Nuclear safety and security are absolute priorities for the EU. As the European Commission’s in-house science service, the Joint Research Centre (JRC) supports the Commission in fulfilling the obligations originally set up by the Euratom (European Atomic Energy Community) Treaty in the areas of nuclear research, training and education, and radiation protection. The JRC’s nuclear research activities are defined in a Council Regulation on the research and training programme of the European Atomic Energy Community (2014-18), which complements the EU framework programme for research and innovation, Horizon 2020. The activities also fulfil the legal obligations under the Euratom Treaty (chapter III arts 36 and 39), and under several Euratom recommendations, decisions and directives. The March 2011 Council as well as nuclear summits conclusions also emphasise the need to give priority to the highest standards for nuclear safety and security in the Union and internationally. There are currently around 130 nuclear reactors in operation in 14 EU countries, which produce approximately one third of the European Union’s electricity. The choice to use nuclear power or not in the energy mix of each of the 28 EU Member States is a national decision and currently the situation differs significantly among them. Some Member States have nuclear phase-out policies, whilst some others are opting for long-term operation and lifetime extension of their nuclear plants. This report provides a comprehensive overview of the work of the JRC, the European Commission’s in-house science service in the domain of nuclear safety and security. This research area encompasses the safety of nuclear reactors and the nuclear fuel itself, the safe operation of nuclear energy systems, as well as nuclear safeguards, non-proliferation and the fight against illicit activities involving nuclear and radiological material. The description of the JRC’s work is divided into five chapters, each chapter describing JRC research and relevant scientific outputs in the area, linked to their policy background and context. In addition, lists of facilities, partners and references as well as links to useful tools and websites are provided.