Title: Integrated Modeling of Second Phase Precipitation in Cold-Worked 316 Stainless Steels under Irradiation,
Abstract: The current work combines the Cluster Dynamics (CD) technique and
CALPHAD-based precipitation modeling to address the second phase precipitation
in cold-worked (CW) 316 stainless steels (SS) under irradiation at 300-400 C.
CD provides the radiation enhanced diffusion and dislocation evolution as
inputs for the precipitation model. The CALPHAD-based precipitation model
treats the nucleation, growth and coarsening of precipitation processes based
on classical nucleation theory and evolution equations, and simulates the
composition, size and size distribution of precipitate phases. We benchmark the
model against available experimental data at fast reactor conditions (9.4 x
10^-7 dpa/s and 390 C) and then use the model to predict the phase instability
of CW 316 SS under light water reactor (LWR) extended life conditions (7 x
10^-8 dpa/s and 275 C). The model accurately predicts the gamma-prime (Ni3Si)
precipitation evolution under fast reactor conditions and that the formation of
this phase is dominated by radiation enhanced segregation. The model also
predicts a carbide volume fraction that agrees well with available experimental
data from a PWR reactor but is much higher than the volume fraction observed in
fast reactors. We propose that radiation enhanced dissolution and/or carbon
depletion at sinks that occurs at high flux could be the main sources of this
inconsistency. The integrated model predicts ~1.2% volume fraction for carbide
and ~3.0% volume fraction for gamma-prime for typical CW 316 SS (with 0.054
wt.% carbon) under LWR extended life conditions. This work provides valuable
insights into the magnitudes and mechanisms of precipitation in irradiated CW
316 SS for nuclear applications.