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- Author or Editor: C. Thomas x
- Chemistry and Chemical Engineering x
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Abstract
An investigation of the potentials of neutron activation analysis for the routine analysis of trace elements present in atmospheric pollutants is discussed. Various techniques including sequential air sampling, multiple neutron irradiation, high resolution γ-ray spectrometry, chemical isolation, high flux neutron irradiation and X-ray spectrometry have been employed to determine the levels of Pb, Al, V, I, Cl, Mn, Cu, Br, Na, La, Mo, Au, Cr, Fe, Ni, Se, Zn, Ag and Co in atmospheric pollutants. The results of the analysis of nearly two hundred samples collected from the Buffalo New York area during 1968–1969 are reported.
Abstract
Highly specific neutron activation analysis procedures involving post irradiation chemical separations were developed for the determination of Cu, Hg, Zn, Cd, As, Se and Cr in fish tissues. The procedures developed were used to determine the levels of these biologically active elements in some of the commercially important fish species of Lake Erie. The nuclear analytical procedures developed generally involved the irradiation of fish tissues followed by wet-ashing in the presence of nonradioactive carriers From the homogeneous solution of the tissue digest, the elements of interest were chemically isolated and the radio-activities were measured by scintillation gamma ray spectrometry. The results reported include both the determination of the precision and accuracies of each of these elemental analyses and a survey of these seven elements in nine major fish species of Lake Erie.
Abstract
A unique application of forensic neutron activation analysis involving the analysis of trace levels of tungsten, cobalt and tantalum was presented as evidence in a murder trial. The evidence materials analyzed included the blous of the victim, bed sheets, a pair of pantyhose used in strangulation, head and public hair from the suspect, and several samples of raw materials used at a factory where the suspect was employed. The stalned areas of the fabrics analyzed showed trace levels of cobalt, tantalum, and tungsten which were not present in the fabric mattrices. The occupation of the suspect exposed him to fine dust particulates containing these trace elements. Although eyewitness accounts indicated that the suspect was in the neighborhood, there was, however, no evidence other that the neutron activation analysis results to indicate the probable presence of the suspect at the scence of the crime. A jury trial accepting neutron activation analysis findings resulted in a conviction.
The behaviour of the system PbO-PbSO4 was studied between 400 and 900°. Three basic sulphates could be identified by X-ray diffractometry namely: PbO · ·PbSO4; 2 PbO·PbSO4 and 4 PbO·PbSO4.
Abstract
Three different methods for determining the long-lived radionuclide contents of highly neutron activated metal wastes are being compared and assessed using samples of pressurized-water reactor (PWR) and boiling-water reactor (BWR) spent fuel disassembly hardware and control rods. These methods include: 1) empirical analyses involving sampling and laboratory measurements; 2) direct assay techniques; 3) calculation methods. These techniques are discussed and the results of the comparisons made to date are presented. The agreement between empirical versus calculational methods for the disassembly hardware was generally within 10% to 50%, and rarely exceeded a factor of 2.5, especially near the fueled region of the reactor core. However, large discrepancies between the measured versus calculated concentrations were observed for59Ni and63Ni at the end fittings of the fuel assembly hardware, where the calculations underestimated the concentrations by factors varying from about 8 to 28. The calculation errors are believed to be due to inadequate cross section data for the nickel isotopes.
Abstract
An accurate means of determining bone age is a goal for forensic scientists. In this study, thermogravimetric analysis (TGA) has been used to examine pig bone specimens of different post-mortem age. Analysis of bone in both air and nitrogen atmospheres reveals a decrease in total mass loss as the bones age. Two mass loss steps due to the decomposition of the organic bone components were observed and show decreasing trends with age for decomposition in an air atmosphere. In a nitrogen atmosphere the decomposition was observed to be more complex and age dependence of the mass loss for each step was not identified. The TGA data, however, demonstrates the potential of the technique as a means of estimating post-mortem age of forensic bone specimens.
Abstract
An International Monitoring System (IMS) is being created to monitor the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Radionuclide aerosols will be monitored to provide positive proof of an atmospheric explosion. In addition, a group of laboratories will perform quality assurance and confirmatory analyses of samples of interest. The field and laboratory systems will perform gamma-ray spectrometric analysis of air filters. While laboratories may undertake additional analysis such as chemical separation and beta counting, the scope of the work reported here is to make evaluations with respect only to gamma-ray spectrometry. Activation products have not been completely considered and are shaded with uncertainty, from the probability of escape from an underground test and the dependence on the sub-surface elemental composition.
Abstract
Analytical procedures for measuring various radionuclides in the238U and232Th chains in briney waters are described. Using methods such as mass spectrometry, and alpha, beta and gamma spectrometry, the desired measurement sensitivity required for each of the radionuclides is achieved.233U,228Th,208Po,212Pb, and133Ba are used as tracers for chemical yield recoveries. Typical precision of the results range from 5–20%.
Abstract
NiMoO4 obtained by calcination of precursors has been shown to be a very effective catalyst for oxidative dehydrogenation of propane into propene. Preparation conditions and thermal decomposition of two precursors have been studied by TG-DTA, HTXRD, FFT-IR, and thermo-desorption coupled to mass spectroscopy in order to determine their composition and to define the best treatment to favour the oxidative dehydrogenation process. The selectivity and activity for propane transformation into propene are very different depending on the nature of the precursor and of the active phases obtained after thermal activation. The more selective high-temperature β phase of NiMoO4 has been obtained at a lower temperature (500°C) than previously reported (700°C).
Abstract
Three different spent control rods were obtained for direct-assay measurements and empirical sampling and analysis. They were: 1) a BWR cruciform control rod, 2) a PWR rod-cluster control assembly, and 3) a burnable poison-rod assembly. The dominant activity of the BWR cruciform control rod and the PWR burnable poison-rod assembly is60Co, whereas the PWR rod-cluster control assembly is dominated not only by60Co, but also by108mAg and110mAg, which are found in the Ag–In–Cd alloy of the absorber rods. The radionuclide inventories calculated for the three spent control rods from the empirical sampling data agree very well with data determined from the two direct assay methodologies. The concentration of108mAg in the rod-cluster control assembly will have to be considered when these types of spent control rods are prepared for waste disposal.
