Results 1 - 10 of 8237
Results 1 - 10 of 8237. Search took: 0.029 seconds
|Sort by: date | relevance|
[en] Biologically stable 90Y-labelled albumin microspheres (AMS) were developed by optimizing the process of their preparation. Three formulations of 90Y-AMS were initially prepared with high radiolabelling yield but depending on the step when the radionuclide 90Y and DTPA chelator were added, radiolabelled microspheres with different in vitro and in vivo stability were obtained. DTPA was proved as a useful chelating agent that tightly links radionuclide 90Y to albumin. Also, AMS radiolabelled via DTPA during preparation and before microspheres stabilization, showed significant in vitro and in vivo stability ready for the potential use in selective internal radiation therapy. © 2019 Elsevier Ltd
[en] The probabilities of locating peaks with a high relative peak-area uncertainty were determined empirically with nine types of peak-location software used in laboratories engaged in gamma-ray spectrometry measurements. It was found that it is not possible to locate peaks with a probability of 0.95, when they have a relative peak-area uncertainty in excess of 50%. Locating peaks at these relatively high peak-area uncertainties with a probability greater than 0.95 is only possible in the library-driven mode, where the peak positions are supposed a-priori. The deficiencies of the library-driven mode and the possibilities to improve the probabilities of locating peaks are briefly discussed. © 2019 Elsevier Ltd
[en] In this study, a radiation detection system consisting of two cerium doped lanthanum bromide (LaBr_3:Ce) scintillation detectors in a gamma-gamma coincidence configuration has been used to demonstrate the advantages that coincident detection provides relative to a single detector, and the advantages that LaBr_3:Ce detectors provide relative to high purity germanium (HPGe) detectors. Signal to noise ratios of select photopeak pairs for these detectors have been compared to high-purity germanium (HPGe) detectors in both single and coincident detector configurations in order to quantify the performance of each detector configuration. The efficiency and energy resolution of LaBr_3:Ce detectors have been determined and compared to HPGe detectors. Coincident gamma-ray pairs from the radionuclides "1"5"2Eu and "1"3"3Ba have been identified in a sample that is dominated by "1"3"7Cs. Gamma-gamma coincidence successfully reduced the Compton continuum from the large "1"3"7Cs peak, revealed several coincident gamma energies characteristic of these nuclides, and improved the signal-to-noise ratio relative to single detector measurements. LaBr_3:Ce detectors performed at count rates multiple times higher than can be achieved with HPGe detectors. The standard background spectrum consisting of peaks associated with transitions within the LaBr_3:Ce crystal has also been significantly reduced. Finally, it is shown that LaBr_3:Ce detectors have the unique capability to perform gamma-gamma coincidence measurements in very high count rate scenarios, which can potentially benefit nuclear safeguards in situ measurements of spent nuclear fuel.
[en] The Next Generation Safeguard Initiative (NGSI) includes an effort to determine the mass content of fissile isotopes contained within spent fuel through the spectroscopy of high-energy delayed gamma rays. Studies being performed indicate the primary difficulty is the ability to detect the desired signal in the presence of the intense background associated with spent fuel fission products. An enabling technology for this application is high-resolution high-purity germanium (HPGe) detectors capable of operating efficiently in at extremely high count rates. This presentation will describe the prospects of high-rate germanium detectors and delayed-gamma techniques, primarily discussing the efforts to merge these into a unique and viable system for measuring spent fuel
[en] Actinium-225 and "2"1"3Bi have been used successfully in targeted alpha therapy (TAT) in preclinical and clinical research. This paper is a continuation of research activities aiming to expand the availability of "2"2"5Ac. The high energy proton spallation reaction on natural thorium metal target has been utilized to produce millicurie quantities of "2"2"5Ac. The results of sixteen irradiation experiments of Th metal at beam energies between 78 and 200 MeV are summarized in this work. Irradiations have been conducted at Brookhaven National Laboratory (BNL) and Los Alamos National Laboratory (LANL), while target dissolution and processing was carried out at Oak Ridge National Laboratory (ORNL). Excitation functions for actinium and thorium isotopes as well as for some of the fission products are presented. The cross sections for production of "2"2"5Ac range from 3.6 to 16.7 mb in the incident proton energy range of 78 to 192 MeV. Based on these data, production of Curie quantities of 225Ac is possible by irradiating a 5.0 g cm"-"2"2"3"2Th target for 10 days in either BNL or LANL proton irradiation facilities.
