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Thulium-170 (Tm or Tm-170) is a radioactive isotope of thulium proposed for use in radiotherapy and in radioisotope thermoelectric generators.

Properties

Thulium-170 has a binding energy of 8105.5144(43) keV per nucleon and a half-life of 128.6±0.3 d. It decays by β decay to Yb about 99.869% of the time, and by electron capture to Er about 0.131% of the time. About 18.1% of β decays populate a narrow excited state of Yb at 84.25474(8) keV (t_1/2 = 1.61 ± 0.02 ns), and this is the main X-ray emission from Tm; lower bands are also produced through X-ray fluorescence at 7.42, 51.354, 52.389, 59.159, 59.383, and 60.962 keV.

The ground state of thulium-170 has a spin of 1. The charge radius is 5.2303(36) fm, the magnetic moment is 0.2458(17) μ_N, and the electric quadrupole moment is 0.72(5) e⋅b.

Proposed applications

As a rare-earth element, thulium-170 can be used as the pure metal or thulium hydride, but most commonly thulium oxide due to the refractory properties of that compound. The isotope can be prepared in a medium-strength reactor by neutron irradiation of natural thulium, which has a high neutron capture cross section of 103 barns.

Medicine

In 1953, the Atomic Energy Research Establishment introduced thulium-170 as a candidate for radiography in medical and steelmaking contexts, but this was deemed unsuitable due to the predominant high-energy bremsstrahlung radiation, poor results on thin specimens, and long exposure times. However, Tm has been proposed for radiotherapy because the isotope is simple to prepare into a biocompatible form, and the low-energy radiation can selectively irradiate diseased tissue without causing collateral damage.

Radiothermal generator

As the oxide (Tm₂O₃), thulium-170 has been proposed as a radiothermal source due to it being safer, cheaper, and more environmentally friendly than commonly used isotopes such as plutonium-238. The heat output from a Tm source is initially much greater than from a Pu source relative to mass, but it declines rapidly due to its shorter half-life.

References

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2. ^ "NuDat 3". www.nndc.bnl.gov.
3. ^ Polyak, Andras; Das, Tapas; Chakraborty, Sudipta; Kiraly, Reka; Dabasi, Gabriella; Joba, Robert Peter; Jakab, Csaba; Thuroczy, Julianna; Postenyi, Zita; Haasz, Veronika; Janoki, Gergely; Janoki, Gyozo A.; Pillai, Maroor R.A.; Balogh, Lajos (October 2014). "Thulium-170-Labeled Microparticles for Local Radiotherapy: Preliminary Studies". Cancer Biotherapy and Radiopharmaceuticals. 29 (8): 330–338. doi:10.1089/cbr.2014.1680. ISSN 1084-9785. PMID 25226213 – via Academia.edu.
4. Mertzimekis, Theo J. "NUMOR | Nuclear Moments and Radii | University of Athens | since 2007". magneticmoments.info. Retrieved 12 November 2023.
5. ^ Walter, C.E.; Van Konynenburg, R.; VanSant, J.H. (6 September 1990). "Thulium-170 heat source". doi:10.2172/10156110. OSTI 10156110.
6. ^ Dustin, J. Seth; Borrelli, R.A. (December 2021). "Assessment of alternative radionuclides for use in a radioisotope thermoelectric generator". Nuclear Engineering and Design. 385: 111475. doi:10.1016/j.nucengdes.2021.111475. S2CID 240476644.
7. Hilbish, Theodore F. (November 1954). "Developments in diagnostic radiology". Public Health Reports. 69 (11): 1017–1027. doi:10.2307/4588947. ISSN 0094-6214. JSTOR 4588947. PMC 2024396. PMID 13215708.
8. ^ Halmshaw, Ronald (1995). Industrial radiology: theory and practice (2. ed.). London: Chapman & Hall. pp. 59–60. ISBN 0412627809.
9. ^ Vats, Kusum; Das, Tapas; Sarma, Haladhar D.; Banerjee, Sharmila; Pillai, M.r.a. (December 2013). "Radiolabeling, Stability Studies, and Pharmacokinetic Evaluation of Thulium-170-Labeled Acyclic and Cyclic Polyaminopolyphosphonic Acids" (PDF). Cancer Biotherapy and Radiopharmaceuticals. 28 (10): 737–745. doi:10.1089/cbr.2013.1475. ISSN 1084-9785. PMID 23931111. Archived from the original (PDF) on 2023-11-12.
10. ^ Walter, C. E. (1 July 1991). "Infrastructure for thulium-170 isotope power systems for autonomous underwater vehicle fleets". Lawrence Livermore National Lab., CA (United States). OSTI 5491258.
11. Alderman, Carol J. (1993). "Thulium heat sources for space power application". AIP Conference Proceedings. Vol. 271. pp. 1085–1091. doi:10.1063/1.43194.

• Isotopes of thulium