This document describes the requirements for resistance temperature detectors (RTDs) suitable for applications in I&C systems important to safety of nuclear power plants. The requirements of RTDs include design, materials, manufacturing, testing, calibration, procurement, and inspection. RTDs used for safety applications in Nuclear Power Plants can be categorized into direct-immersed and thermowell-mounted RTDs. Furthermore, there are RTDs with specific design which cannot be assigned to the categories mentioned above. However, they are also covered by the requirements stated in this document. This document does not cover the design, material selection, and construction of the thermowell, the guide tube, the extension cable, and the temperature transmitter or resistance bridge which may be associated with the RTD.