Fuels, Reactors and Reprocessing

NNL’s Materials and Corrosion group contains a number of uniquely experienced professional radiochemists, metallurgists, physicists, materials and corrosion scientists, whose expertise spans a wide range of areas in materials, reactor/plant chemistry and corrosion, and has a long history of successful delivery of work programmes to an exceptional standard. The group supports strategic programmes for both the civil and naval fleets, as well as provide advice on strategic UK issues.

The Materials and Corrosion have provided support on both chemistry and materials issues to the ONR for the Generic Design Assessment process for the approval of new reactor designs. For current reactors, both civil and naval, the team provides support to our customers in areas such as reactor chemistry (graphite and coolant), plant chemistry (storage ponds and associated plant) & the effect of irradiation on materials (including embrittlement of ferritic steels, radiolytic oxidation of graphite and oxidation of Zr alloys). Much of the work directly supports plant operation and lifetime extension. The group also provides focused solutions to emerging materials degradation problems facing the Sellafield site using state-of-the-art facilities and equipment.

Part of the group focus is to develop and maintain knowledge databases on specific technical topics such as embrittlement of reactor pressure vessel, iodine chemistry and dry storage of spent fuel. The team has access to unique facilities and expertise both within our organisations and within NNL’s wider network (which includes other national labs, academia and other EU organisations) that enables us to:

• Maintain capability in key niche technical areas to assist the generation nuclear section in meeting its end of life targets.
• Continued operation in the naval propulsion programme and to support decommissioning ambitions for existing nuclear plants.
• Provide lessons learned experience from previous PLEX operations, as well as defueling and decommissioning from Magnox fleet and the Sellafield plant.

Facilities: The group operate in low and high active operational areas (fumehoods at Central and high active caves at Windscale) to undertake a ‘forensic’ type investigation & analysis of a wide variety of fuel types, irradiated components and radioactive contaminated plant. A wide variety of investigative techniques are used and the team of technicians are both scientifically qualified and expert at remote handling. The work undertaken in the labs consists of routine monitoring of nuclear fuel and reactor components, extended performance trials of ‘standard fuel’, experiments involving non-standard fuel or non-standard operating conditions and trouble-shooting unforeseen problems, including failures.

A variety of destructive and non-destructive techniques are available: Mensuration/ metrology, X-radiography, Gamma scanning, Eddy-current and ultrasonic flaw detection, Leak testing, Fission gas pressure, volume & sampling, Internal stress, Deposit/oxide thickness & morphology, Youngs Modulus, Thermal expansion & diffusivity, Mechanical testing – tensile, compression, 3-point bend, Impact testing, Fracture toughness, Gas-diffusivity, Open pore volume, Isotope assay, Gas mass spectroscopy, Fluorescence spectroscopy, Corrosion rate, Stress rupture, Density, Weight loss, Differential oxidation, Hot-vacuum extraction, Optical microscopy, Electron microscopy & various associated analyses, and the more esoteric analysis techniques.

Collaborations: The Materials and Corrosion group can draw from expertise held in other areas of the business, as well as a number of external resources. Members of the group hold visiting professor status, supervise PhD’s and/or have access to experimental facilities at universities in Oxford, Bristol, Manchester, London, Birmingham, Liverpool, Glasgow, Leeds, Lancashire, Southampton and Swansea, and the international facilities that NNL regularly access include the Diamond Light Source (Harwell, UK) and the European Synchrotron Radiation Facility (Grenoble, France).