1. Reminder of few basic facts about displacements per atom (dpa)
Marco G. Beghi, Politecnico di Milano, Department of Energy

2. displacements per atom (dpa)
mechanical behaviour of structural metals (steels) (embrittlement, swelling, …)
property vs. fluence depends on neutron spectrum, type of particle, …
property vs. dpa collapses in single curve for a given irradiation temperature

3. energetic particle  target
nuclear reactions: transmutations,
gas production (H, He, …)
primary damage: vacancy/interstitial pairs: dpa
(collision cascade)
particle
(dE/dx) ion (elastic collisions)
scattering: dE/dx (stopping power)
metals: heat, no damage
(dE/dx) electron
insulators: also damage (displacements, bond rearrangements, …)
within  ps
independent from temperature

4. strongly temperature dependent
within ps: displacements (dpa) (Frenkel pairs;
some intracascade annihilation
from ps to Ms: evolution of defect population (diffusion, annihilation, coalescence, flow to sinks, …)
evolution of microstructure
evolution of macroscopic properties
‘slow’ evolution
strongly temperature dependent

5. success of dpa approach with steels:
substitutional alloys: Fe-Fe, Fe-Cr, Fe-Ni, … bonds  same
Fe, Cr, Ni, …  same mass
neutron spectra: from keV to MeV
dpa rates not too different
simulation of neutron damage by ions:
tailoring of electron/ion stopping power
dpa rate
with CuCD, MoGr
bonds C-C, Mo-Mo, C-Mo different
C, Mo, Cu different mass