[en] In this paper, a modified version of the Direct LSC method to correct for quenching effect was investigated for the determination of bio-originated fuel content in fuel samples produced from multiple biological starting materials. The modified method was found to be accurate in determining the percent bio-originated fuel to within 5% of the actual value for samples with quenching effects ≤43%. Finally, analysis of highly quenched samples was possible when diluted with the exception of one sample with a 100% quenching effect.
[en] Highlights: • MCNP6.1-computed dose conversion coefficients validated against ICRP 74 values. • Surrogate responses characterized for mono-energetic and fission neutron sources. • Responses estimate dose directly or can be re-cast as radiation protection factors. - Abstract: Computational and experimental estimates of radiation protection factor (RPF) values are of significant interest to various defense-related organizations. Values of the operational quantity of ambient dose equivalent were computed, using version 6.1 of the Monte Carlo N-Particle® code (MCNP6.1), for 25 photon energies and 53 neutrons energies. Energy-dependent values for absorbed dose at a 10-mm depth in the 30-cm-diameter ICRU tissue-equivalent sphere, , were estimated using the kerma approximation for photon (MCNP F6:p tally) and neutron (MCNP F6:n tally) radiation fields, and then transformed to fluence-to-ambient dose equivalent conversion coefficients, , using appropriate quality factors, Q, and radiation fluences. MCNP6.1-computed values of were compared with tabulated values from ICRP Publication 74. The published conversion coefficients for photon radiation fields were within the error bounds of all MCNP6.1-calculated values. For neutron fields, the computed and published conversion coefficients agreed within calculated error bounds for neutron energies of 100 keV and above, while responses to neutron fields below 100 keV exhibited the same shape and were consistent with the kerma approximation applied in the computational model. The MCNP6.1 models were then modified to simulate the same radiation fields, but conversion coefficients were calculated in the shielded environment of a surrogate vehicle (steel cube)—in keeping with historical and recent studies—and the ratios of shielded and unshielded vehicle response functions were expressed as energy-dependent RPF values. The MCNP6.1-computed neutron RPF values were compared with two prior experimental studies involving a mono-energetic neutron source and a high-yield, short-duration fission neutron spectrum and found to agree within the uncertainty of the experimentally-measured values. Limitations of the computed RPF values are discussed.
[en] Highlights: • Three iron oxides were synthesized and the performance were compared for arsenic uptake. • Radiotracer studies were done for sorption, kinetics and isotherm studies. • Oxidation state of sorbed arsenic species investigated by solvent extraction method. • Applied successfully to real arsenic contaminated ground waters. • An uptake mechanism was proposed based on the observations. - Abstract: A radiotracer technique was employed to study the sorption of As(III) and As(V) on chemically synthesized iron oxides: magnetite (Fe3O4), goethite (α-FeOOH) and hematite (Fe2O3) by batch equilibration mode. Magnetite and goethite were found to be promising sorbents for arsenic removal and applied to real ground water from West Bengal, India. A solvent extraction method using benzene was applied for the investigation of oxidation state of sorbed arsenic. A sorption mechanism was proposed for interaction of As(III)/As(V) with iron oxides.
[en] Highlights: • Thermal neutron capture cross sections and resonance integrals of 96,102,104Ru. • The cross sections are measured with reference to a55Mn monitor. • Neutrons from an Am–Be neutron source kept inside a concrete bunker is used. • 104Ru data is measured from 105Ru and 105Rh gamma emissions. - Abstract: Thermal neutron capture cross sections and resonance integrals of 96Ru, 102Ru and 104Ru are measured with reference to a 55Mn monitor. The experiments are carried out using the neutrons from an Am–Be neutron source kept inside a concrete bunker. The thermal neutron capture cross sections measured are in good agreement with the evaluations as well as with one of the recent measurements. The resonance integral of 102Ru measured in the present study is in good agreement with older measurements.
[en] Highlights: • Metrology of detecting 226Ra and 228Ra in samples from hydrothermal plumes. • Optimisation of parameters to detect low-levels of 228Ra using γ-ray spectrometry. • Detection limits of 1.5 mBq was achieved using 1-week measurement underground. • Radon emanation was only 0.5%. • Radiopurity of all materials involved were investigated. - Abstract: The radium isotopes 226Ra and 228Ra can provide important data on the dynamics of deep-sea hydrothermal plumes that travel the oceans for decades and have great impact on the ocean chemistry. This study focuses on parameters important for obtaining low detection limits for 228Ra using gamma-ray spectrometry. It is present at mBq-levels in samples collected during the US GEOTRACES 2013 cruise to the Southeast Pacific Ocean.