Results 1 - 10 of 19888
Results 1 - 10 of 19888. Search took: 0.034 seconds
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[en] SuperLig(R) 644 (Trademark of IBC Advanced Technologies, American Fork, Utah) is an elutable resin that contains covalently bound macrocyclic ligands with high affinity for cesium in alkaline solution in the presence of sodium and potassium. The resin has been selected as the baseline ion exchange material for cesium removal from Hanford tank waste solutions. Extensive experimental investigations conducted at the Savannah River Technology Center (Aiken, South Carolina) and Battelle Pacific Northwest National Laboratory (Hanford, Washington) with simulated Hanford tank waste solutions indicated that SuperLig(R) 644 resin has adequate density and low-cycle physical durability, sufficient chemical stability, sufficient cesium sorption capacity and selectivity. Radioactive Hanford Site tank waste samples from tanks 241-AN-103, 241-AN-102 and 241-AZ-102 confirmed the simulant results
[en] We have developed a chemical separation technique that allows the radiochemical determination of the californium a-decay content in Department of Energy (DOE) high level wastes from the Hanford and Savannah River sites. The chemical separation technique uses a series of column extraction chromatography steps that use Eichrom Industries' lanthanide and actinide plus 3 oxidation state selective Ln-resin(R) and the transuranic selective plus 4 oxidation state TRU-resin(R) to obtain intermediate product phases in dilute nitric acid. The technique has been demonstrated on three types of authentic DOE high and low level waste samples. We obtain discrimination from Pu a-activity by a factor of over 200 and from Cm-244 a-activity by a factor approaching 1700. Californium recoveries are measured by addition of a Cf-249 spike and are in the range of 50 percent to 90 percent in the synthetic samples and are in the range of 1.4 percent to 48 percent for the authentic DOE waste samples
[en] Batch kinetic and column experiments have been carried out at 25, 35, and 45 Degrees C to examine the effect of temperature on SuperLig(R) 644 cesium (Cs) removal from simulated Hanford tank waste supernate. The simulated solution mimicked the composition of the low-activity waste supernate from tank 241-AN-105 in the U.S. DOE Hanford site. Small quantities of toxic metals, such as Cd, Cr, Fe, and Pb were spiked into the simulant to evaluate the metal's competitiveness with Cs for sorption on SuperLig(R) 644 resin. The results indicated that the temperature affects the removal of Cs and metal ions, although the effect was not the same for all metal ions. The extent of Cs removal decreased with an increase in temperature. The Cs capacity at breakthrough point was 0.015, 0.013, and 0.011-mmole/g dry resin at 25, 35 and 45 Degrees C, respectively. The column was effectively eluted to less than 1 Percent (0.1 C/Co) of the feed concentration with approximately 10 BVs of 0.5 M nitric acid. The resin showed limited affinity for toxic metal ions (Cr, Cd, Fe, and Pb) as compared to Cs. Based on the batch kinetic data, the Cs uptake of the resin was not hampered by the presence of the toxic metals in solution
[en] Batch contact and column experiments were performed to evaluate the effect of residence time on cesium (Cs) removal from two simulated Hanford tank wastes using SuperLig(R) 644 resin. The two waste simulants mimic the compositions of tanks 241-AZ-102 and 241-AN-107 at the U.S. Department of Energy (DOE) Hanford site. A single column made of glass tube (2.7-cm i.d.), which contained approximately 100 mL of H-form SuperLig(R) 644 resin was used in the column experiments. The experiments each consisted of loading, elution, and regeneration steps were performed at flow rates ranging from 0.64 to 8.2 BV/h for AZ-102 and from 1.5 to 18 BV/h for AN-107 simulant. The lowest flow rates of 0.64 and 1.5 BV/h were selected to evaluate less than optimal flow conditions in the plant. The range of the flow rates is consistent with the River Protection Project design for the waste treatment plant (WTP) columns, which will operate at a flow rate between 1.5 to 3 BV/h. Batch contact experiments were also performed for two batches of SuperLig(R) 644 to determine the equilibrium distribution coefficients (Kds) as a function of Cs concentration
[en] A new rapid separation method for radiostrontium in emergency milk samples was developed at the Savannah River Site (SRS) Environmental Bioassay Laboratory (Aiken, SC, USA) that will allow rapid separation and measurement of Sr-90 within 8 hours. The new method uses calcium phosphate precipitation, nitric acid dissolution of the precipitate to coagulate residual fat/proteins and a rapid strontium separation using Sr Resin (Eichrom Technologies, Darien, IL, USA) with vacuum-assisted flow rates. The method is much faster than previous method that use calcination or cation exchange pretreatment, has excellent chemical recovery, and effectively removes beta interferences. When a 100 ml sample aliquot is used, the method has a detection limit of 0.5 Bq/L, well below generic emergency action levels.
[en] In this paper, a separation of 209Po, 207Bi and 212Pb using AG 50Wx8 and AG MP 50 cation exchange resins in an HCl medium was developed. A procedure in which Po(IV) elutes first in 0.2 M HCl, followed by Bi(III) in 0.4 M HCl and finally Pb(II) in 2 M HCl was established. The separation using AG 50Wx8 provides a much better elution profile than that of AG MP 50 with no overlap between the elution bands. Finally, this separation has the potential to be used as an isotope generator for producing 210Po from 210Pb.
[en] The substoichiometric separation of Yb(III) can be achieved by the extraction of a substoichiometric amount of thenoyltrifluoroacetone and an excess amount of phenanthroline in benzene. The appropriate pH range for the substoichiometric extraction is 6-8. The reproducibility of the substoichiometric extraction of Yb(III) is very good (RSD 1%). As an example, Yb in a manganese nodule is determined by the substoichiometry combined with the radioactivation analysis. The content of Yb is 17.63+-0.23 μg/g. The present procedure can be applied to the determination of other rare erath elements. (author)
[en] The method for absolute estimation of software quality for doublet deconvolution based on a system of penalty points is presented. The method developed is an effective means for independeble and correspondence competition of programs for doublet processing and for fine tuning of these programs. The application of the suggested method is demonstrated and discussed on the example of test spectrum No. 400 by IAEA. (author)
[en] In human nutrition research, nuclear analytical techniques, particularly neutron activation analysis (NAA), are used mainly for the in vitro study of trace elements. According to work sponsored by the IAEA, up to 15 trace elements and 5 minor elements of nutritional interest may be determined in biological materials by NAA with good accuracy and precision. A programme is described in which NAA was used for the determination of 14 trace elements and one minor element in human milk. NAA also plays an important role in the certification of reference materials for nutritional studies. (author) 17 refs.; 6 tables
[en] Within the framework of the Protection of the Environment programme of the JRC-Ispra of the European Community, research on trace metal exposure and health effects is concerned primarily with the toxicological assessment of present levels of trace metals in the tissues of exposed and unexposed populations. Main activities are: microdetermination of trace elements in human tissues, metabolism and biochemical mechanisms involving trace metals to assess the toxicological significance of the current levels of the elements in the human body. A few selected applications related to the different steps of the biochemical toxicology research are shown. (author)