Design and indigenous development of fabrication of cryopanels for cryopump applications

Hydro formed cryogenic panels or radiation shield are considered to be one of the most important element in building a reactor of fusion Grade. The panels have several applications e.g. cryo pump shields, radiation shield for vacuum vessel to protect TF coils etc. Indigenous fabrication technology to develop such prototype panels to work in the stringent environment of 4K and 80 K cryogens flowing at higher pressures, undergoing a number of thermal cycles with complete leak tightness against Ultra High Vacuum, was taken up addressing all technological barriers. Leak tightness with a pressure of 4 bar was also carried out. Austenitic steel material was taken as the shield plate material to work in fusion tokamak environment. Several joining process available for fabrication were checked for its flexibility cost effectiveness and cleanliness in operation. Various port connections like vertical port, horizontal port, and fish mouth port, inclined port, etc. were tried and definite conclusions were made for successful applications. Hydro-forming with different fluids and different type of die contours were tried and conclusions drawn on area of application and process Panels of different shape and size were designed, CFD conducted to understand its flow behavior, pressure drop, etc. Similarly efforts were taken on design of weld spacing, port size, spot gap for various burst pressure requirements and pressure drop requirements of such panel in operations. Physical prototypes of different shapes and sizes, different bubble geometry, port connections, thickness were made and conclusions drawn on process limitations, quality control points etc. Various tests were conducted at the end of fabrications of such prototypes which includes vacuum leak tests, mechanical and material tests, and thermal cycling after subjecting to cryogenic temperatures. The successful panel is thus shown in details in this paper with all technical details of design, fabrication procedures, testing and performance. The work has been carried out by the support of Board of Research for Fusion Science and Technologies (BRFST) under, Govt. of India.