This publication provides information and a framework for Member States to conduct realistic safety evaluation for research reactors in terms of external events. The publication provides information with examples on the use of a graded approach, based on the radiological hazard that a facility poses to the environment, public and workers, and takes into account the lessons from the Fukushima accident. This publication supports the development of site specific guidelines for the actual design and safety assessment, and should be used in conjunction with the relevant IAEA Safety Standards. It can also be used as training material for research reactor staff and for a self-assessment of the vulnerability of existing structures to external events.