The production of metastable nuclei such as 117mSn, 195mPt (for biomedical applications) and 119mSn (for mossbäuer spectroscopy) via neutron radiative capture reactions are characterized by small neutron cross-sections and, hence, low production rates. The metastable nuclei typically have excitation energy on the order of 100 keV and a large difference in spin from the ground state (most metastable nuclei have high spin). An alternative route for production of these types of metastable nuclei is through neutron inelastic scattering, where the cross-section of the AZ[n,n'γ]AmZ reaction in some cases is substantially higher than that of the (A-1)Z[n,γ]AmZ reaction. As has been shown for the case of 117mSn [Mausner et al, 1985], the magnitude of gain in the cross-section may compensate for the relatively lower fast neutron flux from a well-moderated fission spectrum, En≧Q[n,n'γ] (note that the excitation energy of metastable nuclei will represent the threshold for inelastic scattering). Large research reactors, such as HFIR, with significant fast neutron fluxes are most notably suited for these types of reactions. The results from a systematic study of the production of 117mSn, 119mSn, 125mTe, and 195mPt in the hydraulic tube facility (HT) of the HFIR will be presented in this meeting. In three out of four cases examined, the experimental yields from the [n,n'γ] reactions were higher than that obtained from the [n,γ] reactions. For 195mPt, 117mSn, and 119mSn, the relative gains in the specific activity were 1.4, 1.6, and 8.3, respectively. The larger gain for 119mSn could be attributed to the relatively lower excitation energy (89.5 keV) of this metastable nucleus.

Evaluation of neutron inelastic scattering for radioisotope production

256th National Meeting (2018)

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