For EAST operation schedule, auxiliary subsystems like the cryogenic system have to cope with different heat loads which depend on the different EAST operating states. The cryogenic system consists of a cryoplant and a cryodistribution system. All of these cryogenic subsystems have to operate in parallel to remove the heat loads from the magnet, 80K shields, built-in cryopumps and other small users. After a brief recall of the main particularities of a cryogenic system operating in a Tokamak environment, the first part of this study is dedicated to the assessment of the main EAST operation states. A new design of refrigeration loop for the HTS current leads, the updated layout of the cryodistribution system and revised strategy for operations of the built-in cryopumps have been taken into consideration. The relevant normal operating scenarios of the cryoplant are checked for the typical EAST operating states like plasma operation state, short term stand by, short term maintenance, or test and conditioning state. The second part of the paper is dedicated to the abnormal operating modes coming from the magnets and from those generated by the cryoplant itself. Thanks to this analysis, the optimization of the present operational modes is proposed to make match the technical specifications of the cryogenic system with the EAST operation requirements.

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