Posted to News on 31st Mar 2025, 15:00
Robust inductive sensors trusted on crane within nuclear power plant reactor
Contrinex's uniquely robust inductive sensors are trusted in a wide variety of demanding or critical applications, with an extreme example being their use in a nuclear power plant. The sensor is used to verify that a grab on a specialised crane is closed when lifting.
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The pressurised-water reactor utilises fuel rods containing radioactive material, which are kept immersed in water. During operation, bundles of fuel rods are moved using a crane fitted with a custom-built grab. Contrinex's stainless-steel '700 Series' inductive sensors are fitted within the grab to detect and verify the presence of the bundle of fuel rods in the crane's grab before lifting.
Fuel bundles containing 200 to 300 nuclear fuel rods are immersed in water, forming the core of a pressurised-water nuclear power station. The water acts as a coolant and transfers heat energy which can exceed 300degC to turbines which generate electricity.
Periodically, individual bundles are removed when their fuel rods are spent. A customised crane positions a purpose-built grab directly over the bundle to be moved. The grab is lowered into the water and grips the top of the bundle, which is then lifted out of the core.
Contrinex '700 Series' inductive sensors, which are frequently used in hazardous and hostile environments, are used to detect the presence of the bundle in the grab, initiate closure, and sense the position of the grab, allowing lifting only after they have verified complete closure of the grab. The sensor's reputation for reliability is important because the crane is only maintained at 18- to 24-month intervals and consequently, exceptional reliability is essential.
Contrinex's Extreme '700 Series' inductive sensors excel in extremely demanding environments and are therefore ideal for this application. The sensor's body is constructed from a single piece of V2A/AISI 303 stainless steel to form the front face and cylinder. The IP68- and IP69K-rated sensors are pressure-resistant to 80 bar (1160 psi) and are corrosion-resistant.
A 6mm sensing distance is provided by the small M12-diameter, 60mm long, sensors that are embeddable and so are mounted directly in the metal structure of the grab. They are lightweight and exceptionally reliable which helps ensure the correct operation of the grab. Their vacuum-encapsulated electronics ensure excellent resistance to shock and vibration, and therefore no additional electrical or mechanical protection was required in the installation.
The sensors are configured with an industry-standard PNP normally-closed interface, and connection to the customer's control system is via a flexible PUR-sheathed cable. The M12 connector allows easy disconnection and removal when required. These sensors also offer the IO-Link digital communication protocol.
Because the crane and therefore the sensors can only be accessed at 18- to 24-month intervals during scheduled maintenance, exceptional reliability is required. Therefore, the design of the system also includes double redundancy to allow for damage or premature failure. Four sensors are fitted to each grab, with two identical sensors operating at each sensing point. In the unlikely event that a failure occurs, normal operation is unaffected.
