Americium process

Kilogram quantities of americium as Am can be obtained by the processing of reactor-produced plutonium. Much of this material contains an appreciable proportion of Pu, which is the parent of Am. Separation of the americium is effected by precipitation, ion exchange, or solvent extraction. 

For the neutron porosity measurement, fast neutrons are emitted from a 7.5-curie (Ci) americium-beryllium (Am-Be) source. The quantities of hydrogen in the formation, in the form of water or oil-filled porosity as well as crystallization water in the rock if any, primarily control the rate at which the neutrons slow down to epithermal and thermal energies. Neutrons are detected in near- and far-spacing detectors, located laterally above the source. Ratio processing is used for borehole compensation. 

Figure 3 shows a flowsheet for plutonium processing at Rocky Flats. Impure plutonium metal is sent through a molten salt extraction (MSE) process to remove americium. The purified plutonium metal is sent to the foundry. Plutonium metal that does not meet foundry requirements is processed further, either through an aqueous or electrorefining process. The waste chloride salt from MSE is dissolved then the actinides are precipitated with carbonate and redissolved in 7f1 HN03 and finally, the plutonium is recovered by an anion exchange process. 

MSE Processing of High-Grade Plutonium Scrap. Americium is remove3 from plutonium in a liquid-liquid extraction process using molten salt (KC1, NaCl, MgCl2) and molten plutonium metal... 

Spent Zirflex Process Decladdent. The basic perceived need is to devise an3 develop a simple process for selective and efficient removal of plutonium (and 21 1Am) from spent Zirflex process decladdent solution. To satisfy this need, it may be necessary--or prove beneficial—to determine, by appropriate physiochemical methods, the nature of the plutonium (and americium) species in the decladding solution. Availability of a satisfactory transuranium removal scheme may be one of the key factors in devising an alternative to storage in expensive double-shell tanks for spent Zirflex process solution at the Hanford site. 

We are not aware of any previous studies of the removal of plutonium or americium from (NH )2ZrF6-NHltF-NH N03 solutions. For ready plant-scale application, precipitation, sorption on inorganic materials, or batch solvent extraction processes may all be satisfactory. An inexpensive inorganic material with great selectivity and capacity for sorbing actinides, and with suitable hydraulic properties, would be especially attractive. 

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... 

Molten salt extraction residues are processed to recover plutonium by an aqueous precipitation process. The residues are dissolved in dilute HC1, the actinides are precipitated with potassium carbonate, and the precipitate redissolved in nitric acid (7M) to convert from a chloride to a nitrate system. The plutonium is then recovered from the 7M HNO3 by anion exchange and the effluent sent to waste or americium recovery. We are studying actinide (III) carbonate chemistry and looking at new... 

The following pages will describe several examples of pyrochemical processing as applied to the recycle of plutonium, and will briefly review the fundamental chemistry of these processes. We shall review the conversion of plutonium oxide to plutonium metal by the direct oxide reduction process (DOR),the removal of americium from metallic plutonium by molten salt extraction (MSE), and the purification of metallic... 

Early experimental work in electrorefining at Los Alamos by Mullins et-all ) demonstrated that americium could be partitioned between molten plutonium and a molten NaCl-KCl salt containing Pu+3 ions, and Knighton et-al(8), working at ANL on molten salt separation processes for fuel reprocessing, demonstrated that americium could be extracted from Mg-Zn-Pu-Am alloys with immiscible molten magnesium chloride salts. Work... 

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 ... 

Present production processes use two stage counter-current extraction to remove americium from molten plutonium with magnesium chloride based salts. Both 35 mole % NaCl - 35 mole % KC1 - 3D mole % MgCl2 and 50 mole % NaCl-26 mole % CaCl2 - 24 mole % Mg Cl 2 are used for americium extraction. Figures 4 and 5 show the ternary phase diagrams for these salt systemsU0). 

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,... 

Americium Extraction (more commonly referred to as Molten Salt Ex-or MSE). This process is specifically designed to reduce the americium content of the plutonium metal. (Am241 spontaneously grows into plutonium as a result of Pu241 decay.) When the impure metal contains more than 1000 ppm of americium, it is run through the MSE process. Otherwise, it bypasses the MSE step and proceeds directly to electrorefining. 

Molten Salt Extraction (MSE) - Salt Recovery. The salt residue from the americium extraction process is made up of NaCl, KC1, MgCl2, PuCl3, and AmCl3. A typical residue weighs approximately 2.0 kg and contains 200 g plutonium, 10-20 g americium, 50 g MgCl3 with the remaining equimolar NaCl-KCl. 

The stripping approach seems to be practical. Future work will investigate the disposition of the americium. Work will be done to establish proper operating conditions and optimize process yields. 

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. 

Write a nuclear equation for each of the following processes (a) oxygen-17 produced by a particle bombardment of nitrogen-14 (b) americium-240 produced by neutron bombardment of plutonium-239. 

Colchicine (a drug used in treatment of gout) and vinblastine (a cancer chemotherapy agent) may decrease liver uptake of americium. In rats that received an intraperitoneal injection of either colchicine and vinblastine prior to an intravenous or intramuscular injection of americium citrate, liver uptake of americium was lower, relative to controls, and kidney and skeletal americium uptake were higher (Seidel 1984, 1985). The effect is thought to involve disruption of hepatic microtubule formation, which is critical to the formation and intracellular processing of lysosomes, the initial site of accumulation of americium in the liver. 

Distribution of241 Am in a dialysis system containing sediment, phytoplankton, and detrital matter established that a substantial amount of americium accumulated in all three phases both in fresh and marine waters (NRC 1981). The adsorption process was not reversible and the longer the americium was adsorbed, the more difficult the chemical was to desorb. Appreciable amounts of americium have been shown to adsorb to bacterial cells such as those found in the Waste Isolation Pilot Plant in New Mexico (Francis et al. 1998). There is a potential that americium attached to biocolloids may facilitate its transport from the waste site. 

The principal abiotic processes affecting americium in water is the precipitation and complex formation. In natural waters, americium solubility is limited by the formation of hydroxyl-carbonate (AmOHC03) precipitates. Solubility is unaffected by redox condition. Increased solubility at higher temperatures may be relevant in the environment of radionuclide repositories. In environmental waters, americium occurs in the +3 oxidation state oxidation-reduction reactions are not significant (Toran 1994). 

Workers at plutonium reprocessing facilities, nuclear reactors, transuranium and low level waste storage facilities, or those engaged in the production or processing of243Am or241 Am may be occupationally exposed to americium. In addition, workers at sites where nuclear testing was conducted may also be exposed to americium. Workers in nuclear power stations may be exposed to airborne radionuclides. The... 

Rainey, R. H. Development of the Amex Process for Americium Recovery. 

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