Creep fatigue analysis of DEMO divertor components following the RCC-MRx design code

Abstract

In the DEMO fusion reactor, in-vessel components will be subjected to very high thermo mechanical steady and cyclic loads. A design check that is required by the RCC-MRx code used for nuclear installations and fusion reactors is a creep-fatigue check. The fatigue damage is caused by the pulsed operation of the fusion reactor while creep damage occurs during the hold time of loads at elevated temperatures. The temperature of the main divertor components is kept below that which causes creep by using cooling fluid that flows through channels fabricated within the components themselves. Other components such as the shielding liner and reflector plate supports on the divertor cassette cannot be cooled as such and so their temperature can rise high enough so that they sustain creep damage. In the presence of creep, the fatigue life of a component is reduced. In this work, a creep fatigue assessment of a representative simple geometry is carried out. The representative geometry is that of a thick cylinder under the action of steady and fluctuating loads similar to those seen by DEMO in-vessel components while in service. The cylinder example creep fatigue results are used as a benchmark and compared with those obtained using the creep fatigue assessment (CFA) tool developed at KIT (Karlsruhe Institute of Technology). Methodologies used for creep fatigue assessments within RCC-MRx are presented and explained and results discussed. The work should provide a contribution towards any necessary creep fatigue assessments of DEMO divertor components currently being developed.