Nuclear data environmental samples

The Proton Microprobe. No discussion of ion beam analytical systems would be complete without mention of the ultimate ion beam system— the proton microprobe. As shown in the excellent review articles by Cookson (5) and Martin and Nobiling (19), ion beams can be prepared with dimensions of a micron or so. Such finely focussed ion beams can be supported by the nuclear or atomic analytical methodologies mentioned above, with PIXE being the most widely used. Since the PIXE system s fractional mass sensitivity is not changed by beam area, one can have a 1-ppm measurement made over an area of 10 cm, yielding mass sensitivities of 10" g or so in a nondestructive multiele-mental analysis as shown in Figure 6. No other method exists that can obtain such data, so the role of ion beams is well foimded. Explosive growth of these expensive systems has occurred in the past five years, but the cost has limited applications to most environmental samples. 

In the event of an accident at a nuclear or other facihty, environmental sampling and subsequent measurements should be performed to provide data on the levels, time dependence and spatial distribution of radionuclides in air, soil, plants, foodstuffs and feedstuffs so as to assess doses to critical groups of the population and to support decisions on mitigation and protective actions. Sampling should therefore be representative with regard to the exposure conditions of the critical group (see paras 6.18-6.22). 

The work which is reviewed here provides accurate structural data from micro-wave and radiofrequency spectroscopy of relatively small molecule, hydrogen bonded complexes. Its role has been to provide information concerning the stereochemistry and electronic properties — electric dipole moments and nuclear hyperfine interactions — characteristic of hydrogen bonds. The experiments are done on gas phase samples, often in molecular beams, which eliminates environmental perturbations of the hydrogen bonds. In addition, the small molecules used are amenable to ab initio calculations 7 9) and thus the results are extremely useful as criteria for the accuracy of these calculations. Finally, the results are useful to construct models of more complex systems in chemistry and biology involving hydrogen bonds 4). 

The so-called research survey is an extended ( in-depth ) variant of environmental monitoring however, in real conditions it is most often limited to some extended information survey. The research survey is conducted once every three years and more rarely, as well as before commissioning of a hazardous facility and during elimination of consequences of radiation accidents. Samples are also taken using the principle of surveying nuclear- and radiation-hazardous objects and next comparing the smvey data with some control backgrormd points. 

Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry complement each other mass spectrometry provides molecular weight data, while NMR spectroscopy provides stereochemical information based on the various kinds of protons present in a molecule and their relation to one another. A major advantage of NMR spectroscopy is that the sample is not altered or destroyed. NMR spectroscopy has two major limitations with respect to pesticide residue analyses—it is much less sensitive than mass spectrometry, infrared or ultraviolet spectroscopy, or gas chromatography and moderately pure (95%) compounds are required usually. Since pure materials are required, environmental sam-... 

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