, 1976), However, most of these experiments 

 were done in pot culture; experiments done in the field involved only nonagricultural 

 vegetation. This general lack of information on field-grown crops is apparent from the 

 proceedings of the 1976 international symposium on the Transuranium Nuclides in the 

 Environment {InXQxmiiondX Atomic Energy Agency, 1976). 



This chapter describes plutonium contents of crops grown on fields at the U. S. 

 Department of Energy Savannah River Plant (SRP) and at Oak Ridge National 

 Laboratory (ORNL) in soils containing plutonium concentrations at levels above those 

 attributable to fallout from nuclear weapon tests. The fields at SRP, near Aiken, S. C, 

 have been receiving plutonium at low chronic levels from the emission stack of a 

 reprocessing facility since 1955; the field plots at ORNL are located on the White Oak 

 Creek floodplain, which received plutonium from Manhattan Project operations in 1944. 

 We compared the plutonium contents of major grain crops (wheat, soybeans, and corn) at 

 SRP, where the major mode of contamination is through deposition from the emission 

 stack, with those of major vegetable crops at Oak Ridge, where the major pathway of 

 contamination is via root uptake. 



Description and History of the Study Sites 



Savannah River Plant 



The SRP is on a reservation of 77,830 ha. Public access to the reservation has been 

 controlled since its acquisition in 1951. The reservation consists of freshwater streams, 

 old fields, and forest; most of the old fields are in the upper Coastal Terraces. 



For over 20 yr this integrated nuclear complex has included nuclear reactors (three of 

 the original five are operating at present), two nuclear-fuel reprocessing plants, a fuel 

 fabrication facihty, a heavy-water production unit, and nuclear and environmental 

 research laboratories (Fig. 1). It also includes an ecological research laboratory to assess 

 the effects of nuclear technology on the environment and its biota. The reprocessing 

 plants (F and H) and global fallout are the sources of the transuranic elements that enter 

 the SRP environs. Each source releases plutonium of unique isotopic composition: 25 and 

 95 a % ^^^Pu.* from the F- and H-area reprocessing facilities, respectively, and 10 a % 

 ^^^Pu from global fallout. These isotopic differences provide a convenient basis for 

 studying the origin and transport of plutonium in various SRP ecosystems. 



In 1974 two crop fields were estabhshed adjacent to the H-area reprocessing facility. 

 Low-level atmospheric releases of plutonium have occurred from H area since the start of 

 operations in July 1955. Approximately 440 mCi of plutonium had been released from H 

 area before the installation of high-efficiency filters on the exhaust-air systems in 

 December 1955. These releases contained 2 3 9,24 0p^ From 1956 through 1966, 

 2 3 9,2 4 0pjj re[easgs averaged 4 mCi/yr. From 1967 through 1974, normal releases 

 averaged 12 mCi ^^^Pu/yr and 4 mCi ^^^'^'^'^Pu/yr. An accidental failure of the filtering 

 mechanism in 1969 released an additional 560 mCi of ^^^Pu and 58 mCi of "^'^"^^Pu. 

 Total releases through 1974 were 640 mCi of " ^Pu and 570 mCi of "^ '^"^^Pu. 



* ~238t, ^^*Pu alpha activity ,^„ 



*a % ^^*Pu = --; r-^- — — I -^-. — X 100. 



total plutonium alpha activity 



