Abstract
Nuclear plant life extension to 80 years will require accurate predictions
of neutron irradiation-induced increases in the ductile-brittle transition
temperature (ΔT) of reactor pressure vessel (RPV) steels at high fluence conditions
that are far outside the existing database. Remarkable progress in mechanistic understanding of irradiation embrittlement has led to physically motivated ΔT correlation models that provide excellent statistical fi ts to the existing surveillance database. However, an important challenge is developing advanced embrittlement models for low fl ux-high fl uence conditions pertinent to extended life. These new models must also provide better treatment of key variables and variable combinations
and account for possible delayed formation of “late blooming phases” in low copper steels. Other issues include uncertainties in the compositions of actual vessel steels, methods to predict ΔT attenuation away from the reactor core, verifi cation of the master curve method to directly measure the fracture toughness with small specimens and predicting ΔT for vessel annealing remediation and re-irradiation cycles.