Design of a two-stage cryopump with hydrogen-helium separation capability for fusion reactor application

Abstract

During the regeneration process of the torus cryopumps in CFETR, separating the majority of unburned fuel from desorbed gas mixture can increase fuel recycling efficiency. Given this situation, this paper proposes a two-stage cryopump concept with hydrogen–helium separation capability, based on the differences in cryosorption and cryocondensation capabilities between metal cryopanels with and without activated charcoal coating treatments for hydrogen, helium, and other gases. Subsequently, finite element simulations were conducted to analyse parameters of the designed cryopump, including thermal load, cryopanel temperature, and pumping speed. The simulation results demonstrated that the radiative thermal load on the cryopanels was relatively uniform, confirming the effectiveness of the thermal shield design. Under liquid helium(LHe) cooling conditions, the average temperature of the cryopanels remained stable below 5 K, indicating excellent cooling performance. In the molecular flow regime, the two-stage cryopump achieved a maximum pumping speed of 35 m³/s with a hydrogen–helium separation efficiency of approximately 99 %, thereby validating the feasibility of the proposed concept and design. Based on the design and analysis, a prototype of the two-stage cryopump was developed, and a testing platform was established to evaluate its pumping performance. Test results revealed that the two-stage cryopump achieved a pumping speed of approximately 100 m³/s, which closely meets the expected pumping speed requirements for cryopumps in the divertor region of fusion reactors. The proposal and engineering implementation of the two-stage cryopump concept present an approach to the hydrogen–helium separation and rapid fuel cycling in future fusion reactor.