This IAEA TECDOC provides practical guidance for assessing and managing the hazards posed by volcanic tephra fallout at nuclear installations. Drawing on current practices from Member States, it outlines methodologies for hazard assessment, offers design considerations to protect safety-related structures, systems and components (SSCs), and identifies operational measures to mitigate potential impacts. Focussing on tephra fallout that may affect nuclear installations located at moderate to long distances from volcanoes, this publication supports Member States in enhancing the safety and resilience of nuclear installations exposed to volcanic tephra fallout hazards.