This part of IEC 60951 provides general guidance on the design principles and performance criteria for equipment to measure radiation and fluid (gaseous effluents or liquids) radioactivity levels at nuclear power plants during and after an accident. This standard is limited to equipment for continuous monitoring of radioactivity in accident and post-accident conditions. The object of this standard is to lay down mandatory general requirements and give examples of acceptable methods for equipment for continuous monitoring of radioactivity within the plant during and after accident conditions in nuclear power plants using light water reactors. It specifies, for the equipment described above, the general characteristics, general test procedures, radiation, electrical, safety and environmental characteristics and the identification and certification of the equipment. If this equipment is part of a centralized system for continuous radiation monitoring in a nuclear facility, there may be additional requirements from other standards related to this system. Sample extraction and laboratory analysis, which are essential to a complete programme of effluent monitoring, are not within the scope of this standard.