Electrodeposition of plutonium

The electrodeposition of plutonium is routinely employed as a means of preparing... 

The steps to be followed in the implementation of the electrodeposition of plutonium procedure are ... 

Irlweck, K. and Veselsky, J.C., The electrodeposition of plutonium at tracer concentrations from a mixed NHjCl/NHJ system. Int. J. Appl. Radiat. Isot., 26 (1975) 481-483. 

Electrolytic processes. Because of the positive oxidation potential for plutonium metal to displace hydrogen from aqueous solution, as shown in Table 9.7, nonaqueous solutions such as fused salts must be used for the electrodeposition of plutonium metal. One process involves the electrolysis of a molten equimolar mixture of LiCl-KCl containing 30 w/o FuQs. The melt is contained in a MgO-TiOi crucible heated to 950 C, with an anode through which chlorine gas can be introduced... 

Alpha Spectrometry. Electrodeposition of Plutonium The residue from Pu chemical separation was dissolved in 15 ml electrolyte (plating) solution (4 % (NH4)2C2O4/0.3 M HCl) and then transferred to an electrolysis cell. The beaker was washed with 15 ml deionised water and the washing was poured into the cell. Electrodeposition was carried out at 0.5 A, 20 V for 2-3 hrs. One minute before finishing... 

Electrodeposition of polonium on silver discs, as well as electrolysis of uranium and plutonium on steel discs... 

Preliminary studies have shown that ionic liquids have potential as solvents and electrolytes for metal recovery, and the feasibility of these solvents has been demonstrated for the extraction of gold and silver from a mineral matrix [7], the recovery of uranium and plutonium from spent nuclear fuel [8], and the electrodeposition and electrowinning of metals (especially, for active metals such as Li, Na, Al, Mg, and Ti) from ionic liquids [9-11], Ionic liquids as green solvents and electrolytes have shown important and potential application in extraction and separation of metals. In this chapter, the new applications and the important fundamental and appUed studies on the extraction and separation of metal in ionic liquids including metal oxides and minerals or ores processing, electrodeposition of metals (mainly for active metals), and extraction and separation of metal ions are described. 

Electrolysis through fused salts. Electrodeposition of metal fuel through a fused-salt electrolyte to separate uranium and plutonium from fission products was studied at Knolls Atomic Power Laboratory [N6]. 

Electrodeposition is currently used in a minority of laboratories to prepare a thin, uniform, and reproducible source. The alpha-particle emitting isotopes of plutonium are electrodeposited on polished stainless steel, or platinum disk. In the co-precipitation technique, a small amount of a carrier (e.g., LaF 3) is used to co-precipitate the separated and purified plutonium from solution. The precipitate is then prepared for counting by either filtration or by evaporation of a slurry of the precipitate onto a stainless steel disk or planchet (ASTM 1982 1987). Recent methods use a glass fiber filter which can be used as the source for alpha counting techniques. It has been suggested that low yields result from electrodeposition due to the presence of traces of interfering elements (e.g., iron) (Bernhardt 1976). 

Methods used for concentrating plutonium in a sample by a carrier are often specific to one oxidation state of the plutonium. For example, the classical bismuth phosphate-lanthanum fluoride method of concentrating plutonium from urine samples is specific to plutonium in the tri- and tetravalent states and will leave plutonium(VI) in solution. The fate of the various oxidation states of plutonium in man is not well understood and analysis procedures must insure reduction or oxidation of plutonium into appropriate oxidation states. Liver and kidney samples may contain metals (e.g., iron) which may greatly reduce chemical yields during the final electrodeposition step (Bernhardt 1976). 

