Radioactivity Radionuclides

The purpose of the MCLs for radioactivity (radionuclides) is to limit human exposure. Some waters in contact with radioactive geologic strata (e.g., certain shales) are known to possess radioactivity. Since radioactivity in organisms is cumulative, monitoring should be carried out. 

Gross alpha particle activity, Radium-226 and Radium-288 

Gross alpha particle activity (including Radium-226 but excluding radon and uranium), 15pCiL 1. 

The average annual concentration of beta particle and photon radioactivity from man-made radionuclides in drinking water shall not produce an annual dose equivalent to the total body or any internal organ greater than 4 millirem/yr. Tritium must be less than 20,000 pCi L-1, and strontium must be less than 8 pCi L-1. 

When gross beta particle activity exceeds 50 pCi L radioactive constituents must be identified total body doses must be calculated. 

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Radiation monitoring equipment covers a variety of models designed for a specific purpose. In this section we shall briefly discuss measurement of airborne radioactivity. Radionuclides are released into the atmosphere from operating the various facilities. These radionuclides are dispersed to populated areas where exposure occurs by breathing or swallowing the materials. 

Methods Natural and Artificial Radioactivity Radionuclide Monitoring Radiotracers. Spot Tests. Thin-Layer Chromatography Overview. Titrimetry Oven/iew Potentiometric. X-Ray Fluorescence and Emission X-Ray Fluorescence Theory. 

See also Radiochemical Methods Overview Natural and Artificial Radioactivity Radionuclide Monitoring Food and Environmental Applications. 

See also Air Analysis Sampling. Geochemistry Sediment Soil, Major Inorganic Components Soil, Minor Inorganic Components Soil, Organic Components. Radiochemical Methods Natural and Artificial Radioactivity Radionuclide Monitoring Uranium Radiotracers Gamma-Ray Spectrometry. Water Analysis Freshwater. 

See also Radiochemical Methods Oven/iew Natural and Artificial Radioactivity Radionuclide Monitoring Technetium Radon Uranium Radiotracers Radio-Reagent Methods Radioreceptor Assays Gamma-Ray Spectrometry Food and Environmental Applications. 

A hot cell is a lead shielded locked containment chamber with underpressure, often used for handling highly radioactive radionuclides and products. Hot cells are usually... 

Magill, J. and Galey, J. (2004). Radioactivity, Radionuclides, Radiation (with the Fold-out Karlsruhe Chart of the Nuclides) (Hardcover), Springer-Verlag, Berlin, Germany (a CD-ROM accompanies the book). 

RADIOISOTOPES Isotopes that are radioactive. RADIONUCLIDE A nuclide that is radioactive. RADIOLYSIS The decomposition of material by ionising radiation for example, water into hydrogen and oxygen. 

Decay products of the principal radionuclides used in tracer technology (see Table 1) are not themselves radioactive. Therefore, the primary decomposition events of isotopes in molecules labeled with only one radionuclide / molecule result in unlabeled impurities at a rate proportional to the half-life of the isotope. Eor and H, impurities arising from the decay process are in relatively small amounts. Eor the shorter half-life isotopes the relative amounts of these impurities caused by primary decomposition are larger, but usually not problematic because they are not radioactive and do not interfere with the application of the tracer compounds. Eor multilabeled tritiated compounds the rate of accumulation of labeled impurities owing to tritium decay can be significant. This increases with the number of radioactive atoms per molecule. 

Adsorption of Radionuclides. Other appHcations that depend on physical adsorption include the control of krypton and xenon radionuchdes from nuclear power plants (92). The gases are not captured entirely, but their passage is delayed long enough to allow radioactive decay of the short-hved species. Highly rnicroporous coconut-based activated carbon is used for this service. 

The abundance of a trace element is often too small to be accurately quantihed using conventional analytical methods such as ion chromatography or mass spectrometry. It is possible, however, to precisely determine very low concentrations of a constituent by measuring its radioactive decay properties. In order to understand how U-Th series radionuclides can provide such low-level tracer information, a brief review of the basic principles of radioactive decay and the application of these radionuclides as geochronological tools is useful. " The U-Th decay series together consist of 36 radionuclides that are isotopes (same atomic number, Z, different atomic mass, M) of 10 distinct elements (Figure 1). Some of these are very short-lived (tj j 1 -nd are thus not directly useful as marine tracers. It is the other radioisotopes with half-lives greater than 1 day that are most useful and are the focus of this chapter. 

