Scientists from Perm National Research Polytechnic University have created and patented a thermometer capable of operating stably in the extreme conditions of a nuclear power plant without failure, monitoring the safe operation of a nuclear reactor.
The key element of a nuclear power plant is the reactor, where uranium nuclei are split, and a reliable thermal regime is critical for safety and efficiency. Existing thermometry systems have serious drawbacks: thermocouples fail quickly due to radiation, resistive sensors distort readings under electromagnetic interference, and fiber-optic technologies lose accuracy when the protective coating is damaged by prolonged heating, leading to accelerated equipment wear and frequent shutdowns for replacement.
To solve these problems, scientists at Perm Polytechnic University have developed a device that combines the advantages of fiber-optic systems with resistance to radiation and electromagnetic interference. The device has a measurement range 3-4 times wider than analogues, is durable, and provides accurate control in the reactor core for safe operation of the plant.
The new design of the sensitive element is based on an optical fiber, inside which there are microscopic gas cavities filled with oxygen under pressure, and a metal shell is used instead of the traditional organic protective and hardening coating. The combination of such cavities, each of which is about 3-6 μm in size, is a highly sensitive sensor that changes the optical properties of the reflected radiation under the influence of heat, which is registered by the measuring system.
If we consider the process in more detail, a "flashlight" is built into the thermometer design, which sends a beam of light through a thin glass fiber, at the end of which there are microscopic bubbles with gas, which are a temperature-sensitive element. Light, interacting with the bubbles, is reflected and passes through an "amplifier", a special magnifying glass, entering the measuring system. The computer analyzes changes in the properties of the light reflected from the bubbles due to heating of the sensitive element in the external environment, and converts them into temperature readings.
Depending on the selected high-temperature material of the protective and hardening coating — aluminum, copper, nickel, or their alloys — the thermometer can operate stably in the temperature range from minus 196 degrees Celsius up to plus 1000 degrees Celsius, while existing analogues can withstand no more than 400 degrees Celsius for a short time.
An important improvement was the introduction of an optical amplifier into the measuring circuit, which made it possible to use low-power light sources, completely eliminating the self-heating effect of the sensor.
Thus, the thermometer is not affected by electromagnetic interference, is resistant to radiation, has a 3-4 times wider measuring temperature range, and does not require frequent replacement. In addition, it can be used in metallurgy to control melts, in the chemical industry for aggressive environments, and in the energy sector to monitor equipment. The use of the development will reduce maintenance costs and increase the efficiency of energy facilities due to more accurate control of thermal regimes.
A patent has already been issued for the invention of Permian scientists, and the research itself was carried out as part of the strategic academic leadership program "Priority-2030".