Concept of calorimetry system for ITER

Abstract

The ITER tokamak is expected to produce up to 500 MW of fusion power. Other energy inputs will contribute up to 100 MW. All of this power ultimately converts to heat and the Tokamak Cooling Water System (TCWS) will remove most of it. To ensure safety, diagnostics methods, including calorimetry, will be used. Thermal methods used in calorimetry are not suitable for online control but rather provide time-averaged or integrated values. The ITER calorimetric system aims to calculate the integrated fusion power after each pulse by determining the total tokamak power using data from the TCWS and other systems involved in the energy transfers. The total fusion power will be then determined by analyzing the thermal balance of the machine. As most of the energy transfers are realised by cooling loops, a general forward model has been developed for their analysis. The system is designed to measure net fusion power production. At approximately 200MW, the accuracy is around 10%, and at about 500MW, the accuracy improves to 3%. The expected time constant of the measured instantaneous value is in order of 40s (the nominal ITER burn times are in the range 300 3000s). System will be most useful in cross-calibration with fast time resolution neutron systems. The developed system will also serve as a model for future tokamak-based fusion power plants, where its accuracy will be even higher. The paper gives a general description of the system concept, with main inputs required and the expected outputs.