This proceedings publication presents the essential content of the 2015 IAEA international conference on the operational safety of nuclear power plants. Although conferences on this topic are conducted regularly, this was the first one after the earthquake in 2011 that caused the accident at the Fukushima-Daiichi nuclear power plant. The conference brought together a broad range of participants including nuclear utilities, regulators, governments and academia. The topics covered operational safety, culture for safety, effective use of operating experience and the safety of long term operations, amongst others. A fresh perspective was added by representatives of other industries that deal with significant potential hazards. This publication, available exclusively in digital format, provides the reader with the opening and closing addresses, summaries of all sessions and the majority of the papers and posters accepted for the conference.