- Build strongly improved version of RPV-1 (RPV-2) and to complement it by a module aimed at simulating the irradiation-induced evolution of fracture toughness properties of RPV steels.
- Build a new Virtual Reactor enable to simulate irradiation effects in stainless steels (INTERN-1) and to complement it by a module aimed at simulating the Irradiation Assisted Stress Corrosion Cracking (IASCC) behavior of these steels.
These tools will rely on the state of the art of physics and mechanics and will be developed in a “Software Integration Platform” under Quality Assurance. They will be usable by a large community : nuclear organizations, manufacturers, utilities, regulators, universities,…
The work required to build, validate and disseminate the proposed simulation tools has been structured in 6 sub-projects.
- RPV & Internals: Physics Modeling
- Mechanics modeling
- Internals : Mechanics & Corrosion modeling
- Users Group
SCK•CEN is one of the major partners in PERFECT project, it contribute to all of each of the above mentionned sub-projects.
SCK•CEN is member of the executive committee Board.
SCK•CEN contributes to select the appropriate codes, develop computer programs, provide database for the validation of specific codes.
3. RPV & Internals : Physics Modelling
WP II-1 “RPV and Internals: Ab initio calculations & potentials” (EDF, CEA, SCK•CEN, CNRS-LMPGM, UKAEA, EDINBURGH: coordination SCK•CEN)
In this WP, SCK•CEN contributes mainly on:
- Determination of inter-atomic potentials: inter-atomic potentials are analytical functions employed to determine the interaction forces between atoms as well as the energy of any configuration of atoms. They are the key elements governing the quality of numerical simulation at the atomic scale.
Also, the current inter-atomic potentials will be parameterized so as to simulate Mn, Ni, Cr, C, P, He atoms.
WP II-2 “RPV: Displacement cascades & short term evolution” (EDF, CEA, SCK•CEN, ULB, LPOOL, UPC)
SCK•CEN will perform the following tasks:
- Characterizing the properties of the residual point defects clusters. These properties will be used in the code simulating the long term evolution of hardening defects.
- For short term evolution of residual defects, the elementary phenomena (diffusion of solute atoms, …) will be simulated with “Atomic Kinetic Monte Carlo” (AKMC). The main tasks will consist in upgrading the AKMC code to introduce solute atoms (Cu, Ni, Mn, C) as well as specific behaviors of point defects (diffusion recombination, elimination to sinks, point defect cluster,…). This code will be mainly used to simulate phenomena occurring within the grains.
WP II-3 “RPV : Long term evolution of irradiation induced damage” (EDF, CEA, SCK•CEN, CIEMAT, VTT, FZR, NRI, CNRS-GMP, CUP, UPM, Chalmers, SUTB, EPFL): Coordination SCK•CEN
The main tasks of of SCK•CEN in this WP will be the following:
- Collecting available experimental data for validation of the proposed tools and models.
- Performing complementary quantitative micro-structural characterizations of irradiated RPV steels. The objective is to get a precise description of the irradiation-induced hardening defects and segregation by merging complementary advanced characterization methods: Transmission Electron Microscopy (TEM), with image simulation, Energy Dispersion Spectroscopy (EDS) associated to field Emission Gun Scanning Transmission Electron Microscopy (FEGSTEM,) Atom Probe Field Ion Microscopy (APFIM), Small Angle Neutron Scattering (SANS) and Positron Annihilation Spectroscopy (PAS). These techniques will be applied on a selected set of model alloys with increasing complexity and steels, western and VVER type, irradiated by neutrons or charged particles.
- Benchmarking results of simulations of irradiation-induced damage against experimental data.
WP II-4 ‘”RPV: Discrete Dislocation Dynamics” (EDF, CEA, SCK, , LPOOL, )
The main tasks of the WP will consist in:
- Parameterizing the Dislocation Dynamics code on RPV steels.
- Characterizing quantitatively the interactions between dislocation and irradiation-induced hardening defects.
- Collecting existing experimental data on irradiated RPV steels.
WP II-6 “Internals: Long term evolution of irradiation induced damage” (EDF, CEA, SCK-CEN, VTT, UAAP)
The main tasks of the WP will be the following:
- Collecting available experimental data for validation of the proposed tools and models.
- Performing quantitative micro-structural characterizations of the austenitic steels used for post irradiation crack growth testing within the Sub-Project “Internals - Corrosion and Mechanics”. These materials will be examined by FEGSTEM for intra-granular characterization of microstructure and grain boundary segregation.
- Selection of the best codes for implementation in INTERN-1.
4. Mechanics modeling
WP III-1 “Models of microcrack nucleation” (EDF, CEA, SERCO, VTT, FANP, FZR, NRI, AEKI)
The WP will (i) establish microcrack nucleation criteria for relevant unirradiated and irradiated steels; (ii) propose distributions of microcracks as a function of relevant parameters. The nucleation criteria will be used in the models of brittle fracture behavior considered in WPIII- 2 and WPIII- 3.
