THE REACTION OF HYDROGEN WITH ZIRCONIUM-1 AND -25 w/o URANIUM ALLOYS

Hydrogen-absorption isotherms were measured over the range 535 to 835 C for zirconium--1 wt.% and--25 wt.% uranium alloys. X-ray-diffraction studies were made over approximately the same temperature range for the zirconium--1, -- 25, and --50 wt.% uranium alloys. In general, the alloys resenable the zirconium- hydrogen system, modified by the presence of uranium. With 1 wt.% uranium, the phase boundaries of the zirconium--hydrogen system are shifted to slightly lower hy-drogen contents. With 25 wt.% uranium, the first - two-phase-' region shifts to a hydrogen content 20 wt.% greater than in the zirconium--hydrogen system, while the second cctwo-phase'' region is unchanged. The eutectoid temperature is increased from 547 to 601 C. Heats of solution of hydrogen in the alloys were found to range from --25.9 to --47.9 kcal per mole for the 1 wt.% alloy, and from --30.7 to --50.6 kcal per mole for the 25 in.% alloy-. The x-ray-diffraction data support the interpretation that, as hydrogen is absorbed, the alloys break down to form uranium and zirconium, and the latter absorbs the hydrogen. The entire ternary isotherms could not be deduced from the data. However, three aspects appear certains (1) the extent of the phase fields along the zirconium-- hydrogen binary at 1 wt.% uranium, (2) the existence of alpha zirconium, alpha uranium, and ZrH/sub x/ three-phase fields at low temperatures, and (3) the existence of fields containing beta uranium and ZrH/sub x/ at higher temperatures for both the 25 and 50 wt.% alloys. (auth