Device for measuring the drop time of control rods into the core of a nuclear reactor

Device for measuring the drop time of a control rod into the core of a nuclear reactor comprising:

• a vessel closed in its upper part by a closure head and containing the reactor core including fuel assemblies positioned in vertical adjacent arrangements and having vertical guide tubes for receiving neutron absorbers of a plurality of control rods, each control rod including a neutron absorber rod cluster;
• a drive shaft connected at one of its ends to the control rod cluster;
• a plurality of tubular enclosures placed vertically above the closure head of the vessel, each tubular enclosure having a mechanism for moving a control rod by means of its vertical drive shaft, in the axial vertical direction of the tubular enclosure and for releasing the drive shaft in order to ensure that it drops into the position of maximum insertion in the nuclear reactor core;
• at least one electrical measurement winding surrounding each tubular enclosure, substantially over its entire axial length and connected to a measurement cable for picking up a measurement signal at the terminals of the winding;
• the control rods being grouped together in subassemblies and each electrical winding for each of the rods of a subassembly being connected via a measurement cable to a cabinet of rod position instrumentation containing a plurality of control rod position instrumentation sensors;
• a real-time measurement-signal acquisition module;
• and
• means for processing the measurement signals being connected to the output of the acquisition module for measuring the drop time of the nuclear reactor control rods;
• wherein each cabinet of the rod position instrumentation includes, for each measurement cable connected at its input to the winding of a control rod, an interface box connected permanently to an output of the measurement cable and to an input of a transmission cable for continuously transmitting a measurement signal to the real time acquisition module without interruption of supply power to the winding.