Rhenium nuclides

Figure 1 Part from the Nuclide Chart with basic properties of important isotopes of rhenium and its...

Rhenium, atomic wt 186.2, occurs in nature as two nuclides 185Re [14391-28-7], mass 184.9530, in 37.500% abundance and 187Re [14391-29-8], mass 186.9560, in 62.500% abundance. The latter isotope is radioactive, emitting very low energy radiation and having a half-life estimated at 4.3 ( 0.5) x 1010 yr. The radioactive decay of this isotope has been used to date accurately the time of Earth s formation. 

The discovery of technetium (Z = 43) in 1937 and of promethium (Z = 61) in 1947 filled the two gaps in the Periodic Table of the elements. These gaps had been the reason for many investigations. Application of Mattauch s rule (section 2.3) leads to the conclusion that stable isotopes of element 43 cannot exist. Neighbouring stable isotopes could only be expected for mass numbers A 93, A < 91, A = 103 and A > 105. However, these nuclides are relatively far away from the line of jd stability. The report by Noddak and Tacke concerning the discovery of the elements rhenium and masurium (1925) was only correct with respect to Re (Z = 75). The concentration of element 43 (Tc) in nature due to spontaneous or neutron-induced fission of uranium is several orders of magnitude too low to be detectable by emission of characteristic X rays of element 43, as had been claimed in the report. 

Peacock RD (1966) The chemistry of technetium and rhenium. Elsevier, London Perrier C, Segre E (1937) Radioactive isotopes of element 43. Nature 140 193-194 Perrier C, Segre E (1947) Technetium the element of atomic munber 43. Natiu"e 159 24 (Letter) Richards P (1966) Nuclide generators. In Radioactive pharmaceuticals. USAEC symposiiun series, no. 6, (CONF-651111), Oak Ridge, Term., pp 155-163 Rimmer J (1982) Radiopharmaceutical composition based on technetium-99m and the reagent for making it. Eur Patent Appl EP 78,642... 

The later chemical study showed that neptunium was oxidized to hexavalent with the oxidizing agent, bromate ion BrOs it resembled uranium, not rhenium (Re), contrary to the expectation from the periodic table at that time. The result was the first evidence that an iimer electron shell (i.e., the 5f shell) is filled in the transuranium elements. The isotope of neptunium with the longest half-life (Ti/2 = 2.14 x 10 years) is Np, the mother nuclide of the... 

Probably the most comprehensive published assay of DU used in armor pen-etrators was reported on the basis of analysis of an unfired CHARM-3 penetrator (Trueman et al. 2004). A sample from the penetrator was dissolved in 9 M HCl, spiked with U as a yield monitor, and the uranium was separated from impurities on an ion-exchange resin. The isotopic composition of uranium was determined by mass spectrometric techniques. Actinides ( - Am and Np) were determined in the uranium-free solution by gamma spectrometry and 239+24opy and Pu were measured by alpha spectrometry and their presence was confirmed by ICPMS. Technetium-99 was determined by ICPMS when rhenium was used as a carrier and interferences from iron were eliminated by precipitating with ammonia while ruthenium and molybdenum were removed by separation on a chromatographic resin. The content of these radioactive nuclides is summarized in Table 2.7. 

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