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.

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.