Americium oxidation

ICRP (1995) considers the experimental data on americium nitrate, chloride, citrate, and hydroxide to support classification of these compounds as either Type F or M. Americium oxides are classified as Type... 

Predictions based on the model have been compared to observed time courses for lung, liver, and skeletal americium burden in dogs that inhaled americium oxide (Mewhinney and Griffith 1983). Data on lung retention for four humans who accidentally inhaled americium were also compared to model predictions. The empirical observations fell within predicted retention patterns for particle sizes (AMAD) 0.5 and 1.8 im (Mewhinney and Griffith 1983). 

Property Americium Americium dioxide Americium oxide Americium chloride... 

Americium metal has been obtained by heating americium oxide, Am203, with lanthanum at 1,200 °C americium, which is more volatile than other actinides, volatilizes and can readily be separated from other actinides. Am02 can be obtained by igniting most trivalent americium compounds (Budavari 1996 Cotton and Wilkinson 1980 UIC 1997). 

Newton D, Taylor BT, Eakins JD. 1983. Differential clearance of plutonium and americium oxides from the human lung. Health Phys 44(Suppl. 1) 431-439. 

Only a few compounds of americium exist. The most important is americium oxide (AmOj), whose main use is in the preparation of other compounds. Americium can also form compounds with the halogens, similar to other transuranic elements—for example, americium iodide (Aml ), americium fluoride, and americium chloride (AmF and ArnGl ). 

In research at the Institute of Radiochemistry, Karlsruhe. West Germany during the early 1970s, investigators prepared alloys of americium with platinum, palladium, and indium. These alloys were prepared by hydrogen reduction of the americium oxide in the presence of finely divided noble metals according to ... 

Solubility of Americium Oxide. The dissolution process of Am02 under normal or anoxic conditions in near neutral to alkaline solution includes the reduction of Am4+ to Am3+, which turns the solution phase gradually into an oxidizing medium as Am02 dissolves. For this reason, the solubility of Am02 with respect to pH differs distinctively from that of Am(OH)3 at pH < 9. The primary dissolution process may be expressed as follows ... 

The process sequence currently used for waste salts (except those containing aluminum for which no process currently exists) is shown in Figure 1. The process includes (1) dilute hydrochloric acid dissolution of residues (2) cation exchange to convert from the chloride to the nitrate system and to remove gross amounts of monovalent impurities (3) anion exchange separation of plutonium (4) oxalate precipitation of americium and (5) calcination of the oxalate at 600°C to yield americium oxide. 

The flowsheet for the FFTF Pu02 production is shown in Figure 2. Briefly, the plutonium metal is converted to an impure oxide by burning the metal in air. This is followed by dissolution of the impure oxide in a 15.6 M HN03 - 0.5 M HF solution. The americium is separated from the plutonium by precipitation of the plutonium as the peroxide. Americium does not form an insoluble peroxide and stays in the filtrate with other cationic impurities. The active peroxide filtrate is slowly dripped into 9 M NaOH. The combination of strong alkali and heat destroys the peroxides and precipitates the americium as the hydroxide. Any residual plutonium in the filtrate, along with other cations, is precipitated also as the hydroxide. The flowsheet for the americium oxide production is shown in Figure 3. 

Finally, the black-brown americium oxide is sieved through a 170 mesh 7.6 cm screen on a mechanical shaker. A complete analysis is done to determine whether the Am02 meets the required product specifications. The analysis of representative batches of americium oxide produced at LASL is shown in Table II. Radiochemistry, emission spectroscopy, calorimetry, and spark source mass spectrometry are used in the analysis of the Am02. Providing the Am02 meets all of the product specifications, it is prepared for shipment. Product not meeting these specifications is recycled through the process at the proper entry point. 

Ross, R. G. Wiggins, J. T. "Preparation of Curium-Americium Oxide Microspheres by Resin-Bead Loading", paper presented at Symposium on Industrial Scale Production-Separation-Recovery of Transplutonium Elements, 2nd Chem. Congr. North American Continent, Las Vegas, NV, 1980. 

Preparation of Curium-Americium Oxide Microspheres by Resin-Bead Loading... 

The size of the curium-americium oxide particles is an important criterion in the production of HFIR targets because of the relatively high oxide content in the blend. The oxide particles must be uniformly dispersed in the aluminum pellets/ and the pressed pellets must have a continuous aluminum phase to... 

In the following sections, a brief chronology of the development of this process is presented the materials, equipment, and basic operations relating to the resin-bead loading and calcination method of producing sized curium-americium oxide microspheres at TRU are described and typical production data are presented. 

The equipment for curium-americium oxide production (illustrated schematically in Fig. 2) is located on a rack within a master-slave manipulator-equipped hot cell in the TRU cell bank. The feed adjustment and raffinate collection vessels are located in a tank pit in another part of the cell bank. General design considerations and operating philosophies for chemical process operations at TRU have been described previously (4) Only equipment items that are unique to the curium-americium oxide production are discussed below. 

Figure L Curium-americium oxide microsphere production by Dowex 50W-X8 resin-bead loading and calcination...

Figure 2. Schematic arrangement of equipment for the production of curium-americium oxide microspheres...

The sintering step (to 1050°C) is carried out in a laboratory muffle furnace with the curium-americium oxide contained in an open 50-mL platinum-lined Inconel crucible. 

The production and oxide characterization data for a series of curium-americium oxide production runs are presented in Table I. The table includes the composite feed analyses, the product data for each run, and a summary of the product data. Totals and averages are presented to indicate performance even though the products are not usually combined. Approximately 93.7% of the feed material was converted into product. The normal losses of actinides from the product are the result of oxide particles that stick to the product handling equipment. These are not actual process losses because they are eventually returned to rework. 

The analysis of the composite sample from the same series of curium-americium oxide production runs is presented in Table II. The content of carbon, the major impurity, is inferred rather than directly analyzed. The analyses of curium-americium oxide products generally reflect the purity of the feed, except for carbon and sulfur from the resin and a few potential corrosion products. 

Resin-bead loading and calcination techniques have been used to produce all curium and americium oxide feed material... 

Table I. Typical Curium-Americium Oxide Production Data [Data from a series of runs made March 2-8/ 1978]...

Table II Typical Curium-Americium Oxide Impurity Levels...

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