Influence of Test Temperature on Post Irradiation, High Temperature Tensile and Creep Properties of X8CrNiMoNb16 16, X10NiCrAlTi32 20 (Alloy 800) and NiCr22Fe18Mo (Hastelloy X)

To extend the database of potential HTGR control rod tube materials, three austenitic alloys X8CrNiMoNb16 16, X10NiCrAlTi32 20 and NiCr22Fe18Mo were irradiated in the form of tensile and creep test specimens at 400, 500 and 600 deg C to a thermal neutron fluence of 3 x 10 exp 25 m exp --2 . The main aim was to quantify the influence of the irradiation temperature on the materials' short-term mechanical properties between RT and 900 deg C, but additional information should be gained regarding the possible influence of neutron spectra, the materials' high temperature notch sensitivity and the influence of upset temperatures on the materials' high temperature embrittlement. The irradiation behaviour, especially of Alloy 800, is very complex. Both strength and ductility values between RT and 800 deg C are influenced by the irradiation temperature, and in case of the unirradiated controls, by the annealing temperature, an indication for intricate precipitation behavior. The high temperature embrittlement can be very severe and was already evident at test temperatures of 400 deg C. There are indications that a high-energy neutron spectrum increases the materials' strength values in tensile testing. Graphs. 8 ref.--AA