The study was endorsed for publication by the OECD/NEA Nuclear Development Committee (NDC). Philippe Lebreton (France) provided significant input to Chapter 2 “The Effects of Nuclear Power at the Level of the Electricity System”. The section on the load following capabilities of nuclear plants “The Flexibility Potential of Nuclear Power Plants in the Short Run” is based on earlier work by Dr. Alexey Lokhov (OECD/NEA Nuclear Development Division). For Chapter 5 on “Regulatory Frameworks for the Internalisation of System Effects and the Adequate Remuneration of Flexibility Services” a first draft was prepared by Eduard Blanquet i Arago (OECD/NEA Nuclear Development Division).