GB885786A - Improvements in the production of zirconium hydride - Google Patents

Abstract

Zirconium or an alloy containing a major proportion of zirconium is hydrided by raising the temperature of the metal in a controlled atmosphere to at least 700 DEG C. and below the melting point, introducing H2, if necessary, to provide a hydrogen effective pressure not in excess of the dissociation pressure of the b -solid solution of zirconium, and cooling at a sufficiently slow rate to maintain the H2 effective pressure not in excess of the dissociation pressure. The controlled atmosphere may be vacuum, e.g. a pressure not more than 1m Hg. or an atmosphere of H2 and/or one, or more, inert gases. The hydriding temperature may be 700-900 DEG C., and the pressure may be not more than 100 mm. Hg above the dissociation pressure, which will take into account the effect of contaminants, and provide an effective pressure not above the dissociation pressure, the dissociation pressure being determined from the accompanying Figures (not shown). The hydriding may be effected on Zr or alloy formed, e.g. by drawing or rolling, into any size or shape, e.g. rod or plate, and a hydride, which may contain up to 1,9 or more atom ratio H:Zr, body is produced without cracking or distortion, provided allowance is made for expansion of the body in forming hydride. Alloys may be Zr-U alloys containing up to 8% U. The surface of the metal body may be cleaned before hydriding by treating with an aqueous solution of a mixture of HNO3 and HF, washing with distilled water, and drying. H2 before use should be purified by passing over activated charcoal at say -195 DEG C. In a modification of the process, the hydriding is continued until the b -solid solution phase is saturated with hydrogen, the temperature is adjusted to 800-850 DEG C. and the H2 pressure is adjusted to 200-300 mm. above the dissociation pressure of the b -solid solution until further hydriding has occurred in the b and d , or d phase.