This International Standard establishes requirements for the Supplementary Control Room provided to enable the operating staff of nuclear power plants to shut down the reactor, where previously operating, and maintain the plant in a safe shut-down state in the event that control of the safety functions can no longer be exercised from the Main Control Room, due to unavailability of the Main Control Room or its facilities. The design has to ensure that the Supplementary Control Room is protected against the hazards, including any localised extreme hazards, leading to the unavailability of the Main Control Room. The standard also establishes requirements for the selection of functions, the design and organisation of the human-machine interface, and the procedures which shall be used systematically to verify and validate the functional design of the supplementary control room. It is assumed that supplementary control room provided for shutdown operations from outside the main control room would be unattended during normal plant conditions other than for periodic testing. The requirements reflect the application of human engineering principles as they apply to the human-machine interface during such periodic testing and during abnormal plant conditions. This standard does not cover special emergency response facilities (e.g. a technical support centre) or facilities provided for radioactive waste handling. Detailed equipment design is also outside the scope of the standard. This standard follows the principles of IAEA Specific Safety Requirements SSR-2/1 and IAEA Safety GuideNS-G-1.3. The purpose of this standard is to provide functional design requirements to be used in the design of the supplementary control room of a nuclear power plant to meet safety requirements. This standard is intended for application to a supplementary control room whose conceptual design is initiated after the publication of this standard. If it is desired to apply it to existing plants or designs, special care must be taken to ensure a consistent design basis. This relates, for example, to factors such as the consistency between the supplementary control room and the main control room, the ergonomic approach, the automation level and the information technology, and the extent of modifications to be implemented in I&C systems.