Study on decay heat removal of compact ITER

Since fusion power and neutron fluence of the compact ITER has been reduced, thermal transients due to decay heat of the tokamak components such as in-vessel components and vacuum vessel (VV) were numerically analyzed for the purpose of identifying the necessity of cooling function as the safety measure. The result shows that the maximum VV temperature remains around 500 °C even under the extremely hypothetical conditions, assuming that all the coolants in the VV and in-vessel components are lost instantaneously. In addition, the maximum temperature appears after about 100 days and hence reducing the temperature rise can be practically achieved during such a long grace period. As a whole, it has been clarified that the decay heat removal can be passively achieved by only radiation without any active cooling measures. This paper describes the analysis results on thermal transient due to decay heat, including sensitivity study on the effect of heat connection and removal characteristics on the temperature rise.