Abstract
A GREAT advantage of production of radioisotopes by threshold reactions (n, p) and (n, α), relative to neutron capture (n, γ), is that the radioisotope can be separated chemically from the target material, and hence be obtained in high specific activity, in principle completely carrier-free. The rate of threshold reactions in the pile, however, is much smaller in general than that of capture reactions, not only because of the low cross-sections for neutrons in the MeV. range but also because of the low flux of neutrons of that energy in the pile. As measurement of the small yields of such reactions is often difficult, especially for long-lived radioisotopes, it is very useful to be able to predict approximate yields in advance. An example is furnished by the reaction 54Fe(n, p)54Mn, recently discussed by Stafford and Stein1; in this case some experiments had indicated production of the 324-day manganese-54 by pile neutrons, whereas others showed none. The most recent experiments1, however, utilizing samples enriched in iron-54, definitely established the reaction with a cross-section for fast neutrons of 11 millibarns (10−27 cm.2). It is the purpose of the present communication to point out that the approximate yields for threshold reactions in the pile can be predicted, and to illustrate the method for 54Fe(n, p)54Mn as an example.
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References
Stafford, G. H., and Stein, L. H., Nature, 172, 1103 (1953).
Hughes, Spatz and Goldstein (unpublished, see ref. 4).
Bonner, Ferrel and Rinehart, Phys. Rev., 87, 1032 (1952). Hill, D. L., Phys. Rev., 87, 1034 (1952). Watt, B. E., Phys. Rev., 87, 1037 (1952).
The measurements, as well as the details of their interpretation, are described by the author in “Pile Neutron Research”, 93 (Addison-Wesley, 1953).
Collins, Nier and Johnson, Phys. Rev., 86, 408 (1953).
Ref. 4, pp. 60, 106.
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HUGHES, D. Pile Production of Radioisotopes by Threshold Reactions. Nature 173, 396 (1954). https://doi.org/10.1038/173396a0
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DOI: https://doi.org/10.1038/173396a0
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