Positive safety impact of ignitor design modifications

Ignitor is a proposed compact high-magnetic field tokamak aimed at studying plasma burning conditions in deuterium–tritium plasmas. A design revision of the ignitor project lead to the substitution of the graphite tiles with molybdenum ones. The consequences of this substitution from the radiological risk and environmental impact viewpoints are examined, applying a computational model for tritium inventory estimate and for activation calculation. It turns out that the global tritium inventory in the machine is almost halved by this design modification, due to a practically negligible tritium inventory in Mo. Activation of Mo is higher that that of C, however, it remains moderate. Because of this, some of the most relevant accidental sequences see a reduction of releases and of doses to public, due to radioactive source terms reduction. Graphite substitution with Mo in the first wall has therefore a global positive effect on the machine radiological safety.