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- Author or Editor: P. Levy x
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Abstract
The thermal decomposition kinetics of irradiated and unirradiated ammonium perchlorate and ammonium perchlorate powder-aluminum particle mixtures has been studied by determining decomposition gas pressurevs. heating time with samples at a controlled temperature Qualitatively the radiation induced changes are similar to those obtained in previous studies on ‘pure’ ammonium perchlorate. The induction period is shortened and the acceleratory and decay period rate constants are increased. The data have been analyzed using Avrami-Erofeev kinetics. The results for pure unirradiated material are in accord with published results. The activation energies for the induction, acceleratory and decay periods for pure pellets were found to be 133.5±6.7, 131.8±6.7 and 127.2±6.7 kJ·mol, respectively. Samples were exposed to either a single gamma-ray irradiation, fission neutron irradiation followed by a gamma-ray irradiation, or to a proton irradiation. When compared on an equal energy deposited basis, the fast neutron induced changes are appreciably larger than the gamma-ray changes. However, the proton induced changes are comparable or slightly more than the gamma-ray effects. Some, or all, of the fast neutron effects can be attributable to the concentrated radiation damage ‘spikes’ along the path of lattice atom recoils. It is likely that these become thermal decomposition sites when the crystals are heated. Protons create fewer spikes than fast neutrons. Overall, the results indicate that any ammonium perchlorate-aluminum propellant mixtures that may be exposed to radiation environments, such as used in this study, should be subjected to a thorough radiation effects analysis if reliable performance is required.
Summary
An underground laboratory for low-level gamma- and beta-spectrometry has been constructed at IAEA-MEL, Monaco, for the analysis of environmental radionuclides. The laboratory is situated at a depth of 35 m water equivalent underground and equipped with 4, large volume HPGe detectors placed in a common lead shield with anti-cosmic plastic scintillator shielding. There is also an anti-Compton gamma-spectrometer, comprized of an HPGe detector and NaI(Tl) shielding, and finally, a Quantulus liquid scintillation spectrometer. The performance of the gamma-spectrometers with different shielding settings/adjustments are discussed, as well as their possible applications in the analysis of natural and anthropogenic radionuclides in the marine environment.
Low viscosity in cereals is important for monogastric livestock feeding. With respect to triticale, knowledge on the variability of its viscosity and its environmental dependence is deplorably low. Six winter varieties with similar earliness at maturity were chosen that covered a large range of potential applied viscosity (PAV) (individual values ranging from 1.8 to 4.9 ml/g). These were cultivated in four locations in Switzerland, at altitudes ranging between 430 and 700 m a.s.l., in 2008 and 2009. The effect of genotype on the PAV was significant and clearly influenced by the location factor. Although variety × location and variety × year interactions were rather low, they were still very important for the PAV compared with other variables such as grain yield and specific grain weight. The PAV expression of one variety seemed not to be susceptible to environmental conditions. The varietal range in viscosity demonstrates a high potential for breeding to raise quality, especially as the viscosity and the grain yield were not correlated. The favourable relationship between the PAV and protein content found in the present study may provide a further incentive to improve this trait to yield high-quality triticale. Existing variability might be used to guide the choice of favourable varieties.
Abstract
The development of radioanalytical methods for low level radionuclides in marine environmental samples is presented. In particular, emphasis is placed on the introduction of extraction chromatography (EC) as a tool for improving the quality of results as well as reducing the analysis time. However, the advantageous application of EC often depends on the effective use of suitable preconcentration techniques, such as co-precipitation, to reduce the amount of matrix components which accompany the analytes of interest. On-going investigations in this field relevant to the determination of environmental levels of actinides, 137Cs and 90Sr are discussed.
Summary
A procedure is described to extend the current radiochemical method of seawater analysis for Pu and Am including Np. Short-lived 239Np tracer was prepared by separation from its 243Am parent. Irish Sea Water reference material (IAEA-381) containing known concentrations of 237Np, Pu isotopes and 241Am was used to test the procedure for small water volumes. Inductively-coupled plasma mass spectrometry (ICP-MS) was used in addition to alpha spectrometry for measurement of 237Np in the purified final Np fractions.
Abstract
A reference material designed for the determination of anthropogenic and natural radionuclides in sediment, IAEA-384 (Fangataufa Lagoon sediment), is described and the results of certification are presented. The material has been certified for 8 radionuclides (40K, 60Co, 155Eu, 230Th, 238U, 238Pu, 239+240Pu and 241Am). Information values are given for 12 radionuclides (90Sr, 137Cs, 210Pb (210Po), 226Ra, 228Ra, 232Th, 234U, 235U, 239Pu, 240Pu and 241Pu). Less reported radionuclides include 228Th, 236U, 239Np and 242Pu. The reference material may be used for quality management of radioanalytical laboratories engaged in the analysis of radionuclides in the environment, as well as for the development and validation of analytical methods and for training purposes. The material is available from IAEA in 100 g units.
