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Abstract  

Whole-body ashes from nine cremated adult humans were acquired from local mortuaries in Ft. Collins, Colorado (USA) with the consent of next of kin. Ashes of each individual corpse were ground, homogenized and sealed in a steel can for 30 days before gamma-spectroscopy measurements were made to determine the 228Ra, 228Th, 238U, 226Ra and 40K contents. The median values of radionuclide contents in our study subjects were generally higher than literature values in which only a selected set of organs had been analyzed. Direct estimates of natural or man-made radionuclides in whole-body human ashes should be more accurate than estimates based on analysis of small bone or tissue samples that require extrapolation to the entire body.

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Abstract  

Environmental material was analyzed using conventional gamma spectroscopy and low energy photon spectroscopy after high energy bremsstrahlung activation. Ni, Cu, Zn, As, Se, Mo, Ag, Cd, Sn, Hg, Tl, Pb and U have determined in the concentration range from 0.01 to some 1000 μg/g. In no case was a chemical separation required. Most of the above listed elements were analyzed with a planar intrinsic germanium diode measuring the low energy range of the emitted photon spectrum. Advantages and drawbacks of this method are discussed. Some results of parallel determinations with other activation methods are also presented; they generally are in good agreement with the concentration data obtained by the method described.

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Abstract  

Soil samples were collected at the site of a 1951 leak from an underground storage tank of 6.7 liter of an aqueous solution of irradiated uranium. Laboratory simulations were conducted using irradiated and non-irradiated natural uranium metal, dissolved in acidic aqueous solutions and added to soil columns. Contaminant transport experiments were conducted for a period of 12 to 14 months, followed by sample analysis employing gamma-spectroscopy, neutron activation analysis and liquid scintillation counting. The concentration distributions of U, Cs and Sr found from the experiments were used to derive diffusion coefficients. The measured diffusion coefficients from the field samples were: for 137Cs, 3.0E-04 cm2·s−1; for 238U, 1.8E-09 cm2·s−1; and for 90Sr, 2.6E-09 cm2·s−1. Corresponding values for the laboratory simulations were 5E-06, 3E-05 and 1.9E-05 cm2·s−1, respectively.

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Summary  

The fission of highly enriched uranium (HEU) by thermal neutrons creates dozens of isotopic products. The Isotope and Nuclear Chemistry Group participates in programs that involve analysis of “fresh' fission products by beta counting following radiochemical separations. This is a laborious and time-consuming process that can take several days to generate results. Gamma-spectroscopy can provide a more immediate path to isotopic activities, however, short-lived, high-yield isotopes can swamp a gamma-spectrum, making difficult the identification and quantification of isotopes on the wings and valley of the fission yield curve. The gamma-spectrum of a sample of newly produced fission products is dominated by the many emissions of a very few high-yield isotopes. Specifically, 132Te (T1/2 = 3.2 d), its daughter, 132I (T1/2 = 2.28 h), 140Ba (T1/2 = 12.75 d), and its daughter 140La (T1/2 = 1.68 d) emit at least 18 gamma-rays above 100 keV that are greater than 5& abundance. Additionally, the 1596 keV emission from 140La imposes a Compton background that hinders the detection of isotopes that are neither subject to matrix dependent fractionation nor gaseous or volatile precursors. Some of these isotopes of interest are 111Ag, 115Cd, and the rare earths, 153Sm, 154Eu, 156Eu, and 160Tb. C-INC has performed an HEU irradiation and also “cold' carrier analyses by ICP-AES to determine methods for rapid and reliable separations that may be used to detect and quantify low-yield fission products by gamma-spectroscopy. Results and progress are presented.

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Abstract  

Determination of tree ring chemistry using Neutron Activation Analysis (NAA) is part of an ongoing research between Penn State University (PSU) and Cornell University, The Malcolm and Carolyn Wiener Laboratory for Aegean and Near Eastern Dendrochronology. Tree-ring chemistry yields valuable data for environmental event signatures. These signatures are a complex function of elemental concentration. To be certain about concentration of signature elements, it is necessary to perform the measurements and corrections with the lowest error and maximum accuracy possible. Accurate and precise values of energy dependent neutron flux at dry irradiation tubes and detector efficiency for tree ring sample are calculated for Penn State Breazeale Reactor (PSBR). For the calculation of energy dependent and self shielding corrected neutron flux, detailed model of the TRIGA Mark III reactor at PSU with updated fuel compositions was prepared using the MCNP utility for reactor evolution (MURE) libraries. Dry irradiation tube, sample holder and sample were also included in the model. The thermal flux self-shielding correction factors due to the sample holder and sample for were calculated and verified with previously published values. The Geant-4 model of the gamma spectroscopy system, developed at Radiation Science and Engineering Center (RSEC), was improved and absolute detector efficiency for tree-ring samples was calculated.

