Fuels, Reactors and Reprocessing

The Fuel, Reactors & Reprocessing capability consists of three teams providing technical support (commercial work, R&D, nuclear foresight & advice) to a wide range of customers including the UK government.

Post Irradiation Examination – Metallography

The PIE Metallography team is comprised of PIE Technicians, a Deputy Delivery Manager, Microscopists, Deputy Technical Leads and a Technical Lead and Team manager. They work together to perform destructive examination techniques on a range of irradiated materials including oxide fuels, stainless steel cladding, Zircaloy and ex-service graphite.

Using hot cell adapted metallographic cutting and grinding equipment, the team size reduce, mount and prepare highly active samples for a range of techniques including optical microscopy, electron microscopy, hydrogen analysis via hot vacuum extraction, thermal expansivity and diffusivity, and hardness testing. The samples for microscopy examination are transferred to a designated lower-active cave which contains a range of equipment including:

  • Two light optical microscopes
  • SEM
  • Henry Royce Institute funded optical microscope with three Raman lasers and a microhardness HV tester (Vickers) (to be installed spring 2020)
  • Henry Royce Institute funded Deben in-situ 5kN tensile compression and horizontal bending stage (to be installed spring 2020)

Routine customer work involves using the optical microscope to perform dimensional measurements on ex-service components, together with documenting observations and capturing micrographs. This information is used to determine in-service operating temperatures and to deduce potential failure mechanisms, which feeds into supporting our customers safety cases. Other niche projects have involved making electrochemistry samples and ‘matchstick’ fuel samples for SEM-EDX analysis, together with providing information for long-term pond storage and EU projects.

The team also has a non-active metallographic laboratory at NNL’s Workington facility, which is used to develop and support active operations. This contains non-active replica equipment including two cutters, grinding and polishing machines and a preparation optical microscope. The lab also contains new equipment which is being non-actively commissioned before installation to the hot cell. Currently (early 2020) this includes a microhardness tester and a laser flash analyser, which is used to conduct thermal diffusivity measurements.

The multiple capabilities of the equipment and the experience of the metallography team allows larger active samples to be size reduced and prepared. These samples can then be either examined at Central or Windscale Laboratory, or exported to an academic facility. The microscopes complement the Deben mechanical testing stage, enabling complete characterisation of highly-active materials from visual identification of features of interest, to determining chemical compositions and mechanical properties.

Customers: EDF Energy, Rolls Royce, Sellafield Ltd, MoD, Wood, NDA, RWM, BEIS and EU programmes.

Collaborations: The metallography PIE team work closely with Universities, government organisations, IAEA, EU projects and internally within NNL. Through the Industrial Training Programme NNL provides real industrial problems to third year students from Sheffield University, who’s project is investigating the issue and proposing a solution. The team is involved with helping the students understand the constraints of the nuclear industry and guide their research. In recent years the team has also hosted several university placement students who directly contribute to customer projects.