Tritium safety consideration in the design of tritium systems for China HCSB and DFLL TBMs

The main goal of an international thermonuclear experimental reactor (ITER) test blanket module (TBM) is to test the feasibility of tritium production and extraction. China has designed two types of TBMs to put in a whole test port, which are the helium-cooled solid breeder (HCSB) TBM and the dual-function lithium lead (DFLL) TBM. A set of common tritium processing systems was designed for the two types of TBMs, including the tritium extraction system (TES), the helium coolant system and the coolant purification system (CPS). Tritium in the TBMs and the ancillary systems should be controlled for the sake of radiological safety. The design of a few key parameters, such as the partial pressures of tritium in the coolant and above the breeder, the flux of carrier gas for tritium extraction, the efficiency of tritium extraction, the selection of the structure material together with the surface coating, etc., depend on the structure of the TBMs and the control of tritium release into the environment. A set of calculation models, based on the tritium mass balance among the TBMs, and different ancillary systems were developed to appraise the tritium safety in the common tritium systems and the Chinese TBMs. A tritium permeation barrier coating on the structure material of some components, a double-wall design for some tritium containers, and the establishment of a glove-box atmosphere detritiation system (GDS) are all necessary to control the release of tritium into the environment.