Insertion of uranium into HTS precursor powders prior to texturing, and irradiation with thermal neutrons after texturing is called U/n processing. Damage caused by uranium fission fragments has been extensively studied for pinning center behavior in Y123, and Ag-BiSCCO tape. In both HTS systems results for Jc, anisotropy, etc. are excellent. We consider the chemical and physical conditions under which U/n processing is successful, including spacing, S, and size of deposits of U compounds, and neutron absorption by the HTS. If δ=length of the quasi-columnar fission fragment defects, we find S<25 ∼5.4μm is needed for the best U/n results and, thus, if deposits of U compounds exist, sub-micron size is desirable. Application of these conditions is considered to Y123, Ag-BiSCCO tape, Nd123, Sm123 and Gd123. Studies in progress of Nd123 and Sm123 are reported.
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