Naturally occurring zirconium (40Zr) is composed of four stable isotopes (one, 94Zr, may in the future be found radioactive), and one very long-lived radioisotope (96Zr), a primordial nuclide that decays via double beta decay with an observed half-life of 2.34 × 1019 years;[4] it can also undergo single beta decay, which is not yet observed, but the theoretically predicted value of t1/2 is 2.4 × 1020 years.[5] The second most stable radioisotope is 93Zr, which has a half-life of 1.61 million years. Thirty other radioisotopes have been observed from 77Zr to 114Zr; all have half-lives less than a day except for 95Zr (64.032 days), 88Zr (83.4 days), and 89Zr (78.36 hours). The most stable of the isomeric states is just 4.16 minutes for 89mZr.
↑()– Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
↑#– Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
↑Bold half-life– nearly stable, half-life longer than age of universe.
12#– Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
↑Bold symbol as daughter– Daughter product is stable.
↑() spin value– Indicates spin with weak assignment arguments.
↑Theorized to also undergo β− decay to 96Nb with a partial half-life greater than 2.4×1019y[11]
Zirconium-88
88Zr is a radioisotope of zirconium with a half-life of 83.4 days. In January 2019, this isotope was discovered to have a thermal neutron capturecross section of approximately 861,000 barns; this is several orders of magnitude greater than predicted, and greater than that of any other nuclide except xenon-135.[13]
Zirconium-89
89Zr is a radioisotope of zirconium with a half-life of 78.36 hours, produced by proton irradiation of natural yttrium (89Y). Its most prominent gamma photon (99% of decays) has an energy of 909keV and it emits a positron (as opposed to electron capture) about 23% of decays.[14] Zirconium-89 is employed in specialized diagnostic applications using positron emission tomography[15] imaging, for example, with zirconium-89 labeled antibodies (immuno-PET).[16]
93Zr is a radioisotope of zirconium with a half-life of 1.61 million years, decaying through emission of a low-energy beta particle. 73% of decays populate an excited state of niobium-93, which decays with a half-life of 13.9 years (almost entirely by internal conversion, emitting no gamma ray) to the stable ground state of 93Nb, while the remaining 27% of decays directly populate the ground state.[10] It is one of the 7 long-lived fission products. The low specific activity and low energy of its radiation limit the radioactive hazards of this isotope, and its insolubility makes it unlikely to escape a waste repository; all these are shared with palladium-107.
Nuclear fission produces it at a fission yield of 6.3% (thermal neutron fission of 235U), one of the most abundant fission products. Nuclear reactors usually contain large amounts of zirconium as fuel rodcladding (see zircalloy), and neutron irradiation of 92Zr also produces some 93Zr, though this is limited by 92Zr's low neutron capturecross section of 0.22 barns. Indeed, one of the primary reasons for using zirconium in fuel rod cladding is its low cross section.
93Zr also has a low neutron capturecross section of 0.7 barns.[18][19] Most fission zirconium consists of other isotopes; the other isotope with a significant neutron absorption cross section is 91Zr with a cross section of 1.24 barns. 93Zr is a less attractive candidate for disposal by nuclear transmutation than are 99Tc and 129I. The isotope could be recycled: if the effect on the neutron economy of 93 Zr's higher cross section is deemed acceptable, irradiated cladding and fission product zirconium (which are mixed together in most current nuclear reprocessing methods) could be used to form new zircalloy cladding. Once the cladding is inside the reactor, the relatively low level radioactivity can be tolerated, but transport and manufacturing might require precautions not now taken.
↑Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3) 030003. doi:10.1088/1674-1137/abddaf.
↑Dilworth, Jonathan R.; Pascu, Sofia I. (2018). "The chemistry of PET imaging with zirconium-89". Chemical Society Reviews. 47 (8): 2554–2571. doi:10.1039/C7CS00014F. PMID29557435.
↑Van Dongen, GA; Vosjan, MJ (August 2010). "Immuno-positron emission tomography: shedding light on clinical antibody therapy". Cancer Biotherapy and Radiopharmaceuticals. 25 (4): 375–85. doi:10.1089/cbr.2010.0812. PMID20707716.
↑M. B. Chadwick et al, "ENDF/B-VII.1: Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data", Nucl. Data Sheets 112(2011)2887. (accessed at www-nds.iaea.org/exfor/endf.htm)
↑"ENDF/B-VII.1 Zr-93(n,g)". National Nuclear Data Center, Brookhaven National Laboratory. 2011-12-22. Archived from the original on 2009-07-20. Retrieved 2014-11-20.
