On-line boron concentration monitoring device

The invention belongs to on-line monitoring devices for nuclear power plants, and provides a device for continuously monitoring the boron concentration on line in a circuit of a pressurized water reactor of a power station. The device comprises a neutron source, an assembly for mounting the neutron source, a neutron detector, and a shield arranged around the neutron source, wherein the neutron source is arranged on a circuit pipeline; the neutron detector is arranged under the circuit pipeline; a calibrated orifice of which the pipe diameter is the same as that of the neutron detector is formed above the neutron source; the shield arranged around the neutron source comprises an inner polyethylene slowing-down layer and an outer boron-doping polyethylene layer. The device is high in integration level, compact in structure, convenient to detach, capable of self-calibration, and high in measuring response speed, makes up for use deficiencies of a conventional off-line boron concentration monitoring device and a conventional on-line boron concentration monitoring device, prolongs the response time of the boron concentration monitoring device, simplifies the periodic calibration process, meanwhile, reduces the size, and improves the signal to noise ratio of a signal processing device.