Thermal behaviour of ZrCo getter beds during hydrogen absorption at variable flow rates and concentrations

• Higher H 2 concentration/flow over ZrCo bed leads to higher absorption rate and higher peak temperature. • Higher flow drives temperature higher than a lower flow since more H 2 is arriving/ sec . • The peak bed temperature remains well below 400 °C even under pure high H 2 /flow. • Absorption is temperature driven and the peak temperature tracks the reaction time roughly exponentially. • ZrCo H 2 absorption capacity remains essentially constant over ∼ 40 cycles indicating good durability. • Based on the experimental results showed in this study, it is confirmed that ZrCo shows a stable hydrogen absorption performance, working under the operating conditions investigated in this study. Zirconium-cobalt alloy (ZrCo) is one of the most studied getter materials for the storage, supply, and recovery of hydrogen isotopes. However, the exothermic nature of the hydridation reaction has always raised concerns regarding local overheating, which might compromise the getter stability, particularly at high H-concentrations and/or high flow rates. In this work, the thermal behaviour of a ZrCo getter bed upon hydrogen absorption was experimentally assessed under controlled conditions in the HYDE loop facility installed at the Tritium Laboratory Karlsruhe (TLK). Successive loading–deloading cycles were performed on 30 g of ZrCo with H 2 /He mixtures ranging from 1 % to 11 % H 2 under both low (40–100 Ncm³/min) and high (300–500 Ncm³/min) H 2 flow regimes. A linear relationship (R² ≈ 0.99) was observed between the H 2 concentration in helium and the maximum temperature reached by the getter material during absorption, regardless of the helium dilution rate. The temperature increased from 68 °C at 1 % H 2 (low flow) to 258 °C at 11 % H 2 (high flow). The reproducibility of the experiments in terms of absorption capacity with nearly 40 experimental cycles also confirms that the material remains stable, with an average H/ZrCo ratio of ∼ 2.80 ± 0.06. These results show that under DEMO-relevant operating conditions (<0.1 % H 2 in helium), the peak temperature that can be reached by the ZrCo getter should be moderate, and it is not expected to be a matter of concern or to jeopardise the getter material stability.