This publication is part of the IAEA’s Emergency Preparedness and Response (EPR) series. It provides the basic information and criteria needed by a decision maker in order to protect the public during an emergency involving severe fuel damage in a light water reactor (LWR) or graphite moderated reactor (RBMK) core and/or spent fuel pool. This publication applies to reactors with power levels greater than 30 MW(e) (100 MW(th)) and to spent fuel pools that contain reactor fuel that needs to be actively cooled in order to prevent overheating and failure of the fuel. It takes account of the lessons learned from response to past emergencies, including the accident at TEPCO’s Fukushima Daiichi Nuclear Power Station in 2011, and from latest research, while ensuring consistency with IAEA Safety Standards Series No. GS-R-2.