SPECIMEN SIZE EFFECTS ON THE CRACK GROWTH RATE RESPONSE OF HIGHLY IRRADIATED TYPE 304 STAINLESS STEEL

摘要

Crack growth rate (CGR) testing was performed onfour compact tension (CT) specimens of two differentsizes (B=8mm and B=19 mm), machined from a Type 304stainless steel (SS) baffle plate at a dose of ~30 dpa. Themain objective was to determine the stress intensity factor(K) validity limit for highly irradiated SS, while anotherobjective was to study the effect of specimen size on theCGR. All testing was conducted in simulated boilingwater reactor (BWR) normal water chemistry (NWC). Thelarge specimen was tested at K in the range 15 to 82MPa√m, whereas the small specimens were tested atstress intensity factors in the range 14 to 36 MPa√m. Thestrain hardening capacity was lost in the highly irradiatedstainless steel tested, and the results indicate that the Kvalidity can be based on ASTM E399 using an effectiveyield strength discounting a portion of the irradiationinduced hardening. Crack branching and out-of-planecracking developed when the limit was exceeded. Therewas no effect of specimen size when testing wasconducted at valid K.