Isotopes decay properties

Table I. Generator Radionuclides for Labeling Cryptates Isotope Decay Properties Parent...

AH of the 15 plutonium isotopes Hsted in Table 3 are synthetic and radioactive (see Radioisotopes). The lighter isotopes decay mainly by K-electron capture, thereby forming neptunium isotopes. With the exception of mass numbers 237 [15411-93-5] 241 [14119-32-5] and 243, the nine intermediate isotopes, ie, 236—244, are transformed into uranium isotopes by a-decay. The heaviest plutonium isotopes tend to undergo P-decay, thereby forming americium. Detailed reviews of the nuclear properties have been pubUshed (18). 

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. 

Radical trapping studies, 14 277 Radicidation, 8 655 Radioactive decay, 21 287—288 particles associated with, 21 291 Radioactive decay properties of uranium isotopes, 25 393 Radioactive emission, interaction with tracer molecules, 21 276 Radioactive iodine, protection from,... 

Table 1. Decay properties and availability of actinide isotopes for solid state studies ...

Actinides, the chemical elements with atomic numbers ranging from 89 to 103, form the heaviest complete series in the Periodic Table. They are radioelements, either naturally occurring or synthesized by nuclear reactions. Their predominant practical application depends on the nuclear properties of their isotopes decay, spontaneous or induced fission. Their chemical and physical properties reflect a very complex electronic structure, and their study and understanding are a challenge to experimentalists and theoreticians. 

Browne, E. and R. B. Firestone. Table of Radioactive Isotopes, Wiley, New York, 1986. An authoritative compilation of radioactive decay properties. Do note that the spontaneous fission half-lives are missing for several heavy nuclei. 

Table 3-1 Decay Properties of Some Biochemically Important Isotopes...

The ionizing properties of Pu and other radioactive materials is one determinant of the level of hazard associated by different exposure routes. Radioactive elements are those that undergo spontaneous transformation (decay) in which energy is released either in the form of particles, such as alpha or beta particles, or waves, such as gamma or X-ray. Plutonium exists in several isomeric forms, the most important of which are Pu-238 and Pu-239. When these isotopes decay, they emit primarily alpha particles, which are densely ionizing and, therefore, damaging however, the penetration of alpha particles into tissue is slight, so... 

The radioactive decay properties of the plutonium isotopes that appear in irradiated reactor fuel are listed in Table 9.14. All but Pu and Pu are alpha emitters. Because it penetrates matter only weakly, alpha radiation is stopped by the outer layer of dead skin and is not a hazard outside the body. However, plutonium is very effective biologically when deposited in or on living tissue, particularly if by inhalation or by contaminated injuries. Pu is a relatively short-lived (13.2-year... 

Although a richness of information has been obtained, a number of open questions still remain. For elements which were chemically identified, like Rf or Sg, a more detailed study, both theoretical and experimental, should follow. Elements 109, 110 and 111 are still to be studied experimentally the prerequisites for their successful experimental studies should be similar to those of the lighter transactinides. These include the existence of isotopes long enough for chemical studies, knowledge of their nuclear decay properties, so that they can be positively identified, synthesis reactions with the highest possible cross sections and suitable techniques for their separation. For those elements, predictions of the chemical behaviour are a matter of future research. Especially difficult will be the accurate prediction of adsorption of the heaviest elements on various surfaces, or their precipitation from aqueous solutions by determining electrode potentials. For that, further developments in accurate calculational schemes are needed. More sophisticated methods are needed to treat weak interactions, which are important for physisorption processes. 

Radiation Power Rate. For sources consisting of a known weight of a single radioisotope whose decay properties are known, the power in Mev/g-sec can be computed from Eq. (10-14) or (10-16). Conversion to watts is then made on the basis that 1 Mev/sec = 1.6 X 10 watt. The addition of other radioisotopes to the volume source requires a summation of the power value calculated for each isotope as described. The power liberation from a complex mixture of radioisotopes such as found in the fission products of U fuel is time-consuming to calculate. Figure 10-7 avoids the necessity of this by giving the and y power, curies and composition of the radioactive isotopes, all as a function of elapsed time after the fuel is pulled from the reactor. This elapsed time is known as the radiation cooling period. 

In a later experiment (Tiirler et al., 1999), the isothermal temperature was varied to obtain the adsorption enthalpy for Sg. The yield of short-lived W isotopes from reactions on Gd incorporated in the target was also measured at the same time. An adsorption enthalphy of-96 1 kJ mol 1 was obtained for the dioxydichloride of W in agreement with the previous measurement. Based on 11 events attributable to Sg, an adsorption enthalpy of -100 4 kJ mol-1 or 96 1 kJ mol 1 was obtained depending on the Sg half-life used in the Monte Carlo calculations. Thus, the experimental results confirmed the theoretically predicted volatility sequence of Mo > W > Sg. From an analysis of the decay properties of the correlated decay chains detected in these experiments, Tiirler et al. (1998) were able to recommend better half-lives and cross sections of 7.4 + 3.3/ - 2.7 s and approximately 0.24 nb for 265Sg and of 21 + 20/ - 12 s and approximately 0.025 nb for 266Sg for 22Ne beam energies between 120 and 124 MeV. 

A number of other similar cases were observed in which seemingly new radioactive elements with unique decay patterns were chemically identical to known elements. The recognition that there were identical elements with differing radioactive decay properties was made in 1909 and 1910 by Svedberg and Soddy respectively. Soddy coined the term isotope ( same place, i.e., in the periodic table) in 1913. 

It seemed too time consuming to both to write a new publication. They had a manuscript describing the decay properties of the supposed radium isotopes "Uber den Nachweis and das Verhalten der bei der Bestrahlung des Urans mittels Neutronen entstehenden Radium-Isotope (On the detection and the properties of the radium isotopes formed in the irradiation of... 

To search for new transuranium nuclides and to study decay properties of these nuclei, a composite system consisting of the gas-jet transport apparatus and an online isotope separator (JAEA-ISOL) has been developed by Ichikawa et al. (2002). This system enables one to simultaneously determine the mass number via the isotope separator and the atomic number by the measurement of X-rays associated with the EC/P" decay of a nucleus. The experimental setup is schematically drawn in O Fig. 18.9. 

Decay properties of transuranium nuclides lead to the understanding of proton excess heavy nuclei verification of the proton drip line, nuclear structure of large deformed nuclei such as octupole and hexadecapole deformation, and fission barrier heights. There are several textbooks and review articles on nuclear decay properties of transuranium nuclei (e.g., Hyde et al. 1964 Seaborg and Loveland 1985 Poenaru 1996). Theoretical nuclear models of heavy nuclei are presented by Rasmussen (1975) and the nuclear structure with a deformed single-particle model is discussed by Chasman et al. (1977). Radioactive decay properties of transuranium nuclei are tabulated in the Table of Isotopes (Firestone and Shirley 1996). Recent nuclear and decay properties of nuclei in their ground and isomeric states are compiled and evaluated by Audi et al. (1997), while the calculated atomic mass excess and nuclear ground-state deformations are tabulated by MoUer et al. (1995). 

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