Influence of thermally induced secondary stresses on the lifetime of high temperature reactor components

The metallic components of a high-temperature reactor with operating temperatures above 880°C have to be ensured against the, in comparison to primary stresses, respectively higher secondary stresses due to loading transients. For the calculation of the damage accumulation due to primary, secondary and peak stresses, elastic methods are used in the temperature region up to 800°C. These elastic methods are too conservative at temperatures above 900°C. Therefore a simplified inelastic method is shown for calculation of the creep damage of a reformer tube with operating temperatures at about 900°C under start-up and shut-down loadings. With this method a design is possible for the calculated start-up and shut-down transients during the lifetime of the component.