To ensure the reliable operation of key equipment in nuclear power plants, temperature monitoring during operation is indispensable, so that potential safety hazards can be detected in time. Fiber optic temperature measurement is a new technology developed in recent years and has gradually shown some outstanding characteristics. The distributed fiber optic temperature measurement system is based on the backward Raman scattering temperature effect of optical fiber and the optical time-domain reflectometry theory. It uses optical fiber as the temperature information sensing medium and transmission medium, combined with high-power pulsed light source and high-speed signal acquisition and processing technology, to obtain the temperature value at each point where the fiber is located. It features long distance, distribution, integration and high precision. Meanwhile, because optical fiber has obvious characteristics such as anti-electromagnetic interference, corrosion resistance, moisture resistance and salt resistance, the system fully matches the requirements of nuclear power plant equipment and can be used for temperature measurement and fire alarm systems of various facilities in the plant, especially for applications requiring large-scale, multi-point accurate measurement — such as heating positions caused by high-voltage transmission of cables or poor contact of electrical equipment, cable compartments, cable channels, large transformers, boilers and pipelines.

I. Application cases of fiber optic temperature measurement systems in nuclear power plants:

(1) Outdoor transformer temperature sensing area. The traditional temperature measurement method is to fix the temperature-sensing cable on the transformer fire water pipe, or suspend the temperature-sensing cable around the transformer with steel wire rope or brackets. In these detection installation methods, there is a certain distance between the detector and the transformer body. In order to minimize the influence of air circulation and heat transfer time on the accuracy of temperature detection, and considering that the transformer is a high-voltage current-carrying body with certain restrictions on halogen-containing materials and metals, a heat-resistant silicone optical cable was designed for transformer body temperature measurement. It is attached to the outer surface of the transformer body with plastic strips, maximizing the body temperature measurement accuracy without affecting the aesthetics and daily maintenance of the transformer.

(2) Cable bridges, cable corridors, cable trenches, GIL (gas-insulated pipeline) busbars, copper busbars and other electrically concentrated sites. The electromagnetic interference generated by these concentrated sites and the humid environment of underground corridors can change the physical, mechanical and electrical properties of electronic products, accelerating equipment corrosion and reducing equipment insulation strength. When the distributed fiber optic temperature measurement system is applied to such sites, it can give full play to its long-distance, corrosion-resistant and anti-interference characteristics. It can be arranged on the top of the corridor and the surface of the cable bridge to detect the temperature of corridor and bridge cables in real time, provide early warning of fire alarm risks (prevention before "burning"), and link with other detection methods to fire-fighting equipment.