The purpose of this procurement is to establish a framework agreement with a number of pre-qualified, specialist corrosion testing providers to deliver corrosion testing services for the UKFE STEP programme over the next two years. The framework will enable efficient and compliant call-off contracts for testing of high-temperature coolants, carrier gases, and breeder materials against STEP coolant-facing alloys and candidate tritium breeding materials as requirements arise. The framework is intended to streamline procurement and contract management, reduce the need for repeated tender exercises, improve consistency in quality and supplier performance, and enable faster delivery of future testing requirements through simplified call-off procedures. The procurement also aims to establish long-term working relationships with expert testing organisations, promote innovation and market engagement, support a broad specialist supplier base (including SMEs), and ensure compliance with the Procurement Act 2023 through transparent, competitive, and value-for-money procurement. Framework appointments are intended only for organisations that can undertake the testing directly. The testing will generate mechanistic understanding of corrosion interactions between high-temperature coolants (including light and heavy water, supercritical CO2 and helium), carrier gases (helium), STEP coolant-facing alloys, and candidate tritium breeding materials (including lithium ceramics and liquid metals), to quantify corrosion effects, identify mitigation strategies, and support the extension of component service life. – Lot nr.: Lot 1 Light (H2O) and heavy (D2O) water exposure. This lot covers the provision of corrosion testing services to assess the performance and compatibility of STEP candidate materials when exposed to high-temperature aqueous environments representative of future fusion reactor operating conditions. Testing will focus on austenitic stainless steels, tungsten, copper-based alloys, and other candidate materials supplied by UKFE. The objective is to quantify corrosion behaviour, establish baseline performance data using unirradiated materials, and develop a mechanistic understanding of corrosion processes to support material selection, coolant chemistry development, and component lifetime assessment. Suppliers are encouraged to propose capabilities for testing under synergistic irradiation environments where available. The scope includes exposure testing in recirculating high-temperature, high-pressure water environments, monitoring of relevant environmental and corrosion parameters, post-test material characterisation, and the generation of data including corrosion rates, material loss, crack initiation and growth behaviour, oxide characterisation, and material/coolant compatibility. Testing shall be undertaken using recognised industry standards where available, or mutually agreed methodologies where standards do not exist. Suppliers should be capable of undertaking specimen testing, advanced post-exposure characterisation, data analysis, and reporting. Final deliverables will include raw and analysed test data, technical reports, microstructural characterisation results, and the return of all tested and untested materials to UKFE. A non-exhaustive list of anticipated testing requirements is provided in Appendix H – Test Matrix, and suppliers may offer all or part of the required services, as well as complementary capabilities. Duration contract start date : 02/11/2026 12:00:00 AM Duration contract end date : 02/11/2028 11:59:59 PM Criteria definitions: Price: 10 (Commercial) Quality: 80 (Technical) Quality: 10 (Social Value) – Lot nr.: Lot 2 CO2, supercritical CO2 exposures & Helium – applicable to lot 2 This lot is for the provision of specialist materials testing services to assess the performance and degradation of candidate fusion reactor materials under representative STEP operating environments. The work will evaluate uncoated and coated structural alloys, including austenitic stainless steels, ferritic steels and copper-based alloys, when exposed to high-temperature CO2, supercritical CO2 and helium environments, including helium in contact with lithium-rich breeder materials. The supplier will undertake controlled exposure testing to quantify degradation mechanisms such as oxidation, carburisation, corrosion, creep-corrosion and crack growth, and provide mechanistic understanding of these processes together with potential mitigation strategies. Testing will primarily be performed on unirradiated materials to generate baseline performance data, although capability for irradiation-assisted testing is desirable. The scope includes specimen manufacture (where required), high-temperature exposure testing in controlled gas environments, online environmental monitoring, post-test materials characterisation, microstructural and compositional analysis, measurement of corrosion and mass change, and comprehensive reporting of raw and analysed data. For helium testing, additional assessment of interactions between structural materials, protective coatings and lithium-rich breeder materials is required, including appropriate handling of air-sensitive materials. All testing shall be conducted to recognised industry standards (e.g. ASTM where applicable) or agreed alternative methods where no standards exist, with all tested and untested materials returned to UKFE on completion of the contract. Duration contract start date : 02/11/2026 12:00:00 AM Duration contract end date : 02/11/2028 11:59:59 PM Criteria definitions: Price: 10 (Commercial) Quality: 80 (Technical) Quality: 10 (Social Value) – Lot nr.: Lot 3 Liquid metals – applicable to lots 3 This lot is for the provision of specialist testing services to evaluate the compatibility and degradation of candidate fusion reactor materials in liquid metal environments representative of STEP operating conditions. The work will assess structural materials, including austenitic steels, ferritic steels, tungsten and SiC/SiC composites, for corrosion, dissolution, selective leaching, embrittlement and other degradation mechanisms that may affect component performance and lifetime. The scope includes the manufacture and characterisation of lithium-lead (LiPb) liquid metals of varying compositions, measurement of thermophysical properties, controlled impurity addition and analysis, and long-duration corrosion exposure testing under representative operating conditions. Testing will investigate the influence of liquid metal composition, impurities and operating environment on both the liquid metal and exposed materials to improve understanding of corrosion mechanisms and materials compatibility. Services include liquid metal manufacture and purity validation, thermophysical property assessment, static and dynamic corrosion testing, advanced post-exposure materials characterisation, analysis of corrosion products and impurity uptake, specimen manufacture where required, and comprehensive reporting of raw and analysed data. Testing will primarily be undertaken on unirradiated materials to generate baseline performance data, with capability for pre-irradiated materials and advanced exposure techniques considered advantageous. All testing shall be carried out in accordance with recognised industry standards (e.g. ASTM where applicable) or agreed alternative methods where standards do not exist. The contract also includes testing of coated materials, handling of reactive liquid metals under inert conditions, and the return of all supplied materials to UKFE upon completion of the work. Duration contract start date : 02/11/2026 12:00:00 AM Duration contract end date : 02/11/2026 11:59:59 PM Criteria definitions: Price: 10 (Commercial) Quality: 80 (Technical) Quality: 10 (Social Value)