| Hydrogen storage bed is a necessary component for deuterium-tritium fusion energy under development in International Thermonuclear Experimental Reactor?ITER?,which is applied to rapid and safe recovery/delivery of hydrogen isotopes.For practical application in ITER,requirements on storage capacity of 100 g?16.6 mol?tritium and hydrogen delivery rate of not less than 20 Pa·m3/s should be fulfilled by each bed.Aiming to this target,we conducted a comprehensive research involving hydrogen isotopes storage materials,bed configuration design and operation conditions of the hydrogen storage bed.In this thesis,studies were carried out not only to obtain a method for fast and efficient activation of ZrCo alloy but also to understand the detailed phase transformation during the dehydrogenation process of ZrCoH3.Meanwhile,based on a new bed design of thin double-layered annulus configuration,in which heat transfer and mass transfer can be substantially enhanced,full-scale ZrCo bed,Zr0.8Hf0.2Co bed,Zr0.8Ti0.2Co bed and depleted uranium bed were fabricated.The corresponding hydrogen storage behaviors including hydrogen recovery/delivery,thermal property,cycling performance and structural stability of these beds were systematically investigated.The main contents and results of this thesis are as follows:1.Effects of temperature and hydrogen pressure on the activation behavior of ZrCo alloyExperimental results showed that activation of ZrCo alloy essentially involved procedures including evacuation,hydrogenation and dehydrogenation.It was found that initial evacuation at temperature higher than 300? was clearly beneficial to the subsequent hydrogenation process.Hydrogen absorption rate of ZrCo alloy during the activation process could be enhanced by increasing the hydrogenation temperature,whereas hydrogen pressures had an indiscernible impact on the hydrogenation process.Compared with other temperatures and hydrogen pressures,100? and 0.8 bar H2 was a preferred condition for hydrogenation of ZrCo.In addition,it was demonstrated that dehydrogenation at high temperature over 500? was favorable to enable activated ZrCo to own high hydrogen capacity.The experimental results suggested that fast and efficient activation of ZrCo could be achieved by one cycle of optimized procedures including initial evacuation,hydrogenation and dehydrogenation.Meanwhile,optimum procedures composed of initial evacuation at 500?,hydrogenation at 100? under 0.8 bar H2 and dehydrogenation at500? under vacuum was highly recommended for fast and efficient activation of ZrCo alloy.2.Effects of temperature and hydrogen pressure on the dehydrogenation behavior and corresponding phase transformation of ZrCoH3It was revealed that various dehydrogenation behaviors would be observed when different initial hydrogen pressures were applied to the temperature-programmed dehydrogenation of ZrCoH3.Under very low initial hydrogen pressure,like 0.01 bar,disproportionation of ZrCoH3 was not observed even up to 650?,whereas the disproportionation happened under higher initial hydrogen pressure,such as 1 bar or 4 bar.The disproportionation reaction during the dehydrogenation process of ZrCoH3 could proceed following two reaction pathways,respectively corresponding to hydriding disproportionation of ZrCo and dehydriding disproportionation of ZrCoH3-x.If sufficiently high hydrogen pressure was applied,the dehydrogenation of ZrCoH3-x to produce ZrCo would be suppressed.Then,dehydriding disproportionation of ZrCoH3-x would happen.Otherwise,the hydriding disproportionation of ZrCo would occur.In addition,the hydrogen pressure?P?–temperature?T?phase boundaries for the dehydrogenation of ZrCoH3,which was established by settling the respectively onset points and end points in the P-T diagram for the formation ZrCo or ZrH2/ZrCo2,could be a guide to avoid the disproportionation for the practical application of ZrCo alloy.Based on the established P-T phase boundaries,the thermodynamic parameters could be successfully calculated for the disproportionation reactions in the ZrCo-H system.3.Investigation on the hydrogen storage properties of full-scale ZrCo bed,Zr0.8Hf0.2Co bed,Zr0.8Ti0.2Co bed and depleted uranium bed with thin double-layered annulus configurationIt was found that all these fabricated beds not only could reach the hydrogen storage target of 17.5 mol but also owned good structural stability.For ZrCo bed,the hydrogen delivery amount was too low to fulfill the requirements of practical application if the average delivery rate was required to hold at 20 Pa·m3/s.Meanwhile,the degradation of cycling property was very serious for ZrCo bed.Experimental results showed that the hydrogen delivery behavior of ZrCo bed was obviously affected by the operation conditions.For example,operation of employing extra buffer vessel and scroll pump could not only promote the hydrogen delivery process but also reduce the possibility about disproportionation of ZrCo and the risk of the bed involving high pressure at high temperature.Compared with ZrCo bed and Zr0.8Hf0.2Co bed,Zr0.8Ti0.2Co bed exhibited superior hydrogen delivery properties in terms of higher hydrogen delivery amount,faster delivery rate and better cyclic delivery performance,which could deliver 17.06 mol H2 at450°C within 31.8 min holding at the critical delivery rate of 20 Pa·m3/s.It was shown that the delivery rate target could be reached by the Zr0.8Ti0.2Co bed.For depleted uranium bed,it was found that not only hydrogen delivery amount as high as 16.5 mol?94%of recovery amount?but also an average delivery rate of 20 Pa·m3/s could be obtained at 450?,even though the hydrogen delivery time of the bed reached as long as 30.9 min.Meanwhile,the fabricated depleted uranium bed also exhibited outstanding cyclic hydrogen recovery/delivery performances.Deterioration in both hydrogen recovery/delivery amount and rate was not observed even up to 10 cycles.The experimental results suggested that the fabricated depleted uranium bed was technically feasible to be applied to hydrogen isotopes recovery and delivery in the International Thermonuclear Experimental Reactor. |
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