An analogy of interstitial site occupancy and hydrogen induced disproportionation of Zr1-xTixCo ternary alloys

The hydrogen induced disproportionation behavior of Ti-substituted ZrCo alloys was investigated to explore their suitability for International Thermonuclear Experimental Reactor (ITER) Storage and Delivery System (SDS). The isothermal disproportionation studies on Ti substituted alloys were carried out in conditions simulating ITER SDS i.e. 750 K temperature and 100 kPa hydrogen pressure. It was observed that the rate of disproportionation of Ti substituted ZrCo alloys was found to vary as ZrCo > Zr0.9Ti0.2Co > Zr0.7Ti0.3Co > Zr0.8Ti0.2Co. X-ray diffraction measurements revealed the formation of TiCoH phase along with Ti substituted ZrCo2 and ZrH2 phases as a result of disproportionation reaction of alloys. Neutron diffraction measurements on deuterides indicated that deuterium occupancy in 8e site and the corresponding Zr-D distance provide the primary driving force for disproportionation of alloys to take place. A plausible potential energy profile based on thermodynamic and kinetic considerations was proposed to explain the disproportionation mechanism of alloys. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.