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  • Author or Editor: R. Jervis x
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Abstract  

In recognition of the 1997 anniversary of the first century of radiochemistry, a review is made of its unique contribution to the emergence of nuclear science, its development from the use of very basic chemical techniques initially to a battery of more sophisticated procedures, and its changing role as it has become widely applied in many fields of science. Synergistically, these fields have been able to develop with the aid of radiochemistry while at the same time, radiochemical methods developed to meet the demands of such applications. Among these, during the second half of the century, has been radiochemistry applied to quantitative chemical analysis: RAA or, nuclear analytical chemistry, and typical examples of its use in the authors' laboratory are described, including some recent INAA results on development of novel ‘activable’ tracer coding for forensic use with specialized and high security materials. The specific contributions, during the century, of Japanese pioneers in radiochemistry are also cited.

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Abstract  

Nuclear methods of analysis have advanced dramatically in recent years, and in many ways, techniques that once were viewed as a scientific curiosity and the toys of a few scientists working in large nuclear research establishments, are now semi-routine and can be applied even by young students. Large amounts of good analytical data are outputted from instruments having sophisticated embedded software. It is interesting to speculate on the directions that nuclear analytical techniques may take next: whether more multielement; more automation for vastly larger sample suites; extension to minor and major components of samples as well as trace components; coupling of nuclear methods to hyphenated methods. However, in some respects the resources needed to continue to develop and apply radioanalytical methods are on the wane: reactors and accelerators are being closed and fewer radiochemical specialists are being trained. The open question, is whether instrumental analysis techniques will offer more and better results with less effort, or be less equipment intensive? In this paper some personal reflections on nuclear actcivation methods and their trends are presented and discussed. Some mileposts in the development of the field and some unique and interesting applications (as implied by the paper title) are cited and discussed.

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Abstract  

The purpose of this study was to use instrumental neutron activation analysis (INAA) to investigate the effectiveness of oak tree leaves as indicators of atmospheric pollution. Leaves were sampled from several different cities in southwestern Ontario, Canada and tested for 16 different trace elements (U, Dy, Ba, Ti, Sr, I, Br, Mg, Cu, Na, V, K, Al, Mn, Cl and Ca). The results show promise for the use of oak leaves as multielemental environmental monitors due to their apparent ability to reflect the overall pollution levels of the vicinity in which they grow. Oak leaves were found to be superior to both birch and maple leaves for monitoring most of the elements studied.

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Abstract  

Epithermal neutron activation analysis (ENAA) was applied to measure quantitatively Cd and other elements in bone samples from control and Cd-fed rats. This method was found to be non-destructive to the bone samples, with no sign of radiolytic charring and was sensitive enough to detect and quantify Cd in bone samples at normal levels for mammals (viz. 0.5–1.0 g/g) and higher. Two different thermal neutron shield materials were utilized, namely cadmium and boron. The boron shield resulted in a 27% improvement in the detection limit of Cd in bone. The accuracy of ENAA for Cd was assessed by intercomparison with electrothermal atomic absorption spectrophotometry (ETAAS), and the results were in fair agreement (±23%) with those from ENAA.

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Abstract  

Concentrations of 35 elements in Chinese Standard Rocks (GSR-1 to GSR-3) and Soils (GSS-1 to GSS-8) have been measured with INAA using the SLOWPOKE reactor. At the same time, the U. S. NBS reference standards: SRM-1632a (Bituminous Coal), SRM-1633a (Coal Fly Ash) and SRM-1646 (Estuarine Sediment) were also analyzed in order to cross-check the accuracy of this method. The results obtained indicate that the reproducibility of the method is satisfactory for most of the elements, namely the precision in general, is better than ±10%. Comparison of our values for NBS SRM-1632a, 1633a and 1646 with the certified values of NBS or with values cited in the literature indicates good agreement. The results were found to be accurate within ±10% error of the established results.

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Abstract  

The trace metal loading of used car and truck tires and the fractions of the metals volatilized upon incineration of the tire were determined. INAA was chosen due to its multielement analysis capability and its low detection limit for many elements. A high purity planar germanium detector was used. Among the elements measured were, Al (4–150 g/g), Ti (41–730 g/g), V (0.04–0.4g/g), Mg (>80–580 g/g), Zn (1–2.2%) as typical concentrations; also some amounts of antimony, bromine and arsenic have been found. Major differences in elemental concentrations have been observed between the tread and the wall of a tire, and also between different brands.

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Abstract  

Extension of current INAA practice to accommodate large volume samples, of the order of 0.1 to 1 m3, requires consideration of the need for correction factors that are usually negligible for most small sample analyses. Direct INAA of large samples can be advantageous for materials that are not homogeneous such as contaminated soil, industrial raw materials or solid wastes. Large sample INAA can be adapted for the screening of such materials in situations when representative small samples would be difficult or tedious to obtain and analyze. However, appropriatecorrections are required to take into account neutron flux attenuation and gradients within large samples as well as absorption losses of emerging -rays and extended counting geometry. In this work, thermal neutron flux attenuation over several cm within a SLOWPOKE reflector site was measured, using monitors, to amount to 0.84 of incident flux and the quantitative sample self-shielding factors for cylindrical C12H22O11 samples, were modeled within ±3% through adaptation of published values. Gamma-ray attenuation and variation in counting geometry over sample dimensions were experimentally determined and compared to calculated correction factors. Their computation was based on sample-detector geometry and utilized linear -attenuation coefficients of sample matrix and air. Similarly, agreement of large sample SRM's measured concentrations with certified values was within <5%, thus validating the use of these methods and their future extension to large volume sample INAA.

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