Within the framework of large R&D studies performed for the future sodium-cooled reactor prototype called ASTRID, in-service inspection and repair (ISI&R) has been identified as a major issue to be taken into account in order to improve the reactor’s safety, to consolidate its availability and to protect its related investment. Following on from the pre-conceptual design phase (2008-2012), the conceptual phase (2013-2015) is now focusing on improving the ISI&R tool for structures immersed in sodium at about 200°C in the ASTRID reactor. This work is based on a set of consolidated specifications and a qualification process involving increasingly more realistic experiments and simulations performed with the CIVA code. ISI&R items are being developed and qualified as part of a multi-year program which mainly deals with the reactor block structures, the primary components and circuit, and the power conversion system (PCS). This program is ensuring the strong ties needed between the reactor designers and inspection specialists since the aim is to optimize inspectability and repairability. This has already induced specific rules for design in order to shorten and facilitate ISI&R operations. These new rules have been merged into the RCC-MRx rules. Current R&D deals with the following ISI&R items: • Under-sodium non-destructive examination (NDE) of welded joints on the ASTRID supporting core structure (so called strongback): sodium testing and simulation are being performed • NDE of welded joints on the ASTRID strongback supporting skirt, from outside the primary sodium (through the main vessel wall): water testing and simulation are being performed • Under-sodium NDE of welded joints on the ASTRID above-core structure: water testing and simulation are being performed • Under-sodium telemetry and vision of immersed structures and components forming the ASTRID primary vessel: improved techniques of scanning are being studied • Primary circuit cover-gas telemetry of structures and components forming the ASTRID primary vessel • Methods for in-situ repair: a laser technique has been selected • Associated in-sodium robotics: a sodium-proof material and technology is being developed and tested This paper provides the main testing and simulation results for telemetry, vision and NDE applications. R&D for inspection and repair of SFRs faces challenging requirements and is progressing towards available technological solutions, associated with demonstrated performance levels: the basic inspection techniques are expected to reach level 6 of ‘technological readiness’ by the end of conceptual phase. The integrated readiness level’ is also discussed in this paper with respect to access within the reactor block, fluids, positioning and maintenance aspects.