Commissioning of the ESS large-scale 20 K helium refrigeration system for the cryogenic moderator system

At the ESS, a large-scale 20 K helium refrigeration system with a cooling capacity of 30.3 kW at 15 K, which is called Target Moderator CryoPlant (TMCP), has been designed to cool the cryogenic moderator system (CMS) where subcooled liquid hydrogen will be circulated at 1.0 kg/s through four hydrogen moderators where the total nuclear heating is estimated to be 17.2 kW for the proton beam power of 5 MW. The first phase of the TMCP installation and commissioning for the TMCP compressor skids and cold box was completed in 2019. The phase 2 installation of 300 m-long cryogenic helium transfer lines (CTLs) and a valve box located at one end of it in the Target building has been completed in the summer of 2022. Subsequently, the commissioning has been conducted until December 2022. This paper will describe the performance evaluation test results of the CTL heat load and pressure drop, the TMCP cooling capacity, and a test result of a failure action caused by instrument air failure.