Americium production

At present, americium is separated and purified in Kg/yr quantities at the new plutonium facility at Los Alamos (Figure 1). The feed for the americium production comes from a line which produces high purity ceramic grade Pu02 for the Fast Flux Test Facility (FFTF) at Richland, Washington. The feed for this FFTF PuO is aged plutonium metal which contains sizable amounts of 24 Am... 

Later laboratory demonstrations using actual solutions, however, showed that acceptably pure product could be precipitated from a 4 or 6 g Am/L solution, the equivalent of evaporating the solution to about 900 L. Emission spectrographic analyses showed the total impurities of the americium product from both the 4 and 6 g/L solutions to be about 1.5 wt %. 

The countercurrent DBBP z 1hn extraction process was operated on a plant-scale for about six years. During that time, it provided excellent recovery ( vl00%) of soluble plutonium in the feed and adequate decontamination of 21flAm from plutonium and other metallic impurities. The Am/Pu ratio in the WS-1 Column (Am strip column) product was 2.5/1 compared to only 1/1 for the batch extraction process americium product. Concentrations of calcium, aluminum, and other metallic impurities in the counter-current Am product stream were also much lower than in the Am product from the batch extraction process. 

Mailen, J. C., D. O. Campbell, J. T. Bell, and E. D. Collins, Americium Product Solidification and Disposal, ORNL/TM-10226, Martin Marietta Energy Systems, Inc., Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1987. 

I cay product is neptunium-237. Identify the emission from americium-241. 

Figure 1 shows a simplified flow sheet for plutonium-239 recovery operations at Rocky Flats. Impure plutonium metal is sent through a pyrochemical process, called molten salt extraction (MSE), to remove the elemental impurity americium. The product plutonium metal, if it meets plant purity requirements, is sent to the foundry. Metal that does not meet foundry requirements is processed further, either through an aqueous process using ion exchange, or through a pyrochemical electrorefining process. The waste chloride salt from MSE is... 

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 extent of the first reaction is about 67%, which means that some of the MgCl2 remains in the bulk salt. In a typical 4.5-kg run containing 3000 ppm americium, 90% of the americium is oxidized at the expense of approximately 100 g plutonium. A typical product weighs 4400 g and contains 98% of the feed plutonium. ... 

Plutonium and americium recovery from MSE Salt Stripping Product. 

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. 

The large contribution of the fecal route to excretion of absorbed americium appears to be the result of excretion of americium into the bile. In monkeys that received an intravenous injection of americium citrate,241 Am was detected in gall bladder bile and its concentration increased as the relative rate of fecal excretion increased over time post injection (Durbin 1973). Durbin (1973) estimated that at bile production rates similar to humans, biliary excretion could have accounted for most, if not all, of the fecal excretion of americium observed in the monkeys. 

Americium is released into surface water primarily from plutonium production reactors, nuclear fuel reprocessing facilities, or in nuclear accidents. It may also be released from radioactive waste storage facilities. Since 241Pu decays into 241 Am,241 Am is also released as a result of 241Pu releases. Water sampling data were used to estimate effluent releases from the SRS from the plant s start up in... 

As a manufactured element, americium is not naturally present in rocks and soils. Contamination of the soil can occur either from deposition of americium or precursor plutonium originally discharged into the atmosphere, or from waste products discharged directly into or on the ground. Except for the reentry into... 

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... 

Methods for Determining Parent Compounds and Degradation Products in Environmental Media. Analytical methods with the required sensitivity and accuracy are available for quantification of americium, both total and isotopic, in environmental matrices (see Table 7-2). Knowledge of the levels of americium in various environmental media, along with the appropriate modeling (see Chapters 3 and 5), can be used to evaluate potential human exposures through inhalation and ingestion pathways. 

UIC. 1997. Most smoke detectors contain an artificially produced radioisotope americium-241. Americium-241 is made in nuclear reactors, and is a decay product of plutonium-241. Uranium Information Center. Nuclear Issues Briefing Paper 35. http //www.uic.com.au/nip35.htm. January 27, 2000. 

A multi-wall shipping container, holding 400 ml of a solution of americium chloride in a polythene bottle and sealed for over 3 months, exploded. The reason could have been a slow pressure build-up of radiolysis products. Venting and other precautions are recommended. 

As indicated earlier Kraus (9) has recognised three types of hydrolysis products of tetravalent thorium, uranium, plutonium and americium. These products are ... 

Ionization smoke detectors contain a small radioactive source (Americium 241) which ionizes air in a small chamber. The ions flow to a charged plate giving a measurable current. Products of combustion in the chamber are not easily ionized and absorb the radiation and reduce the current. The low current trips the alarm circuit. The size and composition of the particles are crucial to successful detection so that some types of smoke or vapor are detected at very low (invisible) levels. 

Americium, californium, and einsteinium oxides have been reduced by lanthanum metal, whereas thorium has been used as the reductant metal to prepare actinium, plutonium, and curium metals from their respective oxides. Berkelimn metal could also be prepared by Th reduction of Bk02 or Bk203, but the quantity of berkelium oxide available for reduction at one time has not been large enough to produce other than thin foils by this technique. Such a form of product metal can be very difficult to handle in subsequent experimentation. The rate and yield of Am from the reduction at 1525 K of americium dioxide with lanthanum metal are given in Fig. 2. 

Americium may be separated from other elements, particularly from the lanthanides or other actinide elements, by techniques involving oxidation, ion exchange and solvent extraction. One oxidation method involves precipitation of the metal in its trivalent state as oxalate (controlled precipitation). Alternatively, it may be separated by precipitating out lanthanide elements as fluorosilicates leaving americium in the solution. Americium may also he oxidized from trivalent to pentavalent state by hypochlorite in potassium carbonate solution. The product potassium americium (V) carbonate precipitates out. Curium and rare earth metals remain in the solution. An alternative approach is to oxidize Am3+ to Am022+ in dilute acid using peroxydisulfate. Am02 is soluble in fluoride solution, while trivalent curium and lanthanides are insoluble. 

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