State of Advancement of the International REVE Project: Computational Modelling of Irradiation-Induced Hardening in Reactor Pressure Vessel Steels and Relevant Experimental Validation Programme

Abstract

The REVE (REactor for Virtual Experiments) project is an international joint effort aimed at developing multiscale modelling computational toolboxes capable of simulating the behaviour of materials under irradiation at different time and length scales. Well grounded numerical techniques such as molecular dynamics (MD) and Monte Carlo (MC) algorithms, as well as rate equation (RE) and dislocation-defect interaction theory, form the basis on which the project is built. The goal is to put together a suite of integrated codes capable of deducing the changes in macroscopic properties starting from a detailed simulation of the microstructural changes produced by irradiation in materials. To achieve this objective, several European laboratories are closely collaborating, while exchanging data with American and Japanese laboratories currently pursuing similar approaches. The material chosen for the first phase of this project is reactor pressure vessel (RPV) steel, the target macrosocopic magnitude to be predicted being the yield strenght increase (Δσy) due, essentially, to irradiation-enhanced formation of intragranular solute atom precipitates or clouds, as well as irradiation induced defects in the matrix, such as point defect clusters and dislocation loops. A description of the methodological approach used in the project and its current state is given in the paper. The development of the simulation tools requires a continuous feedback from ad hoc experimental data. In the framework of the REVE project SCK·CEN has therefore performed a neutron irradiation campaign of model alloys of growing complexity (from pure Fe to binary and ternary systems and a real RPV steel) in the Belgian test reactor BR2 and is currently carrying on the subsequent materials characterisation using its hot cell facilities. The paper gives the details of this experimental programme — probably the first large-scale one devoted to the validation of numerical simulation tools — and presents and discusses the first available results, with a view to their use as feedback for the improvement of the computational modelling.

Nanostructure evolution under irradiation in FeMnNi alloys: A “grey alloy” object kinetic Monte Carlo model

“…This result is in qualitative agreement with what reported by Hoelzer and Ebrahimi in [46], where iron alloys containing nickel were irradiated at 288°C to a fluence of 4.63 Á 10 23 n m À2 ($0.05 dpa) and showed an increase in the relative fraction of loops with ½h1 1 1i Burgers vector, while the reported number density for Fe-0.7Ni was 6.5 Á 10 21 m À3 , i.e. higher than in the Fe-C model alloy irradiated in the REVE experiment under similar conditions [37]. Hoelzer and Ebrahimi ascribed this behaviour to the fact that Ni atoms interact strongly with SIA atoms but weakly with vacancies in a-iron [47], so the nickel-SIA interaction is expected to increase the vacancy annihilation rate and thus reduce the elimination of ½h1 1 1i loops.…”

“…Our simulation conditions were dictated by the reference irradiation experiment from the REVE campaign performed in the in-pile Section 2 of the CALLISTO loop of the BR2 reactor in SCKÁCEN in Mol, Belgium [37]. The irradiation temperature and pressure were maintained constant at about 563-568 K and 15 MPa, respectively.…”

Overview of the RPV-2 and INTERN-1 packages: From primary damage to microplasticity

“…Note also that some convenient quantities are provided to ease the comparison with experimental results: the defect size density, FðRÞ ¼ 4pR 2 Vat Cðn; pÞ as a function of the cluster spherical radius Rðn þ pÞ is also given, the cluster mean radii,…”

“…This includes the development of the numerical or theoretical tools and the experimental validation at the relevant scale. Seminal work to create an integrated tool taking into account the impact of reactor neutron spectrum on the production of defects affecting the microstructure was started in the REVE (REactor for Virtual Experiments) initiative [1][2][3]. From this initiative it appeared that the follow-up of the project had to reduce the empiricism of the models using specific experimental data to calibrate and validate some of the models present in the codes.…”

A not-so-short description of the PERFECT platform

“…During the REVE initiative Jumel et al [7], Malerba et al [10], Jumel and Van-Duysen [8], a first prototype of so-called 'Virtual Test Reactor' (VTR) was developed: RPV-1. This VTR was already based on a chaining of several modules, to predict the increase of critical resolved shear stress due to irradiation.…”