6.4 Lifetime and fatigue

Because the beamline component will become activated during the operation of the reactor, any maintenance or exchange of the components will have to be done remotely, and all such operations will be very difficult. That consideration leads to the requirement that all the components must be designed to have an expected life that is longer than that of the reactor, for example, with a fatigue life of >40 years. The calorimeter of the injectors of a reactor will "see" a similar thermal load to that of the calorimeter of the ITER injectors, even though the accelerated current density is reduced by 50% of that expected with the ITER system. The ITER calorimeter design was extremely challenging, and it is unlikely that the design of the calorimeter of the injectors on a reactor will be significantly better. The calorimeter of the ITER injectors has a calculated fatigue life of 7.5 <sup>10</sup><sup>4</sup> thermal cycles, and R&D is needed to meet the full fatigue lifetime requirement which could be <sup>≈</sup><sup>5</sup> <sup>10</sup><sup>5</sup> , i.e. 8 times higher.
