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Laurence Luneville1 David Simeone1 Jean-Christophe Sublet2

1, CEA, Gif sur Yvette, , France
2, IAEA, Vienna, , Austria

The recent nuclear evaluations describe more accurately the elastic and inelastic neutron-atoms interactions
and allow calculating more realistically primary damage induced by nuclear reactions. Even if
these calculations do not take into account relaxation processes occurring at the end of the displacement
cascade (calculations are performed within the Binary Collision Approximation), they can accurately
describe primary and recoil spectra in different reactors opening the door for simulating aging of nuclear
materials with Ion Beam facilities. Since neutrons are only sensitive to isotopes, these spectra must be
calculated weighting isotope spectra by the isotopic composition of materials under investigation. To
highlight such a point, primary damage are calculated in pure Ni exhibiting a meta-stable isotope produced
under neutron flux by inelastic neutron-isotope processes. These calculations clearly point out
that the instantaneous primary damage production, the displacement per atom rate (dpa/s), responsible
for the micro-structure evolution, strongly depends on the 59Ni isotopic fractions closely related to the
inelastic neutron isotope processes. Since the isotopic composition of the meta-stable isotope vanishes
for large fluences, the long term impact of this isotope does not largely modify drastically the total dpa
number in Ni based steels materials irradiate in nuclear plants.

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