Transuranic sediments

Livens FR, Hursthouse AS. 1993. Soil and sediment chemistry of the transuranic elements. Anal Proc 30 196-198. 

Approximate maximum concentration factors for selected transuranics in marine sediments, macroalgae, and fish... 

Table 32.23 Approximate Maximum Concentration Factors for Selected Transuranics in Marine Sediments, Macroalgae, and Fish...

The major repository of transuranic elements entering aquatic systems is the bed sediment (1-4). A significant portion is thought to arrive at the bed sediment surface as a result of association with, and subsequent settling of, suspended particulate matter. Concentrations of plutonium and americium in sediments relative to those in water reportedly range from 1 x IO" to 3 X 10 (32,33,34). Little information is currently available for other actinides of interest relative to nuclear fuel cycle wastes (Th, U, Cm and Np). 

Aston, S.R. and Stanners, DA. (1981) Observations on the deposition, mobility and chemical associations of plutonium in intertidal sediments. In Techniques for Identifying Transuranic Speciation in Aquatic Environments. IAEA, Vienna, pp. 209-218. 

Edgington, D.N., Alberts, J.J., Wahlgren, MA., Martunnen, J.O. and Reeve, C.A. (1976) Plutonium and americium in Lake Michigan sediments. In Transuranic Nuclides in the Environments. IAEA, Vienna, pp. 493-516. 

Livingston, H.D., Mann, D.R. and Bowen, V.T., Analytical procedures for transuranic elements in seawater and marine sediments. In Analytical Methods in Oceanography, Advances in Chemistry Series 147. American Chemical Society, 1975. 

Analytical Procedures for Transuranic Elements in Seawater and Marine Sediments... 

Transuranic elements are extracted from seawater by coprecipitation with either ferric hydroxide or calcium/strontium oxalate or are leached from sediments with 8M nitric acid. Radiochemical separations are used to aruilyze PUy... 

Most of the procedures for analysis of transuranic nuclides in seawater and marine sediments have been described in detail elsewhere both by our laboratory and those of other workers. A full discussion of these various procedures is found in a comprehensive state-of-the-art review of techniques proposed for the analyses of transuranic elements in the marine environment (4). Here we concentrate on the procedures used at the Woods Hole Oceanographic Institution, the problems encoim-tered, and what is being learned from the data. 

A full account of the problems considered in collecting, storing, and processing marine samples for transuranic analysis is given in the above-mentioned review (4). The specific methods discussed here were foimd effective at least for the transuranic analyses of seawater and sediments contaminated by global fallout, nuclear fuel reprocessing wastes, or nuclear power plant operation waste. In these cases, a preliminary acid treatment of the sample in the presence of suitable yield monitors seems to solubilize the transuranic elements and achieves isotopic equilibration between the yield monitor and sample. The yield monitors used were either Pu or sep qj. 238,239,240,24ip whereas Am was used for Am, 2 Cm, and by inference, Cf. In addition, it was convenient to use 50 mg of a lanthanide (neodymium) as a carrier for americium to purify the separated americium fraction. 

Sediment. About 50 g of dried sediment was used in transuranic element analyses. Two teachings of the sediment with 200 ml hot 8M nitric acid extracted the plutonium completely and, doubtless, other transuranic elements. Some workers prefer to fuse sediments completely (7, 8), but this is not necessary when the source of transuranic elements is global fallout or nuclear power plant waste. Fusion is probably essential when the transuranic elements in a sample are in relatively resistant... 

The transuranic elements extracted from seawater or sediments are further purified such that ... 

The International Atomic Energy Agency organized a series of interlaboratory comparisons for calibration purposes. Those completed so far include two seawater, one seaweed Fucus vesiculosus), and one sediment sample. These materials were contaminated in nuclear waste disposal situations and, in consequence, contain transuranic elements in concentrations much higher than those found in samples contaminated by global fallout of nuclear weapons testing debris. Nevertheless, the data speak directly to questions of calibration of detectors and yield... 

Table V shows some transuranic radionuclide concentrations found in near shore sediment close to Cape Cod, Mass. The total transuranic content of these shallow sediments agrees well with that predicted as being delivered to the latitude, arguing that the core segment represents part of the period of high 23sp delivery from SNAP 9A fallout. The implication is that all of the delivered transuranic element is rapidly deposited in the sediment in contrast to the "soluble fallout radionuclides.

Table VI shows the distribution of Pu, Tu, 239,24op j d within a sediment core collected several hundred miles northwest of the British Isles. Concentration profiles of plutonium and americium nuclides are rather similar in shape. The transuranic concentrations found in this sediment were surprisingly high. The high concentrations are believed to result from deposition of these nuclides from advected water carrying these nuclides from another area, rather than from the direct vertical transport of sinking particles.

Our initial series of sediment analyses for transuranic elements led ... 

G.R. Choppin (Florida State University) is investigating the synergistic reaction of actinide-TTA complexes with brown ether adducts in benzene solutions and interaction of plutonium and other transuranic elements with the components of marine sediments under different conditions. The interaction of plutonium-238 dioxide heat source with the marine environment is also under investigation by H.V. Weiss (Naval Coastal Systems Center). 

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