This publication aims to provide guidelines for the assessment of the safety of nuclear facilities other than NPPs in relation to external events through the application of simplified methods and procedures for their siting and design. The approach adopted is both simplified and conservative compared with that used for power reactors. It seeks to provide a rational balance for a suitable combination of sustainable effort in site investigations and refinement in design procedures, compatible with the assigned safety objectives, graded from those of NPPs. This publication is the successor to IAEA TECDOC 348 (1985), which focused on the seismic design of nuclear facilities with limited radioactive inventory. After some 17 years, new operational data have become available, sophisticated design methodologies are now more easily obtainable, and experts felt that the trade-off between sustainable investment in the facilities and design conservatism had to be redefined. The publication has been mainly developed for engineers, constructors and utilities, but it can be effectively applied also by regulatory bodies as a quick and conservative review tool.