BS IEC 62397:2007 details the specifications for Resistance Temperature Detectors (RTDs) that are appropriate for use in nuclear power plants (NPPs). The requirements encompass the design, materials, manufacturing process, testing, calibration, procurement, and inspection of RTDs. In nuclear applications, both “direct-immersion” and “thermowell-mounted” RTDs are widely employed; nonetheless, this standard does not preclude any other RTD design that may be necessary for specific specialized applications across different reactor types.
RTDs can be manufactured with various internal configurations, which are determined by the manufacturing process, qualifications, and intended applications. For RTDs intended for use within an NPP, the design and construction of the RTD must take into account the environmental conditions it will encounter during normal operation and under design basis accident scenarios, as well as the qualification tests stipulated by the user. A common practice is to use a flexible mineral-insulated (MI) cable between the RTD and the connector; however, the user may opt for any other construction. An alternative design might involve a rigid outer sheath over the MI cable, which is welded to the connector at both ends.
The scope of this standard does not include the design, material selection, and construction of the thermowell, the guide tube, the extension cable, or the temperature transmitter or bridge that may be connected to the RTD.
