IEC 61504:2017 supplements IEC 61559-1 and includes radiation monitoring functions important to safety that are outside the scope of IEC 61559-1. It applies to centralized systems having a direct role in the achievement or maintenance of radiation protection in nuclear facilities. These systems perform functions such as: - radiation protection of plant discharge; interlock of control functions to prevent or to mitigate accidental release of radioactive material; - radiation and environmental monitoring functions to support monitoring of and response to accidents; - provide information to process control or safety systems for use in control or interlock functions. This new edition includes the following significant technical changes with respect to the previous edition: - it supplements IEC 61559-1 and integrates IEC 61559-2; - it describes integration of functions including equipment covered by other IEC standards.