Low cycle fatigue testing of Inconel 600 and life assessment of JET vacuum vessel

Low cycle/high strain fatigue tests at 300°C have been carried out on specimens of Inconel 600 to assess the life of critical parts of the JET (Joint European Torus) vacuum vessel. Specimens have been loaded with alternate cycling strain up to ±1%. The shape of some specimens has been chosen to reproduce the real working conditions and the stress distributions. The results of the tests have been used to evaluate the actual damage produced by plasma disruptions in the past operational campaigns and to predict the additional damage caused by the expected future operational phases of JET. The critical regions of stresses and the maximum strain value for reference disruption scenarios have been evaluated. A statistical analysis of the measured vessel displacements for the past four years of operation has been carried out. It shows that the accumulated fatigue damage in the critical part is no more than a few percent. Anticipated total damage for another five years is less than 1/3 of the fatigue failure obtained from the tests