The influence of argon cryotrapping agent on ITER fuel cycle design

• Published in: Fusion engineering and design 1991-12, Vol.18, p.85-90
• Main Authors: Murdoch, D.K., Boissin, J.C.
• Format: Article
• Language: English
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/0920-3796(91)90112-4

The torus evacuation pumping process adopted for ITER fuel cycle design integration studies involves the cryotrapping of helium ash in a continuously deposited frost layer. This design circumvents uncertainties over the long-term integrity and tritium retention of solid sorbents for helium cryopumping, and the issue of scale-up, tritium compatibility and tolerance of operational setups in the case of magnetic bearing turbomolecular pumps. Argon has been selected as cryotrapping agent because of its chemical inertness (resulting in tritium compatibility), and manageable neutronic characteristics. Nevertheless torus exhaust gas processing is complicated by (1) the similarity of the freezing temperature of argon and tritiated impurities (particularly methane), (2) the relatively large flow of argon required, and (3) neutron activation (argon-41 production). The paper reviews the influence of argon on the primary vacuum pump design, describes briefly the system for separation of the argon from the plasma exhaust stream and outlines a strategy for reusing the partially purified argon as cryotrapping medium. The effects of residual quantities of argon in the feed to the fuel clean-up loop are discussed.