Radiation and Thermomechanical Degradation Effects in Reactor Structural Alloys

Identifying Limitations of ASME Section III Division 5 For Advanced SMR Designs

“…This increase of strength is typically most pronounced below a characteristic material-and dose ratedependent temperature. Above this characteristic temperature, the radiation hardening diminishes with increasing temperature [33] as indicated in Figure 4.2 for Alloy 617 and Alloy 800H [36].…”

“…Since the rate-controlling energies for these processes are approximately proportional to the material's melting point, the transition temperature between different irradiation degradation mechanisms can be approximated by using homologous irradiation temperature (T/TM, where TM is the melting temperature) [33]. Figure 4.1 summarizes the approximate temperature regimes where different irradiation degradations are most pronounced in structural metallic alloys.…”

“…For most materials, the irradiation hardening at a given dose is either nearly constant or decreases slowly with increasing temperature below the characteristic temperature [33]. In some materials, however, a localized peak in irradiation hardening can occur at an intermediate temperature.…”

Initial development for the introduction of provisions for irradiation effects in Division 5 rules

“…The approximate temperature ranges where these phenomena are dominant are shown in Figure 3.1, following Zinkle et al [2]. Here / is the homologous temperature.…”

“…Approximate temperature regimes where different phenomena caused by irradiation are most prominent in structural alloys, schematic after[2]. The highlighted regions correspond to room temperature to 700F and 700 to 1200F for Grade 91 steel.…”