Distribution Of Americium Research Articles

Whole-body distribution of americium in rats for different pathways of intake

Purpose: To compare data on the whole-body distribution of americium-241 (241Am) in rats following intravenous injection (IV), inhalation, and wound (intramuscular injection, IM).Material and methods: Following exposure, each rat was placed in an individual metabolism cages for the duration of the study, 28 days (d). Urine and feces were collected daily. Tissues and organs were collected and measured.Results: Liver and skeleton were the main sites of deposition for all routes of exposure but the content differed substantially. By 28 d, 241Am content in liver was similar for IV and IM administrations (12 ± 4% and 14 ± 5%, respectively), which was 3-fold higher compared to inhalation. Americium-241 content in skeleton was 27% by the end of the IV study; which was 50% higher compared to the IM study and 6-fold higher compared to inhalation. The cumulative excretion in 28 d was 54% for IV (44% by feces and 10% by urine); 38% for IM (34% by feces and 4% by urine); and 84% for inhalation (83% by feces and 1% by urine).Conclusion: Unperturbed rat models for the three routes of administration are the baseline for evaluating the efficacy of chelating agents.

Biochemical fractionation and cellular distribution of americium and plutonium in the biomass of freshwater macrophytes

Accumulation of americium (241Am) and plutonium (238,242Pu) and their distribution in cell compartments and biochemical components of the biomass of freshwater aquatic plants Elodea canadensis,Ceratophyllum demersum and Myrioplyllum spicatum and aquatic moss Fontinalis antipyretica have been investigated in laboratory experiments. Americium and plutonium taken up from water by Elodea canadensis apical shoots were mainly absorbed by structural components of plant cells (90% for 241Am; 89% for 238Pu and 82–87% for 242Pu). About 10–18% of isotope activity was recorded in the cytosol fraction. The major concentration (76–92%) of americium was bound to cell wall cellulose-like polysaccharides of Elodea canadensis, Myriophyllum spicatum, Ceratophyllum demersum and Fontinalis antipyretica, 8–24% of americium activity was registered in the fraction of proteins and carbohydrates, and just a minor concentration (<1%) in the lipid fraction. The distribution of plutonium in the biomass fractions of Elodea was similar to that of americium. Hence, americium and plutonium had the highest affinity to cellulose-like polysaccharides of cell walls of freshwater submerged macrophytes.

AMERICIUM IN THE BEAGLE DOG: BIOKINETIC AND DOSIMETRIC MODEL

A biokinetic model of the systemic distribution of americium in the beagle dog is presented. The model is based on a previous biokinetic model of plutonium. The data sets used for the development of the model were the measurements of excreted activity (urine and feces) and organ burdens (skeleton, liver, and other soft tissues) for different levels of initial injected activity. In developing the model, the compartmental structure of the skeleton of the plutonium model was adopted, and only the numerical values of parameters were adapted. The model well describes the fractions of americium in the skeleton, liver, and soft tissues and the total fraction excreted in urine and feces. The tuning of the liver clearance parameter provides a realistic description of the change in the partitioning between liver and skeleton for different injection levels. The most significant features of the biokinetics and dosimetry of americium and plutonium in beagles are compared. The total fractions of the clearance to the skeleton and the liver are roughly equal to the value for plutonium, but the partitioning of americium between these organs is reversed with respect to the partitioning of plutonium. 241Am doses to liver and skeleton are similar to 239Pu doses, owing to some counteracting factors. For the highest injection level, the liver mass is dependent on the time post injection. For the skeletal tissues, the dose to the cortical endosteum by far exceeds the dose to the trabecular endosteum and the red marrow. The model provides the basis for statistical survival analyses and risk estimates.

