Radiochemical methods evaluation

Contaminant concentrations Dispersal of airborne contaminants such as odors, fumes, smoke, VOCs, etc. transported by these airflows and transformed by a variety of processes including chemical and radiochemical transformation, adsorption, desorption to building materials, filtration, and deposition to surfaces evolution of contaminant concentrations in the individual zones air quality checks in terms of CO2 levels cross-contamination evaluation of zones air quality evaluations in relation to perception as well as health. Methods ate also applicable to smoke control design. 

The large body of radiochemical data reported on samples from event Small Boy contained a considerable proportion of unreliable results and calibration factors. For successful use of the data to establish the fractionation behavior of fission products in nuclear debris, it was necessary to examine the individual values by all available methods, to discard those which fail to show internal consistency, and to revise the calibrations. The authors of this report have undertaken such an evaluation, and a number of meaningful relationships have already resulted. 

Procedures for the determination of 11 elements in coal—Sb, As, Br, Cd, Cs, Ga, Hg, Rb, Se, U, and Zn—by neutron activation analysis with radiochemical separation are summarized. Separation techniques include direct combustion, distillation, precipitation, ion exchange, and solvent extraction. The evaluation of the radiochemical neutron activation analysis for the determination of mercury in coal used by the Bureau of Mines in its mercury round-robin program is discussed. Neutron activation analysis has played an important role in recent programs to evaluate and test analysis methods and to develop standards for trace elements in coal carried out by the National Bureau of Standards and the Environmental Protection Agency. 

This article presents a comprehensive view of the present state-of-the-art of radiochemical separations for the following trace elements in coal Hg, Rb, Cs, Se, Ga, As, Sb, Br, Zn, Cd, and U. Most of the work on the determination of trace elements in coal is very recent. The accuracy of the analysis methods, nearly all newly developed, has been open to question because of the lack of standards and lack of knowledge of the range of concentrations for many trace elements in coal. Federal government laboratories have taken the lead in evaluating methods of analysis and in developing standards. By a round-... 

O Gorman et al. (19) used radiochemical NAA as a referee method in evaluating the determination of mercury by atomic absorption techniques. A commercial testing laboratory did the neutron activation analyses. 

Weaver and von Lehmden (20), under sponsorship of the EPA, evaluated two instrumental NAA methods and one with radiochemical separation for determining mercury in coal. 

Evaluate Module The functions of this module are to process, integrate, and report radiochemical, UV, and/or MS data. The MS data are best processed using this module, especially when the data are acquired using the stop-flow method. When operating in this mode, the acquired MS profile appears discontinuous. The ARC software is capable of removing the gaps observed during all the ARC stop... 

Finally, it is worth mentioning the first example of a study of the effect of diene on C2-C3 analysis by IR (80). It refers to ethylidene norbornene (ENB), but the procedure is of general applicability. A correction coefficient K on the results obtained through the near-IR method (8) was obtained by analyzing a set of terpolymers with 14C-labelled C2 and subtracting13 from the measured C3 content an amount proportional to the diene concentration. K was evaluated so as to minimize the sum of the squares of the differences (total found —100), where total found stands for the sum C2 (determined by radiochemical analysis) + diene (determined by IR) + C3 (determined by near-IR and suitably corrected for the diene influence). In other words, the expression to minimize is... 

It is not possible within the scope of this collection of methods to deal with the theoretical processes in the interaction of radioactive emitters with matter (e.g. ionization, photo-electric effect, Compton effect, pair creation), the construction and operation of detectors, the structure and circuitry of the measuring equipment, or the electrical evaluation of the signals received. The reader should consult the specialized radiochemical literature. 

All chromatographic methods (liquid, liquid-liquid, liquid-solid, gas, gas-liquid, and gas-solid chromatography) are used in radiochemical analysis of food and environmental samples. Equipment for the evaluation of paper and thin-layer radiochromatograms is commercially available. The radiation detectors used vary according to the type and energy of the radiation emitted by the measured radionuclides. Use is made of ionization chambers, proportional counters, and Geiger-Miiller, scintillation, and semiconductor detectors. 

Iodine. Iodine is an essential trace element, which forms an indispensable part of thyroid hormones. Hence, the constant supply of I via the food chain is necessary. Iodine is determined via the I(n,y) I reaction. A comparative evaluation of INAA and two different methods of RNAA was given by Kucera et al. (2001). In the radiochemical procedures, irradiated samples were digested by alkaline-oxidative fusion to avoid losses of volatile I. According to the first... 

Chemical methods apply to the separation and purification of radioactive substances in the same way they apply to stable substances. A radiochemical separation is judged in terms of both the yield and the purity of the separated material this is particularly important when analyte concentrations are low or contaminant levels are high. Purity and fractional recovery are often evaluated with the tracer technique. Radiochemical and mass spectrometric detection methods are quite sensitive, and it is possible to work with trace amoimts of analyte. However, radiochemical procedures involving the presence of an isotopic carrier (which can also function as a tracer) are often simpler to design than are carrier-free procedures losses from adsorption on vessel walls or suspended particles may negatively affect the recovery of the analyte in a tracer-level sample. 

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