The work reported deals with the preparation and physical properties, especially thermal dissociation pressures, and densities of hydrides, hydrogen- metal systems, and mixtures of hydrides with other substances. Possible applicatlons as moderators, high-temperature neutron shields, and low-temperature shields are cited and design problems discussed. Most of the data on dissociation pressures cover ranges and compounds not hltherto explored because of experimental difficulties and the basic knowledge of the thermal behavior of hydrides was substantially increased. New hydrldes were prepared and several reported in the literature were shown not to exist. The following compounds, mixtures, and systems were studled: Tl-H, U-H, Ll-H, Na-H, Ca-H, Ba-H, Th-H, Sr- H; NaH-NaF, NaH-NaOH, NaH-CaH/, LlH-LiF, CaH/sub 2/-CaF/sub 2/, CaH/sub 2/-CaC/ sub 2/,CaH/sub 2/-Ca/sub 3/N/sub 2/; FeH/sub 3/ (alleged), NiH/sub 2/ (alleged), Ti(BH/sub 4/)/sub 3/, Th(BH/sub 4/)/sub 4/, WH/sub 4/ (attempted), W(BH/sub 4/)/ sub 4/ (attempted), /sub 4/NBH/sub 4/, (CH , and ydrides are ing an N/sub H/ comparable to water yet stable at red heat, compounds giving a neutron shield weight less than half that of water, and compounds suitable for use as hightemperature moderators containing large amounts of hydrogen. (auth)

None