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Abstract  

This contribution compares measured neutron energy spectra and neutron fluence rates in the LVR-15 reactor core fully equipped with IRT2M nuclear fuel (enrichment 36% of 235U in the form of UO2) and then with a partially replaced core equipped with three IRT4M nuclear fuel assemblies (enrichment 19.7%). The measurements were performed in the LVR-15 reactor at Research Center Rez Ltd. in the Czech Republic, and were related to a planned transition to low-enriched nuclear fuel within the scope of the RERTR programme. An activation method was chosen for the neutron spectrum measurement. Iron, cobalt, nickel, copper, titanium, iridium and niobium foils were irradiated at four positions near the replaced fuel assemblies. Reaction rates for observed reaction channels were determined using gamma spectroscopy. Reaction rates along the height of the reactor core at the same positions were determined using iron, nickel, and cobalt foils. The SAND-II and STAYNL computer programs were used for neutron spectrum adjustment, and input approximation for both programs was calculated using MCNPX (v2.6). The results include a comparison of theoretical and measured data. Differences were found between thermal neutron fluence rates inside IRT2M fuel assemblies and IRT4M fuel. This difference was predicted by preliminary calculations, but it becomes less significant as distance from fuel assemblies increases.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Craig Aalseth, Erica Andreotti, Dirk Arnold, Joan-Albert Cabeza, Detlev Degering, Andrea Giuliani, Raquel de Orduña, Rodolfo Gurriaran, Mikael Hult, Martin Keillor, Matthias Laubenstein, Gilbert le Petit, Romul Margineanu, Murray Matthews, Harry Miley, Iolanda Osvath, Monica Pellicciari, Wolfango Plastino, Hardy Simgen, Marc Weber, and Robert Werzi

Abstract  

Aerosol samples collected on filter media were analyzed using HPGe detectors employing varying background-reduction techniques in order to experimentally evaluate the opportunity to apply ultra-low background measurement methods to samples collected, for instance, by the Comprehensive Test Ban Treaty International Monitoring System (IMS). In this way, realistic estimates of the impact of low-background methodology on the sensitivity obtained in systems such as the IMS were assessed. The current detectability requirement of stations in the IMS is 30 μBq/m3 of air for 140Ba, which would imply ~106 fissions per daily sample. Importantly, this is for a fresh aerosol filter. One week of decay reduces the intrinsic background from radon daughters in the sample allowing much higher sensitivity measurement of relevant isotopes, including 131I. An experiment was conducted in which decayed filter samples were measured at a variety of underground locations using Ultra-Low Background (ULB) gamma spectroscopy technology. The impacts of the decay and ULB are discussed.

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Abstract  

A study was initiated to investigate the chronological deposition of uranium in certain species of trees growing on the site of a former uranium metal processing facility. The Feed Materials Production Center (FMPC) is located in Fernald, Ohio, and for roughly 40 years operated as a large scale uranium processing center. Core samples from several species of trees growing in different locations throughout the site were extracted using a 12.5 mm incremental wood boring drill bit. After extraction, each core sample was cut and packaged into individual sections representing 4 annual growth rings and submitted for instrumental neutron activation analysis (INAA). The reaction 235U(n,f)140Ba→140La+γ was evaluated using high resolution germanium gamma-spectroscopy to detect the 1.596 MeV photon emission from the fission product 140La following a minimum of a 3 week decay. A total of 106 samples representing 7 individual trees of 3 unique species were irradiated. In addition to the tree-core samples, 18 quality control (QC) samples and 18 standard reference material (SRM) Fly Ash samples were irradiated with the core samples for determining neutron flux. The activity in any one sample in a batch was determined by comparison with the amount of natural uranium in the QC standards. No significantly measurable amount of uranium was detected in any of the tree core samples, although 3 tree core samples were in excess of the minimum detectable amount (30 ng).

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Martin Keillor, Craig Aalseth, Anthony Day, James Fast, Eric Hoppe, Brian Hyronimus, Todd Hossbach, Harry Miley, Allen Seifert, and Glen Warren

Abstract  

Physics experiments, environmental surveillance, and treaty verification techniques continue to require increased sensitivity for detecting and quantifying radionuclides of interest. This can be done by detecting a greater fraction of gamma emissions from a sample (higher detection efficiency) and reducing instrument backgrounds. A current effort for increased sensitivity in high resolution gamma spectroscopy will produce an intrinsic germanium (HPGe) array designed for high detection efficiency, ultra-low-background performance, and useful coincidence efficiencies. The system design is optimized to accommodate filter paper samples, e.g. samples collected by the Radionuclide Aerosol Sampler/Analyzer (RASA). The system will provide high sensitivity for weak collections on atmospheric filter samples, as well as offering the potential to gather additional information from more active filters using gamma cascade coincidence detection. The current effort is constructing an ultra-low-background HPGe crystal array consisting of two vacuum cryostats, each housing a hexagonal array of 7 crystals on the order of 70% relative efficiency per crystal. Traditional methods for constructing ultra-low-background detectors are used, including use of materials known to be low in radioactive contaminants, use of ultra pure reagents, clean room assembly, etc. The cryostat will be constructed mainly from copper electroformed into near-final geometry at PNNL. Details of the detector design, simulation of efficiency and coincidence performance, HPGe crystal testing, and progress on cryostat construction are presented.

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Summary  

In 1951, 6.7 liter of an aqueous solution of actinides, fission and daughter products leaked from an underground storage tank into prairie soil. In 2001, soil samples were collected from the site to determine the degree and extent of the contamination. This paper reports on the continuation of complementary analytical techniques used to determine the concentrations of the contaminants in the soil samples, including gamma-ray spectroscopy, neutron activation analysis (NAA) and liquid scintillation counting (LSC). Gamma-ray spectroscopy was able to identify and quantify the presence of 137Cs, while the activities of the actinides and remaining fission and daughter products were too low to be measured. Concentrations of 137Cs as low as 0.15 Bq/g and as high as 341 Bq/g were measured. NAA was successful in detecting 238U. Only preliminary LSC analysis has been conducted, resulting in gross beta-counts for the soil samples. Finally, correlations were developed between borehole gamma logging values and corresponding concentrations of 137Cs determined by gamma-spectroscopy and gross beta-counts from LSC analysis.

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