Presents the safety objective, and detailed requirements for the fulfilment of safety function for the various types of emergency power systems. AC, DC, non-interruptible AC, standby diesel generators and non-electric systems such as steam turbines for individual pumps and instrument air, and the necessary distribution systems are dealt with.

Presents the questions which must be posed by the safety assessor when reviewing the safety of an emergency power system in the design of a nuclear power plant. An extensive reference list of relevant international and national technical standards provides further guidance on acceptable design solutions.

This publication contains guidance and recommendations on the requirements for ensuring the reliability of all types of emergency powers systems (EPSs) for both new and operating nuclear power plants. It is intended for the use of those involved in the design, operation, assessment and licensing of EPSs, including designers, safety assessors, regulators and operators. It revises the previous safety guide (Safety standards series no. 50-SG-D7 (Rev. 1) (ISBN 9201232918) issued in 1991.

This Safety Guide was prepared under the IAEA safety standards programme for nuclear power plants (NPPs). The basic requirements for the design of safety systems for NPPs are provided in Safety Standards Series No. NS-R-1: Safety of NPPs: Design. The Safety Guide describes how the revised basic requirements should be met for the design of emergency power supply systems for NPPs. This publication is a revision of Safety Series No. 50-SG-D7, Emergency Power Systems at NPPs. It takes account of developments in the design of emergency power supply systems in NPPs since 1991 and includes recommendat.