September 27, 2017: PhD public defence - Monica Chiapetto - Computer simulation of the nanostructural evolution under irradiation in ferritic alloys - ULille

Name: Monica Chiapetto

Date: September 27, 2017 09:00 h

Venue: 

Université de Lille 1
Cité Scientifique, 59650 Villeneuve-d'Ascq, France
Salle 107 – bâtiment C15

 

Computer simulation of the nanostructural evolution under irradiation in ferritic alloys

In this study, object kinetic Monte Carlo (OKMC) models were developed in order to predict the nanostructure evolution under neutron irradiation in both RPV and F/M steels. These were modelled, respectively, in terms of Fe-C-MnNi and Fe-C-Cr alloys, but the model was also validated against data obtained on a real RPV steel coming from the surveillance programme of the Ringhals Swedish nuclear power plant. The effects of the substitutional solutes of interest were introduced in our OKMC model under the simplifying assumptions of ‘‘grey alloy’’ scheme, i.e. they were not explicitly introduced in the model, which therefore cannot describe their redistribution under irradiation, but their effect was translated into modified parameters for the mobility of defect clusters. The possible origin of low temperature radiation hardening (and subsequent embrittlement) was also investigated and the models strongly supported the hypothesis that solute clusters segregate on immobile interstitial loops, which act therefore as heterogeneous nucleation sites for the formation of the NiSiPCr- and MnNi-enriched cluster populations experimentally, as observed with atom probe tomography in, respectively, F/M and RPV steels. In other words, the so-called matrix damage would be intimately associated with solute atom clusters and precipitates which increase their stability and reduce their mobility: their ultimate effect is reflected in an alteration of the macroscopic mechanical properties of the investigated alloys. Throughout all our work the obtained results have been systematically validated on existing experimental data, in a process of continuous improvement of the physical hypotheses adopted. 

 

Promotors:
  •  (ULille) Charlotte Becquart
SCK•CEN mentors:
  • Lorenzo Malerba
  • Nicolas Castin

Click here for a list of obtained PhD degrees.