Research Themes

The research is structured to deliver our vision of structural integrity undertaken on a faithful digital representation of safety-critical components. To demonstrate relevance to, and validate our approach, we will focus on key features in current operational plant where failures most often occur. Major areas that are addressed in the programme lie in:

  • (a) the predictive capability associated with the entry-into-service condition (particularly joining processes)
  • (b) in-service degradation modelling (particularly at the meso scale)
  • (c) methods to translate advanced microstructurally-informed models into practical tools for
    design and integrity assessments.

They will be addressed in work packages (WP) 1,2, and 3 respectively.

WP 1: Entry to service condition
WP 2: In-service materials behaviour
WP 3: Implementation and lifetime assessment

WP1 – Entry to service condition

Output: continuum and meso-scale weld models of austenitic and ferritic steels The entry-into-service state of a weldment comprises features at several length scales: geometry, distortion and defects, residual stresses and cyclic plastic hardening, grain morphology and texture, microconstituent and precipitate distributions, and chemical segregation. All will affect in-service behaviour and their development is driven by the rapid, transient thermal loading associated with welding.

WP1 defines this entry-into-service state, via both modelling (WP1a) and scale-appropriate testing (WP1b).

WP2 – In-service materials behaviour

Output: meso-scale model of common damage mechanisms seen in power plants There are a number of key damage mechanisms experienced by nuclear plant during service. Common mechanisms of most interest to EDF include fatigue, cleavage fracture; ductile failure; creep and creep fatigue; and corrosion-fatigue. The damage models currently used capture degradation at a continuum level (e.g. critical energy release rates, void nucleation/growth/coalescence) as this was previously the only approach available to produce lifetime assessment.

WP2 is thus intended to expand Crystal Plasticity functionality to consider the degradation of complex microstructures in-service environments. This work will allow us to simulate the influence of microstructural features in degradation – capturing, for example, the role of carbides in cleavage, second-phase particles in void growth, and grain boundaries in corrosion.

WP 3: Implementation and lifetime assessment

Output: open-source reduced engineering models of welding and damage, probabilistic integrity assessment The validated models of entry-into-service condition (WP1a) and in-service degradation (WP2a) are tuned to key material properties over a range of length scales. As such, a variety of modelling techniques (e.g. continuum, CP, phase field) are used to capture material behaviour with a common aim: to improve component lifetime estimates.

WP3 is intended to both reduce the computational expense of the models produced, and harmonise the digital architecture used by these models to support future applications.