IRRADIATION CREEP AND VOID SWELLING OF 2 LMR HEATS OF HT9 AT SIMILAR-TO-400-DEGREES-C AND 165 DPA

Two nominally identical heats of HT9 ferritic-martensitic steel were p roduced, fabricated into pressurized tubes, and then irradiated in FFT F, using identical procedures. After reaching 165 dpa at similar to 40 0 degrees C, small differences in strains associated with both phase-r elated changes in lattice parameter and void swelling were observed in comparing the two heats. The creep strains, while different, exhibite d the same functional dependence on swelling behavior. The derived cre ep coefficients, the one associated with creep in the absence of swell ing and the one directly responsive to swelling, were essentially iden tical for the two heats. Even more significantly, the creep coefficien ts for this bcc ferritic-martensitic steel appear to be very similar a nd possibly identical to those routinely derived from creep experiment s on fee austenitic steels.