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Decay series

The terms radioactive transmutation and radioactive decay arc synonymous-Gencrally, the term decay is preferred in the English literature. As already mentioned in section 2.1, many radionuclides were found after the discovery of radioactivity in 1896, These radionuclides were named UXi, UX2. or mesothorium 1, mesothorium 2,., or actinouranium. in order to indicate their genesis. Their atomic and mass numbers were determined later, after the concept of isotopes had been established. [Pg.29]

The great variety of radionuclides present in thorium and uranium ores are listed in Tables 4.1, 4.2 and 4.3. Whereas thorium has only one isotope with a very long half-life (- Th), uranium has two and giving ri.se to one decay scries for Th and two for U. In order to distinguish the two decay series of U, they were named after long-lived members of practical importance the uranium-radium series and the actinium series. The uranium-radium series includes the most important radium isotope ( Ra) and the actinium scries the most important actinium isotope ( Ac), [Pg.29]

Nuclide Half-life Decay mode Maximum energy of the radiation [MeVj [Pg.29]

In all of these decay series, only a and p decay are observed. With emission of an y. particle ( Me) the mass number decreases by 4 units, and the atomic number by 2 units [A — A -A Z - Z - 2). With emission of a / particle the mass number docs not change, whereas the atomic number increases by 1 unit A — A Z = Z + 1). These are the first and second displacement laws formulated by Soddy and Fajans in 1913. By application of the displacement laws it can easily be deduced [Pg.29]

The decays of U, and Xh are more complicated. If we ignore the intermediate isotopes in the U and Th decay series, then for the system [Pg.76]

However, for investigating short -term recent geological processes, the intermediate isotopes in decay series cannot be ignored and in fact these short-lived intermediate isotopes are powerful in deciphering young geological processes. [Pg.76]

Before we study the behaviors of U-series disequilibria during partial melting, we try to understand a simple case of U-decay series in an isolated system in the absence of melting. For this undisturbed closed system, the uranium-thorium-radium (U-Th-Ra) series disequilibria (Fig. [Pg.76]

1) can be described by the following system of three differential equations  [Pg.77]


A few techniques exist that do not provide for direct dating but rather give information as to whether the object is of modem manufacture. One of these is dating (53). In the decay series of uranium, the first long-Hved member after Ra, with its 1622 yr half-life, is which has a 22 yr... [Pg.419]

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. [Pg.35]

Figure 1 Chart showing the decay chain of the U-Th decay series isotopes. Vertical arrows define alpha (a) decays while beta (/ ) decays are illustrated by diagonal arrows... Figure 1 Chart showing the decay chain of the U-Th decay series isotopes. Vertical arrows define alpha (a) decays while beta (/ ) decays are illustrated by diagonal arrows...
Thorinm-232 is the only non-radiogenic thorium isotope of the U/Th decay series. Thorinm-232 enters the ocean by continental weathering and is mostly in the particulate form. Early measurements of Th were by alpha-spectrometry and required large volume samples ca. 1000 T). Not only did this make sample collection difficult, but the signal-to-noise ratio was often low and uncertain. With the development of a neutron activation analysis " and amass spectrometry method " the quality of the data greatly improved, and the required volume for mass spectrometry was reduced to less than a liter. Surface ocean waters typically have elevated concentrations of dissolved and particulate 17,3 7,62... [Pg.46]

In the U-Th decay series there are four radium isotopes, Ra (tj j =... [Pg.48]

Polonium has no stable isotopes, all 27 isotopes being radioactive of these only °Po occurs naturally, as the penultimate member of the radium decay series ... [Pg.748]

The much rarer element, protactinium, was not found until 1913 when K. Fajans and O. Gohring identified Pa as an unstable member of the decay series ... [Pg.1250]

FIGURE 17.16 The uranium-238 decay series. The times are the half-lives of the nuclides (see Sei tion 17.7). The unit a, for annum, is the SI abbreviation for year. [Pg.825]

Polonium, completing the elements of Group 16, is radioactive and one of the rarest naturally occurring elements (about 3 x 10 " % of the Earth s crust). The main natural source of polonium is uranium ores, which contain about lO g of Po per ton. The isotope 210-Po, occurring in uranium (and also thorium) minerals as an intermediate in the radioactive decay series, was discovered by M. S. Curie in 1898. [Pg.4]

Figure 1. The three decay series from uranium, thorium, and actinium as published by Soddy in 1913 (Soddy 1913b). Figure 1. The three decay series from uranium, thorium, and actinium as published by Soddy in 1913 (Soddy 1913b).
The uranium and thorium decay-series contain radioactive isotopes of many elements (in particular, U, Th, Pa, Ra and Rn). The varied geochemical properties of these elements cause nuclides within the chain to be fractionated in different geological environments, while the varied half-lives of the nuclides allows investigation of processes occurring on time scales from days to 10 years. U-series measurements have therefore revolutionized the Earth Sciences by offering some of the only quantitative constraints on time scales applicable to the physical processes that take place on the Earth. [Pg.3]

If we consider this pair of radioactive isotopes for time scales greater than six half-lives of N2, Equation (3b) can be simplified. Because each decay series starts with a long-lived parent, it is commonly the case that A,2. In this case, after six half lives, e approaches zero and can be removed from the equation. For time scales such that 6T2 [Pg.6]

Figure 3. Parent daughter disequilibrium will return to equilibrium over a known time scale related to the half-life of the daughter nuclide. To return to within 5% of an activity ratio of 1 requires a time period equal to five times the half-life of the daughter nuclide. Because of the wide variety of half-lives within the U-decay-series, these systems can be used to constrain the time scales of processes from single years up to 1 Ma. Figure 3. Parent daughter disequilibrium will return to equilibrium over a known time scale related to the half-life of the daughter nuclide. To return to within 5% of an activity ratio of 1 requires a time period equal to five times the half-life of the daughter nuclide. Because of the wide variety of half-lives within the U-decay-series, these systems can be used to constrain the time scales of processes from single years up to 1 Ma.
Table 2. Half-lives for the U- and Th- decay series nuclides, with decay modes. [Pg.16]

In this chapter we discuss improvements documented in the literature over the past decade in these areas and others. Chemical procedures, decay-counting spectroscopy, and mass spectrometric techniques published prior to 1992 were previously discussed by Lally (1992), Ivanovich and Murray (1992), and Chen et al. (1992). Because ICPMS methods were not discussed in preceding reviews and have become more commonly used in the past decade, we also include some theoretical discussion of ICPMS techniques and their variants. We also primarily focus our discussion of analytical developments on the longer-lived isotopes of uranium, thorium, protactinium, and radium in the uranium and thorium decay series, as these have been more widely applied in geochemistry and geochronology. [Pg.25]

The end of the 1980 s saw the application of TIMS to U-series measurement (Chen et al. 1986 Edwards et al. 1987 Goldstein et al. 1989). This represented a major technological advance. Analysis time was reduced from one week to several hours, sample sizes for many carbonate or volcanic rock samples decreased from -10-100 pg to 0.1-1 ug U or Th, measurement precision improved from percent to permil levels, and for the decay series, the dating range was extended from 350,000 years to... [Pg.32]

Oversby VM, Gast PW (1968) Lead isotope composition and uranium decay series disequilibrimn in recent volcanic rocks. Earth Planet Sci Lett 5 199-206... [Pg.172]


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