Hydriding/dehydriding characteristics on fast heat transfer response ZrCo bed for ITER

Abstract Three models of fast heat transfer response ZrCo hydride bed were tested to examine their hydriding and dehydriding performance, and the hydrogen retention of the ZrCo during multiple hydriding and dehydriding operation. The design features of the present models are (i) very thin layer (3 mm) of ZrCo powder packing, (ii) large heating area in contact with the ZrCo powder (2.04 cm 2 /g-ZrCo), and (iii) large filter surface area (1.76 cm 2 /g-ZrCo) to reduce pressure drop across the filter during hydrogen delivery. To evaluate pumping conductance effect during dehydriding with vacuum pumping, two sizes of hydrogen pumping line were applied. Extremely high delivery rate of 1.3 × 10 −2  Pam 3 /s for 90% delivery was observed in the 2nd and 3rd model tests. Hydrogen retention of ∼1.5 × 10 −2  L-STP/g-ZrCo (∼2 L-STP/bed model) was observed in all models after multiple repetitions of hydridings and dehydriding under vacuum pumping: 25 cycles (1st model), 14 cycles (2nd model) and 70 cycles (3rd model). It was experimentally confirmed that the differences in the delivery rate and hydrogen retention the three model beds were predominantly generated by the difference in the pumping conductance (effective pumping speed) in the delivery pipeline.