Production of ytterbium-169 radiography sources in a high flux reactor
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Date
1974-02
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Publisher
Australian Atomic Energy Commission
Abstract
The irradiation of ytterbium-168 in the Hollow Fuel Element facilities of the AAEC research reactor HIFAR was studied to determine the optimum conditions for the production of ytterbium-169 for industrial radiography sources. The thermal neutron activation cross-section of ytterbium-168 is 3,470 barns; in core positions in the reactor this is significantly increased by the contribution of epithermal neutron activation. Flux depression and target burnup are such that the activation formula normally used for radioisotope production calculations is inadequate. Therefore, a modified formula which includes corrections for these effects, combined with iterative computer calculations to correct for effects resulting from the change in target mass during irradiation, was used to calculate ytterbium-169 yields. It was found that for targets containing 10 mg and 20 mg of Yb2O3, there is an optimum ytterbium-168 enrichment of approximately 20 per cent. The activation of such targets can be increased significantly by diluting the Yb2O3 with a low neutron cross-section material such as graphite. The optimum irradiation time in HIFAR in a thermal neutron flux of 1.0 x 10 14 n cm-2s-1 is approximately one operating period of 24 days.
Description
Keywords
Gamma radiation, Cross sections, HIFAR Reactor, Isotope separation, Neutron beams
Citation
Hetherington, E. L. R. & Wood, N. R. (1974). Production of ytterbium-169 radiography sources in a high flux reactor. (ANSTO/E306). Lucas Heights, NSW: Australian Atomic Energy