Declassified 21 Sep 1973. A wide range of metallic hydrides (to NH 9.0), each containing additives to tailor the nuclear characteristics, have been fabricated successfully. Specific additives have included B compounds and high Z- material compounds, e.g., W, Hf, Th. Hydrided Ti which contains B compounds has proven relatively easy to fabricate and has shown excellent radiation stability. Post-irradiation appearance (through 6 x 10/sup 20/ nvt thermal) shows no visible changes. Strengths to 150,000 psi at 380 deg C (with ductile failure) have been observed for TiH. Sound, massive N/sub H/ 6.9 hydrided Zr rods have been fabricated in hydride-furnace batches as large as 50 kg, with 100% yield. A 50 Th-50 Zr hydride of N/sub H/ 6.7 and higher has been fabricated. The basic structure, apparently ThZr/sub 2/H/sub 8/, is a cubic spinel-type structure and is the first reported hydride having this structure. This material, when containing a B compound additive, will probably provide more gamma shielding than is generally needed, but the material has interesting possibilities as a combination breeder-blanket-shield. It now appears that almost any combination of looked-for nuclear properties can be incorporated into a metallic hydride composite having useful engineering characteristics. (16 tables, 23 figs) (DLC)