Radionuclide mixtures

The vast majority of groundwater and subsurface media contaminated with radionuclides are at sites associated with DOE facilities. Although numerous site-specific reports exist. It has only been recently that a general study of the levels of contamination at all DOE sites was made by Zachara and Riley ( 3). The major observations of this study are the predominance of organics and radionuclide mixtures at existing DOE waste sites. The most important radionuclides identified, based on frequency of appearance in reported analytical results, were plutonium, americium, uranium, neptunium, and cobalt. 

For some radionuclide mixtures, a group separation, e.g., for actinides, is satisfactory for measuring its component radionuclides by alpha-particle spectral analysis. As discussed in Section 6.4.1, further chemical separation is needed for radionuclides that emit alpha particles of almost the same energies, or even a mass spectrometer for radioisotopes of the same element with almost identical alpha-particle energies such as Pu and Pu. 

Inference of the radionuclide mixture and overall decay rate in submitted samples based on type of sample and prescreening radiation scans of sample... 

Screening in response to emergencies is particularly subject to problems due to the unexpected situation and the possibly unprepared persons who collect and transport samples. In the laboratory, problems can arise due to large differences in radionuclide contents among samples, unexpected radionuclide mixtures, unusual modes of detector operation, and the pressure to report analytical results immediately. Problematic actions that need to be prevented because they adversely affect results include ... 

Table 15.8 Activity limits for excepted packages (except mixtures of radionuclides) ...

The y-energies are characteristic of the nuclear energy levels and transitions. Figure 10.12 shows the appearance of a y-ray spectrum. Such spectra are of immense value in the identification and determination of radionuclides in a radioactive mixture. 

Table 2.1 lists specific radionuclides that may be present in nuclear fuel rods or industrial sources used to construct a dirty bomb. It also lists the radiological half-lives of each radionuclide, whether they are present in fresh or spent fuel rods, and their potential industrial applications. Note that the actual suites of isotopes for given fuel rods will vary depending on the origin and composition of the original fuel mixture. The uranium and plutonium isotopes found in fuel rods may also be found... 

Sebesta et al. describe a method for the separation of Tc and s + issj g adsorption chromatography using a solution of iV-benzoyl-A-phenylhydroxylamine in chloroform sorbed on Chromosorb W DMCS. The mixture of the radionuclides of technetium and rhenium in 5 M HCIO4 is passed through the coliunn. 

Figure 11,8 Composite decay curves for (A) mixtures of independently decaying species, (B) transient equilibrium, (C) secular equilibrium, and (D) nonequilibrium, a composite decay curve b decay curve of longer-lived component (A) and parent radio nuclide (B, C, D) c decay curve of short-lived radionuclide (A) and daughter radionuclide (B, C, D) d daughter radioativity in a pure parent fraction (B, C, D) e total daughter radioactivity in a parent-plus-daughter fraction (B). In all cases, the detection coefficients of the various species are assumed to be identical. From Nuclear and Radiochemistry, G. Friedlander and J. W. Kennedy, Copyright 1956 by John Wiley and Sons. Reprinted by permission of John Wiley and Sons Ltd.

Radioactive Debris in Cows. Nuclear detonations produce a complex mixture of radionuclides that includes both the fission products and those induced by neutron activation. Experiments relating to such events... 

From this example it is apparent that complex experiments can be carried out with relative ease. The mixture of approximately 10 isotopes in these samples has been resolved as to the specific radionuclides and their amounts. 

The system has a specific capability for the resolution of very complex mixtures in which large energy peaks tend to mask small adjacent ones. It is therefore particularly suitable for rigorous studies of the slow incorporation of low levels of radionuclides into biological or environmental systems. It should encourage investigation in these areas, where up to now the accumulation of data has been slow, laborious, and expensive. 

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