Americium , and

In general, the absorption bands of the actinide ions are some ten times more intense than those of the lanthanide ions. Fluorescence, for example, is observed in the trichlorides of uranium, neptunium, americium, and curium, diluted with lanthanum chloride (15). 

The spent salt from MSE is currently sent to an aqueous dissolution/carbonate precipitation process to recover plutonium and americium. Efforts to recover plutonium and americium from spent NaCl-KCl-MgCl2 MSE salts using pyrochemistry have been partially successful (3). Metallothermic reductions using Al-Mg and Zn-Mg alloys have been used in the past to recover plutonium and americium, and produce salts which meet plant discard limits. Attempts at direct reductions of MSE salts using... 

A production process has evolved from this original work, and is presently used for extracting americium from kilogram amounts of plutonium metal. This process is based upon equilibrium partitioning (by oxidation-reduction reactions) of americium and plutonium between the molten chloride salt and the molten plutonium phase. The chemistry of this process is indicated by the following reactions ... 

The NaCl-KCl eutectic is used when the pregnant extraction salt is to be processed by aqueous recovery (this is the salt currently used at Rocky Flats because calcium follows americium in the present aqueous recovery process). The NaCl-CaCl system is used when the salt is processed by pyrochemical means to recover the americium and residual plutonium. When the pyrochemical recovery technique is used, the NaCl-CaCl2-MgCl2 salt is contacted with liquid calcium metal at approximately 850°C in a batch extractor. The calcium reduces A111CI3,... 

Figure 10 shows in graphic form the utility of molten salt extractions for americium removal in one, two, and three stage extractions for various salt-to-metal extraction feeds. This graph demonstrates the impressive power of molten salt extraction systems for purification of plutonium from americium and related rare earth elements. 

Molten Salt Extraction Salts Plutonium and Americium Recovery. We have demonstrated the ability to successfully strip the plutonium from the MSE salts. The resulting metal product now contains as much as 10% americium and as a result cannot be fed directly into the metal processing sequence. To use the plutonium we must remove the americium. 

Holden NE (1989) Total and spontaneous fission half-lives for uranium, plutonium, americium and curium nuclides. Pure Appl Chem 61(8) 1483-1504... 

Dacheux N, Aupiais J (1997) Determination of uranium, thorium, plutonium, americium, and curium ultratraces by photon electron rejecting alpha liquid scintillation. Anal Chem 69 2275-2282 Duan YX, Chamberlin EP, Olivares JA (1997) Development of a new high-efficiency thermal ionization source for mass spectrometry. Inti JMass Spectrom IonProcessesl61 27-39 Edwards RL, Chen JH, Wasserburg GJ (1987) systematics and the precise... 

Physical and Chemical Properties of Americium and Selected Americium Compounds... 

This public health statement tells you about americium and the effects of exposure. 

The model is designed to simulate oral, inhalation, and parenteral (e.g., injection) exposures to americium and cannot be applied to other routes of exposure without modification. 

Information on the transplacental transfer of americium in humans is not available directly, but the information from experiments with americium and other actinides has been used to derive biokinetic models and perform dosimetric models for the human (NCRP 1998 NRC 1996 Sikov and Kelman 1989). Studies in animals that received parenteral injections of americium have shown that absorbed americium is transferred to the fetus (Hisamatsu and Takizawa 1983 Paquet et al. 1998 Sasser at al. 1986 Schoeters et al. 1990 Weiss et al. 1980) (see Section 3.4.2.1). Limited reports indicate that241 Am may induce fetal death and teratogenic effects in rodents (Moskalev et al. 1969 Rommerein and Sikov 1986). 

The known oxidation states of americium are +2, +3, +4, +5, and +6. However, the stable oxidation states are +3 and +4 the common oxidation state is +3, in which state, the behavior of americium and... 

Using transfer factors derived for uptake into plants and animals, Friberg and Vesanen (1999) have listed critical activity levels for americium and other nuclides deposited on soil and pasture vegetation from a nuclear accident required to exceed the action level for foodstuffs recommended by the IAEA. Experiments have been conducted to assess uptake of241 Am and other radionuclides from fallout or nuclear facilities in plants. 

