.. AL AU " . Mia . J . . 1 O ** 1 " Win UNCLASSIFIED ORNL :. 27 784 رم 0 1 - 77 ANTIES DECLE: Cong. 641110-1 PREPARATION OF ULIRA PURE CALCIUM CARBONATE FROM ' ELECTROMAGNETICALLY PRODUCED 48ca FOR CALCIUM FLUORIDE OPTICAL CRYSTAL GROWTH* MASTES J. 0. Younghanse R. L. Bailey H. R. Gwinn The recovery and chemical refinement of electromagnetically separated isotopes presents some special problems. Perhaps the major difficulties are to prevent isotopic dilution and to avoid cor.tamination by other elements, particularly tbose which would be difficult to remove without the use of complicated chemical processes. Every erfort is made to eliminate or minimize contamination from equipment components during the separation process so chemical purification procedures for the re- o? non ha admiPod. covered material can be sin Although 48ca is one of the least abundant calcium isotopes (0.185% natural abundance), it is one of the isotopes for which there is the greatest demand. Enriching 1 g of 48ca from its natural abundance to *Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation. . >96% isotopic purity requires ~5500 calutron tank hours so the result- ing sample represents a considerable investmer.t in time and money. . To fill a special request from Brookhaven National Laboratory, a 14-8 sample of 96.44% 48Ca was transferred to Harshaw Chemical Company where the material was converted to calcium fluoride, 0.5% europium was added as a scintillator, and a single crystal was grown. This cylindrical crystal containing 10 g of 48ce was mounted in a stainless steel sleeve to form an optical device and transferred to Brookhaven for use in experi- ments designed to study double beta decay in 48 Ca. During initial phases of the experiment, an alpha activity of 4000 counts per hour was detected. This was an intolerable interference, and the experiment had to be discontinued. It was BNL's opinion that the alpha emitting contaminant in the crystal was due to uranium estimated to be present in the amount of ~1 ppm. Uranium had not been observed in the inventory samples at ORNL as shown by spectrographic analyses. Create you The 48Ca used in the cryetal grown for the Brookhaven project had been collected in copper receiver pockets, which 18 a standard procedure. After the receiver assembly is removed from the calutron and disassembled, the outside surfaces of these collector pockets are thoroughly cleaned with dilute nitric acid, and recove:ry and refinement of the separated material is performed according to an established procedure. A typical spectrographic analysis of the refined 48Ca shows barium, stront ium, magnesium, silicon, and sodium present as impurities in small amounts. After notification of the uranium contamination problem, an analysis man aikana was made of a l-g 48ca sample which had been processed immediately after the material which was sent to Harshaw. The results showed the uranium content to be 12 ppb. This analysis was made using a special mass spectro- meter technique and substantiated our belief that uranium would be elimi- nated by the established refinement procedure since it employed the citrate, oxilates, and carbonates as precipitants for calcium. These reagents are also excellent complexing agents for uranium. pun EXAM 200 © A check was also made on salvage materials returned from Harshaw to ORNL for recovery of the enziched isotope. Four batches, ranging from a few grams of calcium fluoride powder to 3.5 gal of solution containing only a few milligrams of calcium, were anlyzed using a fluorometric process, and the uranium content was determined to be ~ppm. The decision was made to return the first crystal from Brookhaven to the ORNL Electromagnetic Separations Departuent for repurification. some me.... This reprocessing was approached with caution since the value of the r original 48ca in the crystal had now been multiplied by accumulated se miks momencensentere fabrication costs. Even more exacting rules of cleanliness aná technique .. han were imposed during this processing. All equipment was new and specially cleaned; reagents were specially selected from those used in the original refinement; exposure to room air was minimized. The crystal was removed from the stainless steel sleeve and placed in a stainless steel mortar. The mortar and pestle were placed in a · polyethylene bag, and the bag was sealed. Manipulation of the pestle inside the sealed bag crushed the crystal and the sample was then transferred to a platinum dish and weighed. (A 4-mg 1088 was sustained in the crushing operation. The calcium fluoride was decomposed with boiling perchloric acid, and a sample was removed for uranium analysis. A mass spectrometer technique was used, and the assay showed 27 ppb of uranium with almost normal isotopic distribution of this contaminant. Amnonium hydroxide was added to preci pitate the 0.5% europium scintillator before the previously described refinement procedure was perforned on the material. Spectrographic analysis of the final sample indicated the presence of 100 ppm Ba, 500 ppm Sr, and 40 ppm Mg, but no special effort was made to remove these elements. A mass spectro- meter technique was also used, and the sample was shown to contain <0.5 ppb of uranium (0.46). The reprocessed 48Ca was returned to Harshaw, another crystal was grown for Brookhaven, and the experiments were continued. The detectable alpha activity bad been reduced by a factor of 5 over the level shown to be present in the original crystal. --LEGAL NOTICE – Two report mo prepared una acount of Governeol sponsored wort. Nellbar ebe Vallad suales, sor the Commissloa, por may porno scur oo behall of the Coa mission: A. Makes may norunly or no prescoustion, expressed or implied, with respect to the accu- racy, completeness, or wewnus of the informasuon coalaland la o report, or that we we I any lalor melloa, apparatus, colod, or prxcou klowed u this report way sot lairinge privately oned rucu; or B. Air:Des may ludillues mu respect to the use of, or for damages reowuing from the Nu of uy lalormation, apparatus, meldod, or process dixcloud in We report. 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