Sensitive methods for analysis of plutonium in urine are particularly important for estimating occupational plutonium body burdens. Routinely available instrumentation, such as the alpha spectrometer, can readily detect these low concentrations. More sensitive methods are commonly required for urine samples in order to assess chronic exposures to plutonium. These low detection limits were first achieved in the past by nuclear emulsion track counting (see Table 6-1). In this method, the electrodeposited sample is exposed to nuclear track film, subsequent to the isolation of plutonium. The alpha-particle emitting isotopes of plutonium will leave tracks on the film which are counted to quantify the amount of plutonium. Nuclear emulsion track counting has been used in the past to measure plutonium concentrations in the urine of workers at a nuclear reactor plant (Nielsen and Beasley 1980). A type of scintillation counting has been used to measure plutonium-239 and americium-241 in animal tissues (NCRP 1985). 

Liquid-scintillation counting is a less common method used to measure plutonium concentrations from the various alpha-particle emitters among the isotopes of plutonium. Although liquid scintillation counting avoids the interferences from iron and other metals seen with electrodeposition, this method generally has higher detection limits than obtained with alpha spectrometry. In addition, the composition of the scintillation solution must be carefully controlled to prevent polymerization, deposition, or precipitation of the plutonium (NCRP 1985). 

Electrodeposition - Electrolytic reduction of plutonium at a platinum cathode. Preparation of sources for energy analysis. Very thin, uniform films arc attainable. Method can be made quantitative. Requires special preparation of solution, requires relatively long time to prep2irc 1 sample. 

Electrodeposition could be a pseudo-S-L type process, although definitive proof is lacking. The element to be ionized, uranium [16] or plutonium [17], is coelec-trodeposited with a platinum metal layer, then covered with an additional layer of platinum. The U or Pu is believed to be electrodeposited as an oxide, and platinum is electrodeposited as the metal. Hence there is thought to be a U or Pu oxide buried in the metal matrix. When this deposit is heated, after a sufficient length of time atomic cations of U or Pu begin to sublime from the surface without measurable metal oxide ions. Metal oxide ions should be readily observable if they are present in the matrix. Thermodynamic calculations indicate that the hot platinum matrix will not reduce the U and Pu oxides to the metallic state, and yet the observed species are atomic ions and not oxide molecular ions. 

Plutonium is electrodeposited onto a stainless steel disk to obtain a thin and uniform source for counting alpha particles. Counting is by spectral analysis to identify the plutonium alpha particles by peak energy and determine their activity by the integral of the count rate at the peak. 

One of the requirements of any nuclear facility is to monitor the effluent uxiste water to show compliance with existing standards. This paper describes a sequential procedure for the separation of the transuranic elements from water samples up to 60 1. The elements of interest are coprecipitated with calcium fluoride and then individually separated using a combination of ion exchange and solvent extraction, with a final sample preparation by electrodeposition. Alpha spectrometry of these samples allows the measurement of neptunium, plutonium, and transplutonium nuclides at sub-fCi/l, levels. 

A process for the extraction of uranium and plutonium metals with sodium amalgam from aqueous solutions has been developed. Amounts of mercury and sodium in the actinide metal after extraction were found to be less than 5 and 15 p.p.m., respectively. The preparation of thiol and thin films of neptunium, plutonium, americium, uranium, and californium by electrodeposition from organic solutions onto neutral foils has been described. ... 

Electrodeposition as a means of reducing plutonium to the metal has been limited by the corrosiveness of the chlorine and fused chloride environment. It also provides relatively little separation from impurities, except for those elements that form volatile chlorides [C2]. 

In this process, oxide fuel is dissolved in a molten chloride salt mixture through which Q2-HCI gas is flowing. Dissolved uranium and plutonium are then recovered as oxides by cathodic electrodeposition at 500 to 700°C. The process was demonstrated with kilogram quantities of irradiated fuel, with production of dense, crystalline UO2 or UO2-PUO2 reactor-grade material. Difficulties were experienced with process control, off-gas handling, electrolyte regeneration, and control of the plutonium/uranium ratio. Development has been discontinued. 

Some elements are not suitable for electrodeposition from aqueous solution as the metal. Among these are the radionuclides plutonium, uranium, and thorium, which are prepared for alpha-particle spectral analysis by deposition of oxides. Other metals, such as lead, can also be deposited as oxides under empirically derived conditions (Laitinen and Watkins 1975). 

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