The radiation dose from being in or near a "cloud" of aiibome radioactivity can be calculated if the radionuclide concentration in the cloud is known. While radioactive noble gases may be inhaled, they are not retained in the body, hence, most of their dose contribution is by cloud radiation. 

Nuclear activation analysis (NAA) is a method for qualitatively and quantitatively detg elemental compn by means of nuclear transmutations. The method involves the irradiation or bombardment of samples with nuclear particles or high-energy electromagnetic radiation for the specific purpose of creating radioactive isotopes from the stable or naturally-occurring elements present. From the numbers, types and quantities of radioactive elements or radionuclides, it is possible to deduce information about the elemental compn of the original sample... 

Radioactive particle tracking (RPT) can be used to map the velocity field by tracking the position of a single radioactive tracer particle in a reactor. The particle which may consist of a polypropylene shell contains a radionuclide that emits y-rays. 

Similar demands for reference materials also arise in connection with the monitoring of radioactivity in and around nuclear installations (nuclear power plants, nuclear fuel and reprocessing plants, and nuclear waste facilities). These, in fact, are now the main applications of radionuclide reference materials. 

Quality assurance of radiopharmaceutical preparation and use is obviously a very important topic because of its direct impact on patient diagnosis, treatment and health (see, e.g. Abreu 1996). Reference materials play only a small - but nevertheless important -role in this process, mainly in the area of calibration of radioactivity-measuring instruments. The materials of interest are all pure chemical containing calibrated activities of selected radionuclides used commonly in nuclear medicine (e.g. Co, Ga, I,... 

Figure 16. Schematic representation of a degassing magma reservoir in a physical steady-state (mass M of magma constant). ( ) and [Ik] denote fluxes and radionuclide Ik concentrations, respectively. Indices 0, L, G, E, I, R, refer to deep undegassed magma (in radioactive equilibrium), degassed lava, gas phase, and erupted, intended, or recycled degassed magma, respectively (after Gauthier and Condomines 1999).

While it is expected that the source rocks for the radionuclides of interest in many environments were deposited more than a million years ago and that the isotopes of uranium would be in a state of radioactive equilibrium, physical fractionation of " U from U during water-rock interaction results in disequilibrium conditions in the fluid phase. This is a result of (1) preferential leaching of " U from damaged sites of the crystal lattice upon alpha decay of U, (2) oxidation of insoluble tetravalent " U to soluble hexavalent " U during alpha decay, and (3) alpha recoil of " Th (and its daughter " U) into the solute phase. If initial ( " U/ U).4 in the waters can be reasonably estimated a priori, the following relationship can be used to establish the time T since deposition,... 

The thermodynamic properties of U-Th series nuclides in solution are important parameters to take into account when explaining the U-Th-Ra mobility in surface environments. They are, however, not the only ones controlling radionuclide fractionations in surface waters and weathering profiles. These fractionations and the resulting radioactive disequilibria are also influenced by the adsorption of radionuclides onto mineral surfaces and their reactions with organic matter, micro-organisms and colloids. 

The role of radionuclides as tracer of the chemical transport in river is also reinforced by the fact that each of the U-Th-Ra elements has several isotopes of very different half-lives belonging to the U-Th radioactive series. Thus, these series permit comparison of the behavior of isotopes of the same element which are supposed to have the same chemical properties, but very different lifetimes. These comparisons should be very helpful in constraining time scales of transport in rivers. This was illustrated by Porcelli et al. (2001) who compared ( " Th/ U) and ( °Th/ U) ratios in Kalix river waters and estimated a transit time for Th of 15 10 days in this watershed. The development of such studies in the future should lead to an important progress in understanding and quantifying of transport parameters in surface waters. This information could be crucial for a correct use of U-series radioactive disequilibria measured in river waters to establish weathering budgets at the scale of a watershed. 

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