Strategic Support Framework for Spent Fuel

The measurement and metrology services lot covers the adaption or development of measurement systems for application in: • A heavily shielded, irradiated fuel examination facility, where measurements are undertaken directly on irradiated materials out of their storage context. Adaption may require deployment into high radiation environments or may require adaptation to be able to deploy them across a thick concrete wall into a high radiation environment with limited access and limited ability to manipulate items. • Pond storage environments: where irradiated fuel is stored in fixed geometries underwater, with restricted access • Dry storage environments, where fuel is contained within sealed containment systems. Monitoring may be focussed on the integrity of the containment system or conditions inside the container. Additional information: Full details can be found in Appendix D Procurement Specification.

The principal topic areas of interest in relation to this topic area are listed below and support with experimental works, technique demonstration and modelling are of interest: • Environmentally assisted stress corrosion cracking of irradiated high Ni Austenitic stainless steel (AGR cladding) in pond water • Environmentally assisted stress corrosion cracking of austenitic stainless steels in air, associated with long term fuel and nuclear material dry storage canisters • Corrosion of fuel materials in pond water, disposal contexts and nominally dry gasses. Whilst the main focus is on uranium oxide and U:Pu mixed oxide fuels, there is also interest in work on other fuels, as note above • Corrosion of fuel cladding materials, as detailed above, in pond water, disposal contexts and nominally dry gasses. • Oxidation of fuel and cladding materials at low temperatures (e.g. below about 200°C) over very long timescales. Additional information: Full details can be found in Appendix D Procurement Specification

The focus on this area is to undertake non-active work on simulant materials or undertake modelling of aspects of spent fuels that affect their behaviour in long term storage, although consideration of preparation for disposal is also relevant. Areas of particular interest are: • Migration of water into failed fuel during pond storage. This may include fuel in a range of conditions from largely intact fuel pins, to short sections of fuel, fuel fragments and fuel corrosion products. • Migration of water out of failed fuel in storage or drying at a range of potential pressures and temperatures • Radiolysis of /water vapour and hydrated compounds associated with failed fuel and corrosion products in wet and nominally dry conditions r • Evolution of fuel and fuel corrosion products during storage, including dry, damp and aqueous environments, and during drying under vacuum or elevated temperatures • Interaction and behaviour of radionuclides released as a result of fuel/cladding corrosion with the storage environment • Materials engineering associated with hydrogen management, in particular to control pressurisation or explosion risk. • Options for the stabilisation and treatment of severely damaged and corroded fuels. Support is sought in relation to undertaking experimental work and modelling. Additional information: Full details can be found in Appendix D Procurement Specification

Access to irradiation facilities is required in relation to three principal requirements: • Understanding the effects of irradiation on materials, particularly in relation to radiolysis effects. Current areas of work are related to high pH aqueous conditions, however irradiation of low humidity air and conditions relevant to disposal are also of interest. • Neutron imaging techniques for the detection and mapping of hydrogen in fuel storage systems (in-situ) and for detection of water in irradiated fuels (ex-situ). • Beam line characterisation of the chemistry of nuclear materials undergoing corrosion or speciation in environments of interest (principally pond storage and disposal) using spectroscopy techniques e.g. XAFS / XANES. Additional information: Full details can be found in Appendix D Procurement Specification.