Activation analysis gamma spectrometry

As seen in the specific examples given later, numerous analytical methods are used for the determination of uranium in environmental samples. The most popular among them are ICPMS and alpha spectrometry, but neutron activation analysis, gamma spectrometry, and XRF are often deployed and even simple spectrophoto-metric (like colorimetric aresnazo-III) techniques are sometimes still used. For the precise determination of total uranium and its isotopic composition, isotope dilution (ID) methods can be used. One example is a comparison of ID-TIMS and ID-SIMS for isotope ratios in soil standards where two separation and preconcentration chromatographic techniques were also compared (Adriaens et al. 1992). 

The uranium content in soil can be determined directly by some analytical methods that are mainly based on nuclear techniques (variations of neutron activation analysis, gamma spectrometry, x-ray fluorescence, or laser-ablation ICPMS), but the common, popular, and more accurate methods require digestion and dissolution of the entire soil sample or at least rely on leaching the uranium out of the sample matrix. In principle, the methods used for assaying uranium in minerals (see Chapter 2) are also suitable for soil characterization, but uranium is usually present in the latter only as a low-level impurity, usually below 100 pg U g. We shall first overview the procedures deployed for the treatment of soil samples prior to analysis and refer to the analytical devices used for the measuranent of the uranium content and isotopic composition in these studies. 

Analytical methods for quantifying americium in environmental samples are summarized in Table 7-2. The methods that are commonly used in the analysis of americium based on activity are gross a analysis, a-spectrometry and gamma-ray spectrometry. MS detection techniques are used to measure the mass of americium in environmental samples. (The mass-activity conversion factor for 241Am is 0.29 (lCi/ lg or 3.43 ig/ p,Ci [Harvey etal. 1993]). 

Asaro, F., Applied Gamma-Ray Spectrometry and Neutron Activation Analysis, Proceedings of the XX. Colloquium Spec-troscopicum Internationale and 7. International Conference on Atomic Spectroscopy Praha 1977 Invited Lectures II, 413-426. 

Other frequently used methods for determining fluoride include ion and gas chromatography [150,204,205] and aluminium monofluoride (AIF) molecular absorption spectrometry [206,207]. Less frequently employed methods include enzymatic [208], catalytic [209], polarographic [210] and voltammetric methods [211], helium microwave-induced [212] or inductively coupled plasma atomic emission spectrometry [213], electrothermal atomic absorption spectrometry [214], inductively coupled plasma-mass spectrometry [215], radioactivation [216], proton-induced gamma emission [217], near-infrared spectroscopy [218] and neutron activation analysis [219]. 

The post-bombardment processing of the activated sample may follow either a nondestructive assay of the radioactivity in the sample (gamma-ray scintillation spectrometry is used most often for this) or a chemical processing of the sample prior to the radioactivity assay. Techniques involving either precipitation, electrodeposition. solvent extraction, and ion exchange or some combination of these form the basts of the radio-chemical separation techniques used in activation analysis. 

The recent general availability of solid state Ge(Li) gamma-ray detectors has made possible new applications of activation analysis to multielement trace analysis. A simplified schematic representation of a Ge(Li) detector is given in Fig. 6. The principal advantage of these detectors is their excellent energy resolution for gamma-ray spectrometry 52>. While a typical 3 X 3" NaI(Tl) scintillation crystal may have a photopeak resolution of 50 KeV fwhm (/ull width at Aalf maximum) for the 137Cs... 

Voighl, A. F., D. E. Becknell, and Sr. L. Menapace Comparison of Solid State and Scintillation Gamma-Ray Spectrometry in Analysis. The 1968 International Conference Modern Trends in Activation Analysis, Gaithersburg, Maryland, October 7—11, 1968, Paper 106. 

Perkins, R. W., and D. E. Robertson Selective and Sensitive Analysis of Activation Products by Multidimensional Gamma-Ray Spectrometry. Modern Trends in Activation Analysis-Proceedings of the 1965 International Conference in College Station, Texas, April, 1965. A and M College of Texas, College Station, Texas, pp. 48—57 (1965). 

A wide variety of solvents, reagents, and structural materials encountered normally in the trace-element analysis of seawater have been analyzed for trace-element impurities by neutron activation analysis and gamma (y)-ray spectrometry.17 Some of the results obtained for 10 trace elements are shown in Table 6.4 and indicate that many substances contain high impurity levels of various elements. Particular note should be made of the high concentrations of zinc in... 

