A radiochemical isotope dilution mass spectrometry method has been developed to determine the age of uranium materials. The amount of 230 Th activity, the first progeny of 234U, that had grown into a small uranium metal sample was used to determine the elapsed time since the material was last radiochemically purified. To preserve the sample, only a small amount of oxidized uranium was removed from the surface of the sample and dissolved. Aliquots of the dissolved sample were spiked with 233U tracer and radiochemically purified by anion-exchange chromatography. The 234U isotopic concentration was then determined by thermal ionization mass spectrometry (TIMS). Additional aliquots of the sample were spiked with 229 Th tracer, and the thorium was purified using two sequential anion-exchange chromatography separations. The isotopic concentrations of 230 Th and 232 Th were determined by TIMS. The lack of any 232 Th confirmed the assumption that all thorium was removed from the uranium sample at the time of purification. The 230 Th and 234U mass concentrations were converted to activities and the 230 Th/234U ratio for the sample was calculated. The experimental 230 Th/234U ratio showed the uranium in this sample was radiochemically purified in about 1945.
A 3.7 MeV external proton beam was employed to produce X-rays in Pinus rigida Mill /pitch pine/ intra-annual growth rings and several elements were quantitatively determined. The PIXE experimental set-up, rapid sample preparation methods, and some interesting observations are discussed. In addition, statistical analysis of the tree-ring element concentrations revealed that Cl, K and Ca were slightly translocated whereas the other elements detected were not. The concentrations of several elements in the rings were negatively correlated with annual stream water pH which reflected precipitation pH.
Determination of 25 trace elements in the meteorites Allende and Murchison by ICP-MS is described. Samples are digested using HF, HNO3, and HClO4 at 140°C and diluted into HNO3. Element concentrations were determined using USGS terrestrial rocks as standards for calibration. Precision and accuracy of the technique, evaluated based on measurements of samples of known composition, are for 16 elements better than 10%.
Inductively coupled plasma mass spectrometry (ICP-MS) was evaluated for major, minor, trace, and ultra-trace elemental analyses of individual tree rings. The samples were obtained from an old-growth Douglas fir (Pseudotsuga menziesii) growing 15 km northeast of Mount St. Helens volcano, Washington, USA and from trees at various other North American sites. Samples were brought into solution by microwave digestion in sealed Teflon vessels. Eightly percent of elements from Li to U had detection limits in the solid (wood) below 8.0 ng g–1 (parts per billion, ppb). When selected element concentrations in the Mount St. Helens samples are plotted against time, two anomalous peaks occur at A. D. 1478 and 1490 that closely correlate with past eruptions of the volcano. These preliminary results show that ICP-MS is a rapid and sensitive analytical method for multielemental analyses of individual tree rings.
Authors:P. Warwick, N. Evans, A. Hall, G. Walker, and E. Steigleder
Conditional stability constants have been determined for U(IV) and U(VI) Boom Clay humic acid (BCHA) and Aldrich humic acid
(AHA) complexes, under anaerobic and carbonate free conditions. The constants are needed for nuclear waste repository performance
assessment purposes. The U(IV) constants were obtained by developing an approach based on the solubility product of amorphous
U(OH)4. The U(VI) constants were obtained by applying the Schubert ion-exchange approach.
Authors:G. Derrick, H. Sturk, A. Haynes, S. Chapman, and W. Hall
Reliability of citation searches is a cornerstone of bibliometric research. The authors compare simultaneous search returns
at two sites to demonstrate discrepancies that can occur as a result of differences in institutional subscriptions to the
Web of Science and Web of Knowledge. Such discrepancies may have significant implications for the reliability of bibliometric
research in general, but also for the calculation of individual and group indices used for promotion and funding decisions.
The authors caution care when describing the methods used in bibliometric analysis and when evaluating researchers from different
institutions. In both situations a description of the specific databases used would enable greater reliability.
Authors:G. Hall, N. Roach, U. Simmons, H. Cong, M-l. Lee, and E. Cummings
We have constructed an external beam proton-induced X-ray emission (PIXE) system for trace element analysis of biological and environmental samples. Optimization of sample preparation and experimental PIXE set up has produced a rapid, accurate, sensitive, and reliable PIXE analysis procedure. The analytical procedure was evaluated using maternal scalp hair from pregnant women 16–19 weeks' gestation. The samples were irradiated with 3.5 MeV protons from the Rutgers Nuclear Physics Department's 8 MV Tandem FN Van de Graaff accelerator. The concentrations of the elements calcium (Ca) to cadmium (Cd) in hair are reported for 50 subjects. The analytical procedure is suitable for non-invasive clinical analysis for evaluation of nutritional states and for environmental exposure to toxic metals.
Authors:S. P. LaMont, T. R. LaBone, J. R. Cadieux, W. M. Findley, G. Hall, C. R. Shick, D. W. Efurd, and R. E. Steiner
The lung dissolution rates for PuO2 were determined using a 100 day in vitro experiment. A very small amount of the PuO2 rapidly dissolved with a half-time of approximately 10 days, while the majority of the material (>99%) dissolved with a half-time
of approximately 5 . 105 days. This dissolution half time is significantly longer than what is recommended by the ICRP, and would result in higher
calculated doses for inhalation intakes of PuO2 than those currently estimated by the ICRP 66 human respiratory tract model for radiological protection.
Authors:D. Hoffman, R. Henderson, K. Gregorich, D. Bennett, R. Chasteler, C. Gannett, H. Hall, D. Lee, M. Nurmia, S. Cai, R. Agarwal, A. Charlop, Y. Chu, G. Seaborg, and R. Silva
The isotope260Lr, produced in reactions of18O with249Bk, was used to perform chemical experiments on lawrencium to learn more about its chemical properties. These experiments involved extractions with thenoyl trifluoroacetate, elutions from cation exchange resin columns with ammonium alpha-hydroxyisobutyrate, and reverse-phase chromatography using hydrogen di(2-ethylhexyl) orthophosphoric acid to investigate the chemical properties of Lr. The results from the elutions gave information about the ionic radius of Lr(III) which was found to elute very close to Er. An attempt to reduce Lr(III) with hydroxylamine hydrochloride was unsuccessful.