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Abstract  

There is a significant discrepancy in the reported values for the emission probability of the 186 keV gamma-ray resulting from the alpha decay of 226 Ra to 186 keV excited state of 222 Rn. Published values fall in the range of 3.28 to 3.59 gamma-rays per 100 alpha-decays. An interesting observation is that the lower value, 3.28, is based on measuring the 186 keV gamma-ray intensity relative to the 226 Ra alpha-branch to the 186 keV level. The higher values, which are close to 3.59, are based on measuring the gamma-ray intensity from mass standards of 226 Ra that are traceable to the mass standards prepared by HÓNIGSCHMID in the early 1930's. This discrepancy was resolved in this work by carefully measuring the 226 Ra alpha-branch intensities, then applying the theoretical E2 multipolarity internal conversion coefficient of 0.692±0.007 to calculate the 186 keV gamma-ray emission probability. The measured value for the alpha branch to the 186 keV excited state was (6.16±0.03)%, which gives a 186 keV gamma-ray emission probability of (3.64±0.04)%. This value is in excellent agreement with the most recently reported 186 keV gamma-ray emission probabilities determined using 226 Ra mass standards.

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Abstract  

The parameters for a sulfate based electrodeposition method were optimized for the preparation of Cm and Np alpha-spectrometry sources. Alpha-spectrometry requires the preparation of essentially massless sources to eliminate self-absorption of alpha-particles, which can cause degraded alpha-spectra. A variety of methods for the electrodeposition of actinides have been reported in the literature, many of which require long deposition times and lack reproducibility. A previously reported sulfate based method has been evaluated for the preparation of Np and Cm sources. High yields were achieved and source preparation took 90 minutes or less. The effects of electrodeposition time and pH of the depositing solution were evaluated for each element. Typical resolution (FWHM) for sources prepared by this method is 50 keV or less with recoveries approaching 100%.

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Abstract  

An extraction chromatographic method is described for the pre-concentration and separation of thorium, uranium, plutonium and americium in human soft tissues. Tissues such as lung and liver are oven dried at 120°C, ashed at 450°C and the ashed sample is alternately wet (HNO3/H2O2) and dry ashed, and then dissolved in 8M HCl. Because of the complex matrix and large sample samples (up to 1500 g), the actinides were preconcentrated from the tissue solution using the TRUTM resin (EIChroM) prior to elemental separation by extraction chromatography and determination of americium, plutonium, uranium and thorium by alpha spectrometry. The actinides were eluted from the preconcentration column and each actinide was individually eluted on TEVATM and TRUTM resin columns in a tandem configuration. Actinide activities were then determined by alpha spectrometry after electrodeposition from a sulfate medium. The method was validated by analyzing human tissue samples previously analyzed for americium, plutonium, uranium and thorium in the United States Transuranium and Uranium Registries (USTUR). Two National Institute of Standards and Technology (NIST) Standard Reference Materials, SRM 4351-Human Lung and SRM 4352-Human Liver were also analyzed.

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Abstract  

Alpha-spectrometric measurements using Si detectors is the standard method for the determination of alpha emitting actinide elements. This method requires the preparation of sources for analysis which do not degrade the energy spectrum of the emitted alpha particles via sample self-absorption. A variety of methods for the electrodeposition of actinides have been reported in the literature, many of which require long deposition times and lack reproducibility. A sulfate based method has been evaluated for the preparation of these sources using chemometric analysis to optimize the method and evaluate several variables and their interactions with the goal to achieve high yield source preparation in 1 hour or less. Typical resolution for this method is 30 keV or less with recoveries approaching unity.

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Abstract  

The dissolution rates for 238U, 230Th, and 231Pa from 8 contaminated soils in simulated lung fluid were determined. The soil samples were provided by the US Army Corps of Engineers and were collected from various areas at their St. Louis, Missouri FUSRAP sites. Each soil was subjected to a 100 day in vitro dissolution experiment, during which the amount of each radionuclide that had dissolved was periodically measured. At the conclusion of the experiment, a plot of the relative amount of radionuclide dissolved vs. time was constructed for each radionuclide in each soil. The dissolution rates for each radionuclide were then determined by fitting multiple first-order exponential functions to each plot. The results of these experiments were then used assign in vitro dissolution rate classifications to each radionuclide in each soil according to ICRP 30 guidelines.