Of the five stable Isotopes of zinc, only three ( Zn, Zn, and Zn) can be measured with (delayed gamma) Neutron Activation Analysis and hlgh-resolutlon gamma spectrometry. The required methodology for the measurement of Zn is the most stringent of the three isotopes and the necessary Radiochemical Neutron Activation Analysis has been developed and described in detail elsewhere (.8), The salient features of neutron activation of these three Isotopes are tabulated in Table li and from these, two points emerge First, with the availahility of thermal neutron... 

Nondestructive method (EMAA instrumental neutron activation analysis) based on the measurement of radioactivity of samples analyzed by high-resolution gamma spectrometry using the differentials of the rate of decay of the radionuclides analyzed in time [15]. NAA has several important advantages [15] ... 

NAA is preferred for the analysis of unique samples such as meteorite, the certification of reference materials, and quality assurance in analytical chemistry [21]. Definitive methods are based on the activation of samples, selective separation of analyzed radionuclides by column (ion-exchange) chromatography, and measurement by gamma spectrometry [15, 16, 19]. In definitive methods, radiochemical separation, co-precipitation, extraction, and ionic exchange guarantee the... 

Gamma-ray spectrometry is a probe of nudear rather than chemical processes, but its high specificity and sensitivity have applications in analysis of materials (286). It is especially suited for activation analysis. Unstable nudides produced by nudear bombardment can be identified by their characteristic gamma-ray decay emissions. An important example is slow neutron capture by nitrogen with subsequent decay of 15 detected from its 1.7—10.8 MeV gamma lines, a signature useful for remote, nondestmctive detection of possible hidden explosives (see Explosives and propet. t.ents). Gamma-ray... 

The most obvious application of this method is in waste characterisation associated with nuclear decommissioning, where activated concrete bioshields are a potential source of activity. A core from a bioshield has been analysed using gamma spectrometry, analysis and determination. The core used was too old for any " Ca to be detected, but... 

Non-Destructive Analysis Analytical Method Neutron activation analysis (NAA) Gamma-ray spectrometry X-ray fluorescence spectrometry Conductivity and pH... 

EPA (1999) Determination of metals in ambient particulate matter using neutron activation analysis (NAA) gamma spectrometry. In Compendium of methods for the determination of inorganic compounds in ambient air (EPA/625/R-96/ 010a). Compendium Method 10-3.7. Center for Environmental Research Information, Office of Research and Development, U S Environmental Protection Agency, Cincinnati. 

Prompt gamma-activation analysis and neutron activation-mass spectrometry techniques have been developed that can accurately measure boron in biomaterials (Anderson et al. 1990, 1994). One major... 

TNPGNAA thermal neutron prompt gamma neutron activation analysis TOF-MS time of flight mass spectrometry toxicokinetics study of the quantitative action of a poison in an organism over a period of time, especially the processes of absorption, distribution, biotrans formation and excretion... 

A number of investigators have used Nal(Tl) spectrometry after radiochemical separation to determine several elements in petroleum. Ordogh, et determined I, Br and V in Hungarian crudes by a nondestructive technique, and Palmai used a similar method to determine V, Na, Mn, and Al in products from refinig of crudes. Several Russian papers report the use of nondestructive activation analysis and Nal(Tl) gamma-ray spectrometry for such trace elements as V, Ni, Cu. Co and Na. Mast, et al. and Arroyo and Brune have used nondestructive techniques for the determination of V in crude oils. 

This method involves bombarding the sample with neutrons and measuring the radioactivity induced in the sample (commonly using gamma-ray spectrometry). In order to understand the principles of neutron activation analysis, some pertinent properties of neutrons and their interactions with matter will first be discussed. 

Note 6. Combining the inequality constraint 0] with known Internal Poisson variance has been used by Guinn for total variance estimation in activation analysis ( 2), by Donahue (88) for the same purpose in accelerator mass spectrometry, by Heydorn (18.89) for the analysis of precision of gamma ray spectrum analysis, and by Currie ( ) for optimal weighting in counting experiments. The variance weighted t approximation derives from work by Cochran (90). Cochran s work, however, applied to a somewhat different model than used here. The statistical properties of this extension of his technique have not been studied. 

Activation Analysis and gamma-ray spectrometry (J.P. Op de Beeck F. Reichel)... 

---