Pu In Sediments Research Articles

The distribution of plutonium, Americium and curium isotopes in pond and stream sediments of the Savannah river plant, South Carolina, USA

The concentrations of 238Pu, 239,240Pu, 241Am and 244Cm were determined in sediment samples from five streams and two ponds on the Savannah River Plant (SRP) and in four sediment samples from the Savannah River above and below the plant site. The following concentration ranges were determined: 238Pu, 0·07–386 fCi g −1; 239,240Pu, 0·37–1410 fCi g −1; 241Am, 0·1–4360 fCi g −1; 244Cm, <0·01–392 fCi g −1. Comparisons of the elemental and isotopic ratios of the sediments show that the majority of the sediments studied have been impacted upon by plant operations and that sediments outside the plant boundary in the Savannah River have only been influenced by aerial releases. Atom ratios of 240Pu/ 239Pu indicate that up to 86% of the Pu in these sediments is derived from plant operations. However, comparisons of the concentration data with values for other impacted sediments near nuclear facilities indicate that the levels are relatively small. Finally, <13% of the Pu, Am or Cm in pond sediments is associated with humic or fulvic acids, indicating that little of the material should be remobilized in oxic environments through organic complexation.

Distribution of plutonium and americium in Bikini Atoll lagoon.

Important factors that govern the redistribution and transport of radionuclides in Bikini Atoll Lagoon are particulate size and physical-chemical state. In water samples from Bikini the particulate fraction was collected on 0.3-μm millipore filters and the soluble fraction sorbed onto aluminum oxide beds. Sediments were collected by grab sampling or by coring. The radionuclides measured include 239,240Pu and 241Am. The largest source of radionuclides available for transport as indicated by 241Am and 239,240Pu in sediments and water samples reside in the deep water in the northwestern quadrant of the lagoon within approximately 6 km south of the second thermonuclear detonation-Shot Bravo. Small particles and/or ions of radionuclides are released at the sediment-water interface and are transported by the currents. These particles and ions agglomerate during transport away from the sediment surface. Coagulation with detritus and incorporation with plankton would cause the effective particulate size to increase. After about 16 yr, since the last nuclear test on the Atoll, the radionuclides are neither buried totally in the lagoon sediments nor have they been discharged completely to the ocean. There is a constant circulation and redistribution of the materials in the lagoon enforced by prevailing lagoon currents. The flux of americium and plutonium away from Bikini Atoll and into the North Equatorial Current are calculated to be about 3 Ci 241Am and 6 Ci 239,240Pu per year.