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Abstract  

Plutonium and other actinides were determined in human autopsy tissues of occupationally exposed workers who were registrants of the United States Transuranium and Uranium Registries (USTUR). In this study, Pu was purified and isolated from Am, U and Th, after drying and wet-ashing of the tissues, and the addition of238Pu as a radiotracer. After electrodeposition onto vanadium planchets the239+240Pu activity was determined by alpha-spectrometry. A fission track method was developed to determine239Pu in the presence of238Pu and240Pu, using LexanTM polycarbonate detectors. Combining the two techniques allowed the determination of the240Pu/239Pu activity and atom ratios. Data from selected USTUR cases are presented.

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Summary  

In the analysis of biological samples with sub ng/g uranium concentrations, pre-concentration has been shown to improve the detection limit for the determination of uranium. Recovery corrected kinetic phosphorescence analysis (KPA) combines pre-concentration and separation of uranium by anion-exchange from human tissues dissolved in 6M HCl, with the radiochemical yield determined by alpha-spectrometry, using 232U as a tracer. Total uranium is determined by KPA after correction for chemical recovery. Twenty-one randomly selected dissolved tissue samples from the United States Transuranium and Uranium Registries (USTUR) Case 0242 were chosen for comparative analyses. The set of samples included dissolved bone and soft tissues. Uranium concentrations for seven of the samples had not been previously reported. Direct KPA could not be used to determine uranium concentrations of five unreported tissues. Three of these tissues had uranium concentrations at or below the KPA L Q value of 0.028 ng/ml and two tissues had known matrix interferences. All seven of the unreported tissues were successfully analyzed by recovery corrected KPA; concentrations ranged from 9 to 1380 ng per tissue, including those that could not be analyzed by direct KPA due to matrix problems. Recovery corrected KPA gives results similar to direct KPA where matrix interferences and low detection limits are not encountered. A comparison of the direct method of KPA versus recovery corrected KPA shows marked improvement for the determination of uranium in samples that heretofore either uranium was not detected or the sample had to be drastically diluted to minimize matrix effects in order to measure uranium.

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Abstract  

The paper contains a summary of the recent developments of the prediction part of the NAAPRO (Neutron Activation Analysis PRognosis and Optimization) code. Specific details are given for the activation product yield calculation approach used in the program and for the nuclear data libraries. The prospects for the code development are discussed.

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Abstract  

Capabilities of black poplar-tree (Populus nigra L.) bark as a biomonitor of atmospheric air pollution by chemical elements were tested against epiphytic lichens Xanthoria parietina (L.) and Physcia adscendens (Fr.). Concentrations of 40 macro and trace elements were determined using epicadmium and instrumental NAA. The data obtained were processed using non-parametric tests. A good correlation was found between concentrations of majority of elements in bark and lichens. On the accumulation capability bark turned out to be competitive with both lichens examined. The main inorganic components of black poplar-tree bark were revealed. A substrate influence on the concentrations of some elements in epiphytic lichens was established. An optimized procedure of bark pre-irradiation treatment was suggested.

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Abstract  

More than 2200 atmospheric particulate matter filters were collected from 1995 through 2002 in the Spokane, WA area for the Spokane Air-Filters Project. The samples were sent to the US EPA in Research Triangle Park, NC for energy dispersive X-ray fluorescence (XRF) analysis and then delivered to the Washington State University Nuclear Radiation Center for neutron activation analysis (NAA). There were 28 elements of interest for the NAA portion of the project; however, due to detector efficiencies, background effects, and composition loading on each filter, only 15 of the 28 elements analyzed for produced valid results above the detection limit due to Compton background noise and blank subtraction. The 15 detectable elements with their six year average with associated 95% confidence interval concentrations in ng/m3 are: As (0.384±0.88), K (50.0±194), La (0.051±0.251), Na (61.9±421), Sm (0.00928±0.072), Au (0.00154±0.149), Br (1.06±1.5), Ce (0.164±0.969), Co (0.0399±0.122), Cr (0.479±3.31), Fe (110±227), Sb (0.474±1.64), Sc (0.0197±0.00548), Th (0.011±0.0603), and Zn (12.4±32.6).

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