Environmental Actinide Science
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Environmental
Actinide Science
Robert J. Silva and Heino Nitsche This article is a short qualitative summary of a chapter in the forthcoming book Advances in Plutonium Chemistry: 1967–2000, edited by Darleane Hoffman for the Amarillo National Research Center. Readers are referred to the chapter for more technical details.
Introduction Considerable progress has been made in the study of environmental plutonium science in the last 30-plus years, driven to a large extent by concerns about the release and migration of large amounts of plutonium into the accessible geosphere. Plutonium has been introduced into the environment through several pathways. Environmental contamination has been caused by nuclear-weapons production and testing, nuclear-reactor accidents, and accidents during the transport of nuclear weapons. Above-ground testing of more than 420 nuclear weapons has produced large amounts of radionuclides through fission and neutron activation products. More than three metric tons of plutonium have been distributed on the earth’s surface by global fallout.1 For example, the MAYAK plutonium production complex in the former Soviet Union is located in the southern Urals, about 70 km north of Chelyabinsk and 15 km east of Kyshtym. Between 1949 and 1951, about 76 million m3 of liquid radioactive waste with a total activity of 100 PBq (2.7 MCi) were discharged into the Techa River.2,3 The reactor explosions in 1986 in Chernobyl2 released 23 kg of plutonium isotopes totaling 6.5 PBq (0.18 MCi). Within a 30-mi radius, the concentration of 239,240Pu is between 3.7 GBq/km2 and 185 GBq/km2 (0.1–5 Ci/km2). Large areas in Belorussia and Ukraine were contaminated also. Severe contaminations occurred in the United States at sites within the nuclearweapons complex. The Hanford Site in southeastern Washington State was the first industrial-scale plutonium production site. Between 1944 and 1981, approximately 220,000 m3 of liquid reprocessing waste, totaling 11.8 EBq (320 MCi), were pro-
MRS BULLETIN/SEPTEMBER 2001
duced and are stored in 149 single-shell and 28 double-shell steel tanks.4,5 As much as 3800 m3 of radioactive contaminated liquid were released into the environment. During the earlier times of operation, some high-level wastes (HLW) and other contaminated liquids were discharged directly into the ground through trenches and shallow subsurface drainage systems, so-called cribs. The released volume of more than one billion m3 contaminated around 500 km2 with radionuclides and toxic chemicals. At Oak Ridge National Laboratory (ORNL), 160,000 m3 of liquid waste containing fission products and transuranium elements were directly discharged into the ground, thus creating a radioactive burden of about 44.4 TBq (1.2 kCi). In the whole U.S. weapons complex, 5700 contaminated groundwater plumes exist, and estimates for the volume of contaminated soil range from 73 million to 200 million m3. At Sellafield, the British nuclear-fuel reprocessing plant, between 1950 and 1992, discharges were made into the Irish Sea of 120 TBq
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