WP III-2 “Models of brittle fracture behavior” (CEA, EDF, SCK-CEN, SERCO, JRC-IE, VTT)
The WP will develop improved criteria for crack propagation by transgranular cleavage and brittle intergranular fracture and recommend which of the various fracture models considered are to be developed further within the Sub-Project.
WP III-3 “Implementation and application of fracture models” (VTT, EDF, CEA, SCK-CEN, SERCO, FANP, FZR, NRI, AEKI, BZI)
The WP will extend current models of fracture behavior and provide the methodology for their use in WPIII- 5 to predict the fracture behavior of irradiated RPV.
WP III-4 “Characterization of irradiated RPV steels” (FZR, CEA, SCK-CEN, JRC-IE, VTT, FANP, NRI, AEKI)
The WP will collect existing data on irradiated RPV steel so as to provide a comprehensive characterization of the flow and fracture toughness properties of irradiated RPV steels in support of the modeling work carried out under WPIII- 3 and WPIII- 5. It will carry out the required complementary tests.
5. Internals : Mechanics & Corrosion modeling
WP IV-0 “Sub-Project Technical Coordination” (SCK•CEN)
WP IV-1 “Internals: Mechanistic and Engineering Framework” (SERCO, CEA, SCK•CEN, CIEMAT, VTT, FANP)
This WP will act as a scientific and technical co-coordinator between the different WPs and the “Outside World". Its main tasks will be:
- Identification, from existing laboratory and industry knowledge, of the key physical and chemical mechanisms to be addressed in the other WPs. It will provide the mechanistic scenario for the Sub-Project.
- Collection of existing data required to validate the proposed codes and models.
- Critical evaluation of results generated within the Sub-Project.
- Benchmark against experimental data of models and numerical tools developed in the other WP’s.
- Preparation, with the Sub-Projects “Integration” and “Users Group”, of a benchmark on an engineering application.
WP IV-2 ”Internals: Environment Chemistry” (SCK•CEN, CEA, SERCO, NRI, VUB )
This Work-Package will produce a numerical tool to simulate them; its main tasks will consist in:
- Coupling two commercial codes (MIOTRAS & PIRODE) to get a first estimate of the local water chemistry from the bulk chemistry and local parameters (geometry, temperature, flow…).
- Experimentally measuring parameters characterizing the modification of the local chemistry due to the presence of the material.
- Theoretically and experimentally assessing the modification of the local chemistry due to neutron irradiation (radiolysis effect).
- Benchmarking simulation results against experimental data get by exposure of artificial cracks and crevices to PWR environment representative of internal's situations. In-situ measurement inside these set-ups and post-exposure analysis of their surfaces will be performed.
WP IV-3 “Internals: Behavior of Irradiated Material” (VTT, CEA, SCK•CEN, CIEMAT)
Its main tasks will consist in:
- Development of FEM methods to describe the behavior of cracked bodies of irradiated stainless steel. The developments to be made are the FEM description of cracked bodies, taking into account the difference in behavior between grain interior and grain boundary.
- Verification of the FEM model by performing finite element simulations to determine local stress, strain and strain rate distribution in cracked bodies of assessment of the influence of the environment on the mechanical behavior. This will include the assessment of the environmental influence on cracking resistance and cracking mechanism transitions as well as the study of the interaction between deformation and the surface layer, formed in LWR environment.
WP IV-4 “Internals: Crack Propagation” (CEA, SCK•CEN, SERCO, CIEMAT, FANP,VTT,ARMINES)
In this WP, simulation tools shall be developed to describe the growth at multi-scale level:
- On the microscopic scale, modeling of the modification of the mechanical state at the crack tip (determined in WPIII-3) due to the presence of corrosion induced vacancies and/or hydrogen.
- On the mesoscopic scale, simulation of the crack advance in multi-grain array (code CASTEM) from the external load and crystallographic orientation of grains.
- Macroscopic modeling, using FEM for modelling the material (WP IV-3) and the environment (WP IV-2), will be linked to the micro- and meso-scopic modeling of stress corrosion cracking in order to provide a macroscopic crack propagation model.
- Determination of a crack advance criterion based on macroscopic modelling and experimental data.
- Benchmarking with experimental results obtained on both irradiated, unirradiated and model materials.
WP IV-5 “Internals Crack Initiation” (FANP, CEA, SCK•CEN, SERCO,VTT, CIEMAT, AEKI, VUB)
The initiation of cracks in LWR relevant conditions will be addressed from different viewpoints:
- Deterministic modeling of process, related to nucleation of cracks: these involve the (electro)chemical, physical and mechanical phenomena related to stability of the surface layer of materials, exposed to the environment (related to WP V-2 and WP V-3).
- Experimental parameterization of these deterministic models in relevant environment.
- Description of growth and coalescence of micro cracks, taking into account the statistical nature of these processes.
- Experimental characterization of crack initiation in LWR conditions; given the exploratory nature of this work, the scope of experiments will be limited to evaluating selected single variable trends.
6. Users Group
SCK•CEN is active in this group, by providing key data , participating in the common exercise and als co-organising training activities.