IEC 60965:2016 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. This new edition includes the following significant technical changes with respect to the previous edition: - requirements associated with regular testing of the supplementary control room (SCR); - requirements to assess the time available during which the reactor will be safe but unattended, in order to move from the main control room (MCR) to the SCR and for the SCR to become operational; - taking into account new requirements laid down by the IAEA.