Physical, Chemical, and Radiological Properties. Data on the physical and chemical properties of americium and americium compounds are available in the literature (Cotton and Wilkinson 1980 Lide 1994, 1998 Nenot and Stather 1980 Seaborg 1991). Data are also available on the radiological properties of americium isotopes (ICRP 1983 Lide 1998). 

Bioavailability from Environmental Media. The absorption and distribution of americium as a result of inhalation and ingestion exposures have been discussed in Sections 3.3.1 and 3.3.2. EPA lists identical uptake factors for inhaled and ingested americium (and all the other transuranics other than plutonium) regardless of compound solubility, indicating that the knowledge base for americium is not sufficiently developed to quantify the differences that are recognized for most other elements. 

In vitro analyses of americium are routinely performed in situations where in vivo analyses cannot be obtained or in support of an in vivo monitoring program. Urine is the preferred sample for in vitro analyses of americium, although other sample types, such as feces, tissue, bone, or blood, can also be used on a more limited basis. Urine provides for an analysis of soluble or transportable americium, fecal analysis can be used to measure ingestion or clearance of americium, and tissue is used to assess whole or regional body burdens of americium (Guilmette and Bay 1981 Ide 1986 Ide et al. 1985 Mclnroy et al. 1985). 

One of the limitations of the portable field survey instruments in the measurement of americium is that their quantitative accuracy depends on how well the lateral and vertical distribution of americium in the soil compares with the calibration parameters used. These methods can provide a rapid assessment of americium levels on or below surfaces in a particular environment however, laboratory-based analyses of samples procured from these environmental surfaces must be performed in order to ensure accurate quantification of americium (and other radionuclides). This is due, in part, to the strong self absorption of the 59.5 keV gamma-ray by environmental media, such as soil. Consequently, the uncertainty in the depth distribution of americium and the density of the environmental media may contribute to a >30% error in the field survey measurements. Currently, refinements in calibration strategies are being developed to improve both the precision and accuracy (10%) of gamma-ray spectroscopy measurements of americium within contaminated soils (Fong and Alvarez 1997). 

Bomben AM, Equillor HE, Oliveira AA. 1994. Simultaneous biphasic liquid scintillation determination of americium and plutonium. J Radioanal Nucl Chem 177(l) 27-37. 

Bulman RA. 1978. The movement of plutonium, americium, and curium through the food chain. 

Carter RE, Busch E, Johnson O. 1951. The relative physiological and toxicological properties of americium and plutonium. GRAI 14(NTIS/DEC95013620). 

Carvalho FP, Fowler SW. 1985. Biokinetics of plutonium, americium and californium in the marine isopod Cirolcma borealis, with observations on its feeding and molting behavior. Mar Biol 89 173-181. 

Cooper JR, Gowing HS. 1981. The binding of americium and curium to human serum proteins. IntJ Radiat Biol 40(5) 569-572. 

Crawley FEH, Goddard EA. 1976. The translocation of 241-americium and 242-curium from the respiratory system of the rat. Health Phys 30 191-197. 

Dacheux N, Aupiais J. 1997. Determination of uranium, thorium, plutonium, americium, and curium ultratraces by photon electron rejection a liquid scintillation. Anal Chem 69 2275-2282. 

Dacheux N, Aupiais J. 1998. Determination of low concentrations of americium and curium by photon/electron rejecting alpha liquid scintillation. Anal Chim Acta 363 279-294. 

Directorate of Fisheries Research. 1990. Determination of alpha-emitting nuclides of plutonium, americium and curium in environmental materials Pt. 1. Seawater. Lowestoft, England Directorate of Fisheries Research. NTIS/DE92614732. 

Durand JP, Milcent MC, Goudard F, et al. 1994. Chemical behavior of three radionuclides (cesium, americium and technetium) and their uptake at the cystosolic level in aquatic organisms. Biochem Mol Biol Int 33(3) 521-534. 

Ellender M, Haines JW, Harrison JD. 1995. The distribution and retention of plutonium, americium and uranium in CBA/H mice. Hum Exp Toxicol 14 38-48. 

Ham GJ, Stradling GN, Breadmore SE. 1977. Determination of americium and curium in biological samples of extraction and liquid scintillation. Anal Chem 49 1268-1270. 

Hammond SE, Lagerquist CR, Mann JR. 1968. Americium and plutonium urine excretion following acute inhalation exposure to high-fired oxides. Am Ind Hyg Assoc J 29(2) 169-172. 

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