IRRADIATION CREEP OF VARIOUS FERRITIC ALLOYS IRRADIATED AT SIMILAR-TO-400-DEGREES-C IN THE PFR AND FFTF REACTORS

Irradiation creep of three ferritic alloys at similar to 400 degrees C has been studied. Specimens were in the form of pressurized tubes. In a joint US/UK creep study, two identical sets of creep specimens cons tructed from one heat of HT9 were irradiated in fast reactors, one in the Prototypic Fast Reactor (PFR) and the other in the Fast Flux Test Facility (FFTF). The specimens in PFR were irradiated to a dose of sim ilar to 50 dpa, whereas the specimens in FFTF were irradiated to a dos e of 165 dpa. The observed swelling and creep behavior were very diffe rent in the two reactors. Creep specimens constructed from D57, a deve lopmental alloy ferritic alloy, were also irradiated in PFR to a dose of similar to 50 dpa. Creep behavior typical of previous studies on fe rritic alloys was observed. Finally, creep specimens constructed from MA957, a Y2O3 dission-hardened persion-hardened ferritic alloy, were i rradiated in FFTF to a dose of similar to 110 dpa. This alloy exhibite d a large amount of densification, and the creep behavior was differen t than observed in more conventional ferritic or ferritic-martensitic alloys. (C) 1998 Elsevier Science B.V. All rights reserved.