Spectrometric techniques mass, nuclide

The development of mass spectrometric techniques for nuclide identification using a tandem Van de Graaff accelerator at the University of Rochester Nuclear Structure Laboratory by H. Gove, K. Purser, A. Litherland, and numerous associates has provided an excellent means for the precise measurement of 36C1 concentrations in natural water [43]. Thus far, about 40 groundwater related samples which have been collected and purified chemically by H. Bentley have been analyzed for 36C1 by D. Elmore, H. Bentley, and others using the University of Rochester machine. Some of these samples are listed in Table 2. 

Measurement of U-series disequilibria in MORB presents a considerable analytical challenge. Typical concentrations of normal MORB (NMORB) are variable but are generally in the 50-150 ppb U range and 100-400 ppb Th range. Some depleted MORB have concentrations as low as 8-20 ppb U and Th. The concentrations of °Th, Pa, and Ra in secular equilibrium with these U contents are exceedingly low. For instance, the atomic ratio of U to Ra in secular equilibrium is 2.5 x 10 with a quick rule of thumb being that 50 ng of U corresponds to 20 fg of Ra and 15 fg of Pa. Thus, dissolution of a gram of MORB still requires measurement of fg quantities of these nuclides by any mass spectrometric techniques. 

As discussed above, mass spectrometric techniques are the methods of choice for measurement of nuclides pertinent to this study. They supercede earlier decay-counting techniques because of their ability to detect a much larger fraction of the nuclides of... 

Mass spectrometric techniques play a dominant role for the determination of transuranium elements in bulk samples as well as in microparticles. The radioactive element most frequently investigated by inorganic mass spectrometry is uranium. The determination of the concentrations and the precise isotopic analysis of naturally occurring radioactive elements (e.g. Th and the decay nuclides) by inorganic mass spectrometry as terrestrial... 

Besides the analysis of nuclear fuel and of radioactive waste materials, the determination of contamination and enrichment of selected radioactive nuclides, e.g., which is one of the most important environmental indicators of nuclear accidents, Se, Tc, Np, Pu, °Pu and "Am at ultratrace concentration levels, is useful for environmental monitoring of fallout from nuclear weapons testing, nuclear power plants or nuclear accidents. ". Selected application fields for the determination of natural and artificial long-lived radionuclides (LLR) and radionuclides investigated by mass spectrometric techniques are summarized in Tables 9.36 and 9.37, respectively. 

Activities of U-series nuclides in MORBs have been determined by both nuclear particle counting and mass-spectrometric techniques. In this section, we highlight briefly the key... 

During the last 25 years, a large number of radioactive species has been discovered. One of the prime objectives of nuclear chemists has been to assign the atomic number and the mass number to the nuclides which are responsible for observed activities. In general, the atomic number is found by chemical analysis, whereas the mass assignment is most unambiguously obtained by methods involving mass spectrometric techniques. 

The obvious method of determining the half-life of a radioactive sample is to measure the change in activity of the sample in successive intervals of time. Another satisfactory procedure is to measure the disappearance of a radioactive parent nuclide or the growth of a daughter nuclide using mass spectrometric techniques. In the former method, emitted particles are counted, whereas, the latter method measures directly the decrease in the amount of the parent isotope, or the increase in the amount of the... 

Probably the most comprehensive published assay of DU used in armor pen-etrators was reported on the basis of analysis of an unfired CHARM-3 penetrator (Trueman et al. 2004). A sample from the penetrator was dissolved in 9 M HCl, spiked with U as a yield monitor, and the uranium was separated from impurities on an ion-exchange resin. The isotopic composition of uranium was determined by mass spectrometric techniques. Actinides ( - Am and Np) were determined in the uranium-free solution by gamma spectrometry and 239+24opy and Pu were measured by alpha spectrometry and their presence was confirmed by ICPMS. Technetium-99 was determined by ICPMS when rhenium was used as a carrier and interferences from iron were eliminated by precipitating with ammonia while ruthenium and molybdenum were removed by separation on a chromatographic resin. The content of these radioactive nuclides is summarized in Table 2.7. 

Prospects for further improvements in sensitivity and precision of mass spectrometric measurements of these nuclides require improvements in either ionization efficiency or transmission efficiency or both. For TIMS methods, the possibility exists for increasing ionization efficiencies using different loading techniques. In addition, small but significant increases in transmission efficiency could plausibly be obtained with improved TIMS instruments, perhaps including the Finnigan TRITON. For ICP-MS... 

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