Radionuclides short-lived

Because the short-lived nuclides are extinct, a different approach must be taken to use them as chronometers. Equation (8.9) cannot be used to calculate a date because the number of parent nuclides, N, is zero and the equation is undefined. However, if a short-lived nuclide was homogeneously distributed throughout a system, then one can determine the order in which objects formed within that system based on the amount of radionuclide that was present when each object formed. The oldest object would form with the highest amount of the radionuclide relative to a stable isotope of the same element, and the youngest will have the lowest amount. Obviously, no chronological information can be obtained about objects that formed after the radionuclide has reached a level too small to detect the radiogenic daughter isotope. 

Consider a hypothetical system that has an initial abundance of a short-lived radionuclide Nr. This nuclide is present as a fixed fraction of the parent element and its abundance can be written as the ratio of the radionuclide to a stable reference isotope of the same element, Ns. When the short-lived nuclide has completely decayed to its daughter nuclide, D, we have  

Nuclide Nr Half-life (years) Daughter isotope(s) Decay Stable nuclide mode N (Nr/Ns)o 

The initial ratio, (Nr/Ns)o, is what we hope to determine. We can measure two quantities to extract this information. One is the ratio of the daughter isotope to a stable isotope of the same element. The abundance of the daughter isotope is the sum of the initial abundance, D/i, and the radiogenic component/)  

The other is the ratio of the abundance of the reference isotope of the parent element to the abundance of the reference isotope of the daughter element  

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Cs, I, and Sr) in her milk which is usuaUy consumed fairly near the cow within a few days after production. Other foodstuffs may be stored for months, allowing the short-lived radionuclides to decay away. Moreover, milk is a major food for children who are more susceptible to radiation... 

The inventory of long-lived fission products is far less than an LWR because of the short exposure of the fuel to minimize Pu-240 production. But the health effects from an accident are comparable because it primarily results from short lived radionuclides. 

A specialized application of microwave-assisted organic synthesis involves the preparation of radiopharmaceuticals labeled with short-lived radionuclides, particularly for use in positron emission tomography [70-72]. This represented an excellent application of microwave technology, where the products must be prepared quickly and in high radiochemical yield, on a small scale. 

Fusion reactions produce only short-lived radionuclides there would be no long-term waste-disposal problem. 

Muller, W.A., A.B. Murray, U. Linzner, and A. Luz. 1990. Osteosarcoma risk after simultaneous incorporation of the long-lived radionuclide 227Ac and the short-lived radionuclide 227Th. Radiation Res. 121 14-20. 

Because many of the radionuclide measurements in seawater require sample sizes of 20-200 liters, it is not practical to distribute true seawater reference materials containing these radionuclides. Furthermore, several of the radionuclide half-lives are only a few days to weeks. A different strategy is clearly required. The most reasonable approach is to prepare a reference material in the field by diluting solutions containing the long-lived parents of the short-lived radionuclides with a volume of seawater similar to the volume used for analyses. 

Russell SS, Srinivasan G, Huss GR, Wasserburg GJ, MacPherson GJ (1996) Evidence for widespread A1 in the solar nebula and constraints for nebula time scales. Science 273 757-762 Russell SS, Gounelle M, Hutchison R (2001) Origin of short-lived radionuclides. Phil Trans R Soc Lond A 359 1991-2004... 

Lasaga 1981), although more conservative formulations tend to be used in the short-lived radionuclide literature that are related to the half-life, such as ... 

The centrifugal separator of the AKUEVE system is also used for phase separation in the SISAK technique [84]. SISAK is a multistage solvent extraction system that is used for studies of properties of short-lived radionuclides, e.g., the chemical properties of the heaviest elements, and solvent extraction behavior of compounds with exotic chemical states. In a typical SISAK experiment, Fig. 4.34, radionuclides are continuously transported from a production... 

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.

M.J. Welch, Radiopharmaceuticals and other Compounds Labeled with Short-Lived Radionuclides, Pergamon Press, Oxford - New York - Toronto - Sydney -Paris - Frankfurt, (1977). 

Short-lived radionuclides are those with half-lives sufficiently short that any atoms present in the early solar system would have completely decayed away. In 1960, John Reynolds found the first clear evidence that short-lived nuclides were present in the form of large excesses of Xe, the decay product of short-lived I, in chondritic meteorites. This discovery showed that elements had been synthesized in stars shortly before the formation of the solar system. A more important short-lived radionuclide, 26A1, was demonstrated to have been present in meteorites by Typhoon Lee and coworkers in... 

The chemical compositions of individual chondrules have been determined by neutron activation of extracted samples or by electron microprobe analyses of chondrules in situ. Some, but not all chondrules are depleted in moderately volatile elements. There is a compositional continuum between the olivine-rich and aluminum-rich chondrules. Original concentrations of the short-lived radionuclide 26A1 in chondrules suggest they formed very early, before all of this isotope decayed, but as much as 2-5 million years after the formation of CAIs (see Refractory Inclusions, below). 

Table 8.8 Short-lived radionuclides used in cosmochemistry ...

Three types of isochron diagrams are used in discussions of short-lived radionuclides. An internal isochron is one based entirely on measurements from the object being dated. By measuring several minerals with different parent/daughter elemental ratios, one can obtain an array of data that gives both the initial ratio (NR/Ns)a and the initial isotopic ratio of the daughter element Figure 8.25 shows an example of an internal isochron for an... 

Short-lived radionuclides can provide high-resolution relative chronometers. The shorter the half-life, the higher the time resolution is. Short-lived systems currently in use can resolve time differences of a few hundred thousand years at 4.57 Ga. But in order to get absolute time, the short-lived systems must be tied to a long-lived radionuclide. 

Wasserburg, G. J. and Papanastassiou, D. A. (1982) Some short-lived nuclides in the early solar system a connection with the placental ISM. In Essays in Nuclear Astrophysics, eds. Barnes, C. A., Clayton, D.D. and Schramm, D.N. Cambridge Cambridge University Press, pp. 77-140. A good review of the early history of chronology using short-lived radionuclides. 

In this chapter, we review what is known about the chronology of the solar system, based on the radioisotope systems described in Chapter 8. We start by discussing the age of materials that formed the solar system. Short-lived radionuclides also provide information about the galactic environment in which the solar system formed. We then consider how the age of the solar system is estimated from its oldest surviving materials - the refractory inclusions in chondrites. We discuss constraints on the accretion of chondritic asteroids and their subsequent metamorphism and alteration. Next, we discuss the chronology of differentiated asteroids, and of the Earth, Moon, and Mars. Finally, we consider the impact histories of the solar system bodies, the timescales for the transport of meteorites from their parent bodies to the Earth, and the residence time of meteorites on the Earth s surface before they disintegrate due to weathering. 

Figure 9.5 compares the abundance ratios of short-lived radionuclides in the early solar system to the abundance ratios predicted by a standard model for galactic chemical... 

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