The tritium system of the Ignitor compact tokamak provides for injecting deuterium–tritium mixtures into the vacuum chamber, to sustain the fusion reaction. In particular, in this study by C. Rizzello (Tesi Sas) and S. Tosti (ENEA) in Italy, the design of the Ignitor tritium system has been updated taking into account new technologies proven in other tokamak machines (JET and TFTR) and recent studies carried out in qualified international tritium laboratories.
The Ignitor fuel cycle has been studied for 10 years of operation (both preliminary and operating phases). The main subsystems considered consist of tritium storage and delivery, plasma exhaust and gaseous waste detritiation treatments, and tritium accountability. The requirements of continuous operation, maintenance and safety have been considered; in particular, all main components have been duplicated and the tritiated wastes are mainly produced in the form of hydrides stored in getter beds, thus avoiding the formation of highly contaminated tritiated water. The main components of the tritium storage and delivery system are two getter beds; these devices use an uranium bed, and their tritium content is evaluated by calorimetry.
During the discharges when deuterium–tritium mixtures are used (plasma discharges), the plasma exhaust system separates the hydrogen isotopes by means of a thin-wall Pd–Ag permeator tube, characterized by high hydrogen permeability, complete selectivity and durability. All the tritium present in the gaseous streams coming from the vacuum chamber (except after power discharges) is continuously converted into tritiated water by a catalytic reactor, while the resulting water is collected onto molecular sieves. The process control as well as the assessment of the tritium inventory is performed via tritium measurements; these are carried out by ionization chambers calibrated through gas chromatography and mass spectrometers.
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