As a follow-up to the 2010 NEA report Nuclear Fuel Behaviour under Reactivity-initiated Accident (RIA) Conditions: State-of-the-art Report 2010, this report presents the state-of-the-art knowledge on nuclear fuel behaviour under reactivity initiated accident (RIA) conditions for light-water reactors (LWRs) and conventional fuels. It gives an overview of scenarios for RIAs in major types of reactors and a description of key phenomena in fuel rod behaviour under RIAs, including burn-up effects. It provides an overview of tests and experiments that have been conducted to study RIAs, a summary of results from experimental programs with integral RIA simulation tests, and a description of computer programs used for analyses of RIAs. As regards fuel safety analyses, it discusses the transferability of test results to LWR RIA conditions and state-of-the-art methods for analysing postulated scenarios for RIAs in LWRs. It also gives a review of the regulatory acceptance criteria for RIAs applied in twelve NEA member countries. Finally, it provides recommendations as to the research work needed to fill the remaining knowledge gaps for RIA analyses.