Strategy for determination of ITER in-vessel tritium inventory

Tracking of tritium inventories on ITER will be essential to ensure that the safety limits established for the mobilizable tritium inventory in the vacuum vessel are not violated. The large and highly variable flow rate and complex chemical and isotopic composition of the tokamak exhaust stream will compromise the precision of direct flow rate measurements. Thus a complementary procedure to derive the in-vessel inventory at regular intervals is required. The method proposed consists of tracking the transfers of tritium to and from a predefined area of the plant, calculation of tritium inventory changes within that area and periodic measurement of the ex-vessel portion of the total inventory, allowing the in-vessel portion to be calculated by difference.