Monitoring of nuclear power plants

A specialized system for measuring temperature, temperature gradients, and strain in containments — the protective reactor enclosures of nuclear power plants. An advanced monitoring system for the protection of critical infrastructure, providing long-term measurement accuracy and repeatability. Sensors based on FBG (Fiber Bragg Grating) technology, together with state-of-the-art evaluation electronics, ensure the system’s reliability and long service life.

A nuclear reactor is a highly complex technological facility whose safe operation is ensured by a wide range of protection systems, operational measurements, and emergency safety circuits. The most important protective element of a nuclear power plant is the reinforced concrete containment structure — the containment building — which is designed to prevent the release and spread of radionuclides and ionizing radiation into the environment in the event of an accident, including reactor leakage. In the event of leakage in the reactor cooling circuits, hot coolant could escape and create overpressure that the containment structure must withstand. The containment is therefore a critically important component of a nuclear power plant, and its service life essentially determines the operational lifetime of the entire reactor. For this reason, it is necessary to continuously and very precisely measure the response of structural deformations under various reactor operating conditions and evaluate the condition of the containment. Information obtained from FBG sensor measurements makes it possible to predict the future condition of the structure and monitor the effects of the prestressing system. This helps prevent irreversible changes in the containment structure that could shorten its service life, thereby contributing to greater safety and economic efficiency of nuclear power plants.

Fiber-optic sensors offer several key advantages compared to electrical sensors. The primary benefit is the evaluation of an optical signal, which is inherently resistant to electromagnetic interference. Compared to conventional vibrating-wire strain gauges, which use electromagnetic transducers for detection, fiber-optic sensors provide higher reliability and, above all, longer service life. In a fiber-optic sensing system, not only the sensors themselves but also the entire transmission network is implemented using optical fibers and cables, which are non-conductive. Optical strain gauges are temperature-compensated, which also enables temperature measurement directly at the sensor installation point. The sensor system is most commonly implemented using a serial-parallel topology, and several hundred sensors can be connected to a single evaluation unit, depending on the measurement range. Thanks to optical signal transmission, the evaluation unit can be located several kilometers away from the monitored structure.