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PREPARATION, DENSITY,AND MELTINGPOINT OF l47Pm METAL
Preparation of Promethium-147 Metal and Determination of the Density and Melting Point1 by E. J. Wheelwright Battelle Memorial Institute, Pacific Northwest Laboratory, Rkhland, Washington 99968
(Received January 9, 1969)
Four 30-g buttons of I4’Pm metal have been prepared by Ca reduction of anhydrous PmC13. Additional purification was obtained by vacuum distillation of Ca and Mg impurities. The density of the metal was Sound to be 7.22 & 0.03 g/cma, and the melting point is 1168 & 6’.
I n 1963, Weigel reported the preparation of approximately 50 mg of P m metal by the reduction of PmF3 with Li Purity of the metal was not given, but the melting point was reported to be 1080 10”. Two years later, the author reported additional work with a similar small quantity of Pm. Again the purity of the metal was not reported, but the melting point was revised to 865 f 40°.4 The P m metal was perhaps impure and the revised melting point, observed by means of McWhan’s “solder-rupture” method, might have resulted from a rupture of the Pm bead a t the solidsolid phase transition temperature rather than from true melting. Consideration must be given to the problems encountered in performing this work with such a small amount of material. Under AEC sponsorship, efficient separation processes have been developed and more than 4 kg of highpurity 147Pmhave been Programs are in progress to study the chemistry of this heat-generating radioisotope and to carefully measure specific physical and chemical properties. The density and melting point of the metal, paramount values required for proper evaluation of I4’Pm metal for remote or portable energy-source a,pplications,were the first physical property measurements made,
Preparation of 14’Prn Metal Because of requirements of absolute containment and minimization of personnel exposure, all work with P m was performed in a stainless steel glove box covered with 0.5 in. of lead and equipped with both lead impregnated gloves and l-in. thick lead-glass viewing windows. I n anticipation of high reactivity of Pm metal in air, one module of the glove box was isolated by activation of an interconnecting air-lock and purged continually with argon. However, the glove box could not be made completely leak-tight, and the required negative differential pressure in that module resulted in continuous contamination of the argon atmosphere by air. Several methods of preparation were considered prior to finalizing on conventional calcium reduction, with an iodine booster, of anhydrous chloride as the process
which could be performed with a minimum of hand manipulation, would yield a reasonably pure metal, could be scaled up from 30-g batches to 100-g batches with little equipment change-out, and would require a minimum of equipment development and testing. The equipment was procured and tested, using Nd as a stand-in for Pm, prior to installation in the glove box. The chlorination was performed by flowing argon, saturated with CC4, upflow through 200 g of Nd203 supported on a fritted disk in a quartz tube held in a vertical tube furnace. The furnace temperature was increased from 450 to 600” in 50” increments over a 30-hr period. The reaction is report to proceed as8 Nd203
+ 3CC14 +2NdCl3 + 3COC12
and/or 2Nd203
+ 3CC14 +4NdC13 + 3C02
The off-gas products were removed by a caustic scrubber prior to discharge of the argon. The reduction was performed in a domed-bottom Ailgo crucible, sealed inside a small Inconel pressure bomb (International Nickel Co., Inc.). Button recovery was facilitated by employment of a thin-wall stainless steel can, designed to contain the crucible and slip, with close tolerances, into the pressure vessel. The void space between the crucible and can was filled with (1) Work performed under Contract AT(45-1)-1830 between Battelle-Northwest and the U. S. Atomic Energy Commission. ( 2 ) F. Weigel, Angew. Chem., 7 5 , 451 (1963). (3) F. Weigel, Angew Chem. Intern. Ed. Enol., 2, 326 (1963). (4) F. Weigel, Fifth Rare Earth Research Conference, Chemistry Session C, Ames, Iowa, Aug 30, 1965. (5) R. L. Moore, L. A. Bray, and F. P. Roberts, “Applications of Solvent Extraction Techniques to the Large-Scale Recovery and Purification of Fission Product Elements,” in “Solvent Extraction Chemistry of Metals,” H. A. C. McKay, Ed., Macmillan, London, 1965. (6) E. J. Wheelwright, F. P. Roberts, T. R. Myers, U. L. Upson, H. H. Van Tuyl, and L. J. Kirby, U. S. Atomic Energy Commission Unclassified Report, BNWL-318, Dec 1966. (7) E. J. Wheelwright and T. R. Myers, U. S. Atomic Energy Commission Unclassified Report, BNWL-SA-1493, Mar 1968. (8) J. F. Miller, S. E. Miller, and R. C. Himes, J . Amer. Chem. Soc., 81, 4449 (1959).
Volume 79,Number 9 September 1960
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E. J. WHEELWRIGHT PRESSURE GAGE
Table I: Impurities Found in Nd Metal Prepared during Equipment Testing
Impurity
Concentration, ppm weight baais
Sm
