Primary and secondary creep of OFHC copper at various temperatures

• Creep behaviour of OFHC Cu in air atmosphere is analysed. • Creep constant-load tests at 300°C, 400°C, 450°C and 550°C. • The hardening effect is dominant for all stress and temperature levels investigated. • Norton-Bailey estimations are in good agreement with the measured strain rates at all examined temperature levels. • Numerical analyses on EU-DEMO monoblock component are performed to assess the effect of primary creep response. The proper design of reliable high temperature structures for the realization of fusion power plants is a key issue. Therefore, the behaviour of primary and secondary creep of involved materials plays a crucial role. Unfortunately, in the case of the oxygen free high conductivity copper (OFHC Cu), employed for manufacturing some parts of the divertor cooling system, a well consolidated creep constitutive model is still missing. In addition, to the authors’ knowledge, only a limited amount of experimental data on the creep of OFHC Cu, obtained at temperatures quite dissimilar from those expected for in service fusion power plants, are available in the literature. In this work the creep behaviour of OFHC Cu in air atmosphere was analysed under different operating conditions. Creep constant-load tests were carried out at 300°C, 400°C, 450°C and 550°C to measure primary and secondary creep strains. The testing load levels were chosen taking account of the creep design aims of the European Demonstration Power Plant (EU-DEMO) project. Finally, phenomenological laws were proposed to model the creep response of the examined material, and numerical analyses on EU-DEMO monoblock component were performed to assess the effect of primary creep response.