Structural Materials

The Structural Materials expert group focusses on the evaluation and prediction of the behaviour of structure materials in nuclear installations.

Activities

  • The selection, specification and validation of materials for new applications in nuclear installations.
  • The evaluation of ageing effects on the physical, chemical and mechanical properties of materials.
  • The assessment of the impact of the material property evolution on integrity of components of nuclear installations.

Applications

The current scope of applications is centered around 3 fields:

  • The embrittlement of steels, used for reactor pressure vessels in current light water reactors (LWRs), due to neutron irradiation.
  • The degradation of austenitic stainless steels and nickel base alloys due to stress corrosion cracking and/or irradiation in LWR environments.
  • The behaviour of martensitic steels and high temperature alloys that are candidate materials for application in advanced fission and fusion reactor concepts.

Typically, the above-mentioned applications are tackled on different levels:

The fundamental level, where the effect of irradiation and ageing is described through modelling of the physical processes that take place in the material, from the atomistic scale up to the scale of a single grain. This activity yields fundamental insight in the parameters governing the development of the microstructure of the material under irradiation and therefore are supported by a range of microstructural investigation techniques.

The continuum level, where the macroscopic behaviour of the material is correlated to the observed changes in microstructure due to ageing and irradiation. At this level, the evolution of material characteristics such as the mechanical behaviour is linked to the observed modification of the microstructure. These activities are supported by functional testing of materials during the course of the ageing process.

The industrial level, where the modification of the material behaviour due to ageing is correlated to the expected behaviour of reator components during their lifetime. At this level, applied research and industrial service are closely related. Inversely, interaction with industry also serves to an improved understanding of the relationship between the component – material manufacturing process, its initial microstructure and behaviour and the evolution of the material during ageing in reactor conditions. This partnership between material producers and research is also targetted to optimise both materials and manufacturing methods for new reactor types and their components.

Collaboration

The Structural Materials expert group works in close collaboration with:

The expert group also makes use of the Fermi computation cluster.

Mechanical and Corrosion Analysis

The mechanical and corrosion characterisation of various reactor materials is required. These tests are performed in the unirradiated and the irradiated condition.

Investigated materials

  • Reactor pressure vessel steels
  • Internals
  • Fuel cladding
  • Material for fusion reactors or advanced systems such as ADS (Accelerator Driven Systems)

Tests

  • Tensile tests
  • Impact tests
  • Fracture toughness tests
  • Fatigue tests
  • Hardness tests
  • Burst tests
  • Swelling tests
  • Creep tests
  • Slow strain rate tensile tests

Test-mechanical-and-corrosion-analysis

Foreground: tested molybdenum round compact tension specimens.
Background: low cycle fatigue specimens and round compact tension specimens mounted on an irradiation rig to be loaded in the BR2 reactor.

Tests are performed according to standard testing methods and/or advanced test techniques. The establishment of a Quality Assurance System has led to the Beltest accreditation of our laboratory (EN 45000).

Commercial or in-house developed equipment is used. In addition to the testing capabilities, the laboratory has a strong technical support from the reactor materials research unit that provides specimen fabrication and reconstitution of non-irradiated and irradiated specimens.

External clients can take contact to establish tailored testing programmes. More information can be found in the section 'Our Services - Mechanical and corrosion analysis'.

Head of Expert GroupKonstantinovic Milan