Assessment of the exposure pathway in the uptake and distribution of americium and cesium in cuttlefish ( Sepia officinalis) at different stages of its life cycle

Laboratory radiotracer experiments were performed to study the uptake, assimilation and retention of americium ( 241Am) and cesium ( 134Cs) by the common cuttlefish Sepia officinalis. Uptake and loss kinetics of the radionuclides were measured following exposure through sediments, seawater and food at different stages of the animal's life cycle. Sediment was found to be a minor uptake pathway for both radionuclides in juveniles. Following a short seawater exposure, cuttlefish accumulated 241Am and 134Cs, but only to a limited extent (whole-body CF < 2). Among the cuttlefish organs, branchial hearts and their appendages displayed the highest degree of uptake for 241Am (CF = 42 and 16, respectively), but these tissues contained low percentage of total 241Am due to their relatively small contribution to whole organism weight. The major fraction of incorporated radionuclides was associated with muscular tissues (viz. 65% and 82% of total 241Am and 134Cs, respectively). Whole-body loss of 241Am and 134Cs was relatively rapid ( T b½ = 14 and 6 days, respectively). After dietary exposure, around 60% and 30% of ingested 241Am was assimilated into the tissues of juvenile and adult cuttlefish, respectively. However, assimilated 241Am was more strongly retained in adults than in juveniles ( T b½ = 28 vs. 5 days, respectively), suggesting that different mechanisms govern 241Am elimination at both ages. Ingested 134Cs was assimilated to a similar extent in juveniles (29%) and adults (23%), but the depuration rate was four times faster in adults. Our results strongly suggest that these two radionuclides follow different excretion pathways and that the mechanisms can vary with age for a given radionuclide.

Americium complexation by acetylacetone studied by akufve alpha on-line liquid-scintillation technique

The distribution of americium(III) trace concentrations between chloroform and 1 M NaClO 4 has been measured as a function of pH and acetylacetone (HAa) concentration (conc. range 3.0 to 0.01 M in CHCl 3) using the AKUFVE closed flow mixer-centrifugal separator with a newly devised alpha on-line liquid scintillation technique. The dependency of the detector on solution composition and interfering or disturbing physical factors such as quenching compounds, sorption, entrainment, radiation background, etc. is described. At high pH slow kinetics are encountered. Most of these phenomena can be directly observed and corrected for in the AKUFVE run, yielding “clean” distribution curves. From these curves it is concluded that in the aqueous phase, the complexes AmAa 2+, AmAa 2 +, AmAa 3 and AmAa 4 − are formed, and in the organic phase probably AmAa 3 and AmAa 3·HAa; equilibrium constants are calculated.

Americium in intertidal sediments from the coastal environs of Windscale

The distribution of americium in surface intertidal sediments from a coastal environment near the Windscale nuclear fuel reprocessing plant has been investigated. The study includes data on the broadscale distribution of 241Am in Northwest England, but focuses on the sediments of the Ravenglass estuary 10 km south of Windscale. The results indicate that americium concentrations in the inner estuary sediments are up to seven times higher than those from the Irish Sea itself. Americium distribution on silt banks is rather constant on a small scale, but varies considerably between adjacent silt bank and salt marsh areas.

Distribution of americium between liquid plutonium and a fused salt. Evidence for divalent americium

The distribution of Am between liquid Pu metal and a fused salt of NaClKCl containing PuCl 3 has been studied at 698, 730 and 775°C over a PuCl 3 mole fraction range of 6 × 10 −3 to 2 × 10 −2. The distribution data are consistent with the following equation ▪ From the temperature dependence of the equilibrium constant, a value of −3.5 kcal is estimated for ΔH° for the above reaction.

In vitro Distribution of Americium in Human Blood Serum Proteins

THE distribution of plutonium in blood serum proteins has been investigated previously1–3. Normally, americium-241 is present in plutonium samples, and is produced there by the β-decay of plutonium-241. Accordingly it is of interest to compare the distribution of americium in blood serum proteins with that of plutonium.

Studies of the Liquid-Liquid Partition Systems. III. The Solvent Extraction of Americium(III) and Europium(III) Thiocyanate Complexes with Tributylphosphate

Abstract The two-phase distribution of americium(III) and europium (III) has been studied between the hexane solution of tributylphosphate (TBP) and the aqueous solution of sodium thiocyanate at 25°C. From the distribution data when the organic phase was 5% (by volume) TBP in hexane and the aqueous phase was 5 m Na(SCN, ClO4), the following equilibrium constants have been obtained by a least-squares method: (Remark: Graphics omitted.) A remarkable salting-out effect has been observed when sodium perchlorate is added to the aqueous phase. This salting-out effect has been discussed, as has the solvation number of TBP in the adduct complexes in the organic phase.